US3737660A

US3737660A - Apparatus for taking tomograms of parabolically curved objects

Info

Publication number: US3737660A
Application number: US00078666A
Authority: US
Inventors: S Ando; S Yoshioka
Original assignee: MIDA ELECTRONIC APPARATUS IND
Current assignee: MIDA ELECTRONIC APPARATUS IND
Priority date: 1969-10-09
Filing date: 1970-10-07
Publication date: 1973-06-05
Anticipated expiration: 1990-06-05

Abstract

For taking tomograms of parabolically curved objects such as the dentition, jawbones and other bony structures of the head and dento-facial region, there are provided an X-ray tube and a radiographic film holder at both ends of a turnable arm. This arm is furnished with a plurality of shafts alternately serving as a pivot therefore, in such a manner that the X-ray tube supported at one end of the arm turns round a parabolically curved object at an unvarying distance therefrom, while radiating X-rays which traverse the object to impinge upon the radiographic film carried by the aforesaid holder turning in coordination with the turn of the arm. There are also disclosed herein a device for holding the head of a patient, a device for minute adjustment of ear-rods and the like for use in positioning the head, and a device for modification of the image density of X-rays traversing the head in readily penetrable directions.

Description

United States Patent 1 1 1111 3,737,660

Ando et al. 14 1 jam 5, 31973 54 APPARATUS FOR TAKING 3,514,606 5 1970 Rabey 1. ..250/65 R TOMOGRAMS 0 PARABOLIC ALLY 2,630,536 3/1953 Vladeff ..250/65 R CURVED OBJECTS [75] Inventors: Shoichi Ando, Shibuya-ku, Tokyoto; Shinji Yoshioka, Ichikawa-shi, both of Japan Assignee: Hida Denki Kogyo Kabushiki Kaisha, a/k/a Mida Electronic Apparatus Industrial Co., Ltd., Tokyo, Japan; a part interest Filed: Oct. 7, 1970 App]. No.: 78,666

[30] Foreign Application Priority Data Feb. 19,1970 Japan ..45/16790 Dec. 12, 1969 Japan ..44/118085 Dec. 1, 1969 Japan ..44/114226 Oct. 9, 1969 Japan ..44/80982 [52] U.S. Cl ..250/50, 250/61.5, 250/65 R [51] Int. Cl. ..G03b 41/16 [58] Field of Search ..250/65 R, 50, 61.5

[56] References Cited UNITED STATES PATENTS 3,536,913 10/1970 Huchel ..250/65 R Primary Examiner-James W. Lawrence Assistant ExaminerC. E. Church Attorney-Waters, Roditi, Schwartz & Nissen [57] ABSTRACT For taking tomograms of parabolically curved objects such as the dentition, jawbones and other bony structures of the head and dento-facial region, there are provided an X-ray tube and a radiographic film holder at both ends of a turnable arm. This arm is furnished with a plurality of shafts alternately serving as a pivot therefore, in such a manner that the X-ray tube supported at one end of the arm turns round a parabolically curved object at an unvarying distance therefrom, while radiating X-rays which traverse the object to impinge upon the radiographic film carried by the aforesaid holder turning in coordination with the turn of the arm. There are also disclosed herein a device for holding the head of a patient, a device for minute adjustment of ear-rods and the like for use in positioning the head, and a device for modification of the image density of X-rays traversing the head in readily penetrable directions.

6 Claims, 15 Drawing Figures PATENIEBJ'JH 5 191a SHEET E OF 6 FIGS APPARATUS FOR TAKING TOMOGRAMS OF PARABOLICALLY CURVED OBJECTS BACKGROUND OF THE INVENTION This invention relates generally to tomography, and in particular to a novel apparatus capable of taking tomograms of objects in the shape of an approximately parabolic curve such as a panoramic view, especially, the dentition, jawbones and other parts of the face and head. The invention also relates to some improvements designed to add to the utility of the above apparatus.

There has long been awaited by roentgenologists and related specialists the advent of apparatus capable of taking curved surface tomograms of the dentition, jawbones, etc., of the face and head. Many attempts made conventionally at the provision of such apparatus have been frustrated, in nearly all cases, due to the fact that those bony structures in the human face and head represent a parabolic curve consisting of two or more arcs of different curvatures.

