JPH0666514A - Interferometer apparatus - Google Patents

Abstract

PURPOSE:To prevent the disturbance due to a flow of air without fail in an optical path of an object light toward an object to be inspected from a reference member provided in the main body of an interferometer. CONSTITUTION:The main body 1 of an interferometer is fitted to a fixed board 2. An opening 2a for introducing a laser light is formed in the fixed board 2 and a lens mount part 6 on which a lens 5 to be inspected, as an object of inspection, is mounted removably is provided in a part on the upper side of this opening 2a. On the lower side of the fixed board 2, a disturbance preventing member 25 formed of a tubular member is fitted and the tip part thereof has an inside diameter which allows a reduced-diameter part 1a of the main body 1 of the interferometer fitted with a reference lens 16 to be inserted into it. The main body 1 of the interferometer is contrived so as to be displaced up and down in order to regulate the relative position of the reference lens 16 to the lens 5 to be inspected, and an optical path of an object light is always positioned inside the disturbance preventing member 25 irrespective of the position of the main body 1 of the interferometer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an interferometer device for inspecting a surface state of an object to be inspected such as a lens by using a laser interferometer.

[0002]

2. Description of the Related Art Generally, a Newton gauge (or Newton prototype) is used to inspect the finishing accuracy of a lens or other object to be inspected, and the object to be inspected through this Newton gauge,
For example, it is performed by irradiating a lens with light and measuring the number of interference fringes (normally called Newton number) generated by the reflected light from the reference surface of the Newton gauge and the reflected light from the object to be measured. Here, the Newton gauge is directly superposed on the lens to be inspected, the illumination light is irradiated to this Newton gauge, and the reflected light from the reference surface of the Newton gauge and the surface to be inspected of the lens to be inspected The simplest inspection method is to observe the interference fringes generated with the reflected light with the naked eye. However, since the Newton gauge is brought into contact with the lens to be inspected at the time of inspection, there is a possibility that scratches or the like may occur on both unless care is taken carefully. In particular, since the Newton gauge is repeatedly used, it is necessary to frequently replace the Newton gauge because scratches are accumulated on the entire surface very early. Also, if dust or other foreign matter enters the overlapping part of the two, it becomes impossible to observe the interference fringes accurately. Therefore, it is necessary to clean the overlapping surface of the both before the inspection, and this work is extremely difficult. There are various problems such as being troublesome.

Therefore, it is known that a laser interferometer is used to make an inspection in a non-contact state with a lens to be inspected. That is, laser light from a laser oscillator is applied to a reference lens through a light guide optical system, a part of the reference surface of the reference lens is reflected, and this is used as a reference light, and a part of the transmitted light is used as a reference light. It is configured so that the interference fringes generated between the reference light and the object light are reflected by the reflected light as the object light on the surface to be inspected of the lens to be inspected mounted so as to face the lens. is there.

[0004]

As described above, when the laser interferometer is used, the lens to be inspected can be inspected in a non-contact manner with the reference lens. Therefore, compared with the method in which the Newton gauge is directly superposed on the lens to be inspected. Therefore, it is possible to reliably prevent the inconvenience that the test lens and the reference lens are damaged. However, in the above-mentioned conventional technology, the interferometer body including the laser oscillator, the light guiding optical system, the reference lens, and the interference fringe observation means is mounted in the housing, but the lens to be inspected is removable. Therefore, the optical path length between the interferometer main body and the lens to be inspected needs to be set to a certain length because of the relationship of the focal length of the lens to be inspected, etc.

Usually, the lens is inspected at a lens manufacturing site, and this lens manufacturing site is not necessarily an environment suitable for disposing an inspection device using a laser beam. That is, since the manufacturing site is an open space, the air flow naturally exists in the atmosphere, and particularly when the air-conditioning equipment and other equipment for generating the air flow are provided, the air flow becomes more intense. Therefore, due to the influence of the surrounding air flow, a so-called disturbance in which the laser light fluctuates in the optical path of the object light between the interferometer body and the lens to be measured may occur. When such a disturbance occurs, the observed interference fringes are not stable, and especially when detecting the finishing accuracy of the lens to be inspected by analyzing the interference fringes by an image processing apparatus using a computer, If stable interference fringes cannot be measured, there are drawbacks such as measurement errors.

