JP2001082944A - Apparatus for measuring inclination of subject - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately measure the inclination of a subject having a curved surface to be measured. SOLUTION: This apparatus for measuring the inclination of a subject includes a light source 11, a light-receiving element 19, and a collimator lens 17 for converting light rays emitted from the light source 11 into parallel light rays to irradiate the subject 18 therewith and for collecting and focusing the reflected light rays onto the light-receiving element 19, and measures the inclination of the subject 18 from the imaging position of the light-receiving element 19. The apparatus also has a reference lens 20 disposed between the collimator lens 17 and the subject 18 to collect or diffuse the parallel light rays to irradiate the subject 18 therewith from a direction perpendicular to the tangent of the curved surface of the subject 18.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tilt measuring device for measuring the tilt of a test object having a curved test surface such as a collimator lens for a pickup device.

[0002]

2. Description of the Related Art FIG. 5 is a diagram showing a basic configuration of a conventional laser autocollimator. In the figure, light emitted from a laser diode (LD) 11 is reflected by a total reflection mirror 1.
It is reflected at 4. Further, the linearly polarized laser light is reflected by the polarization beam splitter 15, passes through the λ / 4 plate 16, becomes a circularly polarized wave, passes through the collimator lens 17, becomes parallel light, and is transmitted to the lens 18. Irradiated. The light reflected by the object lens 18 is condensed by the collimator lens 17, passes through the λ / 4 plate 16, and is linearly polarized (for example, s).
(Polarized wave), passes through the polarization beam splitter 15 and forms an image on the light receiving element 19.

[0003] With such a configuration, the inclination of the object lens 18 is measured according to the image forming position of the light receiving element 19.
For example, if the imaging position when the test object is not tilted is known in advance, the tilt of the test lens 18 is measured from the relative position to the image forming position. In addition, as the light receiving element 19, a two-dimensional position detecting element (PSD) or a solid-state imaging element (CC
D) is used.

[0004]

In the conventional laser autocollimator, if the object to be inspected is a flat surface, the reflected light from the surface to be inspected is also parallel light, and all the reflected light is directed to one point on the light receiving element. It can be converged and observed as a point image. Therefore, the inclination of the test object can be easily measured.

However, if the surface of the test object is a curved surface,
The reflected light from the test surface becomes diffused light, and only a part of the reflected light can be focused on the light receiving element as shown in FIG. In this case, the image on the light receiving element 19 is gradually blurred concentrically with respect to a certain center corresponding to the inclination of the test lens 18.

Further, depending on the distance between the collimating lens 17 and the test lens 18, even if the light is diffused outside the collimating lens 17 as shown in FIG. The light that reaches the light receiving element 19 is only a part of the expanded range. Therefore, the amount of light that can be used for measurement is significantly reduced.

[0007] Due to such factors, in the conventional laser autocollimator, the image on the light receiving element when the tilt of the test object having a curved test surface is measured becomes unclear, and it is difficult to measure the tilt. It is.

When there is a flat portion 18a at the edge of the test lens 18 as shown in FIG.
By condensing the reflected light from a with the collimating lens 17, it is possible to indirectly observe the tilt of the object lens 18. However, this requires that the flat portion 18a has a sufficient area and that flatness corresponding to the tilt of the test lens 18 is guaranteed.
It is limited to the case of tilt measurement for some test objects.

An object of the present invention is to provide a tilt measuring apparatus capable of accurately measuring the tilt of a test object having a curved test surface.

[0010]

In order to achieve the above object, according to the present invention, a light source, a light receiving element, and parallel light emitted from a light source are radiated toward a test object, and the reflected light is collected. A collimator lens that emits light and forms an image on the light receiving element; a tilt measuring device that measures the tilt of the test object from the image forming position of the light receiving element; A reference lens that converges or diffuses the parallel light to irradiate the test object from a direction orthogonal to a tangent to a curved surface of the test object. This makes it possible to configure the light incident on the test object so as to be perpendicular to the curved surface, and to guide a large amount of reflected light to the light receiving element.

In another invention, in addition to the above-mentioned invention,
When the test surface of the test object is a curved surface that is spherical or aspherical, the position of the reference lens such that the focal position of the reference lens coincides with the center position of at least one radius of curvature of the test object. Set. As a result, the incident angle of the light applied to the test object becomes 0 or near 0, and a large amount of reflected light returning in the coming direction is obtained, and a large amount of reflected light is imaged on the light receiving element via the collimating lens. be able to.

