JPH02138849A - Deficiency analysis for lens - Google Patents

Abstract

PURPOSE:To obtain useful information for quality control, process control, readjustment and the like by detecting condition of an image face with a quantitative measurement of a contrast of a chart image to enable a judgement on the propriety of a lens to be inspected while a factor of a deficiency is analyzed from the condition of the image face. CONSTITUTION:A lens mounting section 10 holds a lens 1 to be measured at a specified position so as to be rotatable in such a matter that the optical axis thereof is in the center thereof and an optical system 2 is so arranged as to make light passing through a chart CA with a specified grid pitch from on an axis along the optical axis of the lens 1 and light passing through a chart CZ with a specified grid pitch from outside the axis at a specified angle with the optical axis thereof incident into the lens 1 held with the mounting section 19. With the passage of light LA and LZ respectively from on and outside the axis from the optical system 2 through the lens 1 held by the mounting section 10 at a contrast measuring section 3, images of the charts CA and CZ are scanned in a direction of pitch of the chart images with sensors of a sensor CCD section 31. Thus, signals depending on the light density of the images are applied to an arithmetic circuit 32 to perform an analysis on the images.

Description

[Detailed description of the invention]

[Industrial Application Field] This invention measures the contrast of a chart image formed by a lens, and determines the quality of the lens based on this measurement value.
The present invention relates to a lens defect analysis method for determining defects and analyzing the causes of the defects. [Prior Art] Generally, optical lenses such as photographic lenses are subjected to a final inspection (performance inspection) by a projection test during mass production. This projection test is a test in which an operator visually checks a chart image projected by a lens to be tested (test lens) 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 of the line array (line width and pitch) of this pattern corresponds to the resolution, and from the minimum pitch line array that can be seen separately in the chart image projected on the projection plate 5', for example, 100 pieces/ram. The resolution is evaluated. The light beam from the lamp 1' is condensed by a condenser lens 2', illuminates the transmission type chart 3' from the back side, and passes through the transmission chart 3'. Transmission type chart 3' formed by this transmitted light
The image of the lens 4' is projected onto a projection plate 5' placed at a position 40 to 50 times the focal length of the lens 4' to be tested.
Enlarge and project onto the image. At this time, if the incident angle 02 of the illumination light from the condenser lens 2' to 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' Because the results are narrowed down,
The incident angle θ2 had to be sufficiently large. [Purpose of the Invention] This invention was made in view of the above background, and makes it possible to inspect optical lenses by detecting conditions such as curvature and inclination of the image plane through automatic quantitative measurement. With,
The purpose of this invention is to provide a lens failure analysis method that can analyze the cause of the failure from the state of the image plane. [Means for Solving the Problems] Therefore, in the lens failure analysis method according to the present invention, light that has passed through a lattice chart with a predetermined pitch is incident on the test lens from the axis and off-axis, and the test lens The contrast between the formed on-axis and off-axis grid chart images is
At multiple off-axis positions, measurements are taken at multiple locations in the direction of the optical axis of the two elements, and the contrast measurement values are measured at multiple points in the direction of the optical axis of the two elements. Understand the inclination and curvature of the formed image plane, and check the inclination and curvature of the image plane
The quality of the tested lens is determined by comparing the amount of curvature with a predetermined criterion, and this must be done in advance. 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 (1) on the projection plate 5' (2), and then the image is projected onto the projection plate 5'. Visually check whether the chart with a predetermined pitch at a predetermined position in the chart image is separated (in other words, whether the chart has a predetermined resolution at a predetermined position in the chart image), and It is used to check the quality of the product. [Problems to be Solved by the Invention] However, in such projection tests, the chart at a predetermined position (predetermined position off-axis) within the chart image projected on the axis, that is, with the center of the chart image in focus. This is to examine separation/non-separation, and it is sufficient if the resolution of the peripheral image at the focusing position is equal to or higher than a reference value. In other words, although it is possible to determine the final quality of the lens, even if it is defective, the cause of the defect cannot be determined, and therefore no data can be obtained that is useful for lens quality control, manufacturing process control, readjustment, etc. The cause of the defect in the lens to be tested is analyzed from the causal relationship between the image plane/) tilt/curvature with respect to the determined defect factor. 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 (
Modulation+Transfer Funct
ion, 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. Contrast) m is defined as I wax + I sin when measured using a sine wave grating, where the maximum light amount of the optical image is l5ax + the minimum light amount is in. From the maximum light amount I @aX and the minimum light amount I sin of the chart transmitted light that changes sinusoidally and is input to the test lens,
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 I si
n can be considered to be O (zero), and therefore the contrast of the input image in equation (1), which is the definition equation of MTF, is l. Therefore, if you measure the contrast of the sine wave chart image (output image) formed by the lens under test, this will mean that the maximum contrast is obtained at the spatial frequency of the chart pitch and at multiple locations on-axis and off-axis. By examining the position in the optical axis direction (that is, the imaging position) that indicates the value of
) It is possible to detect the tilting of the image forming surface as shown in the figure, the curvature of the image forming surface as shown in FIG. Therefore, if the judgment standard value and judgment standard 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 curvature, tilting, etc. of the imaging plane, it is possible to measure the test lens. 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 9-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 measured spatial frequency includes harmonics, resulting in a mixture of multiple spatial frequencies, but if the MTF of the lens to be tested is known, such as during mass production, it is sufficient to set the judgment criteria by considering the harmonic branch. This is the MTF value of the lens to be tested. 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 optical systems such as camera lenses, M
The TF is calculated (or measured after manufacturing) and is known, and also depends on the curvature and inclination of the imaging plane. 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 e(n trees/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 an ideal (designed) MTF curve and the contrast at a spatial frequency of n lines/layer is a, the chart image of the same spatial frequency formed by the test lens is If the contrast is X, the MTF of the lens under test
It can be inferred that it looks like an imaginary line. On the other hand, this has the effect that the image plane position can be detected while including harmonics. Further, from the contrast of each measurement point 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 content of the defect is derived by a predetermined analytical calculation method. is also possible. DESCRIPTION OF THE PREFERRED EMBODIMENTS [Examples of the Invention] Examples of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a block diagram of a lens tester LT for inspecting lenses, to which the lens failure analysis method according to the present invention is applied. "Overview of Lens Tester LT" (Configuration) Lens Tester LT includes a contrast measuring section as a contrast measuring means, which is composed of a lens mount section 10 as a lens holding section, an optical system 2, a sensor section 31, and an arithmetic circuit 32. 3. It is composed of a control section 4 as an operation control means, 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 this 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. The contrast between the on-axis and off-axis chart images is calculated (that is, measured). 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 1, and the lens mount section 10 to rotate the test lens l around its tip axis to change the off-axis measurement point and change the pitch direction of the chart image with respect to the test lens 1 on the axis 2. 1. Measurement of the contrast of the chart image at multiple locations in the optical axis direction of the lens to be tested is performed at multiple predetermined off-axis positions, and further, from the contrast measurement results of the axis obtained by the above measurements, The on-axis and off-axis CCD sensors 31A and 31Z are fixed at the average position on the optical axis where the contrast at each measurement point is the maximum value, that is, the contrast at each measurement point on axis 2 is the maximum value. The distance from the test lens 1 that is equal to the average distance between the test lens l and the on-axis sensor 31A that indicates the value is
The lens mount section 10 holds the lens 1 to be tested at a predetermined position so as to be rotatable about the optical axis of the lens 1 to be tested. The optical system 2 transmits light (on-axis light LA) that passes through a predetermined element pinch char) CA from an axis along the optical axis of the test lens 1 to the test lens 1 held in the lens mount section 10.
At the same time, light (on-axis light LZ) transmitted through the chart CZ of a predetermined lattice pitch is made to enter from off-axis having a predetermined angle/degree with the optical axis. In the contrast measuring section 3, the contrast measuring section 3 detects the contrast formed by the on-axis and off-axis lights LA-LZ from the optical system 2 passing through the test lens l held in the lens mount section lO.
Each CCD sensor (on-axis sensor 31A and off-axis sensor 312) of the CCD sensor unit 31 scans the A/CZ images 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 sensor 31Z is also fixed by applying the signal to the arithmetic circuit 32 (on-axis arithmetic circuit 32A and off-axis arithmetic circuit 32B), and the contrast of the chart image at each off-axis measurement point is measured by rotating the test lens l. Each CCD sensor 31A of the sensor unit 31 of the contrast measuring unit 3
31Z, the measurement of contrast, and the driving of the lens mount section 10 (rotation of the lens l to be tested) are controlled. The determination unit 5 is controlled by the operation control unit 4 and compares the contrast value of the chart image obtained by the contrast measurement unit 3 with a predetermined determination reference value, and selects an axis indicating the maximum contrast value. 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 exceeds the judgment standard, it is judged as defective and the test lens 1 is judged to be good or bad. do. 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 above components 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 10J.