Therefore, in order to prevent the disturbance of the laser beam due to such an air flow, the applicant of the present invention houses the interferometer body in a housing, forms an opening in the housing, and forms an opening in the opening. We have developed a structure that forms an object mount part for setting the object. If such a configuration is adopted, it is possible to prevent the disturbance of the laser light due to the air flow outside the housing, that is, the disturbance factor, but such a configuration is not without problems. That is, since the laser oscillator or the like is a heat source in the housing, air convection occurs in the housing, and this convection may cause disturbance to the laser light.

The present invention has been made in order to solve the problems of the prior art as described above, and its purpose is to cause a disturbance not only due to a disturbance factor but also due to the interferometer body itself. Thus, it is another object of the present invention to provide an interferometer device capable of reliably preventing the interference fringe information from becoming unstable.

[0008]

In order to achieve the above-mentioned object, the present invention is designed to provide a light source between a reference light reflected from a reference member and an object light reflected from an object to be inspected set on an object mount portion to be inspected. The feature is that the disturbance prevention member is provided so as to surround the optical path of the object light when the interference is caused.

[0009]

In the optical path of the laser light, the space between the laser oscillator and the reference member is housed in the housing of the interferometer body.
Therefore, the problem of disturbance does not occur. However, it is necessary to move the reference member and the object mounting part in a direction in which they approach and separate from each other. Therefore, the optical path of so-called object light from the reference member to the object to be measured is an interferometer. It cannot be stored in the main body housing. Even if the entire interferometer body is housed in the housing, since the interferometer body has a heat source such as a laser oscillator, the entire interferometer body may be housed in the housing. Air convection may occur inside. Therefore,
In the present invention, the disturbance prevention member is provided so as to surround the optical path of the object light.

In the interferometer main body, a heat source is a laser oscillator, and the laser oscillator is generally arranged at a position apart from the reference member to some extent. Therefore, there is no particular heat source in the optical path of the object light from the reference member to the object to be inspected. For this reason, the site concerned should be isolated from others by a disturbance prevention member,
Moreover, if the isolated space is made as small as possible, the air inside the disturbance preventing member is reliably held in a stationary state. As a result, the optical path of the object light can be prevented from being disturbed, and stable interference fringes can be observed.

[0011]

Embodiments of the present invention will now be described in detail with reference to the drawings. First, FIGS. 1 to 3 show a first embodiment of the present invention. In the figure, reference numeral 1 denotes an interferometer main body, which is mounted on a surface plate 2 which is mounted on a main body machine frame 3. The platen 2 has an opening 2a for guiding a laser beam.
Is formed, and a lens mount portion 6 to which a lens 5 to be inspected as an object to be inspected is detachably attached is provided on the upper surface of the opening 2a. Further, inside the surface plate 2, a moving means 7 of the interferometer main body 1 is provided.

An example of the interferometer body 1 is shown in FIG. Although a so-called Fizeau interferometer is shown in this figure, it goes without saying that the interferometer used in the present invention is not limited to this type. In the figure, 10 is a laser oscillator 10 composed of a He-Ne laser or the like, and the laser light output from this laser oscillator 10 is once condensed by a diverging lens 11 for beam divergence. , Diverge. A pinhole 12 is provided at the condensing position of the diverging lens 11 so that light other than the condensed light is cut from the optical path. The light passing through the pinhole 12 is reflected by the reflecting surface 13a of the beam splitter 13. The reflected light from the beam splitter 13 is collimated by a collimator lens 15 via a quarter-wave plate 14, and the collimated light is a reference lens 16 as a reference member.
Is incident on. The incident surface 16a of the reference lens 16 is provided with an antireflection coating, and the incident surface 16a
The surface on the side opposite to is a reference surface 16b, and the reflected light from this reference surface 16b forms a reference wavefront as reference light with respect to the measurement wavefront which is the object light reflected from the surface 5a to be measured of the lens 5 to be measured. To do.

