JPH0554602B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to the setting of a hologram prototype for precisely measuring the surface shape of optical elements such as lenses and mirrors, especially aspherical optical elements, using the hologram prototype. The present invention relates to a method and apparatus therefor.

Prior Art As a method for measuring the surface shape of an aspherical optical element, a hologram prototype created by interference between a reflected or transmitted wavefront from a reference aspherical surface and a reference light wavefront, or optical design values of a reference aspherical surface is used. A so-called "computer-generated hologram", which is created by calculating a hologram pattern using an electronic computer and using an electron beam drawing method, is used as a hologram prototype, and the diffracted light by the hologram prototype of the reflected or transmitted wavefront from the aspherical optical element under test is used as a hologram prototype. A holographic interferometer is known that interferes with a reference beam and precisely measures the error of the aspherical optical element under test from the reference aspherical surface from the amount and shape of interference fringes.

Further, as an interferometer, for example, a Fizeau type interferometer shown in FIG. 22 is known. That is,
The light from the light source (laser) LS is collimated by the collimator lens C. Then, the imaging lens
A part of the light beam reflected by the beam splitter BS, which is a half mirror tilted between _L1 and the diverging lens _L2 , is diverged by the diverging lens _L2 and then reflected by the reference spherical surface R. It is reflected, passes through the same optical path as the incident light (l ₁ ), passes through the beam splitter BS, the hologram prototype H, and the imaging lens L ₁ , becomes the zero-order reference light, and passes through the aperture of the spatial filter SF. .

On the other hand, the light that passes through the reference spherical surface R and is reflected by the optical element to be tested (aspherical concave mirror) T, that is, the object light, travels backwards and passes through the beam splitter BS.
The 0th-order light that passes through the beam splitter BS and is not diffracted by the hologram prototype is cut off by the spatial filter SF, while the 1st-order diffracted light, for example, which is diffracted by the hologram prototype, passes through the aperture of the spatial filter SF and is cut off by the spatial filter SF. Interference fringes are formed on an interference screen or film with the zero-order reference light.

Problems to be Solved by the Present Invention In the above-mentioned holographic interferometer, in order to accurately measure the test object, the hologram prototype is
It is a prerequisite that they be accurately relocated to the reference placement position that served as the reference for their creation. This placement error of the hologram prototype directly leads to measurement errors and a reduction in measurement accuracy of the holographic interferometer.

Conventionally, the setting adjustment for this hologram prototype involves holding the test object and hologram prototype in a predetermined holder, then observing the interference fringes that occur and finely adjusting the positions of both to minimize the interference fringes. A method of adjustment was taken. In this conventional method, the setting work is complicated and takes a long time. In addition, in order to use this method, the manufacturing precision of the test object itself is required in the first place, but holography is currently the only method to accurately measure whether or not the test object is manufactured with high precision. Since the interferometry method is the only available method, it has been difficult to obtain highly accurate specimens. Furthermore, the conventional method described above is an unconventional method in which the position of the hologram prototype, which is the measurement standard, is determined based on a test object whose precision is unknown.

Purpose of the Invention The present invention has been made in view of the conventional drawbacks, and its purpose is to provide a method for setting a hologram prototype without using a test object for setting the hologram prototype, and an apparatus therefor. There is a particular thing.

Still another object of the present invention is to provide a new setting method and apparatus for setting up a hologram prototype in a simple and short time.

Structure of the Invention The present invention includes a first step of adjusting the optical axis of a collimator lens so that the optical axis of the reference lens coincides with the optical axis of the reference lens. and a second step of arranging the aspherical wave generating optical surface so that the center of curvature coincides with the focal point of the reference lens, and separating the aspherical wave generating optical surface from the spherical wave generating optical surface by a predetermined distance in the optical axis direction. a third stage of arranging interference fringes between a diffracted wavefront by the hologram prototype of one of the aspherical wave and reference wave from the aspherical wave generation optical surface and a non-diffracted wavefront by the other hologram prototype; A hologram prototype having an intensity pattern that becomes zero when is placed at a predetermined position,
The hologram prototype setting method includes a fourth step of arranging the diffracted wavefront and the non-diffracted wavefront so that interference fringes become zero.

The present invention also provides an optical axis of a collimator lens,
a reference lens positioning means for adjusting the optical axis of the reference lens so that the optical axis coincides with the optical axis of the reference lens, and the center of curvature thereof coincides with the focal point of the reference lens; an optical surface for generating a spherical wave disposed, an optical surface for generating an aspherical wave disposed at a predetermined distance from the optical surface for generating a spherical wave along the optical axis direction, and an optical surface for generating an aspherical wave disposed from the optical surface for generating a spherical wave. a hologram prototype having an intensity pattern in which interference fringes between the diffracted wavefront of one of the aspherical waves and the reference light wave and the non-diffracted wavefront of the other become zero when placed at a predetermined position; an observation optical system for observing interference fringes between a diffracted wavefront of either an aspherical wave from an optical surface for use and a reference light wave by a hologram prototype, and a non-diffracted wavefront by the other hologram prototype; This is a hologram prototype setting device characterized by comprising a hologram prototype holder for holding the prototype.

