JP3079900B2 - Hologram interferometer for measuring cylindrical optical elements - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hologram interferometer for measuring a surface state of a cylindrical surface in a cylindrical optical element such as a cylindrical lens and a cylindrical mirror.

[0002]

2. Description of the Related Art Generally, an interferometer is used to accurately and non-contactly measure the surface shape of a lens or other test object. A typical interferometer is a Fizeau interferometer. The Fizeau interferometer has a laser light source,
A beam splitter, a collimator lens, and a reference lens are used, and a test object is disposed in front of the reference lens. The laser light from the laser light source is reflected (or transmitted) to a beam splitter, and is made into a parallel light beam by a collimator lens. The parallel light beam is incident on a reference lens, and a part of the light is reflected by the reference surface. Observing interference fringes caused by the interference between the light reflected from the reference surface and the light reflected from the test surface by partially reflecting the light transmitted through the reference lens on the test surface of the test object. Is used to measure the surface shape of the test object.

[0003] The reference surface of the reference lens is an ideal shape of the surface of the test object. If the test object is a spherical lens, the reference lens may be a spherical lens. However, when the test surface is an aspherical surface, it is extremely difficult to accurately form the reference surface. On the other hand, in recent years, a hologram interferometer that measures the surface state of an object to be measured by using a computer-generated hologram has been put to practical use. A computer-generated hologram is formed by applying a photoresist film on a glass substrate and scanning the photoresist film with an electron beam to expose a hologram pattern having a lattice pattern equivalent to interference fringes between an object wave and a reference wave. And an optical element in which interference fringes are made visible by developing it.

According to the interference method using the hologram,
It can be used for a wide range of applications because it can inspect and measure aspheric surfaces and other special shapes. In particular, in recent years,
A large number of cylindrical optical elements are used in a device having a scanning optical system such as a copying machine and a facsimile, and a hologram interferometer must be used to accurately measure the surface state of such a cylindrical optical element. Can be.

There are two types of hologram interferometers: a reflection type and a transmission type. In a reflection type hologram interferometer, a reference beam and a measurement beam are obtained by irradiating a laser beam from a predetermined angle direction with respect to a hologram pattern forming surface of a hologram optical element and diffracting the laser beam on the hologram pattern. The reference light and the measurement light are both reflected on the hologram pattern forming surface. On the other hand, in the transmission type hologram interferometer, the reference light is reflected on the hologram pattern formation surface, but the measurement light is transmitted through the hologram pattern formation surface. If the surface to be inspected has a concave curved surface shape, the measurement can be performed in the same manner whether the surface is a reflection type or a transmission type. However, when the surface to be inspected has a convex curved surface shape, the reflection type hologram interferometer causes a problem of eclipse of the light path of the light incident on the hologram optical element. Therefore, it is necessary to dispose them at predetermined intervals, which limits the measurable curvature of the test surface. On the other hand, when the transmission type hologram interferometer is used, the test object can be arranged at a position very close to the hologram optical element, and thus there is an advantage that the measurable range is widened.

[0006]

In the above-mentioned transmission type hologram interferometer, various types of light sources are provided from a laser light source to a test object via a hologram optical element and to an interference fringe observation unit. The optical members must be accurately arranged, and when the test object is an aspherical optical element, the arrangement of various optical members to be used is limited. The overall configuration will be considerably larger. For these reasons,
At present, an apparatus for measuring an aspherical optical element using a transmission hologram interferometer has not yet been developed.

The present invention has been made in view of the above points, and an object of the present invention is to provide an apparatus capable of accurately measuring a cylindrical optical element having a small and compact configuration and having an aspheric surface to be measured. Is to provide.

[0008]

In order to achieve the above-mentioned object, the present invention provides a light source unit which converts a laser beam from a laser light source into a parallel light beam and emits the same in order to measure the surface shape of a cylindrical optical element. A light source / observation unit with an interference fringe observation unit, an interferometer unit with a transmission type hologram optical element, and a test object placed with its test surface facing up and position adjustment An interferometer unit , comprising:
Is provided in the housing, and the light source / observation unit is provided.
Mirrors that route the optical path of laser light from
And the periphery of the outer surface of the opening formed in the lower surface of the housing.
And the hologram optical element is detachably mounted.
The mounting portion to be attached and the housing from the outside of the housing.
Adjusting the position of the hologram optical element with respect to the attachment portion
It is characterized by having a configuration provided with a position adjusting means .

[0009]

First, the interferometer device is composed of three units in terms of function. The light source / observation unit can be used not only as a transmission type hologram interferometer but also as a reflection type hologram interferometer as a basic configuration of an interferometer device, and can also be used as an interferometer using a reference lens. It is. In other words, by changing the members arranged in the optical path where the laser light converted into a parallel light beam from the light source / observation unit is guided,
Since various types of interferometer devices can be configured, the devices can be shared, and mass production effects can be expected.

[0010] The optical path from the light source / observation unit is routed, and the interferometer unit equipped with the hologram optical element and the object mounting unit provided with the mounting table on which the object is mounted are separated. , The assembling of the interferometer unit is facilitated, which is advantageous in terms of maintenance and the like. In addition, since the periphery of the mounting table can be arranged in an open space, there is an advantage that the test object can be easily attached to and detached from the mounting table, and the automation can be performed.

