JPH0694432A - Non-contact type shape inspection device - Google Patents

Abstract

PURPOSE:To inspect the shape of a body to be inspected in a non-contact condi tion and also in real time, with a simple method and accurately, by preparing a hologram prototype in a short preparing time and with a minimum equipment, and by using this hologram prototype. CONSTITUTION:A non-contact type shape inspection device is provided with a hologram prototype by which a phase-type grating pattern corresponding to a prescribed line of the hologram of a reference body is formed on an acoustic/ optical diffraction element 37 by changing the electric signal 43 to be input into the acoustic/optical diffraction element 37 for indicating a hologram. A body 35 to be inspected is arranged in front of or behind the hologram prototype. The beam diffracted by the hologram prototype is made incident both on a first diffraction grating 41 and on a second diffration grating 42 that has the same grating direction and has been arranged in the position where the contrast of the interference fringes produced by the first diffraction grating behind thereof becomes maximum. From the pattern of the interference fringes produced behind the second diffraction grating; the strain of the shape of the inspected body with regard to a reference body can be read.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a hologram prototype and a non-contact type shape for inspecting how much the shape of a test object is distorted by using the hologram prototype. Regarding inspection equipment.

[0002]

2. Description of the Related Art As a method of inspecting the shape of an object in such a non-contact manner, for example, "high-precision mirror surface shape measuring method"
In 1988, various methods have already been proposed, as known from the method described in detail in Optronics Inc.). In particular, among them, the method using the computer generated hologram is highly accurate and can be measured in real time, so that it is expected to be put into practical use. In particular, recently, the zone plate 1 which is one of computer generated holograms has been attracting attention as an inspection of the shape of the lens surface having an aspherical shape. FIG. 1 shows a zone plate, which is a type of computer generated hologram, and is often used for inspection of spherical surfaces and aspherical surfaces. Figure 2
This is an example of inspecting an aspherical shape using this zone plate, and the pattern distortion 2 represents the distortion of the shape of the test object with respect to the reference object.

[0003]

However, the methods using these computer generated holograms have some problems. First of all, it is necessary to prepare hologram prototypes for the number of types of test objects. Second, there is a problem that mass production is difficult because the hologram prototype cannot be copied. Thirdly, it takes time to create the hologram prototype, and a special expensive device is required to create the hologram prototype, so that the hologram prototype cannot be easily created. There is a problem that there is not.

For example, there are two typical methods for producing holograms. One is the hologram original X
-Drawing with a Y plotter and reducing this to a photograph. Another method is a method of directly writing on a photoresist or the like with an electron beam exposure apparatus. Although the device required by the former method is an XY plotter, although this has become popular in recent years, the hologram prototype manufactured by this method has a high accuracy due to the accumulation of errors in each process. There is a problem that it is hard to come out. Also, the grating width of the hologram is 0.
A grid with a pitch smaller than 1 mm cannot be created. Therefore, in the method using the plotter, the inspection of the wavefront having the aberration of several tens of wavelengths is the limit. Further, it is a problem that it takes several hours even if the production process is estimated to be small.

On the other hand, the direct writing method using the electron beam exposure apparatus can write up to a minimum grating width of 5 μm. Therefore, it is possible to accurately inspect a wavefront having an aberration of 500 wavelengths or more with this hologram prototype. However, since the electron beam exposure apparatus is expensive and takes a lot of time to create, the method using the electron beam exposure apparatus is not practical considering that the inspection apparatus is used at the production site.

[0006] Therefore, an object of the present invention is to provide a hologram prototype production method capable of producing a hologram prototype with a short production time and minimum equipment.

Another object of the present invention is to provide a non-contact type shape inspection device which can inspect the shape of a test object in a non-contact manner by a simple method using this hologram prototype.

