JPH0262931A - Searching method for optimum image plane position of lens - Google Patents

Abstract

PURPOSE:To search a peak position among contrasts with high accuracy by moving a detecting means stepwise, calculating the peak position among many contrasts obtained by a measuring means, and repeating the calculation several times and finding a mean position. CONSTITUTION:Light LA which is transmitted through a chart CA with specific grating pitch from on the optical axis and light LZ which is transmitted through a chart CZ from the external of the axis are entered into a lens 1 to be inspected. The brightness of the image is converted by CCD sensors 31A and 31Z into electric signals, and arithmetic circuits 32A and 32Z calculate the contrasts of respective chart images. A control part 4 moves sensors 31A and 31Z in the direction of the optical axis and rotates the lens 1 around the optical axis to measure contrasts at plural positions in the optical-axis direction as to plural specific external positions of axis, thereby fixing the sensors 31A and 31Z at the mean positions on the optical axis where the maximum contrast is obtained. At this position, the lens 1 is rotated and the contrast of the image of the chart CZ is measured. Thus, the best image plane position is found.

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for detecting the best image plane position of a lens, and more particularly, to detecting a contrast peak that changes in accordance with defocus in a lens to be inspected. [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, and 2' is a lamp 1'.
3' is a transmission type chart, 4' is a test lens, and 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 convergence and pitch) of this pattern corresponds to the resolution, and for example, 100 wood/■■ from the minimum pitch line array that can be seen separately in the chart image projected on the projection plate 5'. It is evaluated for its resolution. 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 is enlarged and projected by the test lens 4' onto a projection plate 5' placed at a position 40 to 50 times the focal length of the test lens 4'. At this time, if the incident angle θ2 of the illumination light from the condenser lens 2' to the chart 3' is smaller than the incident angle OI of the light flux of the chart image by the test lens 4', as shown in the figure, the test lens 4' As a result, the incident angle θ2 must be sufficiently large. The operator finely adjusts the position of the test lens 4' in the optical axis direction to focus the center of the chart image on the projection plate 5', and then the chart image projected onto the projection plate 5'. Visually check whether the chart at a predetermined pitch at a predetermined position within the chart image is separated (in other words, whether the chart image has a predetermined resolution at a predetermined position within the chart image), and inspect the quality of the lens to be tested. . However, such projection tests have poor workability because they must be performed in a dark room.
If the focal length of the lens to be tested is long, a large darkroom is required, which requires a large amount of equipment cost.Furthermore, the condenser lens needs to be large in diameter and bright, and a highly skilled technician is required to visually check the chart image. There were a number of problems, including the fact that even operators could not perform stable inspections with a certain level of accuracy. For this reason, the applicant first developed a lens holder that rotatably holds the lens to be tested, and a lattice chart of a predetermined pitch from on-axis and off-axis to the lens to be tested held in the lens holder. An optical system that allows the transmitted light to enter, and a chart image detected by a detection means that is disposed in front of each optical path of on-axis and off-axis light by the optical system and that is movable and driveable in the optical axis direction of the lens to be tested. a contrast measuring means for calculating contrast based on the image of the lens to be tested; A lens tester comprising a determination section that determines the quality of a lens to be tested by comparing the contrast measured by a measuring means with a predetermined criterion, and a display section that displays the determination result by the determination section. Proposed. [Question 11 to be solved by the invention] However, in order to quantitatively test a test lens with high precision in the lens tester as described above, it is necessary to determine the peak position of contrast for defocus in the test lens, that is, the best image plane. It is necessary to determine the position, and in order to comprehensively determine the quality of the lens to be tested by the determining section, it is necessary to determine the best image plane position as well. [Object of the Invention] This invention was made in view of the above background, and it is an object of the present invention to detect the best image plane position of an optical lens, that is, the contrast peak position for defocus in the optical lens, with high precision and efficiency. The purpose of this invention is to provide the best possible method for detecting the image plane position of a lens. [Means for Solving the Problems] Therefore, the method for detecting the best image plane position of a lens according to the present invention includes a step-moveable part that moves a chart image of a lattice chart formed by a lens to be tested in the optical axis direction of the lens to be tested. A lens tester that detects by a detection means and continuously obtains a large number of contrasts of images of the lattice chart based on the chart image detection result by the detection means by a contrast measurement means that operates in conjunction with the step movement of the detection means, The above-mentioned detection means is moved by a predetermined amount of steps while operating the detection means, and a large number of contrasts are continuously obtained from the above-mentioned contrast measurement means as a result of this, and the peak position is determined by comparing the magnitudes of these contrasts as the contrast for the defocus of the subject lens. At the same time, the step movement amount of the detection means is decreased and updated according to the peak position, and the contrast for the defocus is measured and the peak position is calculated multiple times, and the multiple peak positions obtained thereby are The average is taken as the best image plane position l. Note that measuring the contrast of the image of the lattice chart formed by the lens under test means that the lattice of the lattice chart has a predetermined pitch, so the MTF of the lens under test is measured at the spatial frequency of the chart pitch. It turns out. 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 Function
on, abbreviated as MTF). MTF is defined as, at a certain spatial frequency,
It can be thought of as a contrast deterioration function, and is used to indicate the imaging characteristics of an optical system. When the contrast m is measured using a sine wave grating, the maximum light intensity of the optical image is I□1. If the minimum light amount is I sin, then 1,, lI +1□. is defined as Maximum amount of light transmitted through the chart that changes sinusoidally and is input to the lens to be tested 1. , Minimum light intensity■,,,. Therefore, the contrast of the input image to the test lens can be calculated using the above equation (2), but the minimum light ir-+- of the input light can be considered to be 0 (zero), so the defining equation of MTF is The contrast of the input image in equation (1) is l. Therefore, if the contrast of the sine wave chart image (output image) formed by the test lens is measured, this will be the MTF value of the test lens at the spatial frequency of the chart pitch. The MTF is a function unique to the optical system, and when expressed on orthogonal coordinates with the contrast deterioration rate on the vertical axis and the spatial frequency on the horizontal axis, it can be expressed, for example, as shown in FIG. 32. Optical systems such as camera lenses are M at the time of optical design.
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 (n-tree ZIl
By examining the MTF value in (2), it is possible to predict the MTF of the lens to be tested. That is, for example, the 33rd
When the solid line shown in the figure is the ideal (design) MTF curve and the contrast at a spatial frequency of 1 line/am is a, the contrast of the chart image of the same spatial frequency formed by the test lens is X. In this case, the MT of the lens to be tested
It can be inferred that F is like an imaginary line. In addition, by examining the position in the optical axis direction (i.e., the imaging position) that exhibits the maximum contrast value at multiple locations on-axis and off-axis, we can determine the tilt of the imaging surface as shown in Figure 30(a). or,
It is possible to detect the curvature of the imaging plane as shown in FIG. Therefore, if the judgment reference value and the judgment reference amount are appropriately set based on the allowable value of the contrast of the test lens at a predetermined spatial frequency and the allowable amount of curvature, inclination, 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. Also, from the occurrence of curvature, inclination 9, etc. of the image formation, 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. Note that if a rectangular wave chart is used instead of a sine wave chart, the measured spatial frequency will include harmonics and jII number of spatial frequencies will be mixed.
If the MTF of the lens to be tested is known, such as during mass production, it is sufficient to set the judgment criteria in consideration of harmonics.
