JP3123256B2 - Test lens support device for interferometer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is for inspecting the surface condition of a lens such as a spherical lens using a laser interferometer. The present invention relates to a lens support device.

[0002]

2. Description of the Related Art There has been conventionally known an arrangement in which a laser interferometer is used to inspect and measure the finishing accuracy of a lens. That is, a reference lens is disposed in an optical path of laser light from a laser light source, and a test lens is disposed at a position in front of the reference lens in this optical path. The surface condition of the lens to be inspected is measured by measuring the number of interference fringes (usually called Newton number) generated between the object light which is the reflected light from the surface to be inspected. is there. Thus, using a laser interferometer,
Since the lens to be inspected can be inspected in a non-contact manner, it can be inspected precisely without damaging the reference lens and the lens to be inspected, which is extremely convenient.

[0003]

Here, the optical elements from the laser oscillator to the reference lens are housed in the housing as the main body of the interferometer. However, since the lens to be tested must be detachable, A lens mount is provided, and a test lens is set on the lens mount. In order to measure the lens under test with high accuracy, the lens to be measured has no inclination or tilt, and the center of the radius of curvature of the surface to be measured of the lens to be measured is on the optical axis of the laser beam emitted from the interferometer body. The lens must be set in the lens mount in a state where it is positioned at the same position as the center of the radius of curvature of the reference surface of the reference lens, that is, the position of the so-called cat's eye point. Further, in order to efficiently measure the lens to be measured, it is necessary to easily attach and detach the lens to and from the lens mount.

When setting the lens to be tested on the lens mount, the above points must be noted, but various proposals have been made to meet this demand. For example, a lens mount is provided on the upper part of the interferometer main body, the lens to be measured is set so that the surface to be measured is directed downward on the lens mount, and the laser light is irradiated from below the lens to be measured. Things have been suggested. And
The lens mount is formed by providing a ring-shaped or three or more projections on the lens mount, and the lens to be measured is set such that the surface to be measured abuts the lens set part. Has been made. With this configuration, the test lens is positioned and held on the lens set portion by the action of its own weight such that the center of the radius of curvature of the test surface is located at the cat's eye point. There is an advantage that the attachment / detachment operation becomes extremely easy.

[0005] However, such a method of attaching and detaching the lens to be inspected does not always have no problem. That is, since the surface of the test lens is in contact with the lens set portion, when the weight of the test lens increases, the load concentrates on the contact portion between the test lens and the lens set portion. Therefore, there is a disadvantage that distortion occurs on the surface to be inspected of the lens to be inspected, and interference fringes due to the distortion occur, thereby deteriorating the measurement accuracy of the lens to be inspected, particularly in the peripheral region. Here, when the lens set portion is formed by three protrusions, the load of the lens to be measured is concentrated on three points,
Further, even if the lens set portion is formed in a ring shape, the load is concentrated at three points because the lens set portion is substantially supported at three points. When measuring a lens to be measured, which has a considerable weight depending on its outer diameter and thickness, an extremely large load acts on the contact portion with the lens set portion, and the distortion is correspondingly large. Therefore, interference fringes due to this distortion may occur in a wide range, and there may be a part where inspection / measurement is substantially impossible.

The present invention has been made in view of the above points, and an object of the present invention is to provide a method of mounting a test surface on a test surface by a load without deteriorating the ease of attaching and detaching the test lens to and from a lens mount. An object of the present invention is to surely prevent distortion from occurring and enable accurate inspection and measurement of a lens to be inspected.

[0007]

In order to achieve the above-mentioned object, according to the present invention, a test surface of a test lens is brought into contact with a lens set portion of a lens mount and positioned by the action of its own weight. It is characterized in that the lens mount is not held in such a state, and that the lens mount is equipped with a load adjusting means for adjusting the pressing load of the lens under test against the lens set by its own weight.

