JPH09210856A - Measuring apparatus for afocal optical system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a measuring apparatus which suppresses a measuring error to a minimum by. a method wherein a collimator in which a slit for object- position setting at a lens to be inspected is used as a light source is formed in such a way that it can be moved to a direction at right angles to an optical axis and that it can be turned around the position of the slit. SOLUTION: A collimator 11 is made freely movable on a longer X-axis stage 36 and a longer Y-axis stage 38 which are at right angles to each other, and it can be turned by a rotary stage 32 around a slit 50 in a slit plate 35. In a measurement on an axis, light from the slit 50 is passed through a lens 41, to be inspected, and a lens 42, and it forms an image in a condensing point 46. The light forms an image on an area CCD 47 by a lens 43, an output is A/D-converted and FFT-processed, and the image performance value of an afocal optical system at every frequency is found. In a measurement outside the axis, the collimator 31 is moved to an outside-of-axis collimator position 51, the stage 32 is turned, a longer rotary stage 45 is turned together with a pupil position 37, the lenses 42, 43 and the CCD 47, and it is aligned with a reference position in which the output shape of a slit image is set. After that, an image performance value is found in the same manner.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring quality characteristics of an afocal optical system used for a finder, a telescope, an opera glass, etc. of a camera.

[0002]

2. Description of the Related Art As a method of measuring the performance of a telescope or the like, a plurality of slits are provided at the focus position of a collimator instead of an object at an infinite distance, and a lens to be inspected (telescope) is placed on the optical path of the light emitted from the collimator. The telescope + focusing lens performance is measured from the output shape of the slit image formed by focusing the image with a focusing lens and then forming it on the line sensor with a magnifying lens in an appropriate size. There is. A conventional example of such a measuring method will be described.

FIG. 3 schematically shows a conventional image quality measuring device for a telescope. In FIG. 3, a light source 2 is provided inside the collimator 1. A slit plate 3 is provided behind the light source 2 at a constant distance. On the center of the slit plate 3, there is a slit 5 for on-axis measurement, and on both sides of this slit 5 are slits 4 and 6 for off-axis measurement.
Is provided. Inside the collimator 1, the slit plate 3
A collimator lens 8 is provided behind (on the right side in the drawing).

A test lens 9 composed of two lenses is arranged behind the collimator 1 at a constant distance, and a detection unit 11 is arranged further behind at a constant distance from the test lens 9. ing. The detection unit 11 has A
A / D conversion board and a personal computer for calculating the image performance value of the afocal optical system are connected. Detector 11
Is hollow, and a condenser lens 12 is arranged inside the front side, that is, on the side of the lens 9 to be inspected. Condensing lens 1
A magnifying lens unit 17 is arranged behind the lens 2. Inside the magnifying lens unit 17, a magnifying lens 14 is provided on the condensing lens 12 side, and a line sensor 16 is provided behind the magnifying lens 14.
Is attached. A power source, an A / D conversion board, and a personal computer are connected to the line sensor 16.
A switching mirror 19 is arranged between the magnifying lens 14 and the line sensor 16, and the position of the image can be confirmed by passing through the switching mirror 19 and the eyepiece lens 18.

Next, a measuring method using the above image performance measuring apparatus will be described. First, at the time of on-axis measurement, the optical axes of the collimator 1, the lens 9 to be inspected, the condenser lens 12, and the magnifying lens 14 are aligned as shown in FIG. The parallel light 20 emitted from the on-axis slit 5 and passed through the collimator lens 8 passes through the lens 9 to be inspected, and then is focused on the first focus point 13 by the condenser lens 12. Further, the formed slit image is formed on the line sensor 16 by the magnifying lens 14, and the line sensor 16 arranged so as to be orthogonal to the slit image obtains an output as a sectional shape of the slit image. After the D conversion, FFT (Fast Fourier Transform) processing is performed by a personal computer, and the image performance value of the afocal optical system for each frequency is measured.

Further, when the off-axis is measured by changing the incident angle, the entire detecting section 11 is examined by the eyepiece 18 while observing each image of the off-axis slits 4 and 6 on the slit plate 3. The image performance value of the afocal optical system can be measured by the same method as described above by rotating the eye point 10 with the slit image as the center of the visual field.

In the measurement of the peripheral portion, T, R (Tang)
Since it is necessary to perform measurement by switching the direction (tangential line) and the direction (Radial), the slit plate 3 is provided with slits for measuring the off-axis T and R directions in a concentric circle in advance. Then, according to the measuring method in the T and R directions, the slit plate 3 is rotated and switched. At the same time, the direction of the line sensor is also rotated and aligned around the sensor center so as to be orthogonal to the slit image in the T and R directions. Can be measured in the same manner as in the above example.

