JPH0224528A - Lens tester - Google Patents

Abstract

PURPOSE:To evaluate the image forming property of an optical system such as photograph lenses accurately by quantitatively measuring the contrast of a chart images. CONSTITUTION:An optical system 2 inputs light which is transmitted through a chart CA having a specified lattice pitch into a lens under test 1 which is held on a lens mounting part 10. Light which is transmitted through a chart CZ at a specified lattice pitch is also inputted. In a contrast measuring part 3, the images of the charts CA and CZ which are formed by the passing through the lens under test 1 are formed in a CCD sensor part 31. The contrast between the chart images is computed in an operating circuit 32. In a judging part 5, the contrast value of the chart images which is obtained in the contrast measuring part 3 is compared with a reference value. The contrast measuring part 3 is controlled with an operation control part 4. When the contrast value exceeds the judging reference, the lens under test 1 is judged as defective. A display part 6 displays the result of the judgment of the judging part 5 by the lighting of LEDs.

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an inspection device used for determining defective optical lenses, and more specifically, it measures the contrast of a chart image formed by the lens and measures the contrast based on this measured value. The present invention relates to a lens tester that determines the quality of lenses. [Prior Art] Generally, optical lenses such as photographic lenses are subjected to a final inspection (performance inspection) during mass production by a projection test.The projection test is a chart projected by the lens to be inspected. The image is visually checked by the worker.
2 to confirm the resolving power of the lens to be tested. Figure 31 shows an outline of the projection test, where 1' is a lamp such as a halogen lamp as a light source, 2' is a condenser lens that condenses the light from lamp 1', 3' is a transmission chart, and 4' is the subject. The detection lens 5' is a projection plate. The transmission type chart 3' is made by drawing a plurality of predetermined patterns on the surface of a transparent glass plate, each of which is a combination of vertical and horizontal line arrays of varying pitches, by vapor deposition of chromium or the like to prevent light from transmitting. The size (line width and pitch) of the line array in this pattern corresponds to the resolution, and for example, 100 lines/layer can be separated from the line array with the minimum pitch that can be seen separately in the chart image projected onto the projection plate 5'. The light rays from the fist lamp 1', whose resolution is to be evaluated, are condensed by a condenser lens 2', illuminate the transmission type chart 3' from the back, and pass through. The image of the transmission chart 3' formed by this transmitted light is enlarged and projected by the test lens 4' onto the projection plate 5' placed at a position 40 to 50 times the focal length of the test lens 4'. do. At this time, if the incident angle θ2 of the illumination light from the condenser lens 2' onto the chart 3' is smaller than the incident angle θ1 of the light flux of the chart image by the test lens 4', as shown in the figure, the test lens 4' The incident angle θ2 must be sufficiently large to obtain a narrowed-down result. The operator finely adjusts the position of the lens 4' to be tested in the optical axis direction to focus the center of the chart image on the projection plate 5', and then the chart image projected onto the projection plate 5'. Visually check whether the chart is separated at a predetermined pitch at a predetermined position within the chart image (in other words, whether the chart image has a predetermined resolution at a predetermined position within the chart image), and determine the quality of the lens to be tested. It is something to be inspected. [Problem to be Solved by the Invention] However, in such a projection test, the light from a light source with finite brightness is enlarged and projected, and the enlarged image projected onto the projection plate is dark. Everything has to be done in a darkroom. For this reason, the complicated and time-consuming measurement work must be carried out in a darkroom, resulting in extremely poor workability, requiring a lot of time for measurement, and creating a poor working environment for the workers. Furthermore, depending on the focal length of the lens to be tested, the distance from the lens to be tested to the projection plate may be several meters, and in such cases, multiple workers such as a focus adjustment person and a checker are required. It is something. In addition, since the distance between the test lens and the projection plate is 40 to 50 times the focal length of the test lens, if the test lens has a long focal length, a correspondingly large darkroom is required, and a large amount of equipment is required. The problem is that it costs money. Furthermore, since the incident angle θ2 of the illumination onto the chart must be larger than the incident angle θ3 of the light flux of the chart image through the test lens, if the test lens is bright (with a large F value), a condenser lens should be used. It had to be large in diameter and bright, which was extremely difficult. In addition, although skill is required to perform inspection efficiently and with less variation, since the chart image is checked visually, separation and separation of the chart image is necessary.
Non-separation also depends on the physical condition and psychological state of the worker.
There is a problem in that no matter how skilled the operator is, stable inspection with a certain level of accuracy or higher cannot be expected. [Purpose of the Invention] The present invention was made in view of the above background, and it is possible to inspect optical lenses by automatic quantitative measurement, and is small and lightweight, has good workability, and is easy to work with. To provide an efficient lens tester. is its purpose. [Means for Solving the Problems] Therefore, a lens tester according to the present invention is as follows. "Configuration" A lens holder that rotatably holds the lens to be tested;
an optical system that makes light transmitted through a chart of a predetermined lattice pitch enter the test lens held by the lens holder from on-axis and off-axis; a contrast measuring means that calculates contrast based on a chart image detected by a length measuring means arranged movably in the optical axis direction of the test lens;
an operation control means for measuring the contrast at a predetermined position of the image of the test lens by controlling the rotational drive of the lens holder and the operation of the contrast measuring means; It is composed of a determining section that determines the quality of the lens to be tested by comparing the contrast measured by the contrast measuring means with a predetermined criterion, and a display section that displays the determination result by the determining section. be. "Operation" The contrast measurement means detects the light intensity of the on-axis and off-axis chart images formed by the test lens held in the lens holder, and calculates the time series of the pitch direction of the chart. It is converted into an electrical signal, and from this electrical signal, the contrast of the chart image of the predetermined grator pitch on-axis and off-axis is calculated (ie, measured). Here, measuring the contrast of the chart image formed by the lens under test means measuring the MTF value of the lens under test at the spatial frequency of the chart pitch, since the chart is a lattice chart with a predetermined pitch. It is something that In other words, what is MTF? (Overview of MTF) When light (image light) passes through an optical system such as a camera lens,
The contrast of the output light (output image) of the optical system is worse than the contrast of the input light (input image). The amount of change in contrast is closely related to the spatial frequency of the image, and the ratio of contrast between the input image and output image is determined by the modulation transfer function (
ModulationTrans4er Function
on, abbreviated as MTF). MTF is defined as, at a certain spatial frequency,
It can be thought of as a contrast deterioration function, and is used to indicate the imaging characteristics of an optical system. When measured using a sine wave grating, the contrast m is defined as follows, where the maximum light amount of the optical image is Iaax+the minimum light amount is Isin. The maximum light intensity I jdX and the minimum light intensity □ of the chart transmitted light that changes sinusoidally and is input to the lens to be tested. Therefore, the contrast of the input image to the test lens can be determined using the above equation (2), but the minimum amount of input light l5in is O(
Therefore, the definition formula of MTF is (1
), the contrast of the input image is l. Therefore, if the contrast of the sine wave chart image (output image) formed by the test lens is measured, this will be the MTF value of the test lens at the spatial frequency of the chart pitch. The MTF is a function unique to the optical system, and when expressed on orthogonal coordinates with the contrast deterioration rate on the vertical axis and the spatial frequency on the horizontal axis, it can be expressed, for example, as shown in FIG. 32. In an optical system such as a camera lens, the MTF is calculated (or measured after manufacturing) at the time of the optical stage 1 and is known due to the curvature or inclination of the imaging surface. It is also possible to analyze the causal relationship between the occurrence of such problems and the cause of a malfunction in the optical system. Therefore, a single spatial frequency (n lenses/am
), it is possible to predict the MTF of the lens to be tested. That is, for example, when the solid line shown in FIG. 33 is the ideal (design) MTF curve and the contrast at the spatial frequency n tree/sum is a, the contrast of the chart image of the same spatial frequency formed by the test lens is is X, the MT of the lens to be tested
It can be inferred that F is like an imaginary line. In addition, by examining the position in the optical axis direction (i.e., the imaging position n) that exhibits the maximum contrast value at multiple locations on-axis and off-axis, the imaging plane as shown in FIG. 30(a) can be determined. Fall down,
It is possible to detect the curvature of the imaging plane as shown in FIG. Therefore, if the judgment reference value and the judgment reference amount are appropriately set based on the allowable value of the contrast of the test lens at a predetermined spatial frequency and the allowable amount of the curvature and inclination of the image plane 2, etc., the measurement of the test lens can be performed. By comparing the results with these determination reference values or determination reference amounts, it is possible to determine the quality of the lens to be tested. Furthermore, it is possible to analyze the causes of defects in the optical system, such as the eccentric five-plane shape of the constituent lenses and interval errors, from the occurrence of curvature, inclination 9, etc. of the imaging plane. In addition, when using a square wave chart instead of a sine wave chart,
The measurement chamber 11Jf frequency includes harmonics and multiple spatial frequencies coexist, but the M of the lens to be tested during mass production etc.
When the TF is known, it is sufficient to set the determination criteria by considering the harmonic liquid component, and conversely, it has the effect that the image plane position can be detected while including the harmonics. The operation control means moves the detection means in the optical axis direction of the test lens, measures the contrast of the chart image at a plurality of locations on the axis and off-axis in the optical axis direction of the test lens, and also moves the detection means in the optical axis direction of the test lens. By driving the lens to be tested, the lens to be tested is rotated around its tip axis, and off-axis measurement points are changed to measure the contrast of the chart image at multiple points in the optical axis direction of the lens to be tested. *The detection means is fixed at the average position on the optical axis where the contrast at each measurement point is the maximum value based on the on-axis contrast measurement results obtained from the above measurements. The detection means of the contrast measuring means is driven to move so that the lens to be tested is rotated around its optical axis by driving the lens holder, and the contrast of the chart image at each off-axis measurement point is measured. Measures the contrast of the image and the chart image, and controls the drive of the lens holder (rotation of the lens to be tested). The determination section is controlled by the operation control means and compares the measured value (contrast value of the chart image) obtained by the contrast measurement means with a predetermined determination reference value, and also compares the measurement value (contrast value of the chart image) with a predetermined determination reference value, and compares the value on the axis showing the maximum contrast. The amount of mutual deviation in the optical axis direction of each off-axis measurement point is compared with a predetermined judgment standard amount, and if any of the compared measured values exceeds the judgment standard, it is judged as defective and the tested lens is accepted. If the lens to be tested is defective, check the contrast of each measurement point above or the state of mutual deviation in the optical axis direction of the on-axis and off-axis measurement points showing the maximum contrast. The details of the defect are derived using a predetermined analytical calculation method. The display section displays the determination result by the determination section and the derived defect content. It is something. Embodiment J of the Invention Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. "Overview of Lens Tester LT" First, let's talk about the J! of Lens Tester LT according to the present invention. abbreviation, 1st