[0008]

In setting the test lens in the lens set portion of the lens mount, it is more advantageous to enable positioning by the action of its own weight from the viewpoint of the operability of attaching and detaching the test lens. However, in order to position the center of the radius of curvature of the surface of the lens to be measured at the cat's eye point,
In order to align the light so as to be located on the optical axis of the light emitted from the interferometer body, the action of the weight of the test lens is used. However, if there is a certain amount of load, this alignment is ensured, and it is not necessary to apply a load more than the load enough to ensure this alignment, and it also causes distortion on the test surface. It will be harmful because it will be generated. Therefore, in the present invention, a configuration is adopted in which the pressing load of the test lens against the lens set portion is adjusted. As a result, even if the test lens is heavy, the test surface is not distorted due to an excessive load, and the centering action of the interferometer body can be reliably exhibited. This load adjusting means can be constituted by an elastic member made of, for example, a spring or an elastic body such as rubber.

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings. First, in FIG. 1, reference numeral 1 denotes an interferometer main body, and the interferometer main body 1 is mounted on a main body casing 2 having an anti-vibration mechanism. The main body casing 2 is a sealed space in order to prevent air disturbance inside, and the interferometer main body 1 is mounted so as to be vertically displaceable by a lifting / lowering means 3. An opening 4 is formed in the top plate portion 2a of the main body casing 2 so that the laser beam from the interferometer main body 1 can be led out through the opening 4. The test lens 5 whose surface condition is to be measured is set on a lens mount 6 arranged on the upper surface side of the opening 4 so that the test surface 5a faces the interferometer main body 1 side. Have been.

FIG. 2 shows an example of the main body 1 of the interferometer. The figure shows a so-called Fizeau interferometer, but it goes without saying that the interferometer used in the present invention is not limited to this type. In FIG. 1, reference numeral 10 denotes a laser oscillator 10 composed of a He—Ne laser or the like. The laser light output from the laser oscillator 10 is once focused 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 off from the optical path. The light passing through the pinhole 12 is reflected by the reflection surface 13a of the beam splitter 13. The light reflected by the beam splitter 13 is converted into parallel light by a collimator lens 15 via a quarter-wave plate 14, and the parallel light is incident on a reference lens 16. The incident surface 16a of the reference lens 16 is provided with an anti-reflection coating, and the surface opposite to the incident surface 16a is a reference surface 16b, and the light reflected from the reference surface 16b is reflected by the lens 5 to be measured. A reference wavefront is formed as reference light with respect to the measurement wavefront that is the object light reflected from the test surface 5a.

When the lens 5 to be tested is mounted on the lens mount 6, the reference lens 1 is transmitted from the laser oscillator 10 through the diverging lens 11, the pinhole 12, the beam splitter 13, and the collimator lens 15 which constitute an optical system for guiding a laser beam.
6, a part of the light is reflected by the reference surface 16b of the reference lens 16, and the other is incident on the lens 5 to be inspected and reflected by the surface 5a of the lens 5 to be inspected. Reference lens 16
The reflected light from the reference surface 16b and the test surface 5a of the test lens 5 is returned to the beam splitter 13 via the quarter wavelength plate 14 while being converged by the collimator lens 15. Here, this return light passes through the reflection surface 15a of the beam splitter 13. The optical path of the transmitted light of the beam splitter 13 includes an aperture 17 and an imaging lens 1.
An interference fringe is formed at the imaging position of the imaging lens 18 by the interference between the reference light from the reference surface 16b and the object light from the test surface 5a. An imaging means 19 composed of a CCD or the like is provided at the image forming position, and the imaging means 19 captures interference fringes.

As described above, the surface condition of the lens 5 to be inspected is inspected by observing the interference fringes. To accurately inspect the lens 5 to be inspected, it is necessary to inspect the lens 5 to be inspected.
Must be accurately positioned on the lens mount 6. That is, as shown in FIG.
The center O of the radius of curvature of the surface 5a to be inspected is positioned on the optical axis A of the laser beam emitted through the reference lens 16 in the interferometer main body 1, and the reference surface 16
It must be located at the center of the radius of curvature b, the so-called cat's eye point. When the position is shifted from the cat's eye point in the direction of the optical axis A, the position of the interferometer 1 can be adjusted by appropriately raising and lowering the interferometer main body 1 by the lifting / lowering means 3. However, as shown by O 'in the figure, when the test surface is at a position shifted from the optical axis A, the test surface is at a position shown by a virtual line in the diagram, and the object light reflected from the test surface is A shift occurs between the wavefront and the wavefront of the reference light reflected from the reference surface 16b of the reference lens 16,
Accurate interference fringes are not formed, making inspection and measurement impossible. Accordingly, the test lens 5 must be set on the lens mount 6 such that the center O of the radius of curvature of the test surface 5a is located on the optical axis A.

