JPH1068675A - Apparatus and method for measuring lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lens measuring apparatus and method capable of obviating indeterminate elements caused by measurers or the like and measuring the visibility or magnification with high accuracy. SOLUTION: The light of a light source 11 is transmitted through a knife edge 33 and the transmitted light flux is collimated by a collimater 14 to impinge an image forming lens 20 so that the image of the knife edge is imaged on a light receiving element 24 by the image forming lens. The output of the light receiving element 24 is differentiated by a differentiating circuit 30 to provide a position having the maximum differentiating value as an imaging position. The imaging position is obtained in the presence and absence of an inspected lens to calculate the visibility of the inspected lens from a difference between both imaging positions.

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 diopter and magnification of a lens, and more particularly to a technique applicable to the measurement of diopter of a camera finder, binoculars, a telescope or the like.

[0002]

2. Description of the Related Art As a device for measuring a lens system such as a viewfinder of a camera, there is known a telescope measuring device of Ealing Company, UK shown in FIG. This measures the MTF of the lens to be measured.

In FIG. 11, light emitted from a light source 1 passes through a slit 2, is converted into a parallel light beam by a collimating 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.

However, in the above device, the optical performance (MT
F) can be measured, but diopter cannot be measured. On the other hand, a conventional method of measuring diopter generally uses a diopter telescope. First, the objective lens of the diopter telescope is moved in the optical axis direction to focus on infinity. Next, the test lens is set in front of the diopter telescope, and the objective lens is moved again to focus on infinity. Then, the diopter of the test lens was calculated from the extension amount of the objective lens in both measurements.

[0005]

However, in the above-mentioned method, since the measurer adjusts the focus visually, the influence of the measurement error by the measurer is large, and the measurement accuracy cannot be improved. Therefore, the measured diopter was also coarse in diopter units.

The present invention has been conceived in view of the above facts, and it is an object of the present invention to provide a lens measuring apparatus and a measuring method capable of eliminating uncertain factors such as a measurer and measuring diopter or magnification with high accuracy. And

[0007]

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 that holds the test lens so that the light beam emitted from the collimator is incident, an imaging lens on which the light beam emitted from the test lens is incident, and a sample lens that is placed near the imaging point of the imaging lens; A light-receiving element movable back and forth in the optical axis direction of the imaging lens, a controller for moving the light-receiving element back and forth in the optical axis direction, a differentiation circuit for differentiating the output of the light-receiving element, and control for controlling the differentiation circuit and the controller And a device.

The pattern plate is a slit or a knife edge, the knife edge is inclined by 45 ° with respect to the tangential direction and the radial direction, or the test lens is a finder lens, The plate may be a frame of the finder lens, or the arithmetic circuit may be a differential circuit for differentiating the output of the light receiving element.

The lens measuring method of the present invention includes:
The light from the light source is transmitted through the pattern plate, and the transmitted light beam is converted into a parallel light beam by a collimator. A step of arranging a test lens in the parallel light beam to obtain a position where the imaging lens forms the pattern image, and calculating a diopter of the test lens from a difference between the two imaging positions. And a process.

A light receiving element is placed at the image forming position, and the light receiving element is moved forward and backward in the direction of the optical axis of the image forming lens to obtain an image forming position from the output of the light receiving element. It is preferable that the position where the peak value of the differential value becomes the maximum is set as the image forming position, or that the output of the light receiving element is measured in the vertical and horizontal directions with the light receiving element using a knife edge inclined at 45 ° to the pattern plate. .

Further, the distance between two separated points of the pattern image on the imaging plane may be determined by the light receiving element, and the magnification of the lens to be inspected may be determined from the distance between the corresponding two points on the pattern plate.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing the configuration of one embodiment of the measuring device of the present invention. The light source 11 is supported by the cylinder 12,
The cylindrical body 12 includes a pattern plate 13 and a collimator 14.
And are integrated. As shown in FIG. 3, a slit 13 a having a width d is formed in the pattern plate 13, and the slit 13 a overlaps a front focal point of the collimator 14.
The slit 13a may be elongated as shown in FIG. 3A or may be square as shown in FIG. When the slit 13a is elongated, the pattern plate 13 is connected to a rotating means 15 so as to be rotatable around the optical axis a. The cylindrical body 12 is fixed to a light source support 16, and the light source support 16 is fixed to a 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 erected from above, and the lens O to be tested is detachable therefrom. An imaging lens support 19 is provided on the right side of the sample stage 18, and an imaging lens 20 is attached to the tip of the imaging lens support 19.

