JPS6255542A - Optical system inspecting device - Google Patents

Abstract

PURPOSE:To enable the inspection of an optical system containing an asymmetrical element such as axial deviation of a lens, by providing an objective lens for a metal microscope, a pinhole and an opening dia. Varying aperture between a laser light source and the optical system to be inspected. CONSTITUTION:When a laser light of a laser light source 1 is focused with an objective lens 8 for a metal microscope to pass only a bright part in the center of a diffracted light with the lens 8 through a pinhole 9 placed at the focusing point of the laser light, a spherical wave without noise is obtained expanding radially from the position of the hole of the pinhole 9. Then, an aperture allows a part of the spherical wave to pass and be incident into an optical system 4 being inspected and hence, a transmission light through the optical system forms a concentrical diffraction pattern at the position of the pinhole 6. Then, a second finely mobile base 7 is adjusted to pass a bright spot through the pinhole 6, and then the graduation of the finely mobile base 7 is read out, thereby permitting the fine measurement of the position of an emission light beam. Then, the position of the emission light beam is measured about respective incident positions and incident angles moving a first finely mobile base 5. Thus, the inspection of the optical system 4 can be inspected.

Description

[Detailed Description of the Invention] [Industrial Application Field] - This invention involves a method in which a narrow beam of light is incident on an optical system from a predetermined position at a predetermined angle, and the output light is emitted onto a screen placed behind the optical system. This relates to an optical system inspection device for measuring the position and inspecting the optical path within the optical system by ray tracing.〇 [Prior art] Conventionally, as a device for inspecting the optical path of an optical system, the device shown in Fig. 2 is used. There was something shown. In the figure, (1) is a laser light source, (2) is a telephoto optical system for converting the laser light generated from the laser light source fll into parallel rays, (31 is an aperture, +
41Jri optical system to be tested, (5) is the first fine movement table for adjusting the incident position and direction of the thin beam to the optical system to be tested (4), (6) is the optical system to be tested (4) (7) is a second fine movement table for adjusting the position of the pinhole (6).

Next, the operation will be explained. The laser light emitted from the laser light source (1) is converted into parallel light KL by the telephoto optical system (2).

When a thin parallel beam is taken out by the diaphragm (32) and made to enter the optical system under test (4) from a prescribed position at a prescribed angle by adjusting the first fine movement table (5), the beam is The refraction according to Snell's law is repeated on each surface of the lens constituting the analysis system (4), and the transmitted light passes through the pinhole (6).
), and adjust the second fine movement table (7) so that the light beam passes through the pinhole (6) when the optical system to be examined (4) is not placed.
9. Read the scale of the second fine movement table (7) using the position of ) as the origin. The optical system can be inspected by comparing it with the values calculated by ray tracing.

[Problem that the invention seeks to solve]

In conventional optical system inspection equipment, even if a thin parallel light beam is incident, the light that has passed through the optical system to be inspected (4) is
4), the light beams are no longer parallel, and therefore the light beams become thick at the detection position of the emitted light, that is, on the pinhole (6), resulting in a problem that the position detection accuracy is low. In terms of geometrical optics, if you make the aperture smaller and make the incident light beam narrower, you should be able to make the output light beam narrower, but in reality, the intensity of the light decreases, making it difficult to detect the position of the light beam, and the diffraction at the aperture makes the output light beam narrower. Improving accuracy is difficult because the light beam spreads out.

This invention was made in order to solve the above-mentioned problems, and is designed to ensure that the intensity of the light beam emitted from the optical system under test is sufficient.
Means for solving the problems of GC aimed at obtaining an optical system inspection device that can clearly see the center position of the emitted light beam and measure the position of the emitted light beam with high precision] The optical system inspection device according to the present invention is , an objective lens for a metallurgical microscope, a pinhole, and a diaphragm with a variable aperture diameter are provided between the laser light source and the optical system to be tested.