Conversely, it has the effect of being able to detect the image plane position 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 [Embodiments of the Invention] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a block diagram schematically showing the configuration of a lens tester to which a preferred embodiment of the method for detecting the best image plane position of a lens according to the present invention is applied. "Overview of Lens Tester LT" (Configuration) Lens Tester LT consists of a lens mount section 10. The contrast measuring section 31 is constituted by an optical system 2, a sensor section 31, and an arithmetic circuit 32, and an M control M41 determining section 5 and a display section 6 serve as operation control means. Note that 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. (Function) The lens mount section 10 holds the test lens 1 at a predetermined position so as to be rotatably driven around the optical axis of the test lens 1. The optical system 2 extends along the optical axis of the test lens l held by the lens mount part IO. Light transmitted from the axis through chart CA with the specified lattice pitch (
On-axis light LA) is made incident, and light (on-axis light LZ) that has passed through a chart CZ with a predetermined lattice pitch from off-axis having a predetermined angle with the optical axis is made incident. In the contrast measuring section 3, a chart C is formed by the on-axis and off-axis lights LA-LZ from the optical system 2 passing through the test lens l held by the lens mount section IO.
Each CCD sensor (on-axis sensor 31A and off-axis sensor 31Z) of the CCD sensor unit 31 scans the A-CZ image in the pitch direction of the chart image, converts the brightness of the chart image into an electrical signal, and converts the brightness of the chart image into an electrical signal. The signals are computed by the arithmetic circuit 32 (on-axis arithmetic circuit 32A and off-axis arithmetic circuit 32B) to calculate (that is, measure) the contrast of the on-axis and off-axis chart images. The control unit 4 controls each CCD sensor 31 of the CCD sensor unit 31.
A.31Z is moved in the optical axis direction of the test lens 1 to measure the contrast of the on-axis and off-axis chart images at multiple locations along the optical axis direction of the test lens l, and the lens mount section By driving lO, the test lens l is rotated around its optical axis to change the off-axis measurement point, and the pitch direction of the chart image relative to the test lens l on the axis is changed. The contrast of the chart image is measured at multiple predetermined off-axis positions at multiple locations in the optical axis direction of the detection lens L, and further, from the on-axis contrast measurement results obtained from the above measurements, the contrast at each measurement point is determined. The on-axis and off-axis CCD sensors 31A and 312 are fixed at the average position on the optical axis where the contrast at each measurement point is the maximum value. The off-axis sensor 31Z is also fixed at a distance from the tested lens l that is equal to the average distance between the lens l and the on-axis sensor 31A), and the chart image at each off-axis measurement point is obtained by rotating the tested lens l. Each CCD sensor 31A of the sensor section 31 of the contrast measuring section 3 measures the contrast of
31Z, the measurement of contrast, and the driving of the lens mount section 10 (rotation of the lens 1 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 also compares the contrast value of the chart image obtained by the contrast measurement unit 3 with a predetermined determination reference value. The amount of mutual deviation in the optical axis direction of each off-axis measurement point is compared with a predetermined determination reference amount, and if it exceeds one determination criterion, it is judged as defective and the quality of the lens 1 to be tested is determined. Furthermore, if the lens to be tested is defective, a predetermined value is 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 provided 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 10.
It is a sectional view taken along ■-■. In the figure, 100 is a chassis of the lens tester LT (not shown in FIG. 2), and 11 is a mount on which the tested lens 1 is positioned and held. 101 is a chassis 1 that rotatably supports the mount 11;
00 is a fixed bearing boss, 15 is a locking mechanism for fixing the lens 1 to be tested on the mount 11, and 17 is a locking mechanism 1.
An air cylinder 5 drives the mount 11, and a DC motor 18 rotates the mount 11. The mount 11 forms an opening for passage of inspection light in the center of a disk-shaped substrate 12, and also has a lens mounting section 13 that can position and place the lens l to be tested on the upper surface of the substrate 12.
The bearing boss 101 has a substantially disk-shaped appearance with a fitting portion 14 for fitting the bearing boss 101 formed on the lower surface of the bearing boss 101, respectively. 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. A locking mechanism 15 for fixing to the mounting portion 13 is also provided. The fitting portion 14 is fitted into a bearing boss 101 fixed to the chassis 100 via a bearing 102, and is rotatably installed in the chassis 100. The lens mounting portion 13 has an upper surface serving as a reference surface 13A, and is also provided with a positioning surface (not shown) in the front-back and left-right directions. When the lenses (flanges for attaching the lens to the camera body) are placed in contact with each other, the vertical, front, back, left and right positions of the lens to be tested relative to the mount 11 are 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 mount 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 the idle gear 16, and the idle gear 16 also meshes with the gear 12A on the outer periphery of the substrate 12 of the mount 11, and the mount 11 is rotated by the rotation of the DC motor 18.
or rotationally driven. In the locking mechanism 15, a link plate 152 is rotatably supported on the side surface of a boss 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 lock plate 153 is fitted into a notch 153A of the lock plate 153, and the lock plate 153 is configured to rotate as the link plate 152 rotates. The lock plate 153 has a plate shape with a predetermined thickness, and has a notch 153A open at its upper end and a protruding claw 153B at one end. It is rotatably supported by a post 151 on the lower end side. Further, the link plate 152 and the lock plate 153 are connected by a spring 154 on the outside of their respective pivot positions (on the side opposite to the lens mounting section 13), and the spring 154 or the lock plate 153 is connected to each other by a spring 154. The claw 153B is pulled against the link plate 152 in a direction that causes the lens mounting portion 13 to rotate. This rotation of the lock plate 153 is caused by the claw 153B being the lens F! i1. It is regulated by coming into contact with the upper surface (reference surface 13A) of the placement part 13, but at this time the claw 153B is in contact with the reference surface 13A.
The force for pressing 3A is set to a predetermined pressing force sufficient to hold the lens 1 to be tested. The air cylinder 17 is installed on the chassis 100 outside the link plate 152 with the position of the rod 17A corresponding to the upper side of the pivot point of the link plate 152, and the air cylinder 17 is driven to extend the rod 17A. When the rod 17A is
Press the upper end of 52 and rotate it (rotate so that the upper end moves toward the lens mounting section 13 and the lower end moves toward the side opposite to the lens storage section 13), and lock plate 15 via the bin 152A.
3 in the direction in which the claw 153B moves away from the lens a holder 13 (indicated by an arrow in the figure). Although the air cylinder 17 in Figure 2 is only shown for one lock mechanism 15, it may be arranged similarly for the other lock mechanism 15, or for both lock mechanisms 15.
It is sufficient if they are connected by a link mechanism or the like so that they operate synchronously. (Function) Then, the air cylinder 17 is driven to lock the lock plate 1.
When the claw 153B of 53 is rotated in the direction away from the lens storage section 13, the reference surface 13A of the lens storage section 13 is rotated.
It becomes possible to place (or remove) the lens 1 to be tested on top. In this state, position the test lens 1 on the reference plane 13A! Placed. Driving the air cylinder 17 in the opposite direction, the link plate 1
When the pressure on the lens 52 is released, the lock plate 153 rotates due to the tensile force of the spring 154, and the claw 153B presses the flange IA of the test lens l onto the lens mounting 1ffila, thereby placing the test lens l on the reference surface 13A. (ie, on the mount 11). Furthermore, by rotating the DC motor 18 to drive the mount 11, the lens l to be tested fixed on the mount 11 can be rotated about its tip axis.