Effects of the Invention According to the present invention, since the test object is not used for setting the hologram standard as in the past, it is possible to perform positioning with high precision, and the work is simple and easy. The configuration of the setting device is also simple.

Embodiments Hereinafter, embodiments of a holographic interferometer including a holographic prototype setting device according to the present invention will be described in detail.

A. Overall optical configuration FIG. 1 shows an overall diagram of the optical configuration of a holographic interferometer including the setting device for the hologram prototype according to the present invention. Laser 1 as a light source
The light from 01 has its optical path changed by mirrors 102a and 102b, and then is condensed by a condenser lens 103. There is a pinhole 10 near this focal point.
A pinhole reticle plate 104 having a diameter of 4a is arranged. The diverging light passing through the pinhole 104a acts as if the pinhole 104a were a secondary light source. Note that mirrors 102a and 102b
A quarter wavelength plate 105 is arranged between them.

A collimator lens 106 is arranged so that its focal point is located at the pinhole 104a.
The pinhole 104a serves as a secondary light source, and the light beam emitted from the pinhole 104a is made into a parallel light beam by the collimator lens 106. A reference plane plate 107 is arranged behind the collimator lens 106. This reference plane plate 107 is the front plane 10
7a is arranged perpendicular to the apparatus optical axis (collimator optical axis) ₀₁ . Further, the rear plane 107b is inclined at a small angle with respect to the front plane 107a, so that interference light between the light reflected from the front plane 107a and the light reflected from the rear plane 107b does not affect the measurement. It's summery.

When the test object T is a concave object such as an aspherical concave mirror, a reference lens 109 is attached to the apparatus lens barrel 108 and arranged behind the reference plane plate 107 . The parallel light beam transmitted through the reference plane plate 107 becomes a convergent light beam, and after converging once at point P,
It becomes diverging light again and hits the object to be inspected, for example, an aspherical concave mirror T.
incident on .

The object light reflected from the test object T and the reference light reflected from the front plane 107a of the reference plane plate 107 are connected to the half mirror surface 110 between the pinhole reticle plate 104 and the collimator lens 106.
a is incident on a prism type beam splitter 110 tilted with respect to the optical axis _O1 . Both the object light and the reference light are reflected by the half mirror surface 110a and enter a hologram prototype 300 supported by a hologram prototype holder 200, which will be described later.

Laser 101, mirrors 102a, 102b, 1/
4-wave plate 105, pinhole reticle 104, zoom splitter 110, collimator lens 10
6. The reference flat plate 107, the reference lens 109, the test object T, and the hologram prototype holder 200 are installed on one common optical bench 100.

The light transmitted through the hologram prototype 300 is imaged on a spatial filter 113 via an imaging lens 111 and a half mirror 112. This spatial filter 113 is for selectively extracting only one of the reference light and the object light that was diffracted by the hologram prototype 300 and the other light that was not diffracted by the hologram prototype 300. . To be more specific, as in the conventional Fizeau interferometer shown in FIG. A hologram prototype 30 is created using the reference light and the object light from the test object T.
It selectively extracts only the first-order object system diffracted at zero, and cuts out the diffracted light of the reference light and the zero-order and higher-order diffraction lights of the second and higher orders of the object light.

The object light and reference light selected by the spatial filter 113 are passed through the zoom lens 114 and the half mirror 11.
5 and the TV camera 11 via the imaging lens 116.
An interference pattern between the reference light and the object light is formed on the imaging surface 117a of No. 7. The image captured by the TV camera 117 is sent to an interference pattern analysis device 119 consisting of a monitor television 118 and a personal computer. Note that the reference light and object light that have passed through the half mirror 115 form a similar interference pattern when formed on the imaging surface 117a of the film 120a of the instant development type camera 120.
Record on 0a.

A portion of the light that has passed through the imaging lens 111 is transmitted through a half mirror 112 and is imaged on a reticle plate 121 arranged with the crosshairs aligned with the optical axis.
The image on the reticle plate 121 is captured by a TV camera 123 via a photographing lens 122, and the switching circuit 12
4 on the monitor 118. These reticle plate 121, photographing lens 122, TV camera 123, and monitor 118 are connected to an alignment optical system 1 for setting the object T in the measurement optical path.
Form 25.

Imaging lenses 111, 116, half mirror 11
2,115, spatial filter 113, zoom lens 114, photographic lens 122, TV camera 11
7, 123 and the camera 120 are the optical bench 13
0. This optical bench 130 has an arm that rotates by driving a known micro-feeding mechanism 131 around a point LC that is conjugate with the exit pupil EP of a composite optical system of a collimator lens 106 and a reference lens 109 in order to adjust the off-axis angle described later. 131
It is fixedly installed. Note that when the object to be inspected is a flat object, the reference lens 109 is not necessary, and in this case, the center of rotation LC is set at a position conjugate with the center of the exit pupil of the collimator lens 106.

As described above, since the present holographic interferometer is of the Fizeau type, the number of optical elements can be significantly reduced compared to the Twyman-Green type and Matsuhatsu-Ender type. Furthermore, unlike the conventional Fizeau type interferometer, this interferometer has its beam splitter placed in the diverging beam between the collimator lens and the pinhole 104a. The area of the half mirror surface is 1/4 compared to that of the original.
It can be made as small as possible.