This will be explained using the block diagram shown in the figure. (Configuration) The lens tester LT includes a lens mount section 10 as a lens holding section, an optical system 2, a contrast measurement section 3 as a contrast measurement means, which is composed of a sensor section 31 and an arithmetic circuit 32, and an operation control section. It is composed of a control section 4, a determination section 5, and a display section 6. Incidentally, the control section 4 and the determination section 5 are constituted by one microcomputer. In the second embodiment, the lens tester LT is connected to a computer as shown in FIG. 26 to constitute a lens tester system, which will be explained in detail later. (Function) The lens mount part 0 holds the test lens 1 in a predetermined position so as to be rotatable about the optical axis of the test lens 1. The optical system 2 transmits light (on-axis light LA) that has passed through a char (A) CA with a predetermined lattice pitch from an axis along the optical axis of the test lens L to a test lens L held in a lens mount unit 10. At the same time, the light (on-axis light L
Z) is incident. In the contrast measurement section 3, a chart C is formed by the on-axis and off-axis light LA@LZ from the optical system 2 passing through the test lens 1 held by the lens mount section 10.
Each CCD sensor (Iil I upper sensor 31A and off-axis sensor 31Z) of the CCD sensor unit 31 scans the A-CZ image in the pitch direction of the chart image, converts the brightness of the chart image into an electrical signal, and converts the brightness of the chart image into an electrical signal. The signals are computed by the arithmetic circuit 32 (on-axis arithmetic circuit 32A and off-axis arithmetic circuit 32B) to calculate and measure the contrast of the chart images on-axis and off-axis. The control unit 4 controls each CCD sensor 31 of the CCD sensor unit 31.
A.31Z is moved in the optical axis direction of the test lens 1 to measure the contrast of the on-axis and off-axis chart images at multiple locations along the optical axis direction of the test lens l, and the lens mount section By driving 10, the test lens l is rotated around its tip axis to change the off-axis measurement point, and the pitch direction of the chart image relative to the test lens l on the axis is changed. The contrast of the chart image is measured at multiple predetermined off-axis positions at multiple locations in the optical axis direction of the detection lens 1, and each measurement point is determined from the on-axis contrast measurement results obtained by measurement Optical axis where the contrast at each measurement point on the axis is the maximum value] The on-axis and off-axis CCD sensors 31A and 31Z are fixed at this average position, that is, the contrast at each measurement point on the axis is at the maximum value. The average distance between the test lens 1 and the on-axis sensor 31A,
The off-axis sensor 312 is also fixed at a distance from the test lens l that is equal to ), and the contrast measurement unit 3 is configured to measure the contrast of the chart image at each off-axis measurement point by rotating the test lens 1. Each CCD sensor 31A of the sensor section 31
-31Z movement drive, contrast measurement, and drive of the lens mount section 10 (rotation of the lens 1 to be tested). The determination unit 5 is controlled by the operation control unit 4 and performs the load measurement i! Comparing the contrast value of the chart image obtained in step 13 with a predetermined criterion value,
The amount of deviation in the optical axis direction of each on-axis and off-axis measurement point that shows the maximum contrast value is compared with a predetermined judgment standard amount, and if any exceeds the judgment standard, it will be inspected as defective. Determine the quality of lens l. Furthermore, if the lens to be tested is defective, a predetermined value can be determined based on the contrast value of each measurement point or the mutual deviation in the optical axis direction of the on-axis and off-axis measurement points that indicate the maximum contrast value. The details of the defect are derived using the analytical calculation method. The display unit 6 displays the determination result by the determination unit 5 and the derived defect details by lighting the LEDs arranged thereon. Next, the configuration and operation of each of the uI components described above will be explained in detail in order. [Lens mount section 10J (configuration) FIG. 2 is a plan view of the lens mount section 10, and FIG. 3 is a plan view of the lens mount section 10.
It is the m-tn sectional view. In the figure, 100 is the chassis of the Lens Tester LT (:
52 (not shown in Figure 52), 11 is a mount for positioning and holding the lens 1 to be tested, 101 is a bearing post fixed to the chassis lOO which rotatably supports the lens (11), 1
5 is a locking mechanism for fixing the lens l to be tested on the mount ll; 17 is an air cylinder for driving the locking mechanism 15;
8 is a DC motor that rotates the mount 11. (Fran) 11 forms an opening for passing the inspection light in the center of the disk-shaped substrate 12, and -L of this substrate 12.
Lens a placement part 1 that can position the lens 1 to be tested on the surface Ml
3. It has a substantially disk-shaped appearance with a fitting portion 14 for the bearing post 101 protruding from the lower surface. A gear 12A is formed on the outer peripheral end surface of the substrate 12 over the entire circumference, and the lens l to be tested is placed between the lens a and the lens a at two opposing locations around the lens storage section 13 on the top surface of the substrate 12. Okibe 13
A locking mechanism 15 is provided for fixing to. The fitting portion 14 fits into a bearing boss 101 fixed to the chassis 100 via a bearing 102, and is rotatably installed in the chassis 100. The upper surface of the lens storage section 13 serves as a reference surface 13A, and positions are formed in the front-rear and left-right directions (not shown). When the lens is placed in contact with the flange for attaching the lens to the camera body, the vertical, front, back, φ and left and right positions of the test lens l are determined with respect to the mount 11 (
In other words, it is configured to be in a positioned state. The DC motor 18 is fixed to the lower surface of the chassis 100 on the side of the mount 11, with its spindle 18A facing upward. Spindle 1 that penetrates chassis lOO and protrudes upward
A gear 181 is fitted and fixed to the upper end of 8A.
1 meshes with the idle gear 16, and the idle gear 16 meshes with the gear 12A on the outer periphery of the board 12 of the mount 11 (Fran) 11.
is designed to be rotationally driven. In the locking mechanism 15, a link plate 152 is rotatably supported on the side surface of a post 151 erected on the upper surface of the base plate 12 at a substantially central portion of the link plate 152.
A pin 152A fixed to the tip of the link plate 152 is fitted into a notch 5153A of the lock plate 153, and the lock plate 153 also rotates as the link plate 152 rotates. The lock plate 153 has a plate shape with a predetermined thickness, and has an open cutout 153A formed at the upper end and a protruding claw 153B from one side end, with the claw 153B on the lens mounting section 13 side. It is rotatably supported by a boss 151 on the lower end side. Further, the link plate 152 and the lock plate 153 are connected by a spring 154 on the outside of their respective pivot positions (on the side opposite to the lens mounting portion 13), and the spring 154 connects the lock plate 153 with the link plate 152. is pulled and biased against the link plate 152 in a direction that causes the claw 153B to rotate toward the lens mounting portion 13 side. The rotation of the lock plate 153 is regulated by the claw 153B coming into contact with the upper surface (reference surface 13A) of the lens a holder 13. At this time, the force with which the claw 153B presses the reference surface 13A is It is set to provide a predetermined pressing force sufficient to hold l. The air cylinder 17 is installed on the chassis 100 outside the link plate 152 with the position of the rod 17A corresponding to the upper side of the pivot point of the link plate 152, and the air cylinder 17 is driven to extend the rod 17A. When the rod 17A is
Press the upper end of 52 and rotate it (rotate so that the upper end moves the lens toward the placement part 13 and the lower end moves to the side opposite to the lens 11.M part 13), and lock plate 153 via pin 152A. The claw 153B is configured to rotate in a direction away from the lens mounting portion 13 (indicated by an arrow in the figure). Note that the air cylinder 17 in the figure is one of the locking mechanisms 15.
Although only the one for the locking mechanism 1 is described, the other locking mechanism 1
5 may be arranged in the same manner, or both lock mechanisms 15 may be connected by a link mechanism or the like so that they operate synchronously. (Function) Then, the air cylinder 17 is driven to lock the lock plate 1.
53 in the direction in which the claw 153B moves away from the lens storage section 13, the reference surface 13A of the lens storage section 13
It becomes possible to store (or remove) the lens 1 to be tested above. In this state, the lens l to be tested is positioned a on the reference surface 13A, and the air cylinder 17 is driven in the opposite direction to release the link plate 152 from being suppressed.
The lock plate 153 rotates with the tensile force of 4, and the claw 153B locks the flange IA of the tested lens l into the lens @, M
13 to place the lens to be tested on the reference surface 13A.
(on the mount). Furthermore, by rotating the DC motor 18 to drive the mount 11t, the lens 1 to be tested fixed on the flange 11 can be rotated around its tip axis, and can be rotated to any desired position (angle). It can be stopped at The drive control of the air cylinder 17 and the DC motor 18 is performed by a control section 4, which will be described later. r Optical system 2 (configuration) As shown in FIG. 1, the optical system 2 includes a light source section 21 that forms two light beams, axial light and off-axis light, and a light source section 21 that forms two light beams, axial light and off-axis light. Each chart CA-CZ is a transmission grating with a predetermined pitch arranged at a transmitting position, and each light flux (on-axis light LA and off-axis light LZ) passes through the chart CA-CZ and the test lens 1. Mirror 22#2 that reflects and refracts the optical path and guides it to the contrast measuring section 3, which will be described later.
3. It is composed of collimator lenses 24-24 arranged on each light beam optical path. As shown in FIG. 4, the light source unit 21 includes a halogen lamp 211. The halogen lamp 2
It is constructed by arranging two filters 212φ213, a condenser lens 214, a diffuser plate 215, an on-axis fixed half mirror 216, and an off-axis movable mirror 217 in the order described above for adjusting the light from 11 to a predetermined spectral characteristic. ing. A parabolic reflecting plate 211A is provided on the back side of the halogen lamp 211 (the side opposite to the light beam output side), and focuses the light from the halogen lamp 211 at a predetermined position (indicated by f in the figure). It looks like this. Two filters, an infrared absorption filter 212 and a color correction filter 213, are placed in front of the optical path from the focal point If, followed by a condenser lens 214 and a diffuser plate 215 in that order. In front of the optical path from the diffuser plate 215, an axial fixed half mirror 216 is fixedly arranged at an angle of 45° with respect to the optical path.
Next, an off-axis movable mirror 217 is arranged. The off-axis movable mirror 217 has an adjustable angle and is movable back and forth in a direction parallel to the light beam from the halogen lamp 211, so that the off-axis movable mirror 217 can adjust the angle of the off-axis movable mirror 217. The angle is adjustable. Separate charts CA-CZ are mounted on the chassis 10 in front of the test lens 1 (that is, on the light source section 21 side of the furan 11) on the optical path of the on-axis and off-axis lights LA-LZ emitted from the light source section 21.
It is fixed at 0. As shown in FIG.
This is a rectangular wave grating in which a plurality of light-opaque line portions are formed by vapor-depositing chromium. Then, the axial light LA is transmitted to a point M (i.e., the test lens l
On the optical axis of the optical axis of
