JP3410800B2 - Vibration resistant interferometer - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration resistant interferometer which is not easily affected by external vibration or air disturbance in the vicinity of a subject, and particularly relates to an optical member or the like which requires highly accurate measurement results. The present invention relates to a vibration resistant interferometer suitable for measuring surface shape.

[0002]

2. Description of the Related Art Conventionally, an interferometer has been known as a means for observing interference fringes formed by optical interference and discriminating a fine uneven shape on the surface of an optical member or the like.

With the development of high-precision machining technology in recent years, there is a demand for an interferometer that can be mounted on a machining machine or the like at a machining site to measure the surface to be machined with high precision.

An interferometer mounted on a processing machine or the like at a processing site is easily affected by vibrations of an optical system from the outside, disturbance of air near a surface to be processed, and the like, and can theoretically measure with high accuracy. However, it is difficult to actually obtain highly accurate measurement results unless the influence of these vibrations and air disturbances can be eliminated to reduce the interference fringe disturbance.

Therefore, as an interferometer capable of eliminating the effects of such vibrations and air disturbances, the reference light beam and the object light beam travel in substantially the same system path so as to be similarly affected by the above effects. A so-called common path interferometer, which is designed to substantially cancel a relative phase change of a light beam, has been attracting attention.

FIG. 11 shows a zone plate interferometer which is a typical example of the common path interferometer. That is, in this interferometer, the laser light beam 1 is converged by the lenses 2 and 3 onto the concave surface which is the surface 4a to be inspected of the object 4, and the zone plate 5 is arranged in the optical path of this converged light beam. It is the one. When the laser light beam 1 is incident on the zone plate 5, it is divided into a first light beam diverging from the center of curvature of the surface 4a to be inspected and a second light beam traveling toward the center of the surface of the object to be inspected. The first light flux is reflected by the inspection surface 4a and re-incident on the zone plate 5, the first light flux passes through the zone plate 5 and goes straight, and the second light flux is diffracted by the zone plate 5. Overlap,
After that, it reaches the film surface of the camera 9 through the mirrors 7 and 8 and forms interference fringes according to the uneven shape of the surface 4a to be inspected on the film surface.

Here, the reflected light from the surface to be inspected 4a of the first light flux is as object light, and the surface to be inspected 4a of the second light flux is also.
The reflected light from each functions as a reference light. These two light beams are reflected by the same surface to be inspected 4a, and pass through substantially the same position, so even if external vibrations or air disturbance near the surface to be inspected occur, the position of each light beam will change. Changes in the phase difference are canceled by each other, and a highly accurate measurement result can be obtained from the interference fringe image obtained by the interference of these two light beams.

[0008]

However, in the above zone plate (Fresnel zone plate) interferometer, the shape of the surface to be measured to be measured is restricted.

This zone plate is a transparent glass plate or film in which a large number of concentric circles whose radius is proportional to the square root of the number counted from the center are drawn, and the annular zones formed by these are made transparent and opaque. In the element, generally, this alternating light and dark ring zone is calculated by a computer, drawn by a plotter, and reduced and produced by photographic recording, which is troublesome.

Further, there are many restrictions on the positions where the zone plate and other optical systems are arranged, which complicates the structure of the apparatus.

The present invention has been made in view of the above circumstances, and provides a vibration-resistant interferometer in which there are few restrictions on the shape of the surface to be measured and which has a simple device configuration and is easy to manufacture. The purpose is.

[0012]

A first vibration resistant interferometer of the present invention comprises a light beam emitting means for emitting a coherent light beam, and the coherent light beam as a first light beam and a second light beam. First light beam splitting means for splitting into a light beam, light beam coupler means for synthesizing the first light beam and the second light beam and guiding the combined light beam onto a surface to be inspected of a subject, and the light beam coupler A first light beam having a beam diameter expanded to the light beam coupler means so that a large-diameter light spot is formed on the surface to be detected by the first light beam from the means. An optical system and a second light beam from the light beam coupler means for guiding the second light beam to the light beam coupler means so that a light spot having a small diameter is formed on the surface to be inspected. The optical system and the first part transmitted / reflected from the surface to be inspected Second light beam separating means for separating the object light beam, which is the second light beam, and the reference light beam, which is the second light beam transmitted / reflected from the surface to be inspected, by the second light beam separating means. The object light beam and the reference light beam, which are separated from each other, are overlapped and irradiated, and a screen means is formed to form an interference fringe carrying the unevenness information of the surface to be inspected.