Furthermore, by narrowing the half mirror surface, the beam splitter can be constructed in a prism type, and as will be described later, it is possible to reduce calculation information and drawing information for drawing a hologram pattern. Furthermore, since the beam splitter has become smaller, its manufacturing precision can be significantly improved, and its manufacturing cost can also be reduced.

Furthermore, since the hologram prototype is also arranged within the convergence and reflection beam of the beam splitter, it is possible to reduce the size, reduce costs, and achieve high-precision drawing. This has made it possible to create a holographic interferometer that can measure with high precision even large-diameter test objects and highly aspherical test objects.

B Hologram Prototype Figure 2 is a plan view showing the configuration of the hologram prototype. The hologram prototype 300 has a hologram pattern section 301 made of a computer-generated hologram in the center. Conventional interferometers use mirror-type beam splitters to separate and combine the reference beam and object beam.
In the case of this mirror type beam splitter, if the mirror surface and mirror back surface (half mirror surface) are formed in parallel, the light reflected from each surface will interfere with each other and adversely affect the measurement. The beam splitter had the mirror surface and mirror back surface not parallel to each other but tilted at a slight angle. As a result, the symmetry with respect to the optical axis is disrupted, and conventionally, even in the case of an on-axis hologram prototype, the hologram pattern had to be calculated for all quadrants to obtain drawing data. but,
In this holographic interferometer, the beam splitter 110 is a prism type beam splitter as described above, so symmetry with respect to the optical axis is preserved, and the hologram pattern of the on-axis hologram prototype is a concentric circle pattern. Point symmetry. Therefore, as shown in FIG. 4, the pattern calculation and drawing data calculation are performed as follows:
This is done only for the first quadrant of , and the other (-x, y),
For the second, third, and fourth quadrants of (-x, -y), (x, -y), it is sufficient to simply coordinate transform the data in the first quadrant, reducing calculation costs and calculation time, and rendering Data can be reduced. On the other hand, if the same amount of expense and time as in the past is spent on calculating hologram patterns and creating drawing data, those data can have higher precision.

A cross-shaped distortion test pattern 302 is formed around the hologram pattern section 301, which is drawn at the same time as the hologram pattern is drawn by electron beam scanning. This distortion test pattern is compared with a reference pattern created in advance, and the amount of distortion of the hologram pattern can be tested from the amount of mutual positional deviation.

Further, a black-white ratio test pattern 303 is formed at two locations outside the distortion test pattern. This black-and-white ratio test pattern is, for example, a checkered pattern in which black portions 304 and white portions 305 of the same area are alternately arranged in a plane as shown in FIG. 3.
This black-and-white ratio test pattern 303 is drawn at the same time as the hologram pattern 301 is written with an electron beam, so this black-and-white ratio test pattern 303
By measuring the black and white ratio of the hologram pattern using a densitometer, the black and white ratio of the hologram pattern itself can be indirectly known.

The hologram prototype 300 is placed in a hologram prototype holder 200 at each corner of the hologram prototype 300.
A cross-hair-shaped alignment mark 306 is formed for alignment when attaching to. An L-shaped upper/lower discrimination mark 307 is formed below the two alignment marks on the lower side of the figure.

C Hologram Prototype Holder FIGS. 5 to 7 are diagrams showing the hologram prototype holder 200. A shaft 203 is supported by bearings 201 and 202 placed on the optical bench 100 so as to be slidable in parallel to the optical axis O ₂ (see FIG. 1). The shaft 203 has a screw 204,
A stage 205 moving in the Z-axis direction (optical axis _O2 direction) is fixed by 204. A cylinder 206 is attached to the bearing 201, and a spring 20 is installed in the cylinder 206.
7 is inserted. On the other hand, a Z-axis feed screw 208 is screwed into the bearing 202 . This Z-axis feed screw 208 cooperates with the spring 207 via a steel ball 209 to clamp the Z-axis direction moving stage 205, and by its feeding, the stage 205 is moved back and forth along the Z-axis direction.

Stage surface 20 of Z-axis direction movement stage 205
An XY direction moving stage 211 is placed on 5a via a steel ball 210. This stage 21
On the back side of 1, there are screws 212 as shown in Figure 6.
is implanted, and the Z-axis direction moving stage 205
The rod 21 passed to the rear of the opening 213 formed in
A spring 215 is hung between the 4 and 4. The tensile force of the spring 215 pulls the X-Y direction moving stage 211 toward the stage surface 205a of the Z-axis direction moving stage 205, thereby stabilizing the moving surface.

Further, the Z-axis direction moving stage 205 has two Y-axis feed screws 216, 21, as shown in FIG.
7 and one X-axis feed screw 218 are attached. The side surface of the XY direction moving stage 211 has guides 220 via bearings 219, and these guides 220 are pressed by feed screws 216, 217, 218 via steel balls 221.

The X-Y direction moving stage 211 further has a notch 2 on the side opposite to the mounting position of the X-axis feed screw 218.
It has 22. A resilient body 223 is inserted between the side surface of the notch 222 and the upright piece 224 of the Z-axis direction movement stage 205.

