JPH10318883A - Method and device for measuring lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and device for measuring a lens wherein an optical performance at a center part and a peripheral part of a to-be-inspected lens is measured in a short period. SOLUTION: The light from a light source 11 transmits a pattern plate 13, and the transmitted light flux is made into a parallel light flux by a collimator 14, and the parallel light flux is deflected at a first light path deflecting mirror 27 placed on an optical axis to be incident on an incidence angle setting mirror 28, and then made incident at a peripheral part of an imaging lens A by the incidence angle setting mirror 28, and the light flux from the imaging lens A is reflected on an out-going angle setting mirror 32 to be incident on a second light path deflecting mirror 31, and then it is deflected toward the optical axis direction with the second light path deflecting mirror 31 to be incident on an imaging 20, then a pattern image of the pattern plate 13 is imaged on a photo- detecting element 24 by the imaging lens 20, so that a lens performance at a peripheral part of a to-be-inspected lens is measured based on the output from the photo-detecting element. When the first and second light path deflecting mirrors 27 and 31 are taken out, a center part of the to-be-inspected lens A can be measured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for measuring the performance of a lens such as an MTF in an afocal optical system, and more particularly to a technique applicable to measurement of the performance of a lens such as a camera finder, binoculars or a telescope.

[0002]

2. Description of the Related Art FIG. 4 shows the measurement of the lens performance of an afocal optical system such as a finder lens of a camera.
The telescope measuring device of Ealing of the United Kingdom shown below is known. This measures the MTF of the lens to be measured.

In FIG. 4, light emitted from a light source 1 passes through a slit 2, is converted into a parallel light beam by a collimator lens 3, and is converted into a virtual image P by a test lens 4 such as a finder lens.
And the divergent light beam emitted from ′ is formed at the point P by the imaging lens 5. This image is formed on the light receiving element 7 by the magnifying lens 6, and the light quantity distribution is Fourier-transformed by the microcomputer to measure the MTF of the afocal optical system.

[0004]

However, in the above apparatus, the optical performance (MTF) of the central portion of the lens can be measured, but the optical performance of the peripheral portion cannot be measured.

The present invention has been made in view of the above-described circumstances, and has as its object to provide a lens measuring apparatus and a measuring method capable of measuring the optical performance of the peripheral portion of the lens in a short time.

[0006]

To achieve the above object, a lens measuring apparatus according to the present invention comprises a light source, a pattern plate receiving light from the light source, a collimator having the pattern plate as a front focal position. A sample stage for holding a lens to be inspected so that a light beam emitted from the collimator enters, a first optical path bending mirror detachably provided between the sample stage and the collimator; An incident angle setting mirror for causing the reflected light beam from the first optical path bending mirror to enter the test lens as a light beam intersecting the optical axis; an emission angle setting mirror for receiving the light beam emitted from the test lens; A detachable second optical path bending mirror that receives a reflected light beam from the exit angle setting mirror and emits the reflected light beam in the optical axis direction on the optical axis of the inspection lens, and reflection from the second optical path bending mirror. An imaging lens into which the light beam enters A light receiving element provided on an image forming surface of the imaging lens, a light receiving element controller for moving the light receiving element in the optical axis direction, an arithmetic circuit for processing an output of the light receiving element, the arithmetic circuit, and the light receiving element And a control device for controlling the controller.

[0007] Further, the pattern plate has a slit, a first rotating frame which supports the first optical path bending mirror and the incident angle setting mirror and rotates about the optical axis, and A second rotating frame that supports the second optical path bending mirror and the emission angle setting mirror and rotates about the optical axis; and a mirror controller that drives the first and second rotating frames in conjunction with each other. Or a configuration in which the light source has a collimator rotating means rotatable around the optical axis together with the pattern plate and the collimator.