It is a sectional view taken along ■-■. In the figure, 100 is a chassis of the lens tester LT (not shown in FIG. 2), 11 is a mount for positioning and holding the test lens 1, and 101 is fixed to the chassis 100 that rotatably supports the mount 11. Bearing post, 15
17 is an air cylinder that drives the lock mechanism 15; 18 is a locking mechanism that fixes the lens to be tested on the mount 11;
is a DC motor that rotates the mount 11. The mount 11 forms an opening for passage of the inspection light in the center of the disk-shaped substrate 12, and this position is determined (
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 mounting position 11 with its spindle 18A facing upward. A spindle 1 that penetrates the chassis 100 and protrudes upward.
A gear 181 is fitted and fixed to the upper end of 8A.
1 meshes with an idle gear 16, and the idle gear 16 meshes with a gear 12A on the outer periphery of the substrate 12 of the mount 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 thereof.
A pin 152A fixed to the tip of the link plate 152 is fitted into a notch 153A of the lock plate 153, and the lock plate 153 is configured to rotate as the link play I 152 rotates. Lens mounting section 1 capable of positioning and mounting the test lens l on the upper surface of the lock plate substrate 12
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 at two opposing locations around the lens mounting portion 13 on the upper surface of the substrate 12. Placement section 13
A locking mechanism 15 is provided for fixing to. The fitting portion 14 fits into a bearing post 101 fixed to the chassis 100 via a bearing 102, and is rotatably installed in the chassis lOO. The lens mounting portion 13 has a reference surface 13A on its upper surface, and is provided with positioning in the front-back and left-right directions (not shown). When the lens 1 is placed in contact with the flange (for attaching the lens to the camera body), the upper, lower, front, left, and right sides 153 of the lens 1 to be tested are plate-shaped with a predetermined thickness and cut at the upper end. The notch 153A is formed in an open manner, and a claw 153B is formed protruding from one side end, and the claw 153B is rotatably supported on the post 151 on the lower end side with the claw 153B facing the lens mounting portion 13. be. 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 mounting portion 13, but 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 on the outside of the link plate 152 so that the position of the rod 17A corresponds to the second side of the pivot point of the link plate 152, and the air cylinder 17 is driven to move the rod 17A. When the rod 17A is extended, the tip of the rod 17A presses the -1- end of the link plate 152 and rotates (the upper end moves toward the lens mounting section 13 side and the lower end moves toward the side opposite to the lens storage section 13). The opening plate 153 is rotated via the bottle 152A in the direction in which the claw 153B moves away from the lens mounting part 3 (indicated by an arrow in the figure). In addition, although the air cylinder 17 is shown only for one lock mechanism 15 in the figure, it may be arranged similarly for the other lock mechanism 15, or both lock mechanisms 15 may be connected by a link mechanism or the like. It is sufficient if the configuration is such that they operate synchronously. (Function) Then, the air cylinder 17 is driven to lock the lock plate 1.
53 in a direction in which the claw 153B moves away from the lens holder 13, the lens holder optical system 2 forms two light beams, an on-axis light and an off-axis light, as shown in FIG. A light source unit 21, each chart CA-CZ which is a transmission grating with a predetermined pitch arranged at a position where each light beam from the light source unit passes through, the chart 1-CA-CZ and the lens 1 to be examined. Mirrors 22 and 23 that reflect and refract the optical paths of the respective light beams (axis I-light LA and off-axis light LZ) and guide them to a contrast measuring section 3 to be described later, and collimator lenses 24 and 24 arranged on the respective light beam optical paths. , is composed of. As shown in FIG. 4, the light source unit 21 includes a halogen lamp 211. M halogen lamp 2
Two filters 212-213, a condenser lens 214, a diffuser plate 215, a fixed half mirror 216 for the "axis", and a movable mirror 217 for the off-axis are arranged in the order described above to adjust the light from 11 to a predetermined spectral characteristic. It is composed of On the back side of the halogen lamp 211 (the side opposite to the light beam output side), the lens 1 to be tested can be placed (or removed) on the reference surface 13A of the parabolic reflector section 13. In this state, the lens I to be tested is positioned and placed on the reference surface 13AJ2, and the air cylinder 17 is driven in the opposite direction to release the link play 1-152 from being suppressed.
The mouth/ink plate 153 rotates due to the tensile force of 54,
The claw 153B suppresses the flange IA of the test lens 1 onto the lens mounting portion 13'', thereby moving the test lens l onto the reference surface 13A''.
- (that is, on the mount 11). Furthermore, by rotating the DC motor 18 to rotationally drive the mount 11, the test lens l fixed to the mount Ill can be rotated around its optical axis.
Moreover, it can be stopped at any position (angle). Incidentally, drive control of the air cylinder 17 and the DC motor 18 is performed by a control section 4, which will be described later. "Optical system 2" (configuration) 211A is provided to condense light from the halogen lamp 211 at a predetermined position (indicated by f in the figure). Two filters, an infrared absorption filter 212 and a color correction filter 213, are placed in front of the optical path from the focal position f, 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 nozzle lamp 211. The angle can be adjusted. Separate charts CA-CZ are mounted on the chassis 10 in front of the test lens 1 (i.e., on the light source section 21 side of the mount 11) on the optical path of the on-axis and off-axis lights LA-LZ emitted from the light source section 21.
It is fixedly placed at O. As shown in Fig. 6, the charts CA-CZ are arranged at a predetermined pitch (P) in one direction on a flat glass substrate through which light can pass.
This is a rectangular wave grating in which a plurality of light-opaque line portions are formed by vapor-depositing chromium. Then, the position where the axial light LA is transmitted (i.e., the lens to be tested l
On the optical axis), there is an on-axis chart CA of P = 1/20 +am, and at the position where off-axis light LZ passes, there is an on-axis chart CA of P = 1/10.
mm off-axis char) CZ are respectively arranged. In addition, the arrangement direction of each chart CAφCZ is off-axis chart)
In CZ, the pitch direction (direction perpendicular to the scored line) is radial from the center of the lens 1 to be tested, and the on-axis chart CA is also arranged in the same direction as the off-axis chart CZ. The mirrors 22 and 23 fix the on-axis mirror 22 at a predetermined position for the optical path extension of the on-axis light LA via the on-axis chart CA and the test lens l, and also extend the optical path of the on-axis light LA through the on-axis chart CA and the test lens l. An off-axis mirror 23 is disposed at a predetermined position on the optical path extension of the off-axis light LZ transmitted therethrough. The mirror holder 233 is integrally and irremovably fitted to the slide base 232, and is slidable and rotatable in the fitting portion 234 thereof. This slide base 23
The rotational position of the mirror holder 233 relative to the mirror holder 2 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 (that is, the longitudinal direction of the guide rail 231). or,
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
An off-axis mirror 23 is fixed to 33. With this configuration, the off-axis on-axis mirror 22 converts the on-axis light LA along the optical axis of the test lens 1 into the on-axis sensor 3 of the contrast measurement unit 3, which will be described later.
1A at a predetermined position on the optical axis of the test lens 1 at a 45° angle with respect to the optical axis of the test lens 1.
It is fixedly installed at an angle. As shown in FIGS. 7 and 8, the off-axis mirror 23 is attached to a guide rail 231 fixed to the chassis 100 through a slide base 232 and a mirror holder 233 so that the distance from the optical axis of the lens 1 to be tested is adjusted. And the installation 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 23 can 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 fixed to the chassis 100 via a unit base 313 of a sensor section 31 of the contrast measurement section 3, which will be described later, on an optical path that is refracted by the axial emirror 22 and off-axis mirror 23 and goes toward the contrast measurement section 3. has been placed. (Function) In the light source section 21, the light from the /\logen lamp 211 is passed through the infrared absorption filter 212 and the color correction filter 21.
3, the light has a predetermined spectral characteristic 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. To 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% cart wavelength is 750 nm. (d) shows the halogen lamp 211. Infrared absorption filter 2
This is the spectral characteristic of transmitted light when the 139 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 received light spectral characteristics of 31Z (Fig. 5(e)), the axis "-" and off-axis light flux LA-LZ that passed through the test lens l are:
The light beams are reflected by the on-axis mirror 22 and the off-axis mirror 23, respectively, and the imaging position is shortened by the collimator lens 24, and the light beams enter the 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. By adjusting the margins below, the spectral characteristics substantially match the visibility. The light processed to have such spectral characteristics is diffused by a diffusion plate 215 in order to focus on the filament image of the halogen lamp 211, and about 50% of the light is transmitted to the axial fixed half mirror 216 as a two-dimensional LA. It is reflected upward at a right angle. 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 y, -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 by changing and adjusting the angle, the angle of the off-axis light LZ with respect to the optical axis can be changed and adjusted. The measurement position can be changed, and it can be adapted to the type of lens 1 to be tested. The on-axis and off-axis light fluxes LA and LZ from the light source section 21 are transmitted through the axial chart CA and the off-axis chart CZ, respectively, and enter the lens 1 to be tested. [Contrast measurement unit 3] (Configuration) CCD sensors 31A and 31 are provided on the optical path of the contrast light LZ, respectively.