Moreover, it can be stopped at any position (angle). The drive control of the air cylinder 17 and the DC motor 18 is performed by a control section 4, which will be described later. "Optical System 2" (Configuration) As shown in FIG. 1, the optical system 2 includes a light source section 21 that forms two light beams, axial light and off-axis light, and a light source section 21 that forms two light beams, axial light and off-axis light, and each light beam from the light source section. Each chart CA-C2 is a transmission grating with a predetermined pitch arranged at a transmitting position, and each light flux (on-axis light LA and off-axis light LZ) passes through the chart CA-CZ and the test lens l. Mirrors 22 and 2 that reflect and refract the optical path and guide it to a contrast measuring section 3, which will be described later.
3. It is composed of collimator lenses 24 arranged on each light beam optical path. As shown in FIG. 4, the light source unit 21 includes a halogen lamp 211 as a light source, and a halogen lamp 2 as a light source.
Two filters 212 and 213, a condenser lens 214, a diffuser plate 215, an on-axis fixed half mirror 216, and an off-axis movable mirror 217 are arranged in the order described above to adjust the light from 11 to a predetermined spectral characteristic. It is configured. A parabolic reflecting plate 211A is provided on the back side of the halogen lamp 211 (the side opposite to the light beam emission side), and focuses the light from the halogen lamp 211 at a predetermined position (indicated by f in the figure). It looks like this. Two filters, an infrared absorption filter 212 and a color correction filter 213, are placed in front of the optical path from the focal 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 serves as an angle adjustment part and is also movable back and forth in a direction parallel to the light beam from the halogen lamp 211, and adjusts the off-axis light relative to the optical axis of the test lens l. The angle can be adjusted. Separate charts CA-CZ or chassis 10 are placed in front of the test lens l on the optical path of the on-axis and off-axis lights LA-LZ emitted from the light source section 21 (that is, on the light source section 21 side of the mount 11).
It is fixed at 0. As shown in Fig. 6, the charts CA-CZ are arranged at a predetermined pitch (P
) is a rectangular wave grating formed by vaporizing a plurality of light-opaque line parts or ROMs. Then, the position where the axial light LA is transmitted (i.e., the lens to be tested l
On the optical axis of ), P = 1/20 ■ On-axis chart C of the table
At the position where the off-axis light LZ is transmitted, P = 1/10
Off-axis charts CZ of s+e are arranged respectively. In addition, the arrangement direction of each chart CA-CZ is the pitch direction (direction perpendicular to the marked line) of the off-axis chart CZ or the direction radial from the center of the test lens l, and the arrangement direction of the on-axis chart CA is It is arranged in the same direction as this off-axis chart CZ. The mirrors 22 and 23 fix the on-axis mirror 22 at a predetermined position on the optical path extension of the on-axis light LA via the on-axis chart CA and the test lens l, and also fix the on-axis mirror 22 at a predetermined position on the optical path extension of the on-axis light LA via the on-axis chart CA and the test lens l. The off-axis mirror 23 is arranged at a predetermined position on the optical path extension of the off-axis light LZ. The axial mirror 22 transmits axial light L along the optical axis of the test lens L.
On-axis sensor 31A of the contrast measuring section 3, which will be described later.
The light beam is fixedly installed at a predetermined position on the optical axis of the lens 1 to be tested at an angle of 45° with respect to the optical axis of the lens 1 to be tested so as to reflect at right angles toward the lens 1 . As shown in FIGS. 7 and 8, the off-axis mirror 23 is attached to a guide rail 231 fixed to the chassis 100 via a slide base 232 and a mirror holder 233 to determine the distance and installation angle from the optical axis of the lens l to be tested. This is what is installed as I can adjust it. 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 to the guide rail 231 on its lower surface, and is slidably moved 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 holter 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 holter 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. A cylindrical mounting bar 23A or its end face is adhesively fixed to the back surface of the off-axis mirror 23, and when the mounting bar 23A is fitted into the mounting hole 233B of the mirror holder 233, the mounting bar 23A is Two set screws 233
Tighten mirror holder 2 from the orthogonal direction with C.
An off-axis mirror 23 is fixed to 33. With this configuration, the off-axis mirror 23 can be fixed without being distorted. In FIGS. 7 and 8, the axis of the mirror 23 is at an angle perpendicular to the optical axis direction, but in reality it is installed at a predetermined angle as shown in FIG. 1TJ1. The collimator lens 24 is connected to the chassis 100 on an optical path that is refracted by the on-axis mirror 22 and the off-axis mirror 23 and goes toward the contrast measuring section 3 via a unit base 313 of a sensor section 31 of the contrast measuring section 3, which will be described later. Fixed and placed. (Function) The light source section 21 converts the light from the halogen lamp 211 into an infrared absorption filter 212 and a color correction filter 213.
As a result, the light has a predetermined spectral characteristic as shown in FII(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 represents the wavelength, and the vertical axis represents the wavelength. It is emissivity or transmittance. Explain each graph. (a) shows the emission spectral characteristics of the halogen lamp 211 alone. (b) is the transmission spectral characteristic of the color correction filter 212 alone, and the color correction filter 212 has a center transmission wavelength of 460
nm. (c) is the transmission spectral characteristic of the infrared absorption filter 213 alone, and has a 50% cut wavelength of 7500 m. (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 light-receiving spectral characteristics of 31Z (FIG. 5(e)), the spectral characteristics substantially match the visual sensitivity. The light processed to have such spectral characteristics is diffused by a diffusion plate 215 to blur the filament image of the halogen lamp 211, and approximately 50% of the light is converted into axial light LA by an axial fixed half mirror 216. 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 217, and becomes off-axis light LZ. As described above, the off-axis movable mirror 217 can move back and forth in the direction parallel to the light beam, and can change and adjust the angle of the off-axis light LZ with respect to the optical axis by changing and adjusting the angle.
The off-axis measurement position can be changed and it can be adapted to the type of lens l to be tested. On-axis and off-axis light fluxes LA and LZ from the light source section 21 are on-axis and off-axis light beams that have passed through the test lens 1, which are transmitted through the on-axis chart CA and the off-axis chart CZ, respectively, and enter the test lens l. The light beams LA-LZ are reflected by an on-axis mirror 22 and an off-axis mirror 23, respectively, and their imaging positions are shortened by a collimator lens 24, and then enter a contrast measuring section 3, which will be described later. Note that the movement and rotation of the off-axis mirror 23 is performed by the light source unit 2 described above.
When the angle of the off-axis light LZ with respect to the optical axis is changed by adjusting the off-axis movable mirror 217 in step 1, the off-axis light LZ
This adjustment is made so that the light is incident on the sensor 31Z of the contrast measuring section 3. The following margin is ``Contrast Measuring Unit 3'' (Configuration) The Contrast Measuring Unit 3 has a CCD sensor 31A-31 on each of the optical paths of the two-dimensional LA and off-axis light LZ.
The sensor section 31 includes a sensor section 31 in which Z is arranged, and a calculation section 32 that processes two on-axis and off-axis signals from the sensor section 31. The sensor section 31 includes on-axis and off-axis CCD sensors 31A.