Further, the light beam coupler means may be the second
It may be configured by the same optical member as that of the light beam separating means.

Further, the object light beam and the reference light beam may be combined by the first light beam separating means.

A second vibration resistant interferometer of the present invention is a light beam emitting means for emitting a coherent light beam, and the coherent light beam is split into a first light beam and a second light beam. And a first light beam having a beam diameter expanded so that a large-diameter light spot is formed on the surface to be inspected by the first light beam. It has an optical system that guides it upwards, and a reference surface that is mounted and held in the vicinity of the mounting and holding position of the subject on the base on which the subject is mounted and held and that is irradiated with the second light beam. A reference plate, an object light beam that is the first light beam transmitted / reflected from the surface to be inspected, and a reference light beam that is the second light beam transmitted / reflected from the reference surface are overlapped and irradiated, Screen means for forming interference fringes carrying the unevenness information of the surface to be inspected It is characterized in that it comprises.

Further, a third vibration resistant interferometer of the present invention is a light beam emitting means for emitting a coherent light beam, and the coherent light beam is separated into a first light beam and a second light beam. And a first light beam having a beam diameter expanded so that a large-diameter light spot is formed on the surface to be detected by the first light beam. The first optical system for guiding and the second light beam form a small-diameter light spot on the surface to be inspected, and the second light beam is applied to the surface to be inspected with respect to the first surface. A second optical system that guides the second light beam onto the surface to be inspected so as to be incident and emitted from a direction different from the light beam, and the first light beam transmitted / reflected from the surface to be inspected An object light beam and the second light beam transmitted / reflected from the surface to be inspected That the reference light beam is irradiated on top, is characterized in that a said screen means interference fringes carrying unevenness information of the test surface is formed.

Further, there is provided divergent light conversion means for converting the first light beam into divergent light so that each light beam of the first light beam is vertically incident on each portion of the spherical surface to be inspected. Is also possible.

Further, on the screen means,
It is also possible to provide a phase relationship changing means for changing the phase relationship between the object light beam and the reference light beam.

The light beam coupler means means an element which synthesizes the light beams separated into two systems and emits them in the direction of the surface to be inspected. Specifically, a half mirror, a polarization beam splitter, a diffraction grating. A simple element that has existed in the past, such as.

The zone plate used in the zone plate interferometer separates one light beam into two systems and irradiates the light onto the surface to be inspected, and is not included in the light beam coupler means.

The screen means is not limited to a so-called screen which allows direct visual observation of the interference fringe image, but an interference fringe image on the screen means such as an image receiving surface of a CCD or a film surface of a camera. The thing which can make the said interference fringe visible by giving predetermined post-processing is also included.

Further, the small-diameter light spot means a light spot having a small diameter such that the reference light beam has almost no unevenness information of the surface to be inspected.

[0023]

According to the first vibration resistant interferometer of the present invention, both the first and second light beams formed by separating the coherent light from the light source are irradiated onto the surface to be inspected. Then
A large-diameter light beam spot is formed by the first light beam on the surface to be inspected, and a small-diameter light beam spot is formed by the second light beam, and the reflected light of the first light beam from the surface to be inspected /
An object light beam is formed by the transmitted light, and a reference light beam is formed by the reflected light / transmitted light from the surface to be inspected of the second light beam. That is, since the first light beam is irradiated over a wide area of the surface to be inspected, the reflected light / transmitted light becomes an object light beam carrying unevenness information over a wide area of the surface to be inspected, while Since the second light beam is locally irradiated onto a narrow area of the surface to be inspected, the reflected light / transmitted light functions as a reference light beam having almost no unevenness information.

Therefore, the object light beam and the reference light beam are generated by the same surface to be inspected, and the vibration from the outside is applied to the object or the interferometer to change the distance between the interferometer and the surface to be inspected. Also, the change in the phases of the object light and the reference light is canceled, and the observed interference fringes are not affected by this vibration.

Since the first light beam and the second light beam are combined by the light beam coupler means, they pass through substantially the same position between the light beam coupler means and the surface to be inspected. Since the reference light beam also passes through the substantially same position from the surface to be inspected until it is decomposed by the second light beam separating means, a temperature distribution of air occurs between the interferometer and the surface to be inspected, and air disturbance occurs. Even if it occurs, the change in the phases of the object light and the reference light is canceled, and the observed interference fringes are not affected by the air disturbance.

Further, the first vibration resistant interferometer uses the light beam coupler means to combine the first light beam and the second light beam and emit the combined light beam toward the surface to be inspected.