[0008]

SUMMARY OF THE INVENTION In order to solve this problem, the present invention provides a non-contact type shape inspection apparatus for inspecting a distortion of a shape of a test object with respect to a reference object in a non-contact manner in real time. A hologram prototype that forms a phase-type grating pattern corresponding to a predetermined row of the hologram of the reference object on the acousto-optic diffraction element by changing the electric signal input to the diffraction element and displays the hologram, and before or after the hologram prototype. The test object placed, a means for generating interference fringes from the light diffracted by the hologram prototype, and an interval equal to the fringe interval of the interference fringes, arranged so that the grating is parallel to the interference fringes. The configuration in which the distortion of the shape of the test object with respect to the reference object is read from the diffraction grating and the pattern of interference fringes formed by the wavefront that has passed through the diffraction grating is adopted.

[0009]

In the preferred embodiment, a pulsed laser beam is formed from a laser light source, and then a slit-shaped plane wave is made incident on a test object. A hologram prototype including an acousto-optic diffraction element has a phase-type grating pattern corresponding to a row of slit-shaped plane waves of a hologram of a reference object formed by changing an electric signal input thereto. The hologram diffracted light from the hologram prototype is guided to the first diffraction grating. The second diffraction grating is arranged at a position where the direction of the grating is the same as that of the first diffraction grating and the contrast of the interference fringes formed behind by the first diffraction grating is maximized. The distortion of the shape of the test object with respect to the reference object is read from the pattern of the interference fringes generated behind the second diffraction grating.

In a preferred embodiment, the plane wave is incident on the hologram prototype, the hologram diffracted light from the hologram prototype is incident on the test object, and then the first and second holograms are irradiated.
Is incident on the diffraction grating of.

Further, in a preferred embodiment, the hologram diffracted light from the hologram prototype enters the test object through the light deflecting means, and the light deflecting means causes the slit-shaped plane wave to move in the direction perpendicular to the longitudinal direction of the test object. It is projected on all sides. A phase-type grating pattern corresponding to rows in the deflection direction is sequentially formed on the acousto-optic diffraction element according to the light deflection to form the entire pattern of interference fringes, from which the distortion of the shape of the test object with respect to the reference object can be read. It will be possible.

In the preferred embodiment, the hologram diffracted light from the hologram prototype enters the test object via the image plane rotating means. Only the image plane is rotated by the image plane rotating means without changing the optical axis, and the entire pattern of interference fringes is formed.

[0013]

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

First, a method for producing a hologram prototype will be described.

First, the features of the hologram prototype will be described. In the embodiment of the present invention, the acousto-optic diffraction element 3 is used as the hologram prototype. The acousto-optic diffraction element 3 is shown in FIG.
As shown in, a sound wave is incident from the end surface 3 a of the acousto-optic crystal via the electric signal source 4. When sound waves propagate in the acousto-optic diffraction element 3 crystal one after another, a phase-type grating 3d having a spatially different phase is formed in the crystal. Therefore, the required hologram is written in the acousto-optic diffraction element 3 simply by inputting the hologram pattern calculated by the computer in advance to the electric signal of the signal source 4 input into the crystal. As shown in FIG. 3, the width d of the written grating is determined according to the velocity v of the sound wave and the frequency f of the input electric signal, and is expressed by the following equation: d = v / f.

For example, as shown in FIG. 3, an electric input signal 5 that linearly changes from 100 MHz to 50 MHz is input to the acousto-optic diffraction element 3, and the period of this input signal 5 is H / v. Here, H is the effective length of the acousto-optic diffraction element 3. Therefore, for example, the speed of sound waves is 660 m / s
Then, when the input signal of 100 MHz is input, t
The phase type grating pattern having a grating width of 6.6 μm formed at 0 travels upward at the speed of sound v and reaches the upper end of the acousto-optic diffraction element in FIG. 3 at time t1, while the acousto-optic diffraction element 3
Since an input signal of 50 MHz is input to, a phase type grating pattern having a grating width of 13.2 μm is formed at the lower end.

At this time, the acousto-optic diffraction element 3 is shown in FIG.
When the plane wave 6 is incident as shown in FIG. 3, diffracted light is generated according to the phase type grating pattern, and when the first-order diffracted light 7 therein is viewed, a spherical wave substantially condensed at the point O is generated.

In the above example, the frequency of the input signal 5 is linearly reduced with time to form a spherical wave. However, if the electric signal 4 input to the acousto-optic diffraction element 3 is arbitrarily rewritten, it is not limited to a spherical wave. Wavefronts with arbitrary wavefront shapes can be created.