[Effect]

The objective lens in this invention condenses the laser beam and produces a concentric diffraction pattern with a bright center at the condensing point. If a pinhole about the diameter of the central bright part is placed at the focal point, a spherical wave centered at the focal point can be obtained. Since the aperture allows only a portion of this spherical wave to pass through, diffraction occurs due to the aperture. When the diffracted light is made incident on the optical system to be tested and the aperture of the diaphragm is adjusted, the transmitted light of the tested lens becomes a bright concentric diffraction bump in the center, and the center position of the emitted light can be clearly seen.

〔Example〕

FIG. 1 is a block diagram of an optical system inspection apparatus showing an embodiment of the present invention. 2 In FIG. 1, (l) is a laser light source, (
3) is the aperture, (4) is the optical system to be tested, (5) is the first fine movement table, (6) is the pinhole, (7) is the second fine movement table, (8
) is an objective lens for a metallurgical microscope, and (9) is a pinhole that is placed at the focal point of the laser beam and allows only the bright part in the center to pass through.

Next, the operation will be explained. The laser beam emitted from the laser light source fi+ is focused by an objective lens (8), and a pinhole (9) placed at the converging point of the laser beam is inserted into the objective lens (2).
), a spherical wave without spatial noise can be obtained that spreads radially from the position of the pinhole (9) by passing only the central bright part of the diffracted light. The diaphragm (3) allows a part of this spherical wave to pass through and enters the optical system to be tested (4), so the transmitted light from the optical system to be tested (4) passes through the pinhole (6).
Create a concentric diffraction pattern at the position. This concentric pattern passes from the pinhole (6) through the optical system to be tested (4) to the diaphragm, ! :l When looking at f31, depending on the number of fresnels 7 that fit into the hole of the diaphragm [3], by adjusting the hole diameter of the diaphragm (3), a bright spot will appear in the center of the concentric button. can be put into a state where it is possible. In this state, adjust the second fine movement table (7) to find the bright spot or pinhole (6).
By reading the scale of the second fine movement stage (7), the position of the emitted light beam can be precisely measured. Move the first fine movement table (5) to each incident position,
The optical system (4) to be inspected can be inspected by measuring the position of the emitted light beam with respect to the angle of incidence.

In the above embodiment, the hole (6) is used to detect the position of the emitted light beam, but a diffraction batten may be projected onto a screen or a light receiving surface of an image sensor.

〔Effect of the invention〕

As described above, according to the present invention, the center position of the light ray can be clearly seen by using single diffraction, so ray tracing can be actually performed with high precision, and the axis of the lens, which was previously difficult to inspect based on imaging characteristics. Lateral distortion of the optical system, including asymmetric elements such as misalignment and lens tilt, is now possible. Furthermore, according to this invention, since the measurement pattern directly corresponds to the ray tracing method used for optical design, the correspondence with the design value is clear, and the optical system can be corrected if there is a deviation from the design value. It's easy to do.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an optical system inspection device according to an embodiment of the present invention, and FIG. 2 is a diagram showing a conventional optical system inspection device. In the figure, (1) is a laser light source, +31Fi aperture,
(4) is the optical system to be tested, +51U first fine movement table, (6
1, +91 is the pinhole, (7) is the second fine movement table, (8
) is an objective lens for metallurgical microscopes. In the drawings, the same or corresponding parts are designated by the same reference numerals.

Claims (1)

[Claims] A laser light source, an objective lens for a metallurgical microscope to focus the laser light emitted from this laser light source, a pinhole placed at the focal point of the laser light, and a part of the diverging laser light emitted from this pinhole to pass through. A diaphragm with a variable aperture diameter, a first fine movement stage for adjusting the position and angle of the optical system to be tested with respect to the diverging laser beam limited by the diaphragm, and a first fine movement stage for adjusting the position and angle of the optical system to be tested with respect to the diverging laser beam limited by the diaphragm, and a An optical system inspection device comprising: a pinhole attached to a second fine movement table for adjusting the position so that the center portion passes through.