312 is configured to be movable in the direction of the light beam, but its configuration is the same on-axis and off-axis, and the explanation on the outside of the axis will be omitted by explaining the on-axis side. The arithmetic unit 32 includes an arithmetic circuit 32A that arithmetic processes the above-axis signal from the CCD sensor 31A of the sensor unit 31, and an arithmetic circuit 32A that processes the on-axis signal from the CCD sensor 312 of the sensor unit 31;
It is composed of an rA arithmetic circuit 32Z that performs A arithmetic processing. As with the second sensor section 31, its configuration is rotary on the axis and off-axis, and explanation 151 on the outside of the axis will be omitted by explaining the second side of the axis. The sensor section 31 is introduced into the contrast measuring section 3 by the optical system 2, as shown in FIG. A CCD sensor 31A that receives the axial light LA, and a sensor board 311 that holds the CCD sensor 31A. Slide base 312 to which the sensor board 311 is fixed
1 etc. are arranged in a predetermined positional relationship on the unit base 313 to form an integrated unit. Two slide shafts 314A of linear bearings 314 are fixed to the unit base 313 in 11 rows with the optical path (optical axis) of the binary LA. Two slide pieces 314B are slidably fitted to each of the slide shafts 314A. The slide base 312 is installed on the unit base 313 by fitting and fixing each slide piece 314B to the lower surface thereof, and is movable in the optical path direction of the axial light LA. In addition, an acid screw 315 is fixed approximately at the center of the lower surface,
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 dual-light LA incident side.
317 are screwed together. The sensor board 311 is an electric circuit board that detects (measures) the optical end of the image of the axial char (CA) caused by the axial light LA that has passed through the test lens L as an analog signal.
A CCD sensor 31A that detects the light A and outputs a 'ton Qi Shinso' corresponding to the amount of light, and the CCD sensor 31 (not shown).
It is composed of a drive circuit A and peripheral circuits such as a sample & hold circuit. The CCD sensor 31A is a line sensor in which pixels are arranged in a line, and is fixed to the front side of the sensor board 311, but the light receiving surface is perpendicular to the axial light LA and the line direction is 11 on the axial chart CA. The slide base 312 is vertically fixed to the slide base 312 so as to match the pitch direction of the slide base 312 . That is, it is provided in front of the sensor port 311 with its pixel arrangement direction perpendicular to the lattice direction of the image of the axial char (CA) produced by the axial light LA. Note that the collimator lens 24 of the optical system 2 described above is fixed to the front end of the unit base 313. The arithmetic circuit 32A is configured as shown in the block diagram shown in FIG.
- Processing the sensing signal 30 of the optical image of the chart CA,
Outputs the contrast of the CA image. In other words, in this arithmetic circuit 32A, the CCD sensor 31A
is connected to the bypass filter 321 and the integration circuit 322 via the aforementioned sample and hold circuit (not shown), and the bypass filter 321 is connected to the absolute value circuit 323.
connected to. The absolute value circuit 323 is the integral circuit 3
24, and the integrating circuit 324 is connected to a sample & hold circuit 325. Furthermore, one of the integrating circuits 32
2 is connected to the sample & hold circuit 326,
These sample & bold circuits 325 and 326 are both connected to a division circuit 327. (Function) In the sensor section 31, the slat base 312 slides along the slide shaft 314A by the rotation of the pulse motor 316. That is, the CCD sensor 31A is driven to move in the optical axis direction of the axial light LA. The arithmetic circuit 32A uses the CCD-t! of the sensor section 31! 7s3
The optical image signal so sent from 1A is decomposed into an alternating current component and a direct current component, and both of them are integrated for a predetermined period of time, and the ratio of the 1 minute value of these alternating current components and ItcIiJ & min is calculated from the tested lens! Output as contrast. The bypass filter 321 receives the optical image. Take out the AC component inside. The absolute value circuit 323 converts the absolute value of the AC component by the bypass filter Lt9321, that is, the negative AC component, into iE.
Outputs I which is rectified to the side. The integrating circuit 324 integrates the absolute value sent from the absolute value circuit 323 over a predetermined time. That is, the integrating circuit 324 integrates the alternating current component within the optical image signal 50. On the other hand, one integrating circuit 322 integrates the optical image signal So sent from the CCD sensor 31A of the sensor section 31 as it is for a predetermined time.
Then, the DC component of the optical image signal SQ is integrated. Note that each of the integration circuits 322-324 is reset by a reset signal To, and its integration time is controlled by an integration signal 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 hold circuit 326 is connected to the integrator circuit 32.
The integral value of 2 is sampled and sent to the division circuit 327. The sampling timing is controlled by the sample signal T2. The division circuit 327 receives the optical image signal So from the integration circuit 324.
The integration circuit 322 divides the integral of the AC component i by the integral value of the DC component of the optical image signal So by the integrating circuit 322, and outputs the result of the division as the contrast of the lens l to be tested. The optical image signal So is a rectangular wave signal because the axis cA is a rectangular grating (the rectangular wave signal includes a DC component), and is converted into a Fourier zf. For example, the above rectangular wave signal can be expressed as a combination of several sine waves having different frequencies. Therefore, the above calculation output from the calculation circuit 32A is
The contrast will be explained by replacing the optical image signal So with the sine wave signal Sl shown in FIG. In the figure, a is the maximum value of the sine wave signal S1, that is, the maximum light path, b is the minimum value of the sine wave signal S1, that is, the minimum light value,
T is the period of the sine wave signal S1. The alternating current component of this sine wave signal S1 is expressed as follows, where ω is the angular velocity. Also, its DC component is. It is expressed as Here, if we focus on one period of the AC component, integrate the AC component and the DC component, and take the ratio of the mutual integral values, we get Equation (5) above, which differs from Equation (2) above. 2
Although it is multiplied by the constant /π, it becomes the contrast itself. That is, in the arithmetic circuit 32A, the CCD of the sensor section 31
The optical image signal So sent from the sensor 31A is passed through the bypass filter 321. The AC component is integrated over a predetermined time by an integrating circuit 324 via an absolute value circuit 323,
The other integrating circuit 322 integrates the DC component. Then, the division value of the AC component is divided by the integral A4 of the DC component by the division circuit 327, that is, the division shown in equation (5) is executed, and the result of this division 'Q becomes the contrast of the lens 1 to be tested. The above explanation has been made by replacing the optical image signal So with the sine wave signal S1 shown in FIG. Since the intersection 1i of the optical image signal So and the area ratio of the component to the DC component are calculated using 324, the same is true even if the optical image signal So is a rectangular wave including many harmonic sine waves. It doesn't matter. Note that the drive J control and calculation circuit 32 of the sensor section 31
Arithmetic control of A is performed by a control section to be 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 (the lens mount section 10 and the contrast measurement section 3) according to a predetermined control program 4A (shown in FIG. 17) in the memory.
), and controls all operations including (contrast) JILT constant operation. (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. The contrast of the chart image at multiple points in the optical axis direction of the test lens is measured by driving the lO to rotate the test lens around its optical axis and changing off-axis measurement points. Performed at multiple off-axis positions, (
Measurement 1) From the measurement results of the measurement 1, it is possible to know the following optical characteristics of the lens 1 to be tested. (The determination of quality by comparing these measurement results with reference values is performed by the determination unit 5, which will be described later.) (1) Change in the position on the optical axis where the contrast at each measurement point on the axis shows the maximum value From this, the degree of axial Jl' point aberration can be detected. (2) At each measurement point on the axis, the contrast is maximum ((i
By comparing the average position on the optical axis (average image plane position) with the reference image plane position of the subject lens 1, it is possible to detect whether the pack focus of the subject lens 1 is over or under. (3) Maximum contrast at each off-axis measurement point (+7
The degree of off-axis astigmatism can be detected by the change in position in the optical axis direction, which is indicated by i. (4) Curvature or inclination of the image plane can be detected by comparing the position at which the contrast is at its maximum value (ie, the image plane position) at an off-axis measurement point with the on-axis image plane position. (5) The degree of axial L coma aberration can be detected from the difference in the maximum value of contrast at each measurement point on the axis. (6) Maximum contrast Ii at each measurement point on the axis
Insufficient contrast can be determined from the average value of . (7) Maximum contrast at each measurement point on the axis 1
From the value of the smallest one among them, it is possible to judge whether there is a lack of contrast in part of the lower part L. (8) Each one off axis! Insufficient off-axis contrast can be determined from the average value of the maximum contrast values at a certain 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 lens to be tested 1 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 (36ssX) at the image plane position.
