CA1143971A - High efficiency symmetrical scanning optics - Google Patents
High efficiency symmetrical scanning opticsInfo
- Publication number
- CA1143971A CA1143971A CA000360909A CA360909A CA1143971A CA 1143971 A CA1143971 A CA 1143971A CA 000360909 A CA000360909 A CA 000360909A CA 360909 A CA360909 A CA 360909A CA 1143971 A CA1143971 A CA 1143971A
- Authority
- CA
- Canada
- Prior art keywords
- lens
- facets
- light beam
- cylinderical
- scanning
- 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
- 238000003384 imaging method Methods 0.000 claims abstract description 23
- 230000003287 optical effect Effects 0.000 claims description 33
- 238000012937 correction Methods 0.000 claims description 13
- 238000010408 sweeping Methods 0.000 claims description 2
- 229910052729 chemical element Inorganic materials 0.000 claims 1
- 230000001419 dependent effect Effects 0.000 description 4
- 238000006073 displacement reaction Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 238000013461 design Methods 0.000 description 3
- 230000004075 alteration Effects 0.000 description 2
- 238000013459 approach Methods 0.000 description 2
- 238000005452 bending Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000000135 prohibitive effect Effects 0.000 description 1
- FBWNMEQMRUMQSO-UHFFFAOYSA-N tergitol NP-9 Chemical compound CCCCCCCCCC1=CC=C(OCCOCCOCCOCCOCCOCCOCCOCCOCCO)C=C1 FBWNMEQMRUMQSO-UHFFFAOYSA-N 0.000 description 1
- 230000004304 visual acuity Effects 0.000 description 1
Classifications
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/08—Mirrors
- G02B5/09—Multifaceted or polygonal mirrors, e.g. polygonal scanning mirrors; Fresnel mirrors
Abstract
ABSTRACT OF THE DISCLOSURE
To provide a relatively compact and linear underfilled multi-faceted rotating polygon beam scanning system, there are imaging optics for bringing a input light beam to a tangentially extending line-like focus on suc-cessive facets of a rotating polygonal scanning element and for restoring the light beam reflected from the facets to a generally circular focus on an image plane. Each of the facets subtends a sufficient angle about the axis of rotation of the scanner to ensure that the input beam remains fully seated on a single facet while the reflected beam is being scanned through a desired scan angle. Furthermore, improved linearity is achieved because the scan-ning system is symmetrical in the tangential and sagittal planes at all points between the imaging optics and the polygonal scanning element.
To provide a relatively compact and linear underfilled multi-faceted rotating polygon beam scanning system, there are imaging optics for bringing a input light beam to a tangentially extending line-like focus on suc-cessive facets of a rotating polygonal scanning element and for restoring the light beam reflected from the facets to a generally circular focus on an image plane. Each of the facets subtends a sufficient angle about the axis of rotation of the scanner to ensure that the input beam remains fully seated on a single facet while the reflected beam is being scanned through a desired scan angle. Furthermore, improved linearity is achieved because the scan-ning system is symmetrical in the tangential and sagittal planes at all points between the imaging optics and the polygonal scanning element.
Description
~397~
~ACKGROUND OF THE INVENTION
_ This invention relates to flying spot optical scanning systems and, more particularly, to optical scanning systems having multi-faceted ro~ating polygon beam scanning elements.
Multi-faceted rotating polygon beam scanning elements are commonly utilized in flying spot optical scanning systems. For example, they are frequently employed in raster input and output scanners for cycli-cally scarming an unmodulated or a modulated light beam through a prede-termined scan angle in a line scanning direction, As a general rule, a polygonal scanning element is rotated at an essentially constant angular velocity so that its facets sequentially inter-cept and reflect an input llght beam. To avoid unwanted vignetting of the reflected light beam, provision is conventional~y made for Dreventing the illu~
mination of the active scanning facet from varying as a function of the rotationof the scanning elementO To that end, some multi-faceted rotating polygon beam scanners are operated in a so-called overfilled mode in which two or more of the facets are simultaneously illuminated by the input beam. See, for example, U.S. Patent No. 3,995,110. While overEllled scanners have been used with substantial success, such as in the commercially available 9700 elec-tronic printing system of Xerox Corporation, they suffer from the disadvan-tage that a substantial part (i.e. 50% or more) of the available optical energy is wasted due to ~he inherent truncation of the input beam. Thus, others have ,. :
~ 3~
suggested that such scanners be operated in a fully filled mode or underfilled mode to avoid truncating the input beam. However, fully filled systems have tended to be relatively complex because they generally require facet tracking to maintain the input beam fully seated on the scanning facet while the reflected beam is being scanned through a desired scan angle. Underfilled systems, on the other hand, have traditionally been rather bulky and non-linear.See, for example, U.S. Patent Nos. 3,675,016 and 3,750,1~9.
SUMMARY OF THE INVENITON
In accordance with the presen~ invention, to provide a relatively compact and linear underfilled multi-faceted rotating polygon beam scanning system, there are imaging optics for sequentially bringing an input light beam to a tangentially exten&ng line-like focus on successive facets of a rotating polygonal scanning element and for restoring the light beam reflected from the facets to a more circular focus on an image plane to provide a generàlly cir-cular scanning spot. Each of the facets subtends a sufficient angle about the axis of rotation of the scanning element to ensure that the input beam remains fully seated on a single facet while the reflected bearn is being scanned through a desired scan angle. Furthermore, improved linearity is achieved because the scanning system is symmetrical in the tangential and sagittal planes at all points between the imaging optics and the scanning element.
More particularly, to perform a relatively linear wide angle scan over a flat field, the imaging optics comprise a spherical focusing lens and at least one cylinderical sagittal correction lens. The sperical lens is positionedbetween the scanning element and the cylinderical lens or lenses and is used in a symmetrical double pass mode to focus the input and reflected beams.
The curvature of the spherical lens is selected to compensate for the tendency of the scanning spot velocity to vary as a function of the field position. A
single cylinderical sagittal correction lens may be used in a symmetrical ~ -double pass mode for both input and reflected beams if the sagittal angular displacement between those beams is less than 5 or so. If the displacement ; ~ -angle substantially exceeds that limit, the cost of avoiding excessive aberrations while using a single cylinderical lens is likely to be prohibitive.
~hus, the preferred approach for systems involving a relatively large sagittal angular displacernent between the input and reflected beams is to provide separate, substantially identical and symmetrically positioned, cylinderical sagittal correction lenses for the input and reflected beams. At any rate,
~ACKGROUND OF THE INVENTION
_ This invention relates to flying spot optical scanning systems and, more particularly, to optical scanning systems having multi-faceted ro~ating polygon beam scanning elements.
