CA1051553A - Omnidirectional optical scanner - Google Patents
Omnidirectional optical scannerInfo
- Publication number
- CA1051553A CA1051553A CA203,370A CA203370A CA1051553A CA 1051553 A CA1051553 A CA 1051553A CA 203370 A CA203370 A CA 203370A CA 1051553 A CA1051553 A CA 1051553A
- Authority
- CA
- Canada
- Prior art keywords
- frequency
- light beam
- scan
- oscillating
- scan window
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
- G06K7/00—Methods or arrangements for sensing record carriers, e.g. for reading patterns
- G06K7/10—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation
- G06K7/10544—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation by scanning of the records by radiation in the optical part of the electromagnetic spectrum
- G06K7/10821—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation by scanning of the records by radiation in the optical part of the electromagnetic spectrum further details of bar or optical code scanning devices
- G06K7/10861—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation by scanning of the records by radiation in the optical part of the electromagnetic spectrum further details of bar or optical code scanning devices sensing of data fields affixed to objects or articles, e.g. coded labels
- G06K7/10871—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation by scanning of the records by radiation in the optical part of the electromagnetic spectrum further details of bar or optical code scanning devices sensing of data fields affixed to objects or articles, e.g. coded labels randomly oriented data-fields, code-marks therefore, e.g. concentric circles-code
Abstract
ABSTRACT OF THE DISCLOSURE
An omnidirectional optical scanner scans bar coded labels passed relative to a rectangular scan window with a plurality of interlaced X's whereby the labels are completely scanned irrespective of their orientation. The interlaces X's are generated from a laser light source directed onto a first oscillating mirror for deflecting the light beam in a horizontal direction at a slow frequency. A
second oscillating mirror is positioned to further deflect the light beam in a vertical direction at a higher frequency. The horizontal and vertical frequencies are set at a particular ratio so that the X's overlap and the scan on the return passes midway between the legs of a previous scan. The horizontal and vertical amplitudes are controlled by horizontal and vertical photo detectors located adjacent the scan window which provide inputs to amplitude control circuits to assure an orthogonal pattern by keeping the crossing angle constant. The oscillating mirrors are phase and frequency locked by a precision digital system to assure phase lock stability and thereby prevent voids in the scan pattern. The scan window crops out the end portions of the scan pattern. Generally, the most linear parts of the scan pattern, but including the turn around portions of the scans within the scan window are used. However. in one embodiment, end mirrors fold the end portions of the scan pattern outside of the window into the scan window toward the center thereof to enhance the scanning of certain labels.
An omnidirectional optical scanner scans bar coded labels passed relative to a rectangular scan window with a plurality of interlaced X's whereby the labels are completely scanned irrespective of their orientation. The interlaces X's are generated from a laser light source directed onto a first oscillating mirror for deflecting the light beam in a horizontal direction at a slow frequency. A
second oscillating mirror is positioned to further deflect the light beam in a vertical direction at a higher frequency. The horizontal and vertical frequencies are set at a particular ratio so that the X's overlap and the scan on the return passes midway between the legs of a previous scan. The horizontal and vertical amplitudes are controlled by horizontal and vertical photo detectors located adjacent the scan window which provide inputs to amplitude control circuits to assure an orthogonal pattern by keeping the crossing angle constant. The oscillating mirrors are phase and frequency locked by a precision digital system to assure phase lock stability and thereby prevent voids in the scan pattern. The scan window crops out the end portions of the scan pattern. Generally, the most linear parts of the scan pattern, but including the turn around portions of the scans within the scan window are used. However. in one embodiment, end mirrors fold the end portions of the scan pattern outside of the window into the scan window toward the center thereof to enhance the scanning of certain labels.
Description
3L~5~L~ 3 1 Background of the Invention Field of the Invention This invention relates to optical scanning systems and more particularly to omnidirectional optical scanning systems.
The invention finds particular application for scanning randomly oriented bar coded labels, which for example, are attached to consumer items being checked out at a counter. The check out operator merely passes the item across the scan window insur~ng that the label is within the scan window as the item is being placed into a box or bag. Except for certain small items, little attention need be paid to the orientation of the items as they are moved across the scan window.
Description of the Prior Art Omnidirectional scanning systems such as in U.S. Patents 3,718,761 and 3,728,677 are not particularly suitable for scanning ; systems where the operator passes the items across the scan window ;
because they require a square scan wi`ndow rather than a narrow rectangular scan window. The square scan window for a given width requires a greater reach and is not as desirable from a human factors point of view as a norrow rectangular scan window. The narrow ~
rectangular scan windowi however, requires multiple X patterns to insure ` ~i that the coded label will be properly scanned. The multiple X patterns are produced in this invention by sine wave light patterns and have a subtle safety advantage .,' ;, ' ' ' , ~ ' .
. ~ ;
:
The invention finds particular application for scanning randomly oriented bar coded labels, which for example, are attached to consumer items being checked out at a counter. The check out operator merely passes the item across the scan window insur~ng that the label is within the scan window as the item is being placed into a box or bag. Except for certain small items, little attention need be paid to the orientation of the items as they are moved across the scan window.
Description of the Prior Art Omnidirectional scanning systems such as in U.S. Patents 3,718,761 and 3,728,677 are not particularly suitable for scanning ; systems where the operator passes the items across the scan window ;
because they require a square scan wi`ndow rather than a narrow rectangular scan window. The square scan window for a given width requires a greater reach and is not as desirable from a human factors point of view as a norrow rectangular scan window. The narrow ~
rectangular scan windowi however, requires multiple X patterns to insure ` ~i that the coded label will be properly scanned. The multiple X patterns are produced in this invention by sine wave light patterns and have a subtle safety advantage .,' ;, ' ' ' , ~ ' .
. ~ ;
:
- 2 -,~
~)5~ 3~
in that -the av~r~ge laser power entering a fixed 2 aperture (]aser power times aperture diameter divided
~)5~ 3~
in that -the av~r~ge laser power entering a fixed 2 aperture (]aser power times aperture diameter divided
3 by length of scan) is less. The sine wave light patterns
4 on the other hand introduced linearity problems which this invention solved.
6 The use of two oscillating mirrors to 7 produce sine wave light patterns is well known in the 8 prior art as evidenced by U. S. Patents 1,756,232; 1,951,666 9 and 3,437,393. However none of these patents teach phase control to produce an X pattern without degeneration which 11 would result in scan voids. Also, in applicants' 12 invention amplitude control is needed to maintain the 13 crossing angle of the scans constant. These latter mentioned 14 patents are not directed to omnidirectional scanners.
The omnidirectional scanner of applicants' invention is 16 useful for scanning bar coded labels which may pass 17 anywhere in the scan window. Thus the X scan pattern .i :
18 should be uniform. Ideally, the scan lines should 19 intersect at the longitudinal axis of the scan window and at 45 and 135. In practice, with fV = AH
21 fH
22 where f=frequency and A-amplitude the scan lines are 23 at 45 and 135 to the longitudinal or horizontal axis ~;
24 at the center of the scan window but are at 55 and 125 at the edges. This error in applicants' invention is 26 spread out or normalized by introducing a constant 27 or stretch factor of 1.05 whereby:
28 AH = 1O05 fv . It should bè recognized that the other , -- ~
~ 29 AV
;~ 30 stretch or compression factors may be used to increase ; 31 or decrease the intersec~ion angles as may be advantageous RO973-012 -3- ~
.
,:
' ...... . . .
;
L in a particular application. The scan lines then 2 intersect at 40 and 140 at the center and 50 and 130 3 at the edges so as to be centered about the ideal 4 intersections of 45~ and 135. ' ' In applicants' invention, the ratio of 6 the low (herizontal) and high (vertical) frequencies 7 is important so as to make the X's as linear in curvature 8 as possible to reduce the unused portion of the scan and 9 thereby reduce scan speed and to interlace the scans so the X's are at an optimum spacing for scanning a particular 11 bar code label.
12 The turn around portions (nonlinear) of the 13 Lissajous scan pattern may or may not be used in the scan ~' 14 window depending upon'the type of label being scanned. I~ is ' desirable to have horizontal scans for scanning short or 16 segmented labels. The turn around portions of the Lissajous 17 pattern, although not linear, are useful for forming ~ ' 18 horizontal scans. This eliminates scan gaps whi'ch can ~-~
19 occur in the scanning arrangements of patents 3,718,761 '`~
20 and 3,728,677. Further, in app:Licants' invention, by ' ' 21 folding the end portions of the Lissajous pattern which are 22 outside of the scan window into the scan window, ~;
: .
23 substantially vertical scans are formed at the central '~
24 portion of the scan window. These vertical scans are 25 helpful for scanning worst case label conditions. ~;` -26 In applicants' invention, it is critical 27 that the frequency and phase lock system be verv accurate.
28 The mirrors are oscillated at resonance and the Q is very ; 29 high. Thus, any appreciable shift in frequency renders the - 30 system uns~able. Applicants' preferred èmbodiment uses a . ;
.
, - ~.
`, ' ' ~ .
:: : . : : ~.: . .. , , . .:,.: , ,.
1 digital Erequerlcy and phase lock sys-tem. Most prior art 2 frequency and phase lock sys-tems requirs a continuous 3 frequency change until the desired pha.se lock is achieved.