This light beam coupler means is a simple and inexpensive element that has been used in general optical systems in the past.
The device can be easily manufactured and the cost required for the manufacturing can be reduced.

Further, in the above-mentioned zone plate interferometer using the zone plate, by inserting this zone plate in the optical path, the type and arrangement of other optical members are largely restricted. The type interferometer does not use a special optical element such as a zone plate, and can secure the degree of freedom in the type and arrangement of other optical members.

Further, in this vibration resistant interferometer, not only when the surface to be inspected is a flat surface but also when it is a spherical surface or an aspherical surface, a lens or the like corresponding to the shape is simply inserted at a predetermined position in the optical path. Thus, it is possible to easily obtain an interference fringe corresponding to the surface to be inspected, and it is possible to relax restrictions on an observation target as compared with the zone plate interferometer.

The light beam coupler means and the second
By configuring the light beam separating means of (1) with the same member, the number of parts can be reduced, and further, the device configuration can be simplified and the manufacturing cost can be reduced.

Further, the first light beam separating means makes it easy to set the position of the screen means by synthesizing the object light beam and the reference light beam, and another light for synthesizing these two beams. The number of parts can be reduced as compared with the case where the beam combining means is used.

Further, according to the second and third vibration resistant interferometers of the present invention, the light beam coupler means and the second light beam separating means are unnecessary, so that the vibration resistant interferometer is further improved. The device configuration can be simplified and the number of parts can be reduced. Further, since the first light beam and the second light beam are irradiated on the same surface to be inspected, or on the surface to be inspected and a reference plate mounted and held on a base common to the object to be inspected, As with the first vibration resistant interferometer, it is not affected by external vibration. However, since the common paths of the first light beam and the second light beam, and further the object light beam and the reference light beam are short or almost nonexistent, the surface to be inspected as compared with the first vibration resistant interferometer. It is likely to be affected by the disturbance of air in the vicinity, but in the second vibration resistant interferometer, by arranging the subject and the reference plate in a close position, and in the third vibration resistant interferometer. Is the first
By making the incident angles of the second light beam and the second light beam on the surface to be inspected and the emission angles of the object light beam and the reference light beam from the surface to be inspected close to each other, the influence of the air disturbance can be reduced. be able to.

Further, by providing the phase relationship changing means for changing the phase relationship between the object light beam and the reference light beam on the screen means, it becomes possible to perform interference fringe analysis using the so-called fringe scanning method. It becomes easy to distinguish the concave portion and the convex portion on the surface to be inspected.

[0034]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic view showing an optical system of a vibration resistant interferometer according to the first embodiment of the present invention. In this optical system, a laser light beam 13 emitted from a laser light source 11 and made into a linearly polarized beam by a polarizing plate 12 is split into two systems by a half mirror 14. Huff mirror 14
The first laser beam 15 reflected by the beam passes through the half-wave plate 16, is diverged by the objective lens 17, is reflected by the mirror 18, and is collimated by the collimator lens 19 into a large-diameter parallel beam, which is a polarized beam. It enters the splitter 20 from above. On the other hand, the second laser beam 21 transmitted through the half mirror 14 is a movable reflection mirror 22 for fringe scanning.
The light beam is reflected by and is incident on the polarization beam splitter (light beam coupler means) 20 in the state of a small-diameter beam from the side.
In the polarized beam splitter 20, the second laser beam 21
Is reflected downward, while the first laser beam 15 that is linearly polarized by 90 ° rotated by the half-wave plate 16 is transmitted downward through the polarization beam splitter 20. As a result, the large-diameter first laser beam 15 and the small-diameter second light beam 21 are combined by the polarization beam splitter 20 and irradiated onto the surface 23a to be measured.

The large-diameter first laser beam 15 is the surface 23a to be measured.
Since the irradiation is performed over a wide range, the reflected light of the first laser beam 15 from the surface 23a to be inspected becomes the object light 24 carrying the minute unevenness shape information of the surface 23a to be inspected. on the other hand,
The second laser beam 21 having a small diameter is applied to one point of the surface 23a to be inspected, so that it becomes the reference light 25 that does not carry the uneven shape information of the surface 23a to be inspected.

The object light 24 and the reference light 25 are returned to the polarization beam splitter 20 in a state where they are combined with each other, and the object light 24 is transmitted by the polarization beam splitter 20.
Is reflected.