Multi-faceted rotating polygon beam scanning elements are commonly utilized in flying spot optical scanning systems. For example, they are frequently employed in raster input and output scanners for cycli-cally scarming an unmodulated or a modulated light beam through a prede-termined scan angle in a line scanning direction, As a general rule, a polygonal scanning element is rotated at an essentially constant angular velocity so that its facets sequentially inter-cept and reflect an input llght beam. To avoid unwanted vignetting of the reflected light beam, provision is conventional~y made for Dreventing the illu~
mination of the active scanning facet from varying as a function of the rotationof the scanning elementO To that end, some multi-faceted rotating polygon beam scanners are operated in a so-called overfilled mode in which two or more of the facets are simultaneously illuminated by the input beam. See, for example, U.S. Patent No. 3,995,110. While overEllled scanners have been used with substantial success, such as in the commercially available 9700 elec-tronic printing system of Xerox Corporation, they suffer from the disadvan-tage that a substantial part (i.e. 50% or more) of the available optical energy is wasted due to ~he inherent truncation of the input beam. Thus, others have ,. :
~ 3~
suggested that such scanners be operated in a fully filled mode or underfilled mode to avoid truncating the input beam. However, fully filled systems have tended to be relatively complex because they generally require facet tracking to maintain the input beam fully seated on the scanning facet while the reflected beam is being scanned through a desired scan angle. Underfilled systems, on the other hand, have traditionally been rather bulky and non-linear.See, for example, U.S. Patent Nos. 3,675,016 and 3,750,1~9.
SUMMARY OF THE INVENITON
In accordance with the presen~ invention, to provide a relatively compact and linear underfilled multi-faceted rotating polygon beam scanning system, there are imaging optics for sequentially bringing an input light beam to a tangentially exten&ng line-like focus on successive facets of a rotating polygonal scanning element and for restoring the light beam reflected from the facets to a more circular focus on an image plane to provide a generàlly cir-cular scanning spot. Each of the facets subtends a sufficient angle about the axis of rotation of the scanning element to ensure that the input beam remains fully seated on a single facet while the reflected bearn is being scanned through a desired scan angle. Furthermore, improved linearity is achieved because the scanning system is symmetrical in the tangential and sagittal planes at all points between the imaging optics and the scanning element.
More particularly, to perform a relatively linear wide angle scan over a flat field, the imaging optics comprise a spherical focusing lens and at least one cylinderical sagittal correction lens. The sperical lens is positionedbetween the scanning element and the cylinderical lens or lenses and is used in a symmetrical double pass mode to focus the input and reflected beams.
The curvature of the spherical lens is selected to compensate for the tendency of the scanning spot velocity to vary as a function of the field position. A
single cylinderical sagittal correction lens may be used in a symmetrical ~ -double pass mode for both input and reflected beams if the sagittal angular displacement between those beams is less than 5 or so. If the displacement ; ~ -angle substantially exceeds that limit, the cost of avoiding excessive aberrations while using a single cylinderical lens is likely to be prohibitive.
~hus, the preferred approach for systems involving a relatively large sagittal angular displacernent between the input and reflected beams is to provide separate, substantially identical and symmetrically positioned, cylinderical sagittal correction lenses for the input and reflected beams. At any rate,
-2-L3~7~
the cylinderical correction lens for the reflected beam ls selected to have a radius of curvature in the tangential plane which causes that lens to be substantially normal to ~`
the reflected beam in all field positions.
To compensate for radial runout variations in the polygonal scanning element, the input beam is preferably substantially collimated in the tangential plane while being applied thereto. For that reason, there advantageous-ly is a prefocusing lens for bringing the input beam to a 10 focus at a point which is displaced from the imaging optics by a distance selected to cause such collimation.
An aspect of the invention is as follows:
A flying spot optical scanning system for sweeping an optical scanning spot across an imaging surface, said 15 system comprising the combination of a source for supplying a light beam; a beam scanning element having a plurality of reflective facets circumferentially distributed in a tangen-tial plane about an axis of rotation; means for rotating said scanning element on said axis of rotation, whereby 20 said facets serially intexcept and reflect said light beam;
lens means optically interposed between said source and ;
said surface for serially focusing the light beam onto successive ones of said facets and for refocusing light reflected from said facets onto said surface; said lens 25 means including a cylinderical correction lens and a spherical lens which is positioned between said cylinderi-cal lens and said scanning element; said cylinderical lens and said spherical lens each being substantially sym-metrical about an optical axis which is essentially normal 30 to the axis of rotation of said scanning element; said cylinderical lens having substantial power in a sagittal plane and negligible power in a tangential plane; said light beam being applied to said cylindrical lens with a generally circular cross section; said cylinderical lens 35 and said spherical lens operating in a symmetrical double ,~-2a-s ~3~7~L
pass made to bring said light beam to a tangentially extend-ing line-like focus on successive ones of said facet and ~:
to restore the light reflected from said facets to a generally circular focus on said imaging surface, with :
S said light beam underfilling and remaining fully seated on ~ :
just one of said facets as said reflected light is scanned :
through a predetermined scan angle. :
:
~, :
: ::: :
:' ~ ~ ' ' -2b-~ .
, : : .
. ~' :
. ~ . ` '. . `
39~1 BREF DESCRIPTION OF THE DRAWINGS
Still other objects and advantages of the invention will become apparent when the following detailed description is read in conjunction with the aitached drawings, in which:
FIG. l is a schematic tangential plane view of an underfilled multi-faceted rotating polygonal beam scanning system which is constructed in accordance with the present invention;
FIG. 2 is a schematic sagittal plane view of the scanning system shown in FIG. l;
FIG. 3 is a schematic sagittal plane view of an alternative embo-diment of this invention.
DETAII ED DESCRIPTION OF T~E ILLUSTRAlED E~vIBODIMENTS
While the invention is described ln some detail hereinbelow with specific reference to cer-tain illustrated embodiments, it is to be understood that there is no desire to limit it to those embodiments. On the contrary, the intent is to cover all modifications, alternatives9 and equivalents falling within the spirit and scope of the invention as defined by the appended claims.
Turning now to the drawings, and at this point especially to FIGS. l and 2, there is an optical scanning system l0 comprising a laser or o~her suitable source ll for supplying an input light beam 12 which is applied to a multi-faceted polygonal beam scanning element 13 having a plurality of substantially identical reElective facets 14. In keeping with generally accepted prac-tices9 the facets 14 are essentially planar and are supported in ~39~
adjacent abutting relationship on the outer circumference of a regular polygon 15. Furthermore, a motor 16 has its output shaft 17 coupled to the polygon 15 for rotating the scanning element 13 a substantially constant angular velocity ~J in the direction of the arrow (FIG. 1). Thus, the facets 14 sequentially 5 intercept and reflect the input beam 12, thereby providing a reflected light beam 19 which is cyclically scanned through a predetermined scan angle Q
In accordance with this invention, there are imaging optics 21 for serially :Eocusing the input beam 12 on successive ones of the facets 14 andfor refocusing the reflected beam 19 on an image plane 22 to provide a scan-ning spot S. As shown, the input beam 12 is applied to the imaging optics 21 in alignment with the optical axis thereof in the tangential plane ~FI~.