4 In such systems even a small frequency shift requires a long correction time,because to achieve system stability 6 the change in frequency must be slow. Applicants' 7 arrangement permits a relatively large change in frequency 8 because it is made instantaneously rather than being 9 continuous. Further, stability is maintained by making the changes at a slow rate; i.e., a change in frequency 11 is made only once during a predetermined sample period , 12 which occurs less frequently than the period of the oseillating mirror being controlled.
14 Summary of the Invention The principal objects of applicants' `
16 invention are to provide an improved omnidirecitonal 17 scanning system which:
18 (a) is eapable of scanning bar coded 19 labels without regard to label orientation, (b) can be used with a narrow rectangular 21 sean window, 22 (e) has high stability and accuracy, 23 (d) is highly reliable and 24 (e) is relatively inexpensive. ,; , These objects are achieved by using ' 26 an intense, substantially non-divergent light souree 27 such as a laser and deflecting the light beam with two 28 oscillating mirrors, which are phase and frequency locked, ,~ ' 29 to a narrow reetangular sean window whieh masks out the nonlinear end portions of the scan. The two mirrors `
, R0973-012 -5- ~ ~
1 are oscillated at frequenc1es which cau.se the beam to 2 trace out a pattern of ove~lapping Xls. Amplitude 3 control is included to maintain ~he light beam at a 4 constant crossing angle. ~he frequency and phase lock maintains unifoxm spacing of the X's and prevents the 6 scan pattern from degenerating.
7 Brief Description of the Drawings 8 Fig. 1 is a perspective view illustrating -9 the omnidirectional scanning system of the invention;
1~ Fig. 2 is a schematic block circuit 11 diagram of the control circuit showing a preferred 12 embodiment of the frequency and phase lock system and -~
~ . , 13 including the amplitude control circuit; - ~ ~
14 Fig. 3 is a more general schematic ~ -block circuit diagram of the frequency and phase lock 16 system of Fig. 2;
17 Fig. 4 is a waveform diagram including 18 a series of waveforms to lllustrate phase correction;
. , , ' ' . .
19 Flg. 5 ls a waveform diagram lllustrating the high and low frequency pulses for one scanner cycle;
21 Fig. 6 is a partial perspec~ive view 22 illustrating an alternate embodiment of the invention; --: . ~
23 Fig. 7 is a developed plan view illustrating , 24 the scan pattern for the alternate embodiment shown in Fig.
6;
26 Fig. 8 is a diagram showing a typical 27 label; and, 28 Fig. 9 is a perspective view illustrating 29 the invention incorpoxated in a housin~ at a check out ~ .
counter.
,''' :~
,.
.:- .: -. , :: : : .
. ~ :: : - . , .
,S~3 Descr ~
2 With re~erence to the drawings and 3 particularly to Fig. 1, the invention is illustrated 4 by way of example as including a laser light source 10 which provides an intense narrow beam of light schematically illustrated by line 11. This beam of 7 light is directed onto a beam expander 15 which includes 8 lens 16 for expanding the laser beam and focusing lens 9 17 for focusing the expanded beam and directing the beam onto mirror 21 of the horizontal torsional ~eflector 11 20.
12 The beam i5 reflected from mirror 21 to 13 mirror 26 of vertical torsional deflector 25. The terms 14 horizontal and vertical are arbitrary and could be interchanged without affecting the scope of the invention.
16 However, one of the torsional deflectors, in this example, 17 horizontal deflector 20 is operated at a lower frequency I8 than the operation of vertical deflector 25. The 19 horizontal deflector 20 and vertical deflector 25 are ;
operated at resonance with a predetermined frequency 21 ratio whereby the beam of light traces out a pattern of 22 interlaced X's 30 in scan window 35.
23 The beam from laser 10 is expanded and `
24 then focused so as to obtain a small focused spot near the large focal length of the focusing lens 170 The 26 maximum deflection angle of the torsional deflectors 27 20 and 25 dictates the focal length. However, the large 28 focal length increases the depth of field.
29 Horizontal deflector 20 moves the beam so as to scan the length of window 35 and vertical deflector 31 25 causes the beam to scan the width of window 35. The -RO973-012 -7- `
-, ~l~5~Si~;3 - combination of these orthogonal deflections at pred~termined 2 fixed frequency ~nd amplitude ratios produces the 3 pattern of interlaced X's at scan window 35.
4 Scan window 35 is located at the top of ;~
an enclosure 50, Fig. 9, for housing the previously 6 described elements. Scan window 35 is a narrow rectangular 7 aperture formed in the housing and covered by glass 8 or other suitable transparent material. ~ , 9 In Fig. 9 an article 70 bearing a bar coded '~
label 71 is transported by conveyor belt 51 to ~he 11 scanning area. The checkout operator passes the article 12 70 with label 71 face down over scan window 35 in 13 preparation to place the article 70 into bag 55 which is 14 supported on shelf 56.
Label 71 is a bar coded label of the type 16 shown in Fig. 8. Label 71 is printed with a plurality of ., .. -;`-, 17 bars 72 which have a reflectance less than the background 18 area 73. Thus, as the beam scans across label 71, it is 19 modulated by the reflectance difference between the ". .
background 73 and the printed ink bars 72~ The modulated 21 reflected light is collected by photo multiplier tube 80 in 22 Fig. 1 which converts it to an electrical signal. -;~
~ 23 This electrical signal is passed to video processor 85 ~ ;
;; 24 which analyzes the electrical signal to identify the ~` 25 information represented by bar 72 on label 71.
``~ 26 The scan pattern 30 can read label 27 71 irrespective of its orientation. In the emhodiment ~-,::
-~ ! . 28 shown in Fig, 1, the end portions 31 and 32 of scan , ~ ~ , . . . .
29 pattern 30 fall outslde of or are cropped out by scan , 30 window 35. Photo detectors 90 and 95 are positioned ;` ' ~,~
'' :
: - ' ' . , .,' .
; .~ .
~.t~ 5s3 _ within housing SO near scan window 35 so as to detect 2 ~he vertical and horizontal amplikudes of the beam as 3 it traces out scan pattern 30" The signals from 4 photo detectors 90 and 95 are fed to amplitude, frequency and phase lock control circuit 100.
6 In this example scan window 35 is 7 approximately 7027 inches by 1.3 inches. Deflectors 8 20 and 25 are operated at frequencies which result 9 in an interlaced X pattern which will insure proper scanning of label 71. The X's must not be too far 11 apart or closer than necessary to properly read the 12 label 71. A ratio of 5 1/3 has been found to be 13 satis~actory for a scan window of the aforementioned 14 dimensions. In general, the scans should,cross each other at the horizontal axis of the scan window and be 16 substantially perpendicular to each other at the point ,:
17 of intersectionO Horizontal and vertical amplitude 18 control circuits keep this crossing angle constant and 19 the ~requency and phase lock circuit maintains a uniform --space in between the X's and prevents the scan pattern 21 from degenerating. Degeneration of the scan pattern 22 would cause scan voids resulting in improper reading of 23 the label 71.
24 The amplitude frequency and phase lock control circuit 100 of Fig. 1 is shown in detail in `
26 FigO 2. The horizontal and vertical amplitude control 27 circuits are substantially identical and control the ` 28 horizontal and vertical amplitudes by controlling the 29 amount of current passed by amplifiers 106 and 119 to 30 deflectors 20 and 25 respectively. Amplifiers 106 .'` `' ~ ~
~`
, ' . :
6 The use of two oscillating mirrors to 7 produce sine wave light patterns is well known in the 8 prior art as evidenced by U. S. Patents 1,756,232; 1,951,666 9 and 3,437,393. However none of these patents teach phase control to produce an X pattern without degeneration which 11 would result in scan voids. Also, in applicants' 12 invention amplitude control is needed to maintain the 13 crossing angle of the scans constant. These latter mentioned 14 patents are not directed to omnidirectional scanners.
The omnidirectional scanner of applicants' invention is 16 useful for scanning bar coded labels which may pass 17 anywhere in the scan window. Thus the X scan pattern .i :
18 should be uniform. Ideally, the scan lines should 19 intersect at the longitudinal axis of the scan window and at 45 and 135. In practice, with fV = AH
21 fH
22 where f=frequency and A-amplitude the scan lines are 23 at 45 and 135 to the longitudinal or horizontal axis ~;
24 at the center of the scan window but are at 55 and 125 at the edges. This error in applicants' invention is 26 spread out or normalized by introducing a constant 27 or stretch factor of 1.05 whereby:
28 AH = 1O05 fv . It should bè recognized that the other , -- ~
~ 29 AV
;~ 30 stretch or compression factors may be used to increase ; 31 or decrease the intersec~ion angles as may be advantageous RO973-012 -3- ~
.
,:
' ...... . . .
;
L in a particular application. The scan lines then 2 intersect at 40 and 140 at the center and 50 and 130 3 at the edges so as to be centered about the ideal 4 intersections of 45~ and 135. ' ' In applicants' invention, the ratio of 6 the low (herizontal) and high (vertical) frequencies 7 is important so as to make the X's as linear in curvature 8 as possible to reduce the unused portion of the scan and 9 thereby reduce scan speed and to interlace the scans so the X's are at an optimum spacing for scanning a particular 11 bar code label.
12 The turn around portions (nonlinear) of the 13 Lissajous scan pattern may or may not be used in the scan ~' 14 window depending upon'the type of label being scanned. I~ is ' desirable to have horizontal scans for scanning short or 16 segmented labels. The turn around portions of the Lissajous 17 pattern, although not linear, are useful for forming ~ ' 18 horizontal scans. This eliminates scan gaps whi'ch can ~-~
19 occur in the scanning arrangements of patents 3,718,761 '`~
20 and 3,728,677. Further, in app:Licants' invention, by ' ' 21 folding the end portions of the Lissajous pattern which are 22 outside of the scan window into the scan window, ~;
: .