24 + ui) diagonal angles (■ in Fig. 14)
,■,■,■), and the off-axis position is a position at a predetermined distance necessary for determination from the axis' two positions (in this example,
w).However, if the purpose is only to detect curvature/inclination by comparing the image plane position at the 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. Test lens 1 by driving
The CCD sensor 31A of the contrast measurement means 3 is driven to move, the contrast of the chart image is measured, and the lens is held so that the contrast of the chart image at a predetermined measurement point off-axis is measured by rotating the optical axis around the optical axis. Part 10
(rotation of the test lens 1). (Measurement 2) From the measurement results of Measurement 2, (1) Astigmatism on the axis "-" can be detected from the difference in contrast values at each measurement point on the axis. (2) Insufficient contrast on the axis can be detected from the average value of contrast at each measurement point on the axis. (3) Partial deficiency in on-axis contrast can be detected from the minimum value of contrast at each measurement point on the axis. (4) Insufficient off-axis contrast can be determined from the average contrast value 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. The off-axis measurement point for this detection is 1. For example, if the lens to be tested is a 35-layer camera lens that uses film and is of a type that does not rotate during focusing, such as a straight helicoid, the image plane position As shown in Figure 14, 3
51111 film (36m x 24mm) and 8 directions (■ to ■ in Figure 14) on the horizontal and vertical lines centered on the diagonal line and the on-axis position (optical axis center), from the on-axis position. It is sufficient to measure at a position with a distance ah (in this example, the same position h = 15 mm as in measurement 1 described above).
However, in the case of a 35m film, the measurement point on the vertical line ([stock] and ■ in the figure) will be out of the viewing angle at a position of 15m+w from the on-axis position, but data such as the curvature of the field can be measured by 1'J. is very effective. In addition, in the case of a test lens l such as a one-turn helicoid, the lens rotates with focusing and the direction of the lens is not constant, the 30°
It is sufficient to measure in 12 directions (■ ~ @) at ° intervals.The distance from the axial position on the image plane to the measurement position can be set as appropriate according to the angle of view of the lens 1 to be tested. It's good. Next, the detailed operation control will be explained using the flowchart 21. FIG. 16 is a flowchart of the control program 4A of the 2nd control section 4 and the I regular day program 5A, which will be described later. As mentioned above, it is stored in the memory constituting the control unit 4 and consists of a plurality of subprograms (subroutines).In other words, this control program 4A includes the initial setting subroutine 41.0 the preparation subroutine 42.contrast measurement subroutine 43. .Contrast measurement subroutine 4
4. It is composed of a parts recovery & data transfer subroutine 45. Each subroutine will be explained below according to the flow shown in the figure. The initial setting subroutine 41 includes each drive mechanism section 1 display section 6 of the optical system 2 and contrast measuring section 3, and control ff&4.
The memory, etc. in the microcomputer that is configured is set to its initial state. 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. Initialize/set the sensor board 311 to its scanning start position (reference position 21).
), and measure the amount of transmitted light through the lens to be inspected to check for dirt on each chart CA, CZ, large abnormality in the optical system (for example, the lens is stopped down), etc. The contrast measurement subroutine 43 moves the sensor board 311 of the sensor unit 31 to the scanning start position (base edge position).
Scan (move) in the direction of shortening the optical path by approaching the lens to be tested 1 while measuring the contrast at a predetermined distance from iri.
In this embodiment, the scanning width (traveling distance gI) of l scanning step is set to I/12 IIm, and the scanning speed is approximately 240 Step/Sec. uses a pulse motor 316, but 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 amount of defocus as shown in FIG. 17 is obtained, and by numerical calculation, the peak value of contrast and its position can be obtained both on-axis and off-axis. Furthermore, the contrast measurement subroutine 4
In step 3, the contrast measurement is performed four times at the same time by rotating the lens to be tested and changing its measurement point. (+iif-described measurement l) contrast 111 constant subroutine 44 is)
"L Uniaxial" - Set the on-axis and off-axis sensor boards at the image plane position. This corresponds to setting each of the CCD sensors 1-9 on the film surface (designed value) that is in focus at the center. Then, the off-axis contrast is measured in several predetermined directions (the measurement mentioned above?).In other words, for a test lens of a type in which the lens does not rotate, such as a linear helicoid, the off-axis contrast is measured in several predetermined directions. In the case of a type of lens to be tested, such as a rotating helicoid, in which the orientation of the lens is not constant, measurements are taken in 12 directions as shown in FIG. The measurement direction is changed by controlling the rotation of the lens mount section 10 depending on the type of the lens 1 to be tested. The parts return & data transfer subroutine 45 returns the stop position of the lens mount part 10 to the predetermined initial position, releases the lock mechanism 15, and makes it possible to remove the test lens l from the lens testers I and T. At the same time, the measured value of the contrast is output to the personal computer (to be described later), and if the measured contrast is lower than the value measured for the number of turns, air is blown onto the char) CA and CZ from the - side and from the other side. Clean the char (CA, CZ) by suction. Next, each major subroutine will be explained in detail. The contrast All constant subroutine 43 is a subroutine that searches for on-axis and off-axis focus positions (image plane positions). Contrast measurement is carried out using two on-axis and off-axis sensor boards (CCD sensors 31A and 31Z) for two optical paths LA-LZ, one on-axis and off-axis with respect to the lens l to be tested, respectively, as shown in FIG. This is done by Each CCD sensor 31A/3
1Z moves by l scanning steps every time the contrast is measured by - degrees. As a result, contrast 1 to contrast wss (1.v curve of contrast value to defocus amount) shown in FIG. 18 is obtained. All of this contrast value is stored in memory and given a predetermined scanning width wS.
After the S scan is completed, the peak value of the contrast and its image plane position are calculated by the I-determined portion 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. 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 111 subroutine 43 shown in FIG. Hereinafter, each process (in T-order) will be explained according to the flowchart in the figure. In process [11], the sensor section 31 and the calculation section 32 measure the contrast on the axis 1- and off-axis. In the process [21], the contrast measured in the process [+] is transferred to an A/D controller 8 (not shown) disposed after the calculation unit 32.
Convert to digital h). process

In [3], the contrast converted to digital F5 in process [2] is transferred to Do of the scanning average register group provided in the control unit 4. In process [41], the scan-+i-average is calculated by the scan-average register group in the control unit 4, and the calculation result is stored in a predetermined location in the memory. In process [51], in the scanning average register group, each data on each scanning average register is shifted to the respective register. In process [6], each CCD sensor is moved by one scanning step. In process [7], the scanning (movement) amount of each CCD sensor is inspected. That is, it is checked whether the scanning amount (the amount of movement due to scanning) has reached the set number of scanning steps, and if the scanning is completed, the process moves to the next process [81], 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 by &l from the contrast for a predetermined scanning width. In process [9], the lens mount is rotated by a predetermined angle to change the measurement orientation of the lens to be tested. process

In step 101, it is checked whether contrast measurements have been completed for all set orientations (four orientations). When the measurement is completed, the contrast measurement subroutine 43 is exited and the process returns to the main control program t, 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 conditions, 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 is met. The loop consisting of processing [+3] to processing [71] constitutes one scanning step, and in this embodiment, the processing time of one scanning step is set to 4.096 m, 9. In the control section 4, when determining the contrast H11, a scanning average calculation is performed using a scanning averaged register group.Next, the operation of this scanning averaged value will be explained in detail. (Regarding Scanning Average Operation) FIG. 19 is a conceptual diagram of the scanning average register group. The scanning average register group is composed of 8 predetermined number of registers Do"D+, 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 Do of the scanning average register group in register D.
