JPH09236509A - Method and device for measuring diopter of finder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a method and a device for measuring visibility of a finder by which the diopter finder can be measured accurately. SOLUTION: A light source 2, a slit 3 and a collimator lens 5 are arranged ahead of a finder lens 6 as a lens to be measured, and a focusing lens 8 and a light reception element 10 consisting of line sensors are arranged therebehind. Then an optical picture from the slit 3 illuminated by the light source 2 is focused on the line sensors 10, and the optical picture thereon is subjected to Fourier transformation. Using a method to measure the MTF, the line sensors 10 are moved to the light axis direction while the finder lens 6 is removed, so as to find out such a position that the MTF value of specific frequency may become the maximum. In addition, while the finder lens 6 is set thereon, the line sensors 10 are moved to the light axis direction so as to find out such a position that the MTF value of specific frequency may become the maximum, and as a result the diopter of finder is calculated on the basis of the difference between the obtained positions.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a finder diopter measurement method and apparatus, and is applicable to a finder inspection method for a camera, an inspection machine, and the like.

[0002]

2. Description of the Related Art As an inspection device for an optical finder such as a bright frame type range finder of a camera,
A telescope (MTF) measuring device manufactured by Ealing, England is commercially available. FIG. 6 shows the optical arrangement. In FIG. 6, reference numeral 34 indicates a finder lens that is a lens to be measured, and a light source 31, a slit 32, and a collimator lens 33 are arranged in this order in front of the finder lens 34 toward the finder lens 34. The finder lens 34 is, for example, a concave lens used in a bright frame type range finder.

A slit 32 illuminated by a light source 31
The image is converted into a parallel light flux by the collimator lens 33, a divergent light flux having a point P ′ as a virtual image by the finder lens 34 which is the lens to be measured, and is imaged at the point P by the imaging lens 35. The image of the point P is formed by the magnifying lens 36 and the area sensor 3
7 is formed. The output signal from the area sensor 37 is input to a microcomputer (not shown), and the light quantity distribution on the area sensor 37 is Fourier transformed to measure the optical performance (MTF) of the afocal finder lens 34.

[0004]

The above-mentioned conventional measuring method and apparatus can measure the optical performance (MTF) of the finder lens which is the lens to be measured, but cannot measure the diopter. Therefore, the diopter measurement of the finder lens is performed by visually locating a diopter measuring telescope behind the finder and passing through the telescope. In this measurement using a telescope for diopter measurement, the diopter of the finder lens is measured in diopter units, but there is a drawback in that the measurement accuracy is poor.

The conventional afocal MTF described above is also used.
According to the method and apparatus for measuring, the vertical direction (radial (R) direction) and the horizontal direction (tangential (T) direction)
To measure with, slit 32 and line sensor 37
It is necessary to rotate by 90 ° for measurement, which is troublesome.
In addition, in diopter measurement using a telescope for diopter measurement, the combined diopter in the tangential direction and the radial direction is measured.

The present invention has been made in view of the above-mentioned conventional technique, and an object of the present invention is to provide a diopter measuring method and device for a finder which can measure the diopter of a finder such as a camera with high accuracy. And

The present invention also provides a finder diopter measuring method and apparatus capable of measuring diopter in the radial direction and the tangential direction of the finder in the diopter measurement by MTF measurement without rotating the slit and the sensor. The purpose is to provide.

[0008]

In order to achieve the above object, in the method of measuring the diopter of a finder according to claim 1, a light source, a slit and a collimating lens are arranged in front of a finder lens which is a lens to be measured. Then, a light receiving element composed of an imaging lens and a line sensor is arranged behind the finder lens, the light image of the illuminated slit is formed on the line sensor, and the light image on the line sensor is Fourier-transformed. Using the method of measuring, the finder lens is removed, the line sensor is moved in the direction of the optical axis, and the position where the MTF value of a specific frequency is maximized is searched. While moving in the axial direction, a position where the MTF value of a specific frequency is maximum is searched for, and the diopter of the finder is calculated from the position difference between the two.

According to a second aspect of the present invention, in the diopter measuring method of the finder, a square slit is used, an area sensor is used as a light receiving element instead of the line sensor, and the finder lens is removed. M with a specific frequency when the finder lens is installed
A diopter may be calculated by searching for a position where the TF value is maximum in two directions orthogonal to each other and calculating the position difference of the area sensor in the two directions orthogonal to each other.