A sensor section 31 with Z arranged thereon and an axis from the sensor section 31.
- and an arithmetic unit 32 that performs arithmetic processing on two off-axis signals. The sensor section 31 includes an axial and off-axis CCD sensor 31A.
312 is configured to be movable in the direction of the light beam, but its configuration is the same on axis ``2'' and off-axis, and explanation of the outside of the axis will be omitted by explaining only the axis ``2 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 312 of the sensor unit 31. be done. The configuration is the same on the axis J- and off-axis as in the sensor section 31, and the explanation on the outside of the axis will be omitted by explaining the axis 1- side. The sensor section 31 is introduced into the contrast IIA constant section 3 by the optical system 2, as shown in FIG. CCD sensor 3 that receives the axial light LA
1A, a sensor board 3 holding the CCD sensor 31A
11. The slide base 3121 to which the sensor board 311 is fixed is arranged in a predetermined positional relationship with the unit base 313 to form an integrated unit. Two slide shafts 314A of a linear bearing 314 are fixed to the unit base 313 in parallel with the optical path (optical axis) of the light LA, and two slide pieces 314B are respectively attached to the slide shafts 314A. They are fitted so that they can slide freely. 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 axis LA. Further, an acid screw 315 is fixed to a substantially medium flame on the lower surface and is provided on the front surface of the sensor board 311 so as to be orthogonal to the grid direction. 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. 12, and calculates the optical image signal SO detected by the CCD sensor 31A of the sensor unit 31, that is, the optical image of the axial chart (CA) transmitted through the test lens l. The sensing signal 30 is processed to output the contrast of the image of the axis-chart CA. 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 Hall 1 circuit (not shown), and the noise pass filter 321 is connected to the absolute value circuit 32.
Connected to 3. The absolute value circuit 323 is connected to an integration circuit 324, and the integration circuit 324 is connected to a sample and Hall 1 circuit 325. Furthermore, one of the integrating circuits 3
22 is connected to the sample and Hall 1 circuit 326,
The acid screw 315 has a screw shirt connected to the spindle of a pulse motor 316 fixed to the end surface of the unit base 313 on the side opposite to the three-light LA incident side.
317 are screwed together. The sensor board 311 is an electric circuit board that detects (measures) the light intensity of an axial (Nature) CA image caused by the axial light LA that has passed through the test lens 1 as an analog signal. A CCD sensor 31A that outputs an electric signal corresponding to the amount of light, and the CCD sensor 3 (not shown)
It is composed of a 1A drive circuit and peripheral circuits such as a sample and Hall circuit. The CCD sensor 31A is a line sensor in which pixels are arranged in a line, and is fixed to the front side of the sensor board 311, and its light receiving surface is perpendicular to the axial light LA, and the line direction is the axis. The slide base 312 is vertically fixed to the slide base 312 so as to match the pitch direction of the slide base 312 . In other words, the image of CA (on-axis char by light LA) is placed along the pixel arrangement direction, and these samples and Hall 1 circuit 325
・Both 326 are 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 31A of the sensor section 31.
The optical image signal So sent from the AC component is decomposed into an AC component and a DC component, and both of them are integrated for a predetermined period of time. The integral (a) ratio of N is output as the contrast of the lens 1 to be tested. The bypass filter 321 extracts the alternating current component within the optical image signal SO. The absolute value circuit 323 outputs the absolute value of the alternating current component written by the input circuit 321, that is, the value obtained by rectifying the negative alternating current component to the positive side. The integration circuit 324 receives the J- signal sent from the absolute value circuit 323.
The absolute value is integrated 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 is connected to the sensor part 31.
The optical image signal -3o sent from the CCD sensor 31A is directly integrated for a predetermined time, and the integrating circuit 3
At 22, the DC component of the optical image signal So is integrated. Note that each of the integration circuits 322φ324 is reset by the reset signal To, and its integration time is controlled by the integration value 1 to T1. 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 ball 1 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 is represented by an optical image produced by the integration circuit 324. Moreover, the DC component is expressed as follows. Here, if we integrate the AC component and the DC component and take the ratio of the mutual integral values, taking note of the - period of the AC component above, we get the equation (5) above. Unlike the formula, 2
Although it is multiplied by the constant /π, it becomes the contrast itself. That is, in the arithmetic circuit 32A, the sensor section 31(7)C
The optical image signal So sent from the CD sensor 31A is passed through the bypass filter 321. A division is performed in which the integral value of the AC component in the absolute image circuit signal (3S) is divided by the integral value of the DC component of the optical image signal So by the integrating circuit 322, and the division result is used as the contrast light of the test lens l. The image signal So is a rectangular wave signal because the on-axis chart 1-CA is a rectangular grating (the rectangular wave signal includes a DC component and is deviated).However, if Foury transform is performed, '' - The shaped wave signal can be expressed as a composite of several sine waves with different frequencies. Therefore, the optical image is expressed as follows: Signal So 13th
This will be explained in relation to the sine wave signal S1 shown in the figure. 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 S1, that is, the minimum light ψ, T
is the period of the sine wave signal S1. If the angular velocity is ω, then the AC component of the sine wave signal Sl is integrated over a predetermined time by an integrating circuit 324 via 323, and the DC component is integrated by the other integrating circuit 322. And the division circuit 327
The integral value of the AC component is divided by the integral value of the DC component,
That is, the division shown in equation (5) is executed, and the result of this division becomes the contrast of the lens 1 to be tested. As described above, the calculation output from the calculation circuit 32A becomes the contrast of the tested lens l, and the optical image signal So is converted into a sine wave signal S! shown in FIG. As explained above, since the calculation of the contrast in -1- is the area ratio calculation of the AC component to the direct component of the optical image signal SO using the integrating circuits 322 and 324, the optical image signal So is The same applies to a rectangular wave signal containing many harmonic sine waves, and there is no problem in any way. In addition, the drive control and arithmetic circuit 3 of the sensor section 31 described in -I-
Calculation control of 2A 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 10 and contrast measurement section 3) according to a predetermined control program 4A (shown in FIG. 17) in the memory.
), and controls all contrast measurement operations. (Function) The control section 4 controls the CCD sensor 3 of the contrast measurement section 3.
1A to move it in the optical axis direction of the test lens l, and measure the contrast of the chart image at multiple locations in the optical axis direction of the test lens l, both on-axis and off-axis. 10 is driven to rotate the lens to be tested about its front axis, and the off-axis measurement points are changed to measure at a plurality of locations in the optical axis direction of the L lens to be tested. (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) Partial lack of contrast on axis -L 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 can be detected from the difference in the maximum value of contrast at each off-axis measurement point. For example, if the test lens l is a lens for a camera using 35mm film, the measurement point that makes such detection possible is the angle of view of the 35mm film (36mm x
24+*m) diagonal angle (■, ■, ■, ■ in Fig. 14), and the off-axis position is a predetermined distance #h necessary for judgment from the on-axis position of the chart image. Contrast measurements are made at a plurality of predetermined off-axis positions. (Measurement 1) From the measurement results of the measurement 1, the following optical characteristics of the tested lens 1 can be known. (The quality/failure judgment by comparing these measurement results with reference values is performed by the judgment unit 5, which will be described later). From the change, the degree of axial astigmatism can be detected. (2) By comparing the average position (average image plane position) of the position on the optical axis where the contrast exhibits the maximum value at each measurement point on the axis with the reference image plane position of the subject lens l, It is possible to detect whether the back focus of the detection lens l 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) The curvature or inclination of the image plane can be detected by comparing the position where the contrast shows the maximum value (i.e., the image plane position) at the off-axis measurement point with the on-axis image plane position (this implementation In the example, measurement may be performed at h=15 mm). In addition, if the purpose is only to detect curvature/inclination by comparing the image plane position at an off-axis measurement point and the on-axis image plane position,
Three off-axis measurement points are sufficient. Next, based on the on-axis contrast measurement results obtained from the above measurements, the CCD sensor 31A is fixed at the average position on the optical axis where the contrast at each measurement point is the maximum value, and the lens holding part 10 is fixed. By driving the lens to be tested
to measure the contrast of the chart image at a predetermined measurement point off-axis by rotating the optical axis around the optical axis, and to measure the contrast of the chart image by driving the CCD sensor 31A of the contrast 11 constant means 3 and measuring the contrast of the chart image, and the lens. Holding part 10
(rotation of the test lens 1). (Measurement 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 second axis can be detected from the average value of contrast at each measurement point on the second axis. (3) A 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 41 average value of contrast at each off-axis measurement point. (5) From the difference in contrast values at each off-axis measurement point,
Defects in off-axis contrast variation can be determined. For example, if the lens to be tested 1 is a camera lens using 35 mm film and is of a type that does not rotate during focusing, such as a straight helicoid, the off-axis measurement point for this detection is the position of the image plane. As shown in the ft514 diagram, the horizontal and vertical lines centered on the diagonal line of the viewing angle of the 35mm film (36m x 24mm) and the on-axis position (optical axis center) - 8 directions (■ to ■ in Figure 14) ), So-1
The measurement may be performed at a position a predetermined distance #h from the − position (in this embodiment, the same position h=15+wm as in the measurement 1 described above). However, in the case of 351 film, the vertical line measurement subroutine 44. 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, the drive mechanism section 1 of the contrast measurement section 3, the display section 6 of the drive mechanism section 1, the memory in the microcomputer that constitutes the control section 4, 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 to be tested l is set on the lens mount section 10, clears the display section that displays defects and defective items, and displays the sensor section 31. The sensor board 311 is moved to the 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 aperture is stopped). - Although the fixed points (■ and ■ in the figure) are out of the field of view at a position 15 mm from the axis -1 position, it is effective for obtaining data such as the curvature of the field. It is. In addition, in the case of the test lens 1, such as a rotating helicoid, where focusing is difficult and the lens rotates and the orientation of the lens is not sufficient, measure 12 orientations (■ to O) at 30° intervals as shown in Figure 15. Just do it.