The average of O to D7 is calculated. This lli average value is then transferred and stored in memory as a contrast. Thereafter, each data in the group of scan average registers is shifted to the next register. That is, Do −ml)1,
DI+D2... It is shifted from D6 to Dr. Namely. Since the logic of converting 8 to -1 in binary notation is simple, such processing enables high-speed calculations. Furthermore, data shifting within the register is easy with the microcomputer that constitutes the control section 4. For reasons such as this, scanning ('average calculation can be easily and quickly processed.In addition, in the method described in 2), the contrast peak position where the sum of registers DO to DI is maximum is the sensor board at point IIIf where data is taken into Do. However, since this deviation is always constant, the position where the deviation is 4 scanning steps can be taken as the peak position. , the scanning mode smoothed register group Dg-DI is all F.
Until ULL is reached, the scan averaged contrast is considerably lower than the actually measured contrast. However, the measured value of this part corresponds to the base part of the contrast curve 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 the scanning width WSS amounts to 300 to 1000 steps. Since 1 scanning step is 4.096 +ss, it takes about 1 second to 4 seconds. The contrast peak value and its position are found by repeatedly comparing the contrast values for all the contrast data for each step stored in the memory.Depending on the number of scanning steps, the maximum value is about 10.
The comparison is repeated 00 times, and since the control unit 4 operates at 2M) lz claws in the tree embodiment, the processing time for the size comparison requires about 100 ms. (Regarding shortening of scanning time) Contrast) In the flN constant subroutine 43, the contrast is measured in the four predetermined directions indicated by ■, ■, ■, ■ in Fig. 14, and the peak value of the contrast and its position are calculated. However, if the following conditions are satisfied, the scanning width is reduced based on a predetermined procedure without scanning the entire scanning width wSS. This aims to shorten the scanning time. The conditions are: (1) When there is a large difference in the amount of change due to variations in fb when testing multiple lenses and changes in the measurement point of the image plane within each lens, and the name of the song is larger. . (2) When the tilt of the off-axis image plane of the test lens is small or there is no need to adjust it. (3) Examine changes due to the orientation of the central image plane of the test lens,
This is the case when only the average axial image plane needs to be measured. FIG. 20 is a conceptual diagram illustrating shortening of scanning time. In the figure, the horizontal axis indicates the scanning direction of the sensor port, and the vertical axis indicates the progression of scanning time downward. Scanning of the sensor board is performed four times in four predetermined directions, but first, if the sensor board is scanned in 800 scanning steps for the -th direction, then in the next direction (■), the peak position found in direction (■) plus the predetermined Scanning is performed with a scanning width WSH (this is, for example, 200 scanning steps). - If the peak position in the direction ■ of the second time is the 400th scan step, then the second scan in the direction ■ is 6
00 scan steps would be sufficient. Similarly, in the third direction 11 (■), there are 400 scanning steps, and in the fourth direction (■), there are 400 scanning steps.
00 scanning steps. This results in four scans in four directions totaling 2200 scan steps, compared to a total of 3200 scan steps if all four scans in four directions were scanned at a predetermined 800 scan steps without using this method. This saves about 4 seconds in time. ``Determination Unit 5J (Configuration) The determination unit 5 is constituted by a microcomputer including a CPU and a memory together with the aforementioned control unit 4. Also, in the determination 8111s, J and ``I determination results are temporarily stored. Two 'I'4 constant registers O8O and O51 (not shown) each consisting of 8 bits are provided.The reason why there are two judgment registers, DSO and DSI, is that the number of data to be processed is limited. Furthermore, the memory of the microcomputer that constitutes the determination section 5 together with the control section 4 is used as a display control memory for controlling the display section 6, which will be described later. (Function) The 14 constant section 5 predetermines the contrast value at each measurement point of the lens l to be measured under the control of the control section 4 described above in accordance with the control program 5A shown in FIG. The fljlim program 5A, which performs pass/fail judgment by comparing with the determined judgment criteria, performs judgment 811.
It is stored in the memory constituting 5 and consists of a plurality of subprograms (subroutines). In other words, this control program 5A includes two determination subroutines 51 and 52.
Consisted of. here. 1. By comparing the measurement results of Measurement I (contrast D sizing routine 43) with the judgment criteria, (1) On-axis astigmatism defects (defects due to abnormal changes in the on-axis peak (A-ASU)) ) (2) Over or under back focus defect (
Mechanical back focus defect, excessive defect (large rb)
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 (
(UND), and over-defect, that is, a defect in which the off-axis image plane is farther from the lens side than the on-axis image plane (0VER)) (5) Axial coma aberration defect (defect due to an abnormal change in the best axial contrast (A- CON) ) (6) On-axis contrast deficiency defect (average axial contrast ratio is too small (A-MTFLo)) (7) On-axis partial contrast deficiency defect ((A-NTFPL(8) Off-axis contrast deficiency defect) (Defect in which the average off-axis contrast ratio 1 is too small (Z-MTFLD)) (9) Defect in off-axis coma aberration (
Determine the abnormal change in best off-axis contrast (Z-CON). 2.1Ng2 (contrast) All fixed subroutine 44
) by comparing the measurement results of
) On-axis contrast deficiency defect (^-MTFLO) (3)
Partially insufficient on-axis contrast (if part of the off-axis contrast is small and under-performing (U-U)
), if part of the off-axis contrast is small and excessive (0+H (4) Off-axis contrast deficiency (Z-MTFLO)) (5) Off-axis contrast fluctuation defect (off-axis MTF is severe) Changing defects (Z-
HEN )) is determined. The results of each judgment in the above section [I are shown in the judgment register D.
It is recorded by changing the state of predetermined bits 1 to 8 of SO and DSL (20 for good, 1 for bad), and the judgment result recorded in the judgment register Dso-ost is for each judgment. It is transferred to the display control memory every subroutine 51 and 52. Based on the determination result transferred and stored in the display control memory, each LED provided on the display section 6, which will be described later, is
is controlled to blink. In other words, each LED of one display unit 6 displays the contents of the display control memory,
In other words, the configuration is such that the blinking is controlled according to the state of each bit j, i, (Q or l) of the judgment registers DSO and DSl, and each LED is controlled to blink when the corresponding hint state is O. is turned off, and is turned on in case of l. Further, the data used for the above determination is also sent to a personal computer section PC, which will be described later. A detailed explanation will be given below based on a flowchart. First, the two determination subroutines 51 and 52 constituting the control program 5A will be explained according to the flow shown in FIG. The determination subroutine 51 calculates on-axis astigmatism (astigmatism), coma, off-axis astigmatism (eccentricity), and degree of coma from the results of the contrast measurement subroutine 43 described above. moreover,
+i uniform image plane position on axis (HKNPPM) and 4I off axis
The curvature of field can be calculated from the difference from the homogeneous image plane position (HKNPPZ).