That is, a virtual plane wave is incident on a virtual object whose shape shows a reference value, the wavefront shape of the object reflected light or the object transmitted light at that time is calculated, and the wavefront of this object light becomes the reference light. The virtual plane waves are superposed, and the pattern of the interference fringes generated at this time is obtained by a computer. By inputting a predetermined electric signal into the acousto-optic diffraction element, a phase-type grating pattern corresponding to one row of the interference fringe pattern (corresponding to the row n1 in FIG. 1) is formed in the acousto-optic diffraction element to form a hologram. Display in real time. Furthermore, the electric signal is sequentially changed according to the pattern of each row (n1 ...) Of the interference fringe pattern to form the phase-type grating pattern on each row in the acousto-optic diffraction element and rewrite in real time to realize the entire space of the hologram pattern. Display in time. Where the nr row in FIG. 1 passes through the center of the zone plate,
The pattern corresponding to the radius at that time corresponds to the pattern formed when the input signal 5 is applied to the acousto-optic diffraction element in FIG.

In this way, it is possible to create the hologram prototype in real time with the hologram prototype placed in the measurement system.
Further, since the hologram pattern can be rewritten in real time, various hologram patterns can be displayed in real time with only one acousto-optic diffraction element which is a hologram prototype.

Next, an optical system for inspecting the distortion of the shape of the test object in a non-contact manner using the hologram prototype thus formed will be described.

A general hologram interferometer for this purpose is shown in FIG. Reference numeral 10 denotes a laser light source, and light emitted from this laser light source passes through a beam expander 12 and a collimator lens 13 to become a plane wave. This plane wave is split into two by the beam splitter 14, one of which is
The half mirror 2 which is reflected by the mirror 18 and serves as reference light 19
It is guided to the observation surface 17 via 1. The other light is guided to the test object 15. The test object 15 may be a transmissive object or a reflective object. Here, an example of a transparent object is shown. The plane wave from the beam splitter 14 enters the test object 15, and the light that has passed through the test object 15, that is, the object light 20, enters the hologram prototype 16. Of the light diffracted by the hologram prototype 16, only the first-order diffracted light is guided to the observation surface 17 via the mirror 22 and the half mirror 21.

In the case of an interferometer using an ordinary computer generated hologram, a hologram pattern is calculated in advance from the shape of the reference object, and the same pattern as that is calculated.
Quantize and record. In the recording process, it has recently been common to use an electron beam. Therefore, if the object has the same shape as the reference object, the light diffracted by the hologram prototype 16 becomes a plane wave. On the observation surface, the diffracted light and the reference light overlap each other to form interference fringes. When the shape of the test object is the same as that of the reference object, the interference fringes have a uniform brightness as a whole, and no stripe pattern is observed. On the contrary,
If the number of interference fringes observed is large, the shape of the test object is distorted as compared with the reference shape, and, for example, the pattern as shown in FIG. 2 is observed.

In such an interferometer, the interference fringes cannot be seen only by replacing the hologram prototype 16 with the acousto-optic diffraction element 3 described above. This is because the hologram written in the acousto-optic diffractive element runs through the element at the speed of sound, so that the diffracted light is not stationary, and due to the Doppler shift caused by the movement of the hologram, the diffracted light is acousto-optic. This is because modulation occurs at the same frequency as that input to the diffractive element.
This is shown in FIG. In FIG. 5, w0 is the frequency of the incident light, f is the modulation frequency of the input signal of the acousto-optic diffraction element 3, and this value is equal to the Doppler shift amount of the first-order diffracted light.

As described above, in the configuration of FIG. 4, when the hologram prototype is replaced by the acousto-optic diffraction element, the hologram written in the acousto-optic diffraction element runs through the acousto-optic diffraction element at the speed of sound. Therefore, there is a problem that it is not possible to observe the diffracted image of the stationary hologram, and since the aperture is slit-shaped, the diffracted image from the entire surface can be displayed at the same time as a normal hologram dry plate. There is a problem that you cannot observe.

First, FIG. 6 shows an optical system that solves the problem of hologram movement.