23 substantially vertical scans are formed at the central '~
24 portion of the scan window. These vertical scans are 25 helpful for scanning worst case label conditions. ~;` -26 In applicants' invention, it is critical 27 that the frequency and phase lock system be verv accurate.
28 The mirrors are oscillated at resonance and the Q is very ; 29 high. Thus, any appreciable shift in frequency renders the - 30 system uns~able. Applicants' preferred èmbodiment uses a . ;
.
, - ~.
`, ' ' ~ .
:: : . : : ~.: . .. , , . .:,.: , ,.
1 digital Erequerlcy and phase lock sys-tem. Most prior art 2 frequency and phase lock sys-tems requirs a continuous 3 frequency change until the desired pha.se lock is achieved.
4 In such systems even a small frequency shift requires a long correction time,because to achieve system stability 6 the change in frequency must be slow. Applicants' 7 arrangement permits a relatively large change in frequency 8 because it is made instantaneously rather than being 9 continuous. Further, stability is maintained by making the changes at a slow rate; i.e., a change in frequency 11 is made only once during a predetermined sample period , 12 which occurs less frequently than the period of the oseillating mirror being controlled.
14 Summary of the Invention The principal objects of applicants' `
16 invention are to provide an improved omnidirecitonal 17 scanning system which:
18 (a) is eapable of scanning bar coded 19 labels without regard to label orientation, (b) can be used with a narrow rectangular 21 sean window, 22 (e) has high stability and accuracy, 23 (d) is highly reliable and 24 (e) is relatively inexpensive. ,; , These objects are achieved by using ' 26 an intense, substantially non-divergent light souree 27 such as a laser and deflecting the light beam with two 28 oscillating mirrors, which are phase and frequency locked, ,~ ' 29 to a narrow reetangular sean window whieh masks out the nonlinear end portions of the scan. The two mirrors `
, R0973-012 -5- ~ ~
1 are oscillated at frequenc1es which cau.se the beam to 2 trace out a pattern of ove~lapping Xls. Amplitude 3 control is included to maintain ~he light beam at a 4 constant crossing angle. ~he frequency and phase lock maintains unifoxm spacing of the X's and prevents the 6 scan pattern from degenerating.
7 Brief Description of the Drawings 8 Fig. 1 is a perspective view illustrating -9 the omnidirectional scanning system of the invention;
1~ Fig. 2 is a schematic block circuit 11 diagram of the control circuit showing a preferred 12 embodiment of the frequency and phase lock system and -~
~ . , 13 including the amplitude control circuit; - ~ ~
14 Fig. 3 is a more general schematic ~ -block circuit diagram of the frequency and phase lock 16 system of Fig. 2;
17 Fig. 4 is a waveform diagram including 18 a series of waveforms to lllustrate phase correction;
. , , ' ' . .
19 Flg. 5 ls a waveform diagram lllustrating the high and low frequency pulses for one scanner cycle;
21 Fig. 6 is a partial perspec~ive view 22 illustrating an alternate embodiment of the invention; --: . ~
23 Fig. 7 is a developed plan view illustrating , 24 the scan pattern for the alternate embodiment shown in Fig.
6;
26 Fig. 8 is a diagram showing a typical 27 label; and, 28 Fig. 9 is a perspective view illustrating 29 the invention incorpoxated in a housin~ at a check out ~ .
counter.
,''' :~
,.
.:- .: -. , :: : : .
. ~ :: : - . , .
,S~3 Descr ~
2 With re~erence to the drawings and 3 particularly to Fig. 1, the invention is illustrated 4 by way of example as including a laser light source 10 which provides an intense narrow beam of light schematically illustrated by line 11. This beam of 7 light is directed onto a beam expander 15 which includes 8 lens 16 for expanding the laser beam and focusing lens 9 17 for focusing the expanded beam and directing the beam onto mirror 21 of the horizontal torsional ~eflector 11 20.
12 The beam i5 reflected from mirror 21 to 13 mirror 26 of vertical torsional deflector 25. The terms 14 horizontal and vertical are arbitrary and could be interchanged without affecting the scope of the invention.
16 However, one of the torsional deflectors, in this example, 17 horizontal deflector 20 is operated at a lower frequency I8 than the operation of vertical deflector 25. The 19 horizontal deflector 20 and vertical deflector 25 are ;
operated at resonance with a predetermined frequency 21 ratio whereby the beam of light traces out a pattern of 22 interlaced X's 30 in scan window 35.
23 The beam from laser 10 is expanded and `
24 then focused so as to obtain a small focused spot near the large focal length of the focusing lens 170 The 26 maximum deflection angle of the torsional deflectors 27 20 and 25 dictates the focal length. However, the large 28 focal length increases the depth of field.
29 Horizontal deflector 20 moves the beam so as to scan the length of window 35 and vertical deflector 31 25 causes the beam to scan the width of window 35. The -RO973-012 -7- `
-, ~l~5~Si~;3 - combination of these orthogonal deflections at pred~termined 2 fixed frequency ~nd amplitude ratios produces the 3 pattern of interlaced X's at scan window 35.
4 Scan window 35 is located at the top of ;~
an enclosure 50, Fig. 9, for housing the previously 6 described elements. Scan window 35 is a narrow rectangular 7 aperture formed in the housing and covered by glass 8 or other suitable transparent material. ~ , 9 In Fig. 9 an article 70 bearing a bar coded '~
label 71 is transported by conveyor belt 51 to ~he 11 scanning area. The checkout operator passes the article 12 70 with label 71 face down over scan window 35 in 13 preparation to place the article 70 into bag 55 which is 14 supported on shelf 56.
Label 71 is a bar coded label of the type 16 shown in Fig. 8. Label 71 is printed with a plurality of ., .. -;`-, 17 bars 72 which have a reflectance less than the background 18 area 73. Thus, as the beam scans across label 71, it is 19 modulated by the reflectance difference between the ". .
background 73 and the printed ink bars 72~ The modulated 21 reflected light is collected by photo multiplier tube 80 in 22 Fig. 1 which converts it to an electrical signal. -;~
~ 23 This electrical signal is passed to video processor 85 ~ ;
;; 24 which analyzes the electrical signal to identify the ~` 25 information represented by bar 72 on label 71.
``~ 26 The scan pattern 30 can read label 27 71 irrespective of its orientation. In the emhodiment ~-,::
-~ ! . 28 shown in Fig, 1, the end portions 31 and 32 of scan , ~ ~ , . . . .
29 pattern 30 fall outslde of or are cropped out by scan , 30 window 35. Photo detectors 90 and 95 are positioned ;` ' ~,~
'' :
: - ' ' . , .,' .
; .~ .
~.t~ 5s3 _ within housing SO near scan window 35 so as to detect 2 ~he vertical and horizontal amplikudes of the beam as 3 it traces out scan pattern 30" The signals from 4 photo detectors 90 and 95 are fed to amplitude, frequency and phase lock control circuit 100.
6 In this example scan window 35 is 7 approximately 7027 inches by 1.3 inches. Deflectors 8 20 and 25 are operated at frequencies which result 9 in an interlaced X pattern which will insure proper scanning of label 71. The X's must not be too far 11 apart or closer than necessary to properly read the 12 label 71. A ratio of 5 1/3 has been found to be 13 satis~actory for a scan window of the aforementioned 14 dimensions. In general, the scans should,cross each other at the horizontal axis of the scan window and be 16 substantially perpendicular to each other at the point ,:
17 of intersectionO Horizontal and vertical amplitude 18 control circuits keep this crossing angle constant and 19 the ~requency and phase lock circuit maintains a uniform --space in between the X's and prevents the scan pattern 21 from degenerating. Degeneration of the scan pattern 22 would cause scan voids resulting in improper reading of 23 the label 71.
24 The amplitude frequency and phase lock control circuit 100 of Fig. 1 is shown in detail in `
26 FigO 2. The horizontal and vertical amplitude control 27 circuits are substantially identical and control the ` 28 horizontal and vertical amplitudes by controlling the 29 amount of current passed by amplifiers 106 and 119 to 30 deflectors 20 and 25 respectively. Amplifiers 106 .'` `' ~ ~
~`
, ' . :
5~
1 and 119 are controlled by the amount of voltage on 2 conductors 129 and 134 respectively. The vol~ages 3 on these conductors depends upon the charges on 4 capacitors Cl and C2 respectively. Current sowrces 126 and 131 are positive current sources and current
1 and 119 are controlled by the amount of voltage on 2 conductors 129 and 134 respectively. The vol~ages 3 on these conductors depends upon the charges on 4 capacitors Cl and C2 respectively. Current sowrces 126 and 131 are positive current sources and current
6 sources 127 and 132 are negative current sources. The
7 positive current sources 126 and 131 are turned on
8 under control of single shot multivibrators 125 and
9 130 respectively. The single shot multivibrators in ~ turn are fired by signals from the photodetectors 90 11 and g5 respectively. When either positive current source 12 is turned on, its asso d ated capacitor starts to charge 13 whereby the voltage output from the associated buffer 14 amplifier; i.eO, amplifier 128 or 133, reduces. When the positive current source is turned off, the associated 16 capacitor starts to discharge and this increases the 17 voltage at the output of the associated buffer amplifier.