The distance from the "axis" 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) J
ll fixed subroutine 43. The contrast measurement subroutine 43 is performed on the sensor board 31 of the sensor section 31.
1. While measuring the contrast at predetermined distances from the scan start position (reference position), the lens 1 to be tested is approached and scanned (moved) in a direction to shorten the optical path. In this embodiment, the scanning width (moving distance) of l scanning steps is 1/12.
mu, and its scanning speed is approximately 240S.
It is tep/Sec. Further, although the pulse motor 316 is used as the power source for this scanning, a motor with an encoder or the like may also be used. As a result, a characteristic curve of the contrast value with respect to the day focus amount as shown in FIG. 17 is obtained, and by numerical calculation, the contrast peak value and its position can be obtained both on and off the axes -1 and -2. Further, in the contrast 11111 constant subroutine 43, the contrast measurement is performed four times by rotating the lens to be tested and changing its measurement point. (Measurement 1 mentioned above) The contrast foot measurement subroutine 44 sets each of the on-axis and off-axis sensor ports to the average on-axis image plane position. This corresponds to setting the on-axis and off-axis CCD sensors on the film surface (design value) that is focused at the center. Then, the on-axis and off-axis contrasts are measured in several predetermined directions (measurement 2 described above). In other words, for a test lens of a type in which the lens does not rotate, such as a linear helicoid, measurements are taken in 8 directions shown in Figure 14, and for a test lens of a type in which the lens does not rotate, such as a rotating helicoid, measurements are made in 12 directions shown in Figure 15. do. The measurement direction is changed by controlling the rotation of the lens mount section 10 according to the type of lens l to be tested. The parts restoration & data transfer subroutine 45 returns the stop position of the lens mount part 10 to a predetermined initial position, releases the locking mechanism 15, sets the test lens l to a state R1 that can be removed from the lens tester LT, and sets the contrast ratio Output the measured value to the personal computer section PC (described later), and
If the measured contrast is lower than the previously measured value, air is blown onto the char) CA and CZ from one side and suctioned from the other to clean the char) CA and CZ. 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 [2], the contrast measured in process [11] is converted into a digital quantity by a converter (not shown) disposed after the calculation unit 32. In process [3], the contrast converted into a digital quantity in process [2] is transferred to Do of the scan 1-average register group provided in the control unit 4. In process [4], 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 explained in detail, and each main subroutine is explained in detail. The contrast measurement subroutine 43 is a subroutine that searches for the axis -L and the off-axis focus position (image plane position). Contrast measurement is carried out using two optical paths LA-LZ outside the axes -1-9 with respect to the lens to be tested l, as shown in fiS1 diagram.
For each on-axis and off-axis sensor board (CC
D sensor 31A. 31 Z,). Each CCD sensor 31A
- 312 moves l scanning steps every time the contrast is measured by - degrees. As a result, contrast 1 to contrast WSS (characteristic curve of contrast value versus day focus amount) shown in FIG. 18 are obtained. All these contrast values are stored in memory and are
After the scanning is completed, the contrast peak value and its image plane position are calculated by a determination unit 5, which will be described later. Furthermore, by rotating the lens L to be tested and changing the orientation of the lens with respect to the off-axis light beam LZ, the above measurement is carried out as shown in FIG.
It is carried out regarding the direction. Shift this to star. In process [11i1, each CCD sensor is moved by one scanning step. In process [7], the scanning (movement) amount of each CCD sensor is inspected. In other words, it is checked whether the scanning amount (movement M due to scanning) has reached the set number of scanning steps, and if the scanning is completed, the process moves to the next process [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 for a predetermined scanning width. In process [91], the lens mount is rotated by a predetermined angle to change the measurement orientation of the lens to be tested. In process [101], it is checked whether or not the contrast has been measured for all of the 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 [11] is executed. In process [111], the number of scanning steps is changed and set according to the condition, and the process returns to process [11]. This is intended to shorten the scanning time by reducing the number of scanning steps when a predetermined condition f1 is satisfied. Note that the loop consisting of processing [+1] to processing [7] constitutes one scanning step, and in this embodiment, the processing time of one scanning step is set to 4.096 rss. In the control section 4, scanning average calculation is performed using a scanning average register IT during contrast measurement.Next, the operation of this scanning 11 average will be explained. (Regarding Scanning Average Operation) Figure fjS19 is a conceptual diagram of the scanning average register group. The scanning average register group is composed of eight registers DO"D7 each having a predetermined number of bits, and is provided in the control section 4. In its operation, first, the above-mentioned digital signal is input to the control section 4.
is transferred to the DO of the scanning average register group in the register D.
The average of O~DJ is calculated. It's much lower than that. However, the measured values in this part correspond to the contrast field part shown in FIG. 17, so there is no problem. Furthermore, the contrast obtained by taking the scanning average always becomes 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 a scan@WSS reaches 300-1000 steps. (2) Since the scanning step is 4.096 rxs, it takes about 1 second to 4 seconds. The peak value of contrast and its position are found by repeatedly comparing the magnitude of contrast for all the contrast data for each step stored in the memory. Depending on the number of scanning steps, up to about 10
The comparison is repeated 00 times, and in this embodiment, since the control unit 4 operates with a 2 M) lz clock, the processing time for the magnitude comparison requires approximately 100 tss. Then, this average value is transferred to memory as contrast,
be remembered. Thereafter, each data in the scanning average register group is shifted to an adjacent register. In other words, DO→D
,,D. →D2, . . . D6 → Dl. In other words, since the logic of dividing by 8 in binary is simple, high-speed calculation becomes possible through such processing. Furthermore, data shifting within the register is easy with the microcomputer that constitutes the control section 4. For these reasons, the scanning average: 11 calculation can be processed easily and at high speed. In the method described above, the contrast peak position where the sum of the registers Do to D is maximum is deviated from the sensor board position at the time when data is taken into DO by four scanning steps. However, since this deviation is always constant, the position where the deviation is four scanning steps may be taken as the peak position. First 1 to 7 pieces of data to be read into register Do 1
-1, that is, until the scanning average register group Do-DI all becomes FULL, the contrast obtained by taking the scanning average is the contrast of the actually measured contrast (regarding shortening of scanning time). There are mistakes shown in ■,■,■,■! The contrast is measured in four directions, and the contrast peak value and its position are calculated. However, if the following conditions are satisfied, scanning is performed based on a predetermined procedure without scanning the entire scanning width WSS. Decrease width. This aims to shorten the scanning time. The conditions are: (1) When there is a large difference between the variation in fb when inspecting multiple test lenses and the amount of change due to changes in the measurement point of the image plane within each test lens, and the former is larger. . (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,
"Average axis" - when only the image plane needs to be measured. It is. FIG. 20 is a conceptual diagram illustrating shortening of the scanning time. In the figure, the horizontal axis indicates the scanning direction of the sensor board, and the vertical axis indicates the progress of the scanning time downward. Scanning of the sensor board is performed four times in four predetermined directions. First, if the sensor board is scanned in 800 scanning steps in direction 1 in ``time 1'', then in the next direction 2, the peak found in direction 2 The position plus a predetermined scanning width WSH (this is, for example, 200 scanning steps) is scanned. -.If the peak position in the azimuth (2) is at the 400th scanning step, the second scan in the azimuth (2) of 1°1 will only require 600 scanning steps. Similarly, in the third direction (2), there are 400 scanning steps, and in the fourth direction (2), there are 400 scanning steps. In this way, 4 directions 4
The total number of scans is 2,200 scan steps, compared to the total of 3,200 scan steps that would have been obtained by scanning all four directions in four predetermined 800 scan steps without using this method. Seconds reduced. The RAM 5A is stored in a memory constituting the 1 determining section 5, and consists 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 measurement subroutine 43) with the judgment criteria, (1) axial astigmatism defects (defects due to abnormal changes in the axial peak (A-ASU) ) ) (2) Over or under back focus defect (
Mechanical back focus defect, excessive defect (fb large)
and insufficient defect (fb 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 (
ON port), and over-defective, that is, the off-axis image plane is farther from the lens side than the on-axis image plane.Determination Unit 5 (Configuration) The determination unit 5, together with the aforementioned control unit 4, has a CPU and a memory. It is composed of a microcomputer. Further, within the judgment section 5, there are provided two judgment registers DSO and O51 (not shown), each consisting of 8 bits, for storing the judgment result at -. The reason why there are two determination registers, DSO and DSI, is that one determination register cannot handle the amount of data to be processed. Furthermore, the memory of the microcomputer that controls 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 quality of the product is determined by comparing it with the determined criteria. Control program (0VER)) (5) Axial coma aberration defect (defective due to abnormal change in contrast on the best axis (A-CON)) (6) Axial contrast insufficient defect (average axial contrast value is too small (A-CON)) A-MTFLO) ) (7) Partial on-axis contrast deficiency ((A-NTFPL(8) Off-axis contrast deficiency (average off-axis contrast value too small (Z-MTFLO)) (9) Off-axis coma Determine aberration defects (abnormal change in best off-axis contrast (Z-CON)). 2. By comparing the measurement results of measurement 2 (contrast measurement subroutine 44) with the determination criteria, (1) on-axis Astigmatism defect (A-ASU) (2)
On-axis contrast deficiency defect (A-MTFLO) (3) Partial deficiency of on-axis contrast (a defect when part of the off-axis contrast is small and under-defective (U+H), is it a part of the off-axis contrast? If it is small and over-defect (0+H (4) Off-axis contrast deficiency (Z-MTFLO)) (5) Off-axis contrast fluctuation defect (Defect where off-axis MTF changes drastically (Z-) I
EN )) is determined. 1] - The results of the judgment for each item are determined by the predetermined focus points 1 to 8 of the judgment registers DSO and ll5I, respectively.