Further, the lens measuring method of the present invention includes:
The light from the light source is transmitted through the pattern plate, the transmitted light is converted into a parallel light by a collimator, and the parallel light is bent by a first optical path bending mirror placed on the optical axis to be incident on an incident angle setting mirror. The incident angle setting mirror makes the light beam intersecting with the optical axis incident on the imaging lens, and the light beam emitted from the imaging lens is reflected by the emission angle setting mirror and made incident on the second optical path bending mirror. The light is bent in the optical axis direction by the optical path bending mirror 2 and made incident on the image forming lens, and the pattern image of the pattern plate is formed on the light receiving element by the image forming lens. It is characterized by measuring the lens performance of the peripheral part.

The first and second optical path bending mirrors are removed, a light beam parallel to the optical axis is made incident on the lens to be inspected, and the image of the pattern plate is formed on the imaging lens by the light beam. It is desirable to measure the lens performance at the center of the lens.

In addition, the first optical path bending mirror and the incident angle setting mirror are integrally rotated about the optical axis of the lens to be tested by a first rotating frame, and are combined with the second optical path bending mirror. The emission angle setting mirror may be integrally rotated with the second rotation frame about the optical axis of the lens to be measured, and the performance of the lens may be measured in an arbitrary direction around the lens to be measured.

The pattern plate may be rotated about the optical axis to measure the lens performance of the central portion and / or the peripheral portion in any direction of the test lens.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 and FIG. 2 are views showing the configuration of an embodiment of the measuring apparatus of the present invention. The light source 11 is supported by a cylinder 12, and a pattern plate 13 and a collimator 14 are integrated into the cylinder 12. The pattern plate 13 is provided with a slit 13a having a width d.
3a overlaps the front focal point of the collimator 14. Further, a collimator rotating means 15 is connected to the cylindrical body 12, and the optical axis X
It becomes freely rotatable around −X ′, so that the direction of the slit 13a can be freely changed. The collimator rotating means 15 is fixed to the light source support 16,
Is fixed to the device base 17.

On the right side of the light source support 16, a device base 17 is provided.
There is a sample table 18 standing upright, and the lens A to be tested is detachable. As the test lens A in the illustrated embodiment, a finder lens of a camera is attached.
On the right side of the sample table 18, there is an imaging lens support table 19,
An imaging lens 20 is attached to this tip.

An automatic stage 21 is mounted on the right side of the imaging lens support 19 so as to be able to advance and retreat in the direction of the optical axis XX '. The automatic stage 21 is provided with a light receiving element support 22. The light receiving element 24 is fixed to the support 22. A line sensor is used as the light receiving element 24, and the light receiving element 22 is rotatable around an optical axis XX '.

A first rotating frame 26 is provided between the lens A to be tested and the collimator 14, and a first optical path bending mirror 27 and an incident angle setting mirror 28 are fixed thereto. The first rotation frame 26 is configured to be rotatable around the optical axis XX ′.

The first optical path bending mirror 27 is detachable.
If it is attached, it reflects the light beam from the collimator 14 to the incident angle setting mirror 28, and if it is removed,
The light beam from the collimator 14 is directly incident on the lens A to be measured. The incident angle setting mirror 28 receives the light beam from the collimator 14 from the first bending mirror, and is capable of adjusting the tilt angle θ of the mirror so that the light beam enters the periphery of the lens A to be measured.

A second rotating frame 30 is provided between the test lens A and the imaging lens 20, and a second optical path bending mirror 31 and an emission angle setting mirror 32 are fixed thereto. You. The second rotation frame 30 is also configured to be rotatable around the optical axis. The second optical path bending mirror 31 is detachable. When the second optical path bending mirror 31 is attached, the light flux emitted from the lens A to be measured and reflected by the emission angle setting mirror 32 is transmitted along the optical axis X-.
The light is emitted so as to overlap with X ′ and sent to the imaging lens 20. When detached, the light flux from the imaging lens A along the optical axis is directly incident on the imaging lens 20.

The emission angle setting mirror 32 can adjust the tilt angle α of the mirror so as to receive the light beam transmitted through the peripheral portion of the lens A to be inspected and send it to the second bending mirror. The output of the light receiving element 24 is input to a microcomputer as a control device 36 via an arithmetic circuit 35 including a binarizing circuit. The automatic stage 21 automatically advances and retreats on the optical axis by the light receiving element controller 37, and the light receiving element controller 37 is driven by the control device 36 according to a predetermined program. Further, the output state of the light receiving element 24, the measurement result, and the like can be monitored by a display (CRT) 38. The mirror controller 39 further controls the first rotation frame 26.
And the second rotating frame 30 are rotated in conjunction with each other.