An automatic stage 21 is mounted on the right side of the imaging lens support base 19 so as to be able to advance and retreat in the direction of the optical axis a. A light receiving element support base 22 is provided on the automatic stage 21. A rotary stage 23 is provided on the surface facing the imaging lens, and the light receiving element 2 is provided on the rotary stage 23.
4 is fixed. A line sensor is used for the light receiving element 24, and the rotary stage 23 is rotatable around the optical axis a.

The output of the light receiving element 24 is input to a microcomputer as a control device 26 via an arithmetic circuit 25 comprising a binarizing circuit. The automatic stage 21 advances and retreats on the optical axis automatically by the controller 27, and the controller 27 is driven by the control device 26 according to a predetermined program. Also, the light receiving element 2
The output state of 4, and the measurement result can be monitored by the CRT 28.

In FIG. 1, a pattern plate 13 illuminated by a light source 11 becomes a parallel light beam by a collimator 14,
A virtual image P ′ is formed by the test lens O, and an image is formed at the point P on the light receiving element 24 by the imaging lens 20.

FIG. 2 is a flowchart of the measurement. First, the lens O to be inspected is removed (step 1).
01). The rotating means 15 and the rotating stage 2 are arranged such that the line sensor as the light receiving element 24 and the slit image are orthogonal to each other.
3 is adjusted (step 103). For example, the slit 13a is set in the radial (R) direction, and the line sensor of the light receiving element 24 is set in the direction orthogonal to this. Then, the output of the light receiving element 24 is measured while moving the light receiving element 24 in the direction of the optical axis a (step 105).

FIG. 4 (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.

This is binarized by a binarization circuit as an arithmetic circuit 25, and input to a control device 26.
Is calculated (step 107). The control device 26 drives the controller 27 to move the light receiving element 24 in the optical axis direction, and obtains the position where the above MTF is maximum (step 1).
09), the position of the light receiving element 24 on the optical axis at that time is measured (step 111).

Next, the slit 13a is rotated by 90 ° to the tangential (T) direction, and the light receiving element 24 is also rotated by 90 ° so as to be perpendicular to the tangential (T) direction. And step 105
To step 111 are repeated. Next, a finder lens as the test lens O is attached (Step 10).
1) Repeat steps up to step 111. When the measurement of the presence or absence of the test lens O is completed, the control device 26 calculates the diopter according to the following equation (step 113).

Diopter (diopter) = (f d^Two/ Δa−L) where, fd: focal length of the imaging lens 20 (mm) Δa: maximum value of the specific frequency MTF value depending on the presence or absence of the lens to be inspected
Large position difference (mm) L: distance (m) between the principal point of the test lens and the imaging lens
m). Finally, the measurement result is displayed on the CRT 28, and the processing ends.
You.

In the above embodiment, the light receiving element 24 is a line sensor. However, 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 slit 13a is formed in a square as shown in FIG. 3B, the rotating means 15 becomes unnecessary.

In the above embodiment, the slit 13a is used as the pattern plate. However, the slit width d is 100 μm or less to search at the position of the maximum value of the optical performance (MTF) in the direction of the optical axis. The diopter is difficult to measure with a lens, and is not suitable for measuring a test lens having poor optical performance such as a finder of a camera or the like.

The slit (object) T. R (vertical,
When measuring the diopter in the (lateral) direction, it is necessary to measure by rotating the slit 13a and the light receiving element 24 by 0 ° and 90 °, so that an image displacement occurs due to the rotation, and adjustment is required at the time of measurement, and the measurement is required. It takes time.

The embodiment shown in FIG. 5 solves such a problem. The diopter can be measured with high accuracy even with a dark lens such as a camera finder, and the light receiving element and the pattern plate are rotated. FIG. 3 is a diagram showing an embodiment that does not need to be performed.

In FIG. 5, a lens O to be inspected is a finder lens, which has a frame 41 in which a frame or a mark is drawn in the field of view, and is attached to the sample table 18.
The collimator 14 and the light source 11 are provided in front of the test lens O, and a diffusion plate 32 and a knife edge 33 as a pattern plate are supported between them.

As shown in FIG. 6, the knife edge 33 is configured such that a semicircle is shielded and a semicircle is transmitted. Edge 3
3a is installed at an angle of 45 ° with respect to either the tangential (T) or the radial (R), and is attachable / detachable. In this example, the rotating means 15 is not used.