18 This in turn increases the current for driving the 19 associated torsional deflectorO
Torsional deflectors 20 and 25 are ~1 driven from a system clock 101. The frequency of 22 system clock 101 is dependent upon the ~esired phase ~-23 lock accuracy because a correction is made only when 24 the phase error exceeds one cycle of the system clock.
The principles of the frequency and phase lock circuit 26 in Fig. 2 can be understood with reference to Fig. 3 27 which shows a more general digital frequency and phase 28 lock system. In Fig. 3 system clock 201 has a frequency 29 Fc. The frequency Fc = tF2)(x3(Kl)-(Fl)(y)(Kl) where the frequency F2 is either the higher or the lower of 31 ~he two frequencies. The selected ratio of the frequencies :- ~ .,,: , :
, ~3t3~
, F1 to F2 determines ~he values of X and Y. The constant 2 Kl is related to the system phase lock accuracy. In Fig.
3 3, Fl=Fc/Y Kl. This is represented hy a block 202. The 4 frequency Fl drives device 220 which corresponds to torsional deflector 20 of Figs. 1 and 2. Device 220 6 generates an output signal at a frequency Fl plus a 7 phase shift ~. The phase shift is not constant for 8 the device and varies from device to device.
9 Frequency F2 drives device 225 which corresponds to torsional deflector 25 of Figs. l and 2.
11 The frequency of device 225 is F2+~2 where ~2 is the : -r 12 phase shift from the input frequency F2. The frequencies , 13 can be locked in or out of phase depending upon the i - 14 requirements of the scan pattern which in turn is 15 dependent upon the ratio of the frequencies Fl and F2.
16 In order to phase lock with a predetermined constant ~- 17 phase shift single shot multivibrators 221 and .-18 226 can be connected into the circuit. Only one of ~;~ 19 the single shot multivibrators 221 and 226 would be connected into the circuit at any one time. In Fig. 2 , 21 as it will be seen shortly, the frequencies are phase 22 locked with a predetermined constant phase shift~ -23 The phase shifts are compared by phase ~ :
24 detector 229. However, to facilitate a phase shift comparision, the two frequencies are normalized to 26 a common frequency by blocks 223 and 228 respectively. ~ -27 The normalized frequency equals Fc/(X)(Y)(Kl)(K2).
28 The constant K2 is an integer number that determines 29 the error sampling rate of ~he phase detector 229.
By making the constant K2 large, the sample rate for 31 the phase shift comparison is kept low.
,~
i . .. ~ . . - .
: : . ~ -:- : . : ~.: ::
: . :: : - , ~3S~5S;3 If the output of block 223 lags the 2 output of block 228, phase detector 229 provides 3 a +INC signal on conductor 230 and if the output of 4 block 223 leads the output of block 228 phase detector 229 provides a +DEC signal on conductor 231. If the 6 outputs of blocks 223 and 228 are in phase, there i5 7 no output from phase detector 229. When the outputs of 8 blocks 223 and 228 are in phase, no correction is made 9 to the frequency F2 and block 205 is driven at a frequency of Fc from block 203 via AND circuit 239 which i-s 11 conditioned by +INC and +DEC signals from inverters 236 12 and 237 respectively. The output of AND circuit 239 13 feeds OR circuit 240 which in turn feeds AND circuit 204.
14 AND circuit 204 is conditioned at this time by the output~ -of inverter 237.
16 When phase detector 229 provides a 17 +INC signal on conductor 230,. AND circuit 234 is ~ -18 conditioned whereby the frequency FZ operates at twice 19 its normal frequency. The amount of correction which can take place at any one sample time is limited by ~ :
21. single shot multivibrator 233 which is fired by a signal 22 from OR circuit 232 which receives +INC and +DEC signals :
23 from phase detector 229. The output of AND circuit 234 24 is applied to AND circuit 238 which also receives an input from system clock 201. The output of AND circuit 238 is 26 applied to block 205 via OR circuit 240 and AND circuit ~ .
27 204. AND circuit 204 is conditioned at this time by the 2~ output of inverter 237. Whenever the frequency of F2 29 is to be decraased, it is reduced to zero by applying a +DEC signal to AND circuit 235. This causes the output '` `' . . ' ~ RO973-012 -12-..... . . .
~ ., ' ' ~li5 1~3;~
of inverter 237 to decondition AND circuit 204. Thus 2 block 205 is not driven by either either the ~ystem clock 3 201 or by block 203.
4 It is seen that the principles of the digital frequency and phase lock system are:
6 (a) to use a relatively high 7 frequency system clock to assure phase lock accuracy, 8 frequency division circuit (flip flops and counters) enable 9 the use of the high frequency clock;
(b) to normalize the frequencies of the 11 driven devices to a common low frequency to provide a 12 low error sample rate;
13 (c) to adjust the phase shifts with the 14 high frequency system clock or with zero frequency; and (d) to limit the amount of phase shift 16 adjustment during any one correction period.
17 In Fig. 2 the horizontal frequency is 18 selected to be 600 Hertz and the vertical frequency is 19 3.2 K Hertz. The constant Xl equals lO00, X equals 16 and Y equals 3. The frequency of system clock 101 Zl is 9.6 M Hertz. The horizontal frequency of 600 22 Hertz is derived by first dividing the system frequency ~ ~ -23 of 9.6 M Hertz in half. This is done by flip-flop 102.
24 The 4.8 M Hertz frequency is again divided in half by flip flop 103 and the resultin~ frequency of 2.4 M Hertz 26 is divided by 16 x 125 or 2000. This division is 27 accomplished by ccunter 104 to result in a frequency of 28 1.2 K Hertz. The frequency of 1.2 K Hertz is divided 29 in half by flip-flop 105 to result in a frequency of 600 Hertz which is applied to amplifier 106~ The ' : . .
-,, : . : . - . . -:
55~
_ output of amplifier 106 is applied to magnet coils 22 2 of torsional deflector 20. Colls 22 are connected in 3 parallel and drive mirrGr 21 ~hrouyh an associated 4 armature and drive rod. The torsional deflectors 20 and 25 are the type shown and described in U. S. patent 6 3,609,485 entitled "Resident Torsional Oscillators".
7 As mirror 21 is oscillated by the 8 signal from amplifier 106, signals are generated by .... .
:: 9 transducers 23 which are connected in series. Signals from transducers 23 are applied to a sine wave to a 11 square wave converter 111. The signals from the sine 12 wave to square wave converter 111 are applied to single 13 shot multivibrator 136 for generating pulses having a :....... 14 width of 78.1 ~ seconds and the frequency~ thereof is then . .
15 normalized by counter 112 which divides the frequency 16 effectively by 3 x 320 The output of counter 112 is 17 applied to phase discriminator 122.
18 In a similar manner mirror 26 of torsional 19 deflector 25 is oscillated in response to a signal from 20 amplifier 119 which is applied to coils 27. Amplifier 119 ~
21 receives a signal at a frequency of 3.2 K Hertz from flip : -:
22 flop 118. Flip flop 118 functions to divide the frequency `~ 23 from counter 117 in half. Counter 117 is driven by .: .
24 signals at the output of AND circuit 116. Counter 117 25 divides the frequency effectively by 3 x 125 or 375.
'~. 26 This maintains the frequency ratio of 5 1/3.
. 27 Counter 117 is normally advanced by 28 signals at a frequency of 2.4 M Hertz from the output of ~
29 flip flop 103 via AND circuit 113, OR circuit 115 and ~;
: 30 AND circuit 116. Howeverl if the phase shifts as detected : :
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by phase discriminator 122 are not equal, counter 117 2 will be advanced at a frequency of 4.8 M Hertz by signals 3 at the output of flip flop 102 or not advanced at all;
4 i.e., at zero ~ Hertz clepending upon whether the difference in phase shift is to be increased or decreased 6 so as to make the phase shifts equal.
7 As mirror 26 is oscillated by the output 8 of amplifier 119, transducers 28 which are connected in 9 series generate signals~ These signals are applied to sine wave to square wave converter 120 and its output is 11 normalized by counter 121 which divides the output from 12 converter 120 by 16 x 32. The output of counter 121 -~ ;
13 is applied to phase discriminator 122.
14 In this instance, the fre~uencies of the signals from transducers 23 and 28 are to be locked 16 90 out of phase with respect to the vertical frequency 17 because the transducers 23 and 28 generate signals 18 indicative of velocity rather than position and velocity 19 and position are 90 out of phase whenever the difference between the constants, i.e., Y-~X, is an odd number.
21 Hence, a single shot multivibrator corresponding 22 to single shot multivibrator 226 of Fig. 3 is included ~ , 23 to provide a predetermined constant phase shift of 24 90 with respect to the vertical frequency.
When the phase shift difference is to be 26 increased, phase discriminator 122 provides an output on 27 conductor 123 and when the phase shift difference is to 28 be decreased, it provides an output signal on conductor 29 124. Conductors 123 and 124 are connected to inputs of AND circuits 109 and 110 respectively and to inputs of 31 OR circuit 107. OR circuit 107 has its output connected ., ;
'' 5~ 3 - to slngle shot multivibrator ].08 which provides a 300 23 microsecond pulse for conditioning AND circu.its 109 and 110 thereby limiting the amount of correction at any one sample time.