As shown in FIG. 6, the elastic body 223 includes a cylinder 225, a piston 226 inserted into the cylinder, and a spring 227 inserted into the cylinder 225 to constantly apply a pressing force to the piston 226. It consists of

Similarly, the stage 211 has notches 228 and 22
9 are formed facing the Y-axis feed screws 216, 217, and the upright pieces 230, 2 of the stage 205
31 and the sides of these notches, the elastic body 23
2,233 are interposed. Pressure body 232,2
The structure of 33 is the same as that of the elastic body 223 described above.

In the configuration of the hologram prototype holder described above, by feeding the feed screws 216 and 217 in the same direction and by the same amount, the stage 211 can move an amount Y as shown in FIG. 10B. In addition, the feed screw 21
8, the stage 211 moves to the 10th A
The amount of movement X is obtained as shown in the figure. Furthermore, by fixing the feed screws 216 and 218 and feeding only the feed screw 217, as shown in FIG. 10C,
The stage 211 is rotated by a rotation angle θ.

The X-Y direction moving stage 211 has a substantially rectangular opening 235 at its center, and circular openings 236 and 237 at the upper left corner and lower right corner. These circular openings 236 and 237 correspond to an opening 238 formed in the Z-axis direction movement stage 205. A microscope objective lens 240 for observing the alignment mark 304 on the hologram prototype 300 is inserted into the opening 238 .

Further, a circular groove 241 is formed around the opening 235 of the stage 211, and a nozzle 242 of a vacuum pump (not shown) is inserted into the pipe 243.
are connected via. Furthermore stage 211
A guide piece 244 is fixed to the outer surface of the holder.
As a result, the hologram prototype 300 is placed on the stage 211 along the guide piece, and the air in the groove 241 is absorbed by the vacuum pump.
11 at atmospheric pressure.

An arm 246 is attached to the tip of the shaft 203 and the tip of the pole 245 implanted in the stage 205.
247 is attached, and its arm 246,
A light emitting diode 248 and a heat ray absorption filter 249 are housed at the tips of the holograms 247, respectively, and are used to illuminate the alignment marks 304 of the hologram prototype placed on the stage 211.

FIG. 8 is a perspective view schematically showing a hologram prototype alignment optical system 250 attached to the hologram prototype holder 200 having the above-described configuration. The alignment optical system 250 includes the above-mentioned light emitting diode 248 and heat ray absorption filter 24.
9. A first optical path 253 consisting of an objective lens 240, a mirror 251, and a beam splitter 252, a light emitting diode 248, and a heat absorption filter 24
9, a second optical path 255 consisting of an objective lens 240, a mirror 254, and a beam splitter 252; and an eyepiece optical path 256, in which the first optical path 253 and the second optical path 255 are combined by the beam splitter 252.

This eyepiece optical path 256 is connected to reticle plates 257 and 258 that move within a plane (xy plane) perpendicular to the optical axis O ₃ and the eyepiece lens 2 by a known moving means (not shown).
59, and circular indicators 260, 261 as shown in FIG. 9 are formed on the reticle plates 257, 258.

As described above, according to this hologram prototype holder, the X-direction moving stage and the Y-direction moving stage are
These movements in X, Y, and θ can be performed on one stage without using a triple stage structure of a directional movement stage and a θ rotation stage. Further, the configuration thereof is extremely simple, and has the advantage of allowing highly accurate movement control and positioning.

D Measuring device for off-axis quantities Measurement methods using interferometers generally include on-axis measurement methods and off-axis measurement methods.

The on-axis type refers to a measurement type in which the object light from the test object and the reference light from the reference plane are coaxial, and because the spatial frequency of the hologram prototype used for measurement can be lowered, it can also be used for test objects with a large degree of asphericity. It has measurable benefits. However, on the other hand, the diffracted light from the 0th order to the higher order by the hologram prototype is all superimposed on the optical axis, although their focal lengths are different.For example, in order to extract the first order diffracted light, a spatial filter is placed at the focal position. Also, the inside of that filter is 0
A portion of the second and higher order diffraction light also passes through this spatial filter. Therefore, there is a drawback that the central part including the optical axis becomes an unmeasurable part.

On the other hand, with the off-axis type, unlike the on-axis type mentioned above, unmeasurable parts do not occur, but because the spatial frequency of the hologram prototype is higher than that with the on-axis type, it is difficult to manufacture and align the hologram prototype. Due to limitations, for example, only aspherical objects with small degrees of asphericity can be measured.

Furthermore, since the off-axis angle varies depending on the type of object and the amount of asphericity, when creating a hologram prototype, the optimal off-axis angle is determined in advance. Therefore, the holographic interferometer of this embodiment is configured as an interferometer that is capable of both on-axis and off-axis measurements and has a variable off-axis angle.

FIG. 11 is an optical layout diagram schematically showing on-axis measurement and off-axis measurement. For on-axis measurements, the reference plane plate 107 is aligned perpendicular to the optical axis O ₁ of the collimator lens 106 .
An observation optical system for observing the interference pattern between the object light and the reference light, that is, a spatial filter 113, a zoom lens 114, an imaging lens 116, and an imaging tube 1.
17 are arranged on the optical axis _O2 perpendicular to the optical axis _O1 .