After that, the object light beam 24 travels backward through the path of the first laser beam 15 incident on the surface 23a to be inspected, through the collimator lens 19, the mirror 18, the objective lens 17 and the like, to the half mirror 14. To reach. On the other hand, the reference light beam 25 travels backward through the movable reflection mirror 22 along the incident system path of the second laser beam 21 to the surface 23 a to be detected and reaches the half mirror 14.

The transmitted light of the object light beam 24 and the reflected light of the reference light beam 25 on the half mirror 14 are combined by the half mirror 14, and the CCD 27 is formed by the imaging lens 26.
Is imaged on the light-receiving surface of the
An interference fringe image due to the optical interference of 25 is formed on the light receiving surface.

After that, the interference fringe image formed on this light receiving surface is photoelectrically converted and projected on a CRT screen (not shown), and the operator observes the projected interference fringe image and examines the surface to be inspected. Determine the unevenness of 23a.

The movable reflection mirror 22 causes minute vibrations by the piezo drive element 28 attached to its back surface, and minutely changes the optical path lengths of the second laser beam 21 and the reference light beam 25. As a result, a minute phase change occurs between the reference light beam 25 and the object light beam 24, and the fringe pattern of the interference fringe image on the light receiving surface of the CCD 27 moves accordingly. Therefore, the fringe scanning is performed based on this moving direction. It is possible to easily discriminate the concave and convex on the surface 23a to be tested by using the method.

An aperture 29 is arranged at the beam converging position between the imaging lens 26 and the CCD 27.

The characteristics of the above optical system are as follows.
The object light beam 24 and the reference light beam 25 are formed by the reflected light from. The reference light beam 25 is applied to the surface 23 to be measured.
It is formed by the reflected light of the second laser beam 25 incident on one point of a and does not carry the unevenness information of the surface to be inspected 23a. Therefore, if the beam diameter is expanded after this, the accuracy is high. It has a function as reference light as well as light reflected from a flat reference surface.

As described above, since the reference light beam 25 is generated by the same surface as the object light beam 24, even if the distance between the surface 23a to be measured and the polarization beam splitter 20 is changed by the vibration from the outside, both beams 24 are generated. , 25 does not change the phase difference, so that the interference fringes formed by the optical interference of these two beams 24, 25 are not affected by the vibration.

Further, in the above optical system, the first light beam 15, the second light beam 21, the object light beam 24 and the reference light beam 25 are respectively provided with a common optical path between the surface 23a to be detected and the polarization beam splitter 20. Therefore, even if the temperature distribution of the air near the surface to be inspected 23a changes and the air is disturbed, the phase difference between the two beams 24 and 25 does not change. The interference fringes formed by the light interference are not affected by the air disturbance.

Further, in the above optical system, in order to combine the first laser beam 15 and the second laser beam 21, a polarization beam splitter 20 which is usually used in a general optical system is used. Unlike the optical members such as the zone plate in the zone plate interferometer and the like, it does not take time and effort to manufacture, is not expensive, and there is no fear of lowering the degree of freedom in selection and arrangement position of other optical members.

Further, the polarization beam splitter 20 performs beam combining of the first laser beam 15 and the second laser beam 21, and beam splitting of the object light beam 24 and the reference light beam 25. Further, the half mirror is used. Since the beam splitting of the first laser beam 15 and the second laser beam 21 and the beam combining of the object light beam 24 and the reference light beam 25 are performed by the beam splitter 14, the number of parts of the optical system can be reduced.

The objective lens 17 and the collimator lens 19
Is set equal to the focal length f of the collimator lens 19.

Next, the optical system of the vibration resistant interferometer according to the second embodiment of the present invention will be described with reference to FIG.

This optical system has substantially the same features as the optical system of the first embodiment except for the points described later, and has substantially the same operational effect. For the members corresponding to the members of the optical system of the first embodiment, the numbers added to the members of the first embodiment are added with 100, and the description thereof is omitted.

The optical system of the vibration resistant interferometer according to the second embodiment has a polarization beam splitter 120 and a collimator lens 119 as compared with the vibration resistant interferometer according to the first embodiment.
The positions of arrangement of the first laser beam 115, the second laser beam 121, the object light beam 124, and the reference light beam 125 can be made large. . As a result, the effect of eliminating the influence of air disturbance becomes greater,
In particular, it is more effective in an interferometer in which the object light beam 124 has a large beam diameter.

A beam expander 131 for expanding the beam diameter of the first laser beam 121 is arranged between the movable reflection mirror 122 and the polarization beam splitter 120.

The collimator lens 119 and the surface to be measured 123a
And the distance on the optical path from the converging position of the first light beam 115 between the objective lens 117 and the mirror 118 to the collimator lens 119.
Is set equal to the focal length f.