A 10 liter off-axis chart CZ is arranged respectively. In addition, the arrangement direction of each chart) CA-CZ is such that the pitch direction (direction perpendicular to the marked line) is radial from the center of the test lens l in the off-axis chart CZ, and the direction in which the pitch direction (direction perpendicular to the scored line) is radial from the center of the test lens is also arranged in the same direction as this off-axis chart CZ. The mirrors 22-23 fix the optical path extension of the axial light LA through the 0-axis on-axis chart) CA and the test lens I, and fix the on-axis mirror 22 at a predetermined position on the 0-axis chart) CA and the test lens I. It is constructed by arranging an off-axis mirror 23 at a predetermined position on the optical path extension of the off-axis light LZ via the lens l. The axial mirror 22 transmits axial light L along the optical axis of the test lens L.
On-axis sensor 31A of the contrast measuring section 3, which will be described later.
The light beam is fixedly installed at a predetermined position on the optical axis of the lens to be tested at an angle of 45 degrees with respect to the optical axis of the lens to be tested so that the light is reflected at right angles toward the lens. As shown in FIGS. 7 and 8, the off-axis mirror 23 is attached to a guide rail 231 fixed to the chassis 100 via a slide base 232 and a mirror holder 233, so that the distance and installation from the optical axis of the lens l to be tested are determined. It is installed so that the angle can be adjusted. The guide rail 231 is fixed to the chassis 100 horizontally with its longitudinal direction facing an off-axis sensor 31Z of the contrast measuring section 3, which will be described later. The slide base 232 is slidably and irremovably fitted into the guide rail 231 at its lower surface, and is slidably movable along the longitudinal direction of the guide rail 231.
It can be fixed in a predetermined position by a locking mechanism (not shown). The mirror holder 233 is integrally fitted with the slide base 232 in a manner that cannot be removed. It is slidable and rotatable in the fitting portion 234. The rotational position of the mirror holder 233 with respect to the slide base 232 can also be fixed at any angle by a fixing mechanism (not shown). The direction of the rotation axis of the mirror holder 233 is a horizontal direction perpendicular to the sliding direction of the off-axis mirror 23 (ie, the longitudinal direction of the guide rail 231). Further, a mirror holding part 233A is provided upright on the upper surface of the mirror holder 233, and a mounting hole 233B is formed through the mirror holding part 233A near the upper end thereof. On the back surface of the off-axis mirror 23, a cylindrical mounting bar 23A is fixed with adhesive at its end surface.The mounting bar 23A is fitted into the mounting hole 233B of the mirror holder 233, and the mounting bar 23A is Two set screws 233
By tightening from the orthogonal direction at C, the mirror holder 2
Off-axis at 33. The zero mirror configuration in which the mirror 23 is fixed allows the off-axis mirror 23 to be fixed without being distorted. Although in FIGS. 7 and 8, the axis mirror 23 is at an angle perpendicular to the optical axis direction, it is actually installed at a predetermined angle as shown in FIG. The collimator lens 24 is connected to the chassis 100 on the optical path that is refracted by the on-axis mirror 22 and the off-axis mirror 23 and goes to the contrast a constant part 3 via the unit base 313 of the sensor part 31 of the contrast measurement i3, which will be described later. Fixed and placed. (Function) In the light source section 21, the light from the halogen lamp 211 is passed through an infrared absorption filter 212 and a color correction filter 213.
As a result, the light has predetermined spectral characteristics as shown in FIG. 5(d), and is emitted toward the test lens l as on-axis and off-axis lights LA-LZ. FIGS. 5(a), (b), and (c) are graphs showing the emission spectral characteristics or transmission spectral characteristics of each component constituting the light source section 21, and in each figure, the horizontal axis is the wavelength, and the vertical axis is the wavelength. It is emissivity or transmittance. Explain each graph. (a) shows the emission spectral characteristics of the halogen lamp 211 alone. (b) is the transmission spectral characteristic of the color correction filter 212 alone, and the color correction filter 212 has a center transmission wavelength of 460
(c) is the transmission spectral characteristic of the infrared absorption filter 213 alone, and the 50% cut wavelength is 750 nm. (d) shows the halogen lamp 211. Infrared absorption filter 2
This is the spectral characteristic of transmitted light when the 131 color correction filters 212 are combined as shown in FIG. That is, the light emitted from the light source has the spectral characteristics shown in (d). Light with this spectral characteristic is
CCD sensor 31A of the contrast measuring section 3, which will be described later.
In combination with the light reception spectral characteristics of No. 312 (FIG. 5(e)), the spectral characteristics substantially match the visual sensitivity. The light processed to have such spectral characteristics is diffused by a diffusion plate 215 to focus on the filament image of the halogen lamp 211, and approximately 50% of the light is directed upward as axial light LA by an axial fixed half mirror 216. It is reflected at right angles towards. The light transmitted through the on-axis fixed half mirror 216 is reflected toward the road at a predetermined angle by the off-axis movable mirror 217, and becomes off-axis light LZ. As described above, the off-axis movable mirror 217 can move back and forth in the direction parallel to the light beam, and can change and adjust the angle of the off-axis light LZ with respect to the optical axis by changing and adjusting the angle.
The off-axis measurement position can be changed and it can be adapted to the type of lens l to be tested. The on-axis and off-axis light beams LA and LZ from the light source section 21 are transmitted through the on-axis char ()CA and the off-axis char ()CZ, respectively, and enter the test lens l. On-axis and off-axis light fluxes LA and LZ that passed through the test lens l
are reflected by an on-axis mirror 22 and an off-axis mirror 23, respectively, and the image forming position is shortened by a collimator lens 24, and the light beams enter a contrast measuring section 3, which will be described later. Note that the movement and rotation of the off-axis mirror 23 is performed by the light source unit 2 described above.
When the angle of the off-axis light LZ with respect to the optical axis is changed by adjusting the off-axis movable mirror 217 in step 1, the off-axis light LZ
is adjusted so that it is incident on the sensor 312 of the contrast measuring section 3. “Contrast Measuring Unit 3” (Configuration) The contrast measuring unit 3 includes a sensor unit 31 in which CCD sensors 31A and 312 are arranged on the optical paths of the on-axis light LA and off-axis light LZ, respectively, and a It is constituted by an arithmetic unit 32 that performs arithmetic processing on two on-axis and off-axis signals. The sensor section 31 includes on-axis and off-axis CCD sensors 31A.
312 is configured to be movable in the direction of the light beam, but its configuration is the same on-axis and off-axis, and the explanation on the outside of the axis will be omitted by explaining the on-axis side. The arithmetic unit 32 includes an arithmetic circuit 32A that arithmetic processes the on-axis signal from the CCD sensor 31A of the sensor unit 31, and an arithmetic circuit 32Z that arithmetic processes the out-axis signal from the CCD sensor 31Z of the sensor unit 31. be done. The configuration is the same on-axis and off-axis, similar to the sensor section 31, and the explanation on the outside of the axis will be omitted by explaining the on-axis side. The sensor section 31 is introduced into the contrast measuring section 3 by the optical system 2, as shown in FIG. 9, FIG. 10, which is a sectional view taken along the line X-X in FIG. a CCD sensor 31A that receives the axial light LA; a sensor board 311 that holds the CCD sensor 31A; Slide base 312 to which the sensor board 311 is fixed
, etc. are arranged in a predetermined positional relationship on the unit base 313 to form an integrated unit. The unit base 313 has two slide shafts 314A of the linear bearing 314, and the optical path of the axial light LA (
The slide shirt is fixed parallel to the optical axis)
Two slide pieces 314B are slidably fitted into each of the slide pieces 314A. The slide base 312 is installed on the unit base 313 by fitting and fixing each slide piece 314B to the lower surface thereof, and is movable in the optical path direction of the axial light LA. Further, an acid screw 315 is fixed to a substantially central portion of the lower surface, and the axial light LA of the unit base 313 is fixed to the acid screw 315.
A pulse motor 3 fixed to the end face on the side opposite to the incident side
16 spindles and connected screw shirt) 31
7 are screwed together. The sensor board 311 is an electric circuit board that detects (measures) the light intensity of the image of the axial char (CA) caused by the axial light LA that has passed through the test lens 1 as an analog signal.
A CCD sensor 31A that senses At- and outputs an electric signal corresponding to the amount of light, and the CCD sensor 31 (not shown).
It is composed of a drive circuit A and peripheral circuits such as a sample & hold circuit. The CCD sensor 31A is a line sensor in which pixels are arranged in a row, and is fixed to the front side of the sensor board 311, but its light receiving surface is perpendicular to the axial light LA and its line direction is aligned with the axial chart CA. It is vertically fixed to the slide base 312 in alignment with the pitch direction. That is, it is provided on the front surface of the sensor board 311 with its pixel arrangement direction perpendicular to the lattice direction of the image of the on-axis chart CA by the on-axis light LA. Note that the collimator lens 24 of the optical system 2 described above is fixed to the front end of the unit base 313. The arithmetic circuit 32A is configured as shown in the block diagram shown in FIG. The sensing signal So is processed and the contrast of the image of the on-axis chart CA is output. In other words, in this arithmetic circuit 32A, the CCD sensor 31A
is connected to the bypass filter 321 and the integration circuit 322 via the aforementioned sample and hold circuit (not shown), and the bypass filter 321 is connected to the absolute value circuit 323.
connected to. The absolute value circuit 323 is the integral circuit 3
24, and the integrating circuit 324 is connected to a sample & hold circuit 325. Furthermore, one of the integrating circuits 32
2 is connected to the sample & hold circuit 326,
These sample and hold circuits 325 and 326 are both connected to a division circuit 327. (Function) In the sensor section 31, the slat base 312 slides along the slide shaft 314A by the rotation of the pulse motor 316. That is, the CCD sensor 31A is driven to move in the optical axis direction of the axial light LA. The arithmetic circuit 32A is a CCD sensor 3LA of the sensor section 31.
The optical image signal So sent from the lens is decomposed into an AC component and a DC component, both of which are integrated for a predetermined time, and the ratio of the integral values of the AC and DC components is output as the contrast of the tested lens l. . The bypass filter 321 receives the optical image signal S. Take out the AC component inside. The absolute value circuit 323 outputs the absolute value of the AC component obtained by the bypass filter 321, that is, the value obtained by rectifying the negative AC component to the positive side. The integrating circuit 324 integrates the absolute value sent from the absolute value circuit 323 over a predetermined time. That is, the integrating circuit 324 integrates the alternating current component within the optical image signal So. On the other hand, the other integrating circuit 322
The optical image signal So sent from the CD sensor 31A is directly integrated for a predetermined time, and the integrating circuit 322 integrates the DC component of the optical image signal So. Note that each of the integration circuits 322-324 is reset by a reset signal To, and its integration time is controlled by an integration signal TI. The sample and hold circuit 325 samples the integral value of the integration circuit 324 and sends it to the division circuit 327.
Similarly, the sample and hold circuit 326 is connected to the integrator circuit 32.
The integral value of 2 is sampled and sent to the division circuit 327. The sampling timing is controlled by the sample signal T2. The division circuit 327 receives the optical image signal So from the integration circuit 324.
A division is performed in which the integral value of the alternating current component within is divided by the integral value of the direct current component of the optical image signal So by the integrating circuit 322, and the division result is output as the contrast of the lens 1 to be tested. The optical image signal So is a rectangular wave signal because the on-axis chart cA is a rectangular grid (the rectangular wave signal includes a DC component and is raised). A wave signal can be expressed as a composite of several sine waves with different frequencies.9 Therefore,