Count -1. Then, by comparing these 51 calculation results with each of the deviation values (to be described later), it is determined whether the lens to be tested I is acceptable or defective, and the determination result is recorded in the determination registers DSO and DSI. Determination subroutine 52 2. Calculate the off-axis contrast and the state of the change in contrast, and use these calculation results as well as each base (which will be described later) as in the judgment subroutine 51. Judgments are made regarding pass/fail and failure contents, and the judgment results are recorded in the judgment registers DSO and [1S1.
a) is transferred to and stored in the display control memory, and each LED of the display unit 6, which will be described later, is transferred to and stored in the display control memory.
This is to control blinking. (Judgment) ^ Standard) Since the criteria for determining the quality of a lens differs depending on the type of lens being tested, the lens tester LT uses the control program 5A-
1- has a lot of judgment no, i1. All of these criteria include control program 5A.
There are 416 names named after STD in J2. The basic value for the image plane is: 5TDPPA: '), Ii-axis image plane 5TDPP
Z: ,! +'; Bewa off-axis image plane 5TOPPAυ:
On-axis under side limit 5TDPPAO: Under-axis side limit 5TIIPPGU n Off-axis angle side limit 5TOPPGO: There is an off-axis side limit,
2. A lens 1 to be tested that falls outside each of the limits is determined to have a defective pack focus fb (mechanical focus position). The base deviation value for image plane change is 5TDPPSA: On-axis image plane change limit 5TDPPS
Z: There is an off-axis image plane change limit, and the tested lens that exceeds each of the above image plane change limits has astigmatism (astigmatism)
It is determined to be defective. Standard values for contrast changes include STDMM
SA: Best axial contrast change limit STDM
MSZ: There is a change limit for the best off-axis contrast, and a test lens that exceeds each of the above change limits is determined to have a coma aberration defect. The reference value for the minimum value of contrast. STDMTNA :Best axis]-Contrast limit S
TDMINZ - Best off-axis contrast limit STD
MNLA Bi-average axis 1 - On-axis contrast limit on the image plane STDMNLZ : Off-axis contrast limit on the A-average axis image plane 5 TrJHNHz : ``1L There is a limit of 11 average value of the off-axis contrast on the image plane on the average axis, and the above A test lens that does not meet each limit is determined to have contrast under-deficiency.In addition, the average off-axis contrast at the average on-axis image plane (1 limit) (
A test lens that does not meet STDMNH2) is determined not to be defective only in a specific direction, but also to be a highly defective lens with a defective average value. (About judgment operation) Fig. 21 1/4-474 c, Fig. 16 d t f
11 is a flowchart of a subroutine 51. below,
1 will be explained according to the flow of each process (step 1) shown in the figure. In process [11], from the four axial image plane positions (PPA) measured in four directions, PPAAx=maximum value PPAMIN: minimum value 1-IKNPPA, average value (SAPPA: maximum value and minimum value Find the difference. In the process [21], the on-axis image plane change limit (5TOPρS
A) and the difference between the maximum value and minimum value calculated in process [1] (5
APPA). Axis” two-field changing mint (
The difference between the maximum and minimum values (5A
If the force (PPA) is large, there will be astigmatism.
A predetermined bit of the determination register (3 bits [1 of the determination register DSO)] is set to 1. +! Q + S I', a camera lens having one-rotation symmetry generally does not produce astigmatism on the optical axis -L. However, if the camera lens is assembled with poorly centered lenses, astigmatism will appear on the optical axis -1-, so =! -Processing [21: The axial image plane position is a predetermined amount]
The lens to be tested that exhibits two fluctuations is determined to have an axial astral defect. Here, defect display will be explained by taking as an example a case where it is determined in the process [21 that there is an axial astigmatism (astigmatism) defect. When it is determined in process [2] that there is a 1-astigmatism (astigmatism) defect, the corresponding focus (3-biff H1 of the determination register DSO) in the determination register 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 (and then turn on the LED 64A (A-ASU) indicating the defect on the display section 6 (shown in Figure 25). In process [3], on-axis under side sumi) (5TD
pp＾■) and processing [I calculated 1 in 11] l yen eve i ()
IKNPPA). 11 average value ()IKNPP than (5TDPPAυ)
M) is larger, mechanical puck focus r
It is determined that the lower side of b is abnormal, and the corresponding bit of the 1 determination register (1 bit 11 of the determination register DSO) is set to 1. As a result, when the contents of the determination register are transferred and stored in the display control memory, the LED 63A (large fb) of the display section 6, which is the manual input ζ of the defect, is turned on. Processing (In 41, there is an abnormality on the over-axis side) (5TDP
PAO) and processing [average value calculated in 11 ()HKNPP
Compare with A). And, Sukekita over side limit (
If the average value (HKNPPA) is smaller than 5TDPPAO), it is determined that there is an abnormality on the over side of the mechanical back focus rb, and the corresponding bit of the determination register (2 bits I+ of the determination register DSO) is set to 1. . As a result, when the contents of the determination register are transferred and stored in the display control memory, the LED 63B (small fb) of the display section 6, which indicates the defect, is turned on. In processing [5], (semi-axis) two image planes (STDPPA)
That is, the difference in image plane position (5AHKNA) between the design value of the axial image plane position and the average i (HKNPPA) calculated in process [11], that is, the average axial image plane position is determined. That is, (5TDPPA) − (HXNPPA) = (
5AHKN^) is calculated. In process [6], an off-axis image plane (5KPPZ) corresponding to (-) the 4i equiaxial image plane (HKNPPA) is determined. This allows measurement of off-axis hun- trast (i.
The off-axis image plane (5KPP) corresponds to (coincides with)
This is because it is necessary to perform the process in Z). Figure 22 shows ), I! The image plane position that is quasi-i and the processing [
11 is a theory IJIJ diagram showing the relationship with the image plane position of 197 yen calculated by 1. As shown in the figure, the amount of deviation of the off-axis image plane from the design value is calculated from the difference in image plane position (5AHKNA) calculated in process [5] to (5AHKNA) / Co
os θ. That is, it is determined from the reference off-axis image plane (5Tnppz). It should be noted that the calculation of the above-mentioned serpentine angle function tends to require a complicated calculation program in the microcomputer that constitutes the determining section 5, and the number of program steps tends to increase unnecessarily. Therefore, in this embodiment, the above calculation is rounded. In process [7], the antagonal one-way limit (5
KPPZU),! =, over one direction 'J myy)
Find (5KPpzo). That is, processing [61
(5KPPZU) = (5KPPZ) + (5T)
DWU) (5KPPZO) = (5KPPZ) −(
5TDWO) is required. % Reason 181 Teha, processing Pl! (73-c calculation L ta 4:
b External image +6i (7) Over one direction sum) (5KP
PZO) and if the value is negative, then (5KPPZO
) = O. This is to eliminate the negative i () and facilitate the arithmetic processing in the determination unit 5. In the process [9J, four +
It is the off-axis image plane position (PPZ), so PPZMAX: maximum f〆i PPZMIN 2 minimum (direct HKNPPZ: 11' uniform 65 APPZ: find the difference between the Ir maximum value and the minimum value. In the process [101, off-axis image Surface change limit (5TDPP
SZ) and the difference (5APPZ) between the maximum value and the minimum value calculated by -1 in process [9]. Off-axis image plane change limit (5TDPPSZ) If the difference between the maximum value and the minimum value of yaw (5APPZ) is larger, it is determined that there is an off-axis astigmatism (astigmatism) defect and the corresponding beam in the 1 judgment register is set. C
'r4 constant register S1)g) is set to 1. As a result, when the contents of the judgment register "-" are transferred and stored in the display control memory, the display section 6 which is an indication of the defect in question.