1) and at a small predetermined angle,~with respect to that axis in the sagit-tal plane (FIG. 2). Hence, the optical paths for the input and reflected beams 12 and 19, respectively, are symmetrical in the tangential and sagittal planes about the optical axis of the imaging optics 21 at all points between the scanning element 13 and the imaging optics 21.
As is known, the polygonal scanning element 13 is theoretically capable of cyclically scanning the reflected light beam 19 through an angle, ~, which is given by: O
~ - 2 (360 ) (1) where N = the number of facetei 14 on the scanning element 13 In keeping with the practice used hereinbelow of referencing all angles of 25 interest to the optical axis of the imaging optics 21, the theoretical limït may be expressed in terms of a half angle as follows:
~p= + 360 2) Since the scanner 13 is operatin~ in an underfilled mode, the maximum permissible half scan angle aC can only approach the theoretical 30 limit `P/2. In o~her words, there is the overriding requirement that the -input beam 12 must remain fully seated on just one of the facets 14 ti.e., the active facet) while the reflected beam 19 is scanned through a desired scan angle. For that reason, the maximum permissible half scan angle~ is limited so that:
~3~
2r (tan ~ tan ~ ) (3) where A = the tangential width of the aperture illuminated by the fully seated input beam 12; and r = the radius of the scanning element 13 as measured perpendicularly to the facets 14~
Solving equation (3) for the maximum half scan angle ~< which is con-sistent with underfilled operation of the scanner 13 yields:
oC = 2 arctan (tan ~J - A ~ (4) max 4 2r Thus, the maximum permissible full field scan angle is:
2 ~ = 4 arctan (tan l~ - A~ (5) ~ `
max 4 2r It can be shown that the scanning system 10 provides a su~
stantially linear scan of the scanning spot S over a flat field of scan if the imaging optics 21 have a symmetrical negative distortion factor, di, which varies as a function of the instantaneous half field angle ~1 in accordance with the following relationship:
~ri (6) where ri = the instantaneous angle of the reflected beam 19 relative to the optical a cis of the imaging optics 21 in radians; ancl ~i ~ the instantaneous angle of the reflected beam 19 relative to the optical axis of the imaging optics 21 in degrees 30 h~ultiplying equation (4) by equation (6) and using the limiting case to determine the maximum actual half field scan angle, ~max' which can be realized while operating the scanning system 10 in an underfilled mode to achieve a substantially linear, flat field scan of the scanning spot S yields: :
~max =2d max arctarl (tan ~ - AJ (7) ~3~'7~
That, of course, means that ~he maximum actual full field scan angle is:
2 ~max = 4dmax arctan (tan 4 2r ~ (8) An example may add some perspective to the foregoing &scusslon. For purposes of this example, it will be assumed that the scan-5 ning system 10 is being used to cyclically scan the reflected beam 19 alongan 11" scan line on the image plane 22 and that the optical path length, D, for the reflected beam 19 (as measured on the optical axis, from the active facet 14 to the image plane 22) is 15". That means that an actual half scan angle max of the slightly over 20 is required. Referring to equation (6), 10 it will be seen that a maximum negative distortion factor dmaX of approxi-mately 0.95 radians/degree is needed to achieve a linear scan of the scan-ning spot S. Therefore~ the maximum permissible half scan angle~max need only be slightly greater than 21. If ~max is conservatively selected to be 22 and if the scanning element 13 is selected to have fourteen facets 14 and a radius r of 1.643", equation (3) can be solved to show that the tangential width A for the aperture illuminated by the fully seated input beam 12 must be less than about 0.100". Hence, a conse rvative specification would limit the tangential width A of the illuminated aperture to 0.110" as mea-sured with the illuminated aperture normal to the input beam 12. That 20 would provide a safety margin of about 10 percent to accomodate any minor variations in the tangential width A of the illuminated aperture as a function of -the rotation of the scanning element 13. In practice, the image plane 22 is typically advanced in a cross scan direction at a rate of, say, 10 inches/second relative to the scanning element 13. Hence if it is assumed 25 that a scanning density of 350 scan lines/inch is desired, the rotational rate required of the scanning element 13 would be 15,000 RPM. Clearly, the foregoing parameters are well within reasonable boundaries in view of the current state of the art.
Some scanning efficiency is necessarily sacrificed in the interest 30 of operating the scanning system 10 in an underfilled mode. As a general rule, however, there is only a minor reduction in scanning efficiency which is far outweighed by the advantages of the underfilled mode of operation. For instance, in the case of the above-described example, the scanning efficiency is:
E = Maximum permissible scan ang~e = 2o~max = 8S% (9) Theorehcal Limit _ ~ _ ~3~7~
Considering the imaging optics 21 in some additional detail, it will be seen that there are symmetrically positioned and optically matched lenses 41-43 for focusing the input beam 12 on the active facet 14 and for focusing the reflected beam 19 on the image plane 2~. More particularly, as 5 shown in FIGS~ 1 and 2, there is a cylinderical sagittal correction lens 41 and a spherical focusing lens 42 for bringing the input beam 12 to a tangentially extending line-like focus on the active facet 14. To restore the reflected beam 19 to a more circular focus on the image plane 22, there is the spherical lens 42 and another cylinderical sagittal correction lens 43. Accordingly, it will 10 be understood that the spherical lens 42 is used in a symmetrical double passmode to accomodate the input and reflected beams 12 and 19, respectively.
Of course, the number of elements required to form the spherical lens 42 is directly dependent on the size of the scan angle 0 which, in turn, is dependent on the ratio of the scan line length POQ to the output optical arm length D.
The cylinderical lenses 41 and 43, on the other hand, are optically matched to each other and are substantially identically positioned relative to the spherical lens 42 in the op~ical paths for the input beam 12 and the reflected beam 19, respectively.
To bring the input beam 12 to a tangentially extending line-like 20 focus and to restore the reflected beam 19 to a generally circular focus, thecylinderical correction lenses 41 and 43 have substantial power in the sagittal plane but little, if any, power in the tangential plane. Indeed, there preferably is a prefocusing lens 44 for initially focusing the input beam 12 at a point I
which is displaced from the active scanning facet 14 by a distance which is 25 approximately equal to the output optical arm length D. In other words, the prefocal point I for the input beam 12 is the conjugate to the midpoint O of the scan line POQ which is traced out on the image plane 22 by the reflected beam 19. As a result of the prefocusing, the input beam 12 is substantially collimated in the tangential plane as it leaves the last surface 46 of the 30 spherical lens 4~, whereby the size and shape of the scanning spot 5 are substan-tially unaffected by any minor radial runout variations in the scanning element 13.
Since the input beam 12 is brought to a tangen~ially extending line-like focus on successive ones of the facets 14, the size and shape of the scanning spot S are also substantially unaffected by any sagittal plane variations ~;~L4397i in the power of the facets 14. Power variations among the facets 14 in the tangential plane 14 will have some effect on the geometry of the scanning spot S, but not nearly so great an effect as in an overfilled system. More pointedly, returning for a moment to the foregoing example, it can be shown 5 that each facet 14 of the scanner 13 has a tangential length, L, of approxi-mately 0.75" if the scanner 13 has fourteen facets 14 and a radius r of 1.643"
as previously assumed. Thus, the tangential width A of the aperture illumi-nated by the input beam 12 (which was assumed to be about 0.100") is slightly less than 1/7 of the facet length L. If, it is now assumed that the total 10 power variation along each facet 14 is y4 ~ where )~ is the wavelength of theinput beam 12, the power variation within the illuminated aperture is approxi-mately~
Y~ 7.5 = 3~0 (10) That is about 1/12 the effect that the same facet power variation would have 15 in an overfilled system.