(20 for good, 1 for bad) and recorded in the judgment register DSO.
The judgment results recorded in the DSI are displayed in each judgment subroutine 51-
It is transferred to the display control memory every 52 seconds. 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. That is, each LED of the display unit 6 displays the contents of the display control memory,
In other words, the configuration is such that blinking is controlled in accordance with the state (0 or l) of each bit of the judgment registers DSO and DSI, and each LED is controlled by the judgment subroutine 5.
Similarly to 1, the acceptability and defect content of the tested lens 1 are determined by comparing these 1:1 calculation results with each standard Eve (to be described later), and the determination results are stored in the determination registers DSO and O3.
Record on +. The judgment results recorded in the judgment registers DSO and DSI are processed each time (judgment subroutines 51 and 52) as described above.
1σ) is transferred and stored in the display control memory, and the stored contents of the display control memory are transferred to (display 8?I6, which will be described later).
This controls the blinking of each LED. (Regarding Judgment Criteria) Since the criteria for judging lens quality differ depending on the type of lens to be tested, Lens Tester LT has many judgment criteria in the control program 5A. Control program 5A for all
The standard value name with STD prefixed with J- is digitized by 1. The reference values for the image plane include: 5TDPPA:)^half-axis'' - image plane 5TDPPZ varnish (1: If the state of the hint corresponding to the off-axis image plane is O, the light is turned off; if it is 1, the light is turned off. In addition, the data used for the JFIl determination described in I-I is also sent to the personal computer section PC, which will be described later. First, the two determination subroutines 51 and 52 that make up the control program 5A will be explained according to the flow shown in FIG. ), coma, off-axis ast (eccentricity), and degree of coma.Furthermore,
1ij on the axis! : Calculate the field curvature from the difference between the J image plane position (HKNPP^) and the off-axis \11 uniform image plane (+'/position (HKNPPZ). Then, use these Al calculation results and each node described later. , (Determine the quality and defect content of the lens l to be tested from the comparison with the quasi II′i, and determine the determination result.

[/Record in sister DSO and DSI. The determination subroutine 52 calculates the contrast outside axis-1-9 and the change in contrast by t1 calculation 5TDPP.
AU: 輔1-Anter side remint 5TDPPAO:
輼J-Over side sumin I・5TOPPCII ・Off-axis underside limit 5TOPPGO: Test lens 1 that has an off-axis overside limit and deviates from the -j-memory limit has a puncture focus fb (mechanical focus position) defect. It is determined that The reference value for image plane change is 5TDPPSA: -1, image plane change limit 5TDP
PSZ: There is an off-axis image plane variation limit, and a test lens whose memory image plane variation exceeds the mint is determined to have an astigmatism defect. Standard values for contrast changes include STDMM
SA: Best axial contrast change limit y) STD
MMSZ: There is a change limit for the best off-axis contrast, 1. A test lens whose memory change exceeds the mint value is determined to have a coma aberration defect. The standard value for the minimum value of contrast is STDM
INA: Best on-axis contrast limit STDMIN
Z: Best off-axis contrast limit STDMNL^
: On-axis contrast limit on the image plane on the average axis STDMNLZ : Off-axis contrast limit on the image plane on the average axis STDMNH2: There is a limit for the average value of the off-axis contrast on the image plane on the average axis, and it does not meet each of the above limits. The tested lens is determined to be defective due to undercontrast. It should be noted that a test lens whose average off-axis contrast on the average axial image plane (fi) is less than the limit (ST[1NNH2) is not only defective in a specific direction, but also has a large degree of defect in which the average i11 is also defective. It is determined that it is a lens. (Regarding the determination operation) FIG. 21 1/4 to 4/4 is a flowchart of the determination subroutine 51 shown in FIG. 16. Hereinafter, each process (hand 1 ho 1) shown in the figure The process will be explained according to the flow of the following. In process [11], defect display will be explained by taking as an example a case where it is determined to be defective from four axial image plane positions (PPA) measured in four directions. If it is determined in process [2] that there is an axial astigmatism (astigmatism) defect, the corresponding bit of the determination register (3 bits 11 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 data indicating the axial astral defect stored in the display control memory are used to turn on the LED 64A (A-ASU) which indicates the defect in the first display section 6 (shown in Figure 25). In process [3], the axis is "second under side" (5TD
PPAU) and processing [11 Jl calculated average value (HKNP
PM). ``Suke'' Niander side limit (5T
If the average value (1 (KNPPA)) is larger than the average value (1 (KNPPA)), it is determined that there is an abnormality on the lower side of the mechanical back focus fb, and the corresponding bit of the determination register (1 bit 11 of the determination register DSO) is set to 1. .Thus,
-1- The contents of the judgment register are in the display control memory PPAM.
AX: Maximum value PPAMIN: Minimum value HKNPPA: Average value 5APPA: Find the difference between the maximum value and the minimum value. In processing [21, axial image plane change limit A) and processing [
The difference between the maximum value and minimum value calculated in 11. (5APPA
). On-axis image plane change limit (5TQPPS
If the difference between the maximum and minimum values (5APPA) is larger than A), it is determined that there is an axial astigmatism (astigmatism) defect.
A predetermined bit of the judgment register (3 bits 1-1 of the judgment 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 a poorly centered lens, astigmatism will appear on the optical axis, so in the above process [21] the axial image plane position will change by a predetermined amount. The lens to be tested is found to have a defective axial surface area. Here, in the process [2], when transferred to and stored in the non-point acid, the L of the display section 6 which is the indication of the defect.
Turn on ED63A (large fb). In process [4], the axis "Ni-oper side sumi" (5TD
PPAO) and treatment [11 knee 1 calculated average value (HKN
PPA). Then, the average value (HKNPPM) is higher than the axis I over side limit (5TDPPAO).
If the force is small, it is determined that the mechanical back focus fb is abnormal on the over side, and the corresponding bit of the determination register (
The second bit of the judgment register DSO is set to 1. As a result, when the contents of the determination register -1- are transferred and stored in the display control memory, the LED 63B (fb small) of the display unit 6, which indicates the defect, is turned on. In process [5], the image plane position between the design value of the reference axis] image plane (STDPPA), that is, the image plane position, and the average value (HKNPPM), that is, the average axis image plane position calculated in process [11] is calculated. Find the difference (5A)IKNA). That is, (
5TOPPA) - (HKNPPA) = (5AH
KN^) is calculated. In process [6], an off-axis image plane (5KPPZ) corresponding to (-) the average axis] image plane (HKNPPA) is determined. This is equivalent to 11111 constants of off-axis contrast.