In the finder diopter measuring apparatus according to the present invention, a light source, a slit and a collimating lens are arranged in front of a finder lens which is a lens to be measured, and an image forming lens and a line sensor are arranged behind the finder lens. A light receiving element composed of a line sensor is used by arranging a light receiving element composed of a line sensor, forming an optical image of the illuminated slit on a line sensor, performing Fourier transform of the optical image on the line sensor, and measuring MTF. An automatic stage that can be mounted and moved in the direction of the optical axis, a binarization circuit that binarizes the output of the light receiving element, and a binarization signal from the binarization circuit are input, and automatically through a controller. While moving the stage in the optical axis direction, search for a position where the MTF value of a specific frequency is maximum, and if the viewfinder lens is removed or not. 'S characterized by having a calculating means for calculating a dioptric power from the position difference of the automatic stage in the case in which it is installed.

According to a fourth aspect of the present invention, in the diopter measuring apparatus of the finder, the slit is a square slit, the light receiving element is an area sensor instead of the line sensor, and the calculation means is based on an output signal from the area sensor. ,
A position where the MTF value of a specific frequency is maximum is searched for in two directions orthogonal to each other depending on whether the finder lens is removed or installed, and the position difference of the area sensor in the two directions orthogonal to each other is searched for. The diopter may be calculated.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a finder diopter measuring method and apparatus according to the present invention will be described below with reference to the drawings. In FIG. 1, a finder lens 6, which is a lens to be measured, is mounted on a sample table 13 mounted on a measuring device body 17 via a lens frame 7. The collimator support 12 is provided in front of the sample table 13 (to the left in FIG. 1) in the measuring device main body 17,
An imaging lens support 14 is attached to the rear of 3, and an automatic stage 16 is attached to the rear of the same.

On the collimator support 12, the collimator 1 is arranged on the measurement axis XX of the finder lens 6 which is the lens to be measured. In the collimator 1, a light source 2, a slit plate 3, and a collimator lens 5 are arranged in this order from a position away from the finder lens 6 toward the finder lens 6. An image forming lens 8 is arranged on the image forming lens support 14 behind the finder lens 6 via an image forming lens frame 9.

An automatic stage moving member 16 'is mounted on the automatic stage 16. A light receiving element support base 15 stands up from the upper surface of the automatic stage moving member 16 ', and a line sensor is provided on the surface of the light receiving element support base 15 facing the finder lens 6 via a light receiving element rotation plate 11. Alternatively, the light receiving element 10 including an area sensor is attached. The light receiving element 10 is rotatable by a light receiving element rotating member 11 within a range of 90 ° in a vertical plane perpendicular to the plane of FIG.
Also, since it is held via the slit rotation member 4, it can be rotated in the range of 90 ° in the vertical plane perpendicular to the paper surface of FIG. The center of each optical element is the measurement axis X
-On X. The motorized stage 16 is the controller 1
The automatic stage moving member 16 ′ is moved in the measurement axis X-X direction by a control signal from 9.

The output signal of the light receiving element 10 is a binarization circuit 1.
It is input to the microcomputer 20 via 8. The automatic stage 16 has position detecting means in the measurement axis X-X direction, which is composed of, for example, a linear encoder, and the position signal thereof is sent to the microcomputer 2 via the controller 19.
Input to 0. The microcomputer 20 Fourier transforms the binarized signal output from the light receiving element 10 according to the optical image formed on the light receiving element 10 to measure the MTF of the finder lens 6, and also the controller 19
While moving the automatic stage 16 in the optical axis direction via
A position where the MTF value at a specific frequency is maximized is searched for, and the diopter of the finder lens 6 is determined from the position difference of the automatic stage 16 when the finder lens 6 is removed and when the finder lens 6 is installed. It functions as a calculation means for calculating. A display 21 for displaying input / output data and other various data is connected to the microcomputer 20. The display 21 may be a CRT or another display.

FIG. 2 shows an example of the shape of the slit 3a of the slit plate 3 when the light receiving element 10 is a line sensor. The slit 3a has a rectangular shape with a width d.
The light receiving element 10 including a line sensor is installed such that the pixel array direction is orthogonal to the longitudinal direction of the slit 3a. FIG. 3 shows an example of the shape of the slit 3a 'of the slit plate 3 when the light receiving element 10 is an area sensor, and the slit 3a' is a square whose one side is d.