As described above, when the optical system is composed of three units, the respective optical axes must be matched. In particular, the position between the hologram optical element and the test object needs to be extremely strictly adjusted. The test object is mounted on a mounting table, and when the test object is mounted on the mounting table, the test object must be kept in a stable state. For this reason, there is a limit in adjusting the mounting table to the hologram optical element. On the other hand, between the light source / observation unit and the interferometer unit, as long as the position of the hologram optical element and the test object are correctly aligned, there is no particular problem even if there are some errors during assembly.

As described above, in the present invention, the hologram optical element is mounted on the mounting portion, and the position of the hologram optical element can be adjusted on the mounting portion.
The position of the hologram optical element can be adjusted in the rotation direction. This makes it possible to adjust the direction of the hologram optical element and the direction of the test object so that they exactly match. Further, the angle can be adjusted so as to be inclined in an arbitrary direction with respect to the optical path of the light incident on the hologram optical element.
Thereby, the parallelism between the hologram optical element and the test object can be adjusted. Further, since the mounting table on which the test object is mounted is adjustable, the hologram optical element can be aligned with the reflection mirror by adjusting the mounting table to the hologram optical element within a certain range. Thus, the relative positions of the three units can be accurately adjusted. Moreover, the position adjustment of the hologram optical element
Is easy outside the housing together with the adjustment of the position of the test object
Can be done.

In the interferometer unit, the optical path can be routed in an arbitrary direction by a reflecting mirror. For example, the optical path is guided once downward, and then routed horizontally and upward. With this configuration, the light source / observation unit can be held so as not to protrude upward. By arranging such an optical path, the light source / observation unit can be arranged at a lower position. As a result, the center of gravity of the entire interferometer device is lowered, and the influence of vibration and the like can be suppressed.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, FIG. 1 shows the principle configuration of a hologram interferometer apparatus. In the figure, reference numeral 1 denotes an interferometer device, which is provided with a laser light source 2 composed of a He-Ne laser, a reflection mirror 3, a diverging lens 4, and a pinhole 5, and a laser beam from the laser light source 2. The beam is bent by 90 ° by the reflection mirror 3, passes through the diverging lens 4, passes through the pinhole 5 disposed at the condensing position of the diverging lens 4, diverges, and expands the spot diameter thereof. Then, the direction is changed again by 90 °, the light travels from the laser light source 2 in the direction opposite to the emission direction, and is collimated by the collimator lens 7.

The parallel light is first reflected on the first reflecting mirror 8 and then reflected on the second reflecting mirror 9, and then the light path is directed upward. Then, after the laser light from the second reflection mirror 9 is once turned back by the third reflection mirror 10, the laser light turned back by the third reflection mirror 10 is further reflected on the fourth reflection mirror 11. Like that. The hologram optical element 12 is provided to face the fourth reflection mirror 11. When a laser beam is incident on the hologram optical element 12, the laser beam is divided into a reference beam and a measurement beam. The reference light travels in the same optical path as the incident optical path, in a direction opposite to the incident optical path, and the measurement light passes through the hologram optical element 12.

On the other hand, a cylindrical lens 13 (hereinafter, referred to as a test object 13) as a test object is arranged in an optical path of the measurement light. Here, the hologram optical element 12 diffracts the incident light and separates the reference light and the measurement light. The reference light has a planar wavefront, and the measurement light needs to have a cylindrical wavefront. As shown in FIG. 2, the hologram pattern of the hologram optical element 12 includes a first pattern 12a formed of a parallel linear grid in a direction perpendicular to the generatrix of the test object 13 and a direction orthogonal to the generatrix. Second pattern 1 in an arc shape toward
2b. Therefore, when parallel light is incident on the hologram optical element 12 from a diagonally upper direction at a predetermined angle, the light is diffracted by the action of the first pattern 12a and is reflected in the direction returning to the optical path as reference light, and the second pattern At the time of transmission through 12b, diffraction occurs, resulting in measurement light having a cylindrical wavefront that is parallel to the generatrix direction and converges to a convergence point f in a direction perpendicular to the generatrix.

The center of the circular arc surface of the test surface 13a consisting of the cylindrical surface of the test object 13 is arranged at a position coincident with the convergence point f. If the test surface 13a is a convex curved surface, the convergence point f at a position on the hologram optical element 12 side,
In the case of a concave curved surface shape, it is arranged at a position behind the convergence point f. The light irradiated on the test object 13 is partially reflected on the test surface 13a and returns to the hologram optical element 12. When the return light from the test object 13 passes through the hologram optical element 12, it returns to the collimator lens 7 as original parallel light. Therefore, the measurement light diffracted by the hologram optical element 12 is reflected on the test surface 13a of the test object 13, and the obtained object light interferes with the reference light diffracted by the first pattern 12a. Therefore, the reference light diffracted by the first pattern 12a in the hologram optical element 12 is converted to the light diffracted by the second pattern 12b when the test surface 13a of the test object 13 has an ideal shape. 13 is designed to have the same characteristics as the light reflected by the test surface 13a of the test object 13 and diffracted again by the second pattern 12b. Converted to information. This interference fringe image passes through the beam splitter 6 and passes through the screen 20 forming an interference fringe observation unit and the interference fringe imaging lens 21 provided at the rear focal position of the collimator lens 7 to form the imaging unit 2.
By forming an image on the imaging surface of No. 2, the observation becomes possible.

The hologram optical element 12 converts the plane wave into an aspherical wave corresponding to the surface 13a of the test object 13 by the action of the hologram optical element 12. Interference fringes are generated as a result of interference between parallel lights. Therefore, an extremely clear interference fringe pattern is imaged by the imaging means 22. Therefore, the shape of the test surface 13a can be measured with extremely high accuracy.