In FIG. 6, reference numeral 31 is a laser light source having a coherent length of at least several cm. The laser light emitted from the laser light source 31 is converted into a laser pulse having a pulse width of about 100 ns by the pulse signal 45 by the optical shutter 32 including an acousto-optic modulator. This laser pulse is incident on the beam expander 33 and the collimator lens 34 and slit-shaped slit light is formed. This slit light is projected on the test object 35 which is a reflective object or a transmissive object. Here, a test object that is a transparent object will be described.

The laser light transmitted through the test object 35 passes through the slit 36 placed at the focus position of the test object and is incident on the acousto-optic diffraction element 37. This acousto-optic diffraction element 3
Reference numeral 7 corresponds to the acousto-optic diffraction element 3 in FIG. 3 and is used as a computer generated hologram. Therefore, the hologram pattern, which has been calculated by a computer in advance, is converted into a signal as a temporal change of the sound wave, and then written into the acousto-optic diffraction element 37 via the signal source 43. This signal source 43 is shown in FIG.
, The frequency f (t) linearly decreases, and the acousto-optic diffraction element 37 is formed with a phase-type grating pattern in which the grating width decreases toward the upper end. Pass through the diffractive element at the speed of sound.

The light diffracted by the hologram written in the acousto-optic diffraction element 37 then passes through the Fourier transform lens 38, the slit 39 and the inverse Fourier transform lens 40, and then the first diffraction grating 41 and the second diffraction grating 41. Interference fringes are formed on the observation surface 46 by being diffracted by the diffraction grating 42, and the pattern of the interference fringes is observed by the monitor 47. The slit 39 is placed at the focal position of the Fourier transform lens 38 and, at the same time, at the focal position of the inverse Fourier transform lens 40.
The purpose of the slit 39 is to pass only the first-order diffracted light of the light diffracted by the acousto-optic diffraction element 37.

The light which has passed through the inverse Fourier transform lens 40 is diffracted by the first diffraction grating 41, ...
Since 0, + 1st order diffracted lights are generated and interfere with each other, very fine interference fringes are generated. The second diffraction grating 42 is placed at a position where the contrast of the interference fringes is maximized. The grating width of the second diffraction grating 42 is the same as the grating width of the first diffraction grating 41. In addition, the first diffraction grating 41
When the wavefront of the light incident on is a plane wave, the width of the interference fringes formed by this grating is equal to the grating width of the first diffraction grating 41 and the grating width of the second diffraction grating 42. Therefore, at this time, the interference fringes of the wavefront that have passed through the second diffraction grating 42 are uniformly bright fringes on the entire observation surface 46. That is, when there is no distortion in the test object, the wavefront of the first-order diffracted light of the hologram prototype of the acousto-optic diffraction element 37 becomes a perfect plane wave, so that no fringe appears on the observation surface 46 and the entire surface has a uniform brightness. It will be Therefore, when the shape of the test object 35 is distorted with respect to the reference object, the wavefront of the first-order diffracted light of the hologram prototype of the acousto-optic diffraction element 37 becomes a distorted wavefront, and the wavefront is distorted according to the distortion amount. Interference fringes appear.

In this optical system, the light incident on the acousto-optic diffraction element 37 is at a specific position in the hologram that moves the acousto-optic diffraction element 37 at the speed of sound by the optical shutter 32 being driven by the pulse signal 45. According to the fact that light is incident only for some time, the same conditions as when the hologram is stationary are created. That is, for example, the pulse 45 is generated at the time of t1 when the frequency of the input signal 44 decreases from f1 of t0 to f0, and H / v is set between t0 and t1 as shown in FIG.
By setting (H is the effective length of the acousto-optic diffraction element, and v is the speed of sound), a pattern of a predetermined line (nr) of the stationary hologram as shown in FIG. 1 can be realized.

Further, in order to completely suppress the Doppler shift caused by the movement of the hologram, the pulse width of the pulsed light needs to be several ns when the moving speed of the hologram is about 600 m / s. It is technically possible to generate a pulse of several ns using an optical shutter or a special laser light source. However, such optical shutters and pulsed laser light sources are very expensive and have not reached a practical level. Therefore, the pulse generated by the above optical shutter is limited to 100 ns level at the most. However, 100
The pulse of ns cannot suppress the Doppler shift naturally.