Next, the operation or measurement procedure of the above embodiment will be described. In FIG. 1, the slit 3a illuminated by the light source 2 becomes a parallel light flux by the collimator lens 5, and the virtual image P ′ is obtained by the finder lens 6 which is the lens to be measured.
And the image is formed on the light receiving element 10 by the image forming lens 8. When the light receiving element 10 is a line sensor, the flow of measurement is as shown in FIG. First, the finder lens 6 which is the lens to be measured is removed, and as shown in FIG. 2, the slit 3a of the slit plate 3 is directed in the radial (R) direction (vertical direction), and the light receiving element 10 composed of a line sensor is attached to the slit 3a. 2 and 5 while rotating the light receiving element rotating member 11 so as to be orthogonal to each other, and then moving the line sensor 10 together with the automatic stage 16 in the measurement axis direction XX.
Light receiving element 1 corresponding to the shape of the slit 3a shown in (a)
The amount of light on the light receiving element 10 is measured from the optical image as shown in FIG. The measurement signal from the light-receiving element 10 is binarized by the binarization circuit 18, and is Fourier-transformed at a specific frequency by the calculating means included in the microcomputer 20 to obtain the light-receiving element 10 at the front and rear positions in the measurement axis XX direction. M
The light receiving element 10 having the maximum MTF while comparing the TFs.
Detect the position of.

After detecting the position of the light receiving element 10 having the maximum MTF in the radial (R) direction, the position of the light receiving element 10 having the maximum MTF in the tangential (T) direction (lateral direction) is detected next. . In the tangential (T) direction, the slit 3 and the light receiving element 10 are rotated by 90 °, and the position of the light receiving element 10 is measured in the same procedure as in the radial direction.

Next, the finder lens 6, which is the lens to be measured, is mounted on the sample table 13 and the position of the light receiving element 10 is measured by the same procedure as described above. In this case as well, the position of the light receiving element 10 where the MTF is maximum is measured in the radial (R) direction and the tangential (T) direction by the same procedure as described above. Then, with respect to the radial direction, the positional difference of the light receiving element 10 between when the finder lens 6 is removed for measurement and when the finder lens 6 is installed,
Regarding the tangential direction, the position difference of the light receiving element 10 between the case where the finder lens 6 is removed and the measurement and the case where the finder lens 6 is installed are obtained, and the position difference and the focal length of the imaging lens 8 determine The diopter (diopter) is calculated from the difference between the principal point of the finder lens 6 which is a measuring lens and the virtual image position P ′, and displayed on the display 21.

Here, the value of the diopter is diopter = (fd2 / Δa-1) / 1000, where fd: focal length of the imaging lens (mm) Δa: with or without the lens to be measured. The difference in the maximum position of the specific frequency MTF value of (mm) l: The distance between the principal point positions of the lens to be measured and the imaging lens.

When the light receiving element 10 is an area sensor, it is formed into a square slit shape having a measurement width d as shown in FIG. 3, and the slit plate 3 and the light receiving element 10 are not rotated and the area in the radial (R) direction is shown. By reading the line of the sensor in the vertical direction and reading the tangential (T) direction in the horizontal direction, the same measurement result as in the case of the line sensor can be obtained.

According to the embodiment described above, the method of Fourier transforming the optical image on the light receiving element 10 composed of a line sensor and measuring the MTF is used, and the finder lens 6 as the lens to be measured is removed to receive the light. While moving the element 10 in the optical axis direction, a position where the MTF value at a specific frequency is maximized is searched for, and the finder lens 6 is installed to move the light receiving element 10 in the optical axis direction and move to a specific frequency. Since the diopter is calculated by finding the position where the MTF value of the maximum is found and the position difference between the two is used, accurate diopter measurement can be performed without using a telescope for diopter measurement as in the past. You can

Further, using a device for Fourier transforming the optical image on the line sensor and measuring the MTF, the automatic stage 16 on which the light receiving element 10 composed of the line sensor can be mounted and moved in the optical axis direction, and the light receiving element. A binarization circuit 18 that binarizes the output of 10 and a binarization signal from the binarization circuit 18 are input, and while the automatic stage 16 is moved in the optical axis direction via the controller 19, The position where the MTF value of the frequency is maximized is searched for, and the diopter is calculated from the position difference of the automatic stage 16 when the finder lens 6 as the measured lens is removed and when the finder lens 6 is installed. Since the calculation means is provided for automatically measuring the diopter of the finder lens 6,
It can be done accurately.

Further, using a square slit 3a ',
An area sensor is used as a light receiving element, and a position where the MTF value of a specific frequency is maximum is searched in two directions orthogonal to each other depending on whether the finder lens 6 is removed or the finder lens 6 is installed, To do 2
Since the diopter is calculated from the positional difference of the area sensor across the directions, when the diopter is measured in the vertical direction and the horizontal direction of the finder lens 6 that is the lens to be measured, the slit plate 3 and the light receiving element 10 are Since measurement can be performed without rotating, it is possible to perform accurate diopter measurement in a short time without alignment and adjustment of the slit plate 3 or the light receiving element 10.