Next, a specific configuration of the interferometer 1 will be described with reference to FIG. In the figure, reference numeral 30 denotes a surface plate, on which the light source / observation unit 31 and
An interferometer unit 32 and a specimen mounting unit 33 are fixedly attached. Test object mounting unit 33
Is mounted with the test object 13, and the surface shape of the test surface 13 a of the test object 13 is measured. Each of these units 3
1 to 33 are independently configured, and are individually installed on the surface plate 30.

The light source / observation unit 31 is composed of a main body casing 31a and a cylindrical body 31b. In the main body casing 31a, an optical path on the light source side from the reflection mirror 3 to the beam splitter 6 and a beam splitter 6 are provided. And an optical path on the image-forming side from to the image pickup means 22.
The collimator lens 7 is mounted on the lower end of the cylindrical body 31b. And this light source / observation unit 31
A connecting portion 31c is connected to the cylindrical portion 31b, and the connecting portion 31c is connected to a support post 34 set up on the surface plate 30.
To be able to move up and down. The support post 34 is a screw shaft, and the connecting portion 31c is moved up and down along the support post 34 to adjust to a required height position.
It can be fixed with a lock lever 35.

Next, the interferometer unit 32 has a housing 40. The housing 40 has a pair of side walls 40.
a, 40a and a peripheral wall 40b surrounding the both side walls 40a, 40a so as to keep them at a predetermined interval. The housing 40 has a lower projecting portion 40L projecting toward the light source / observing unit 31 and an upper projecting portion 40S projecting toward the specimen mounting unit 33 in the side surface shape. 40L is fixed to the surface plate 30. In addition, the bottom of the upper protrusion 40 </ b> S extends to an upper position of the test object mounting unit 33. As a result, the internal volume of the housing 40 can be made compact, and the front and left and right sides of the test object mounting unit 33 to which the test object 13 is attached and detached are opened,
The attachment / detachment operation can be easily performed.

The cylindrical portion 31b of the light source / observation unit 31 above the lower projecting portion 40L of the housing 40
A through hole 41 for guiding the laser light downward is formed at a position facing the substrate. Therefore, in the light source / observation unit 31, the laser beam converted into a parallel light beam by the collimator lens 7 is guided into the housing 40 through the through hole 41. In the housing 40, first and second reflection mirrors 8, 9 are fixedly mounted on the lower projecting portion 40L on the lower side in order to route the optical path of the laser light guided inside. The laser light emitted downward from the light source / observation unit 31 is turned by the first and second reflection mirrors 8 and 9 downward so that the laser light is directed upward. It is guided to the upper protrusion 40S on the side. A third reflecting mirror 10 and a fourth reflecting mirror 11 are provided in the upper overhanging portion 40S on the upper side. And the upper overhang 4
A mounting portion 42 is provided on the lower surface of the OS, and the hologram optical element 12 is disposed so as to face the fourth reflection mirror 11. First to fourth reflection mirrors 8 to 11
Among them, the first to third reflection mirrors 8 to 10 are mounted on mirror holders 8a to 10a, and the mirror holders 8a to 10a are fixed to the side wall 40a of the housing 40 using screws or the like.

Here, the hologram optical element 12 is irradiated with light from obliquely above at a predetermined angle. When exposing the hologram pattern on the hologram optical element 12, the incident angle of the light with respect to the hologram optical element 12 is made to coincide with the angle at which the light corresponding to the reference light in the first pattern 12a is irradiated. Thereby, the hologram optical element 12
When light is incident on the optical path, diffracted light traveling in the opposite direction is obtained on the same optical path as the incident optical path. The test object 13 is a cylindrical optical element, and the cylindrical optical element is often long in the generatrix direction. For this reason, the test object 13 does not interfere with each part constituting the interferometer apparatus 1. In order that the optical path of the light from the third reflecting mirror 10 can be reflected by the fourth reflecting mirror 11 so as to be directed downward in order to mount the object on the test object mounting unit 33, FIG. The light path is not simply directed downward just as indicated by the imaginary line, but is directed 90 ° to the incident light to the fourth reflection mirror 11 as indicated by the solid line in FIG. Incident on the hologram optical element 12 at a predetermined angle θ. Thereby, by arranging the test object 13 in a direction orthogonal to the incident direction of light from the third reflection mirror 10 to the fourth reflection mirror 11,
The measurement becomes possible.

In order to change the optical path in this direction, the fourth reflecting mirror 11 is directly mounted on the mirror holder 43 provided on the side wall 40a of the housing 40.
Is not fixed, but a mirror mount 44 is fixedly provided, and the fourth reflection mirror 11 is fitted into a concave portion 45 provided on the surface of the mirror mount 44. Thus, as shown in FIGS. 5 and 6, the mirror mount 44 is formed by moving the columnar member obliquely with respect to its axis.
It has a shape cut at an angle of 5 °, and a concave portion 45 is provided in this oblique cut surface portion 44a. On the mirror mount 44, a circular connecting portion 46 protruding in the axial direction of the mirror mount 44 is connected to the side opposite to the side where the concave portion 45 is formed, that is, the surface 44 b in the direction perpendicular to the axis. The connecting portion 46 is connected so as to be fitted to a receiving portion 47 provided on the mirror holder 43, and is fixed by screwing four screws 48. . With this configuration, as shown in FIG. 5, if the cut surface portion 44a of the mirror mount 44 is mounted to the mirror holder 43 with the cut surface portion 44a facing the third reflection mirror 10, the mirror mount 44 can be mounted on the mirror mount 44. The outward path can be bent right below by the fourth reflecting mirror 11, and by rotating the mirror mount 44 in the direction shown by the arrow from this position, the optical path is rotated around the axis of the mirror mount 44. Thus, light can be made to enter the hologram optical element 12 in an oblique direction. For this purpose, as shown in FIG. 6, the mirror holder 43 is provided with screw insertion holes 49 at four positions, but these screw insertion holes 49 are not at four positions at the top, bottom, left and right, but at an angle therefrom. It is provided at a position rotated by θ, whereby the mirror mount 44 is mounted while being rotated in the direction of the arrow from the state shown in the figure. Of the four screws 48 to be screwed, one screw 48a is used as a reference screw, and this reference screw 48a is used.
a is inserted into the screw insertion hole 49a formed in the mirror holder 43 in a state where there is substantially no gap,
The screw insertion hole 49 through which the other screw 48 is inserted has some play, so that when the mirror mount 44 is mounted on the mirror holder 43, it can be finely adjusted in the rotation direction.

Next, the test object 13 is a cylindrical optical element such as a cylindrical lens or a cylindrical mirror shown in FIG. 7, and the test surface 13a is a cylindrical surface. The cylindrical surface has a generatrix B direction and a direction orthogonal to the generatrix B, that is, a curved surface R direction. The hologram pattern in the hologram optical element 12 for measuring the surface state of the test surface 13a is Thing 1
3 are arranged to face each other. Therefore, in order to accurately measure the surface condition of the surface 13a, the generatrix B is perpendicular to the second pattern 12b, and the center O of the curved surface R is the center line of the optical axis of the hologram optical element 12. On A,
The hologram optical element 1
The center line A must be positioned so that the generatrix B is perpendicular to the optical axis center line A.

For this purpose, the test object mounting unit 33 includes multi-axis adjusting means 50, and the mounting table 51 on which the test object 13 is mounted is mounted on the multi-axis adjusting means 50. 5
The test object 13 placed on 1 is positioned at the measurement position. Thus, the test object 13 has a bus B of the test surface 13a.
In the direction perpendicular to the plane of FIG.
Is mounted so as to abut the positioning protrusion 51a provided in the first position.

The multi-axis adjusting means 50 first has a Z-axis stage. In the Z-axis stage, a slide guide 52 is provided upright on the surface plate 30, and an elevating base 53 is mounted on the slide guide 52 as shown in FIG. The elevating base 53 includes a coarse sliding portion 53a and a fine sliding portion 53b. A lock screw 54 is mounted on the coarse sliding portion 53a, and there is a gap between the coarse sliding portion 53a and the fine sliding portion 53b. , Z
Screw shaft 55 (or micrometer head) for shaft adjustment
Is installed. Therefore, when the lock screw 54 is loosened, the elevating base 53 moves to the two sliding portions 53a, 53b.
Can be moved up and down in conjunction with each other (coarse movement operation), and the lock screw 54 is pressed against a frictional engagement portion 52a provided on the side surface of the slide guide 52 to fix the coarse movement slide portion 53a. When the screw shaft 55 is screwed, the fine movement slide portion 53b is minutely moved in a direction approaching / separating from the coarse movement slide portion 53a (fine movement operation).
be able to.

Fine movement slide portion 53 of elevating base 53
A support arm 56 extends from b. Then, an X for adjusting the horizontal position in the XY axis direction is
A Y stage and a θ stage for adjusting the θ direction are mounted. These horizontal plane adjustment units can adjust three axes in the XY axis direction and the θ direction. However, depending on the size of the test object 13, adjustment in the Y axis direction is not necessarily required. What is necessary is to be constituted by a biaxial adjustment member at least in the horizontal plane in the X-axis direction and the θ-direction. Thus, a guide rail 57 is provided on the support arm 56 in the Y-axis direction, and a Y-axis table 58 is mounted on the guide rail 57 so as to be movable in the Y-axis direction. A screw shaft 59 (or a micrometer head) for Y-axis adjustment is mounted on the Y-axis table 58, and the screw shaft 59 is screwed to rotate the Y-axis.
The axis table 58 moves in the Y-axis direction, that is,
3 can be slightly moved in the direction of the generatrix B when it is placed. The Y-axis table 58 is provided with a guide rail 60 in the X-axis direction.
Are provided so as to be minutely movable in the X-axis direction by a screw shaft 62 for X-axis adjustment.

The θ stage is provided on the X-axis table 61. That is, as is clear from FIG. 9, a ring-shaped fixed shaft 63 is protruded from the X-axis table 61, and a fine movement rotating ring 64 is inserted into the fixed shaft 63. The rotary table 6 is attached to the fine movement rotating ring 64.
The rotary shaft 65a connected to 5 is inserted. Fixed shaft 6
3 has two long holes 66 and 67 formed in two places, and a lock screw 68 is screwed into one long hole 66. The lock screw 68 is screwed into the fine movement rotating ring 64, and the tip end thereof is frictionally engaged with the rotating shaft 65a. Therefore, when the lock screw 68 is separated from the rotary shaft 65a, the rotary shaft 65a can freely rotate, and the rotary table 65 can perform a coarse rotation operation in the θ direction. An operating finger 69 connected to the fine rotation ring 64 extends from the other long hole 67,
The operating finger 69 has a screw shaft 7 for fine movement in the θ direction.
The tip of 0 (or micrometer head) abuts, and the operating finger 69 is urged by a spring 71 in the direction of pressing against the screw shaft 70 from the opposite direction. Therefore, the lock screw 68
When the screw shaft 70 is screwed in a state in which the rotary shaft 65a and the fine movement rotating ring 64 are integrated with each other, the rotation table 65 and the fine movement rotating ring 64 within the range of the width of the long hole 67.
Can be finely adjusted.

The rotary table 6 constituting the θ stage
5, a tilt direction adjustment stage is provided as shown in FIGS. 10 and 11. This tilt direction adjusting stage has a substantially rectangular tilt base 72, a spherical joint 73 is provided at the center of the tilt base 72, and a spherical bearing 74 in which the spherical part 73 a of the spherical joint 73 is provided on the rotary table 65. It is inserted in. A pair of screw shafts 75 and 76 are located at a position separated by a predetermined distance from the disposition position of the spherical joint 73 in the direction of the generatrix B and a direction orthogonal to the generatrix B.
Are screwed from below the rotary table 65, and these two screw shafts 75, 76 are in contact with receiving portions 77, 78 (the receiving portions 78 are not shown in the drawing) provided on the lower surface of the tilt base 72. And the screw shafts 75, 7
6, compression springs 79 and 80 are stretched between the tilt table 72 and the rotary table 65, respectively. Therefore, if the screw shaft 75 is screwed, the tilt table 72
Can be tilted to the tilt axis T ₁ around. The tilt axis T ₁ is an axis that passes through the optical axis center line A of the hologram optical element 12 and is orthogonal to the generatrix B of the test object. Further, when Nishikai the screw shaft 75, the tilt stage 72 can be tilted to a tilt orthogonal axes T ₂ around orthogonal to the tilt axis T _1. Although this adjustment of the tilt orthogonal axis T ₂ direction is not necessarily required, the hologram optical element 12
When it is necessary to accurately arrange the center axis A of the test object 13 at the center position of the test object 13, the screw shaft 76 is appropriately screwed,
It may be adjusted inclination angle of tilt orthogonal axis T ₂ direction.

As described above, when the surface state of the test object 13 is measured by using the multi-axis adjusting means 50, the mounting table 51 on which the test object 13 is set is moved in the XY directions and θ.
Adjustable in the direction and tilt direction.

As described above, the hologram optical element 12 is mounted on the mounting portion 42 provided around the opening 42a formed on the lower surface of the upper protruding portion 40S in the housing 40 of the interferometer unit 32. Part 42
Has a configuration in which the hologram optical element 12 can be adjusted in the rotation direction and the tilt direction. Here, the rotation direction position adjustment mechanism has the same configuration as the θ direction adjustment means of the mounting table 51, and the tilt direction adjustment mechanism has substantially the same configuration as the tilt direction adjustment means of the mounting table 51. Has become.

As shown in FIGS. 12 to 14, the outer shape of the hologram optical element 12 is square, but the hologram optical element 12 is fixed to a circular hologram holder 81. Hologram holder 8
Reference numeral 1 is connected to the support plate 82 so as to adjust the inclination. The support plate 82 is a circular member having a through-hole 82 a having substantially the same shape as the hologram optical element 12. The hologram holder 81 and the support plate 82 are spaced apart by 90 °. A pair of adjusting screws 83 and 84 are provided, and a spherical joint 85 is provided at a position 180 ° from one adjusting screw 83. The adjusting screws 83 and 84 are
The screw holes 82 b, which extend through the insertion holes 81 a, 81 b provided in the hologram holder 81 and are formed in the support plate 82.
82c. The adjusting screws 83 and 84 have large-diameter portions 83 a and 8 that come into contact with the hologram holder 81.
4a is formed, and the tip portion is formed with a screw portion 83
b, 84b. On the other hand, the spherical joint portion 85 includes a shaft portion 85a fixed to the support plate 82 and the shaft portion 8a.
The hologram holder 81 has a spherical receiving portion 85c with which the spherical portion 85b engages. Further, springs 86, 87 are mounted on the adjustment screws 83, 84 at positions between the support plate 82 and the hologram holder 81.

With the above arrangement, when the adjusting screw 83 is screwed in and out, the hologram holder 81 is
Relative to the support plate 82, should be able to tilt about the axis A _1, also by operating the adjusting screw 84, the hologram holder 81 can be tilted about an axis A _2, whereby the hologram optical element 12 In the optical path cross section of the incident light, the angle can be adjusted in an arbitrary direction.

The support plate 82 is connected to the mounting portion 42 provided on the lower surface of the upper overhang portion 40S so that the position thereof can be adjusted in the rotational direction. The mounting portion 42 is provided fixed to the housing 40 and has a fixing ring 90 formed in a frame shape.
A fine rotation ring 91 is inserted into the fixed ring 90, and a holding ring 92 into which the support plate 82 is screwed is inserted into the fine rotation ring 91. Further, the fixing ring 90 is provided with long holes 93 and 94, and a lock screw 95 is provided at a portion where one of the long holes 93 is formed.
Are in contact with the outer surface of the support plate 82 through the fine rotation ring 91. An operation finger 96 protruding from the other long hole 94 is connected to the fine movement rotating ring 91,
The tip of the operating finger 96 projects outward from the fixing ring 90. This portion comes into contact with the tip of an adjusting screw 98 screwed into a housing 97 provided in connection with the fixing ring 90, and in this housing 97, a direction in which the operating finger 96 is pressed against the adjusting screw 98. The spring 99 that urges the spring is elastically mounted.

With this configuration, when the lock by the lock screw 95 is released, the support plate 82 can be freely rotated, and the hologram optical element 12 provided on the hologram holder 81 connected to the support plate 82 is provided.
Can be adjusted in the rotational direction. Further, the hologram optical element 12 is oriented in a predetermined direction,
If the adjusting screw 98 is screwed in and out while the lock is performed by the step 5, the position of the hologram optical element 12 can be finely adjusted.

Thus, in order to measure the surface condition of the test surface 13a, which is a cylindrical surface of the test object 13, the light incident on the hologram optical element 12 needs to be incident at a predetermined angle θ. is there. The incident angle θ must be exactly the same as the angle of the reference light diffracted by the hologram optical element 12. The test object 13
Needs to be arranged at a position directly facing the hologram optical element 12. For this purpose, the optical path from the laser light source 2 to the test object 13 via the hologram optical element 12 and the test object 1
The optical path from 3 to the imaging means 22 via the hologram optical element 12 must be adjusted very strictly. Since the light source / observation unit 31 is assembled in a state in which the light source / observation unit 31 is accurately positioned in advance, no deviation of the optical axis occurs between them. First to fourth reflection mirrors 8 to 1
Similarly, the positional relationship 1 is accurately incorporated in advance. If the light source / observation unit 31 and the interferometer unit 32 are accurately assembled on the surface plate 30, the optical axes of the two units will be exactly the same.

However, the hologram optical element 12 mounted on the interferometer unit 32 is appropriately replaced according to the object to be inspected.
It is extremely difficult to perform accurate positioning when the camera is mounted on the camera 2. Unless the hologram optical element 12 is strictly aligned with the fourth reflection mirror 11 and the mounting table 51, accurate measurement of the test object 13 cannot be performed.

Therefore, first, if the hologram optical element 12 is accurately placed in a horizontal state, the fourth reflection mirror 11 makes light incident on the hologram optical element 12 at an angle θ from the fourth reflection mirror 11. It is located where it can. However, since there is a mechanical error or an assembly error of the apparatus, the mirror holder 43 can be rotated by a small angle with respect to the mirror mount 44 around a portion fixed by the reference screw 48a. By absorbing these errors, the direction of incidence on the hologram optical element 12 can be adjusted very accurately.

Next, the hologram optical element 12 must be arranged in a horizontal state, and the direction in which the hologram pattern is formed must exactly match the direction of the subject 13 placed on the placement table 51. Then, by first screwing the support plate 82 into the holding ring 93 and appropriately adjusting the screws 83 and 84 into and out of the hologram optical element 12 with the hologram optical element 12 attached to the attachment portion 42, the hologram optical element 12 can be arbitrarily set. , The inclination of the hologram optical element is adjusted, and the hologram optical element is accurately leveled. In order to adjust the direction of the hologram pattern of the hologram optical element 12, if the hologram pattern is largely displaced, the lock screw 95 is first loosened and the hologram holder 81 on which the hologram optical element 12 is mounted is required. Rotate in the direction of. When the rotation direction is adjusted to some extent, fine adjustment is performed by tightening the lock screw 95 and then screwing the adjustment screw 98 in and out. As a result, if the test object 13 placed on the mounting table 51 is arranged at a predetermined position, the state is adjusted so that the measurement of the test surface 13a can be performed.

In the above state, the test object 13 is set on the mounting table 51 with the direction of the generatrix B directed to the lattice direction of the hologram pattern of the hologram optical element 12. Here, the hologram optical element 12 has its hologram pattern arranged in a direction perpendicular to the plane of FIG. 3 from the angle of the incident light from the fourth reflection mirror 11,
Therefore, the test object 13 is also set such that the generatrix B faces in the left-right direction. Thus, the mounting table 51 has no members on the front side and the left and right sides and is an open space, so that the work of attaching and detaching the test object 13 can be easily performed. In particular, when a long object is used as the test object 13 or when the attaching and detaching operation of the test object 13 is automated,
It is important that both the left and right sides of the mounting table 51 are open.

In measuring the surface shape of the test object 13, first, a sample in which the test object 13 is formed in an ideal shape is used, and the sample is set on the mounting table 51. If the mounting table 51 is held at a predetermined position, the hologram optical element 12 is in a state where the test object 13 mounted on the mounting table 51 can be measured. The position of the table 51 is adjusted. First, lock screw 5
Coarse slide part 53a which constitutes elevating base 53 by 4
Is released, and the elevating base 53 is largely moved up and down. After moving to a target position to some extent, the lock screw 54 is tightened to fix the coarse movement slide portion 53a of the elevating base 53. By screwing the screw shaft 55 in this state, the fine movement slide portion 53b moves up and down by a very small amount, and is strictly positioned in the Z-axis direction.

Since the mounting table 51 is linked to the support arm 56 provided on the fine slide section 53b, the mounting base 51 is roughly positioned in the Z-axis direction by the coarse slide section 53a.
By moving the fine movement slide portion 53b up and down by a very small amount, the sample is positioned in the Z-axis direction, that is, the position where the center O of the curved surface R on the cylindrical surface of the sample coincides with the condensing position of the measurement light from the hologram optical element 12. Can be adjusted. When the radius of curvature of the curved surface R is known in advance, the height position of the elevation base 53 is displayed on a scale, and a member having a scale such as a micrometer head is used as the screw shaft 55. If used, the position adjustment in the Z-axis direction can be performed very easily.

Next, even if the center O of the above-mentioned curved surface R is the same as the condensing position of the hologram optical element 12 in the Z-axis direction, there is a case where the position is shifted in the horizontal direction. Here, the curved surface R
Is a straight line in the direction of the generatrix B. Therefore,
It is necessary to adjust the position in the direction orthogonal to the generating line B on the horizontal plane, that is, in the X-axis direction. The position adjustment in the X-axis direction is performed by screwing the screw shaft 62 and moving the X-axis table 61 along the guide rail 60. Note that Y
The position adjustment in the axial direction is not necessarily performed. However, when the center of the surface to be measured coincides with the center axis of the hologram optical element 12, the position adjustment of the Y-axis table 58 is also performed.

Further, in order to make the direction of the generatrix B of the sample coincide with the direction of the hologram pattern of the hologram optical element 12, the θ axis is adjusted by rotating the screw shaft 70 and rotating the rotary table 65. Here, the rotary table 65 can perform a coarse movement operation and a fine movement operation, but the coarse movement operation is performed at the stage of initial adjustment, and the mounting table 51 and the hologram optical element 12 are substantially When the screw shaft 7 is set so that the axes are
By arranging 0 at a substantially central position of the elongated hole 67, adjustment in the θ direction can be easily performed by rotating the lens by a relatively small angle.

Thereafter, the tilt direction is adjusted to adjust the inclination of the generatrix B of the sample. This adjustment in the tilt direction is performed by screwing the screw shaft 75 to the tilt base 72.
Is tilted around the tilt axis T ₁ to generate the bus B
Are positioned so as to be orthogonal to the central axis A of the hologram optical element 12.

By performing the above operation, the test object 1
The mounting table 51 on which 3 is set is precisely located at the measurement position. Therefore, the sample is removed from the mounting table 51, and the test object 13 is set on the mounting table 51.
The measurement light diffracted by the action of the second pattern 12b of the hologram optical element 12 is applied to the test surface 13a of the test object 13 and is reflected by the test surface 13a. Test surface 13
The object light reflected at a is incident on the hologram optical element 12, and is diffracted to become the original parallel light flux. On the other hand, the reference light diffracted by the action of the first pattern 12a of the hologram optical element 12 has a wavefront that would be obtained if the test surface 13a of the test object 13 is in an ideal state. Therefore, interference occurs between the object light and the reference light, and the test surface 13a of the test object 13 with respect to the ideal shape
The information relating to the difference in the surface shape can be extracted as interference fringe information, and can be imaged by the imaging means 22.

Incidentally, a cylindrical optical element used in a scanning optical system such as a copying machine or a facsimile is long, and when measuring the cylindrical surface of such a long cylindrical optical element, a hologram optical element is required. The measuring light from the element can irradiate only a part of its longitudinal direction. Therefore, when a long cylindrical optical element is used as a test object, it is configured as shown in FIGS. In the drawings, the same or equivalent members as those shown in FIGS. 1 to 14 are denoted by the same reference numerals, and detailed description thereof will be omitted.

Reference numeral 13 'denotes a test lens comprising a long cylindrical optical element. The mounting table 100 on which the test object 13' is set is mounted on the reciprocating means 101 in the Y-axis direction, that is, the generatrix direction. ing. The mounting table 100 has a convex portion 10 for positioning the test object 13 ′.
0a. The reciprocating means 101 is provided with the tilt table 7
2 has a slide guide 102 installed in the Y-axis direction, and the mounting table 100 is movable in the Y-axis direction along the slide guide 102. And the mounting table 1
A lock screw 103 is screwed into the mounting table 100 in order to stably hold 00 at a desired position in the Y-axis direction.
By press-contacting the friction plate 104 provided on the side surface of No. 02, it can be stably fixed at a predetermined position. In the drawings, reference numerals 105 and 106 denote stoppers for holding the mounting table 100 so as not to deviate from the slide guide 102.

According to this structure, the mounting table 100 can be adjusted in the Z-axis adjustment, the X-axis adjustment, the θ-direction adjustment, and the tilt direction adjustment at a certain position in the same manner as in the first embodiment. The position and direction are adjusted in this order, and then the measurement is performed while moving the mounting table 100 at a predetermined pitch interval, preferably at every measurable range. by this,
The entire length of the cylindrical optical element can be measured.

By the way, in the interferometer unit 32, the optical path is taken down once, and then the direction is changed so that the optical path is directed upward, so that the optical path is rationally routed and the light source / observation unit unit It is not necessary to dispose 31 at a very high position. As a result, the configuration of the entire interferometer device 1 does not protrude much upward,
The position of the center of gravity can be lowered. As a result, the influence of the surrounding vibration and the like is suppressed as much as possible, and the measurement of the test object 13 can be performed in an extremely stable state.

The measurement light generated by the hologram optical element 12 is light transmitted through the hologram optical element 12, and there is no optical path such as incident light or reference light in this direction. There is no problem that the optical path is deviated due to the arrangement of the optical path. For this purpose, the surface to be inspected 1
When the surface 3a is a convex surface, it is possible to measure the object 13 such that the surface 13a is almost in contact with the hologram optical element 12, so that the measurement can be performed in comparison with a reflection type hologram interferometer. The range of possible measurements is significantly increased.

The interferometer unit 32 is connected to the housing 4
0, the reference reflector 13 and the test object 13 from the laser light source 2 through the hologram optical element 12.
Out of the entire optical path, the connection between the light source / observation unit 31 and the housing 40 of the interferometer unit 32 and the distance from the housing 40 to the test object 13 are extremely small. Moreover, since only the minimum necessary optical path portion is exposed outside, most of the optical paths are arranged in a closed space, so that harmful light can be prevented from entering and problems such as fluctuation of the optical path etc. Therefore, the surface state of the test object 13 can be measured in an extremely stable state.

[0054]

As described above, according to the present invention, when a transmission type hologram interferometer is used to measure a surface of a test object composed of a cylindrical optical element,
Most of the optical paths of the interferometer unit are closed in the housing.
When placed in a chain space to prevent harmful light from entering
In both cases, a reflection mirror is used to prevent fluctuations in the optical path.
Arrange the optical path to be routed in the housing and
Position of the optical element can be adjusted from outside the housing.
When the hologram optical element is mounted
In addition, the position can be adjusted easily and accurately.
With a compact, compact, and compact configuration, the surface of the aspherical cylindrical optical element can be measured very accurately.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle of a hologram interferometer apparatus showing one embodiment of the present invention.

FIG. 2 is a diagram showing a hologram pattern in a hologram optical element.

FIG. 3 is a front view showing a specific configuration of the hologram interferometer apparatus, in which a housing of the interferometer unit is sectioned.

FIG. 4 is an explanatory diagram showing an optical path from a fourth reflection mirror to a test object via a hologram optical element.

FIG. 5 is a sectional view showing a mounting structure of a fourth reflection mirror.

FIG. 6 is an exploded perspective view of a mirror mount and a mirror holder.

FIG. 7 is an explanatory diagram showing a positional relationship between a test lens and a hologram optical element.

FIG. 8 is an explanatory diagram of a configuration of a Z-axis adjustment stage constituting a multi-axis adjustment unit.

FIG. 9 is a cross-sectional view showing the configuration of the θ stage.

FIG. 10 is a plan view of a tilt direction adjustment stage.

FIG. 11 is a sectional view taken along line XX of FIG. 10;

FIG. 12 is a bottom view showing a state where the hologram optical element is mounted on the mounting portion.

FIG. 13 is a sectional view taken along line YY of FIG.

FIG. 14 is a sectional view taken along the line ZZ of FIG.

FIG. 15 is a left side view of a test object mounting unit configured to measure a long cylindrical optical element.

FIG. 16 is a front view of FIG.

[Explanation of symbols]

 Reference Signs List 1 interferometer device 2 laser light source 6 beam splitter 7 collimator lens 8, 9, 10, 11 reflection mirror 12 hologram optical element 12a first pattern 12b second pattern 13, 13 'test object 13a test surface 31 light source Measuring unit 32 Interferometer unit 33 Specimen mounting unit 40 Housing 41 Through-hole 42 Mounting unit 43 Mirror holder 44 Mirror mount 50 Multi-axis adjusting means 51, 100 Mounting table 81 Hologram holder 82 Support plate 83, 84 Adjustment Screw 90 Fixing ring 91 Fine rotation ring 95 Lock screw 96 Operating finger piece 97 Adjusting screw 101 Reciprocating means 102 Slide guide

Claims (5)

(57) [Claims] 1. A light source / observation unit unit having a light source unit for converting a laser beam from a laser light source into a parallel light beam and emitting an interference fringe observation unit for measuring the surface shape of the cylindrical optical element; An interferometer unit having a hologram optical element, and an object mounting unit having an adjustable mounting table on which an object is mounted with the surface to be inspected facing upward. , The interferometer unit is provided in a housing, and the light source / observation unit is
A plurality of reflection mirrors for routing the optical path of the laser light, and around the outer surface of an opening formed in the lower surface of the housing.
Provided, the hologram optical element can mounted is detachably
A mounting part to be attached to the mounting part from outside the housing.
A hologram interferometer for measuring a cylindrical optical element, comprising: a position adjusting means for adjusting the position of the program optical element . 2. A reflection mirror disposed at a position where the light enters the hologram optical element, and reflects the light incident on the reflection mirror such that the light is directed in a direction in which the light is rotated by a predetermined angle around the reflection mirror. The hologram interferometer for measuring a cylindrical optical element according to claim 1, wherein: 3. The housing according to claim 2, wherein
2. The hologram optical element according to claim 1, further comprising means for adjusting the position of the hologram optical element in a rotational direction thereof, and means for adjusting the angle of the hologram optical element so as to be inclined in an arbitrary direction. Hologram interferometer for measuring cylindrical optical elements. 4. The apparatus according to claim 1, further comprising:
Means for adjusting the position of the test object on the mounting table,
The position adjusting means for adjusting the position of the hologram optical element;
A step is an opposing position in the lower part of the housing.
2. The arrangement according to claim 1, wherein the arrangement is arranged at a position.
Hologram interferometer for measuring cylindrical optical elements
Place. 5. A means for adjusting the position of the test object, and
Position adjusting means for adjusting the position of the hologram optical element
Consists of a plurality of adjustment screws.
The feature is that it can be adjusted by manual operation
The hologram for measuring a cylindrical optical element according to claim 4.
Interferometer device.