If the wavefront on which the Doppler shift has occurred and the wavefront on which the Doppler shift has not occurred are overlapped, the interference fringes themselves are modulated, and the interference fringes cannot be seen as stopped. So with this optical system, even if there is a Doppler shift,
It became possible to stop the interference fringes by overlapping the wavefronts with Doppler shift.

The above description is of the order of correcting the wavefront of the light passing through the test object with the hologram prototype.
This need not be limited to this order. That is, FIG.
The optical system shown in FIG. That is, the hologram prototype 37
A plane wave is incident on the first object and the first-order diffracted light of the hologram is incident on the test object 37. If the test object has the same shape as the reference object and is distorted, the transmitted light or reflected light of the test object becomes a plane wave. The same interferometer as shown in FIG. 6 is used as the means for determining whether or not it is a plane wave.

Further, in the above-mentioned embodiment, since the opening of the acousto-optic diffraction element has a slit shape, only one line of a normal hologram pattern can be displayed. There are roughly two ways to improve it.

One of them is a method of expanding an observation area by scanning using a light deflecting means such as a galvano mirror.
An example thereof is shown in FIG. In FIG. 8, a laser light source 51
The emitted laser light is converted into pulsed light by the optical shutter 52, and the cylindrical beam expander 5
3. The light enters the acousto-optic diffraction element (hologram prototype) 55 through the cylindrical collimating lens 54. The light diffracted by the acousto-optic diffraction element 55 passes through the cylindrical lens 56 and the galvano mirror 57, is incident on the test object 58, and reaches the interferometer 59. This interferometer corresponds to the interferometer shown in FIG.

In FIG. 8, a slit-shaped galvanometer mirror 57 is arranged at the point where the first-order diffracted light of the acousto-optic diffraction element 55 is condensed. The light reflected by the galvanometer mirror 57 is
It is deflected according to the rotation of the galvanometer mirror. Since the slit light is deflected in the direction perpendicular to the longitudinal direction, the test object 5
8 is projected in order from the top according to the slit light. The acousto-optic diffractive element 55 according to the position where the test object 58 is projected
Rewrite the hologram pattern to write to. That is, the galvano mirror 57 is deflected by the drive source 70, and the slit-shaped plane wave is projected on all the surfaces of the test object in the direction perpendicular to the longitudinal direction. Phase-type grating patterns corresponding to the rows in the deflection direction are sequentially formed in the acousto-optic diffraction element by changing the electric signal 71 according to the optical deflection.

Therefore, as shown in FIG. 9, when viewed on the observation surface, the interference fringes 60 appear one by one in the x direction in the y direction. When the rotation of the galvanometer mirror is fast, the interference fringes appear continuously one row at a time, so that it appears as if all the interference fringes 61 shown by the dotted line appear on the observation surface of the interferometer at the same time.

The second method is an example in which an image plane rotating prism is used as shown in FIG. In FIG.
The same elements as those of 1 are denoted by the same reference numerals, and the description thereof will be omitted. As shown in FIG. 10, an image plane rotation prism 67 is arranged in the optical path of the diffracted light of the acousto-optic diffraction element 55.
When this prism is rotated, the image of the emitted light rotates.
When the center of rotation coincides with the optical axis, it is not necessary to rewrite the hologram content to be written in the acousto-optic diffraction element. Therefore, on the observation surface of the interferometer, as shown in FIG. 11, the interference fringes 72 in a predetermined row rotate around the optical axis, and the entire pattern thereof is observed as 73.

[0040]

As described above, according to the present invention, it is possible to create a hologram prototype with a short production time and a minimum of equipment, and a simple method using this hologram prototype can be used. It is possible to accurately inspect the shape of the test object in a non-contact manner in real time.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a zone plate which is a type of computer generated hologram.

2 is an explanatory diagram of an example in which an aspherical surface shape is inspected using the zone plate of FIG.

FIG. 3 is an explanatory diagram illustrating a principle of forming a phase type grating pattern on an acousto-optic diffraction element.