The lens mount 6 on which the lens 5 to be tested is set has an XY stage 60 whose position can be adjusted in a direction perpendicular to the optical axis A, and a lens setting section 61 is mounted on the XY stage 60. Is provided. As shown in FIG. 4, the lens set portion 61 is formed by a protrusion indicated by a symbol P, which is disposed at a position where the phase is changed by 120 °, respectively, or is denoted by a symbol R in FIG. As shown, it may be formed of a ring-shaped member.

The lens mount 6 having such a configuration
When setting the lens 5 to be inspected,
It must be maintained in a state where the center O of the radius of curvature of a is exactly coincident with the optical axis A. Moreover, in order to sequentially inspect and measure a large number of lenses 5 to be inspected, each lens 5 to be inspected must always be mounted at a fixed position. Here, since the test surface 5a of the test lens 5 is a spherical surface, the periphery of the test surface 5a is brought into contact with the lens set portion 61 of the lens mount 6, and the test lens 5 Alignment is achieved by the action of its own weight.

The load of the test lens 5 is applied to the lens setting section 61 in order to cause the test lens 5 to perform the centering action on the optical axis A on the interferometer body 1 side by the action of the weight of the test lens 5. Be supported. However, even if the lens set 61 is configured as shown in FIG. 4 or has the structure shown in FIG. 5, the lens 5 to be measured is substantially supported by the lens set 61 at three points. become. Therefore, the load is concentrated on these three supported points, and if the weight of the test lens 5 increases, the test surface 5a may be distorted by the load.

In view of the above, in the present invention, the load absorbing means 62 is attached to the lens mount 6 in order to absorb the load on the lens 5 to be tested which is more than necessary to exhibit the above-described alignment function. It is configured to be provided. As shown in FIG. 6, the load absorbing means 62 has a circular load receiving ring 63 located on the upper surface of the XY stage 60 outside the mounting portion of the lens setting portion 61. Are compression springs 6 as elastic members provided at a plurality of positions, at least three positions, on the XY stage 60.
4 is supported. An inner peripheral surface of the load receiving ring 63 is a tapered surface 63a, and an outer peripheral edge portion of the lens 5 to be inspected on the side of the inspected surface 5a comes into contact with the tapered surface 63a.

With this configuration, when the test lens 5 is set on the lens setting portion 61, the outer peripheral edge portion on the test surface 5a side first comes into contact with the tapered surface 63a of the load receiving ring 63. Then, since the load of the test lens 5 acts on the load receiving ring 63, as shown in FIG. 7, the compression spring 64 is compressed and pushed down, and the test surface 5a of the test lens 5 is lowered. The load of the lens 5 to be inspected is absorbed by the compression of the compression spring 64 due to the contact with the lens set portion 61. Therefore, the spring force of the compression spring 64 is used to align the test lens 5 with respect to the lens set portion 61 such that the center O of the radius of curvature of the test surface 5a is positioned on the optical axis A. The required load acts,
It is set so that a larger load can be absorbed. Thus, distortion caused by the test surface 5a being pressed against the lens set portion 61 with excessive force can be suppressed to a minimum. As a result, in addition to the interference fringes based on the interference between the object light from the test surface 5a and the reference light from the reference surface 16b of the reference lens 16, the interference fringes due to the distortion of the test lens 5a Can be reduced as much as possible, and the measurement accuracy of the surface state due to the interference fringes of the test lens 5 is significantly improved.

Incidentally, the test lens 5 measured by this interferometer has various shapes, and its weight naturally varies depending on the type of the test lens. For this reason, it is preferable that the load absorbing force of the load receiving ring 63 constituting the load absorbing means 62 can be adjusted. Here, the load absorbing force of the load receiving ring 63 changes according to the spring force of the compression spring 64. To do this,
A compression spring having a spring force according to the weight of the test lens 5 may be selected and used. In addition, even if a compression spring having the same spring force is used, the load absorbing force of the load receiving ring 63 also changes depending on the distance from the position where the lens 5 abuts to the lens setting portion 61 in the free state. That is, even with the same compression spring, the longer the distance, the greater the load absorbing force.