Further, in this embodiment, the output of the light receiving element 24 is input to the control device 26 via the differentiating circuit 30 as the arithmetic circuit 25. In FIG. 5, a light beam transmitted through the light source 11, the diffusion plate 32, and the knife edge 33 becomes a parallel light beam and is incident on a finder lens as the lens O to be measured.

The light beam incident on the distance measuring section 42 of the lens O to be inspected passes through the semi-transparent mirror 43 and the lens 44 inside the finder lens, further passes through the imaging lens 20 and forms an image at point P on the light receiving element 24. I do. The output of each element of the light receiving element 24 is shown in FIG.
7 (a), there is obtained a diagram having an output difference of H between light and dark as shown in FIG. 7 (a). When this output is differentiated by the differentiating circuit 30, FIG.
As shown in (b), the local maximum Ho appears at a position corresponding to the edge 33a.

The controller 27 moves the light receiving element 24 in the direction of the optical axis in accordance with a program pre-installed in the control device 26, finds a position where the maximum value Ho is maximized, and uses that position as an image forming point. Read the coordinates on the optical axis of. The reading direction of the light receiving element 24 is set vertically and horizontally, and a position at which the maximum value is maximized is similarly obtained.

Next, the lens O to be inspected is removed, an image of the knife edge 33 is formed in the same manner as described above, and a position where the maximum value is maximized is obtained. Then, from these measurement results, the control device 26 calculates the diopter of the test lens O and displays the diopter on the CRT. As described above, in this embodiment, the knife edge is used instead of the slit, so that the pattern image becomes bright and the diopter can be easily measured even with a dark lens.

In FIG. 5, the knife edge 33 is removed, the parallel light beam from the collimator 14 is made incident on the frame 41, and the lens 45, the mirror 46, the half mirror 43,
The pattern image of the frame 41 is formed at the point P on the light receiving element 24 by the imaging lens 20 via the lens 44. In this case, the frame 41 becomes a pattern plate.

As shown in FIG. 8, the frame 41 has an opaque frame 41b formed on a transparent plate 41a.
The image of this frame becomes a pattern image and becomes a light receiving element 24.
It will image on top. Any frame 41b
, The output of the light receiving element 24 is obtained in the same manner as described above, the differential shape is calculated by the differentiating circuit 30, and the position where the differential value becomes maximum is obtained. Next, the diopter of the frame 41 can be obtained by removing the test lens O and similarly obtaining the position where the differential value becomes maximum.

FIG. 9 shows a further development of the above measuring method.
It is an example applied to measurement of magnification. In this example,
The pattern image of the opaque frame 41b of the frame 41 is applied to the light receiving elements 24 at 141b and 141b '.
Is to measure the output.

As the light receiving element 24, a pattern image 141
When the output of each element is measured in the left and right direction in FIG. 9 using an area sensor or a line sensor having a length exceeding both ends of b, 141b ′, as shown in FIG.
A diagram having a valley portion whose output is reduced by H or H 'corresponding to the pattern images 141b and 141b' is obtained.

When this output is differentiated by the differentiating circuit 30, H ₁ corresponding to the valley of H in FIG. 10A is obtained as shown in FIG.
And the peak of H ₂ are obtained, and the valley of H ₁ ′ and the peak of H ₂ ′ corresponding to the valley of H ′ are obtained. Then, the difference between the barycentric positions of the differential light amount values is calculated to determine the dimension of L, and by measuring the corresponding portion in the frame 41, the magnification of the finder lens can be measured.

In the conventional method, the magnification of a lens to be inspected such as a finder lens cannot be measured. However, according to the embodiment of the present invention, this can be achieved. In the above embodiment,
Although the pattern images 141b and 141b 'are independent images, the same measurement can be performed by measuring two separated points on one pattern image.

[0038]

According to the present invention as described above,
The light image of the pattern plate illuminated by the light source is measured by a line sensor through a test lens and an imaging lens, differentiated by a differentiating circuit, and a sensor position at which the maximum differential value in the optical axis direction is obtained is determined. Since the difference in the movement of the light receiving element between the presence and absence (attachment / removal) of the test lens can be calculated, the diopter of the test lens can be measured with high accuracy. In addition, since all measurements are performed automatically, there is no influence of errors by the operator.