A spatial filter 113 is arranged at the focal position of the first-order diffracted light of the diffracted light by the hologram prototype 300 of each of the object light and reference light, and interference fringes between the first-order diffracted light of the object light and reference light are formed. This will be imaged with an image pickup tube or photographed.

On the other hand, in the case of off-axis measurement, the reference plane 107 is rotated by an angle α (this angle α is referred to as an off-axis angle), as shown by a broken line. The observation optical system is rotated by an angle β together with the optical bench 130 about the rotation center LC. Here, the turning angle β is determined as tanβ=2f tanα/L (where f is the focal length of the collimator lens).

As a result, only the 1st-order diffracted light of the object light by the hologram prototype 300 and the 0th-order diffracted light of the reference light pass through the spatial filter 113' (spatial filter 113 during off-axis), and both interference fringes are observed and photographed. It is configured so that it can be done.

The off-axis angle α is such that the reflected light (reference light) from the reference plane passes through the half mirror surface 110a of the beam splitter 110 and is reflected by the pinhole reticle 1.
This can be determined from the imaging position of the image S formed on 04. That is, the amount of deviation between the imaging position and the optical axis O ₁ is proportional to the small off-axis angle α.

FIG. 12 is a plan view showing the structure of the pinhole reticle 104. A pinhole 104a is formed at one end of the reticle 104, and a scale 401 is formed along the longitudinal direction from there to the other end. The scale 401 is graduated according to the amount of deviation of the spot S from the optical axis O ₁ (the center of the pinhole 104a) corresponding to the off-axis angle α, and scale numbers 402 of the off-axis angle are printed below these graduations. There is.

FIG. 13 shows an off-axis angle adjusting microscope 410 used when setting the off-axis angle α.
FIG. The microscope 410 has an objective lens 411, converts light from a scale 401 on the reticle 104 and off-axis angle scale numbers 402 into parallel light, reflects it on a mirror 412, and forms an image on an aperture 414 with an imaging lens. A scale image and an off-axis scale numeral image are observed through the eyepiece 415.

FIG. 14 shows the optical arrangement of the on-axis adjustment microscope 420. The difference in configuration from the off-axis angle adjustment microscope 410 described above is that the mirror 4
12 is changed to a half mirror 421, and there is no objective lens 411, and the condensing lens 103 of the interferometer
The point is that it works together with the imaging lens 413 to form an image.

If the running direction of the scale 401 of the pinhole reticle 104 is made parallel to the rotating direction of the reference flat plate 107, and the spot S is projected with a vertical deviation from the scale 401, the surface of the reference flat plate 107 may be tilted or , since it can be determined that the optical axis O has rotated by _one rotation, these checks can also be made.

E Interferometer adjustment method a) Setup for on-axis measurement type (on-axis type arrangement of measurement optical system) a-1: Adjust the on-axis adjustment microscope 420 as shown by the two-dot chain line in Figure 1. Set it on the optical axis _O1 of the meter lens 106.

a-2: Whether or not the reflected spot image S by the reference flat plate 107 of the light beam transmitted through the half mirror 421 of the microscope 420 and condensed onto the pinhole 104a by the condenser lens 103 is again imaged onto the pinhole 104a. is observed through the eyepiece 415.

The spot light is observed by the eyepiece lens 415 only when the spot S coincides with the pinhole 104a. The reference plane plate 107 is adjusted so that the spot S can be observed through the eyepiece lens 415. When the spot S is observed, the reference plane plate 107 becomes perpendicular to the optical axis _O1 ,
The interferometer will be an on-axis arrangement.

(Setting the adjustment lens) a-3: Switch the changeover switch 124 to set the TV camera 1 of the alignment optical system 125.
The image from 23 is on monitor TV 11.
Set it so that it is projected at 8.

The monitor television 118 has a pinhole 104a from the reference flat plate 107.
The spot image conjugate to is on the reticle plate 12.
The situation matching the intersection of the crosshairs 1 is displayed.

a-4: Reference lens holder 1 having a reference lens 109 in the device lens barrel 108 of the interferometer
09a is attached using a known holding means (not shown).

a-5: The reference plane 502 of the holder 500 having the adjustment mirror 501 is the reference plane 109b of the reference lens holder 109a.
(See Figure 15A)
The holder 500 is attached to the reference lens holder 109a with attachment screws 503.

a-6: Place the autocollimator 510 on the optical bench 100, and align the crosshair target 51 as shown in FIG. 15B.
1 is the circle indication 512a of the reticle 512
The autocollimator 510 is directly opposed to the adjustment mirror 501 so as to coincide with the adjustment mirror 501. Thereafter, this autocollimator 510 is fixed on the optical bench 100 so that it does not move.

a-7: Place the adjustment mirror 501 into the holder 500
Remove the entire reference lens holder 109a from the reference lens holder 109a.

a-8: Known five-axis holder (not shown) (x,
The adjustment lens 520 held in the five axes of y, z, φ _A , φ _B ; φ _A and φ _B indicate horizontal and vertical tilt directions) is placed between the reference lens 109 and the autocollimator 510 . Place it in At this time, as shown in FIG. 15A, the adjustment lens 520 has a spherical surface 52 for generating a spherical wave 520a.
1 curvature center Q ₁ is the reference lens 109
and the plane 522 of the adjustment lens is perpendicular to the optical axis O ₅ of the autocollimator.