Next, the optical system of the vibration resistant interferometer according to the third embodiment of the present invention will be described with reference to FIG.

This optical system has substantially the same features as the optical system of the first embodiment except for the points described later, and has substantially the same operational effects. For the members corresponding to the members of the optical system of the first embodiment, the numeral added to the member of the first embodiment is added with 200, and the description thereof is omitted.

In the optical system of the vibration resistant interferometer according to the first and second embodiments, the optical systems 17, 19, 117 and 119 for enlarging or reducing the beam diameter are connected to the first laser beam 15, Since the 115 and the object light beams 24 and 124 are configured to pass through, the object light beams 24 and 124 are eventually affected by the aberrations of the optical systems 17, 19, 117 and 119 twice. The effects of optical system aberrations may not be uniform between the light beams 25 and 125. On the other hand, in the optical system of the vibration resistant interferometer according to the third embodiment, the first
The laser expander 215 expands the beam diameter by the beam expander 241 and the reference light beam 225 expands the beam diameter by the beam expander 243, and both beam expanders 241 and 243 have the same lens. Since the object light beam 224 and the reference light beam 225 are composed of a system, the influence of the aberration of the optical system becomes substantially uniform, and the influence of the aberration is canceled between the two beams 224 and 225, so that it is higher. An accurate interference fringe analysis can be performed.

That is, in this optical system, the first laser beam 215 is emitted from the beam expander 241, the movable reflecting mirror 228a, the half mirror 242 and the half mirror 220a.
The object light beam 224 reaches the light receiving surface of the CCD 227 via the half mirror 220a, the mirror 218a, the half mirror 214b, and the imaging lens 226. On the other hand, the second laser beam 221 is emitted from the half mirror 21.
4b, mirror 218a, and half mirror 220a to be inspected surface 223a
And the reference light beam 225 reaches the light receiving surface of the CCD 227 via the half mirror 220a, the mirror 242, the half mirror 214b and the imaging lens 226.

In this optical system, the first laser beam
215 and the second laser beam 221 are combined to form an object light beam.
Half mirror to separate 224 and reference light beam 225
220a, and the above two laser beams 215
, 221 are separated by a half mirror 214a, and the object light beam 224 and a reference light beam 225 are combined by a half mirror 214b. No optical member such as a half-wave plate is used.

Next, the optical system of the vibration resistant interferometer according to the fourth embodiment of the present invention will be described with reference to FIG.

This optical system has substantially the same features as the optical system of the first embodiment except for the points described later, and has substantially the same operational effects. For the members corresponding to the members of the optical system of the first embodiment, the numbers added to the numbers of the members according to the first embodiment are added with 300, and the description thereof is omitted.

In the optical system of the vibration resistant interferometer according to the fourth embodiment, the first laser beam 315 and the second laser beam 321 are combined, and the object light beam 324 and the reference light beam are combined.
Diffractive optical element (including HOE) 320a for separating 325
Is used. Since such a diffractive optical element 320a can be easily manufactured with a large diameter, and the manufacturing cost in this case is low, the above optical system is particularly advantageous when the diameter of the object light beam 324 is increased. Yes, and the device can be made compact.

In each of the above-mentioned embodiments, the surface 23a to be inspected
, 123a, 223a, and 323a have a planar shape, but it is of course possible to observe a test surface having another shape (spherical surface, aspherical surface, etc.) by the vibration resistant interferometer of the present invention. is there.

FIG. 5 shows an optical system of a vibration resistant interferometer according to a fifth embodiment of the present invention, and an optical system for observing a test surface when it has a spherical shape. Is shown.

In the optical system according to the fifth embodiment, the members corresponding to the members of the optical system according to the first embodiment have the same reference numerals as those of the members according to the first embodiment.
Is added and the description is omitted.

In the optical system according to the fifth embodiment, the first laser beam 415 once becomes convergent light by the converging lens 417, becomes divergent light from the converging position P, and is formed on the spherical surface 423 to be inspected. The object light beam 424 is the first laser beam and is configured so that each light beam is incident vertically.
Reverse the same optical path as 415. That is, the convergence position P
Corresponds to the spherical center of the test surface 423a which is a spherical surface. Meanwhile, the second
The laser beam 421 of the reference laser beam 425 is configured so as to be converged by a combination lens 451 and 452 and incident on a point substantially at the center of the surface 423a to be inspected, and the reference light beam 425 has the same optical path as that of the second laser beam 421. Proceed.