As will be appreuated, the cylinderical correction len 43 com-pensates for any slight tilt or wobble of the scanning element 13 and for any minor tilt angles or coning errors of the facets 14. In effect, the cylindericailens 43 bends the reflected beam 19 back toward a predetermined sagittal 20 projection plane should the reflected beam 19 tend to wonder therefrom.
Consequently, the sagittal position of the Eocus~ed reflected beam 19 remains substantially constant on the image plane 22. To provide precise sagittal correction, the optical axes of the cylinderical lenses 41 and 43 are equally but oppositely displaced from the optical axis of the imaging optics 21 by 25 the aforementioned sagittal plane projection angle~
As shown in FIG. 3, if the angular displacement between the input and output beams 12 and 19 (i.e., 2~) is less than 5 or so, the cylindri~cal lenses 41 and 43 may be replaced in favor of using a single cylindrical sagittal correction lens 51 in a symmetrical double pass mode to accomodate 30 both the inpu~ beam 12 and the reflected beam l9. If a single sagittal correc~
tion lens is used in scanners having larger displacement angles between the input and output beams, excessive optical aberrations are likely to occur.
In keeping with one of the important features of this invention, the cylindrical lens 43 and 51 have a bending radius ;n the tangential plane
the cylinderical correction lens for the reflected beam ls selected to have a radius of curvature in the tangential plane which causes that lens to be substantially normal to ~`
the reflected beam in all field positions.
To compensate for radial runout variations in the polygonal scanning element, the input beam is preferably substantially collimated in the tangential plane while being applied thereto. For that reason, there advantageous-ly is a prefocusing lens for bringing the input beam to a 10 focus at a point which is displaced from the imaging optics by a distance selected to cause such collimation.
An aspect of the invention is as follows:
A flying spot optical scanning system for sweeping an optical scanning spot across an imaging surface, said 15 system comprising the combination of a source for supplying a light beam; a beam scanning element having a plurality of reflective facets circumferentially distributed in a tangen-tial plane about an axis of rotation; means for rotating said scanning element on said axis of rotation, whereby 20 said facets serially intexcept and reflect said light beam;
lens means optically interposed between said source and ;
said surface for serially focusing the light beam onto successive ones of said facets and for refocusing light reflected from said facets onto said surface; said lens 25 means including a cylinderical correction lens and a spherical lens which is positioned between said cylinderi-cal lens and said scanning element; said cylinderical lens and said spherical lens each being substantially sym-metrical about an optical axis which is essentially normal 30 to the axis of rotation of said scanning element; said cylinderical lens having substantial power in a sagittal plane and negligible power in a tangential plane; said light beam being applied to said cylindrical lens with a generally circular cross section; said cylinderical lens 35 and said spherical lens operating in a symmetrical double ,~-2a-s ~3~7~L
pass made to bring said light beam to a tangentially extend-ing line-like focus on successive ones of said facet and ~:
to restore the light reflected from said facets to a generally circular focus on said imaging surface, with :
S said light beam underfilling and remaining fully seated on ~ :
just one of said facets as said reflected light is scanned :
through a predetermined scan angle. :
:
~, :
: ::: :
:' ~ ~ ' ' -2b-~ .
, : : .
. ~' :
. ~ . ` '. . `
39~1 BREF DESCRIPTION OF THE DRAWINGS
Still other objects and advantages of the invention will become apparent when the following detailed description is read in conjunction with the aitached drawings, in which:
FIG. l is a schematic tangential plane view of an underfilled multi-faceted rotating polygonal beam scanning system which is constructed in accordance with the present invention;
FIG. 2 is a schematic sagittal plane view of the scanning system shown in FIG. l;
FIG. 3 is a schematic sagittal plane view of an alternative embo-diment of this invention.
DETAII ED DESCRIPTION OF T~E ILLUSTRAlED E~vIBODIMENTS
While the invention is described ln some detail hereinbelow with specific reference to cer-tain illustrated embodiments, it is to be understood that there is no desire to limit it to those embodiments. On the contrary, the intent is to cover all modifications, alternatives9 and equivalents falling within the spirit and scope of the invention as defined by the appended claims.
Turning now to the drawings, and at this point especially to FIGS. l and 2, there is an optical scanning system l0 comprising a laser or o~her suitable source ll for supplying an input light beam 12 which is applied to a multi-faceted polygonal beam scanning element 13 having a plurality of substantially identical reElective facets 14. In keeping with generally accepted prac-tices9 the facets 14 are essentially planar and are supported in ~39~
adjacent abutting relationship on the outer circumference of a regular polygon 15. Furthermore, a motor 16 has its output shaft 17 coupled to the polygon 15 for rotating the scanning element 13 a substantially constant angular velocity ~J in the direction of the arrow (FIG. 1). Thus, the facets 14 sequentially 5 intercept and reflect the input beam 12, thereby providing a reflected light beam 19 which is cyclically scanned through a predetermined scan angle Q
In accordance with this invention, there are imaging optics 21 for serially :Eocusing the input beam 12 on successive ones of the facets 14 andfor refocusing the reflected beam 19 on an image plane 22 to provide a scan-ning spot S. As shown, the input beam 12 is applied to the imaging optics 21 in alignment with the optical axis thereof in the tangential plane ~FI~.
1) and at a small predetermined angle,~with respect to that axis in the sagit-tal plane (FIG. 2). Hence, the optical paths for the input and reflected beams 12 and 19, respectively, are symmetrical in the tangential and sagittal planes about the optical axis of the imaging optics 21 at all points between the scanning element 13 and the imaging optics 21.