Another difficulty resides in the correct adjustment and holding of the head at a position of the greatest convenience for tomographic examination. It has also been considered no less difficult to appropriately modify the unsubdued image density of X-rays radiated through the head in its readily penetrable directions. These intense X-rays will cause unevenness in the tone of a radiographic film exposed thereto.

Hence, no satisfactory tomograms of the dentition, jawbones and other desired objects in the face and head have so far been obtainable.

SUMMARY OF THE INVENTION It is accordingly a primary object of the present invention to provide a novel apparatus capable of taking clear and well-defined panoramic tomograms of tbe dentition, jawbones and other parabolically curved objects.

Another important object of the invention is to provide a device for holding the head of a patient at a minutely adjusted and visually confirmed position of the greatest convenience for its tomographic examination.

Still another important object of the invention is to provide a device capable of preventing, as far as feasible, the unevenness in the density of a radiographic film produced by undesired changes in the intensity of X- rays depending upon the arrangement of bony structures or air cavities present in the head.

With these objects in view and the other objects hereinafter set forth, the invention will now be described in detail with connection to the accompanying drawings showing several preferred embodiments thereof, in which like reference characters indicate like parts.

BRIEF DESCRIPTION OF THE DRAWINGS of the operating principles of the apparatus in accordance with the present invention;

FIGS. 3, 4 and 5 are similar diagrams in which the FIG. 6 is a top view of a device for turning an X-ray tube and a radiographic film holder of the apparatus of the invention along a parabolically curved object, the X-ray tube and the radiographic film holder being in positions shown in FIG. 2;

FIG. 7 is a vertical sectional view of the device of FIG. 6;

FIG. 8 is a top view of the device of FIG. 6, with the X-ray tube and the radiographic film holder in positions shown in FIG. 4;

FIG. 9 also is a top view of the device of FIG. 6, with the X-ray tube and the radiographic film holder in positions intermediate between those shown in FIGS. 3 and FIG. 10 is a front elevational view of a head holding device in the apparatus of the invention;

FIG. 11 is a side elevational view of the head holding device of FIG. 10;

FIG. 12 is a top view of the head holding device of FIG. 10;

FIG. 13 is a perspective view of a device for adjustment of ear-rods for use in holding the head of an individual to be tomographically examined by the apparatus of the invention;

FIG. 14 is a sectional view of one of the ear-rods shown in FIG. 13; and

FIG. 15 is a top view showing the arrangement of filter means adapted to modify the intensity of X-rays traversing the head in readily penetrable directions.

DETAILED DESCRIPTION OF THE INVENTION It will redound to the full appreciation of the present apparatus to clarify the concepts supporting it. So, first of all, description is given on how a tomogram of a parabolically curved object with two or more arcs of different curvatures can be taken with reference to FIGS. 1 through 5.

A parabolic curve 3 shown in perspective in FIG. 1 represents the dentition, jawbones and other objects in the head of an individual, and said parabolic curve 3 is indicated by broken lines in FIGS. 2 through 5. Let it be assumed that the parabolic curve 3 consists of an arc A2-A3 having its center at a point 7 and a radius of r2, an arc A3-A4 having its center at a point 6 and a radius of r1, and an arc A1-A2 having its center at a point 8 and a radius r1.

Now, referring to FIG. 2, an arm 42 is disposed as illustrated which has an X-ray tube 1 at one end and at the other end a screen 5 having a slit 4 therethrough in order to permit the passage of a beam of the X-rays emitted from a slitted opening of the X-ray tube 1. Inside the screen 5 there is provided a radiographic film holder 2 so as to be turnable in the arrow marked direction al in coordination with the turn of the arm 42 in the arrow marked direction a2. Hence, a tomogram of the arc Al-A2 can be taken as the arm 42 turns on its pivot 8 in the clockwise direction a2 to a position shown in FIG. 3 while the radiographic film holder 2 also turns in the clockwise direction al in coordination therewith. Then, with the arm 42 at the position shown in FIG. 3, another pivot of the arm 42located at a point x which is at a distance (r1 r2) from the center 8 of the arc Al-A2 is adjusted at the center 7 of the arc A2-A3, a tomogram of which is obtainable by turning the arm 42 on the above adjusted pivot 7 to the position given in FIG. 4. At this position, the first mentioned pivot of the arm 42 which was located at the center 8 in FIG. 3 is now brought to the center 6 of the arc A3-A4, so that a tomogram of this are A3-A4 can be taken by turning the arm 42 on this same pivot at 6 to the position of FIG.5 while also turning the film holder 2 in the same clockwise direction.