[0025]

According to the first aspect of the invention, the slit light image is searched for the position of the maximum value of the MTF value of the specific frequency of the finder lens and the imaging lens forming the afocal lens, and the imaging lens is formed. Also finds the position of the maximum value of the MTF value of the same frequency, calculates the position difference between the two, calculates the position difference of the maximum value of the MTF value of the specific frequency depending on the presence or absence of the finder lens that is the lens to be measured, and the focus of the imaging lens. It is possible to measure the diopter with high accuracy based on the distance.

According to the third aspect of the invention, there is provided a motorized stage on which a light receiving element composed of a line sensor can be mounted and moved in the optical axis direction, and a binarizing circuit for binarizing the output of the light receiving element. A binarization signal from the binarization circuit is input, and a position where the MTF value of a specific frequency is maximized is searched for while moving the motorized stage through the controller in the optical axis direction, and the finder, which is the lens to be measured, is searched for. Since the calculation means for calculating the diopter from the position difference of the automatic stage when the lens is removed and when the finder lens is installed, the diopter measurement of the finder lens is automatically performed, and It can be done accurately.

According to the second and fourth aspects of the present invention, a square slit is used, an area sensor is used as a light receiving element, and it is specified whether the finder lens is removed or not. Frequency MT
The position where the F value is maximum is searched in two directions orthogonal to each other, and the diopter is calculated from the position difference of the area sensor in the two directions orthogonal to each other. When measuring the diopter with the direction, it can be measured without rotating the slit plate and the light receiving element. A measurement can be made.

[Brief description of drawings]

FIG. 1 is an optical layout diagram and a block diagram of a control arithmetic system showing an embodiment of a finder diopter measurement method and apparatus according to the present invention.

FIG. 2 is a front view showing an example of a slit plate used in the embodiment.

FIG. 3 is a front view showing another example of the slit plate used in the embodiment.

FIG. 4 is a flowchart showing a measuring operation according to the embodiment.

FIG. 5 is a waveform diagram showing an example of a slit shape and an optical image on the light receiving element thereof according to the embodiment.

FIG. 6 is an optical layout diagram showing an example of a conventional MTF measuring device.

[Explanation of symbols]

 2 light source 3 slit 5 collimator lens 6 finder lens which is a lens to be measured 8 imaging lens 10 light receiving element 16 automatic stage 18 binarization circuit 19 controller 20 microcomputer including arithmetic means

Claims (4)

[Claims] 1. A light source, a slit, and a collimator lens are arranged in front of a finder lens which is a lens to be measured,
A light receiving element composed of an imaging lens and a line sensor is arranged behind the finder lens, the light image of the illuminated slit is formed on the line sensor, and the light image on the line sensor is Fourier-transformed to obtain the MTF. Using the measuring method, the finder lens is removed, the line sensor is moved in the optical axis direction, and the position where the MTF value at a specific frequency is maximized is searched. A diopter measuring method for a finder, characterized in that while moving in the optical axis direction, a position where the MTF value of a specific frequency is maximized is searched for, and the diopter is calculated from the positional difference between the two. 2. A square slit is used, an area sensor is used as a light receiving element instead of a line sensor, and an MTF value of a specific frequency is obtained when the finder lens is removed and when the finder lens is installed. 2. The diopter measurement method for a finder according to claim 1, wherein the maximum position is searched for in two directions orthogonal to each other, and the diopter is calculated from the positional difference between the area sensors in the two directions orthogonal to each other. 3. A light source, a slit, and a collimator lens are arranged in front of a finder lens which is a lens to be measured,
A light receiving element composed of an imaging lens and a line sensor is arranged behind the finder lens, the light image of the illuminated slit is formed on the line sensor, and the light image on the line sensor is Fourier-transformed to obtain the MTF. A diopter measuring device for a finder using a measuring device, which comprises a motorized stage on which a light receiving element composed of a line sensor can be mounted and which can be moved in the optical axis direction, and a binary value which binarizes the output of the light receiving element. The digitization circuit and the binarization signal from the binarization circuit are input, and while the motorized stage is moved in the optical axis direction via the controller, a position where the MTF value of a specific frequency becomes maximum is searched for, And a calculation means for calculating the diopter from the position difference of the automatic stage when the finder lens is removed and when the finder lens is installed. Diopter measurement device of the finder according to claim. 4. The slit is a square slit, the light receiving element is an area sensor which replaces the line sensor, and the arithmetic means is based on an output signal from the area sensor.
A position where the MTF value of a specific frequency is maximum is searched for in two directions orthogonal to each other depending on whether the finder lens is removed or installed, and the position difference of the area sensor in the two directions orthogonal to each other is searched for. The diopter measuring apparatus for a finder according to claim 2, wherein the diopter is calculated.