The off-axis image plane (5
This is because it needs to be carried out in KPPZ). FIG. 22 is an explanatory diagram showing the relationship between the reference image plane position δ and the average image plane position calculated in process [1]. As shown in the figure, the amount of deviation from the design value of the off-axis image plane is determined by the processing [
5], the difference in image plane position (5AHKNA) calculated by 31 becomes (5AHKNA)/GasO. In other words, from the reference off-axis image plane (5TDPPZ)
0 is required. It should be noted that the calculation of trigonometric functions as shown in "-" in the microcomputer that constitutes the determination section 5 requires a complex 51 arithmetic program, and the number of program steps tends to increase unnecessarily. Therefore, in this example, the above calculation is rounded to 3
It is 1 arithmetic. Processing [In 71, under unidirectional rimming of off-axis image plane)
(5KPPZU) and over one direction sumin) (
5KPZ) and the maximum and minimum values calculated in process [9]. (S^ρPZ). Off-axis image plane change limit (
The difference between the maximum value and the minimum value (5A
If PPZ) is larger, it is determined that there is an off-axis astigmatism (astigmatism) defect, and the corresponding focus of the determination register (1 bit [1 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 65C (
Z-ASU) lights up. In process [111], the under unidirectional rimin l-(5KPPZU) of the off-axis image plane calculated in process [7] and process [91
Compare with the average value (HKNPpZ) calculated in . If the 11 uniform image i (HKNPPZ) is larger than the under one-way limit (5KPPZU) of the off-axis image surface, it is determined that the image surface is curved to the under side, which is an under abnormality, and the corresponding bit of the determination register (determination register 7 bints of 050]) 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 (65pzo) of the display unit 6 that indicates the defect is determined. In other words, the off-axis image plane calculated by 3-1 in process [6] (
5KPPZ), under one-direction creepage capacity of off-axis image plane (5KPPZ),
TDWU), off-axis image plane over unidirectional tolerance (5T
DWO) to (5KPPZU) = (5KPPZ) + (5T
DWU) (5KPPZO) = (5KPPZ)
-(5TDWO) is obtained. In process [8], the over-unidirectional limit (SKPPZO) of the off-axis image plane calculated in process [7] is checked, and if the ratio is negative, it is set to (5KPPZO) - 0. This is to eliminate negative values and facilitate the arithmetic processing in the determination unit 5. In process [9], from the four off-axis image plane positions (PPZ) measured in four directions, PPZMAX: Maximum value PPZMIN: Minimum value HKNPPZ 2III1 Average value 5APPZ: The difference between the maximum value and the minimum value is determined. In the process [101, the off-axis field change limiter l-(5TDP
Turn on PSA (UND). In process [12J, process [1,1' in 71! ;J, Compare the over one-way limit (5KPPZO) of the off-axis image plane with the average value ()IKNPPZ) calculated previously in process [9]. (5KPP
If the average value (HKNPPZ) is smaller than the average value (HKNPPZ) than
Bit 1'') is set to 1. As a result, when the contents of the determination register described in - are transferred and stored in the display control memory, the LED 65B (OVE
R) lights up. In process [13J, 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) = (5A)IKNZ) is calculated. In process [14], the off-axis image plane difference (5AHKNZ) calculated in process [13] is examined. That is, the sign of the difference (5AHKNZ) between the off-axis image planes is checked. The difference in off-axis image plane (5AHKNZ)! For the value of L,
It is considered that the off-axis image plane is located below the axis 1-image plane. In this case, the off-axis under-distance amount (PPZGU) is (ppzcu) = (5AHKNZ) x 2
+ (5APPZ) is calculated. This off-axis under-under amount (PPZGU) is equivalent to twice the defocus 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 it causes a decrease in contrast. Next, this off-axis underbase (PPZGU) is compared with the off-axis underside limit (5TDPPZU). (5TDPPZU)
If the amount of off-axis under-image (PPZGU) is larger than that, it is possible that there is eccentricity as well as curvature of the image plane toward the under-image side, so it is determined that it is a composite defect of under-image abnormality and eccentricity abnormality.
The corresponding bit of the judgment register (the 5th bit of the judgment register DS1) is set to 1. As a result, when the contents of the determination register are transferred and stored in the display control memory and the display indicating the defect is displayed, the LED 65H (0+H) of the display section 6 indicating the defect is lit. In processing [15], from the four axes at the on-axis image plane position measured in four directions (MTFA), MTFMAXA: Maximum value MTFMINA: Minimum value HKNMTFA: Average value SAMTFA: Maximum value and minimum value. Find the difference between. In process [161], the best axial contrast change limit (STDMMSA) is compared with the difference between the maximum value and the minimum value (SAMTFA) calculated in process [15]. Here, the best on-axis contrast change limiter) (STU
The difference between the maximum and minimum values (SAMTF
If A) is larger, it is determined that there is a coma defect in the on-axis contrast, and the corresponding bit in the determination register (determination register D
4th bit of SO) 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 65G of the display section 6 that indicates the defect in question (
Turn on U+H). 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 image plane on the axis. In this case, the off-axis over amount (PPZGO) is (PPZGO) = (5AHKNZ) x 2 +
(5APPZ) is calculated as 21. This off-axis over amount (ppzco) is equivalent to twice the day focus amount of the off-axis image plane from the average axial image plane (HKNPPM), as in the case of the off-axis under ψ. The larger the amount of overlapping, the more it causes a decrease in contrast. Next, this off-axis over amount (PPZGO) is compared with the off-axis over amount (m pieces) (5TDPPZO). If the off-axis over amount (PPZGO) is larger than the off-axis over side limit (S, TDPPZO), eccentricity is also considered as well as curvature to the over side of the image plane, so the combination of over abnormality and eccentric abnormality is considered. It is determined that it is defective, and the corresponding bit of the determination register (bit 6 [1 of the determination register DSI) is set to 1. As a result, the contents of the determination register are transferred to and stored in the display control memory, and the LED 64B (A-CO
M) lights up. In process [17], the best axial contrast limit (S
TDMINA) and the average value calculated by processing [15] (HK
NMTFA). Here, the average value (HK
If NMTFA) is smaller, it is determined that the on-axis contrast value is insufficient, and the corresponding bit in the determination register (bit 5 [1] in the determination register DSO) is set to 1. This results in
” When the contents of the judgment register 2 are transferred and stored in the display control memory, the LED 6 of the display unit 6, which indicates the defect,
Turn on 4C (A-MTF-LOW). In the process [18], the best on-axis contrast limit (S
TDMINA) and the minimum value (MT
Compare with FMINA). Here, the minimum value (M
If TFMINA) is smaller, it is determined that there is a shortage of image 1 in a part of the axis contrast, and the corresponding bit in the determination register (6th bit of 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 LED64D (A-MTF・PL). Processing [In 19J, four off-axis contrasts at off-axis image plane positions measured in four directions] From (MTFZ), MTFMAXZ: Maximum value MTFMINZ: Minimum value HKNMTFZ: Average value SAMTFZ: Difference between maximum value and minimum value seek. In processing [20J, the best off-axis contrast limit (S
TDMINZ) and processing [average value calculated with 19J (HK
NMTFZ). Here, the average value (H
If KNMTFZ) is smaller, it is determined that the off-axis con i-last value is insufficient, and the corresponding bit in the determination register (3rd pin l-11 of determination register [lS1) is set to 1. As a result, the contents of the determination register 1-1 should indicate that any bit of the display control device DS1 is set to 1. Therefore, if the status yb of all bits of the determination registers DSO and DSL is inspected, the lens to be tested will be
It is possible to know whether each defect is 41 or no. That is, if all bits in the determination registers DSO and DSI are O, the lens 1 to be tested is determined to be non-defective, and the overall good determination correspondence 1/jister (8 vias 1 of determination register DS+]1) of the determination subroutine 51 is performed. Let be 1. As a result, when the contents of the judgment register 2 are transferred and stored in the display control memory, the LED 6 of the display section 6 indicates a non-defective product.
Turn on 2B (Good). -, judgment register DS
If all the O and DSI focuses are inspected and there is even one focus of 1, it means that there is some sort of defect in the lens 1 to be tested that corresponds to the focus. It is determined that the product is defective, and the general defective determination correspondence register (bit 7 of determination register DSI, 1) of the determination subroutine 51 is set to 1. As a result, when the contents of the determination register DSL are transferred to and stored in the display control memory, the LED 65E of the display section 6 which indicates the defect in question (
Z-MTF-LOW). In process [211], the best off-axis contrast change limit (STDMMSZ) is compared with the difference between the maximum value and the minimum value (SAMTFZ) calculated in process [191]. Here, the best off-axis contrast change limit (STOW
MSZ ) is the difference between the maximum and minimum values (SAMTFZ
) is larger, it is determined that the off-axis frame is defective, and the corresponding focus of the determination register (2 pins of the determination register DSI) is determined.