As is known, the polygonal scanning element 13 is theoretically capable of cyclically scanning the reflected light beam 19 through an angle, ~, which is given by: O
~ - 2 (360 ) (1) where N = the number of facetei 14 on the scanning element 13 In keeping with the practice used hereinbelow of referencing all angles of 25 interest to the optical axis of the imaging optics 21, the theoretical limït may be expressed in terms of a half angle as follows:
~p= + 360 2) Since the scanner 13 is operatin~ in an underfilled mode, the maximum permissible half scan angle aC can only approach the theoretical 30 limit `P/2. In o~her words, there is the overriding requirement that the -input beam 12 must remain fully seated on just one of the facets 14 ti.e., the active facet) while the reflected beam 19 is scanned through a desired scan angle. For that reason, the maximum permissible half scan angle~ is limited so that:
~3~
2r (tan ~ tan ~ ) (3) where A = the tangential width of the aperture illuminated by the fully seated input beam 12; and r = the radius of the scanning element 13 as measured perpendicularly to the facets 14~
Solving equation (3) for the maximum half scan angle ~< which is con-sistent with underfilled operation of the scanner 13 yields:
oC = 2 arctan (tan ~J - A ~ (4) max 4 2r Thus, the maximum permissible full field scan angle is:
2 ~ = 4 arctan (tan l~ - A~ (5) ~ `
max 4 2r It can be shown that the scanning system 10 provides a su~
stantially linear scan of the scanning spot S over a flat field of scan if the imaging optics 21 have a symmetrical negative distortion factor, di, which varies as a function of the instantaneous half field angle ~1 in accordance with the following relationship:
~ri (6) where ri = the instantaneous angle of the reflected beam 19 relative to the optical a cis of the imaging optics 21 in radians; ancl ~i ~ the instantaneous angle of the reflected beam 19 relative to the optical axis of the imaging optics 21 in degrees 30 h~ultiplying equation (4) by equation (6) and using the limiting case to determine the maximum actual half field scan angle, ~max' which can be realized while operating the scanning system 10 in an underfilled mode to achieve a substantially linear, flat field scan of the scanning spot S yields: :
~max =2d max arctarl (tan ~ - AJ (7) ~3~'7~
That, of course, means that ~he maximum actual full field scan angle is:
2 ~max = 4dmax arctan (tan 4 2r ~ (8) An example may add some perspective to the foregoing &scusslon. For purposes of this example, it will be assumed that the scan-5 ning system 10 is being used to cyclically scan the reflected beam 19 alongan 11" scan line on the image plane 22 and that the optical path length, D, for the reflected beam 19 (as measured on the optical axis, from the active facet 14 to the image plane 22) is 15". That means that an actual half scan angle max of the slightly over 20 is required. Referring to equation (6), 10 it will be seen that a maximum negative distortion factor dmaX of approxi-mately 0.95 radians/degree is needed to achieve a linear scan of the scan-ning spot S. Therefore~ the maximum permissible half scan angle~max need only be slightly greater than 21. If ~max is conservatively selected to be 22 and if the scanning element 13 is selected to have fourteen facets 14 and a radius r of 1.643", equation (3) can be solved to show that the tangential width A for the aperture illuminated by the fully seated input beam 12 must be less than about 0.100". Hence, a conse rvative specification would limit the tangential width A of the illuminated aperture to 0.110" as mea-sured with the illuminated aperture normal to the input beam 12. That 20 would provide a safety margin of about 10 percent to accomodate any minor variations in the tangential width A of the illuminated aperture as a function of -the rotation of the scanning element 13. In practice, the image plane 22 is typically advanced in a cross scan direction at a rate of, say, 10 inches/second relative to the scanning element 13. Hence if it is assumed 25 that a scanning density of 350 scan lines/inch is desired, the rotational rate required of the scanning element 13 would be 15,000 RPM. Clearly, the foregoing parameters are well within reasonable boundaries in view of the current state of the art.
Some scanning efficiency is necessarily sacrificed in the interest 30 of operating the scanning system 10 in an underfilled mode. As a general rule, however, there is only a minor reduction in scanning efficiency which is far outweighed by the advantages of the underfilled mode of operation. For instance, in the case of the above-described example, the scanning efficiency is:
E = Maximum permissible scan ang~e = 2o~max = 8S% (9) Theorehcal Limit _ ~ _ ~3~7~
Considering the imaging optics 21 in some additional detail, it will be seen that there are symmetrically positioned and optically matched lenses 41-43 for focusing the input beam 12 on the active facet 14 and for focusing the reflected beam 19 on the image plane 2~. More particularly, as 5 shown in FIGS~ 1 and 2, there is a cylinderical sagittal correction lens 41 and a spherical focusing lens 42 for bringing the input beam 12 to a tangentially extending line-like focus on the active facet 14. To restore the reflected beam 19 to a more circular focus on the image plane 22, there is the spherical lens 42 and another cylinderical sagittal correction lens 43. Accordingly, it will 10 be understood that the spherical lens 42 is used in a symmetrical double passmode to accomodate the input and reflected beams 12 and 19, respectively.
Of course, the number of elements required to form the spherical lens 42 is directly dependent on the size of the scan angle 0 which, in turn, is dependent on the ratio of the scan line length POQ to the output optical arm length D.
The cylinderical lenses 41 and 43, on the other hand, are optically matched to each other and are substantially identically positioned relative to the spherical lens 42 in the op~ical paths for the input beam 12 and the reflected beam 19, respectively.
To bring the input beam 12 to a tangentially extending line-like 20 focus and to restore the reflected beam 19 to a generally circular focus, thecylinderical correction lenses 41 and 43 have substantial power in the sagittal plane but little, if any, power in the tangential plane. Indeed, there preferably is a prefocusing lens 44 for initially focusing the input beam 12 at a point I
which is displaced from the active scanning facet 14 by a distance which is 25 approximately equal to the output optical arm length D. In other words, the prefocal point I for the input beam 12 is the conjugate to the midpoint O of the scan line POQ which is traced out on the image plane 22 by the reflected beam 19. As a result of the prefocusing, the input beam 12 is substantially collimated in the tangential plane as it leaves the last surface 46 of the 30 spherical lens 4~, whereby the size and shape of the scanning spot 5 are substan-tially unaffected by any minor radial runout variations in the scanning element 13.
Since the input beam 12 is brought to a tangen~ially extending line-like focus on successive ones of the facets 14, the size and shape of the scanning spot S are also substantially unaffected by any sagittal plane variations ~;~L4397i in the power of the facets 14. Power variations among the facets 14 in the tangential plane 14 will have some effect on the geometry of the scanning spot S, but not nearly so great an effect as in an overfilled system. More pointedly, returning for a moment to the foregoing example, it can be shown 5 that each facet 14 of the scanner 13 has a tangential length, L, of approxi-mately 0.75" if the scanner 13 has fourteen facets 14 and a radius r of 1.643"
as previously assumed. Thus, the tangential width A of the aperture illumi-nated by the input beam 12 (which was assumed to be about 0.100") is slightly less than 1/7 of the facet length L. If, it is now assumed that the total 10 power variation along each facet 14 is y4 ~ where )~ is the wavelength of theinput beam 12, the power variation within the illuminated aperture is approxi-mately~
Y~ 7.5 = 3~0 (10) That is about 1/12 the effect that the same facet power variation would have 15 in an overfilled system.
As will be appreuated, the cylinderical correction len 43 com-pensates for any slight tilt or wobble of the scanning element 13 and for any minor tilt angles or coning errors of the facets 14. In effect, the cylindericailens 43 bends the reflected beam 19 back toward a predetermined sagittal 20 projection plane should the reflected beam 19 tend to wonder therefrom.