FIG. 4 is a configuration diagram showing a general configuration of an interferometer using a hologram prototype.

FIG. 5 is an explanatory diagram illustrating a Doppler shift of first-order diffracted light.

FIG. 6 is a configuration diagram showing a first embodiment of an interferometer using an acousto-optic diffraction element as a hologram prototype.

FIG. 7 is a configuration diagram showing a second embodiment of an interferometer using an acousto-optic diffraction element as a hologram prototype.

FIG. 8A is a top view of a first embodiment in which an interferometer in which an acousto-optic diffraction element is used as a hologram prototype is used to inspect all regions of a test object, and FIG. 8B is a side view thereof.

9 is an explanatory diagram illustrating an interference fringe pattern observed with the configuration of FIG.

FIG. 10 is a configuration diagram showing a second embodiment in which the entire area of a test object is inspected by an interferometer using an acousto-optic diffraction element as a hologram prototype.

11 is an explanatory diagram illustrating an interference fringe pattern observed with the configuration of FIG.

[Explanation of symbols]

 3 Acousto-Optical Diffraction Element 15 Test Object 16 Hologram Prototype 35 Test Object 37 Acousto-Optical Diffraction Elements 41, 42 Diffraction Grating 55 Acousto-Optical Diffraction Element 57 Galvano Mirror 58 Test Object 67 Image Surface Rotating Prism

Claims (15)