According to another aspect of the present invention, in addition to the apparatus for measuring the tilt of a test object according to each of the above-mentioned inventions, the width of the light beam emitted from the reference lens is orthogonal to the optical axis of the test surface of the test object. The collimating lens is disposed so as to be equal to or smaller than the width in the direction in which the light enters the surface to be detected. Therefore, 100% of the light from the reference lens can be applied to the test object, and the amount of reflected light can be increased.

According to another aspect of the present invention, in addition to the above-described aspects, when the test object is a convex lens or a concave lens, the width of the light beam of the light emitted from the reference lens is smaller than or equal to the effective diameter of the convex lens. , The focal length and position of the reference lens. Thereby, all of the light condensed by the reference lens can be applied to the convex lens and the concave lens.

In another invention, in addition to the above-described inventions, when the test object is a concave lens, measurement is performed by disposing this concave lens further away from the collimating lens with the focal position of the reference lens interposed therebetween. Like that. Therefore, even when the concave curved surface of the concave lens faces the laser beam, the reflected light can be reliably increased.

Further, in another invention, in addition to the above-mentioned inventions, a laser diode is used as a light source, and a condensing lens is interposed between the laser diode and a collimating lens to thereby emit light emitted from the laser diode. The light is focused on a collimating lens. Therefore, it can be configured as an additional function of the laser autocollimator.

In another invention, in addition to the above-mentioned inventions, a position where the reflected light from the test surface is imaged on the light receiving surface when the test object is not tilted is defined as a standard position. The inclination of the test object is detected by the displacement from the position. As described above, since the other inclination is measured based on the time when the inclination is zero, the inclination in both directions can be accurately detected.

Further, in another invention, in addition to the device for measuring the inclination of a test object according to each of the above-mentioned inventions, a means for adjusting the distance between the test object and the reference lens according to the curvature of the test surface of the test object is provided. Have. For this reason, it is possible to obtain an optimal arrangement in which the amount of reflected light increases according to the state of the curved surface of the test object to be measured.

[0018]

Embodiments of the present invention will be described below. The same members as those shown in FIG. 5 are denoted by the same reference numerals and described, and the description thereof will be omitted or simplified.

FIG. 1 is a diagram showing an embodiment of a tilt measuring apparatus according to the present invention. In this tilt measuring device, a linearly polarized (for example, P-polarized) laser beam emitted from a laser diode (LD) 11 serving as a light source is condensed by a condenser lens 12, and a pinhole disposed at the focal point thereof 13 and is reflected by a total reflection mirror 14. Further, this linearly polarized laser light is reflected by the polarization beam splitter 15, passes through the λ / 4 plate 16, and becomes circularly polarized. After that, the light passes through the collimator lens 17 and becomes parallel light, which is emitted to the test object lens 18 which is the test object.

The reflected light reflected by the test lens 18 returns to the optical path in the reverse direction, first enters the reference lens 20 and is converted into parallel light, and then is condensed by the collimating lens 17.
After passing through the λ / 4 plate 16, it becomes linearly polarized (for example, S-polarized), passes through the polarizing beam splitter 15, and
9 is formed. The test lens 18 is an aspherical plastic lens.

In the above configuration, the feature of the present invention resides in that the reference lens 20 is disposed between the collimating lens 17 and the test lens 18.

That is, the parallel light that has passed through the collimating lens 17 passes through the reference lens 20 and is condensed at its focal point O. Here, assuming that the test surface of the test lens 18 is a spherical surface, the focal length and position of the reference lens 20 and the test lens are set so that the center of the radius of curvature of the test surface coincides with the focal point O of the reference lens 20. Set the position of 18. This allows
When the test object lens 18 has no inclination, the incident angle of the light illuminating the test surface becomes 0, and all the reflected light is incident to return to the same optical path as the optical path. To form an image on the light receiving element 19.

The position of the reference lens 20 has an allowable range, and it is not always necessary to make the center of the radius of curvature of the surface of the test object lens 18 coincide with the focal point O of the reference lens 20. Even if the two do not exactly match, the angle of incidence can be made smaller than in the conventional case where the parallel light is applied to the test surface,
The amount of reflected light reaching the light receiving element can be increased by that amount, and the inclination measurement of the test surface can be easily performed.