The fact that the above calculation output from the calculation circuit 32A becomes the contrast of the lens 1 to be tested will be explained by replacing the optical image signal 50 with the sine wave signal S1 shown in FIG. In the figure, a is the maximum value of the sine wave signal S1, that is, the maximum amount of light, b is the minimum value of the sine wave signal SI, that is, the minimum amount of light, and T
is the period of the sine wave signal Sl. The alternating current component of this sine wave signal Sl is expressed as (ab) a Sin ωt (3) where ω is the angular velocity. Also, its DC component is. It is expressed as Now, focusing on one period of the AC component, integrate the AC component and the DC component, and calculate the ratio of the integral values. π (a+b), and the above equation (5) differs from the above-mentioned equation (2) in that 2
Although it is multiplied by the constant /π, it becomes the contrast itself. That is, in the arithmetic circuit 32A, the CCD of the sensor section 31
The optical image signal So sent from the sensor 31A is passed through a high-pass filter 321. The AC component is integrated over a predetermined time by an integrating circuit 324 via an absolute value circuit 323,
The other integrating circuit 322 integrates the DC component. Then, the division circuit 327 divides the integral value of the AC component by the integral value of the DC component, that is, the division shown in equation (5) is executed, and the division result becomes the contrast of the lens 1 to be tested. The above explanation has been made by replacing the optical image signal SO with the sine wave signal S1 shown in FIG. Since the area ratio of the AC component to the DC component of the optical image signal SO is calculated using It is. Note that the drive control and calculation circuit 32A of the sensor section 31
The calculation control is performed by a control section described later. "Control Unit 4" (Configuration) The control unit 4 is configured by a microcomputer including a CPU and memory, together with a determination unit 5 to be described later. This control section 4 controls each section of the lens tester LT (lens mount section lO and contrast Jll constant M3) according to a predetermined control program 4A (shown in FIG. 47) in the memory, and controls the contrast It controls all measurement operations. (Function) The control section 4 controls the CCD sensor 3 of the contrast measurement section 3.
1A in the optical axis direction of the test lens 1, and move it in the optical axis direction of the test lens 1 on-axis and off-axis.
At the same time, the contrast of the chart image is measured at that point, and the lens holding part 10 is driven to rotate the test lens around its optical axis to change the off-axis measurement point and adjust the optical axis of the test lens. The contrast of the chart image at point *a in the direction is measured at a plurality of predetermined off-axis positions, (
Measurement 1) From the measurement results of the measurement 1, it is possible to know the following optical characteristics of the lens 1 to be tested. (The determination of quality by comparing these measurement results with reference values is performed by the determination unit 5, which will be described later.) (1) Change in the position on the optical axis where the contrast at each measurement point on the axis shows the maximum value From this, the degree of axial astigmatism can be detected. (2) Compare the V-equal position (average image plane position) at the position l on the optical axis where the contrast is at its maximum value at each measurement point on the axis with the reference image plane position of the lens to be tested l. Therefore, it is possible to detect whether the back focus of the lens l to be tested is over or under. (3) The degree of off-axis astigmatism can be detected by changing the position in the optical axis direction where the contrast is at its maximum value at each off-axis measurement point. (4) Curvature or inclination of the image plane can be detected by comparing the position W1 (ie, image plane position) at which the contrast is at its maximum value at an off-axis measurement point with the on-axis image plane position. (5) The degree of axial coma aberration can be detected from the difference in the maximum value of contrast at each measurement point on the axis. (6) Insufficient on-axis contrast can be determined from the average value of the maximum contrast values at each measurement point on the axis. (7) Insufficient contrast in a part of the axis can be determined from the minimum value among the maximum values of contrast at each measurement point on the axis. (8) Insufficient off-axis contrast can be determined from the average value of the maximum contrast values at each off-axis measurement point. (9) The degree of off-axis coma aberration can be detected from the difference in the maximum value of contrast at each off-axis measurement point. For example, if the lens to be tested is for a camera using 35mm film, the measurement point that makes such detection possible is the angle of view of the 35mm film (36s+m) at the image plane position.
x24+ms) diagonal angle (■, ■, ■, ■ in Fig. 14), and the off-axis position is a position at a predetermined distance necessary for determination from the on-axis position (in this example, h = However, if the purpose is only to detect curvature collapse by comparing the image plane position at the off-axis measurement point and the on-axis image plane position. For example, three off-axis measurement points are sufficient. Next, based on the on-axis contrast measurement results obtained from the above measurements, the CCD sensor 31At is fixed at the position on the optical axis where the contrast at each measurement point is the maximum value, and the lens holder is The CCD sensor 31A of the contrast a foot means 3 is moved so that the lens 1 to be tested is rotated around its optical axis by driving the lens 10, and the contrast of the chart image at a predetermined off-axis measurement point is measured. Measurement of drive and chart image contrast, and lens holder l
Controls the drive of O (rotation of the test lens l). (J
(2) From the measurement results of measurement 2. (1) On-axis astigmatism can be detected from the difference in contrast values at each measurement point on the axis. (2) Insufficient contrast on the axis can be detected from the average value of contrast at each measurement point on the axis. (3) Partial deficiency in on-axis contrast can be detected from the minimum value of contrast at each measurement point on the axis. (4) Insufficient off-axis contrast can be determined from the average contrast at each off-axis measurement point. (5) From the difference in contrast values at each off-axis measurement point,
Judgment is made for poor variation in off-axis contrast. The off-axis measurement point in this detection is 1, for example,
(If the lens for a camera using 35mm film is of a type that does not rotate during focusing, such as a straight helicoid, the image plane position will be as shown in Figure 14.
35. The on-axis position in 8 directions (■ to ■ in Fig. 14) on the horizontal and vertical lines centered on the diagonal line of the angle of view of the film (36mm x 24cm) and the upper axis M (center of the optical axis). It is sufficient to measure at a position at a predetermined distance from (in this example, the same position of h-15mm as in measurement 1 above). However, in the case of a 35m layer film, the measurement point on the vertical line (in the figure (2) and (2) are out of the viewing angle at a position 15 mgm from the on-axis position, but are effective for obtaining data such as curvature of the field of view. In addition, in the case of a test lens l whose orientation is not constant due to rotation of the lens due to focusing, such as a one-turn helicoid, as shown in Fig. 15, 12
The azimuth (■ to o) may be set to 0; the distance from the axial position on the image plane to the measurement position may be appropriately set according to the viewing angle of the lens l to be tested. Next, specific operation control will be explained based on a flowchart. FIG. 16 is a flowchart of a control program 4A of the control section 4 and a determination program 5A described later. This control program 4A is stored in the memory constituting the control section 4, as described above, and consists of a plurality of subprograms (subroutines). That is, this control program 4A includes the initial setting subroutine 41. Measurement preparation subroutine 42° Contrast measurement subroutine 43. Contrast measurement subroutine 4
4. It is composed of a parts recovery & data transfer subroutine 45. Each subroutine will be explained below according to the flow shown in the figure. The initial setting subroutine 41 sets the optical system 2, each driving mechanism section 9 of the contrast measuring section 3, the display section 6, the memory in the microcomputer of which the control section 4 is constructed, etc., to their respective initial states. Note that this initial setting subroutine 41 is executed only once when the power is turned on. The measurement preparation subroutine 42 checks the pneumatic pressure of each pneumatic mechanism, confirms that the lens 1 to be tested is set in the lens mount section IO, clears the display section that displays defects and defective items, and clears the display section that displays defects and defective items. The sensor board 311 is moved to its initial set position (reference position) and stopped, and the amount of transmitted light of the lens to be tested is measured to detect dirt on each chart CA, CZ and major abnormalities in the optical system (for example, when the focus is narrowed down). ), etc. The contrast measurement subroutine 43 scans (moves) the sensor board 311 of the sensor unit 31 in the direction of shortening the optical path by approaching the test lens 1 while measuring the contrast at every predetermined distance from the scanning start position (reference position). In this embodiment, the scanning width (travel distance) of one scanning step is set to 1/12 am, and the scanning speed is approximately 240 Step/See.The power source for this scanning is Although a pulse motor 316 is used, a motor with an encoder or the like may also be used. As a result, a characteristic curve of the contrast value against the day focus amount as shown in FIG. 17 is obtained, and the contrast peak value and its position can be obtained both on-axis and off-axis by calculating the a value. Furthermore, the contrast measurement subroutine 4
In step 3, the contrast measurement is performed four times by rotating the lens to be tested and changing its measurement point. (Measurement I) The contrast a constant subroutine 44 sets the on-axis and off-axis sensor boards to the average on-axis image plane position. This means that the film surface that is in focus at the center (design value) is
This corresponds to setting each off-axis CCD sensor. Then, the on-axis and off-axis contrasts are measured in several predetermined directions (71 constant 2 described above).In other words, in the case of a test lens of a type in which the lens does not rotate, such as a straight helicoid, the contrast is measured in 8 directions shown in Fig. 14. In the case of a type of lens to be tested in which the orientation of the lens is not constant, such as a rotating helicoid, measurements are taken in 12 directions as shown in FIG. The measurement direction is determined by the lens mount section 10 depending on the type of lens 1 (7) to be tested.
Control and change the rotation of. The parts return & data transfer subroutine 45 returns the stop position of the lens mount part 10 to a predetermined initial position, releases the lock mechanism 15, and makes it possible to remove the test lens 1 from the lens tester LT. Output the measured value to the personal computer (described later), and if the measured contrast is lower than the previously measured value,
Clean the char) CA and CZ by blowing air onto the char) CA and CZ from one side and suctioning it from the other. Next, each major subroutine will be explained in detail. The contrast measurement subroutine 43 is a subroutine for finding on-axis and off-axis focus positions (image plane positions). Contrast measurement is performed using the lens to be tested as shown in Figure 1.
On-axis and off-axis sensor boards (CCD sensor 3
1A. 31 Z). Each CCD sensor 31A・
312 moves l scanning steps every time the contrast is measured once. As a result, the contrast shown in No. 18 [1]! ~Contrast VSS (characteristic curve of contrast value with respect to day focus amount is obtained. All of these contrast values are stored in memory and used for a predetermined scan @ WS
After the S scan is completed, the peak value of the contrast and its image plane position are calculated by the determination unit 5, which will be described later. Furthermore, the lens 1 to be tested is rotated to change the orientation of the lens with respect to the off-axis light beam LZ, and the above measurement is performed as shown in FIG.
It is carried out regarding the direction. As a result, the peak value of contrast and its best image plane position are determined for a predetermined orientation. FIG. 18 is a flowchart of the contrast measurement subroutine 43 shown in FIG. 16. Each process (procedure) will be explained below according to the flowchart in the figure. In process [11], the sensor section 31 and the calculation section 32 measure on-axis and off-axis contrast. process

