JPS5940253B2 - autocollimator - Google Patents

Description

[Detailed description of the invention] The present invention relates to an autocollimator.

In general, an autocollimator is an optical system that makes a light beam perpendicularly incident on a flat reflecting mirror and returns the reflected light beam through the same optical path as the incident light beam. In other words, an autocollimator used in a so-called lens eccentricity measurement device uses a lens to be measured instead of the above-mentioned plane reflecting mirror, makes a ray of light incident perpendicularly to the convex or concave surface of the lens, and converts the reflected ray to the incident lens. The process involves returning the same optical path as the light beam in the opposite direction. However, in the case of the latter autocollimator, which requires a convex or concave surface as the reflective surface, the relative distance between the reflective surface and the autocollimator may be changed depending on whether the reflective surface is convex or concave. I had to. Furthermore, autocollimators that maintain the relative distance unchanged have limitations on the curvature of the reflective surface that can perform autocollimation.
An object of the present invention is to provide an autocollimator that can perform autocollimation regardless of the curvature of the reflective surface, ie, whether it is convex, concave, or flat, without changing the relative distance between the reflective surface and the autocollimator.

The autocollimator according to the present invention arranges a collimator lens, a movable positive lens replacement positive or negative lens, and a projection positive lens in the order of the traveling direction of the light beam, and uses either the positive or negative lens as the interchangeable lens. Therefore, auto-collimation is performed regardless of the unevenness of the reflecting surface, and by moving the movable lens in the optical axis direction, regardless of changes in the curvature of the reflecting surface. In other words, the light emitted from the projection lens is is made perpendicular to the reflecting surface.

Next, an embodiment in which the autocollimator according to the present invention is applied to a lens eccentricity measuring device will be described with reference to the drawings. In FIG. 1, a point light source is created by a light source 2, a condensing lens 4, and a pinhole 6. The collimator lens 8 converts the light beam from the point light source on the pinhole 6 into parallel light. positive lens 10
is movable along the optical axis of the collimator lens 8.
The focal length of this movable lens 10 is a positive lens 12a, which will be described later.
The focal length f02 is selected to be larger than the focal length f02. This positive lens 12a is configured to be replaceable with a negative lens 12b having the same focal length -f42. Further, the positive lens 12a or the negative lens 12b is arranged at the front focal position of the fixed positive lens 14 for projecting light beams. That is, the interchangeable lens and the projection lens 14 are separated by the focal length Fl4 of the latter. The upper surface 16a of the test lens 16 that reflects the light beam from the fixed lens 14 for projection is the fixed lens 1
The lens 16 to be tested is placed so that it is at the rear focal position of 4. Further, the lens 16 to be tested is fixed in the optical axis direction. As above, the collimator lens 8, the movable lens 10,
An autocollimator is constituted by the exchangeable positive or negative lens 12a or 12b and the fixed positive lens 14. With this configuration, the positive lens 12 as shown in the figure can be used as an interchangeable lens.
When using a, autocollimation can always be performed even if the reflective surface 16a of the test lens 16 is a convex surface of any curvature toward the autocollimator.

This is illustrated below. FIG. 2a shows the case where the reflective surface 16a of the lens to be tested is flat, that is, its radius of curvature is infinite. In the figure, the movable positive lens 10 is the interchangeable positive lens 1.
The positive lens 10 is placed at a position separated from the lens 2a by the focal length FlO of the positive lens 10 (hereinafter referred to as the reference position). Therefore, the parallel light incident on the movable lens 10 is transmitted to the interchangeable lens 12.
The light is focused on the principal plane of a. This principal plane is fixed lens 1
4, the above-mentioned light beam is again converted into parallel light by the lens 14, enters the plane 16a perpendicularly, is reflected there, and travels in the same optical path as the incident light beam in the opposite direction. Next, in Fig. 2b, there is a virtual reflecting surface 1 whose radius is zero.
6a (this reflective surface is drawn as a dot in the figure) is shown. In this case, the movable lens 10 is moved from the reference position shown in FIG. 2a toward the unillustrated collimator lens 8 by the focal length Fl2 of the interchangeable lens 12a. (Hereinafter, this position will be referred to as the farthest position.) With this, the movable lens 1
The parallel light incident on the lens 12a is condensed at the front focal position of the interchangeable lens 12a.
a, the light becomes parallel light again, and is focused by the fixed lens 14 on its focal position, that is, on the reflective surface 16a. Therefore, the light reflected here also returns along the incident optical path in the opposite direction, as described above. As shown in FIG. 1, in the case of a convex reflecting surface with a radius of an arbitrary value between the above-mentioned extremes, that is, infinity and zero, as shown in FIG. By moving to an appropriate position between the farthest position in FIG. b, the light beam passing through the fixed lens 14 can be converged toward the center of curvature 18 of the reflective surface 16a. Therefore,
All the light rays from the fixed lens 14 are perpendicularly incident on the reflective surface 16a, and the reflected light there travels in the opposite direction along the incident optical path. Thus, by inserting the positive lens 12a into the optical path of the autocollimator and moving the movable lens 10 to a position between the reference position and the farthest position, the autocollimator becomes convex towards it. The light beam emitted from the autocollimator can be made perpendicular to a reflecting surface of any curvature. Next, a case where the reflective surface is a concave surface facing the autocollimator will be described.