The surface to be inspected of the object lens 18 does not necessarily have to be spherical. Even if it is an aspherical lens, the reflected light can be efficiently collected by using the reference lens 20. Tilt measurement can be facilitated.
In the case of this aspheric lens, it is preferable that the closest spherical surface is approximated, and the center of the radius of curvature coincides with the focal point O of the reference lens 20. If at least one radius of curvature of the aspherical lens is employed, the amount of reflected light is increased as compared with the related art. Therefore, at least one radius of curvature of each curved surface of the aspherical lens may be employed.

Further, when the object lens 18 is a concave mirror or a concave lens 21, as shown in FIG.
The focal length and position of the reference lens 20 and the position of the concave lens 21 are set so as to be away from the focal point and the center of the radius of curvature of the concave surface coincides with the focal point O of the reference lens 20.
Also in this case, the reference lens 20 does not necessarily have to be at a position where they both exactly match.

Note that the focal length and position of the reference lens 20 need to be appropriately selected according to the radius of curvature and the effective diameter of the test lens 18. FIGS. 3A and 3B show that a reference lens 20 having a short focal length and a reference lens 20 having a long focal length are connected to the test lens 18 having the same radius of curvature. And the focal point O of the reference lens 20 is aligned. FIG. 3 (B)
As shown in the figure, the width of the light flux of the transmitted light of the reference lens 20 is
If the focal length and position of the reference lens 20 are determined so as to be smaller than or equal to the effective diameter of the test lens 18, the amount of light applied to the test lens 18 increases, and the reflected light is efficiently used for measurement. be able to.

As shown in FIG. 4, a main body side barrel 31 supporting the collimating lens 17 and a screw mount 32 supporting the reference lens 20 are screwed together so that the center of the radius of curvature of the lens 18 to be inspected can be adjusted. The position of the reference lens 20 may be adjusted back and forth according to the radius of curvature of the test lens 18 so that the focus O of the reference lens 20 coincides. The body-side barrel 31 and the screw mount 32 serve as means for adjusting the distance between the test object and the reference lens according to the curvature of the test surface of the test object.

Here, if the radius of curvature of the test lens 18 increases, the position of the reference lens 20 is lowered, and the distance between the test lens 18 and the reference lens 20 is reduced. On the other hand, if the radius of curvature of the test lens 18 becomes smaller, the position of the reference lens 20 is raised, and the test lens 18 and the reference lens 20 are moved.
Increase the distance of As can be seen from FIG. 3, by preparing the reference lens 20 having a longer focal length in advance, the irradiation light when adjusting the position of the reference lens 20 back and forth according to the curvature of the test object lens 18. The increase or decrease can be minimized.

This tilt measuring device is used as a laser autocollimator. As a specific usage example, CD
Optical axis deviation in the process of bonding a collimator lens in an optical pickup device for an optical medium such as a DVD or an optical medium can be confirmed. In addition, in addition to the above, inspection of the lens inclination in the attaching / curing step of the objective lens of the optical pickup device, confirmation of the inclination of the sleeve when the objective lens is temporarily placed on the sleeve,
It can also be used for lens tilt inspection when the objective lens is driven.

Each of the above embodiments is an example of a preferred embodiment of the present invention. However, the present invention is not limited to this embodiment, and various modifications may be made without departing from the scope of the present invention. It is possible. For example, the test object lens 18 and the concave lens 21 are described as examples of the test object, but other objects having a spherical surface and a curved surface similar thereto may be used.

Also, an integrated lens of the collimating lens 17 and the reference lens 20 is disposed,
7 and the reference lens 20 alone may be omitted.
Further, the condenser lens 12 may not be provided.
In the case of a concavely curved test object, the reference lens 20 may be a concave lens instead of a condenser lens to diffuse light. Further, when the test lens 18 is parallel (reference position), it is preferable to arrange the reflected light at the center of the light receiving element 19, but when the tilt direction is always one side, one end of the light receiving element 19 is preferable. It may be configured such that the reflected light in the parallel state comes to the side.