[0008]

By using the above method, it is possible to compare and measure the performance of telescopes. However, the incident angle of view is, for example, ± 20 ° to ± 4.
When measuring an afocal optical system as large as 0 °, it is necessary to set a large gap between the slits for the off-axis on the axis of the focal plane of the collimator. According to the conventional measurement method, the focus of the collimator lens 8 is reduced. Since the distance and effective diameter are limited, the actual measurement angle of view is limited to ± 5 °.

Further, the parallel light from the slits 4 and 6 corresponding to the peripheral light cannot be regarded as an optical ray and an aberration occurs, so that the on-axis and off-axis measurement conditions are different, and the measurement accuracy is different. Will get worse.

Further, in the case of off-axis measurement, Tangent
It is necessary to measure the ial direction and the Radial direction,
It is necessary to make the slit image on the line sensor 16 and the line sensor 16 orthogonal to each other each time the viewing angle of measurement is changed.
When the slits 4 and 6 and the line sensor 16 are rotated, they are affected by eccentricity or a positional error, which makes it very difficult for the viewer of the detection unit 17 to perform alignment, and the workability of measurement deteriorates.

The present invention has been made in order to solve the problems of the prior art as described above, and a large measurement angle of view can be obtained, a measurement error can be minimized, and a slit image when the viewing angle is changed. Is easy to align, and T,
It is an object of the present invention to provide a measuring device for an afocal optical system that does not disappear even when decentered when the R direction is switched, facilitates position adjustment, and improves the efficiency of measurement work. .

[0012]

According to the first aspect of the present invention,
An afocal optical system measuring device that quantitatively measures the image performance of the afocal optical system used for camera viewfinders, telescopes, opera glasses, etc., and a slit for setting the object position of the lens under test. In addition to providing a collimator that uses a light source as a light source, a device that can move the collimator in the direction perpendicular to the optical axis and that can rotate about the slit position as a rotation center, and an area CCD in the slit image detection unit It is characterized by being

The invention according to claim 2 is characterized in that the slit image on the image receiving surface of the area type CCD is displayed on a monitor to align the optical axes.

The invention described in claim 3 is characterized in that a light source section using a pinhole instead of the slit provided in the collimator and an area CCD are used in the light receiving section.

According to a fourth aspect of the present invention, the image performance value of the afocal optical system in any direction is calculated from the CCD output value of the pinhole image using a collimator having a pinhole and an area CCD. Characterize.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a measuring apparatus for an afocal optical system according to the present invention will be described below with reference to the drawings. In FIG. 1, the collimator 3 on the light source side
Reference numeral 1 is hollow, and is attached to a carrier (not shown) that can be freely moved on a long X stage 36 and a long Y stage 38 orthogonal to the long X stage 36. A rotary stage 32 is mounted between the carrier and the collimator 31 so that the collimator 31 can be supported and rotated, and the rotation angle of the collimator 31 can be accurately read. The rotation center of the rotary stage 32 can rotate around the slit 50 of the slit plate 35.

A light source 34 is arranged inside the collimator 31 and at one end of the collimator 31. The filter 33 is arranged behind the light source 34, and the slit plate 3 is provided behind the filter 33 (to the right in FIG. 1).
5 is located behind the slit plate 35 and has a collimating lens 28.
Is provided. The slit 50 is formed in the slit plate 35 at a position orthogonal to the optical axis of the light source 34. Therefore, the light flux from the light source 34 passes through the slit plate 35 by the on-axis slit 50 and is applied to the collimator lens 28.

The lens 41 to be inspected is attached to a rotary stage 40 provided on the long X stage 36 and rotatable around the optical axis with respect to the optical axis, and can be rotated together with the rotary stage 40 about the optical axis. Has become. A diaphragm having a pupil diameter corresponding to each lens 41 to be inspected can be attached to the pupil position 37 of the lens 41 to be inspected. A condenser lens 42 is arranged behind the pupil position 37 such that the focal position on the front side thereof matches the pupil position 37.

The image of the slit is formed at the first condensing point 46,
Further, it is magnified to an appropriate size by the magnifying lens 43 and an image is formed on the area CCD 47. Area CCD 47
Outputs a signal corresponding to the formed slit image, and the output is A / D converted and the MFT calculation is performed for each frequency by the FFT board. Moreover, the personal computer performs a predetermined calculation process and displays the graph. Done. The condensing lens 42 and the magnifying lens 43 are attached to a long rotary stage 45 and have an area CCD 47.
The CD camera 48 is also attached to the long rotary stage 45 via the camera support 49. The long rotary stage 45 has the left end portion in FIG.
6 is attached so as to be rotatable around the pupil position.