In [21], the contrast measured in process [1] is converted into a digital quantity by an A/[) converter (not shown) disposed after the @ calculation unit 32. In process [31], the contrast converted into a digital quantity in process [2] is transferred to Do of the scanning average register group provided in the control section 4. In process [4N], the scanning average register group in the control unit 4 calculates the scanning average, and the calculation result is stored in a predetermined location in the memory. In process [5], in the scanning average register group, each data on each scanning average register is shifted to the respective register. Process] 61 moves each CCD sensor by one scanning step. In process [7], the scanning (moving) bond of each CCD sensor is inspected. In other words, it is checked whether the scanning amount (movement due to scanning ff1) has reached the set number of scanning steps, and if scanning is completed, the next process is performed.

The process moves to [8], and if the scanning is not completed, the process returns to process [1]. In process [8], the contrast peak value and its position are calculated from the contrast test for a predetermined scanning width. In process [91], the measurement orientation of the lens to be tested is changed by rotating the lens framer by a predetermined angle. process

In step 101, it is checked whether contrast measurements have been completed for all set orientations (four orientations). When the measurement is completed, the contrast measurement subroutine 43 is exited and the process returns to the main control program 4A. If the measurement has not been completed, process [111] is executed. In process [11], the number of scanning steps is changed and set according to conditions, and the process returns to process (11). This is to reduce the number of scanning steps when a predetermined condition is met, thereby shortening the scanning time. Note that 411 loops from process [11] to process [7] constitute one scanning step, and in this embodiment, the processing time for one scanning step 2 is set to 4.096 ms. 4, scanning average calculation is performed using a scanning average register group during contrast measurement. Next, the operation of this scanning average will be explained. (Regarding the operation of scanning average) FIG. It is a conceptual diagram of a scanning average register group. The scanning average register group is composed of eight registers Do-D+ of a predetermined number of bits, and is provided in the control unit 4. Control unit 4
is transferred to Do of the scanning average register group in register I.
)+-07 is calculated. This average value is then transferred and stored in memory as a contrast. Thereafter, each data in the scanning average register group is shifted to an adjacent register. In other words, 00-〇I, D1 groan D2
, . . . DbmDl. Namely. Since the logic of dividing by 8 using the za method is simple, high-speed calculation is possible through such processing. Furthermore, data shifting within the register is easy with a microcomputer comprising the control section 4. Due to the following reasons, scanning average calculation is
Can be processed easily and quickly. In addition, in the above method, the contrast peak position where the sum of the registers DO to Dz7) is maximum causes a shift of four scanning steps from the sensor board position at the time when data is taken in. However, since this deviation is always constant, the position where the deviation is four scanning steps may be taken as the peak position. The first to seventh pieces of data taken into register Do, that is, the scanning average register group Do-Dy are all F.
Until ULL is reached, the scan averaged contrast is considerably lower than the actually measured contrast. However, since the measured value of this part corresponds to the bottom part of the contrast curve shown in FIG. 17, there is no problem, and the contrast obtained by taking the scanning average is always a value lower than the actual measured value, causing an error. However, this error with the actual measured value can be reduced by increasing the number of scanning steps, thereby making its influence negligible. In practice, the number of scanning steps in the scanning width wss amounts to 300 to 1000 steps. Since 1 scanning step is 4.096 s, it takes about 1 second to 4 seconds. The contrast peak value and its position are found by repeatedly comparing the contrast values for all the contrast data for each step stored in the memory.Depending on the number of scanning steps, the maximum value is about 10.
The comparison will be repeated 00 times, and since the control section 4 operates with a 2 MHz clock in this embodiment, the processing time for the size comparison requires about 100 as. (Regarding reduction of scanning time) The contrast measurement subroutine 43 measures the contrast in the four predetermined directions indicated by ■, ■, ■, ■ in the fI diagram 414, and calculates the contrast peak value and its position. However, if the following conditions are satisfied, the scanning width WSS is not scanned over the full width of the scanning width WSS, but the scanning width is reduced based on a predetermined procedure. This aims to shorten the scanning time. The conditions are: (1) There is a large difference in the amount of change due to the variation in fb when testing multiple lenses and the change in the measurement point of the image plane within each lens, and the amount of change is larger for the 8 test lenses. case. (2) When the inclination of the off-axis image plane of the test lens is small or there is no need to investigate. (3) Examine changes due to the orientation of the central image plane of the test lens,
This is the case when only the average axial image plane needs to be measured. FIG. 20 is a conceptual diagram illustrating shortening of scanning time. In the figure, the horizontal axis indicates the scanning direction of the sensor board, and the vertical axis indicates the progression of scanning time downward. Scanning of the sensor board is performed four times in four predetermined directions, but first, if the sensor board is scanned in 800 scanning steps for the -th direction, then in the next direction (■), the peak position found in direction (■) plus the predetermined Scanning is performed with a scanning width wSH (this is, for example, 200 scanning steps). - If the peak position in the direction ■ of the second time is 400 scanning steps ■, then the second scan in the direction ■ is 6
00 scan steps would be sufficient. Similarly, for the third direction (■), there are 400 scanning steps, and for the fourth direction (■), there are 400 scanning steps.
This becomes a 0 scanning step. This results in a total of 2200 scan steps for 4 scans in 4 directions, compared to a total of 3200 scan steps if all 4 scans in 4 directions were scanned at a predetermined 800 scan steps.
This saves 1000 scan steps, or approximately 4 seconds in time. “Determination Unit 5” (Structure) The determination unit 5 is constituted by a microcomputer including a CPU and memory together with the aforementioned control unit 4. Further, within the judgment section 5, two judgment registers DSO and 0S1 (not shown) each consisting of 8 bits are provided for temporarily storing judgment results. The reason why there are two determination registers, DSO and DS1, is that one determination register cannot handle the amount of data to be processed. Furthermore, the memory of the microcomputer that constitutes the determination section 5 together with the control section 4 is used as a display control memory for controlling the display section 6, which will be described later. (Function) The determination unit 5 predetermines the contrast value at each measurement point of the lens l to be measured under operational control by the control unit 4 described above in accordance with the control program 5A shown in FIG. The control program 5A, which performs pass/fail judgment by comparing with the determined judgment criteria, is stored in the memory constituting the judgment unit 5, and is composed of a plurality of subprograms (subroutines). In other words, this control program 5A
is composed of two determination subroutines 51 and 52. Here, by comparing the measurement results of 1. Measurement 1 (contrast) M determination routine 43) with the judgment criteria, (1) On-axis astigmatism defects (defects due to abnormal changes in the on-axis peak) A-ASU)) (2) Over or under back focus defect (
Mechanical back focus defect, excessive defect (fb large)
and insufficient defect (RB small)) (3) Off-axis astigmatism defect (off-axis image surface tilt defect (Z-ASU)) (4) Image surface curvature/tilting defect (under defect or A defect in which the off-axis image plane is too close to the lens side than the on-axis image plane (
■ND), and over-defect, that is, the off-axis image plane is farther from the lens side than the on-axis image plane (0VER)) (5) On-axis coma aberration defect (defect due to abnormal change in the best axial contrast (A) -CON ) ) (6) On-axis contrast deficiency defect (average axial contrast value is too small (A-MTFLO) ) (7) On-axis partial contrast deficiency defect ((A-NTFPL(8) Off-axis contrast deficiency Defective (Defect where the average off-axis contrast value is too small)
(Z-MTFLO) ) (9) Determine off-axis coma aberration defect (abnormal change in best off-axis contrast (Z-C(M4)). 2. Using the measurement results of measurement 2 (contrast measurement subroutine 44) as the criterion By comparing (1) On-axis astigmatism defect (A-ASU) (2)
On-axis contrast insufficient defect (A-MTFLO) (3) Partially insufficient on-axis contrast defect (if part of the off-axis contrast is small and under-defect (U+) I
), if part of the off-axis contrast is small and over-defective (0◆H (4) Off-axis contrast deficiency (Z-MTFLO)) (5) Off-axis contrast variation (off-axis MTF) Defects (Z-
HEN )) is determined. The results of the judgment for each item above are stored in the judgment register DS.
It is recorded by changing the state of predetermined bits 1 to 8 of O and DSI (20 for good, l for bad), and the judgment result recorded in the judgment register DSo-DSI is for each judgment. It is transferred to the display control memory every subroutine 51 and 52. Based on the determination results transferred and stored in the display control memory, each LED provided in the display section 6, which will be described later, is controlled to blink. In other words, each LED of one display unit 6 displays the contents of the display control memory,
In other words, the configuration is such that blinking is controlled according to the state of each bit (0 or 1) of the judgment registers DSO and O81, and each LED is turned off when the state of the corresponding bit is 0. In the case of 1, the light is turned on. or. The data used for the above judgment is the personal computer section P.
It is also sent to C. A detailed explanation will be given below based on a flowchart. First, the two determination subroutines 51 and 52 forming the control program 5Al will be explained according to the flow shown in FIG. The determination subroutine 51 calculates on-axis astigmatism (astigmatism), coma, off-axis astigmatism (eccentricity), and degree of coma from the results of the above-described contrast test measurement subroutine 43. moreover,
Field curvature is calculated from the difference between the on-axis average image plane position (HKNPPA) and the off-axis average image plane position (HKNPPZ). Then, by comparing these calculation results with reference values to be described later, it is determined whether the lens l to be tested is good or not and what is defective, and the determination results are recorded in the determination registers nso and flsl. The judgment subroutine 52 calculates on-axis and off-axis contrast and the state of change in contrast, and similarly to the judgment subroutine 51, determines whether the lens to be tested is good or bad by comparing these calculation results with each reference value described later. Determine the content of the defect and send the determination result to the determination register DSO and port Sl.
to be recorded. Judgment register DSO and mouth S! As mentioned above, the judgment results recorded in the judgment subroutines 51 and 52
each LE of display ff16, which will be described later, is transferred to and stored in the display control memory (for each display control memory), and based on the storage contents of the display control memory,
D blinks MW. (About Judgment Criteria) Since the criteria for judging lens quality differ depending on the type of lens to be tested, the lens tester LT has many judgment criteria in the control program 5A. All of these criteria include control program 5A.
Above, the standard values are named with STD. The reference values for the f-plane are as follows: 5TrJPPA: Image plane on the reference axis 5TDPPZ: Image plane off the reference axis 5TDPPAU: On-axis underside limit 5TDPP
^0: On-axis over side limit 5 TIIPPGU: Off-axis under side limit 5 TOPPGO: Off-axis over side limit.
i) Determined as defective. The standard value for image plane change is 5tTDPPStA: On-axis image plane change limit 8t'n
ppsz: There is an off-axis image plane change limit, and a test lens that exceeds each of the above image plane change limits is determined to have an astigmatism defect. Standard values for contrast changes. ST[1MM5A: Best on-axis contrast change limit ST[1MM5Z: Best off-axis contrast has a change limit, and a test lens that exceeds each of the above change limits is determined to have a coma aberration defect. The reference value for the minimum value of contrast. ST[1M I^: Best axial contrast limit S
TDMINZ, best off-axis contrast limit STD
MNLA: On-axis contrast limit on the mean on-axis image plane STDMNLZ: Off-axis contrast limit on the mean on-axis image plane STDMNH2: There is a limit for the average value of off-axis contrast on the mean on-axis image plane. The test lens is determined to be defective due to undercontrast. In addition, the average value of off-axis contrast on the average on-axis image plane) (5
A test lens that does not meet TDNNH2) is determined to be a highly defective lens that is not defective only in a specific direction but also has a defective average value. (About Judgment Operation) FIG. 21 174-4/4 is a flowchart of the judgment subroutine 51 shown in FIG. 16. The following describes the flow of each process (procedure) shown in the figure. In process [1], from the four axial image plane positions l (PPA) measured in four directions, PPAMAX: Maximum value PPAMIN: Minimum value HKNPPA: Average value 5APPA: The difference between the maximum value and the minimum value is determined. process

In [2], the axial image plane change limit (5TflPP
S^) and processing [difference between the maximum value and minimum value calculated in 11 (
5APP^). On-axis image plane change limit (5
TDPPSA) Difference between maximum value and minimum value (7) (
5APPA) is larger, it is determined that there is an axial astigmatism (astigmatism) defect, and a predetermined bit of the determination register (the third bit of the determination register DSO) is set to 1. Camera lenses that are rotationally symmetrical in design generally do not produce astigmatism on the optical axis.However, if the camera lens is assembled with poorly centered lenses, astigmatism may occur on the optical axis. Therefore, in the above process [21], a lens to be tested whose axial image plane position fluctuates by a predetermined amount or more is determined to have an axial astigmatism defect. Here, the processing