Further, in each of the above-mentioned embodiments, the first laser beams 15, 115, 215, 315, 415 and the second laser beams 21, 121, 415 are driven by the surfaces to be inspected 23a, 123a, 223a, 323a, 423a. The object light beams 24, 124, 224, 324, 424 and the reference light beams 25, 125, 225, 325, 425 are obtained by reflecting the light beams 221, 321, 421. In some cases, the object light beam and the reference light beam can be obtained by transmitting the first light beam and the second light beam through the subject.

FIG. 6 shows an optical system of a vibration resistant interferometer according to a sixth embodiment of the present invention.

In the optical path according to the sixth embodiment, for members corresponding to the members of the optical system according to the first embodiment, 500 is added to the numbers given to the members according to the first embodiment. The numbers are attached and the description is omitted.

In the optical system according to the sixth embodiment, the object 523 is sandwiched between the laser light beam 513 and the first laser light beam 513.
The optical system for separating and combining the laser beam 515 and the second laser beam 521, and the optical system for separating and combining the object light beam 524 and the reference light beam 525 are arranged at substantially symmetrical positions. The beam diameter of the first laser beam 515 is expanded by the beam expander 561a, and then the surface to be inspected 523a of the subject 523 is irradiated with the first laser beam 515.
Object light 524 obtained by passing through 523a is reduced by the beam expander 461b.

In the optical system of FIG. 6, the polarizing plate 51
Polarization beam splitters 514a, 51
Polarization splitting and polarization combining are performed using 4b, 520a, 520b and 1/2 wavelength plates 516a, 516b.
When 523 has birefringence, it is possible to dispose a half mirror instead of the polarization beam splitters 514a, 514b, 520a and 520b.

Further, as in the vibration resistant interferometer according to the seventh embodiment of the present invention shown in FIG.
If the aperture 672 is arranged at the beam converging position in the optical path of 5, the scattered light generated by the minute unevenness at the irradiation position of the second laser beam 621 on the surface 623a to be inspected will generate scattered light. It becomes possible to remove the interference fringe image, and thereby an interference fringe image without noise can be obtained. This is similarly applicable to the optical systems of the above-described embodiments.

Further, in FIG. 7, the lens 671 and the lens 673 expand and contract the beam diameter so that the aperture 67
It is adjusted to have a refracting power and an arrangement position so as to converge the second laser beam 621 at the position 2.

In the optical system according to the seventh embodiment, the members corresponding to the members of the optical system according to the first embodiment are the same as the numbers given to the members according to the first embodiment.
Is added and the description is omitted.

FIG. 8 is a schematic diagram showing an eighth embodiment of the vibration resistant interferometer of the present invention.

In the optical system according to the eighth embodiment, first, the laser light beam 713 from the laser light source 711 is split by the half mirror 714 into the first laser beam 715 and the second laser beam 721. Next, the first laser beam 715 reflected by the half mirror 714 is reflected by the mirror 718, the diameter of the light beam is expanded by the beam expander 783, and the parallel light is vertically irradiated onto the surface 723a to be inspected. On the other hand, the second laser beam 721 transmitted through the half mirror 714 is placed on the same base 782 as the subject 723 and is held on the reference plane 781 of the reference plane (the surface precision does not need to be excellent) 781a. Incident perpendicularly to.

The object light beam 724 reflected from the test surface 723a and the reference light beam 725 reflected from the reference surface 781a travel in the same optical path as the two laser beams 715 and 721, and are combined by the half mirror 714. Then, an image is formed on the light receiving surface of the CCD 727 by the image forming lens 726. As a result, an interference fringe image carrying irregularity information on the surface 723a to be inspected, which is generated by the optical interference between the object light beam 724 and the reference light beam 725, becomes a CC image.
It is formed on the light receiving surface of D727.

In this optical system, the second laser beam 721
Is not radiated on the surface 723a to be inspected, the first laser beam 715 and the second laser beam 715 as in each of the above-described embodiments.
721 can be combined or object light beam 724 and reference light beam 725
Need not be separated, and the polarization beam splitters 20, 120, 420, 520a, 520 in the optical system of each of the above-described embodiments are separated.
b, 620, half mirror 220a, diffractive optical element 320a, etc. are unnecessary. As a result, the number of optical components can be reduced, and the configuration of the optical system is further simplified.

Further, since the reference plate 781 for obtaining the reference light beam 725 is fixed on the same base 782 together with the subject 723, the object light beam 724 and the reference light beam 725 are not affected by external vibration. The phase change can be canceled.