S The outputs of AND circuits 109 6 and 110 are at a down level. when their inputs have been 7 satisfied. The output of AND circuit 109 is used to : 8 condition AND circuit 113 for passing the normal 9 frequency of 2.4 M Hertz from flip flop 103 to la counter 117 via OR circuit 115 and AND circuit 116.
11 Of course this occurs when the inputs to AND circuit 12 109 are not satisfied. Additionally the inputs to AND
: 13 circuit 110 must not be satisfied in this instance so 14 as to condition AND circuit 116.
.~ 15 If the inputs to AND circuit 109 are 16 satisfied, then AND circuit 114 is conditioned to pass -17 ~he frequency of 4.8 M Hertz from flip flop 102 to counter 18 117 via OR circuit 115 and AND circuit 116. AND circuit 1~ 116 will be conditioned because the inputs to AND circuit 110 are not satisfied. This is because discriminator 122 21 does not simultaneously provide signals on conductors 123 22 and 124. The inputs to AND circuit 110 are satisfied ~: 23 when the phase shift difference is to be decreased.
24 Under this condition, the output of AND circuit 110 25 deconditions AND circuit 116 and counter 117 is not 26 advanced for a period of 300 microseconds. ~:
27 The desired phase relationship for 28 the signals generated by transducers 23 and 28 is 29 represented by waveforms A and B respectively in Fig. 5.
: 30 In other words, transducers 28 generate 5 1/3 sine wave L 5 ~
pulses for each sine wave pulse generated by transducers 23. The sine wave pulses represented by wave forms A
3 and B are converted to square waves as represented by 4 wave forms D and E respectively. The conversions are made by sine wave to the square wave converters 111 and 6 120 respectively. Thus, one scanner cycle in this example 7 is equal to three low frequency pulses or 16 high frequency 8 pulses which occur in five milliseconds. Waveform C shows 9 the output of single shot multivibrator 136. Thus in every thirty second scanner cycle, phase discriminator-122 compares 11 the delayed rising edge of every third 600 Hertz pulse to the 12 rising edge of every sixteenth 3.2K hertz pulse.
13 Input 1 to phase discriminator 122, Fig.
14 2, is shown as wave form A in Fig. 4 and input 2 is ~
15 shown as waveform B. It is seen in Fig. 4, waveform A ~-16 lags waveform B. Under these conditions, phase 17 discriminator 122 provides an output signal represented 18 by a waveform C, Fig. 4 on conductor 123, Fig. 2. This 19 signal conditions AND circuit 109 whereby AND circuit 114 passes the 4.8 ~ Hertz signal from flip flop 102 to advance 21 counter 117 at this rate for a period of time during which --22 AND circuit 109 has an output. This period of time is 23 represented by waveform D in Fig. 4. It is seen in Fig. 4 24 that this corraction does not bring the inputs represanted by waveforms A and B into phase. However, successive 26 corrections bring waveforms A and B into phase as seen 27 in Fig. 4.
28 Single shot multivibrator 108 in Fig. 2 29 limits the width of tha corrections to the smallar of . .
` 30 either 300 microseconds or the phase error between inputs ,, R~973-OlZ ~17- ~
3'~ 53 1 and 2 at phase dis ~riminator 122. The correction size 2 is limited to 300 microseconds and occurs once every 3 thirty second scanner cycle. ThereEore, assuming no 4 error due to converters 111 and 120, the system could take as lony as 85 seconds to achieve lock. The system 6 lock accuracy is 0.5 with respect to torsional 7 deflector 25 or about 0.14 per cent.
8 The lock on time can be reduced 9 significantly by applying the outputs of converters 111 and 120 directly to phase discriminator 122. With this 11 arrangement, a correction window mus t be generated by 12 dividing the output of converter 120 by 32 and apply 13 the resultant si~nal to a single shot multivibrator, 14 not shown, to ~enerate a sample window of 312 ITicroseconds. ; ~ -Thus the 3.2K Hertz pulse train need only be shifted --;
16 over one period of the 600 hertz pulse train rather than ~ 17 over the period of common frequency of 6.25 Hertz. Also i 18 the correction window limits the correction pulse to a 19 maximum of 312 microseconds thus eliminating the need for the 300 microseconds single shot 108.
21 Normally the scan pattern 30 in Fig. 1 is 22 adequate for scanning the label 71 of Fig. 8. The turn 23 around portions 33 of scan pattern 30, Fig. 1, effectlvely 24 form two horizontal scans. This enhances the scanning of labels which are narrower than the one illustrated in 26 Fig. 8.
27 In some instances it may be desirable 28 to use the entire pattern for scanning modified labels.
29 If the entire pattern is used, the slope of the pattern ~-~ 30 30, Fig. 1, normally within the scan window is too shallow 31 while the slope of the portions 31 and 32 is too steep.
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1 These variances are compensated by folding the portions 31 2 and 32 in toward the center of scan window 35. The 3 folding is accomplished by side mirrors 41 ancl 42 as 4 schematically represented in Fig. 6. Mirrors 41 and 42 are notched so that photodetectors 90 and 95 can 6 amplitude sense the portion of the scan pattern outside 7 the scan window, and not reflected by one of the mirrors ~ and in this instance mirror 42. The resultant scan 9 pattern 30 is illustrated in Fig. 7. The end portions of the scan appear as substantially vertical scan lines 34 ~ :~
11 near the center of the window. The scan pattern in Fig. 7 12 is generated with a vertical frequency seven times the 13 horizontal frequency and the horizontal amplitude is 14 seven times the vertical amplitude. This pattern is easy to generate and requires less detector band width 16 than the pattern 30 of Fig. 1.
17 From the foregoing it is seen that 18 applicants' invention provides an improved omnidirectional 19 scanning system for scanning bar coded labels without .
regard to label orientation. It is seen that the two :~
21 torsional deflectors are locked in phase and frequency 22 so as to generate a pattern of interlaced X's with 23 uniform spacing of the X's. Amplitude control .is 24 provided to maintain the light beam at a constant crossing angle and the scan window is configured so as to mask out 26 the nonlinear end portions of the scanO It is also 27 seen khat the turn around portions of the scan pattern 28 form horizonkal scans so as to further reduce scan voids. ;:
29 In an alternate embodiment the end portions of the scan ~:
pattern not normally in the scan window are folded by R0973-012 -19- ;
s53 mirrors into the scan windo~~whereby two substantially 2 vertical scans are available for scanning the labels.
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18 This in turn increases the current for driving the 19 associated torsional deflectorO
Torsional deflectors 20 and 25 are ~1 driven from a system clock 101. The frequency of 22 system clock 101 is dependent upon the ~esired phase ~-23 lock accuracy because a correction is made only when 24 the phase error exceeds one cycle of the system clock.
The principles of the frequency and phase lock circuit 26 in Fig. 2 can be understood with reference to Fig. 3 27 which shows a more general digital frequency and phase 28 lock system. In Fig. 3 system clock 201 has a frequency 29 Fc. The frequency Fc = tF2)(x3(Kl)-(Fl)(y)(Kl) where the frequency F2 is either the higher or the lower of 31 ~he two frequencies. The selected ratio of the frequencies :- ~ .,,: , :
, ~3t3~
, F1 to F2 determines ~he values of X and Y. The constant 2 Kl is related to the system phase lock accuracy. In Fig.
3 3, Fl=Fc/Y Kl. This is represented hy a block 202. The 4 frequency Fl drives device 220 which corresponds to torsional deflector 20 of Figs. 1 and 2. Device 220 6 generates an output signal at a frequency Fl plus a 7 phase shift ~. The phase shift is not constant for 8 the device and varies from device to device.
9 Frequency F2 drives device 225 which corresponds to torsional deflector 25 of Figs. l and 2.
11 The frequency of device 225 is F2+~2 where ~2 is the : -r 12 phase shift from the input frequency F2. The frequencies , 13 can be locked in or out of phase depending upon the i - 14 requirements of the scan pattern which in turn is 15 dependent upon the ratio of the frequencies Fl and F2.
16 In order to phase lock with a predetermined constant ~- 17 phase shift single shot multivibrators 221 and .-18 226 can be connected into the circuit. Only one of ~;~ 19 the single shot multivibrators 221 and 226 would be connected into the circuit at any one time. In Fig. 2 , 21 as it will be seen shortly, the frequencies are phase 22 locked with a predetermined constant phase shift~ -23 The phase shifts are compared by phase ~ :
24 detector 229. However, to facilitate a phase shift comparision, the two frequencies are normalized to 26 a common frequency by blocks 223 and 228 respectively. ~ -27 The normalized frequency equals Fc/(X)(Y)(Kl)(K2).
28 The constant K2 is an integer number that determines 29 the error sampling rate of ~he phase detector 229.
By making the constant K2 large, the sample rate for 31 the phase shift comparison is kept low.
,~
i . .. ~ . . - .
: : . ~ -:- : . : ~.: ::
: . :: : - , ~3S~5S;3 If the output of block 223 lags the 2 output of block 228, phase detector 229 provides 3 a +INC signal on conductor 230 and if the output of 4 block 223 leads the output of block 228 phase detector 229 provides a +DEC signal on conductor 231. If the 6 outputs of blocks 223 and 228 are in phase, there i5 7 no output from phase detector 229. When the outputs of 8 blocks 223 and 228 are in phase, no correction is made 9 to the frequency F2 and block 205 is driven at a frequency of Fc from block 203 via AND circuit 239 which i-s 11 conditioned by +INC and +DEC signals from inverters 236 12 and 237 respectively. The output of AND circuit 239 13 feeds OR circuit 240 which in turn feeds AND circuit 204.