[2] The defect display will be explained by taking as an example the case where it is determined that the axial astigmatism (astigmatism) is defective. If it is determined in process [2] that there is an axial astigmatism (astigmatism) defect, the corresponding bit in the determination register (the third bit of the determination register DSO) becomes 1. Then, at the end of the determination subroutine 51, the contents of the determination register are transferred and stored in the display control memory (processing [23] to be described later).
), and the LED 64A (A-ASU) indicating the defect on the display section 6 (shown in Figure 25) is turned on based on the data indicating the axial astral defect stored in the display control memory. Processing [31] Under-axis limit (5TOPP)
AU),! l: Processing [11 calculations 1. average value (H
KNPPA). If the average value (HKNPPA) is larger than the on-axis underside limit (5TDPPAH), it is determined that there is an abnormality on the underside of the am mechanical back focus rb, and the corresponding bit of the judgment register (1st bit of the judgment register DSO ) is set to 1. As a result, when the contents of the determination register are transferred and stored in the display control memory, the LED of the display unit 6 that indicates the defect
Turn on 63A (fb large). In process [4], on-axis over side limit (5TDPP
AH) and the average value calculated by processing [1] (HKNPPA)
Compare with. And, on-axis over side limit (5T
If the average value (HK) IPPM) is smaller than DPPAO), it is determined that there is an abnormality on the over side of the mechanical back focus fb, and the corresponding bit of the determination register (second bit of the determination register DSO) is set to 1. . As a result, when the contents of the determination register are transferred and stored in the display control memory, the display section 6 which is an indication of the defect
Turn on LE063B (fb small). In process [5], the image plane between the X semi-axis image plane (STDPPA), that is, the design value of the axial image plane position, and the average value ()IKNPPA), that is, the average axial image plane position calculated in process [1], is Find the difference in position (5AHKNA). That is, (5T
DPPA ) - (HKNPPA) = (5AHKNA
) is calculated. In process [6], an off-axis image plane (5KPPZ) that corresponds to (coincides with) the average on-axis image plane (HKNPPA) is determined. This converts the measurement of off-axis contrast to the mean on-axis image plane (HXNPP)
This is because it is necessary to perform this on an off-axis image plane (5KPPZ) that corresponds to (coincides with) M). FIG. 22 is an explanatory diagram showing the relationship between the reference image plane position and the average image plane position calculated in process [11]. As shown in the figure, the amount of deviation from the design value of the off-axis image plane is determined by the processing [
From the difference in image plane position (5AHKNA) calculated in [5], (
5A) IKNA ) / Cos θ. In other words, Cos from the reference off-axis image plane (5TDPPZ)
θ is obtained. Note that the calculation of trigonometric functions as described above tends to require a complicated calculation program in the microcomputer that constitutes the determination section 5, and the number of program steps tends to increase unnecessarily. Therefore, in this embodiment, the above calculation is rounded off. In process [7], the under one-way limit (5
KPPZU) and over one-way IJ Mi+7to (5K
Ppzo ) is determined. That is, processing

From the off-axis image plane (5KPPZ) calculated in [6], the under-unidirectional tolerance of the off-axis image plane (5TDWt+), and the over-unidirectional tolerance of the off-axis image plane (5-0110), (5KPPZU) = (5KPPZ) ) + (5T
DWU) (5KPPZO) = (5KPPZ) −(
STD 0) is required. In process 181, the process

Check the over-unidirectional sum of the off-axis image plane calculated in [7] (5KPPZO), and if the value is negative, set (5KPPZO) = O. This is to eliminate negative values and facilitate the arithmetic processing in the determination unit 5. Processing

In [9], from the four off-axis image plane positions (PPZ) measured in four directions, PPZMAX: Maximum value PPZMIN: Minimum value HKNPPZ: Average value 5APPZ: The difference between the maximum value and the minimum value is determined. In processing [101, off-axis image plane change limit / ) (5T
DPPSZ) and processing

[Compare the difference (5APPZ) between the maximum value and the minimum value calculated in step 91. If the difference between the maximum value and the minimum value (5APPZ) is larger than the off-axis image plane change limit (5TOPPSZ), it is determined that there is an off-axis astigmatism (astigmatism) defect, and the corresponding bit of the determination register (determination register The first bit of DS1) is set to 1. This results in
When the contents of the determination register are transferred and stored in the display control memory, LE065 of the display section 6, which is an indication of the defect,
Turn on C (Z-ASU). In process [113], the under one-way limit (5KPPZU) of the off-axis image plane calculated in process [7] is compared with the average value ()IKNPPZ) calculated in process [9]. If the average value (HKNPPZ) is larger than the under one-way limit (5KPPZtl > 7th bit) is set to 1. As a result, when the contents of the determination register are transferred and stored in the display control memory, the LED 65A (UND) of the display unit 6, which indicates the defect, is turned on. , processing with the over-unidirectional limit (5KPPZO) of the off-axis image plane calculated in [7]

[Compare with the average value (HKNPPZ) calculated in 91. If the average value (HK)IPPZ) of the off-axis image plane is smaller than the over-unidirectional sum y) (5KPPZO), it is determined that the image plane is curved to the over side, which is an over-abnormality, and the corresponding bit in the determination register is set. (8th bit of judgment register O5O) is set to 1. As a result, when the contents of the determination register are transferred and stored in the display control memory, LE065B (OVER) of the display section 6, which indicates the defect, is turned on. In process [131, the average value calculated in process [91] (HK
NPPZ), that is, the difference in image plane position between the average off-axis image plane position and the off-axis image plane position (5KPPZ) calculated in process (6).
5AHKNZ). That is, (HKNPPZ
) −(5KPPZ) = (5AHKNZ) is calculated. In process [141], the off-axis image plane difference (5AHKNZ) calculated in process [13] is checked. That is, the sign of the difference (5AHKNZ) between the off-axis image planes is checked. If the difference between the off-axis image planes (5AHKNZ) is a positive value, it is considered that the off-axis image plane is on the under side than the on-axis image plane. In this case, off-axis under i (PPZGU) is (PPZGU) = (SAHKMZ) X 2 +
(5APPZ) is calculated. This off-axis under-under amount (PPZG[I) is equivalent to twice the day focus amount of the off-axis image plane from the average on-axis image plane (HKNPPA), and the larger the off-axis under-under amount is, the more the cause of contrast reduction. Next, this off-axis under-under amount (PPZGU) is compared with the off-axis under-under side amount (5TDPPZU). And off-axis underside limit (ST[1PPZU)
If the off-axis under Ik (ppzcu) is larger than , eccentricity is considered as well as curvature of the image plane toward the under side, so it is determined that the combination of under abnormality and eccentric abnormality is defective.
The corresponding bit of the judgment register (5th bit of judgment register O3I) is set to 1. As a result, when the contents of the determination register are transferred and stored in the display control memory, LE065G (U+H) of the display section 6, which indicates the defect, is turned on. On the other hand, if the difference between the off-axis image planes (5AHKNZ) is a negative value, it is considered that the off-axis image plane is located above the on-axis image plane. In this case, the off-axis over amount (PPZGO) is. (PPZGO) = (5AHKNZ) X 2 +
(5APpZ) is calculated. This off-axis over &
(PPZGO) is equivalent to twice the day focus amount of the off-axis image plane from the average axial image plane ()IKNPPA), as in the case of the off-axis under-under amount, and the larger the off-axis over-amount, the higher the contrast. First, this off-axis over amount (PPZGO), which is the cause of the decrease, is compared with the off-axis over side limit (5TDPPZO). Then, the off-axis over 1 is higher than the off-axis over side limit (8TDPPZO).
If i (PPZGO) is larger, eccentricity may be considered as well as curvature toward the overside of the image plane. It is determined that it is a composite defect of over-range abnormality and eccentricity abnormality, and the corresponding bit of the judgment register (6th bit of judgment register DS1)
Let be 1. As a result, when the contents of the determination register are transferred and stored in the display control memory, LE065N ((0+H)) of the display unit 6, which indicates the defect, is turned on. From the on-axis contrast (MTFA) of the four bonds at the image plane position, calculate the difference between the maximum value and the minimum value. MTFMAXA: Maximum value MTFMINA: Minimum value HKNMTFA: Average value

At [161], the best axial contrast change limit (STDMMSA) is compared with the difference between the maximum value and the minimum value (SAMTFA) calculated at [Process]151. Here, the best axial contrast change limit (S-DM
111SA), the difference between the maximum and minimum values (SAMT
If FA) is larger, it is determined that there is a frame defect in the on-axis contrast, and the corresponding bit of the 5 determination register (4th bit of the determination register DSO) is set to 1. As a result, when the contents of the determination register are transferred and stored in the display control memory, LE064B (
A-COM) lights up. Processing [In 171, the best axial contrast decreases? )(S
TDMINA) and the average value () calculated by processing [15]!
Compare with KNM Ding FA). Here, the average value (H
If KNIIITFA) is smaller, it is determined that the on-axis contrast value is insufficient, and the corresponding bit of the determination register (5th bit of the determination register DSO) is set to 1. As a result, when the contents of the determination register are transferred and stored in the display control memory, the LED of the display unit 6 that indicates the defect
Turn on 64C (A-MTF-LOW). In processing [18J, the best on-axis contrast limit (S
TDNINA) and the minimum value (MT
Compare with FIFINA). Here, the minimum value () is smaller than the best on-axis contrast limit (STDMINA).
If ITFNINA) is smaller, it is determined that a part of the on-axis contrast value is insufficient, and the corresponding bit in the determination register (the 6th bit of the determination register [ISO) is set to 1. As a result, when the contents of the determination register are transferred and stored in the display control memory, the display section 6 which is an indication of the defect
Turn on LED64D (A-MTF・PL). In the process [191], from the four off-axis contrasts (MTFZ) at off-axis image plane positions measured in four directions, MTF is calculated as Find the difference between. In the process [201], the best off-axis contrast limit (S
TDMINZ) and processing [191 calculated average value (HK
NMTFZ). Here, the average value ( ) is better than the best off-axis contrast limit (STIIMINZ).
IKNIITFZ) is smaller, it is determined that the off-axis contrast value is insufficient, and the corresponding bit in the determination register (3rd bit of the determination register DSI) is set to 1. As a result, when the contents of the determination register are transferred and stored in the display control memory, the LED of the display unit 6 that indicates the defect
Turn on 65E (Z-MTF-LOW). In processing [21], the best off-axis contrast change limit (STDM) IsZ) and the processing

[Compare the difference between the maximum value and the minimum value (SAMTFZ) calculated in step 191. Here, the best off-axis contrast change limit (sTD
The difference between the maximum and minimum values (SAMTF
If Z) is larger, it is determined that the off-axis frame is defective, and the corresponding bit in the determination register (the second bit of the determination register DSI) is set to 1. As a result, the above judgment register DS
When the contents of I are transferred and stored in the display control memory, the LED 65D (Z-CO
M) lights up. In process 221, a comprehensive judgment is made based on the individual judgments in the judgment subroutine 51, and all bits of the 1 judgment registers DSO and O51 are checked. In other words, if there is some kind of defect in the lens 1 to be tested,
By executing each process up to the above process [21], either bit of the judgment register DSO or DSI becomes 1.
It should be . Therefore, the judgment register DS
By inspecting the status of all bits of O and DSI, it is possible to know whether or not there is any defect in the lens l to be tested. That is, if all bits in the determination registers DSO and [1S1 are 0, the lens to be tested 1 is determined to be non-defective, and the overall good determination corresponding register (the 8th bit of the determination register O51) of the 1 determination subroutine 51 is set to 1. . This results in
When the contents of the above judgment register are transferred and stored in the display control memory, LE062B of the display section 6 displays a non-defective item.
(Good) lights up. On the other hand, if it is determined to be 1 and all the bits of the distal SO and the mouth St are inspected, and even one bit is 1, it means that the tested lens l has some kind of defect corresponding to that bit. Determine test lens 1 as defective and perform 1 determination subroutine 51
Comprehensive defect judgment corresponding register (determination register DSI 7)
bit) is set to 1. Due to this. When the contents of the determination register DSl are transferred and stored in the display control memory, the LED of the display section 6, which indicates a defective product,
62A (defective) lights up. process