-1-D is set to 1. As a result, the above judgment register D
When the contents of SI are transferred and stored in display control memory, ¥
I LED65D of the display section 6 which indicates the defect (Z-
, COM) lights up. In process [221], a comprehensive judgment is made based on the individual judgments in the judgment subroutine 51, and all the focuses in the judgment registers DSO and DSL are checked. In other words, if there is some kind of defect in the lens to be tested,
By executing each of the processes up to the above process [21J], when the determination register DSO or transfer is stored, the LED 62A (defective) of the display unit 6, which indicates a defective product, is turned on. In process [231], the contents of the determination registers DSO and DSI are stored in the display control memory within the memory. That is, by executing the process [23], 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 section 6. This process is performed for the reason of Handling-1- that the determination registers DSO and DSl are registers for arithmetic processing within the determination unit 5, and are also used in the determination subroutine 52, etc., which will be described later. The determination subroutine 51 executes the process described in item 1-23 1]1 in the following. The test lens 1 is judged based on the contrast measured at the average axial image plane, that is, the test lens l is judged based on the contrast measured at the average axial image plane. 24 is a flowchart of the determination subroutine 52 shown in FIG. 16. Hereinafter, each process (procedure) shown in the same figure will be explained according to the flow. In the process [11], 8 or 12 pieces in predetermined 8 or 12 directions measured at the average axis-L image plane position are
The difference between MTFMXLA: Maximum value MTFMNLA: Minimum value HKNMFLA: Average value SAMTFLA: Maximum weight C and the minimum value is determined from the on-axis contrasts. In Process Fl, [2], Best Axis-1-Contrast Change Limit (STDMMSA), Process [1]
-t=difference between the maximum value calculated by al and the minimum 4f4 (SAMT
FLA). Here, if the difference between the maximum value and the minimum value (SAMTFA) is larger than the change limit (STDMMSA) of the contrast on the best axis, the axial contrast limit (STDMNLA) on the axial contrast defective surface is determined. than the minimum value (MTFM
If NLA) is smaller, then the axis "NLA" is smaller than -
・It is determined that there is a shortage of 1 f in the section, and the corresponding bit in the determination register (6th bit of the determination register DSO) is set to 1. As a result, when the contents of the determination register -1- 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). 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 (MTFZLO to MTFZL7 or MTF
gLO~MTFZLII). Therefore,
When off-axis contrast is measured for 8 directions, the measured value of the 4th direction, that is, the save register (MTFZL3
) to the 8th direction save register (MTFZL?)
Transfer to. After that, the measured value of the seventh direction, that is, the contents of the save register (MTFZL6), is judged as the save register (MTFZL6) of the fourth direction, and the corresponding bit of the judgment register (
3 bits of the judgment register DSO]1) are set to 1. As a result, when the contents of the determination register are transferred and stored in the display control memory, the L of the display section 6, which indicates the defect, is
Turn on ED64A (A-ASU). In process [3], the axial contrast limit (STDMNLA) on the average axial image plane is compared with the average value ()IKNMFLA) calculated in process Ml. Average axis on image plane] - Contrast limit (STDMN
If the average value (HKNMFLA) is smaller than LA), it is determined that the axial contrast value is insufficient, and the corresponding bit of the determination register (5th bit of the determination register DSO) is determined.
Let be 1. - As a result, when the contents of the judgment register 2 are transferred and stored in the display control memory, the LEo 64C (A-MTF-LO
Turn on W). In process [41], the axial contrast limit (STDMNLA) on the average axial image plane is compared with the minimum value (MTFMNLA) calculated in process [11]. Average axis 3)
Transfer to. This measurement value transfer is performed using the following process [1
This is a preparation to simplify the old calculation process in f5
This is a data saving operation because the measured values in the four directions are the data to be transferred to the personal computer unit PC, which will be described later. Furthermore, when off-axis contrast is measured in 12 directions, all the measurement data is used, so the process [5] is not performed and the process directly proceeds to the next process [6]. In process [61], from the measured values of off-axis contrast, the difference between MTFMXLZ: Maximum value MTFMNLZ: Minimum value HKNMFLZ: Average value SAMTFLZ: Maximum value and minimum value is determined. Note that when off-axis contrast is measured in eight directions, each of the above values is obtained from the contents of the save registers (MTFZLO to MTFZL5). In addition, when off-axis contrast is measured in 12 directions, the retraction register (MTF
ZLO~MTFZLII) (7) Find the stored value in - from the contents. In process [7], the off-axis contrast 1ll (fixed value) saved in process [5] is returned to its original value. In other words, when off-axis contrast is measured in 8 directions, the save register (M
The fourth direction that was evacuated to TFZL7)? 1111:j
Transfer the f value to the original save register (MTFZL3) and return to the original state. Now, the 71111 planting at the 8th power level is
Although it is erased by the data saving operation in the process [5], there is no problem because the fourth direction symmetrical to this is secured. Further, when off-axis contrast is measured in 12 directions, there is no need to execute the process [7], and the process immediately moves to the next process [8] after executing the process [6J]. In process [8], the off-axis contrast limit (-STDMNLZ) on the average axis-1-image plane is compared with the minimum value (MTFMNLZ) calculated previously in process [61]. 】・】
Off-axis contrast limit (S
If the minimum value (MTFMNLZ) is smaller than TDMNLZ), the direction of the curvature of field is examined because it may be due to a combination failure of the curvature of the field and eccentricity. Further, the LED 65H (0+H) of the display unit 6, which indicates a defective off-axis contrast limit on the image plane, is turned on at 1.equal axis. In Processing [91], the limit of the average value of off-axis contrast at the image plane (STDMNHHz) and the processing [
6] Compare with the 1L average value (HKNMFLZ) calculated in . If the average value (HKNMFLZ) of the off-axis contrast at the average axis-1-image plane is smaller than the limit (STDMNHHz) of the average value, then
It is determined that the off-axis contrast value is insufficient, and the corresponding bit of the determination register (3 vias +- 11 of the determination register DSI) is determined.
Let be 1. As a result, when the contents of the determination register are transferred and stored in the display control memory, the LED 65E (Z-MTF・LOW) of the display section 6, which indicates the defect,
lights up. In process EIOJ, the best off-axis contrast lasing limit (STDMMSZ) is compared with the difference between the maximum value and minimum value (SAMTFLZ) calculated in process [6]. Here, the change limit of the best off-axis contrast (S
The difference between the maximum and minimum values (SAl
lTFLZ) is larger, off-axis contrast]・
fluctuation light 1, Z) than the minimum value (MTFMNLZ)
If the force is not small, the process immediately moves to process [101]. The direction of field curvature has already been checked by the determination subroutine 51. In other words, (PPZGO) > (ppz
cu), then over one direction, (PPZGO) < (P
PZGU), then you are ru on the other hand. Therefore, if the image plane of the lens to be tested is curved in one direction, the off-axis contrast will be different by 1θ due to the combination of the under and eccentricity. , the corresponding bit of the judgment register (5hi, 1·1] of the judgment register DSL) 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 65G (U+H) of the display section 6, which indicates the defect, is turned on. On the other hand, if the image plane of the test lens 1 is overcurved in one direction, it is determined that the off-axis contrast is abnormal due to the combination of overshoot and eccentricity, and the corresponding bit of the determination register (6 bit 7 l of determination register OS+) is determined.・11) is set to 1. As a result, when the content of the judgment register 1- is transferred and stored in the display control memory, it is judged as normal and the corresponding bit of the r4 constant register (bit 4 11 of the judgment register DSL) is set to 1.
shall be. As a result, when the contents of the determination register -1- are transferred and stored in the display control memory, the LED 65F (Z-HEN) of the display section 6, which indicates the defect, is turned on. Processing [I In II, the judgment registers DSO and D
Inspect all SI focuses. Similar to the process [22] in the judgment subroutine 51, this is to perform a comprehensive judgment based on the individual judgments in the judgment subroutine 52, and all the cases of each person in the judgment registers DSO and DSI are processed. Inspect the bits. That is, if all bits of the judgment registers DSO and DSI are O,
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 it is determined in -1- and the contents of the sister are transferred and stored in the display control memory, the LED 62B (good) of the display section 6, which indicates a non-defective product, is turned on. On the other hand, if all bits of the judgment registers DSO and [lSI are inspected and even one l is in focus, it means that the tested lens l has some kind of defect corresponding to that bit. 1 is determined to be a defective product, the tested lens 1 is determined to be a defective product, and the general defective determination corresponding register (determination register O8
The 7 bits []) of 1 are set to 1. As a result, when the contents of the determination register -I- are transferred and stored in the display control memory, the LED 62A of the display unit 6 (which indicates a defective product)
(defective) lights up. In process [121], the contents of the determination registers DSO and DSI are stored in the display control memory in the memory. That is, by executing the process [12], 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 [231] of the determination subroutine 51 described above. The determination subroutine 52 executes the processes in Section 12 1-1 below in the order of description. That is, the display control memory stores the contents of the above-mentioned determination register nso and DSI in which the determination result by the determination unit 5 is temporarily stored. Each LED of the display panel 61 corresponds to the contents of the control memory in Table 71, that is, each bit of the determination register DSO and mouth S+ in the determination unit 5, and the state of each bit (0 or 1). The configuration is such that blinking is controlled in response to. In other words, each L
The EDs are turned off when the state of the corresponding bit is 0, and turned on when the state is 1. The correspondence between each LED and each bit of the judgment register DSO and O3+, that is, which LED corresponds to the judgment register DSO
As to which bit of the word St and which bit of the mouth St corresponds to will be explained in each case in the description of the determination subroutines 51 and 52, the description thereof will be omitted here. Next, specific display contents by each LED will be explained. The LEDs 62A and 62B for comprehensive judgment indicate that 62A is a defective product (that is, various judgment criteria). A light-emitting tie auto (
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 (63A, 63B, 64A, 64B meeting 64C, 64
D-65A/65B/65C/65D-65E/65F
・65Gφ65H) is placed at a predetermined position as shown in Figure 26. Incidentally, in the display panel 61, the 1rf of the lens tester LT, the source switch 66, the start switch for the measurement operation, etc. are also arranged. (Function) Each LED arranged on the display panel 61 is blink-controlled by the display control memory provided in the microcomputer, which together with the control unit 4 constitutes the determination unit 5, as explained in the above-mentioned determination unit 50. be done. In this case, each inspection da- 11-
1 LED is always lit) and 62B
is lit when the lens 1 to be tested is a good product (when it satisfies all of the various criteria). Each judgment section 1 "The other LEDs are 63A, 63B is mechanical back focus defect, and 64A to 64D are lens axis."