Next, a method for measuring the lens performance of the peripheral portion of the lens A under test with the first optical path bending mirror 27 and the second optical path bending mirror 31 attached will be described. First, in FIGS. 1 and 2, the light beam emitted from the light source 11 passes through the slit 13 a of the pattern plate 13, becomes a parallel light beam by the collimator 14, is reflected by the first optical path bending mirror 27, and sets the incident angle. The angle θ is appropriately adjusted by the mirror 28 and is incident on the periphery of the lens A to be measured.

The light beam emitted from the lens A to be inspected has its angle α properly adjusted by the exit angle setting mirror 32, and is converted into a light beam along the optical axis by the second optical path bending mirror 31. Incident on. In the imaging lens 20, the light beam transmitted through the periphery of the lens A to be detected is imaged on the light receiving element 24.

The light receiving element controller 37 moves the moving stage 21 back and forth in the optical axis direction so that a slit image is formed on the light receiving element. A line sensor is used as the light receiving element 24, and the slit image is formed so that the slit image is orthogonal to the line sensor.

FIG. 3 (a) shows the slit 13a with the light quantity on the vertical axis and the width direction length of the slit on the horizontal axis.
It becomes a square wave like. The line sensor has a number of elements arranged in a line, and the width δ of one element is the width D of the slit image.
It is much smaller, and includes many elements of the line sensor in the width of the slit image. Therefore, when the output of each element of the line sensor is represented by the output on the vertical axis and the direction in which the elements are arranged on the horizontal axis, as shown in FIG. Become. The control device 36 drives the light-receiving element controller 37 to move the light-receiving element 24 in the optical axis direction, and obtains a position where the above-mentioned peak is maximum.

When the maximum position is found, the light receiving element 24
Is binarized by a binarization circuit as an arithmetic circuit 35,
When the MTF is input to the control device 36 and the MTF is calculated at the specific frequency, the MTF of the peripheral portion of the lens A to be measured can be obtained.

Next, a method of measuring the MTF at the center of the lens A to be measured will be described. First, the first optical path bending mirror 27 and the second optical path bending mirror 31 are removed. Then, the light beam from the collimator 14 directly enters the test lens A, becomes a light beam along the optical axis, and emerges from the test lens A. The emitted light flux reaches the light receiving element 24 via the imaging lens 20, and the following is the same as the case of the peripheral part.

If the above direction is the radial (R) direction, the slit 13a is rotated by 90 ° by the collimator rotating means 15 to the tangential (T) direction if necessary, and the light receiving element 24 is also turned on. Rotate 90 ° so as to be orthogonal to this. Then, by repeating the same operation as described above, the lens performance in the tangential direction can be measured.

If the first and second rotating frames 26 and 30 are rotated in conjunction with each other, the lens performance of an arbitrary peripheral portion of the lens A to be measured can be measured. In the above embodiment, the light receiving element 24 is a line sensor, but an area sensor may be used. When an area sensor is used, it is not necessary to rotate the light receiving element 24, and the same measurement is performed by reading the area sensor line in the radial (R) direction in the vertical direction and reading the line in the tangential (T) direction in the horizontal direction. Can be. Further, if the shape of the slit 13a is a square, it is not necessary to rotate the slit.

[0027]

According to the present invention as described above,
A first optical path bending mirror, an incident angle setting mirror, an emission angle setting mirror, and a second optical path bending mirror are provided, and the first and second optical path bending mirrors are detachable. When the second optical path bending mirror is attached, the lens performance at the periphery of the lens to be measured can be measured, and when the mirror is removed, the lens performance at the center of the lens to be measured can be measured. That is, the center and the periphery of the lens to be measured can be measured only by attaching and detaching the two mirrors, so that the switching can be easily performed and the measurement can be performed in a short time.

Further, if the first and second rotating frames are provided, it is possible to measure an arbitrary peripheral portion of the lens to be inspected.
If the collimator rotating means is provided, the measurement in the radial direction and the tangential direction can be easily performed.