Consequently, the sagittal position of the Eocus~ed reflected beam 19 remains substantially constant on the image plane 22. To provide precise sagittal correction, the optical axes of the cylinderical lenses 41 and 43 are equally but oppositely displaced from the optical axis of the imaging optics 21 by 25 the aforementioned sagittal plane projection angle~
As shown in FIG. 3, if the angular displacement between the input and output beams 12 and 19 (i.e., 2~) is less than 5 or so, the cylindri~cal lenses 41 and 43 may be replaced in favor of using a single cylindrical sagittal correction lens 51 in a symmetrical double pass mode to accomodate 30 both the inpu~ beam 12 and the reflected beam l9. If a single sagittal correc~
tion lens is used in scanners having larger displacement angles between the input and output beams, excessive optical aberrations are likely to occur.
In keeping with one of the important features of this invention, the cylindrical lens 43 and 51 have a bending radius ;n the tangential plane
3~7~ :
which is selected to maintain the reflected heam 19 in focus over a flat field of scan POQ on the image plane 22. Consequently9 the reflected beam 19 is more or less normal to the cylindrical lenses 43 and 51 in all field positions Ql.
Furthermore, in accordance with another important aspect of this invention, the tangential position, Xi, of the scanning spot S is controlled as a function of the field angle ~1 so that a substantially linear, flat field scan of the scanning spo~ S is achieved. For a flat field of scan, the uncontrolled tangential position, X'i, of the scanning spot S is given by:
X'i = D tan ~ (Il) In contrast, for a linear scan of the scanning spot S, the scanning system must obey the equation:
Xi = D ri 12) Therefore, the spherical lens 42 and the cylinderical lens 43 or 51 are selectedto provide a net symmetrical non-linear negative distortion factor which is given by: g di = tan ~i (13) The resolving power or resolution capability of the scanning system 10, is a function of the size of the scanning spot S.
Spot size is defined by the expression~
Spot size = k 1 F# (14) where k = a constant which is dependent on whether the scanning system 10 is diffraction limited or not;
= 1 the output wavelength of light source ll; and F# = the F/Number of the scanning system 10 ;~
The constant, k, is minimized if the scanning system 10 is diffraction limited.
Indeed, the theoretical untruncated diffraction limited value of k is 1.27, although conservation optical design practices suggest that a more realistic value for a diffraction limited system having normal optical abberations, such 35 as may be caused by fabrication and assembly errors, is k = 1.60 or so. Of course~ the scanning system 10 is diffraction limited only if the F# is selectedso that the input beam 12 and the reflected beam 19 are untruncated. Thus, it should be noted that when the prefocussing lens 44 is used, the F# of the scanmng system 10 is defined in both meridians (i.e., for the input beam 12 and the reflec^ ;~
ted beam 19) by the expression:
f~ 9-;
:
., .
' ' ~ ~', ' ':
9L3~
F# = T (15) where a = the cone diameter of the beams 12 or 19 as rneasured at the first surface 45 of the imaging optics 21; and T = the distance from the surface ~5 to the image plane 22, as measured along the optical axis of the imaging optics As will be appreciated, the cone diameter a and, therefore, the F#
may be controlled by increasing or decreasing the output focal length 15 of the prefocussing lens 44 while adjusting its position relative to the laser ll so th~t ~he input beam 12 remains prefocussed at point I. Sophis-ticated optical design techniques might enable the scanning system 10 to be diffraction limited at a F~ as low as F/20. However, straightforward optical design practices may be used to provide for diffraction limited 20 operation down to F/50 or so, which is more than adequate for most prac-tical applications.
CONCl~USION
In view of the foregoing, it will now be evident that the present invention provides a compact and optically efficient scanning sys-25 tem which is capable of providing a substantially linear, flat field scan ofa scanning spot. The scanning system is capable of providing a relatiyely wide scan angle. Indeed, the ration of the scan line length POQ tQ the output optical armlength D may be greater than one. Additionally, it will be under-stood that provision is made in the scanning system of this invention to 30 minimize variations in the size of the scanning spot. Furthermore, the scan-ning system may easily be diffraction limited a$ almost any F# needed for practical applications, thereby minimizing the size of the scanning spot in the interes~ of maximizing the available optical resolution.
~, 39~
Preferably, the scanning system of this invention is symmetri-cally implemented. However, it will be evident ttlat certain aspects of the invention are not dependent on the symmetry. For example, the concept of using a single spherical lens in a double pass mode can be applied to both 5 symmetrical and asymmetrical multifacted rotating polygon beam scanning systems and to scanning systems which use a rotating monogon or an oscilla-ting mirror for beam scanning purposes.
which is selected to maintain the reflected heam 19 in focus over a flat field of scan POQ on the image plane 22. Consequently9 the reflected beam 19 is more or less normal to the cylindrical lenses 43 and 51 in all field positions Ql.
Furthermore, in accordance with another important aspect of this invention, the tangential position, Xi, of the scanning spot S is controlled as a function of the field angle ~1 so that a substantially linear, flat field scan of the scanning spo~ S is achieved. For a flat field of scan, the uncontrolled tangential position, X'i, of the scanning spot S is given by:
X'i = D tan ~ (Il) In contrast, for a linear scan of the scanning spot S, the scanning system must obey the equation:
Xi = D ri 12) Therefore, the spherical lens 42 and the cylinderical lens 43 or 51 are selectedto provide a net symmetrical non-linear negative distortion factor which is given by: g di = tan ~i (13) The resolving power or resolution capability of the scanning system 10, is a function of the size of the scanning spot S.
Spot size is defined by the expression~
Spot size = k 1 F# (14) where k = a constant which is dependent on whether the scanning system 10 is diffraction limited or not;
= 1 the output wavelength of light source ll; and F# = the F/Number of the scanning system 10 ;~
The constant, k, is minimized if the scanning system 10 is diffraction limited.
Indeed, the theoretical untruncated diffraction limited value of k is 1.27, although conservation optical design practices suggest that a more realistic value for a diffraction limited system having normal optical abberations, such 35 as may be caused by fabrication and assembly errors, is k = 1.60 or so. Of course~ the scanning system 10 is diffraction limited only if the F# is selectedso that the input beam 12 and the reflected beam 19 are untruncated. Thus, it should be noted that when the prefocussing lens 44 is used, the F# of the scanmng system 10 is defined in both meridians (i.e., for the input beam 12 and the reflec^ ;~
ted beam 19) by the expression:
f~ 9-;
:
., .
' ' ~ ~', ' ':
9L3~
F# = T (15) where a = the cone diameter of the beams 12 or 19 as rneasured at the first surface 45 of the imaging optics 21; and T = the distance from the surface ~5 to the image plane 22, as measured along the optical axis of the imaging optics As will be appreciated, the cone diameter a and, therefore, the F#
may be controlled by increasing or decreasing the output focal length 15 of the prefocussing lens 44 while adjusting its position relative to the laser ll so th~t ~he input beam 12 remains prefocussed at point I. Sophis-ticated optical design techniques might enable the scanning system 10 to be diffraction limited at a F~ as low as F/20. However, straightforward optical design practices may be used to provide for diffraction limited 20 operation down to F/50 or so, which is more than adequate for most prac-tical applications.