In this manner, a series of tomograms of the parabolic curve 3 consisting of the arcs Al-A2, A2-A3 and A3A4 can be taken by turning the arm 42 pivoted at the successive ones of the

centers

8, 7 and 6 of those arcs. Described in the following, with reference to FIGS. 6 through 9, is a device for so turning the arm 42, as adapted for materialization of the foregoing fundamental concepts of the present invention.

As seen in the drawings, the arm 42 is turnably supported on a disk 43 by means of self-aligning ball bearings 43a and is provided with two vertical shafts 8a and xa at positions corresponding to the center 8 of the arc A1-A2 and the point x of FIG. 2. Further, at the midpart of the disk 43, there is provided a hole 44 therethrough, so shaped as to consist of three arcs drawn round the

aforesaid centers

6, 7 and 8 of the arcs A3-A4, A2-A3 and Al-A2. A means 45 (for example, a spring) is provided whereby either one of the vertical shafts 8a and xa is temporarily secured to the disk 43 as desired. Roller or ball bearings 46 are provided at the lower ends of the vertical shafts 8a and xa so as to be in internal comtact with the hole 44. At one end of the arm 42 there is provided an X-ray tube 1 having a slit Ia through which X-rays are emitted, while at the other end there is provided a screen having a corresponding slit 4 through which the X-rays are admitted to a film holder 2 supported by the screen 5 so as to be turnable in coordination with the turn of the arm 42.v The desired turn of the arm 42 is obtained by means of a motor M installed upon a motor base 48 slidable in accordance with the turn of the arm 42 along a guide 47 upon the arm 42. The rotation of the motor M is conveyed, via bevel gears G2 and G3 and a shaft 49, to a pinion G4 which is in mesh with a ring gear G1. The shaft 49 is provided with a roller 50 which is rotatable in internal contact with the ring gear G1, while a shaft 51 secured to the motor base 48 is provided with a roller 52 which is rotatable in external contact with the same ring gear G1, so that these

rollers

50 and 52 sandwich the ring gear G1 there-between. Accordingly, even though the arm 42 will turn on either one of its pivots located at the

points

6, 7 and 8 that are off the center of the ring gear G1, the motor M slides by the turn of the arm 42 to such a position that the ring gear G1 is kept in constant mesh with the pinion G4.

To explain the operations of the above described device of the invention, the vertical shaft 80 of the arm 42 is secured, while the other shaft xa is free to move,

when the arm 42 is at its starting position shown in FIG.

6. The rotation of the motor M set in motion, then, is conveyed to the pinion G4, as already mentioned. By the rotational force of this pinion G4, which is in mesh with the ring gear G1, the arm 42 starts turning clockwise, in FIG. 6, to a position shown in FIG. 8, while taking a tomogram of the arc Al-A2 on a radiographic film carried by the holder 2.

At the position of FIG. 8, the shaft xa of the arm 42 is located at the center 7 of the arc A2-A3 (because the distance between the shaft 8a and the shaft xa is equal to a difference between rl and r2). Hence, by resuming the rotation of the motor M upon securing the shaft xa and releasing the shaft 8a, the arm 42 similarly starts turning round the shaft xa due to the rotational force obtained by the intermeshing of the pinion G4 and the ring gear GI, past the position of FIG. 9, until holder 2. Now, with the shaft 8a of the arm 42 located at the center 6 of the arc A3-A4, this shaft 8a is secured while the other shaft xa is released, and the arm 42 is similarly turned round the shaft 8a to the position shown in FIG. 5, thereby taking a tomogram of the final arc A3-A4.

It will now be clear how a complete tomogram of the arcs Al-A2, A2-A3 and A3-A4 is obtained during the turn of the arm 42.

To elaborate further on the above described operations from a mechanical point of view, the vertical shafts 8a and xa serving as a pivot for the turn of the arm 42 are secured alternately at the three

points

6, 7 and 8 (which are off the center of the ring gear G1) within the hole 44 of the disk 43. Consequently, as may be seen from FIG. 8, a distance between the pivot of the arm 42 and the intermeshing point of the ring gear G1 and the pinion G4 is subject to variation along with the turn of the arm 42. Should the motor M be installed fixedly on the arm 42, therefore, the pinion G4 would be meshed incompletely with the ring gear G1, either too deep or disengaged altogether therefrom, thus hampering the smooth turn of the arm 42. This is the reason why, according to the present invention, the motor M is installed on the motor base 48 which is slidable along the guide 47 upon the arm 42 and, further, the ring gear G1 is provided with the two

rollers

48 and 52 which are caused to rotate in internal and external contact, respectively, therewith. The motor M is thus enabled to adjust its position according to the radius of the turn of the arm 42, while the pinion G4 is always kept in proper mesh with the ring gear G1, so that the uninterrupted turn of the arm 42 is insured.