14 AND circuit 204 is conditioned at this time by the output~ -of inverter 237.
16 When phase detector 229 provides a 17 +INC signal on conductor 230,. AND circuit 234 is ~ -18 conditioned whereby the frequency FZ operates at twice 19 its normal frequency. The amount of correction which can take place at any one sample time is limited by ~ :
21. single shot multivibrator 233 which is fired by a signal 22 from OR circuit 232 which receives +INC and +DEC signals :
23 from phase detector 229. The output of AND circuit 234 24 is applied to AND circuit 238 which also receives an input from system clock 201. The output of AND circuit 238 is 26 applied to block 205 via OR circuit 240 and AND circuit ~ .
27 204. AND circuit 204 is conditioned at this time by the 2~ output of inverter 237. Whenever the frequency of F2 29 is to be decraased, it is reduced to zero by applying a +DEC signal to AND circuit 235. This causes the output '` `' . . ' ~ RO973-012 -12-..... . . .
~ ., ' ' ~li5 1~3;~
of inverter 237 to decondition AND circuit 204. Thus 2 block 205 is not driven by either either the ~ystem clock 3 201 or by block 203.
4 It is seen that the principles of the digital frequency and phase lock system are:
6 (a) to use a relatively high 7 frequency system clock to assure phase lock accuracy, 8 frequency division circuit (flip flops and counters) enable 9 the use of the high frequency clock;
(b) to normalize the frequencies of the 11 driven devices to a common low frequency to provide a 12 low error sample rate;
13 (c) to adjust the phase shifts with the 14 high frequency system clock or with zero frequency; and (d) to limit the amount of phase shift 16 adjustment during any one correction period.
17 In Fig. 2 the horizontal frequency is 18 selected to be 600 Hertz and the vertical frequency is 19 3.2 K Hertz. The constant Xl equals lO00, X equals 16 and Y equals 3. The frequency of system clock 101 Zl is 9.6 M Hertz. The horizontal frequency of 600 22 Hertz is derived by first dividing the system frequency ~ ~ -23 of 9.6 M Hertz in half. This is done by flip-flop 102.
24 The 4.8 M Hertz frequency is again divided in half by flip flop 103 and the resultin~ frequency of 2.4 M Hertz 26 is divided by 16 x 125 or 2000. This division is 27 accomplished by ccunter 104 to result in a frequency of 28 1.2 K Hertz. The frequency of 1.2 K Hertz is divided 29 in half by flip-flop 105 to result in a frequency of 600 Hertz which is applied to amplifier 106~ The ' : . .
-,, : . : . - . . -:
55~
_ output of amplifier 106 is applied to magnet coils 22 2 of torsional deflector 20. Colls 22 are connected in 3 parallel and drive mirrGr 21 ~hrouyh an associated 4 armature and drive rod. The torsional deflectors 20 and 25 are the type shown and described in U. S. patent 6 3,609,485 entitled "Resident Torsional Oscillators".
7 As mirror 21 is oscillated by the 8 signal from amplifier 106, signals are generated by .... .
:: 9 transducers 23 which are connected in series. Signals from transducers 23 are applied to a sine wave to a 11 square wave converter 111. The signals from the sine 12 wave to square wave converter 111 are applied to single 13 shot multivibrator 136 for generating pulses having a :....... 14 width of 78.1 ~ seconds and the frequency~ thereof is then . .
15 normalized by counter 112 which divides the frequency 16 effectively by 3 x 320 The output of counter 112 is 17 applied to phase discriminator 122.
18 In a similar manner mirror 26 of torsional 19 deflector 25 is oscillated in response to a signal from 20 amplifier 119 which is applied to coils 27. Amplifier 119 ~
21 receives a signal at a frequency of 3.2 K Hertz from flip : -:
22 flop 118. Flip flop 118 functions to divide the frequency `~ 23 from counter 117 in half. Counter 117 is driven by .: .
24 signals at the output of AND circuit 116. Counter 117 25 divides the frequency effectively by 3 x 125 or 375.
'~. 26 This maintains the frequency ratio of 5 1/3.
. 27 Counter 117 is normally advanced by 28 signals at a frequency of 2.4 M Hertz from the output of ~
29 flip flop 103 via AND circuit 113, OR circuit 115 and ~;
: 30 AND circuit 116. Howeverl if the phase shifts as detected : :
:' :
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:
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, . . .
55~
by phase discriminator 122 are not equal, counter 117 2 will be advanced at a frequency of 4.8 M Hertz by signals 3 at the output of flip flop 102 or not advanced at all;
4 i.e., at zero ~ Hertz clepending upon whether the difference in phase shift is to be increased or decreased 6 so as to make the phase shifts equal.
7 As mirror 26 is oscillated by the output 8 of amplifier 119, transducers 28 which are connected in 9 series generate signals~ These signals are applied to sine wave to square wave converter 120 and its output is 11 normalized by counter 121 which divides the output from 12 converter 120 by 16 x 32. The output of counter 121 -~ ;
13 is applied to phase discriminator 122.
14 In this instance, the fre~uencies of the signals from transducers 23 and 28 are to be locked 16 90 out of phase with respect to the vertical frequency 17 because the transducers 23 and 28 generate signals 18 indicative of velocity rather than position and velocity 19 and position are 90 out of phase whenever the difference between the constants, i.e., Y-~X, is an odd number.
21 Hence, a single shot multivibrator corresponding 22 to single shot multivibrator 226 of Fig. 3 is included ~ , 23 to provide a predetermined constant phase shift of 24 90 with respect to the vertical frequency.
When the phase shift difference is to be 26 increased, phase discriminator 122 provides an output on 27 conductor 123 and when the phase shift difference is to 28 be decreased, it provides an output signal on conductor 29 124. Conductors 123 and 124 are connected to inputs of AND circuits 109 and 110 respectively and to inputs of 31 OR circuit 107. OR circuit 107 has its output connected ., ;
'' 5~ 3 - to slngle shot multivibrator ].08 which provides a 300 23 microsecond pulse for conditioning AND circu.its 109 and 110 thereby limiting the amount of correction at any one sample time.
S The outputs of AND circuits 109 6 and 110 are at a down level. when their inputs have been 7 satisfied. The output of AND circuit 109 is used to : 8 condition AND circuit 113 for passing the normal 9 frequency of 2.4 M Hertz from flip flop 103 to la counter 117 via OR circuit 115 and AND circuit 116.
11 Of course this occurs when the inputs to AND circuit 12 109 are not satisfied. Additionally the inputs to AND
: 13 circuit 110 must not be satisfied in this instance so 14 as to condition AND circuit 116.
.~ 15 If the inputs to AND circuit 109 are 16 satisfied, then AND circuit 114 is conditioned to pass -17 ~he frequency of 4.8 M Hertz from flip flop 102 to counter 18 117 via OR circuit 115 and AND circuit 116. AND circuit 1~ 116 will be conditioned because the inputs to AND circuit 110 are not satisfied. This is because discriminator 122 21 does not simultaneously provide signals on conductors 123 22 and 124. The inputs to AND circuit 110 are satisfied ~: 23 when the phase shift difference is to be decreased.
24 Under this condition, the output of AND circuit 110 25 deconditions AND circuit 116 and counter 117 is not 26 advanced for a period of 300 microseconds. ~:
27 The desired phase relationship for 28 the signals generated by transducers 23 and 28 is 29 represented by waveforms A and B respectively in Fig. 5.
: 30 In other words, transducers 28 generate 5 1/3 sine wave L 5 ~
pulses for each sine wave pulse generated by transducers 23. The sine wave pulses represented by wave forms A
3 and B are converted to square waves as represented by 4 wave forms D and E respectively. The conversions are made by sine wave to the square wave converters 111 and 6 120 respectively. Thus, one scanner cycle in this example 7 is equal to three low frequency pulses or 16 high frequency 8 pulses which occur in five milliseconds. Waveform C shows 9 the output of single shot multivibrator 136. Thus in every thirty second scanner cycle, phase discriminator-122 compares 11 the delayed rising edge of every third 600 Hertz pulse to the 12 rising edge of every sixteenth 3.2K hertz pulse.
13 Input 1 to phase discriminator 122, Fig.
14 2, is shown as wave form A in Fig. 4 and input 2 is ~
15 shown as waveform B. It is seen in Fig. 4, waveform A ~-16 lags waveform B. Under these conditions, phase 17 discriminator 122 provides an output signal represented 18 by a waveform C, Fig. 4 on conductor 123, Fig. 2. This 19 signal conditions AND circuit 109 whereby AND circuit 114 passes the 4.8 ~ Hertz signal from flip flop 102 to advance 21 counter 117 at this rate for a period of time during which --22 AND circuit 109 has an output. This period of time is 23 represented by waveform D in Fig. 4. It is seen in Fig. 4 24 that this corraction does not bring the inputs represanted by waveforms A and B into phase. However, successive 26 corrections bring waveforms A and B into phase as seen 27 in Fig. 4.
28 Single shot multivibrator 108 in Fig. 2 29 limits the width of tha corrections to the smallar of . .
` 30 either 300 microseconds or the phase error between inputs ,, R~973-OlZ ~17- ~
3'~ 53 1 and 2 at phase dis ~riminator 122. The correction size 2 is limited to 300 microseconds and occurs once every 3 thirty second scanner cycle. ThereEore, assuming no 4 error due to converters 111 and 120, the system could take as lony as 85 seconds to achieve lock. The system 6 lock accuracy is 0.5 with respect to torsional 7 deflector 25 or about 0.14 per cent.