CONCl~USION
In view of the foregoing, it will now be evident that the present invention provides a compact and optically efficient scanning sys-25 tem which is capable of providing a substantially linear, flat field scan ofa scanning spot. The scanning system is capable of providing a relatiyely wide scan angle. Indeed, the ration of the scan line length POQ tQ the output optical armlength D may be greater than one. Additionally, it will be under-stood that provision is made in the scanning system of this invention to 30 minimize variations in the size of the scanning spot. Furthermore, the scan-ning system may easily be diffraction limited a$ almost any F# needed for practical applications, thereby minimizing the size of the scanning spot in the interes~ of maximizing the available optical resolution.
~, 39~
Preferably, the scanning system of this invention is symmetri-cally implemented. However, it will be evident ttlat certain aspects of the invention are not dependent on the symmetry. For example, the concept of using a single spherical lens in a double pass mode can be applied to both 5 symmetrical and asymmetrical multifacted rotating polygon beam scanning systems and to scanning systems which use a rotating monogon or an oscilla-ting mirror for beam scanning purposes.
Claims (4)
1. A flying spot optical scanning system for sweeping an optical scanning spot across an imaging surface, said system comprising the combination of a source for supplying a light beam; a beam scanning element having a plurality of reflective facets circumferentially distributed in a tangen-tial plane about an axis of rotation; means for rotating said scanning element on said axis of rotation, whereby said facets serially intercept and reflect said light beam;
lens means optically interposed between said source and said surface for serially focusing the light beam onto successive ones of said facets and for refocusing light reflected from said facets onto said surface; said lens means including a cylinderical correction lens and a spherical lens which is positioned between said cylinderi-cal lens and said scanning element; said cylinderical lens and said spherical lens each being substantially sym-metrical about an optical axis which is essentially normal to the axis of rotation of said scanning element; said cylinderical lens having substantial power in a sagittal plane and negligible power in a tangential plane; said light beam being applied to said cylindrical lens with a generally circular cross section; said cylinderical lens and said spherical lens operating in a symmetrical double pass made to bring said light beam to a tangentially extend-ing line-like focus on successive ones of said facet and to restore the light reflected from said facets to a generally circular focus on said imaging surface, with said light beam underfilling and remaining fully seated on just one of said facets as said reflected light is scanned through a predetermined scan angle.
lens means optically interposed between said source and said surface for serially focusing the light beam onto successive ones of said facets and for refocusing light reflected from said facets onto said surface; said lens means including a cylinderical correction lens and a spherical lens which is positioned between said cylinderi-cal lens and said scanning element; said cylinderical lens and said spherical lens each being substantially sym-metrical about an optical axis which is essentially normal to the axis of rotation of said scanning element; said cylinderical lens having substantial power in a sagittal plane and negligible power in a tangential plane; said light beam being applied to said cylindrical lens with a generally circular cross section; said cylinderical lens and said spherical lens operating in a symmetrical double pass made to bring said light beam to a tangentially extend-ing line-like focus on successive ones of said facet and to restore the light reflected from said facets to a generally circular focus on said imaging surface, with said light beam underfilling and remaining fully seated on just one of said facets as said reflected light is scanned through a predetermined scan angle.
2. The flying spot scanning system of Claim 1 further including a prefocusing lens optically aligned between said source and said cylindrical lens for bringing said light beam to a focus at a point selected to cause said light beam to be substantially collimated in said tangential plane while being applied to said facets, thereby compensating for radial runout variations of said scanning element.
3. The flying spot scanning system of Claim 2 whereas said lens means additionally comprises a pair of substantially iden-tical cylinderical sagittal correction lenses and a spherical lens, said spherical lens being positioned between said cylinderical lenses and said scanning element and being sub-stantially symmetrical about an optical axis which is essen-tially normal to the axis of rotation of said scanning ele-ment; said cylinderical lenses being approximately equi-distantly spaced from and said spherical lens and being substantially symmetrically positioned in a sagittal plane on opposite sides of said optical axis; each of said cylinderical lenses having substantial power in a sagittal plane and negligible power in a tangential plane, said light beam being applied to one of said cylinderical lenses with a generally circular cross section; said one cylinderical lens and said spherical lens cooperating to bring said light beam to a tangentially extending line-like focus on successive ones of said facet and the other of said cylinder-ical lenses and said spherical lens cooperating to restore the light reflected from said facets to a generally circular focus on said imaging surface, with said light beam under-filling and remaining fully seated on just one of said facets as said reflected light is scanned through a predeter-mined scan angle.
4. The flying spot scanning system of claim 3 further including a prefocusing lens optically aligned between said source and said one cylinderical lens for bringing said light beam to a focus at a point selected to cause said light beam to be substantially collimated in said tangential plane while being applied to said facets, thereby compensating for radial runout variations of said scanning element.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/088,804 US4274703A (en) | 1977-08-01 | 1979-10-29 | High-efficiency symmetrical scanning optics |
| US088,804 | 1979-10-29 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1143971A true CA1143971A (en) | 1983-04-05 |
Family
ID=22213586
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000360909A Expired CA1143971A (en) | 1979-10-29 | 1980-09-24 | High efficiency symmetrical scanning optics |
Country Status (5)
| Country | Link |
|---|---|
| US (1) | US4274703A (en) |
| EP (1) | EP0028160B1 (en) |
| JP (1) | JPS5667816A (en) |
| CA (1) | CA1143971A (en) |
| DE (1) | DE3065311D1 (en) |