While in the above described example of the device for turning the arm 42 along an approximately parabolic curve in accordance with the concepts of the invention, the ring gear G1 secured to the disk 43 is kept in constant mesh with the pinion G4 by means of the motor M that is made slidable along the guide 47 upon the arm 42 simultaneously with the turn of this arm 42, the same purpose can also be accomplished by securing the ring gear G1 to the arm 42 and installing the motor M upon the disk 43 so as to be slidable together with the turn of the arm 42.

The foregoing configurations make possible to take a series of tomograms of the entire jawbones or the dentition of an individual, provided, however, that his head is held securely in position. Such a head holding device in accordance with the invention will now be described with reference to an example illustrated in FIGS. 10 through 12.

As seen in the drawings, a casing 53 contains rails 54, and slidably mounted onthese rails 54 is a movable member 55 which is provided with a threaded rod 56 so as to be capable of being secured at a desired position and further with a pair of racks 57 and 58 (still to be described with reference to FIG. 13) with their toothed surfaces opposed to each other. Between these

racks

57 and 58 there is provided a pinion 59 so as to.

rods

68 and 61 are provided downwardly at the opposite ends of the

racks

57 and 58, respectively, and these

rods

60 and 61 are provided at their lower ends with transparent ear-

rods

63, 63 having

flanges

62, 62 and so shaped as to fit in the outer orifice of the ear. A supporting portion 64 (refer to FIG. 11) connected to the aforesaid casing 53 has a holding member 65 which is caused to be slidable toward and away from a column 9 and to be stopped at any desired position in the course of its forward and backward travels. The holding member 65 is attached with a chin rest 68 which may include a vertical portion 66 and a horizontal portion 67. Further, this same holding member 65 is provided with an indicator means 69, the graduations 70 for which are given on the supporting portion 64 (refer to FIG. 12).

A bracket is supported by the aforementioned column 9 so as to be vertically movable. Adapters 71 and 72 for the ear-

rods

63, 63 are so attached to the

vertical rods

60 and 61 as to be freely movable throughout the length thereof and to be fixed at any desired position, while these

rods

60 and 61 are calibrated for indication of the heights of those ear-

rods

63, 63. An indicator means 73 provided to the movable member 55 is for indication of its movements toward and away from the mentioned column 9. A worm gear 74, on the same shaft as the aforesaid pinion 59, is in mesh with a worm 75 which is mounted on a manual rotation shaft 76 so as to be slidable along its length and also to be rotated together with the shaft 76. These transmission means, however, may be served as well by bevel gears and the like. The manual rotation shaft 76 is provided with a handle 77. The aforesaid chin rest 68 is attached to the holding member 65 by means of a screw 78 so as to be vertically movable, to be fixed exactly at a desired position by means of graduations 79 (refer to FIG. 10) calibrated on the holding member 65. A head support 80 (refer to FIG. 11) cooperates with the ear-

rods

63, 63 and the chin rest 68 in order to set the head of a patient at a correct position. This head support 80 is supported by means of an adapter 81 so as to be vertically movable, while the position of this adapter 81 is made adjustable in directions toward and away from the column 9 by means of a screw 82. As seen in FIGS. 10 and 12, the arm 42 is provided at one end with the X-ray tube 1 and at the other end with the radiographic film holder 2 and the screen 5, so as to be turnable altogether.

The operations and functions of the head holding device, described in the foregoing with reference to FIGS. 10, 11 and 12, are explained hereinbelow.

For keeping the head of a patient at a proper position, the pinion 59 is first turned manually by means of the handle 77 thereby to adjust the

racks

57 and 58 at their desired positions. Thus, upon insertion of the

earrods

63, 63 into the earholes to a depth determined by their

flanges

62, 62, the head is now positioned without any sideways inclination. The head is then further readjusted as to its inclinations in front and rearward directions by means of the chin rest 68 which may consist of the vertical portion 66 and the horizontal portion 67. These simple operations are enough to position the head ready for its tomographic examination, as well as to select desired planes in the head for that purpose repeatably.