8 The lock on time can be reduced 9 significantly by applying the outputs of converters 111 and 120 directly to phase discriminator 122. With this 11 arrangement, a correction window mus t be generated by 12 dividing the output of converter 120 by 32 and apply 13 the resultant si~nal to a single shot multivibrator, 14 not shown, to ~enerate a sample window of 312 ITicroseconds. ; ~ -Thus the 3.2K Hertz pulse train need only be shifted --;
16 over one period of the 600 hertz pulse train rather than ~ 17 over the period of common frequency of 6.25 Hertz. Also i 18 the correction window limits the correction pulse to a 19 maximum of 312 microseconds thus eliminating the need for the 300 microseconds single shot 108.
21 Normally the scan pattern 30 in Fig. 1 is 22 adequate for scanning the label 71 of Fig. 8. The turn 23 around portions 33 of scan pattern 30, Fig. 1, effectlvely 24 form two horizontal scans. This enhances the scanning of labels which are narrower than the one illustrated in 26 Fig. 8.
27 In some instances it may be desirable 28 to use the entire pattern for scanning modified labels.
29 If the entire pattern is used, the slope of the pattern ~-~ 30 30, Fig. 1, normally within the scan window is too shallow 31 while the slope of the portions 31 and 32 is too steep.
:
- ~: .:, , - -~5~55~
1 These variances are compensated by folding the portions 31 2 and 32 in toward the center of scan window 35. The 3 folding is accomplished by side mirrors 41 ancl 42 as 4 schematically represented in Fig. 6. Mirrors 41 and 42 are notched so that photodetectors 90 and 95 can 6 amplitude sense the portion of the scan pattern outside 7 the scan window, and not reflected by one of the mirrors ~ and in this instance mirror 42. The resultant scan 9 pattern 30 is illustrated in Fig. 7. The end portions of the scan appear as substantially vertical scan lines 34 ~ :~
11 near the center of the window. The scan pattern in Fig. 7 12 is generated with a vertical frequency seven times the 13 horizontal frequency and the horizontal amplitude is 14 seven times the vertical amplitude. This pattern is easy to generate and requires less detector band width 16 than the pattern 30 of Fig. 1.
17 From the foregoing it is seen that 18 applicants' invention provides an improved omnidirectional 19 scanning system for scanning bar coded labels without .
regard to label orientation. It is seen that the two :~
21 torsional deflectors are locked in phase and frequency 22 so as to generate a pattern of interlaced X's with 23 uniform spacing of the X's. Amplitude control .is 24 provided to maintain the light beam at a constant crossing angle and the scan window is configured so as to mask out 26 the nonlinear end portions of the scanO It is also 27 seen khat the turn around portions of the scan pattern 28 form horizonkal scans so as to further reduce scan voids. ;:
29 In an alternate embodiment the end portions of the scan ~:
pattern not normally in the scan window are folded by R0973-012 -19- ;
s53 mirrors into the scan windo~~whereby two substantially 2 vertical scans are available for scanning the labels.
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Claims (9)
1. An omnidirectional scanning system for scanning bar coded labels on randomly oriented articles comprising a scan window;
a light source for providing a beam of light;
first light beam deflecting means positioned to receive said beam of light and deflect it in a first direction relative to said scan window;
second light beam deflecting means positioned to receive the beam of light deflected by said first light beam deflecting means and deflect it in a second direction relative to said scan window;
driving means for driving said first and second light beam deflecting means at first and second frequencies whereby the light beam traces within said scan window a series of interlaced X's; and control means for controlling said driving means so that said first and second light beam deflecting means are locked in frequency and phase.
a light source for providing a beam of light;
first light beam deflecting means positioned to receive said beam of light and deflect it in a first direction relative to said scan window;
second light beam deflecting means positioned to receive the beam of light deflected by said first light beam deflecting means and deflect it in a second direction relative to said scan window;
driving means for driving said first and second light beam deflecting means at first and second frequencies whereby the light beam traces within said scan window a series of interlaced X's; and control means for controlling said driving means so that said first and second light beam deflecting means are locked in frequency and phase.
2. The omnidirectional scanning system of claim 1 wherein said light source is a laser.
3. The omnidirectional scanning system of claim 1 wherein said first and second light beam deflecting means are torsional deflectors.
4. The omnidirectional scanning system of claim 1 wherein said control means are digital.
Claims 1, 2, 3 and 4 5. The omnidirectional scanning system of claim 1 further comprising:
amplitude control means for sensing the amplitudes of said first and second beam deflections to generate first and second amplitude control signals and circuit means for applying said first and second amplitude control signals to said driving means.
Claims 1, 2, 3 and 4 5. The omnidirectional scanning system of claim 1 further comprising:
amplitude control means for sensing the amplitudes of said first and second beam deflections to generate first and second amplitude control signals and circuit means for applying said first and second amplitude control signals to said driving means.
Claim 5 6. An omnidirectional scanning system for scanning coded labels on randomly oriented articles transported along a path through a scanning station comprising a scan window positioned in the plane of said transport path;
light source means for providing a beam of light having a predetermined width;
first light beam deflector means oscillating at a first predetermined frequency and positioned to deflect said light beam away from said light source and in a first direction relative to said scan window;
second light beam deflector means oscillating at a second predetermined frequency and positioned to deflect the light beam deflected by said first deflector means in a second direction relative to said scan window whereby said deflected light beam moves along a path inside and outside of said scan window so that path in said scan window appears as a series of interlaced X's;
first oscillating means for oscillating said first beam deflector means at said first predetermined frequency;
second oscillating means for oscillating said second beam deflector means at said second predetermined means for locking said first and second oscillating means in phase and frequency.
light source means for providing a beam of light having a predetermined width;
first light beam deflector means oscillating at a first predetermined frequency and positioned to deflect said light beam away from said light source and in a first direction relative to said scan window;
second light beam deflector means oscillating at a second predetermined frequency and positioned to deflect the light beam deflected by said first deflector means in a second direction relative to said scan window whereby said deflected light beam moves along a path inside and outside of said scan window so that path in said scan window appears as a series of interlaced X's;
first oscillating means for oscillating said first beam deflector means at said first predetermined frequency;
second oscillating means for oscillating said second beam deflector means at said second predetermined means for locking said first and second oscillating means in phase and frequency.
Claim 6 7. The omnidirectional scanning system of claim 6 wherein said means for locking said first and second oscillating means in phase and frequency comprises oscillator means for providing signals at third and fourth frequencies, said third frequency being greater than said first and second predetermined frequencies and said fourth frequency being less than said first and second frequencies;
first signal generating means for generating a signal proportional to the frequency of said first light beam deflector means second signal generating means for generating a signal proportional to the frequency of said second light beam deflector means;
phase detecting means connected to receive the signals from said first and second signal generating means and responsive to generate increase and decrease control signals when said signals from said first and second generating means are out of phase in first and second directions respectively; and logic means connected to receive signals at said second, third and fourth frequencies and connected to operate said second oscillating means at said second frequency in the absence of said increase and decrease control signals and to operate said second oscillating means at said third and fourth frequencies in response to increase and decrease control signals respectively.
first signal generating means for generating a signal proportional to the frequency of said first light beam deflector means second signal generating means for generating a signal proportional to the frequency of said second light beam deflector means;
phase detecting means connected to receive the signals from said first and second signal generating means and responsive to generate increase and decrease control signals when said signals from said first and second generating means are out of phase in first and second directions respectively; and logic means connected to receive signals at said second, third and fourth frequencies and connected to operate said second oscillating means at said second frequency in the absence of said increase and decrease control signals and to operate said second oscillating means at said third and fourth frequencies in response to increase and decrease control signals respectively.
Claim 7 8. The omnidirectional scanning system of claim 7 wherein said logic means includes means for limiting the amount of time said increase and decrease control signals are present to operate said second oscillating means at said third and fourth frequencies.