[Brief description of the drawings]

FIG. 1 is a plan view showing a configuration of an embodiment of a lens measuring device of the present invention.

FIG. 2 is a front view showing the configuration of an embodiment of the lens measuring device of the present invention.

FIG. 3A is a diagram showing a light amount in a slit,
(B) is a diagram showing an output of a light receiving element in a slit image.

FIG. 4 is a diagram showing a configuration of a conventional lens measuring device.

[Explanation of symbols]

 A lens under test 11 light source 13 pattern plate 13a slit 14 collimator 18 sample stage 20 imaging lens 24 light receiving element 26 first rotation frame 27 first optical path bending mirror 28 incident angle setting mirror 30 second rotation frame 31 second optical path bending mirror 32 emission angle setting mirror 35 arithmetic circuit 36 controller 37 light receiving element controller 38 mirror controller

Claims (8)

[Claims] 1. A light source, a pattern plate receiving light from the light source, a collimator having the pattern plate as a front focal position, and a sample holding a lens to be inspected so that a light beam emitted from the collimator enters. A first optical path bending mirror detachably provided between the sample table and the collimator; and a light beam reflected from the first optical path bending mirror received as a light beam intersecting the optical axis. An incident angle setting mirror for entering the inspection lens; an emission angle setting mirror for receiving light rays emitted from the lens to be inspected; and a light beam reflected on the optical axis of the lens to be inspected and reflected from the exit angle setting mirror. Detachable second that emits light in the optical axis direction
An optical path bending mirror; an imaging lens on which a reflected light beam from the second optical path bending mirror is incident; a light receiving element provided on an imaging surface of the imaging lens; A lens measuring device comprising: a light receiving element controller for moving forward and backward; an arithmetic circuit for processing an output of the light receiving element; and a control device for controlling the arithmetic circuit and the light receiving element controller. 2. The lens measuring apparatus according to claim 1, wherein said pattern plate has a slit. 3. A first rotating frame which supports the first optical path bending mirror and the incident angle setting mirror and rotates about the optical axis, a second optical path bending mirror and an emission angle. 2. The apparatus according to claim 1, further comprising a second rotating frame that supports the setting mirror and rotates about the optical axis, and a mirror controller that drives the first and second rotating frames in conjunction with each other. 3. The lens measuring device according to 1 or 2. 4. A lens measuring apparatus according to claim 1, wherein said light source has a collimator rotating means rotatable around an optical axis together with a pattern plate and a collimator. 5. The light of a light source is transmitted through a pattern plate, the transmitted light is converted into a parallel light by a collimator, and the parallel light is bent by a first optical path bending mirror placed on the optical axis to set an incident angle. The light is incident on the mirror, is incident on the imaging lens as a light flux intersecting with the optical axis by the incident angle setting mirror, and the light flux emitted from the imaging lens is reflected by the emission angle setting mirror and is reflected on the second optical path bending mirror. The light is bent in the optical axis direction by the second optical path bending mirror to be incident on the image forming lens, and the pattern image of the pattern plate is formed on the light receiving element by the image forming lens. Measuring the lens performance of the peripheral portion of the lens to be measured from the above. 6. The first and second optical path bending mirrors are removed, a light beam parallel to the optical axis is incident on the lens to be measured, and the image of the pattern plate is formed on the imaging lens by the light beam. 6. The method for measuring a lens according to claim 5, wherein the lens performance at a central portion of the inspection lens is measured. 7. The first optical path bending mirror and the incident angle setting mirror are integrally rotated about the optical axis of the lens to be tested by a first rotating frame, and the second optical path bending mirror is The output angle setting mirror is integrally rotated with the second rotation frame about the optical axis of the lens to be measured, and the performance of the lens is measured in any direction around the lens to be measured. Item 5
The measuring method of the lens described. 8. The method according to claim 5, wherein the pattern plate is rotated about the optical axis, and the lens performance of a central portion and / or a peripheral portion is measured in an arbitrary direction of the lens to be inspected. The method for measuring a lens according to any one of the above.