[In 231, 1 judgment register DSO and 11S1
The contents of are stored in the display control memory within the memory. That is, by executing the process [231], each defect content as a determination result is stored in the display control memory, and the content is displayed by lighting on each LED of the display unit 6. In this process, the determination register DSO and the mouth S1 are registers for arithmetic processing within the determination unit 5, and a determination subroutine 52 to be described later is used.
This treatment is for reasons related to the handling of compost, such as the use of waste materials. The determination subroutine 51 executes one or more processes of 23 items in the order of description. Next, the determination subroutine 52 will be explained. In this determination subroutine 52, the test lens 1 is determined based on the contrast measured in the above-described contrast measurement subroutine 44, that is, the test lens 1 is determined based on the contrast measured at the average axial image plane. As the determination criterion here, the reference value with the STD used in the determination subroutine 51 described above is used. FIG. 24 1/2 to 2/2 is a flowchart of the determination subroutine 52 shown in FIG. 16. The following describes the flow of each process (procedure) shown in the figure. In Process 11, the measurement was performed at the average axial image plane position.
8 or 12 pieces in 8 or 12 predetermined directions @
From the on-axis contrast of >ITFMXLA: Maximum value MTFMNLA: Minimum value) IKNNFL^: Average value SAMTFLA: The difference between the maximum value and the minimum value is determined. In process [2], the best axial contrast change limit (STDMNSA) is compared with the difference between the maximum value and the minimum value (5ANTFLA) calculated in process [11]. Here, the best axial contrast change limit (STDMN
If the difference between the maximum value and the minimum value (SAMTFA) is larger than SA), it is determined that the on-axis contrast is defective, and the corresponding bit of the determination register (3 of the determination register DSO) is determined to be defective.
bit) is set to 1. As a result, when the contents of the determination register are transferred and stored in the display control memory, the LED 64A (A-ASU
) lights up. In process [31], the axial contrast limit (5TDNNLA) on the average axial image plane is compared with the average value (iIK, Fl, A) calculated in process [1]. On-axis contrast limit at mean axial image plane (S70MN17
If the average value (HKNMFLA) is smaller than A), it is determined that the on-axis contrast value is insufficient, and the corresponding bit of the determination register (5th bit of the determination register DSO) l
shall be. As a result, when the contents of the determination register are transferred and stored in the display control memory, the LED 84C (A-MTF-LOW) of the display section 6, which indicates the defect, is turned on. process

In [41], the axial contrast limit (STDMNLA) on the average axial image plane is compared with the minimum value ()ITFMNLA) calculated in process [1]. On-axis contrast limit at mean on-axis image plane (STDMNL)
If the minimum value ()ITFMNLA) is smaller than A), it is determined that a part of the on-axis contrast value is insufficient, and the corresponding bit of the 1 determination register (6th bit of the determination register DSO) is set to 1. As a result, when the contents of the determination register are transferred and stored in the display control memory, the LED 64D (A-MTF-PL
) lights up. Processing [51] Measured value (data) of off-axis contrast
Move some of the files and save the data. The 8 or 12 off-axis contrast measurements are stored in dedicated save registers (NTFZLO to MTFZL7 or III
TFZLO to NTFZLII). Therefore, when off-axis contrast is measured in eight directions, the measured value in the fourth direction, that is, the save register (NTFZL
3) Save the contents of the 8th direction save register ()lTFZL
7) Transfer to. Thereafter, the measured value in the seventh direction, that is, the contents of the save register (MTFZL6), is transferred to the save register (NTFZL3) in the fourth direction. This transfer of measured values is a preparation to simplify the calculation process in step [6], and is due to the fact that the measured value of the fourth direction is the data to be transferred to the personal computer section PC described later. This is data evacuation work. Furthermore, when off-axis contrast is measured in 12 directions, all the measurement data is used, so the process [51] is not performed and the process moves to the next process [6]. In process [6], the difference between NTFNXLZ: maximum value MTFMNLZ: minimum value HKNMFLZ: average value SAMTFLZ: maximum value and minimum value is determined from the measured value of off-axis contrast. In addition, when off-axis contrast is measured in 8 directions, save registers (IIITFZLO to MTFZL5)
Find the above six values from the contents of. Furthermore, when off-axis contrast is measured in 12 directions, the above six values are obtained from the contents of the save registers (TFZLO to MTFZLII). In process [7], the off-axis contrast measurement values saved in process [53] are returned to their original values. In other words, when off-axis contrast is measured in eight directions, the save register (MTFZ
Transfer the measured value of the fourth direction saved to L7) to the original save register (MTFZL3) and return to the original state.
Now, the measured value in the 8th direction has disappeared due to the data saving work in the process [51], but there is no problem because the measured value in the 4th direction at the symmetrical position has been secured.
If off-axis contrast is measured for orientation, the processing

There is no need to execute step 71, and immediately after executing step 61, the process moves to the next step 8. In process [8], the off-axis contrast limit (5TDNNLZ) on the average on-axis image plane is compared with the minimum value (MTFMNLZ) calculated in process [6]. Off-axis contrast limit at mean on-axis image plane (5TDNNLZ)
If the minimum value (MTFMNLZ) is smaller than , the direction of the curvature of field is inspected, since it is possible that the combination of curvature and eccentricity of the field is defective. Further, if the minimum value (IITFNNLZ) is not smaller than the off-axis contrast limit (STDMNLZ) on the average axial image plane, the process immediately moves to process [101]. The direction of field curvature has already been checked by the determination subroutine 51. In other words, (ppzco) > (ppz
cu), then over one direction, (PPZGO) < (P
PZGU), it is under one direction. Therefore, if the image plane of the lens under test is curved in one direction,
It is determined that the off-axis contrast is abnormal due to the combination of under and eccentricity, and the corresponding bit of the determination register (determination register DS
5th bit of l) is set to 1. As a result, when the contents of the determination register are transferred and stored in the display control memory, the display section 6 which is an indication of the defect
Turn on LED65G (U+H). On the other hand, if the image plane of the test lens l is overly curved in one direction, it is determined that the off-axis contrast is abnormal due to a combination of overshoot and eccentricity, and the corresponding bit in the determination register (6th bit of determination register DSI) is determined. Let be 1. This results in
When the contents of the determination register are transferred and stored in the display control memory, the LED 65 of the display section 6, which is an indication of the defect,
Turn on H (0+H). In processing [9], the limit of the average value of off-axis contrast in the average on-axis image plane (5TDNNH2) and processing [6]
Compare the average value (1 (KNNFLZ) calculated with
If NMFLZ) is smaller, it is determined that the off-axis contrast value is insufficient, and the corresponding bit of the 1 determination register (3rd bit of the determination register DSI) is set to 1. As a result, when the contents of the determination register are transferred and stored in the display control memory, the LED 65E of the display section 6, which is an indication of the defect,
(Z-MTF-LOW) lights up. In process [101], the best off-axis contrast change limit (SDNNSZ) is compared with the difference between the maximum value and the minimum value (SAN'rFLZ) calculated in process [6]. Here, the change limit of the best off-axis contrast (ST[1M
N5Z) than the maximum and minimum value difference (SAMTFLZ)
) is larger, it is determined that there is an off-axis contrast fluctuation abnormality, and the corresponding bit of the 1 determination register (determination register O51) is determined to be abnormal.
4th bit) is set to 1. As a result, when the contents of the determination register are transferred and stored in the display control memory, LE065F (Z-) of the display section 6, which is an indication of the defect,
FEN) lights up. In process [111] all bits of the decision registers DSO and DSI are checked. This is 1 judgment subroutine 5
Processing in 1