Since the ear-

rods

63, 63 are attached to the

vertical rods

60 and 61 secured respectively to the different ends of the

racks

57 and 58 meshed with one and the same pinion 59, the ear-rods are adjustable simultaneously in coordinated movements by turning the handle 77 of the pinion 59. When the ear-rods are inserted into the earholes of a patient, his head is not only oriented in the proper direction without any sideways inclination but is located at the exact position for tomographic examination. In this case, if ear-

rods

63, 63 are made of a transparent material, the ear-

rods

63, 63 enable the examiner to visually confirm if they are inserted properly into the earholes, even though they are provided with the

flanges

62, 62. Further, according to the present invention, the movable member 55 having all these

racks

57 and 58 and the pinion 59 is mounted on the rails 54 so as to be movable toward and away from the column 9, so that the head held by the

earrods

63, 63 can be adjusted at a position most suitable for taking tomograms of desired planes therein. Accordingly, a series of tomograms thus taken of a parabolically curved object are extremely clear and without substantially any duplex portions from one to the other. Furthermore, the exact positions of the movable member 55 and the chin rest 68 are clearly indicated on their respective graduations, so that, even when a patient is to have his head examined at intervals, the head can be set at the same position as before each time he sits for foregoing another tomographic examination. It is accordingly possible to grasp with much appropriateness the progress of a physical or pathological defect or a difference in its conditions before and after treat ment.

FIG. 13 illustrates another example of a means for the adjustment of the

vertical rods

60 and 61 and, therefore, the ear-

rods

63, 63 in accordance with the present invention. In this example, as in the foregoing one shown in FIG. 10 in particular, the ear-

rods

63, 63 having

flanges

62, 62 are provided at the lower ends of the

vertical rods

60 and 61. Further, in FIG. 13, the reference numeral 84 indicates a bracket; 86 a holding portion; a shaft rotatably installed through the holding portion; 87 a turnable disk secured to the shaft 85; 88 holes formed on the upper surface of the disk 87; and 89 a fixing means provided to the holding portion 86 in order to fix the turnable disk 87 by being inserted in one of its holes 88. Two

parallel racks

57 and 58 and, fixedly provided thereto, sliding portions 60a and 61a of the

vertical rods

60 and 61 are slidably mounted on a guide 83 secured to the bottom of the disk 87. Provided between these two

racks

57 and 58 is a pinion 92 which is in mesh with both of the racks and which is provided with a knob 93.

Thus, by appropriately turning the knob 93 of the pinion 92 in either direction, the

racks

57 and 58 and, therefore, the sliding portions 60a and 61a of the

rods

60 and 61 move correspondingly in the opposite directions so that the ear-

rods

63, 63 may fit in the outer orifices of the earholes of a patient for the proper adjutment of his head.

Further, with reference to FIG. 14, the ear-rods 63 together with its flange 62 is made of transparent material as in the foregoing example, and an electric lamp 90 supplied with power by means of lead wires 91 is installed therein. By the provision of this electric lamp 90, the operator can adjust the knob 93 of the pinion 92 while visually inspecting the depth of insertion of the ear-rod 63 in the earhole of a patient. It will be needless to say that the provision of such an illuminating means only to one of the ear-rods is enough to serve the above purpose.

Now, in taking tomograms of the dentition, jawbones and other objects in the head as in the foregoing, consideration should also be given to the fact that such cavities present therein as the mouth, the nostrills and the throad permit the penetration of too much X-rays more than other part when these are radiated in certain directions. The resultantly produced unevenness in the tone of a radiographic film containing a series of tomograms prevent the physician from obtaining correct diagnostic information therefrom. This defect, however, can be eliminated by another device of the invention newly introduced herein, in which filter means capable of limiting the penetration of X-rays is installed on the side of an X-ray tube and/or a radiographic film, thereby to obtain a tomogram of uniform tone.