This setting of the adjustment lens 520 is performed using the reference light from the reference plane plate 107 projected on the monitor television 118 and the spherical surface 521 of the adjustment lens 520.
Rough positioning is performed by making the interference fringes with the object light (spherical wave) from
11 and the reticle line 512a, precise positioning is performed.

(Setting of adjustment hologram prototype) a-9: Aspherical wave 523 of adjustment lens 520
When the aspherical surface 523 for generating a is located at the above-mentioned setting completion position, an adjustment hologram consisting of an interference pattern generated by interference between the object light from the aspherical surface 523 and the reference light from the reference plane plate 107 is created. A prototype, or an adjustment hologram prototype consisting of a computer-generated hologram obtained by calculating such an interference pattern using a computer and created using an electron beam lithography method based on the calculation result, is placed in the X- It is vacuum-adsorbed onto the stage 211 for moving in the Y direction.

a-10: Switch the changeover switch 124 so that the image of the TV camera 117 of the interference fringe observation optical system is displayed on the monitor TV 118.

a-11: Adjust the feed screws 208, 216, 217, and 218 to remove the adjustment lens 52.
For example, the first-order diffracted light from the hologram standard for adjustment of the object light (aspherical wave) from the aspherical surface 523 of 0, and the reference flat plate 10
The interference fringes in the spatial filter 113 with, for example, the 0th-order diffraction light of the reference light from 7 are made to be one color. As a result, the hologram prototype for adjustment is
Adjustments were made in the Y, Z, and θ directions, and positioning was completed.

(Setting the hologram prototype for measurement) a-12: Adjust the reticle moving knob (not shown) and place it on the alignment mark 306 of the hologram prototype for adjustment that was positioned in step (a-11) above, as shown in FIG. As shown in the example of the observation field of the eyepiece 259 shown in FIG.

a-13: Just in case, autocollimator 510
The user looks through the lens and reconfirms whether the target image 511 and the reticle index 512a match, that is, whether the adjusting lens 520 is correctly positioned.

If the positioning is correct, it is determined that the setting from steps (a-9) to (a-12) was performed correctly,
After this, the autocollimator 510 and adjustment lens 520 are unnecessary, so they are removed.

a-14: The hologram prototype for adjustment is placed on stage 21
1, and a measurement hologram prototype 300 is placed on the stage 21 instead.
1 and vacuum adsorbed.

a-15: While looking through the eyepiece 259 of the hologram prototype holder, look at the circular indicators 260, 2 of the reticles 257, 258 positioned in step (a-12).
Adjust the feed screws 216, 217, and 218 so that the alignment mark 306 of the measurement hologram prototype 300 placed in step (a-14) matches the hologram prototype 61, and move the hologram prototype together with the stage 211. Position.

(Setting the test object) a-16: Place the test object T in a known 6-axis holder (x,
Six axes: y, z, φ _A , φ _B , and θ (θ is rotation around the optical axis) are set.

a-17: Switch the changeover switch 124 to display the image from the television camera 123 of the alignment optical system 125 on the monitor television 11.
8. Reticle plate 1 on the screen of monitor television 118
The holder holding the test object T is adjusted so that the first-order diffracted spot light (usually brighter than the 0th-order diffracted light) from the test surface matches the crosshair image 21 and becomes the smallest spot.

a-18: Next, the changeover switch 124 is switched so that the image from the television camera 117 of the interference fringe observation optical system is sent to the monitor television 118. As a result, the interference fringes are displayed on the monitor television 118, and the holder is finely adjusted so that the direction and pitch of the interference fringes are suitable for measurement.

b) Setup for off-axis measurement type In the case of off-axis measurement type, the work of adjusting the inclination of the reference plane plate 107 is simply added to the above-mentioned on-axis measurement. This tilting operation of the reference plane plate 107 is performed between step (a-15) and step (a-16) of the on-axis setup step described above, that is, after the setting of the hologram prototype for measurement is completed. This work of tilting the reference flat plate is carried out in the following steps.

b-1: Off-axis adjustment microscope 410,
The scale 401 of the pinhole reticle 104 is shown by the two-dot chain line in FIG.
Place it near the position corresponding to the scale number of the desired off-axis angle in front of the
Next, while looking through the eyepiece 415, the microscope is positioned so that the scale line of the desired off-axis angle, for example, 2.5 degrees, is at the center of the field of view.

b-2: Tilt the reference plane plate 107 so that the resulting reflection spot S coincides with the intersection of a desired scale line (for example, a 2.5° scale line). When the tilt adjustment of the reference plane plate 107 is completed, the microscope 410 is removed.

b-3: Switch the changeover switch 124 so that the image of the television camera 123 of the alignment optical system 125 is displayed on the monitor television 118. The micro mechanism 13 is arranged so that the reflected spot image from the reference plane plate 107 matches the intersection of the cross lines of the reticle 121 displayed on the monitor television 118.
0 to rotate the optical bench 130 around the rotation center LD.