Families Citing this family (32)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4397521A (en) * | 1980-09-29 | 1983-08-09 | Xerox Corporation | Double pass optical system for raster scanners |
| US4355860A (en) * | 1980-09-29 | 1982-10-26 | Xerox Corporation | Double pass scanning system |
| WO1982002955A1 (en) * | 1981-02-23 | 1982-09-02 | Gen Optronics Corp | Improved diffraction grating scanner with anamorphic correction of scan curvatures |
| US4753503A (en) * | 1981-02-25 | 1988-06-28 | Benson, Incorporated | Laser scanning system |
| US4374617A (en) * | 1981-08-05 | 1983-02-22 | Xerox Corporation | Multi-function document processor |
| US4537465A (en) * | 1981-11-12 | 1985-08-27 | Lincoln Laser Company | Apparatus with two input beams for generating optical scans |
| US4509819A (en) * | 1981-11-12 | 1985-04-09 | Lincoln Laser Company | Optical beam pulse generator |
| GB2128765B (en) * | 1982-10-16 | 1986-07-16 | Ferranti Plc | Scanning measurement system with a convecting element |
| US4832429A (en) * | 1983-01-19 | 1989-05-23 | T. R. Whitney Corporation | Scanning imaging system and method |
| SE456194B (en) * | 1983-01-31 | 1988-09-12 | Semyre Electronics Ab | AVSOKNINGSANORDNING |
| DE3404407C1 (en) * | 1984-02-08 | 1985-08-22 | Mergenthaler Linotype Gmbh, 6236 Eschborn | Optical-mechanical deflector |
| JPH0672981B2 (en) * | 1985-07-31 | 1994-09-14 | 株式会社リコー | Optical beam scanning optical system |
| US4630130A (en) * | 1985-10-21 | 1986-12-16 | Xerox Corporation | Scanning system for controlling stray beams caused by undesirable optical reflections |
| JPH0627902B2 (en) * | 1986-08-29 | 1994-04-13 | 富士ゼロックス株式会社 | Laser scanning optical system |
| JPS63136017A (en) * | 1986-11-28 | 1988-06-08 | Fujitsu Ltd | Light beam scanning device |
| US4796962A (en) * | 1987-03-23 | 1989-01-10 | Eastman Kodak Company | Optical scanner |
| JP2613600B2 (en) * | 1987-09-22 | 1997-05-28 | 株式会社日立製作所 | High resolution light beam scanner |
| US4921320A (en) * | 1988-09-22 | 1990-05-01 | Eastman Kodak Company | Optical scanner |
| US5194982A (en) * | 1989-03-17 | 1993-03-16 | Asahi Kogaku Kogyo Kabushiki Kaisha | Scanning optical system |
| US4960312A (en) * | 1989-10-10 | 1990-10-02 | Mahmoud Razzaghi | Compact high resolution high speed symmetrical scanning optics using multiple deflections |
| US5247383A (en) * | 1990-03-20 | 1993-09-21 | Olive Tree Technology, Inc. | Scanner with a post facet lens system |
| US5196957A (en) * | 1990-03-20 | 1993-03-23 | Olive Tree Technology, Inc. | Laser scanner with post-facet lens system |
| US5177632A (en) * | 1991-04-04 | 1993-01-05 | Nira Schwartz | Tracking system using a polygon of unique dimension or arbitrary polygon combined with sensors |
| US5278691A (en) * | 1992-06-24 | 1994-01-11 | Eastman Kodak Company | Symmetrical overfilled polygon laser scanner |
| US5387926A (en) * | 1992-06-30 | 1995-02-07 | California Institute Of Technology | High speed digital framing camera |
| KR960701560A (en) * | 1993-02-03 | 1996-02-24 | 프랑크 씨. 지뷰 | METHODS AND APPARATUS FOR IMAGE PROJECTION |
| JPH06337366A (en) * | 1993-05-21 | 1994-12-06 | Xerox Corp | Exposure device for raster output scanner in electrophotography printer |
| JPH07199104A (en) * | 1993-12-28 | 1995-08-04 | Fuji Xerox Co Ltd | Laser optical system device |
| US6575964B1 (en) | 1998-02-03 | 2003-06-10 | Sciton, Inc. | Selective aperture for laser delivery system for providing incision, tissue ablation and coagulation |
| US6014272A (en) * | 1998-05-22 | 2000-01-11 | Eastman Kodak Company | Retroreflective lens |
| US6743221B1 (en) * | 2001-03-13 | 2004-06-01 | James L. Hobart | Laser system and method for treatment of biological tissues |
| US6770069B1 (en) | 2001-06-22 | 2004-08-03 | Sciton, Inc. | Laser applicator |
Family Cites Families (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3675016A (en) * | 1970-02-17 | 1972-07-04 | Eastman Kodak Co | Flying spot scanning |
| JPS4898844A (en) * | 1972-03-29 | 1973-12-14 | ||
| US3853406A (en) * | 1973-06-08 | 1974-12-10 | Zygo Corp | Differential optical noncontacting diameter gauge utilizing a pair of linearly scanning light beams sequentially scanning the test piece |
| JPS5815769B2 (en) * | 1974-09-11 | 1983-03-28 | キヤノン株式会社 | Sousakou Gakkei |
| US3961838A (en) * | 1975-01-10 | 1976-06-08 | Zygo Corporation | Apparatus for producing a scanning laser beam of constant linear velocity |
| JPS5820403B2 (en) * | 1975-01-31 | 1983-04-22 | 富士写真フイルム株式会社 | Kaitentamenkiyouno Heikoudono Gosao Jiyokiyosuruhouhou |
| JPS588B2 (en) * | 1975-10-15 | 1983-01-05 | 富士写真フイルム株式会社 | Hikari Bee Mususasouchi |
| DE2550814C3 (en) * | 1975-11-12 | 1979-08-09 | Erwin Sick Gmbh Optik-Elektronik, 7808 Waldkirch | Line scanning device for material webs to detect defects |
| US4056307A (en) * | 1976-10-29 | 1977-11-01 | The Perkin-Elmer Corporation | Anamorphic scanner lens system |
| JPS54126051A (en) * | 1978-03-23 | 1979-09-29 | Ricoh Co Ltd | Anamorphic f lens system |
-
1979
- 1979-10-29 US US06/088,804 patent/US4274703A/en not_active Expired - Lifetime
-
1980
- 1980-09-24 CA CA000360909A patent/CA1143971A/en not_active Expired
- 1980-10-20 JP JP14676880A patent/JPS5667816A/en active Pending
- 1980-10-29 DE DE8080303840T patent/DE3065311D1/en not_active Expired
- 1980-10-29 EP EP80303840A patent/EP0028160B1/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| EP0028160A1 (en) | 1981-05-06 |
| JPS5667816A (en) | 1981-06-08 |
| US4274703A (en) | 1981-06-23 |
| EP0028160B1 (en) | 1983-10-12 |
| DE3065311D1 (en) | 1983-11-17 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CA1143971A (en) | High efficiency symmetrical scanning optics | |
| EP0016630B1 (en) | Optical scanning apparatus | |
| US5111325A (en) | F-θ lens | |
| CA1087006A (en) | Optical system for rotating mirror line scanning apparatus | |
| US4904034A (en) | Scanning apparatus | |
| US3984171A (en) | Linear scan system | |
| JPS61196222A (en) | Polyhedron scanner | |
| JPH0456962B2 (en) | ||
| US5550668A (en) | Multispot polygon ROS with maximized line separation depth of focus | |
| US5220449A (en) | Light beam scanning optical system | |
| US4984858A (en) | Light beam scanning optical system | |
| US4805974A (en) | Polycone™ scanning system with multiple beams | |
| US4230394A (en) | Mirror facet tracker using spherical mirrors | |
| US5365364A (en) | Optical scanner and printer | |
| WO1982002955A1 (en) | Improved diffraction grating scanner with anamorphic correction of scan curvatures | |
| EP0523320B1 (en) | Optical unit for use in laser beam printer apparatus | |
| EP0637770B1 (en) | Compact ROS imaging system | |
| JPH0644108B2 (en) | A shake correction device that does not cause a bow due to two reflections on one surface | |
| JP3219159B2 (en) | Scanning device | |
| JPH07174996A (en) | Raster-output-scanner image system | |
| JPH1062683A (en) | Achromatic telecentric f-theta scanning lens optical system | |
| JPH01200221A (en) | Light beam scanning optical system | |
| JPS628015Y2 (en) | ||
| JP2757308B2 (en) | Light beam scanning optical device | |
| JPS628016Y2 (en) |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |