JPH06347210A - Hologram cassette for hologram interferometer device - Google Patents

Abstract

PURPOSE:To absorb light transmitted through a hologram optical element and prevent any harm by fitting a lid body with a light absorption function and a light diffusion function. CONSTITUTION:A lid body 32 is provided and is sealed to a cassette body opposingly while it is separated by a specific spacing for a reflection prevention type light absorption layer formation surface 34b of a hologram optical element 34. For example, a black paint is applied to the inner surface of the lid body 32 to achieve a light absorption function, the paint is applied, and then a satinized diffusion surface is obtained, thus enabling light to be absorbed by the light absorption diffusion surface 32a, even if light is transmitted on the light absorption layer formation surface 34b of the optical element 34. Also, even if light is not completely absorbed by the light absorption diffusion surface 32a, reflected light is not regularly reflected and is irregularly reflected, thus preventing any harm for an interference fringe image.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a lens, a plane-parallel plate,
The present invention relates to a hologram interferometer device for measuring the surface state of an object to be measured such as a mirror and other precision optical components, which is related to a hologram cassette that is exchangeably mounted according to the type of the object to be inspected.

[0002]

2. Description of the Related Art An interferometer is used to accurately measure the surface shape of a lens or other test object without contact. A typical example of this interferometer is a Fizeau interferometer as shown in FIG.

In the figure, reference numeral 1 denotes an apparatus main body, and the apparatus main body 1 has a main body casing 1a and a cylindrical portion 1b which is vertically provided on a lower surface of the main body casing 1a. A laser light source 2 made of a He-Ne laser or the like is attached to the main body casing 1a in parallel with the cylindrical body portion 1b. In the body housing 1a, the reflection mirror 3,
The diverging lens 4 and the pinhole 5 are provided, and the laser beam from the laser light source 2 is bent by 90 ° by the reflecting mirror 3 and passes through the diverging lens 4 to reach the diverging lens 4
After passing through the pinhole 5 arranged at the condensing position, the spot diameter is expanded and the spot diameter is expanded, and the light is reflected by the beam splitter 6 to change the direction of 90 ° again, and the laser beam is emitted along the axial direction of the cylindrical portion 1b. The light travels from the light source 2 in the direction opposite to the emission direction, is collimated by the collimator lens 7, and enters the reference lens 8 provided in front of it.

The reference lens 8 has, for example, a spherical reference surface 8b opposite to the incident surface 8a, and the incident surface 8a is provided with an antireflection coating. A part of the laser beam incident on the reference lens 8 is reflected by the reference surface 8b, and most of the laser beam is transmitted through the reference lens 8 and is incident on the surface 9a to be inspected of the lens 9 to be inspected set at the front position thereof. It is incident and a part of it is reflected by the surface 9a to be tested. Then, the reflected light from the test surface 9a and the reflected light from the reference surface 8b of the reference lens 8 interfere with each other to generate an interference fringe.
The reflected light having the interference fringes as described above is collimated by the collimator lens 7
And the beam splitter 6, and enters the image pickup means 12 through the screen 10 and the interference fringe image forming lens 11, and the image pickup means 12 photographs the interference fringes.
The image can be displayed on the monitor device.

Further, in recent years, a hologram interferometer for measuring the surface state of an object to be measured by using a computer-synthesized hologram has been put into practical use. Computer-synthesized holograms are formed by applying a photoresist film on a glass substrate and scanning the photoresist film with an electron beam to expose a hologram pattern equivalent to the interference fringes of the object wave and the reference wave, and then exposing the hologram pattern. It is an optical element in which interference fringes are made visible by developing. When the same reproduction wave as the reference wave is incident on the interference fringes in this hologram optical element, the object wave can be reproduced. According to the interferometry method using this hologram, it is possible to inspect and measure a special shape, so that it can be widely used in the future.

[0006]

By the way, as a hologram interferometer apparatus using the interferometer apparatus of FIG. 9 described above,
The applicant has developed the structure shown in FIG.

Also in this hologram interferometer device, the same structure as the device body 1 of the interferometer device described above is used. However, the reference lens 8 according to the lens 9 to be inspected
Is not used. That is, in this hologram interferometer device, the device body 1 from which the reference lens 8 is removed is used as the laser light source 2
And a light source section having an optical path for collimating the laser light from the laser light source 2 and emitting the parallel light flux and for guiding the incident light to the observation mechanism of the interference fringes, and an observing section such as the image pickup means 12. Since the light source / observation unit is used as a mechanism that exhibits the function of the observation unit, the reference numeral 1L will be used in the following description.

By the light source / observation unit 1L, the laser light from the laser light source 2 is emitted by the collimator lens 7 in the form of a parallel light flux. The parallel light is first reflected by the first reflection mirror 20 and then reflected by the second reflection mirror 21, so that the optical path of the laser light is directed upward. And the second reflecting mirror 2
The laser light from No. 1 is once returned by the third reflection mirror 22, and then the laser light returned by the third reflection mirror 22 is reflected by the fourth reflection mirror 23. A hologram optical element 24 is arranged opposite to the fourth reflecting mirror 23. When laser light is incident on the hologram optical element 24, it is divided into specular reflection light and diffracted light. A reference reflection plate 25 having a reference reflection surface 25a perpendicular to the regular reflection light is arranged in the optical path of the regular reflection light.

On the other hand, an object 26 is placed in the optical path of the diffracted light. Here, assuming that the object 26 to be inspected is a cylindrical optical element such as a cylindrical lens or a cylindrical mirror, the hologram pattern of the hologram optical element 24 is a lattice pattern in which parallel holograms are arranged. Then, the grating direction of the hologram optical element 24 is set to the object 2
6 toward the generatrix direction of the cylindrical surface 26a,
Moreover, it is arranged at a position where the diffracted light is condensed on the central axis.

With the above-described structure, the laser light flux from the laser light source 2 in the light source / observation unit 1L passes through the diverging lens 4 and the pinhole 5 forming the optical system for light transmission, and then the beam splitter. After being reflected by 6 and made into a parallel light flux by the collimator lens 7,
The light enters the hologram optical element 24 via the first to fourth reflection mirrors 20 to 23. Then, the diffracted light emitted from the hologram optical element 24 is once condensed at a position on the central axis of the test surface 26a formed of the cylindrical surface of the test object 26, and then diverges and is irradiated onto the test surface 26a. , Is reflected by the surface to be inspected 26a and returns to the hologram optical element 24.
The return light from the test object 26 is the hologram optical element 24.
The light is reflected by and becomes the original parallel light, and goes to the collimator lens 7. On the other hand, the regular reflection light from the hologram optical element 24 is reflected by the reference reflection surface 25 a of the reference reflection plate 25, and the return light is reflected again by the hologram optical element 24 and travels toward the collimator lens 7.

Therefore, the object wave light due to the pattern of the hologram optical element 24 overlaps with the reference wave light from the standard reflection plate 25 and exerts an interference action with each other to form interference fringes. This light is transmitted through the beam splitter 6, and an interference fringe is imaged on an image forming surface of the image pickup means 12 via an interference fringe image forming imaging lens 11 provided at a rear focal position of the collimator lens 7. Here, by the action of the hologram optical element 24, the plane wave and the test surface 26a of the test object 26 are measured.
Is converted into an aspherical wave and the interference fringes are generated as a result of the interference between the parallel lights, so that an extremely clear interference fringe pattern is imaged by the imaging means 12. Therefore, the shape of the test surface 26a can be measured with extremely high accuracy.

In order to obtain an interference fringe image formed on the image pickup means 12 clearly and in a clear state without noise, it is necessary to avoid the influence of outside light as much as possible. However, since it is necessary to sequentially replace and mount the test object 26, the site where the test object 26 is set must be kept exposed to the outside. Therefore, it is preferable to cover the optical path with a housing or the like except for a small portion from the hologram optical element to the object to be inspected. Moreover, the housing is required to be formed as small as possible from the viewpoint of miniaturization and compactness of the device configuration.

By the way, the hologram optical element is formed by forming a hologram pattern on a transparent plate such as glass, and this hologram pattern reflects the light incident thereon, but the pattern is not formed. Light is transmitted through the part. Normally, the surface opposite to the surface on which the hologram pattern is formed is provided with an antireflection type light absorbing layer which is a coating that prevents reflection of light and absorbs light. However, some light passes through the antireflection light absorption layer. here,
The prior art does not have a mechanism for controlling the light transmitted through the hologram optical element.
For example, the reflected light is reflected on the inner surface of the housing for blocking the optical path from the outside, and the reflected light enters the optical path as harmful light, which causes ghosts, etc. Accurate measurement of objects may not be possible.

The present invention has been made in view of the above points, and its object is to reliably absorb the light transmitted through the hologram optical element and render it harmless.

[0015]

In order to achieve the above-mentioned object, the present invention provides a laser beam from a laser light source which is collimated and emitted, and the laser beam is incident on a hologram optical element for regular reflection. Light is divided into light and diffracted light, and the specularly reflected light is applied to the reference reflector and the diffracted light is applied to the test object to generate object light and reference light, and between these two wavefronts. A method for measuring the surface condition of a test object based on the generated interference fringes, wherein the hologram optical element is fixedly mounted on a frame-shaped cassette body, and the hologram optical element is opposite to the surface on which the hologram pattern is formed. The antireflection type light absorbing layer forming surface formed of a coating that prevents reflection and exhibits a light absorbing function is provided on the side surface, and the cassette body faces the antireflection type light absorbing layer forming surface of the hologram optical element. To do It has a light absorption function, and is to its characterized in that the light has a structure for attaching the lid to form a light-absorbing diffusion surface having a diffusion function.

[0016]

The laser light from the laser light source is collimated and enters the hologram optical element, and a part of the hologram pattern forming surface of the hologram optical element passes through this surface. This transmitted light is prevented from being directly reflected and absorbed by the antireflection type light absorption layer provided on the opposite surface. However, light cannot be completely absorbed by the antireflection type light absorption layer forming surface, and the light is transmitted to the antireflection type light absorption layer forming surface to some extent. The light transmitted through the antireflection type light absorption layer forming surface hits the lid body, and the surface of the lid body facing the hologram optical element has a light absorption function and is a light absorption diffusion surface for diffusing the light. Therefore, most of the light that has passed through the antireflection type light absorption layer forming surface is absorbed by this light absorbing and diffusing surface, and even if reflected on this surface, it is diffusely reflected and diffused almost uniformly, resulting in interference fringes. It is rendered harmless to images.

Thus, in the hologram optical element, only the hologram pattern forming surface is exposed to the outside, and the other side surfaces and the antireflection type light absorbing layer forming surface are covered by the cassette body and the lid. Therefore, there is no inconvenience such as scratches, dirt, dust, etc. In particular, when the hologram optical element is exchanged and used according to the object to be inspected, if the hologram optical element is covered with a lid, the handling becomes extremely easy and the surface of the hologram optical element is damaged during attachment / detachment. There is no danger of it becoming dirty or soiled.

[0018]

Embodiments of the present invention will now be described in detail with reference to the drawings. 1 is an exploded perspective view of the hologram cassette, FIG. 2 is a plan view of the assembled state, FIG. 3 is a sectional view of the assembled state, FIG. 4 is a plan view of the holder member, and FIG. 5 is a front view thereof. Are shown respectively. Furthermore, FIG.
Shows a front view of a state in which a hologram cassette is mounted on a holder member. In these figures, 30 is a hologram cassette, and 50 is a holder member.

The hologram cassette 30 is provided with a frame-shaped cassette body 31 and a lid 32. The cassette body 31 is made of a frame-shaped member and has an opening 31.
The hologram optical element 34 is attached to a. This hologram optical element 34 is provided with an opening 31a.
In order to maintain the state of being mounted inside, the inwardly projecting receiving portion 31b is formed over the entire circumference, and the hologram optical element 34 is mounted at four corners. Notch 3 to facilitate the
1c is formed.

The hologram optical element 34 serves as a hologram pattern forming surface 34a on one side of which a hologram pattern equivalent to the interference fringes generated between the object wave and the reference wave according to the surface shape of the object is formed. Further, an antireflection type light absorption layer forming surface 34b is provided on the opposite side surface thereof with a coating for preventing reflection and absorbing light. The hologram optical element 34 has a considerable thickness so as not to be deformed or distorted by heat or external force. When mounting the hologram optical element 34 on the cassette body 31, the receiving portion 31 having the hologram pattern forming surface 34a as a reference surface is used.
It is arranged so as to be accommodated in the state of being directed to the b side, and is fixed to the receiving portion 31b with an adhesive. And
In a state where the hologram optical element 34 is incorporated in the cassette body 31, the lid body 32 is brought into contact with the cassette body 31 and the screws 35 are fastened to the four corners to assemble the hologram cassette 30. It

The hologram cassette 30 thus assembled is detachably attached to the holder member 50. The holder member 50 includes, for example, a support portion 51 fixed to a housing of the interferometer unit.
The frame body portion 52 is continuously connected to the. The hologram cassette 30 is joined to the upper part of the frame body portion 52 and fixed by using a pair of bolts 53, 53 provided at the front and rear.

Here, the hologram optical element 34 must be accurately positioned in the cassette body 31, but the hologram optical element 34 has its hologram pattern forming surface 34a directly contacting the receiving portion 31b of the cassette body 31. Therefore, by processing the receiving portion 31b so as to be accurately flat to form a reference surface,
It is possible to fix the hologram optical element 34 in a state in which there is no inclination and the flatness is accurately obtained. On the other hand, in order to accurately determine the horizontal position, the inner peripheral wall 31 of the opening 31a is
d is used as a positioning wall.

Then, the hologram cassette 30 is joined to the frame body portion 52 of the holder member 50, and the bolts 53 are inserted through the insertion holes 36 provided in the hologram cassette 30 to form the frame body portion 52. Screw hole 5
The hologram cassette 30 is fixedly connected to the holder member 50 by being screwed into the holder 4. At this time, in order to adjust the position of the hologram cassette 30, positioning pins 55, 55 are projectingly provided on the left and right parts of the frame body portion 52, and the positioning pins are provided on the hologram cassette 30 side. A pin insertion hole 37 into which 55 is fitted is formed.

When the hologram optical element 34 is mounted in a position displaced from the hologram cassette 30, a position correcting mechanism is provided. This misregistration correction mechanism has the configuration shown in FIGS. 7 and 8. That is, the bottom surface of the cassette body 31 is provided with a position adjusting recess 38, and an adjusting plate 39 is fitted into the position adjusting recess 38. Then, the pin insertion hole 37 as the above-mentioned cassette side positioning portion is formed in the adjustment plate 39. In addition, the adjustment plate 39
The screw holes 40, 40 are formed on both sides of the pin insertion hole 37. Further, the cassette body 31 is provided with screw insertion holes 41, 41, and the upper surface side thereof is provided with screw accommodating recesses 43, 43 for accommodating the plate fixing screws 42, 42. Plate fixing screw 4
The second head does not protrude from the upper surface of the cassette body 31. The plate fixing screw 42 is inserted from the screw accommodating recess 43 side into the screw insertion hole 41, and is screwed into the screw hole 40 of the adjusting plate 39 fitted in the position adjusting recess 38, whereby the adjusting plate 39 is removed. The position adjusting recess 38 is fixed so as to be in pressure contact with the inner surface of the position adjusting recess 38.