[Claims] 1. A non-contact type shape inspection apparatus for inspecting a distortion of a shape of a test object with respect to a reference object in a non-contact manner in real time, wherein a reference object of the reference object is changed by changing an electric signal input to an acousto-optic diffraction element. A hologram prototype that forms a phase-type grating pattern corresponding to a predetermined row of a hologram on an acousto-optic diffraction element and displays a hologram, a test object placed in front of or behind the hologram prototype, and from the light diffracted by the hologram prototype Means for generating interference fringes, a diffraction grating having an interval equal to the fringe interval of the interference fringes, the grating being arranged parallel to the interference fringes, and an interference created by the wavefront passing through the diffraction grating A non-contact type shape inspection device characterized by reading a distortion of a shape of a test object with respect to a reference object from a stripe pattern. 2. A non-contact type shape inspection apparatus for inspecting a distortion of a shape of a test object with respect to a reference object in a non-contact manner in real time, a laser light source, and means for forming pulsed laser light from the laser light source, Optical means for converting a pulsed laser beam into a slit-shaped plane wave and making it incident on the test object, and a phase corresponding to the line of the slit-shaped plane wave of the hologram of the reference object by changing the electric signal input to the acousto-optic diffraction element. A hologram prototype for forming a hologram by displaying a type grating pattern on an acousto-optic diffraction element, an optical means for making the object light transmitted or reflected by a test object incident on the hologram prototype, and receiving hologram diffracted light from the hologram prototype First to do
And a second diffraction grating arranged in a position where the direction of the grating is the same as that of the first diffraction grating and the contrast of interference fringes formed behind by the first diffraction grating is maximized. The non-contact type shape inspection device, which reads the distortion of the shape of the test object with respect to the reference object from the pattern of interference fringes generated behind the diffraction grating. 3. One of the lights diffracted by the hologram prototype
The non-contact type shape inspection apparatus according to claim 2, wherein a slit is arranged at a condensing point of the first-order diffracted light in order to observe only the second-order diffracted light. 4. The non-contact type shape inspection device according to claim 2, wherein the means for forming the pulsed laser light from the laser light source is an acousto-optic modulator. 5. A means for monitoring the pattern of interference fringes is provided, according to any one of claims 2 to 4.
The non-contact type shape inspection device described in the item. 6. A non-contact type shape inspection apparatus for inspecting a distortion of a shape of a test object with respect to a reference object in a non-contact manner in real time, a laser light source, and means for forming pulsed laser light from the laser light source. Optical means for converting a pulsed laser beam into a slit-shaped plane wave, and a phase-type grating corresponding to a row in the direction of the slit-shaped plane wave of a hologram of a reference object by changing an electric signal input to an acousto-optic diffraction element A hologram prototype for forming a pattern on an acousto-optic diffraction element for hologram display, an optical means for causing the plane wave to enter the hologram prototype, a means for causing the hologram diffracted light from the hologram prototype to enter the test object, and the test object The first diffraction grating that receives the transmitted or reflected light, and the first diffraction grating having the same grating direction as the first diffraction grating Therefore, it is composed of the second diffraction grating arranged at the position where the contrast of the interference fringes formed behind is maximum, and the distortion of the shape of the test object with respect to the reference object from the pattern of the interference fringes generated behind the second diffraction grating. A non-contact type shape inspection device characterized by reading. 7. One of the lights diffracted by the hologram prototype
The non-contact type shape inspection device according to claim 6, wherein a slit is arranged at a condensing point of the first-order diffracted light in order to observe only the second-order diffracted light. 8. The non-contact type shape inspection apparatus according to claim 6, wherein the means for forming pulsed laser light from the laser light source is an acousto-optic modulator. 9. A device according to claim 6, further comprising means for monitoring a pattern of interference fringes.
The non-contact type shape inspection device described in the item. 10. A non-contact type shape inspection apparatus for inspecting a distortion of a shape of a test object with respect to a reference object in a non-contact manner in real time, a laser light source, and means for forming pulsed laser light from the laser light source. Optical means for converting a pulsed laser beam into a slit-shaped plane wave, and a phase-type grating corresponding to a row in the direction of the slit-shaped plane wave of a hologram of a reference object by changing an electric signal input to an acousto-optic diffraction element A hologram prototype that forms a pattern on an acousto-optic diffraction element and displays a hologram, an optical unit that causes the plane wave to enter the hologram prototype, and a hologram diffracted light from the hologram prototype that enters the test object through the light deflection unit. Means, a first diffraction grating for receiving light transmitted or reflected by the test object, and the first diffraction grating and the direction of the grating are And a second diffraction grating arranged at a position where the contrast of interference fringes formed behind by the first diffraction grating is maximized, and the slit-shaped plane wave is tested by the light deflecting means in a direction perpendicular to the longitudinal direction. Interference fringes generated behind the second diffraction grating are formed by projecting on all surfaces of the object and sequentially forming phase-type grating patterns corresponding to rows in the deflection direction on the acousto-optic diffraction element according to the light deflection. A non-contact type shape inspection apparatus, which reads the distortion of the shape of a test object with respect to a reference object from all patterns. 11. The non-contact type shape inspection apparatus according to claim 10, wherein the means for forming the pulsed laser light from the laser light source is an acousto-optic modulator. 12. The non-contact type shape inspection apparatus according to claim 10, further comprising means for monitoring a pattern of interference fringes. 13. A non-contact type shape inspection apparatus for inspecting a distortion of a shape of a test object with respect to a reference object in a non-contact manner in real time, a laser light source, and means for forming pulsed laser light from the laser light source. Optical means for converting a pulsed laser beam into a slit-shaped plane wave, and a phase-type grating corresponding to a row in the direction of the slit-shaped plane wave of a hologram of a reference object by changing an electric signal input to an acousto-optic diffraction element A hologram prototype that forms a pattern on an acousto-optic diffraction element and displays a hologram, an optical unit that causes the plane wave to enter the hologram prototype, and a hologram diffracted light from the hologram prototype that enters the test object through an image plane rotating unit. Means, a first diffraction grating for receiving light transmitted or reflected by the test object, and the first diffraction grating and the direction of the grating The second diffraction grating is the same and is arranged at a position where the contrast of interference fringes formed behind by the first diffraction grating is maximized. The image plane rotating means rotates only the image plane without changing the optical axis. A non-contact type shape inspection device characterized by displaying all patterns of interference fringes generated behind the second diffraction grating and reading the distortion of the shape of the test object with respect to the reference object from all the patterns of the interference fringes. 14. The non-contact type shape inspection apparatus according to claim 13, wherein the means for forming pulsed laser light from the laser light source is an acousto-optic modulator. 15. The non-contact type shape inspection apparatus according to claim 13 or 14, further comprising means for monitoring a pattern of interference fringes.