An example of such a device will now be described in detail with reference to FIG. 15. A hood 94 made of transparent plastics permitting the penetration of X- rays is supported by parts of the above described head holding device so as to enclose the jawbones 95, spinal column 96, dentition and other parts of the head as in the drawing. This hood 94 is attached with filter means 97 and 98 capable of limiting the penetration of X-rays radiated, and made, for instance, of acrylic resin. Lacking these filter means 97 and 98, more of the X-rays radiated in the arrow marked directions over widths A and B, for example, would reach a radiographic film (disposed in front of the hood 94) than those radiated in other directions, thus rendering the film portions impinged upon thereby darker than the rest and leaving indistinct images of the jawbones 95 and so forth thereon. This undesirable darkening of parts of the film can be successfully overcome by the device of the invention, with its acrylic-resin-made filter means 97 and 98 attached to the hood 94, either on its inside or outside surface and either closer to the radiographic film or to the X-ray tube.

The filter means 97 attached to the open end of the hood 94, at the back of the spinal column 96 in FIG. 15, may be made outwardly openable by means of hinges 99. This helps a patient to move his head into and out of the hood 94.

It is also noteworthy that the above described device is capable of greatly reducing the high doses of X-rays administered hitherto to a patient throughout a series of radiating operations (from 10 to 14 sheets of radiographic film for an adult) for the intraoral radiographing examination of his dentition.

Although several specific examples of the various devices proposed by the present invention have been shown and described in the foregoing, it will be obvious that many modifications, substitutions and changes thereof are possible. The invention, therefore, is not intended to be restricted by the exact showing of the drawings and the description thereof but is considered to include other examples coming within the spirit of the invention.

We claim:

1. In apparatus equipped with a radiant rays source and a radiographic film holder thereby to take a tomogram of an object in the shape of an approximately parabolic curve consisting of not less than two arcs of different curvatures; a head holding device comprising, in combination:

a column slidably supporting the head holding device proper;

a movable member mounted on a pair of rails within a casing so as to be capable of moving toward and away from said column, said movable member having a means thereby to be secured at any desired position in the course of its travels;

a pair of racks disposed in side-by-side relationship across said movable member and having their toothed surfaces opposed to each other;

a pinion provided between said racks so as to be in mesh with both of them, said pinion having a means thereby to be turned manually from outside of said casing;

a pair of rods provided downwardly at the opposite ends of said racks, each of said rods having at the lower end a flanged ear-rods to be inserted into the outer orifice of the ear;

a chin rest provided to a holding member so as to be vertically movable, said holding member being installed in a supporting portion of said casing so as to be movable toward and away from said column and to be fixed at any desired position in the course of its travels; and

a head support including means for adjustment of its position in both vertical and horizontal directions.

2. A head holding device as claimed in claim 1, in which said holding member is provided with an indicator means, the calibrations for which are given on said supporting portion, and said holding member is provided with another set of calibrations for said chin rest connected slidably thereto, whereby a setting of said chin rest in both horizontal and vertical directions can be read numerically.

3. A head holding device as claimed in claim 1, in which said flanged ear-rods are transparent.

4. A head holding device as claimed in claim 3, in which illuminating means are provided in the hollowed interiors of said transparent flanged ear-rods.

5. A head holding device as ciaimed in claim 1, in which said movable member is provided with an indicator means capable of indicating its position in directions toward and away from said column.

6. A head holding device as claimed in claim 1, in which said vertical rods are calibrated for indication of the heights of said ear-rods provided slidably thereto. l k

Claims

1. In apparatus equipped with a radiant rays source and a radiographic film holder thereby to take a tomogram of an object in the shape of an approximately parabolic curve consisting of not less than two arcs of different curvatures; a head holding device comprising, in combination: a column slidably supporting the head holding device proper; a movable member mounted on a pair of rails within a casing so as to be capable of moving toward and away from said column, said movable member having a means thereby to be secured at any desired position in the course of its travels; a pair of racks disposed in side-by-side relationship across said movable member and having their toothed surfaces opposed to each other; a pinion provided between said racks so as to be in mesh with both of them, said pinion having a means thereby to be turned manually from outside of said casing; a pair of rods provided downwardly at the opposite ends of said racks, each of said rods having at the lower end a flanged earrods to be inserted into the outer orifice of the ear; a chin rest provided to a holding member so as to be vertically movable, said holding member being installed in a supporting portion of said casing so as to be movable toward and away from said column and to be fixed at any desired position in the course of its travels; and a head support including means for adjustment of its position in both vertical and horizontal directions.

5. A head holding device as claimed in claim 1, in which said movable member is provided with an indicator means capable of indicating its position in directions toward and away from said column.

6. A head holding device as cLaimed in claim 1, in which said vertical rods are calibrated for indication of the heights of said ear-rods provided slidably thereto.