Modification of the embodiment (1) Instead of the reference plane plate 107, the reference lens 10
You may use the rearmost surface of 9. In this case, this reference lens can be tilted or decentered to perform off-axis measurements.

(2) Instead of the scale 401 of the pinhole reticle 104 for off-axis angle checking,
As shown in FIG. 16, line sensor 601
Alternatively, the off-axis angle may be adjusted by directly receiving light at the spot S and detecting the off-axis angle from the position of the light-receiving element.

(3) There are many possible variations of the alignment mark 306 and alignment optical system 250 for setting the hologram prototype 300, some of which will be briefly described below.

(3-1) In the example shown in Figure 17, alignment mark 3
The image by the objective lens 240 of 06 is directly received by the area sensor 602, its position is stored as element address information, and adjustment is made so that the alignment mark of the measurement hologram prototype is located at the same element address.

(3-2) The example shown in Figure 18 is the hologram prototype 3
Using the hollow circular mark 606 as the alignment mark 00, the alignment optical system 25
A black circle mark 607 having a negative/positive relationship with this circular mark 606 is arranged on the reticle plates 257 and 258 of 0, and then the light receiving element 60
8 is arranged. As a result, the circular mark 606 of the hologram prototype 300 and the black circle mark 607 of the reticles 257, 258 match, and after setting the adjustment hologram prototype so that the output from the light receiving element 608 becomes zero, the reticles 257, 258 are moved. let The subsequent setting of the measurement hologram prototype is similarly adjusted so that the output from the light receiving element 608 becomes zero.

(3-3) FIG. 19A shows a fine first mark instead of the alignment mark 306 of the hologram prototype 300.
A concentric circle mark 609 is provided, and this first concentric circle mark 609 is provided.
For example, a second concentric circle mark 610 having the same shape as the concentric circle mark 609 of
- A configuration is shown in which the objective lens 240 is installed very close to the Y-direction moving stage 211 so as to be movable within a plane perpendicular to the optical axis of the objective lens 240. The reference plate 608 having the second concentric mark 610 has moire fringes caused by both marks 609 and 610.
11 (see Figure 19B) is moved so that it disappears. Using the adjusted position of the reference plate 608 at this time as a reference, the measurement hologram prototype is positioned so that moire fringes between the first concentric circle mark on the measurement hologram prototype and the second concentric circle mark on the reference plate do not appear. do.

(3-4) The example shown in Figure 20 is the hologram prototype 3
Instead of the 00 alignment mark, it is constructed with a Fresnel lens 620. That is, the light from the light source is received by the 4-split detector 621, and the output from each split element surface is equal.
That is, the detector 621 is moved so that the center of the detector 621 and the optical axis of the Fresnel lens 620 coincide, and the hologram prototype for measurement is set using the moved position as a reference position.

Note that if the Fresnel lens 620 is provided with astigmatism, the deviation of the hologram prototype in the Z-axis, that is, the optical axis direction can also be adjusted by the output difference from each divided element surface of the detector 621.

(4) In setting the adjustment hologram prototype, instead of using the adjustment lens 520 having a spherical surface 521 and an aspheric surface 523, the 21st A.
As shown in FIG. 21B, an adjustment lens 650 having only a spherical surface 521 is used.

That is, first, the above-mentioned step (a-3)
Then execute step (a-8) to obtain the spherical surface 52.
₁ and the focal point F of the reference lens 109
The adjustment lens 65 is aligned so that the plane 522 is perpendicular to the collimator optical axis _O5 .
Set to 0. Next, the adjustment lens 650 is moved backward (or advanced) by a predetermined distance D, as shown in FIG. 21B. As a result, the reflected wavefront from the spherical surface 522 is not a perfect spherical wave, but has an aberration, in other words, it is emitted as an aspherical wave. If the hologram prototype for adjustment is created as an interference pattern between this aspherical wave and the reference light from the reference plane plate, the 21st B.
After moving the adjustment lens 650 as shown in the figure, by performing the steps (a-9) to (a-11) described above using the adjustment hologram prototype, the adjustment hologram prototype can be adjusted. The device can be set correctly, and in turn, the hologram prototype for measurement can be set correctly by steps (a-12) to (a-15).

(5) Although the hologram pattern 301 of the hologram prototype 300 described in detail based on FIGS. 2 and 4 is an amplitude type hologram pattern, the present invention is not limited to this, but a phase type hologram pattern. You may also use

[Brief explanation of the drawing]