The hole diameter of the screw insertion hole 41 is formed larger than the outer diameter of the plate fixing screw 42, and the outer dimension of the adjusting plate 39 is smaller than that of the position adjusting recess 38. When it is fitted into the position adjusting recess 38, it can be moved forward and backward and left and right by a predetermined amount. However, adjustment plate 3
The thickness of 9 is the same as or thinner than the depth of the position adjusting recess 38. By moving the adjusting plate 39 in an arbitrary direction, the position of the pin insertion hole 37 into which the positioning pin 55 provided in the frame portion 53 of the holder member 50 is inserted can be adjusted. Moreover, the hole diameter of the insertion hole 36 is also larger than the outer diameter of the bolt 53, so that the hologram cassette 30 itself is held by the holder member 5.
It can be fixed even if it is slightly displaced from 0. A pad 44 made of a flexible material such as moltoprene is fixedly provided on the inner surface of the lid body 32. When the lid body 32 is attached to the cassette body 31, the pad 44 is attached to the hologram optical element 34. It is adapted to be pressed by the receiving portion 31b.

With the above structure, the hologram cassette 30 to which the hologram optical element 34 suitable for measuring the surface condition of the object to be measured is attached is simply attached to the holder member 50. , Different types of test objects such as spherical lenses, aspherical lenses, precision optical elements such as cylindrical lenses and mirrors, and test objects of the same type have different radii of curvature and effective diameters. It becomes possible to measure things. Therefore, by replacing the hologram cassette 30 according to the object to be inspected,
It is possible to accurately measure the surface condition of various test objects, and each member other than the hologram optical element 34 can be commonly used for measuring various test objects.

As described with reference to FIG. 10, the hologram optical element 34 is adapted to collimate the laser beam and irradiate it obliquely from below. Then, the hologram pattern forming surface 3 of the hologram optical element 34.
Part of the light incident on 4a is reflected, and part of the light is transmitted to the antireflection light absorption layer forming surface 34b. Here, since the antireflection type light absorption layer forming surface 34b has antireflection and light absorption functions, not only is there a possibility that the transmitted light will not return to the reflected light path direction, but most of the antireflection type light absorption layer does not absorb light. It will be absorbed by the layer forming surface 34b. However, it is not completely absorbed even by this antireflection type light absorption layer forming surface 34b, and also passes through this antireflection type light absorption layer forming surface 34b to some extent. When the light passing through the antireflection type light absorption layer forming surface 34b enters the optical path, the image quality of the interference fringe image is deteriorated due to the generation of ghosts and the like.

In consideration of the above, in the present invention, the lid 32 is provided in order to prevent the transmitted light from the antireflection type light absorption layer forming surface 34b of the hologram optical element 34 from being emitted to the outside. The lid 32 is provided on the antireflection light absorption layer forming surface 34b of the hologram optical element 34.
Is fixed to the cassette body 31 so as to face each other with a predetermined gap therebetween. Therefore, the light that has passed through the antireflection light absorption layer forming surface 34b does not go out of the hologram cassette 30. However, when reflected on the inner surface of the lid 32, it is reflected on the hologram optical element 34 side. Therefore, the inner surface of the lid 32 is coated with, for example, black paint so as to have a light absorbing function. Moreover, after the coating material is applied in this manner, it becomes a diffusing surface that is made satinized by means such as sand blasting, and even if it is reflected, it becomes a light absorbing and diffusing surface 32a that diffuses and diffuses. ing.

In this way, by making the inner surface of the lid 32 the light absorption / diffusion surface 32a, the hologram optical element 34 is formed.
Even if the light passes through the antireflection type light absorption layer forming surface 34b, it is absorbed by the light absorption / diffusion surface 32a. Even if the light absorption / diffusion surface 32a is not completely absorbed, the reflected light is not harmonized by regular reflection but diffused by diffuse reflection, so that the interference fringe image is rendered harmless.