[0032]

As described above, according to the present invention, a reference lens is provided between a collimator lens and a test object, which collects parallel light and enters the curved surface of the test surface at a right angle of incidence. By arranging the reference lens, more reflected light from the test surface can be collected by the reference lens than when parallel light is directly incident on the test surface. Thereby, it is possible to increase the amount of light to form an image on the light receiving element via the collimating lens,
It is possible to improve the measurement accuracy of the inclination of the test object whose test surface is a curved surface.

When the surface of the test object is a curved surface having a spherical or aspherical surface, the focal position of the reference lens and the center position of at least one radius of curvature of the test object coincide with each other. When the position of the reference lens is set, the incident angle of the light illuminating the test object becomes 0 or near 0, and a large amount of reflected light returning in the coming direction is obtained, and a large amount of reflected light is received through the collimating lens. An image can be formed on the element.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of a device for measuring the inclination of a test object according to the present invention.

FIG. 2 is a diagram showing a positional relationship in a case where an object lens is a concave mirror in the object inclination measuring apparatus of FIG. 1;

FIG. 3 is a diagram for explaining the relationship between the curvature and effective diameter of an object lens, the focal length and the position of a reference lens in the object inclination measuring apparatus of FIG.

FIG. 4 is a diagram showing a configuration example in which the position of a reference lens can be adjusted in the device for measuring the inclination of a test object in FIG. 1;

FIG. 5 is a view showing a basic configuration of a conventional laser autocollimator, and is a view for explaining how reflected light from a test surface becomes diffuse light when the test surface of the test object is a curved surface.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Laser diode (light source) 12 Condensing lens 13 Pinhole 14 Total reflection mirror 15 Polarization beam splitter 16 λ / 4 plate 17 Collimating lens 18 Test object lens (Test object) 19 Light receiving element 20 Reference lens 21 Concave lens 31 Body side Lens barrel 32 screw mount

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Toshiyuki Inoue 4600 Nakashu, Oaza, Suwa-shi, Nagano Nisshin Koki Co., Ltd. In-house F term (reference) 2F065 AA35 AA37 BB05 CC22 DD05 EE05 FF01 FF43 FF49 GG06 GG12 HH09 HH13 JJ09 JJ16 JJ26 LL04 LL12 LL30 LL36 LL37 PP02 QQ28

Claims (8)

[Claims] 1. A light source, a light receiving element, and a collimating lens for irradiating the object side with collimated light emitted from the light source, condensing the reflected light, and forming an image on the light receiving element. ,
In an object inclination measuring apparatus for measuring the inclination of the object from the imaging position of the light receiving element, disposed between the collimating lens and the object,
A tilt measuring device for a test object, comprising: a reference lens for condensing or diffusing the parallel light to irradiate the test object from a direction perpendicular to a tangent to a curved surface of the test object. 2. When the surface of the test object is a curved surface having a spherical or aspherical surface, a focal position of the reference lens and a center position of at least one radius of curvature of the test object are determined. 2. The apparatus according to claim 1, wherein the position of the reference lens is set so as to match. 3. The light beam emitted from the reference lens has a light flux width equal to or smaller than a width of the test surface of the test object in a direction orthogonal to an optical axis, and is incident on the test surface. The apparatus according to claim 1, wherein the collimating lens is provided as described above. 4. When the test object is a convex lens or a concave lens, the focal length and the position of the reference lens are set so that the width of the light flux of the transmitted light of the reference lens is smaller than or equal to the effective diameter. 4. The apparatus for measuring the inclination of a test object according to claim 1, wherein the apparatus is configured to be set. 5. When the test object is a concave lens, the concave lens is arranged at a position further away from the collimating lens with the focal position of the reference lens interposed therebetween, and the measurement is performed. Item 5. An apparatus for measuring the inclination of a test object according to Item 1, 2, 3, or 4. 6. A laser diode is used as the light source, and a condensing lens is interposed between the laser diode and the collimating lens so that light emitted from the laser diode is condensed on the collimating lens. The tilt measuring device for a test object according to claim 1, wherein: 7. A standard position is a position at which reflected light from the test surface when the test object is not tilted is imaged on a light receiving surface.
7. The apparatus for measuring the inclination of a test object according to claim 1, wherein the inclination of the test object is detected based on the displacement from the standard position. 8. The apparatus according to claim 1, further comprising means for adjusting a distance between the test object and the reference lens according to a curvature of a test surface of the test object. An apparatus for measuring the inclination of a test object according to the above.