When the lens 5 to be inspected is mounted on the lens mount portion 6, the laser oscillator 10 passes through a diverging lens 11, a pinhole 12, a beam splitter 13 and a collimator lens 15 which form an optical system for guiding a laser beam, and then a reference lens. 16 is incident on the reference lens 16, a part of which is reflected by the reference surface 16 a of the reference lens 16, and the other is incident on the subject lens 5 and reflected by the subject surface 5 a of the subject lens 5. Reference lens 1
The reflected light from the reference surface 16 a of 6 and the surface 5 a of the lens 5 to be tested is converged by the collimator lens 15 and returned to the beam splitter 13 via the quarter-wave plate 14. Here, this return light is reflected by the beam splitter 13.
Is transmitted through the reflective surface 13a. A diaphragm 17 and an imaging lens 18 are provided in the optical path of the transmitted light of the beam splitter 13, and the reference light from the reference surface 16b and the surface 5a to be inspected are provided at the imaging position of the imaging lens 18. The interference fringes are imaged by the interference effect with the object light from. An image pickup unit 19 including a CCD or the like is provided at this image forming position, and an interference fringe is photographed by this image pickup unit 19.

As described above, the surface state of the lens 5 to be inspected is inspected by observing the interference fringes. To accurately inspect the lens 5 to be inspected, the lens 5 to be inspected
Must be accurately positioned on the lens mount 6. As the lens 5 to be inspected by this interferometer device, various lenses such as a spherical lens and a cylindrical lens are used. For this reason, it is necessary to use the optimum lens mount portion 6 according to the type of the lens to be inspected. Therefore, the XY stage 20 is mounted on the opening 2a of the surface plate 2, and the lens mount portion 6 is mounted on the XY table 20 such that the position of the lens mount 6 can be finely adjusted in the horizontal direction. For example, when a spherical lens is used as the lens 5 to be inspected, the lens mount portion 6 is provided with protrusions at three positions with different phases by 120 °, and the protrusion of the lens 5 to be inspected is provided on each of these protrusions. Positioning is performed by abutting a portion of the surface 5a near the outer peripheral edge.

Next, when inspecting the lens 5 to be inspected, it is necessary to adjust the position between the interferometer main body 1 and the lens mount portion 6 in accordance with the curvature of the lens 5 to be inspected. Further, since it is necessary to displace the interferometer main body 1 between the observing position of the interference fringes of the lens 5 to be inspected and the cat's eye point, the interferometer main body 1 is reciprocally displaceable in the direction of approaching and separating from the lens mount 6. I am trying. For this purpose, the lens mount 6 is fixed and the interferometer body 1
Is moved up and down by the moving means 7. As is clear from FIGS. 1 and 2, the moving means 7 has a guide rail 21 vertically laid on a surface plate 2, and the interferometer body 1 is slidably supported by the guide rail 21. The screw shaft 22 is inserted into the shaft 1 to reciprocate along the guide rail 21. The screw shaft 22 is connected to the operation handle 24 via the bevel gear transmission means 23 by operating the operation handle 24 so that the relative distance between the interferometer body 1 and the lens 5 to be inspected. The positional relationship can be adjusted.

On the lower surface of the surface plate 2, an upper end portion of a disturbance preventing member 25 made of a cylindrical member is attached by a bolt or the like, and the disturbance preventing member 25 extends downward.
The disturbance preventing member 25 is for preventing an air flow from being generated in the optical path of the object light, and the mounting portion of the reference lens 16 in the interferometer main body 1 has a reduced outer diameter. The portion 1a is formed by a predetermined length, and the disturbance preventing member 25 has an inner diameter into which the reduced diameter portion 1a can be fitted. Here, the interferometer body 1 is adapted to be displaced up and down in order to adjust the relative position of the reference lens 16 with respect to the lens 5 to be inspected, and regardless of the position of the interferometer body 1, The optical path of the object light is always located inside the disturbance prevention member 25. Further, the fitting portion of the interferometer main body 1 to the disturbance prevention member 25 is in a state where there is no gap as much as possible so long as it does not hinder the movement of the interferometer main body 1. As a result, the optical path of the object light is isolated from the outside and is almost sealed in a relatively narrow space. Even if an air flow or the like is generated outside, the air inside the disturbance prevention member 25 is Is held so that it does not fluctuate.