Further, the object light beam 724 and the reference light beam
Although 725 does not have a common path between the surface 723a to be inspected and the beam expander 783, the reference plate 781 is disposed near the object 723, and the object light beam 724 and the reference light beam 725 are arranged.
If the spatial positions through which are passed are made close to each other, the influence of the air disturbance can be reduced to a level where there is almost no problem in analyzing the interference fringes.

FIG. 9 shows an optical system of a vibration resistant interferometer according to the ninth embodiment of the present invention.

This optical system also has a first laser beam 815 and a second laser beam 815 as in the optical system of the eighth embodiment.
Synthesis of 821, and object light beam 824 and reference light beam 82
Separation of 5 is unnecessary.

That is, the diameter of the first laser beam 815 is expanded by the beam expander 891 and the surface to be inspected.
The object light beam 824 is incident perpendicularly to 823a and travels backward in the optical path of the first laser beam 815. On the other hand, the second laser beam 821 is obliquely incident on the surface 823a to be measured as shown in FIG. 9, and the reference light beam 825 is emitted obliquely. Therefore, it is not necessary to combine the two laser beams 815 and 821 or separate the object light beam 824 and the reference light beam 825.

However, in the optical system shown in FIG. 9, since the common path of the object light beam 824 and the reference light beam 825 is reduced, for example, as shown in FIG.
The distance between the mirror 828 that reflects 1 and the half mirror 814b that reflects the reference light beam 825 is shortened, and
It is desirable to adjust the optical paths so that the laser beam 821 and the reference light beam 825 both pass through the lens on the object 823 side of the beam expander 891 in order to eliminate the influence of air disturbance.

The vibration-resistant interferometer of the present invention is not limited to the above-mentioned embodiment, and various modifications can be made.

For example, as the light beam coupler means for synthesizing the first light beam and the second light beam, one having a through hole through which the second light beam and the reference light beam pass is formed in the center of the mirror. Can be used.

Further, as the phase relationship changing means for changing the phase relationship between the object light beam and the reference light beam, instead of changing the optical path length of the reference light beam, it is also possible to change the optical path length of the object light beam. Of course, instead of the movable mirror of the above embodiment, it is possible to use one that changes the position of the beam coupler means in a predetermined direction or one that changes the above-mentioned phase relationship by a phase shifter inserted in the optical path. is there.

Further, the surface to be inspected is not limited to that of the above-mentioned embodiment, but can be applied to, for example, a convex spherical surface or an aspherical surface.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an optical system of a vibration resistant interferometer according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram showing an optical system of a vibration resistant interferometer according to a second embodiment of the present invention.

FIG. 3 is a schematic diagram showing an optical system of a vibration resistant interferometer according to a third embodiment of the present invention.

FIG. 4 is a schematic diagram showing an optical system of a vibration resistant interferometer according to a fourth embodiment of the present invention.

FIG. 5 is a schematic diagram showing an optical system of a vibration resistant interferometer according to a fifth embodiment of the present invention.

FIG. 6 is a schematic diagram showing an optical system of a vibration resistant interferometer according to a sixth embodiment of the present invention.

FIG. 7 is a schematic diagram showing an optical system of a vibration resistant interferometer according to a seventh embodiment of the present invention.

FIG. 8 is a schematic diagram showing an optical system of a vibration resistant interferometer according to an eighth embodiment of the present invention.

FIG. 9 is a schematic diagram showing an optical system of a vibration resistant interferometer according to a ninth embodiment of the present invention.

FIG. 10 is a schematic view showing an example in which the arrangement of members of the optical system shown in FIG. 9 is partially changed.

FIG. 11 is a schematic diagram showing a prior art zone plate interferometer.

[Explanation of symbols]