As in case [22], a comprehensive judgment is made based on the judgment made in the judgment subroutine 52, and all bits of each bit of the judgment registers DSO and DSI are checked. That is, when all bits of the 1 determination registers DSO and DSI are 0, the lens 1 to be tested is determined to be non-defective, and the overall good determination corresponding register (the 8th bit of the determination register DSI) of the determination subroutine 52 is set to 1. As a result, when the contents of the determination register are transferred and stored in the display control memory, LE062B (good) of the display section 6, which indicates a non-defective product, is turned on. On the other hand, if all the bits in the determination register DSO and the mouth S1 are checked and there is even one bit in l, it means that the tested lens l has some kind of defect corresponding to the bit. 1 is determined to be a defective product, the lens to be tested 1 is determined to be a defective product, and the general defective determination corresponding register (7th bit of the determination register DSI) of the 1 determination subroutine 51 is set to 1. As a result, when the contents of the determination register are transferred and stored in the display control memory, the LED 62A (defective) of the display section 6, which indicates a defective product, is turned on. In process [12], the contents of the determination register ports SO and DSI are stored in the display control memory within the memory. That is, by executing the process [121], each defect content as a determination result is stored in the display control memory, and the content is displayed by lighting on each LED of the display unit 6. This process is also a process for handling reasons, similar to process [23I] of the determination subroutine 51 described above. The determination subroutine 52 executes one or more processes of 12 items in the order of description. “Display unit 6” (Structure) As shown in Figure 25, the display unit 6 displays the determination result by the 荊节 determination unit 5 through a light emitting diode (
This is displayed by lighting the LED. The display panel 61 has LEDs 62A and 62B for overall judgment.
and LE for each determination item corresponding to the determination by the determination unit 5.
D ($3A-83B-84A-64B building 64C/64
D・65A-65B 65C・65D-65Eφ65F
65G-65H) are arranged at predetermined positions as shown in Figure 26. Incidentally, a power switch 66 for the lens tester LT, a measurement operation start switch, etc. are also arranged within the display panel 61. (Function) Each LED arranged on the display panel 61 is blink-controlled by the display control memory provided in the microcomputer that constitutes the judgment section 5 together with the control section 4, as explained in the above-mentioned section of the judgment section 5. be done. That is, the 0 display control memory stores the contents of the aforementioned determination registers DSO and [ISl, in which the determination result by the 1 determination section 5 is temporarily stored. And the display panel 61
Each LED indicates the content of the display control memory, that is, the determination unit 5.
Each bit corresponds to each bit of the determination registers DSO and DSI in the internal memory, and blinking is controlled in accordance with the state (0 or 1) of each bit. In other words, each LED
are turned off when the state of the corresponding bit is O, and turned on when the state is l. The correspondence between each LED and each bit of the judgment register DSO and DSI, that is, which LED corresponds to the judgment register port SO.
Which bit of O8+ and O8+ corresponds will be explained in each case in the description of the determination subroutines 51 and 5z, and will therefore be omitted here. Next, specific display contents by each LED will be explained. The overall judgment LED 62Aφ62B lights up when the lens 1 to be tested is defective (that is, when it fails even one of the various judgment criteria, in this case, one of the LEDs for each inspection item described later will always light up). However, 62B lights up when the lens 1 to be tested is a non-defective item (when all the various criteria are satisfied). Regarding the LEDs for each judgment item, 63A-63B indicates a mechanical back focus defect, 64A-640 indicates a defect on the lens axis, that is, in the center, and 65A-658 indicates a defect outside the lens axis, that is, in the peripheral area. 2 lights up indicates the defect. Hereinafter, the display (lighting) by the LED for each ``I judgment item'' will be explained individually. When the tested lens 1 clears all the criteria, 62B, which indicates a good product, lights up. If the product is defective, 62A will light up to indicate that it is a defective product.
The details (reasons) of the failure are displayed by lighting the LEDs for each determination item from 63A to 65H. 63A is a mechanical back focus excessive defect (fb
(large) lights up. 63B is a mechanical 7 orcus back shortage defect (fb
Lights up when (small). 64A lights up when there is an on-axis astral defect, that is, a defect due to an abnormal change in the on-axis peak (AJSLI). Possible causes of this defect include eccentricity and poor polishing of the constituent lenses constituting the lens 1 to be tested. 64B lights up when there is an on-axis coma defect (A-Con) due to an abnormal change in the best on-axis contrast. Possible causes of this defect include eccentricity and poor polishing of the constituent lenses constituting the lens 1 to be tested. 64C lights up when the on-axis contrast is insufficient, that is, when the average on-axis MTF value is too small (A-11TFLO). A possible cause of this defect is poor polishing of the constituent lenses constituting the lens 1 to be tested. 64D is defective (A
-MTFPL) lights up. This is a milder defect among the defects shown by 64G. Therefore, 6
When 4C lights up, 64D also lights up. 65A lights up when there is an under-defect, that is, a defect in which the off-axis image plane is too close to the lens side than the on-axis image plane (UNII). The cause of this defect may be poor spacing or large eccentricity of the constituent lenses constituting the lens 1 to be tested. 65B lights up when there is an over-failure, that is, a fault in which the off-axis image plane is farther from the lens side than the on-axis image plane (0VER). The cause of this defect may be poor spacing or large eccentricity of the constituent lenses constituting the lens 1 to be tested. 65C lights up when there is an off-axis ast defect, that is, a defect where the off-axis image surface is tilted (Z-ASU). A possible cause of this defect is eccentricity of the constituent lenses that make up the lens to be tested l. 65D lights up when there is an off-axis coma defect, that is, when there is an abnormal change in the best off-axis contrast (Z-CON). Possible causes of this defect include poor polishing and significant eccentricity of the constituent lenses constituting the lens 1 to be tested. 65E lights up when the off-axis contrast value is insufficient, that is, when the average off-axis contrast value is too small (Z-MTFLO). Possible causes of this defect include eccentricity of the constituent lenses constituting the tested lens 1, alignment defects such as changes in the distance between lenses. 65F lights up when there is a defect (Z-HEN) in which there is an off-axis contrast variation, that is, the off-axis contrast is drastically changing. 65G lights up when a part of the off-axis contrast is small and there is an under-defect (U-H). A possible cause of this defect is poor alignment of the constituent lenses constituting the lens 1 to be tested. 65H lights up when a part of the off-axis contrast is small and there is an over-defect (0◆H). A possible cause of this defect is poor alignment of the constituent lenses constituting the lens 1 to be inspected. By displaying the above-mentioned defect determination, it is possible to determine whether the lens to be inspected l is defective and also to classify the defects by cause, thereby making it possible to improve the efficiency of the inspection work. [Systemization of Lens Tester LT 1] In this embodiment, a lens tester system is constructed by connecting a personal computer (PC, which will be described later) to the lens tester LT as shown in Fig. 26, and the information (measurement and judgment data) from the lens tester LT is ). (Configuration) The personal computer section PC is a so-called personal computer, and has a computer 71. It is composed of a keyboard 72, a CRT display 73, and a printer 74. The computer 71 of the personal computer section PC is a lens tester LT.
It is connected to the microcomputer constituting the control unit 4 and determination unit 5 by a data bus DB, so that measured values from the lens tester LT and commands from the sensor unit PC are transferred to each other. . (Function) Then, in the personal computer section PC, the data input from the lens tester LT can be statistically processed to create secondary data useful for defect countermeasures 9 quality control etc. for the tested lens l. It can also be printed out using the printer 74. In addition, the measurement data and secondary data are displayed on the CRT display 7.
3 and can be printed out using a printer 74. This makes it possible to visualize the measurement data, and to grasp at a glance more detailed image plane conditions that cannot be seen from the judgment display on the display unit 6 of the Renzotes LT. FIG. 27 is an example of a graphical display of measurement data on the CRT display 73. In the graphical display, four types of graphs are displayed simultaneously on one screen (the graph at the top left of the screen is called Gl, the graph at the bottom left of the screen is called 02, the graph at the top right of the screen is called G3, and the graph at the bottom right of the screen is called G4). , these clearly represent the characteristics of the lens l to be tested. The coordinates of each graph are graph Gl, the vertical axis of G2 is the contrast and image plane position, graph G3... The vertical axis of G4 represents the contrast, and the horizontal axis represents the orientation in each graph. However, the scale of the horizontal axis represents the four directions in the contrast measurement subroutine 43 for graph Gl, G2, and graph G3. G4 represents 8 or 12 directions in the contrast measurement subroutine 44. Next, each graph will be explained individually. Graph 01 shows the peak value of axial contrast and its image plane position (best axial image plane position) in each direction measured in the contrast measurement subroutine 43, and the peak value of contrast at each fixed point on each side of the axis is shown by a solid line. , and its position N (best image plane position) is indicated by a dashed line. Note that the designed image plane position is also displayed, making it easy to understand changes in the image plane state of the lens to be tested. Graph G2 shows the off-axis contrast peak value in each direction measured in the contrast measurement subroutine 43 and its image plane position a! (best off-axis image plane position), the peak value of the contrast at each off-axis measurement point is shown by a solid line, and its position (best image plane position W) is shown by a - dotted line. The location is also displayed. Graph G3 is a graph of the on-axis contrast in each direction at the average on-axis image plane position measured in the contrast measurement subroutine 44, and the on-axis contrast is shown as a solid line, and it also indicates the quality of the lens to be tested. The reference value for determination is shown by a dashed line. Therefore, in the graph 3G. In this case, if the contrast indicated by the solid line exceeds the standard value for quality determination, the lens is determined to be non-defective in terms of axial contrast. Graph G4 is a graph of the off-axis contrast for each direction at the average on-axis image plane position measured in the contrast measurement subroutine 44. The off-axis contrast is shown as a solid line, and it also indicates the quality of the lens to be tested. The reference value for determination is shown by a dashed line. Therefore, in the graph 4G, similar to the graph 3G, if the contrast shown by the solid line exceeds the standard value for quality determination, the lens is determined to be non-defective in terms of off-axis contrast. From the above graph display, it is possible to read defects in the optical characteristics of the lens to be tested and their causes, for example, as shown below. (1) In graph G2, when the graph of the off-axis image plane position of each measurement point is expressed to intersect with the designed image plane position as shown in Fig. 28, as shown in Fig. 30 (a) It can be seen that the image plane is tilted. Such a state occurs when the constituent lenses of the lens to be tested l are decentered. (2) As shown in Figure 29, in graph G1, the graph of the on-axis image plane position of each measurement point is near the designed image plane position, but in graph G2, the graph of the off-axis image plane position of each measurement point is If the design image plane position is approximately parallel to either the upper or lower side (in the figure, the lower side, that is, the side closer to the lens),
As shown in b), it can be seen that the image plane is curved (in the figure, it is curved to the under side). Such a state occurs when there is a change in the distance between the lenses of the lenses 1 to be tested. [Effects of the Invention] According to the lens tester according to the present invention, the imaging quality of an optical system such as a photographic lens can be evaluated by quantitatively measuring the contrast of a chart image. As a result, inspection work can be automated, and the entire apparatus can be made smaller and lighter, resulting in significantly improved workability compared to conventional projection tests. Furthermore, since determination can be made through quantitative measurement, inspection can be performed with stable accuracy. In other words, it is possible to efficiently carry out inspections with stable accuracy, and it is possible to significantly reduce inspection costs including equipment costs and personnel costs. Furthermore, it is possible to determine the cause of failure from the measurement results in addition to determining whether it is good or bad, and it is possible to separate the parts into the readjustment process, and by feeding this information back to the assembly process, it is possible to reduce the defective rate.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a schematic configuration of a lens tester to which a preferred embodiment of the lens tester according to the present invention is applied, FIG. 2 is a plan view of a lens mount, and FIG. 3 is a sectional view taken along Fig. 4 is a configuration diagram of the light source section, Fig. 5 is a graph showing the radiation or transmission spectral characteristics of each component of the light source section, Fig. 6 is a plan view of the chart, and Fig. 7 is a plan view of a part of the off-axis mirror. , Fig. 8 is a left side view thereof, Fig. 9 is a plan view of the sensor section, and Fig. 1
The θ diagram is its x-X sectional view, and Figure 11 is the XI-X diagram in Figure 9.
I sectional view, FIG. 12 is a block diagram of the arithmetic circuit, FIG. 13 is an explanatory diagram of a sine wave signal related to contrast calculation in the arithmetic circuit, and FIGS. 14 and 15 are diagrams showing off-axis measurement point positions. , FIG. 16 is a flowchart of the control section and determination section, FIG. 17 is a characteristic curve of contrast value versus day focus amount obtained by measurement, FIG. 18 is a flowchart of a contrast measurement subroutine, and FIG. 19 is a group of scanning average registers. 20 is a conceptual diagram explaining the shortening of scanning time, FIG. 21 is a flowchart of the determination subroutine, FIG. 22 is an explanatory diagram showing the relationship between the reference image plane position and the average image plane position, and FIG. Figure 25 is a flowchart of the determination subroutine, Figure 25 is a plan view of the display panel, Figure 26 is a block diagram of a lens tester system to which the lens tester according to the present invention is applied, and Figure 27 is a diagram of the display of measurement results by the personal computer. Figures 28 and 29 are illustrations of the display in Figure 27, and Figure 30 is an illustration of the display in Figure 28 and 2.
An explanatory diagram of the image plane change corresponding to Fig. 9, Fig. 31 is an explanatory diagram of the conventional projection test, Fig. 32 is a graph showing the MTF curve, and Fig. 33 is the value of MTF at a single spatial frequency. FIG. 2 is a diagram illustrating estimation of the specific MTF of a lens to be tested from FIG. l...Test lens 2...Optical system 3...Contrast measurement section (contrast means) 31...CCD sensor section (detection means) 32...Calculation section (calculation circuit) 4...Control Part (operation control means) 5... Judgment part 6... Display part lO... Lens mount (lens holding part) Wavelength skin length (nm) (nm) Figure Wavelength (nm) Figure Figure Figure o0 Figure 1 □. Figure Figure Figure Figure 1 Figure 1 ↓ , 1 (16b) Figure Figure Figure Figure Direction ↑ Figure Direction Figure Figure Figure Spatial Frequency 'f - Continuation Amendment Book (Method) October 1988 26th・Display of K items 1988 Patent Application No. 174679 Name of the invention Lens tester correction person/Relationship with IG Patent applicant (052) Asahi Optical Industry Co., Ltd.

Claims (1)

[Claims] This is a lens inspection device that measures the contrast of a chart image formed by a lens to be tested and determines the quality of the lens based on the measured value, and includes a lens holding section that rotatably holds the lens to be tested; an optical system that makes light transmitted through a lattice chart of a predetermined pitch enter the lens to be tested held in a lens holder from on-axis and off-axis, and an optical path forward of each of the on-axis and off-axis light through the optical system; a contrast measuring means for calculating a contrast based on a chart image detected by a detecting means arranged movably in the optical axis direction of the lens to be tested; an operation control means for controlling the operation and measuring the contrast at a predetermined position of the image of the test lens, and comparing the contrast measured by the contrast measuring means with a predetermined criterion, A lens tester comprising: a determination section that determines the quality of a lens; and a display section that displays a determination result by the determination section.