Fig. 1 is an optical layout diagram showing the entire holographic interferometer including a setting device for a hologram prototype according to the present invention, Fig. 2 is a plan view showing the configuration of the hologram prototype, and Fig. 3 is a diagram showing the hologram prototype. FIG. 4 is a diagram showing an example of the hologram pattern in its first quadrant, FIG. 5 is a front view of the hologram prototype holder, and FIG. 5 is a cross-sectional view of FIG. 5, FIG. 7 is a cross-sectional view of FIG. 5, FIG. 8 is a perspective optical layout diagram showing the alignment optical system of the hologram prototype holder, and FIG. A diagram showing an example of the eyepiece field of view of the optical system, FIGS. 10A to 10C are schematic diagrams showing the function of the hologram prototype holder, and FIG. 11 is a partial diagram showing the optical arrangement relationship between on-axis measurement and off-axis measurement. Figure 12 is a diagram showing an example of a pinhole reticle, Figure 13 is an optical layout diagram showing the configuration of an off-axis adjustment microscope, Figure 14 is an optical layout diagram showing the configuration of an on-axis adjustment microscope, and Figure 15A. 15B is a diagram showing the arrangement relationship of the reference lens, adjustment mirror, adjustment lens, and autocollimator in order to explain the setting adjustment of the holographic interferometer of the present invention, and FIG. 15B is an eyepiece observation of the autocollimator. A diagram showing an example of the field of view, FIG. 16 is an optical layout diagram showing a modified example of the pinhole reticle, and FIGS. 17 to 20 are diagrams showing modified examples of the positioning mark of the hologram prototype and the alignment optical system, respectively. FIGS. 21A and 21B are diagrams showing another setting method of the hologram prototype for adjustment, and FIG. 22 is an optical layout diagram of a conventional Fizeau type interferometer. 101...Laser, 104...Pinhole reticle, 106...Collimator lens, 107
...Reference plane plate, 109...Reference lens, T...
Test object, 110...Beam splitter, 113...
... Spatial filter, 117, 123 ... Television camera, 200 ... Hologram prototype holder, 20
5...Z-axis direction movement stage, 211...X-Y
Directional movement stage, 208, 216, 217, 2
18...Feed screw, 223, 232, 233...
Elastic body, 215... Spring, 240... Objective lens, 300... Hologram prototype, 301...
Hologram pattern, 302...Distortion inspection pattern, 306...Alignment mark, 303...Black and white ratio inspection pattern, 410...Microscope for off-axis adjustment, 420...Microscope for on-axis adjustment,
501... Adjustment mirror, 520, 650... Adjustment lens, 510... Autocollimator.

Claims (1)

[Claims] 1. A first step of adjusting the optical axis of the collimator lens so that the optical axis of the reference lens coincides with the optical axis of the reference lens. and a second step of arranging the aspherical wave generating optical surface so that the center of curvature coincides with the focal point of the reference lens, and separating the aspherical wave generating optical surface from the spherical wave generating optical surface by a predetermined distance in the optical axis direction. a third stage of arranging interference fringes between a diffracted wavefront by the hologram prototype of one of the aspherical wave and reference wave from the aspherical wave generation optical surface and a non-diffracted wavefront by the other hologram prototype; A hologram prototype having an intensity pattern that becomes zero when is placed at a predetermined position,
A method for setting up a hologram prototype, comprising a fourth step of arranging the diffracted wavefront and the non-diffracted wavefront so that interference fringes become zero. 2. A patent claim characterized in that the spherical wave generating optical surface and the aspherical wave generating optical surface are formed of one optical member, and the second step and the third step are performed simultaneously. A method for setting a hologram prototype according to item 1. 3. The hologram according to claim 1, wherein the aspherical wave generating optical surface is obtained by moving the spherical wave generating optical surface along the optical axis by the predetermined distance. How to set up the prototype. 4. Reference lens positioning means for adjusting the optical axis of the collimator lens and the optical axis of the reference lens to coincide with each other; an optical surface for generating a spherical wave arranged to coincide with the focal point of the reference lens; an optical surface for generating an aspherical wave arranged at a predetermined distance from the optical surface for generating the spherical wave along the optical axis direction; A hologram having an intensity pattern in which interference fringes between a diffracted wavefront of one of the aspherical wave and the reference light wave from the aspherical wave generation optical surface and a non-diffracted wavefront of the other become zero when placed at a predetermined position. Observing interference fringes between a diffracted wavefront by the hologram prototype of one of the aspherical wave and reference light wave from the prototype and the aspherical wave generation optical surface, and a non-diffracted wavefront by the other hologram prototype. A hologram prototype setting device comprising: an observation optical system for holding the hologram prototype; and a hologram prototype holder for holding the hologram prototype. 5. The hologram prototype setting according to claim 4, wherein the spherical wave generation optical surface and the aspherical wave generation optical surface are each formed as an optical surface of one adjustment lens. Device. 6. The spherical wave generating optical surface is also used so that the aspherical wave generating optical surface is obtained by moving the spherical wave generating optical surface by the predetermined distance along the optical axis. A hologram prototype setting device according to claim 4, characterized in that: 7. The adjustment lens further has a plane perpendicular to the optical axis of the spherical wave generating optical surface,
6. The hologram standard setting device according to claim 5, further comprising an autocollimator for arranging the plane perpendicular to the optical axis of the reference lens. 8. The reference lens positioning means is formed on a reference abutment surface formed on a reference lens holder that holds the reference lens, and on a device casing, and the reference abutment surface is brought into contact with the reference lens positioning reference. A hologram prototype setting device according to any one of claims 4 to 7, characterized in that it is constituted by a reference surface that becomes . 9. The reference lens holder removably includes an adjusting reflective member for positioning the autocollimator in order to make the optical axis of the autocollimator parallel to the optical axis of the reference lens. A hologram prototype setting device according to claim 8.