As shown in FIG. 3, instead of the above-mentioned positive interchangeable lens 12a, a focal length -Fl having the same absolute value as that of the positive interchangeable lens 12a is placed at that position.
Insert the negative lens 12b having a diameter of 2. Now, when the reflecting surface is a flat surface, the movable lens 10 may be placed at the reference position, and the optical path at that time is the same as that in FIG. 2a.
Next, when the radius is a virtual reflective surface of zero, move the movable lens 10 from the reference position to the interchangeable lens 12b as shown in FIG. 2c.
The focal length of the lens 12b is 1-Fl2l. The position of the movable lens 10 at this time will be referred to as the closest position. The parallel light incident on the movable lens 10 is condensed by the lens 10 toward the rear focal position of the interchangeable negative lens 12b, so the negative lens 12b converts the light beam into a parallel light flux again, and then the light beam becomes The fixed lens 14 condenses the light onto the reflecting surface 16a, where it is reflected and returns in the opposite direction along the same optical path as the incident light beam. In the case of a concave reflective surface whose radius is an arbitrary value between the above-mentioned infinity and zero, the movable lens 10 is moved to an appropriate position between the reference position and the nearest position as shown in FIG. In this way, the light beam passing through the fixed lens 14 is treated as if it were reflected on the reflecting surface 16.
It can be made to diverge like a ray of light coming out from the center of curvature 20 of a. Therefore, all the light rays from the fixed lens 14 are perpendicularly incident on the reflecting surface 16a, and the reflected light therefrom returns in the opposite direction along the incident optical path. In this way, autocollimation can be performed by moving the movable lens even for a concave reflective surface, no matter what the curvature of the reflective surface is. The optical system for observing the amount of eccentricity of the optical axis of this test lens from the optical axis of the autocollimator is the same as the conventional one, but this will be described below. A beam splitter 22 is provided in between, and the pinhole image reflected by the lens to be examined is formed in front of the eyepiece 24 by the beam splitter 22. The amount of eccentricity of this image from the optical axis is observed with the naked eye or detected photoelectrically by a position sensor 26. As is clear from the above, the amount of movement of the movable lens 10 from the reference position is determined by the curvature of the reflective surface of the test lens. If a scale is provided to indicate this, the curvature of the reflective surface can be determined from the position of the movable lens when performing autocollimation, and conversely, when performing autocollimation on a reflective surface whose curvature is known. , it is sufficient to move the movable lens 10 to the scale of the curvature.
In this embodiment, positive and negative lenses 12a and 12b having focal lengths with the same absolute value are used as interchangeable lenses, and the reflective surfaces of the interchangeable lenses and the test lens are placed in front and behind the projection lens 14, respectively. Since it is placed at the side focal point,
The above-mentioned scale regarding the curvature of a reflecting surface (i.e., a concave and convex reflecting surface with equal radius) having equal absolute values but different signs is symmetrical about the reference position, and furthermore, the absolute values of the magnification of the optical system are also equal. Therefore, it is convenient to handle.

Further, in order to perform autocollimation for convex and concave reflective surfaces of all curvatures, the maximum movement amount of the movable lens 10 only needs to be twice the focal length of the interchangeable lens 12. Therefore, it is possible to speed up the operation. In the above example, a positive interchangeable lens is used for a convex reflective surface, and a negative interchangeable lens is used for a concave reflective surface.However, even in the case of a positive interchangeable lens, For example, by moving the movable lens 10 closer to the collimator lens 8 than the farthest position, auto-collimation can be performed even for a concave reflective surface within a certain range of curvature, and similarly in the case of a negative interchangeable lens. However, for example, by moving the movable lens closer to the interchangeable lens than the closest position, autocollimation can be performed for a convex reflective surface with a certain range of curvature. Therefore, in the present invention, it is not always necessary to use a positive interchangeable lens for a convex reflective surface and a negative interchangeable lens for a convex reflective surface. Similarly, even if the movable lens is moved only between the farthest position and the nearest position, if the reflective surface is shifted from the rear focal position of the projection lens 14 in the optical axis direction, the positive and Negative interchangeable lenses allow autocollimation for concave and convex reflective surfaces of a certain range of curvature, respectively. As described above, according to the present invention, auto-collimation is possible for a reflective surface of any curvature, regardless of whether it is a convex or concave surface, by simply changing the positive or negative polarity of the interchangeable lens depending on the convexity or concavity of the reflective surface.

[Brief explanation of drawings]

FIG. 1 is an optical system layout diagram of an embodiment in which the autocollimator of the present invention is applied to a lens eccentricity measuring device, FIG. 2 is a layout diagram of each lens system of the autocollimator when the reflection surface curvature changes, and FIG. 3 is a diagram showing the arrangement of an optical system for autocollimation on a concave reflective surface. [Explanation of symbols of main parts], 8: Collimator lens, 1
0: Movable positive lens, 12a, 12b: Replacement lens, 1
4: Projection lens, 16a: Reflective surface.

Claims (1)

[Claims] 1. A collimator lens that creates parallel light; a movable positive lens; an interchangeable lens; and a projection lens are arranged in the order of the traveling direction of light, and the positive lens and the negative lens are arranged as the interchangeable lenses. Prepare and correct. An autocollimator characterized in that by exchanging a negative interchangeable lens and moving a movable positive lens in the optical axis direction, light emitted from a projection lens is caused to enter a reflective surface of arbitrary curvature perpendicularly. 2. The autocollimator according to claim 1, wherein a positive lens and a negative lens with equal focal lengths are used as the interchangeable lenses. 3. The autocollimator according to claim 1 or 2, characterized in that the interchangeable lens is disposed at a focal position of the projection lens.