The present embodiment is constructed as described above, and in inspecting the surface condition of the lens 5 to be inspected using this apparatus, first, a lens having a predetermined aperture and radius of curvature is used. A reference lens 16 suitable for measuring the number of Newtons is mounted on the interferometer main body 1, and the lens mount portion 6 supports a portion near the outer peripheral edge thereof according to the outer diameter dimension of the lens 5 to be inspected. Install the one with the optimum size for. Then, operate the operation handle 24,
The interferometer main body 1 is adjusted so that when the lens 5 to be inspected is set, the interferometer main body 1 has an optimum relative positional relationship for measuring the number of Newtons. In this state, the lens 5 to be inspected is set on the lens mount 6 and the interference fringes between the surface 5a to be inspected and the reference surface 16b of the reference lens 16 are photographed, and the lens to be inspected is determined according to the number of Newtons. It is possible to inspect the finishing accuracy of the surface 5a to be inspected.

By the way, the light incident on the lens 5 to be inspected through the reference lens 16 from the laser oscillator 10 in the interferometer body 1 and the reflected light from this lens 5 to be inspected are imaged on the image pickup means 19. There must be no fluctuations in the laser light along the entire optical path. Since the interferometer main body 1 is normally housed in the housing, it is not affected by disturbance factors. Therefore, the reference lens 16 to the test lens 5
Since the optical path of the object light up to is located outside the housing of the interferometer main body 1, fluctuations in the optical path may occur if there is an airflow at this portion. However, since the optical path of this object light is surrounded by the disturbance prevention member 25 and the space inside is kept stationary, no disturbance occurs in the optical path of the object light due to the effect of the air flow outside. . As a result, the interference fringes imaged on the image pickup means 19 are stabilized, and accurate observation thereof is possible. At the same time, the interference fringe information is analyzed by using the image processing means, that is, the number and shape of the interference fringes are automatically determined. It is possible to prevent the determination error from occurring in the case of making the determination.

The disturbance preventing member 25 covers the portion of the interferometer main body 1 where the reference lens 16 is attached, and moreover, is always in the entire movement stroke of the interferometer main body 1 from the cat's eye point to the interference fringe observation position. Since the optical path of the object light can be completely covered, the disturbance in this optical path can be surely prevented. Moreover, the inside of the disturbance prevention member 25 is a relatively narrow space surrounding the optical path of the object light, and there is no factor that causes uneven temperature distribution such as a heat source inside the disturbance prevention member 25. Convection of air inside the can be minimized.

Here, when the lens 5 to be inspected is a spherical lens, a protrusion is provided in the lens mount portion 6,
It is preferable to position and support the protrusions. However, with this configuration, the lens 5
A slight gap is formed between the lens mount portion 6 and the lens mount portion 6. Then, there is a possibility that the airflow may enter the inside through this gap. In order to prevent this, there is an effect to some extent by lowering the height of the protrusions, etc., but a lid 26 is provided at the position where the opening 2a is formed in the surface plate 2 so as to be openable and closable, and the lens mount is provided by this lid 26. Part 6
It can be completely isolated from the outside by putting it on. In order to prevent the laser light from being reflected from the inner surface of the lid 26, the inner surface may be subjected to antireflection treatment. Further, by covering the lens mount portion 6 with the lid 26 in this manner, harmful light from the outside can be blocked.