Claim 8
9. An omnidirectional scanning system for scanning bar coded labels on ran-domly oriented articles comprising a scan window, a light source for providing a beam of light, first light beam deflecting means positioned to receive said beam of light and deflect it in a first direction relative to said scan window, second light beam deflecting means positioned to receive the beam of light deflected by said first light beam deflecting means and deflect it in a second direction relative to said scan window, first driving means for oscillating said first light beam deflecting means over a predetermined deflection amplitude at a predetermined frequency, second driving means for oscillating said second beam deflecting means over a predetermined deflection amplitude at a ratio frequency of said predetermined frequency, sensing means for sensing the phase relationship between said first and second light beam deflecting means to develop an error signal proportional to the degree said first and second light beam deflecting means are out of a pre-determined phase relationship, and means for applying said error signal to said second driving means to bring said first and second beam deflecting means into said predetermined phase.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US382783A US3919527A (en) | 1973-07-26 | 1973-07-26 | Omnidirectional optical scanner |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1051553A true CA1051553A (en) | 1979-03-27 |
Family
ID=23510403
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA203,370A Expired CA1051553A (en) | 1973-07-26 | 1974-06-25 | Omnidirectional optical scanner |
Country Status (7)
| Country | Link |
|---|---|
| US (1) | US3919527A (en) |
| JP (1) | JPS5330617B2 (en) |
| CA (1) | CA1051553A (en) |
| DE (1) | DE2431973C3 (en) |
| FR (1) | FR2238972B1 (en) |
| GB (1) | GB1464982A (en) |
| IT (1) | IT1014625B (en) |
Families Citing this family (43)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4009369A (en) * | 1974-05-03 | 1977-02-22 | Schiller Industries, Inc. | Polyphase scanner for bar code symbols |
| US4041322A (en) * | 1974-05-03 | 1977-08-09 | Schiller Industries, Inc. | Apparatus for generating polyphase scan patterns |
| US4025761A (en) * | 1975-04-16 | 1977-05-24 | Schiller Industries, Inc. | Optical system for code symbol scanners |
| DE2618195C2 (en) * | 1975-05-02 | 1983-06-16 | Sweda International, Inc., 07058 Pine Brook, N.J. | Optical-mechanical scanning device |
| JPS527249A (en) * | 1975-07-07 | 1977-01-20 | Omron Tateisi Electronics Co | Automatic scanning width control unit |
| US4034230A (en) * | 1975-10-24 | 1977-07-05 | Bulova Watch Company, Inc. | Electro-optical bar-code scanning unit |
| JPS5255544A (en) * | 1975-10-28 | 1977-05-07 | Schiller Industries Inc | Apparatus for producing multiiphase scan pattern |
| US4079605A (en) * | 1976-05-03 | 1978-03-21 | Schlage Lock Company | Optical key reader for door locks |
| JPS5327326A (en) * | 1976-08-27 | 1978-03-14 | Mitsubishi Electric Corp | Scanning system |
| JPS5333529A (en) * | 1976-09-09 | 1978-03-29 | Mitsubishi Electric Corp | Automatic reading system |
| US4089269A (en) * | 1977-03-28 | 1978-05-16 | Mekontrol, Incorporated | Vehicle control system |
| JPS5414754A (en) * | 1977-07-06 | 1979-02-03 | Canon Inc | Scanning optical system |
| US4282431A (en) * | 1979-10-18 | 1981-08-04 | E. I. Du Pont De Nemours And Company | Bar code scanner |
| US4387297B1 (en) * | 1980-02-29 | 1995-09-12 | Symbol Technologies Inc | Portable laser scanning system and scanning methods |
| US4788423A (en) * | 1987-05-26 | 1988-11-29 | Santa Barbara Research Center | Two-mirror scanning system |
| US4871904A (en) * | 1987-12-28 | 1989-10-03 | Symbol Technologies, Inc. | Multidirectional optical scanner |
| US4859846A (en) * | 1988-07-21 | 1989-08-22 | Burrer Gordon J | Dual-mode resonant scanning system |
| WO1991017516A1 (en) * | 1990-05-02 | 1991-11-14 | Intermec Corporation | Oscillatable holographic optical element for bar code scanning |
| US5047630A (en) * | 1990-08-22 | 1991-09-10 | Confer Charles L | Modified dual-mode resonant scanning system |
| US5216232A (en) * | 1990-09-10 | 1993-06-01 | Metrologic Instruments, Inc. | Projection laser scanner producing a narrow scan volume |
| US5796091A (en) * | 1993-11-24 | 1998-08-18 | Metrologic Instruments, Inc. | Automatic hand-supportable omnidirectional laser projection scanner with handle-controllable projection axis |
| US5942743A (en) * | 1994-08-17 | 1999-08-24 | Metrologic Instruments, Inc. | Portable automatic hand-supportable omnidirectional laser projection scanner with power conserving control system |
| US5844227A (en) * | 1993-11-24 | 1998-12-01 | Metrologic Instruments, Inc. | Automatic hand-supportable omnidirectional laser projection scanner with scan-head directed projection axis for intuitive hand-supported omnidirectional scanning of bar code symbols within a narrowly confined scanning volume extending thereabout |
| US6098885A (en) | 1990-09-10 | 2000-08-08 | Metrologic Instruments | Countertop projection laser scanning system for omnidirectional scanning volume projected above a countertop surface of code symbols within a narrowly-confined scanning |
| US6651890B2 (en) | 1990-09-10 | 2003-11-25 | Sung Ho Byun | Combination hand-held and counter-top omnidirectional scanner |
| US6286760B1 (en) | 1994-08-17 | 2001-09-11 | Metrologic Instruments, Inc. | Automatic hand-supportable laser projection scanner for omni-directional reading of bar code symbols within a narrowly confined scanning volume |
| US6182898B1 (en) | 1993-11-24 | 2001-02-06 | Metrologic Instruments, Inc. | Bar code scanner with intuitive head aiming and collimated scan volume |
| US6257492B1 (en) | 1990-09-10 | 2001-07-10 | Peter Bressler | Combination hand-held and counter-top omni-directional scanner |
| US6227450B1 (en) * | 1990-09-11 | 2001-05-08 | Metrologic Instruments, Inc. | Electronically-controlled mechanically-damped off-resonant light beam scanning mechanism and code symbol readers employing the same |
| US6874689B2 (en) * | 1990-09-11 | 2005-04-05 | Metrologic Instruments, Inc. | Laser beam scanning device employing a scanning element having a flexible photo-etched gap region disposed between an anchored base portion and a light beam deflecting portion having a natural frequency of oscillation tuned by the physical dimensions of said flexible photo-etched gap region and forcibly oscillated about a fixed pivot point at an electronically-controlled frequency of oscillation substantially different from said natural resonant frequency of oscillation |
| US6742709B2 (en) | 1990-09-11 | 2004-06-01 | Metrologic Instruments, Inc. | Bar code symbol reading system employing electronically-controlled raster-type laser scanner for reading bar code symbols during hands-on and hands-free modes of operation |
| US6860427B1 (en) | 1993-11-24 | 2005-03-01 | Metrologic Instruments, Inc. | Automatic optical projection scanner for omni-directional reading of bar code symbols within a confined scanning volume |
| US6604684B1 (en) | 1993-11-24 | 2003-08-12 | Metrologic Instruments Inc. | Automatic optical projection scanner for omni-directional reading of bar code symbols within a confined scanning volume |
| US6073846A (en) * | 1994-08-17 | 2000-06-13 | Metrologic Instruments, Inc. | Holographic laser scanning system and process and apparatus and method |
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| US7051922B2 (en) | 1994-08-17 | 2006-05-30 | Metrologic Instruments, Inc. | Compact bioptical laser scanning system |
| US7124950B2 (en) * | 1997-09-16 | 2006-10-24 | Metrologic Instruments, Inc. | Bar code symbol reading system employing electronically-controlled raster-type laser scanner for reading bar code symbols during on hands-on and hands-free modes of operation |
| JP4330762B2 (en) | 2000-04-21 | 2009-09-16 | 富士フイルム株式会社 | Multi-beam exposure system |
| JP4620901B2 (en) * | 2001-06-04 | 2011-01-26 | キヤノン株式会社 | Two-dimensional optical scanning device and method for driving the two-dimensional optical scanning device |
| KR100636347B1 (en) * | 2004-08-18 | 2006-10-19 | 엘지전자 주식회사 | Raster Scanning Display System |
| US7182263B2 (en) * | 2004-09-30 | 2007-02-27 | Symbol Technologies, Inc. | Monitoring light beam position in electro-optical readers and image projectors |
| US9495571B1 (en) | 2015-09-30 | 2016-11-15 | Datalogic Automation, Inc. | Two-dimensional representation of linear barcode derived from laser barcode scanner scanline data |
| US11307403B2 (en) * | 2019-04-05 | 2022-04-19 | Infineon Technologies Ag | Synchronization of microelectromechanical system (MEMS) mirrors |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3684867A (en) * | 1970-07-15 | 1972-08-15 | Norbert Karl Acker | Apparatus for reading randomly positioned data |
| US3677465A (en) * | 1970-09-21 | 1972-07-18 | Everett A Johnson | Method and apparatus for authentication of information records |
| US3701098A (en) * | 1971-06-15 | 1972-10-24 | Scanner | Device for machine reading of information without manipulation of the information carrier |
| DE2208459C2 (en) * | 1972-02-23 | 1974-02-14 | Anker-Werke Ag, 4800 Bielefeld | Optical scanning device |
-
1973
- 1973-07-26 US US382783A patent/US3919527A/en not_active Expired - Lifetime
-
1974
- 1974-05-31 IT IT23414/74A patent/IT1014625B/en active
- 1974-06-17 FR FR7422154A patent/FR2238972B1/fr not_active Expired
- 1974-06-25 CA CA203,370A patent/CA1051553A/en not_active Expired
- 1974-07-03 DE DE19742431973 patent/DE2431973C3/en not_active Expired
- 1974-07-05 GB GB2980174A patent/GB1464982A/en not_active Expired
- 1974-07-16 JP JP8082274A patent/JPS5330617B2/ja not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| USB382783I5 (en) | 1975-01-28 |
| US3919527A (en) | 1975-11-11 |
| FR2238972B1 (en) | 1976-10-22 |
| GB1464982A (en) | 1977-02-16 |
| DE2431973C3 (en) | 1977-05-05 |
| DE2431973B2 (en) | 1976-09-16 |
| DE2431973A1 (en) | 1975-02-20 |
| FR2238972A1 (en) | 1975-02-21 |
| JPS5330617B2 (en) | 1978-08-28 |
| IT1014625B (en) | 1977-04-30 |
| JPS5040142A (en) | 1975-04-12 |
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