1 Laser Light Beam 4 Test Object 4a Test Surface 5 Zone Plate 9 Cameras 11, 111, 211, 311, 411, 511, 611, 711, 811
Laser light source 12, 112, 412, 512, 612 Polarizing plate 13, 113, 213, 313, 413, 513, 613, 713, 813
Laser light beam 14, 114, 214a, 214b, 220a, 242, 314, 414, 614
, 714, 814a, 814b Half mirror 15, 115, 215, 315, 415, 515, 615, 715, 815
First laser beam 16,116,416,516a, 516b, 616 1/2 wavelength plate 17,117,317,417,617 Objective lens 18,118,218a, 318,418,518a, 518b, 618,718
, 828 Mirror 19, 119, 319, 619 Collimator lens 20, 120, 420, 514a, 514b, 520a, 520b, 620 Polarizing beam splitter 21, 121, 221, 321, 421, 521, 621, 721, 821
Second laser beam 22, 122, 222, 322, 422, 522, 622 Movable reflection mirror 23, 123, 223, 323, 423, 523, 623, 723, 823
Subjects 23a, 123a, 223a, 323a, 423a, 523a, 623a, 723a, 82
3a Test surface 24, 124, 224, 324, 424, 524, 624, 724, 824
Object light beam 25, 125, 225, 325, 425, 525, 625, 725, 825
Reference light beam 26, 126, 226, 326, 426, 526, 626, 726, 826
Imaging lens 27, 127, 227, 327, 427, 527, 627, 727, 827
CCD 28, 128, 228, 328, 428, 528, 628 Piezo drive element 29, 129, 229, 329, 429, 529, 629, 672, 729
, 829 pinhole 131, 241, 243, 561a, 561b, 783, 891 Beam expander 320a Diffractive optical element (HOE) 451, 452 Combination lens 671, 673 Lens 781 Reference plate 781a Reference surface 782 Base

─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Katsuyuki Okada 5-6-4-303 Konakadai, Inage-ku, Chiba-shi, Chiba (56) Reference JP-A-5-26616 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01B 9/02

Claims (7)

(57) [Claims] 1. A light beam emitting means for emitting a coherent light beam; a first light beam separating means for separating the coherent light beam into a first light beam and a second light beam; Light beam coupler means for combining the second light beam and the second light beam to guide the second light beam onto the surface to be inspected of the subject, and the first light beam from the light beam coupler means to form a large beam on the surface to be inspected. So that a diameter light spot is formed,
A first optical system that guides the first light beam whose beam diameter has been expanded to the light beam coupler means, and a second light beam from the light beam coupler means, which has a small diameter on the surface to be detected. A second light guiding means for directing the second light beam to the light beam coupler means to form a spot;
An optical system for separating an object light beam, which is the first light beam transmitted / reflected from the surface to be inspected, and a reference light beam, which is the second light beam transmitted / reflected from the surface to be inspected, The second light beam separating means, the object light beam and the reference light beam separated by the second light beam separating means are overlapped and irradiated, and an interference fringe carrying the unevenness information of the surface to be inspected is formed on the screen. An anti-vibration interferometer, characterized by comprising: 2. The vibration resistant interferometer according to claim 1, wherein the light beam coupler means and the second light beam separating means are formed of the same optical member. 3. The vibration resistant interferometer according to claim 1 or 2, wherein the first light beam separating means is configured to combine the object light beam and the reference light beam. . 4. A light beam emitting means for emitting a coherent light beam, a light beam separating means for separating the coherent light beam into a first light beam and a second light beam, and the first light beam. An optical system that guides the first light beam having an expanded beam diameter onto the test surface so that a large-diameter light spot is formed on the test surface of the test object, and the test object is mounted on the optical system. A reference plate having a reference surface mounted and held in the vicinity of the mounting and holding position of the subject on the held base, and transmitted / reflected from the test surface. An object light beam that is the first light beam and a reference light beam that is the second light beam transmitted / reflected from the reference surface are overlapped and irradiated, and an interference fringe carrying irregularity information of the surface to be inspected is formed. A vibration-proof interference, characterized in that it comprises a screen means formed . 5. A light beam emitting means for emitting a coherent light beam, a light beam separating means for separating the coherent light beam into a first light beam and a second light beam, and the first light beam. The beam diameter is expanded so that a large-diameter light spot is formed on the surface to be inspected by the first
A first optical system that guides the light beam onto the surface to be inspected, and a light spot with a small diameter is formed on the surface to be inspected by the second light beam. A second optical system that guides the second light beam onto the surface to be inspected so that the second light beam enters and exits the surface to be inspected from a direction different from that of the first light beam; / The object light beam that is the reflected first light beam and the reference light beam that is the second light beam transmitted / reflected from the surface to be inspected are overlapped and irradiated.
A vibration-resistant interferometer, comprising: a screen unit on which interference fringes carrying the unevenness information of the surface to be inspected are formed. 6. A divergent light conversion means for converting the first light beam into divergent light so that each light beam of the first light beam is vertically incident on each portion of the spherical surface to be inspected. The vibration resistant interferometer according to any one of claims 1 to 5, wherein 7. The phase relationship changing means for changing the phase relationship between the object light beam and the reference light beam on the screen means is provided. The vibration resistant interferometer described.