When a knife edge is used for the pattern plate, the pattern image becomes brighter than the slit, and measurement of a dark test lens can be easily performed. Remove the knife edge by the above method, illuminate the entire frame of the finder to be measured, measure the frame image in the finder with a line sensor, differentiate with a differentiating circuit, and the sensor position difference that maximizes the differential value with or without the finder lens The diopter of the frame in the finder can be measured.

The differential value of the frame image on the line sensor can be measured, and the position of the center of gravity of the image differential value on the line sensor can be calculated.
The size of the frame that has passed through the optical system can be calculated by calculating the difference in the center of gravity, and the magnification of the frame image can be measured by comparing the size with the actual size.

If the knife edge is set at an angle of 45 ° with respect to the line sensor or the area sensor of the light receiving element, it is not necessary to rotate the area sensor or the line sensor, and the measurement can be easily performed.

If the distance between two separated points of the pattern image on the imaging plane is determined by the light receiving element and the distance between the corresponding two points on the pattern plate is determined, the magnification of the lens to be inspected can be measured. Becomes

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of a lens measuring device of the present invention.

FIG. 2 is a flowchart illustrating a method for measuring a lens according to the present invention.

FIGS. 3A and 3B are diagrams showing the pattern plate of FIG. 1;

FIG. 4A 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. 5 is a configuration diagram showing another embodiment of the lens measuring device of the present invention.

FIG. 6 is a diagram showing a configuration of a knife edge.

7A is a diagram illustrating an output of a light receiving element with respect to an image of a knife edge, and FIG. 7B is a diagram illustrating a differential value of FIG.

FIG. 8 is a diagram showing details of a frame as a pattern plate.

FIG. 9 is a diagram showing a state where two pattern images are formed on a light receiving element.

10A is an output diagram in which the output of the light receiving element of FIG. 9 is taken in the left-right direction of the figure, and FIG. 10B is a diagram showing a differential value of FIG.

FIG. 11 is a diagram showing a configuration of a conventional lens measuring device.

[Explanation of symbols]

 O lens to be inspected 11 light source 13 pattern plate 13a slit 14 collimator 18 sample table 20 imaging lens 24 light receiving element 25 arithmetic circuit 26 controller 27 controller 30 differentiator circuit 33 knife edge 41 frame

Claims (11)

[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 stage holding a lens to be inspected so that a light beam emitted from the collimator enters. An imaging lens on which a light beam emitted from the lens to be detected is incident; a light receiving element placed near an imaging point of the imaging lens and capable of moving back and forth in the optical axis direction of the imaging lens; An apparatus for measuring a lens, comprising: a controller for moving back and forth in the axial direction; an arithmetic circuit for processing an output of the light receiving element; and a control device for controlling the arithmetic circuit and the controller. 2. The diopter measuring apparatus for a lens according to claim 1, wherein said pattern plate has a slit. 3. The apparatus according to claim 1, wherein said pattern plate has a knife edge. 4. The lens measuring device according to claim 3, wherein said knife edge is inclined by 45 ° with respect to a tangential direction and a radial direction. 5. The test lens is a finder lens,
2. The lens measuring device according to claim 1, wherein the pattern plate is a frame of the finder lens. 6. The lens measuring device according to claim 1, wherein the arithmetic circuit is a differentiating circuit for differentiating an output of the light receiving element. 7. The light of a light source is transmitted to a pattern plate, the transmitted light beam is converted into a parallel light beam by a collimator, and the parallel light beam is incident on an image forming lens to form a pattern image of the pattern plate by the image forming lens. A step of obtaining an imaged position; a step of arranging a test lens in the parallel light beam to obtain a position at which the imaging lens forms the pattern image; and a step of determining the position of the test lens from the difference between the two image formation positions. Calculating a diopter. 8. The image forming apparatus according to claim 7, wherein a light receiving element is placed at the image forming position, and the light receiving element is moved forward and backward in the optical axis direction of the image forming lens to obtain an image forming position from an output of the light receiving element. How to measure the lens. 9. The lens measuring method according to claim 8, wherein the output of the light receiving element is differentiated, and a position at which the peak value of the differential value is maximum is defined as an imaging position. 10. The method according to claim 7, wherein
Using a knife edge inclined at 45 ° to the pattern board,
A method for measuring a lens, comprising: measuring the output of the light receiving element in the vertical and horizontal directions with the light receiving element. 11. The method according to claim 1, wherein a distance between two spaced points of the pattern image on the image forming surface is determined by the light receiving element, and a magnification of the lens to be inspected is determined from a distance between the corresponding two points on the pattern plate. The method for measuring a lens according to claim 7.