If the thickness of the test lens 5 is the same, generally, as the outer diameter increases, the weight also increases. The test lens 5 having such a large outer diameter is provided with the load receiving ring 63.
Abuts on the position above the tapered surface 63a, the load absorbing force increases. Further, in the case of the test lenses 5 having the same outer diameter and having different weights due to the thickness and the like, the position where the compression spring 64 is installed can be adjusted vertically. By adjusting this height according to the weight of the lens to be inspected,
Adjustment of the load absorbing force can be performed.

In the above-described embodiment, the structure in which the compression spring 64 is used as the elastic member for exerting the load absorbing force is shown. However, FIGS.
As shown in (1), an elastic body 65 such as rubber or sponge can be used as the load absorbing means. This elastic body 6
Numeral 5 is fixed on the XY stage 60 by means of bonding or the like, and a portion on the outer peripheral side of the test surface 5a of the test lens 5 is avoided as much as possible so as to avoid the formed portion of the lens set portion 61. It is in contact with a wide surface.

With this configuration, when the lens 5 to be inspected is set on the lens mount 6, it first comes into contact with the elastic body 65 and elastically deforms the elastic body 65 to absorb a predetermined load. In this state, the lens 5 comes into contact with the lens set portion 61. Therefore, the positioning accuracy of the test surface 5a is maintained by the action of the weight of the test lens 5, and the test surface 5a is distorted by the load. Can be prevented.

[0022]

As described above, according to the present invention, the surface to be inspected of the lens to be inspected is brought into contact with the lens set portion of the lens mount, and is held in a state of being positioned by the action of its own weight. As a result, the lens to be inspected can be set easily, quickly, and accurately on the lens set section while being accurately positioned, and a load for adjusting the pressing load against the lens set section due to the weight of the lens to be inspected on this lens mount. Since the adjusting means is mounted, an excessive load acts on the contact surface of the test lens with the lens set portion on the test surface, so that there is no possibility that the test surface will be distorted during measurement. It has various effects.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an overall configuration of an interferometer apparatus according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of an optical system in the interferometer apparatus.

FIG. 3 is an explanatory diagram showing a relationship between a center of a radius of curvature of a surface to be measured of a lens to be measured and an optical axis in an optical path of laser light emitted from an interferometer main body.

FIG. 4 is a diagram illustrating a configuration of a lens setting unit.

FIG. 5 is an explanatory diagram showing another configuration example of the lens setting unit.

FIG. 6 is a sectional view of a lens mount showing the first embodiment of the present invention.

FIG. 7 is an operation explanatory view of FIG. 6;

FIG. 8 is a sectional view of a lens mount showing a second embodiment of the present invention.

FIG. 9 is a plan view of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Interferometer main body 2 Main body housing 5 Test lens 5a Test surface 6 Lens mount 16 Reference lens 16b Reference surface 60 XY stage 61 Lens set section 62 Load absorbing means 63 Load receiving ring 64 Compression spring 65 Elastic body

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) G01B 9/00-11/30 102 G01M 11/00-11/08

Claims (2)

(57) [Claims] 1. A part of a reference surface of a reference lens provided in an interferometer main body is reflected, and light transmitted through the reference lens is reflected by a lens to be inspected to generate an interference fringe between both reflected lights. Inspection and measurement of the surface state of the lens to be inspected by doing, the surface to be inspected of the lens to be inspected is brought into contact with the lens set portion of the lens mount, and is positioned by the action of its own weight. The lens mount has a structure for holding the lens, and the lens mount is provided with a load adjusting means for adjusting a pressing load of the lens to be tested against the lens set by its own weight. apparatus. 2. The load adjusting means comprises an elastic member in contact with a surface to be inspected of the lens to be inspected, and the elastic member is elastically deformed to absorb a load and to adjust a lens on the surface to be inspected of the lens to be inspected. 2. The apparatus according to claim 1, wherein the pressing force against the set portion is adjusted.