Next, a measuring method using the measuring device for the afocal optical system will be described. First, at the time of on-axis measurement, the collimator 31, the test lens 41, and the condenser lens 4
2. The optical axis of the magnifying lens 43 is aligned. The parallel light emitted from the slit 50 and passing through the collimator lens 28 passes through the lens 41 to be inspected, and then forms an image at the first condensing point 46 by the condensing lens 42. Further, the formed slit image is formed on the area CCD 47 by the magnifying lens 43, and the area CCD arranged so as to be orthogonal to the slit image.
After obtaining the output as the cross-sectional shape of the slit image at 47, A /
D-converted and FFT (Fast Fourier Transform) by PC
Processing is performed to measure the image performance value of the afocal optical system for each frequency.

In the case of off-axis measurement, the collimator 31 is moved to the off-axis collimator position 51 shown by the dotted line. Along with this, the rotary stage 32 is attached to the slit 5 of the slit plate 35.
The light beam from the collimator 31 which can be regarded as a light source by rotating it about 0 as a center and the off-axis slit is a lens 4 to be inspected
Incident on 1. Further, the pupil position 37, the condenser lens 42, the magnifying lens 43, the area CCD 47, etc. attached to the long rotary stage 45 are also integrally rotated together with the long rotary stage 45, and the output shape of the slit image after A / D conversion is obtained. Observe on the monitor and adjust to the preset reference position. In this state, an output is obtained from the CCD 47, the output is A / D converted, and FFT processing is performed, whereby the image performance value of the afocal optical system for each frequency can be measured.

In this way, the slit image is transferred to the area CCD.
By detecting and positioning at 47, a wide field of view can be seen on the monitor, so that it is possible to easily position the slit image when the viewing angle is changed.

The tangential direction switching and collimator 3 for rotating the lens 40 to be inspected with the optical axis as a reference.
Since the image position does not disappear from the visual field due to the eccentricity when the Radial direction is switched by the movement of 1, the image position can be easily adjusted and the measurement work can be made efficient.

Further, by using the optical axis ray of the collimator 31 for both the on-axis measurement and the off-axis measurement of the lens 41 to be inspected, the conditions on the object side are the same, so that the measurement error can be reduced. By changing the position and the rotation angle of the collimator 31, it is possible to measure the test lens having a wide angle of view.

A pinhole plate having a pinhole is used in place of the slit plate 35 used in the light source section of the collimator 31, and the pixel position at which the maximum output is detected is detected from the output distribution of the pinhole image on the area CCD 47. It is also possible to extract the pixel output in an arbitrary direction passing through the pixel and calculate the MTF value from the shape by using the above-described measurement method. For example, as shown in FIG. 2, when an image denoted by reference numeral 62 is formed on the area CCD 47, pixels in the X direction and pixels in the Y direction are taken out at the center portion 63 of the image, and this X
The MTF value can be calculated from the pixel shape 65 in the direction and the pixel shape 64 in the Y direction. By using this method, it becomes unnecessary to mechanically switch between the T and R directions, and the efficiency of measurement work can be improved.

[0026]

According to the present invention, a collimator having a slit as a light source is provided for setting the object device of the lens to be inspected, and the collimator is moved in the direction perpendicular to the optical axis and the slit position is set as the rotation center. Since a device capable of rotating is provided and an area type CCD is provided in the slit image detecting portion, a large measurement angle of view can be obtained and measurement error can be minimized. Further, it becomes possible to simplify the alignment of the slit image when the viewing angle is changed. Further, the image does not disappear due to the eccentricity when the T and R directions are switched, the position adjustment becomes easy, and the efficiency of the measurement work can be improved.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a measuring apparatus for an afocal optical system according to the present invention.

FIG. 2 is a diagram showing a method of detecting a pinhole image by the measuring device of the focal optical system.

FIG. 3 is a sectional view showing an embodiment of a conventional measuring apparatus for an afocal optical system.

Claims (4)

[Claims] 1. A viewfinder for a camera, a telescope,
An afocal optical system measuring device that quantitatively measures the image performance of an afocal optical system used in opera glasses, etc., and is provided with a collimator using a slit as a light source to set the object position of the lens under test. At the same time, this collimator is provided with a device capable of moving in a direction perpendicular to the optical axis and rotating about the slit position as a rotation center, and an area type CCD is provided in the slit image detecting portion. Focal optics measuring device. 2. The measuring device for an afocal optical system according to claim 1, wherein a slit image on the image receiving surface of the area type CCD is displayed on a monitor to align the optical axes. 3. A light source section using a pinhole instead of the slit provided in the collimator, and an area type C in the light receiving section.
The measuring device for an afocal optical system according to claim 1, wherein a CD is used. 4. A collimator having the pinhole,
4. The apparatus for measuring an afocal optical system according to claim 3, wherein an area type CCD is used to calculate the image performance value of the afocal optical system in an arbitrary direction from the CCD output value of the pinhole image.