Next, FIGS. 4 and 5 show a second embodiment of the present invention. In this embodiment, the interferometer main body side is fixed, and the lens side to be inspected is moved in a direction of approaching and separating from the interferometer main body. Thus, 3 in the figure
Reference numeral 0 indicates a main body frame of the apparatus, and the interferometer main body 1 is fixedly mounted on the main body frame 30. A cylindrical body 31 extends on the upper side of the interferometer body 1. On the other hand, the lens mount portion 6 is provided on the disturbance prevention member 32. The disturbance prevention member 32 includes a top plate portion 32a and a peripheral body portion 3
2b, the lens mount portion 6 is provided on the top plate portion 32a, and an opening for passing object light is formed at the position of the lens mount portion 6. Body 32b
The lower end of the is fitted into the tubular body 31, and the disturbance preventing member 32 is movable in the vertical direction while maintaining this fitted state.

The disturbance preventing member 32 is driven up and down by a motor 33, and a connecting member 34 is connected to a peripheral body portion 32b of the disturbance preventing member 32. The connecting member 34 is a screw rotated by the motor 33. Axis 35
And the guide member 36 as well.
Therefore, by operating the motor 33, the interferometer main body 1 can be displaced in a direction of approaching or separating from the lens mount portion 6. Further, in the figure, reference numeral 37 is a lid body attached to the disturbance prevention member 32 for opening and closing the lens mount portion 6.

Even with the above construction, the optical path of the object light between the interferometer body 1 and the lens mount 6 is kept in a state of being isolated from the outside by the disturbance prevention member 32, and the optical path of the object light is kept. The disturbance can be surely prevented.

[0024]

As described above, according to the present invention, the disturbance preventing member is provided so as to surround the optical path of the object light between the interferometer body and the object to be inspected. Can prevent turbulence from occurring in the optical path of the object light, and the optical path will not be disturbed by the influence of air convection caused by heat of the laser oscillator, etc. In this state, the interference fringes are stabilized, accurate interference fringe information can be observed, and the inspection accuracy and efficiency of the object to be inspected are improved.

[Brief description of drawings]

FIG. 1 is a sectional view showing an overall configuration of an interferometer device according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line XX of FIG.

FIG. 3 is a configuration diagram of an optical system in the interferometer device.

FIG. 4 is a sectional view showing an overall configuration of an interferometer device according to a second embodiment of the present invention.

5 is an external view of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Interferometer main body 2 Surface plate 5 Test lens 6 Lens mount part 7 Moving means 10 Laser oscillator 16 Reference lens 25,32 Disturbance prevention member 26,37 Lid 32a Top plate part 32b Circumferential body part 33 Motor 35 Screw shaft

Claims (4)

[Claims] 1. A laser oscillator, an optical system for guiding a laser beam from the laser oscillator, and a reference member for reflecting a part of the laser beam guided from the optical system for guiding and transmitting a part thereof. And an interferometer main body provided with an interference fringe observation means, and an object mount part to be inspected is provided at a position separated by a predetermined distance from the reference member, and the object to be inspected is set on the object mount part to be inspected. An interferometer for observing the interference fringes by the interference fringe observation means by causing interference between the reference light reflected from the reference member and the object light reflected from the object to be inspected set on the object mount part to be inspected. The interferometer device is characterized in that a disturbance prevention member is provided so as to surround the optical path of the object light. 2. The object mount portion to be inspected is mounted on a surface plate, the disturbance prevention member is provided so as to be connected to the surface plate, and at least a part of the interferometer body is located inside the disturbance prevention member. The interferometer apparatus according to claim 1, wherein the interferometer body is configured to be displaceable in a direction in which the interferometer body approaches and separates from the object to be inspected. 3. The disturbance prevention member is provided with the test object mount, and the disturbance prevention member is fitted with at least a part of the interferometer main body or a cylindrical body extending from the interferometer main body. The interferometer apparatus according to claim 1, wherein the object mount portion to be inspected is displaceable in a direction of approaching or separating from an interferometer body. 4. The interferometer apparatus according to claim 1, wherein a lid for covering the object to be inspected set therein is provided on the object mounting portion so as to be openable and closable.