Moreover, the hologram optical element 34 must be provided so as to face the object to be inspected, and when the object to be inspected is mounted on the sample table, the hologram optical element 34 is provided.
Is mounted so that the hologram pattern forming surface 34a faces downward, and the antireflection type light absorbing layer forming surface 34b faces upward, but the antireflection type light absorbing layer forming surface 34b which faces upward in this way is covered. Covering with 32 protects the surface, and there is no possibility that the surface will be scratched or soiled. Further, when the hologram cassette 30 is replaced, the cassette body 31 into which the hologram optical element 34 is fitted and the lid 32 can be gripped by hand, and therefore this replacement work can be performed very easily. It is possible, and as long as a hand, a jig, or the like is not brought into contact with the hologram pattern forming surface 34a, there is no particular problem even if a little care is taken.

[0031]

As described above, according to the present invention, the hologram optical element is fixedly mounted on the frame-shaped cassette body,
The surface of the hologram optical element opposite to the surface on which the hologram pattern is formed prevents reflection, and forms a reflection preventing type light absorbing layer by applying a coating exhibiting a light absorbing function, and the cassette body has Since the lid having the light absorbing function and having the light absorbing / diffusing surface for diffusing light is mounted so as to face the surface provided with the antireflection light absorbing layer, the hologram optical element is Most of the light passing through is absorbed by this light absorption and diffusion surface,
Even if it is reflected, it will be diffusely reflected and diffused almost uniformly, so it is not particularly harmful to the interference fringe itself, and since the hologram optical element is covered with the lid in this way, , Damage this holographic optical element,
It is possible to prevent contamination, adhesion of dust and the like, and it is particularly convenient to handle the hologram optical element when it is replaced according to the object to be inspected.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of a hologram cassette showing an embodiment of the present invention.

FIG. 2 is a plan view of a hologram cassette in an assembled state.

FIG. 3 is a sectional view taken along line XX of FIG.

FIG. 4 is a plan view of a holder member.

FIG. 5 is a front view of FIG.

FIG. 6 is a cross-sectional view of an assembled state of the hologram cassette and the holder member.

FIG. 7 is a structural explanatory view of a positional deviation correction mechanism of a hologram optical element.

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

FIG. 9 is a diagram illustrating the principle of a Fizeau interferometer.

FIG. 10 is a diagram illustrating the principle of a hologram interferometer.

[Explanation of symbols]

 30 hologram cassette 31 cassette body 31a opening 31b receiving portion 32 lid 32a light absorption / diffusion surface 34 hologram optical element 34a hologram pattern formation surface 34b antireflection type light absorption layer formation surface 36 insertion hole 37 pin insertion hole 38 position adjustment recess 39 Adjustment plate 40 Screw hole 41 Fixing screw insertion hole 42 Plate fixing screw 50 Holder member 52 Frame part 53 Bolt 54 Screw hole 55 Positioning pin

Claims (1)

[Claims] 1. A laser beam from a laser light source is collimated and emitted, and the laser beam is incident on a hologram optical element to be separated into specular reflected light and diffracted light, and the specular reflected light is used as a reference reflector. In addition, by irradiating the test object with the diffracted light, the object light and the reference light are generated, and the surface state of the test object is measured based on the interference fringes generated between the two wavefronts. The hologram optical element is fixedly mounted on a frame-shaped cassette main body, and the hologram optical element is made of a coating that prevents reflection on the surface opposite to the surface on which the hologram pattern is formed and exhibits a light absorbing function. The cassette body has a light absorption function and a light diffusion function so as to face the antireflection light absorption layer formation surface of the hologram optical element. Light absorption and diffusion surface A hologram cassette for a hologram interferometer device, characterized in that a lid having the above-mentioned structure is attached.