One is a defect in the center, and 65A to 65H indicate a defect outside the axis of the lens, that is, a defect in the peripheral portion, and the lighting indicates the defect. Hereinafter, the display (lighting) by each LED of each determination unit [1 will be individually explained. 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 pack focus excessive defect (fb
Lights up when people). 63B is due to mechanical focus bank malfunction (fb
Lights up when (small). 64A lights up when there is an axial astral defect, that is, a defect due to an abnormal change in the axial peak (A-ASU). 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 axis-frame failure, that is, a failure due to an abnormal change in the best on-axis contrast (A-CON). Possible causes of this defect include eccentricity of the constituent lenses constituting the lens to be tested 1 and poor polishing. 64C lights up when there is a defect (A-MTFLO) in which the contrast is insufficient, that is, the average axis]-MTF value is too small. The cause of this defect is considered to be poor polishing of the constituent lenses constituting the test lens 1. 64D lights up when the - part of the 1-contrast is defective (A-MTFPL). Among the defects shown by 64G, the Iff is lighter as the defects become worse. Therefore, if 64C lights up, 64D also lights up when the point average off-axis contrast value is too small (Z-MTFLO). Possible causes of this defect include eccentricity of the constituent lenses that make up the lens to be tested, 1, and alignment defects such as changes in spacing. 65G lights up when the - part of the off-axis contrast is small and there is an under-contrast defect (U+H).The cause of this defect is that the lens under test It is thought that there is a misalignment of the constituent lenses constituting 1. 65H lights up when there is a defect (0+)l) when the off-axis contrast is small in the - part and is over defective.The causes of this defect are as follows. It is possible that there is a misalignment of the constituent lenses constituting the test lens 1.
In addition to determining whether the product is defective, it is also possible to classify the cause of the defect, which improves the efficiency of inspection work. 65A lights up when there is an under-defect, that is, a defect in which the off-axis image surface is too close to the lens side than the axial image surface (UND). 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-fault, that is, a fault where the off-axis image plane is farther from the lens side than the 1-1 image plane (0VER). The cause of this defect may be poor spacing or large eccentricity of the lenses constituting the lens 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). The cause of this defect is considered to be eccentricity of the constituent lenses that make up the lens 1 to be tested. 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). The cause of this defect is that the ωF of the constituent lenses that make up the test lens
Bad calendar, brave eccentricity gets 2. 65E is insufficient value of ml + outer contrast], that is, 1
;I can only do 4 things. [Systemization of Lens Tester LT 1] In this embodiment, a lens tester system is constructed by connecting a personal computer (PC) to the lens tester LT as shown in the 7526 diagram, and information (measurement and judgment data) from the lens tester LT is configured. The addition of [allows processing]. (Configuration) The personal computer section PC is a personal computer, and is composed of a computer 71, 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 by a data bus DB to the microcomputer that constitutes the control section 4 and judgment section 5 of the lens tester LT, and the measured values from the lens tester LT and commands from the personal computer section PC are passed on to the microcomputer. There is. (Function) Then, in the personal computer section PC, data manually inputted from the lens tester LT can be integrated and processed to create the following data useful for defect countermeasures, quality control, etc. for the tested lens l. The data can also be printed out by 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 allows the measurement data to be visualized, allowing for more detailed image plane conditions that cannot be seen on the display unit 6 of the Lenzotes LT.
This can be understood in 1. FIG. 27 is an example of graphical display of measurement data on the CRT display 73. The graphical display is - - There are four types of graphs on the screen (the graph on the left of the screen is called G1, the graph on the bottom left of the screen is called 62, the graph on the top right of the screen is called 63, and the graph on the bottom right of the screen is called 04). These are displayed simultaneously and 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... Indicated by G4. In addition,
Similar to the graph G1, the designed image plane position is also displayed. Graph G3 is a graph of the on-axis contrast for each direction at the average on-axis image plane position measured in the contrast measurement subroutine 44. The standard value for determining pass/fail for the tested lens is shown by the dotted chain line. Therefore, in the graph 3G, if the contrast shown by the solid line exceeds the standard value for determining pass/fail, the product is good in terms of axis contrast. Graph G4 is a graph of the off-axis contrast for each direction at the average axial image plane position measured in the contrast measurement subroutine 44, and the off-axis contrast is shown as a solid line. , and the reference value 1 for determining the quality of the lens to be tested is also shown by the - dotted chain line.Therefore, in the graph 4G, similar to the graph 3G, the contrast shown by the solid line is the reference value for determining the quality. If it exceeds the off-axis contrast, it is determined that the lens is of good quality, and the vertical axis represents the contrast, and the horizontal axis represents the orientation in each graph.However, the 11 scales on the horizontal axis are the graph Gl
, G2, the four directions in the contrast measurement subroutine 43 are shown in graph G3. G4 represents 8 or 12 directions in the contrast measurement subroutine 44. Next, each graph will be explained individually. Graph Gl shows the peak value of axial contrast in each direction measured in the contrast measurement subroutine 43 and its image plane position M (best axial image plane position),
The peak value of 111 fixed point contrast) is shown by a solid line, and its position (best image plane position) is shown by a dashed line. In addition,
The design image plane position is also displayed (Jl) to make it easier to understand changes in the image plane state of the lens under test. Graph G2 shows the off-axis position in each direction measured in the contrast measurement subroutine 43. The contrast peak value and its image plane position (best off-axis image plane position) are shown by a solid line, and the contrast peak value at each off-axis measurement point is shown by a solid line, and its position (best image plane position) is shown by a dashed line. ” - From the graph display, it is possible to read the failure of the optical characteristics of the lens to be tested and its cause, for example, as shown below. (1) In graph G2, at each measurement point as shown in Figure 28, When the graph of the off-axis image plane position intersects with the construction 1 image plane position, it can be seen that the image plane is tilted as shown in Fig. 30(a). This condition occurs when the constituent lenses of the test lens L are decentered. (2) As shown in Figure 29, in the graph Gl, the image plane position on the axis of each measurement point is the design image plane. It is located near location A.1,
In graph G2, if the graph of the off-axis image plane position of each measurement point is approximately parallel to the design image plane position on either the upper or lower side (the lower side in the figure, that is, the side approaching the lens), the 30th
It can be seen that the image plane is curved (curved to the under side in the figure) as shown in Figure (b). 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 failure analysis method according to the present invention, the condition of the image plane can be detected by quantitatively measuring the contrast of the chart image, and the quality of the test lens can be judged with +1 f ability, and the condition of the image plane can be detected from the condition of the image plane. The cause of the failure can be analyzed and useful information can be obtained for quality control, process control, readjustment, etc. In other words, it contributes to streamlining not only the inspection process but also all lens manufacturing processes.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a schematic configuration of a lens tester using the lens failure analysis method according to the present invention, FIG. 2 is a plan view of the lens mount, FIG.
The figure 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, Fig. 10 is a cross-sectional view taken along the line X-X, Fig. 11 is a cross-sectional view of Fig. 9, and Fig. 1
FIG. 2 is a block diagram of the arithmetic circuit, and FIG. 13 is a diagram illustrating the estimation of the characteristic MTF of the lens to be tested from the MTF value at one spatial frequency. l...Test lens 2...Optical system 3...
Contrast measurement section 31... CCD sensor section 32... Calculation section 4... Control section 5... Judgment section 6...
Display section 10...lens mount

Claims (1)

[Claims] This method measures the contrast of the chart image formed by the lens under test and analyzes defects in the lens based on the measured value.A grid-like chart with a predetermined pitch is transmitted through the lens under test from on-axis and off-axis. The contrast of the on-axis and off-axis grid chart images formed by the test lens is measured at multiple locations in the optical axis direction of the on-axis light at multiple off-axis positions. Then, from the relative position in the optical axis direction of the on-axis light where these contrast measurement values have the maximum value, the inclination/inclination of the image plane formed by the test lens is determined.
The quality of the lens to be tested is determined by determining the curvature and comparing the amount of inclination/curvature of the image plane with predetermined criteria, and also determines the inclination/curvature of the image plane in response to predetermined defective factors. A lens defect analysis method characterized by analyzing the cause of the defect in the lens to be tested from the cause-and-effect relationship.