Turn on LED 65C (Z-ASU). In process [111], the under one-way limit of the off-axis image plane calculated in process [7] (5KPPZU) and process [9]
Compare the tli average (〆i (HKNPPZ)) calculated with the one-way limit (5KPpzu
), if the 1i average value (HKNPPZ) is larger than
Bit 1]) is set to 1. As a result, when the contents of the determination register are transferred and stored in the display control memory, the LED 65A (UND) of the display unit 6, which indicates the defect,
lights up. In process [121], the over-unidirectional sum (5KPPZO) of the off-axis image plane calculated in process I7 is compared with the modulus (tlff (HKNPPZ)) calculated in process [91]. Over one-way limit (5KPPZO)
If the 11 average value (HKNPPZ) is smaller than
'rJl is determined to be an over abnormality in which the image plane is curved to the over side, and the corresponding pitch of the judgment register is set.) ('r4 constant register D
8 hits of SO) [1) 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 65B of the display section 6, which indicates the failure,
(OVER) lights up. In the process [13j, the average Ida i (HKNPPZ) that was 91'O in the process [91], that is! The difference (5A)IK)IZ) in the image plane position between the i-equalized off-axis image plane position and the off-axis image plane position (5KPPZ) calculated in process [61] is determined. That is,
(HKNPPZ) - (5KPPZ) = (5AII
KNZ) is calculated. In process [14], the off-axis image plane difference (5AHKNZ) calculated in process [13] is examined. That is, the off-axis image plane difference (5AHKNZ) chisel E negative is tested. If the off-axis image plane difference (5A)IKNZ) is a positive value. It is considered that the off-axis image plane is located below the image plane on the axis. In this case, the off-axis under-distance amount (PPZGU) is (PPZGU) = (5A)IKNZ) x 2
+ (5APPZ) and ;1 is calculated. This off-axis under-under amount (PPZGU) is equal to the average on-axis image plane (HKNPP
This is equivalent to twice the defocus amount of the off-axis image plane from
) and the off-axis underside limit (5TDPPZU). If the off-axis undersize amount (PPZGU) is larger than the off-axis underside limit (5TDPPZU), the image plane may be curved toward the underside (and eccentricity may also be considered), so the combination of the underside abnormality and the eccentricity abnormality. It is determined that it is defective, and the bit corresponding to the I judgment register (5 bits 11 of judgment register ΩSl) is set to 1.As a result, when the contents of the judgment register are transferred and stored in the display control memory, it is determined that the corresponding defect is displayed. The LED 65G (U+H) of the display unit 6 is turned on. On the other hand, if the difference between the off-axis image planes (5AHKNZ) is a negative value, it is considered that the off-axis image plane is on the over side than the center image plane. In this case, the off-axis overexpression (PPZGO) is (PPZGO) − (5AHKNZ) X 2 +
(5APPZ) is calculated. This off-axis over amount (
PPZGO) is 4 as in the case of off-axis undercarriage.
It corresponds to twice the defocus amount of the off-axis image plane from the i-equal axis image plane ()IKNPPA), and 1. The larger l is in the off-axis over, the more it causes a decrease in contrast.Next, this off-axis over;:: (PPZGO) is compared with the off-axis over side limit (5TDPPZD). If the amount of off-axis overshoot (0 in PPZ) is larger than the off-axis overload (ST! IPPZO), eccentricity is likely as well as curvature toward the overside of the image plane, so It is determined that it is a composite failure of abnormality and eccentricity abnormality, and the corresponding bit of the judgment register (6 viat II of judgment register DSI)
Let be 1. As a result, when the contents of the above-mentioned predetermined register are transferred and stored in the display control memory, the LED 65H (0+H) of the display section 6, which is "/I, the defective defective, 1", is turned on. In process [15], 4 From the four axis L contrasts at the axial image plane position measured for the orientation (MTFA), MTFMAX^: Maximum value MTFMIIIA two minimum images 1) IKNMTF^: Average value 5 ANTFA: Find the difference between the maximum value and the minimum value In process [16], the change limit of the best axial contrast (STDMMSA) is compared with the difference between the maximum value and the minimum ifi (SAMTFA) calculated in process [15J. change limit (S
The difference between the maximum and minimum values (SAM
If TFA) is larger than TFA, it is determined that the two-contrast frame is defective, and the corresponding beat in the determination register (bit 4 of the determination register DSO) is set to 1. As a result, when the contents of the determination register are transferred and stored in the display control memory, LE06 of the display unit 6, which is the indication of the defect,
Turn on 4B (A-COM). In the process [171, the best on-axis contrast limit (S
Compare T[1NINA) with the average value (tIKNMTFA) multiplied by 1 in processing [15j. If the value is small, it is determined that the value of the contrast on the axis is insufficient, and the corresponding bit of the determination register (5 hits 11 of determination register 050) is set to 1.As a result, the contents of the F1 constant register are transferred to the display control memory. When stored, the LED 64C (A-MTF@LOW) of the display unit 6, which indicates the +tA failure, is lit. In the process [181, the best axial contrast limit (S
TDMINA) and processing [minimum I+I' calculated in 151
+ (to TFMINA). Here, if the minimum value (TFMINA) is smaller than the best on-axis contrast limit (STDMINA), it is determined that there is a shortage of iIi in a part of the i top contrast test, and the corresponding bit of the 1 judgment register (rl judgment register SO (6th bit) is set to 1. As a result, 1. When the contents of the determination register are transferred and stored in the display control memory, the LED 64D (A-MTF·PL) of the display section 6, which indicates the defect, is turned on. In processing [19], four off-axis contrasts at off-axis image plane positions with Δ11 constant in four directions) (MTFZ)
From, MTFMAXZ: the maximum value, TFMINZ: the minimum value, HKNMTFZ: the average value of the cap, 5ANTFZ: the difference between the maximum value (and the minimum value). In process 1201, the best off-axis contrast limit (S
TDMINZ) and processing [191 calculated average value (HK
NMTFZ). Here, the average contrast limit (STDMINZ) is higher than the best off-axis contrast limit (STDMINZ).
If (HKNMTFZ) is smaller, it is determined that the off-axis contrast value is insufficient, and the corresponding bit of the 1 determination register (3 bits 1 of the determination register opening S1) is 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 ED65E (Z-MTF fist LOW). In process [211, the change limit of the best off-axis contrast (STDMMSZ) is compared with the difference (SAMTFZ) between the maximum value and the minimum value calculated in process [191].Here, the change limit of the best off-axis contrast (5T
OWNSZ ) than the difference between the maximum value and the minimum value (5A) I
If TFZ) is weaker than hII, it is determined that the frame is defective outside hII, and the corresponding pitch of 'I'lJ constant register) ('r-
The second bit of the constant register DS1) is set to 1. As a result, when the contents of the determination register O5+ are transferred and stored in the display control memory, the display section 6 which is an indication of the defect in question
Turn on LED65D (Z-COM). In the process [22I], a comprehensive judgment is made based on the incidental judgments in the judgment subroutine 51, and step 11
Check all bits of constant registers DSO and []Sl. In other words, if the lens l to be tested has some kind of defect, the bits in either the determination register DSO or DSl should become 1 by executing each process up to the above process [21]. Therefore, by inspecting the state jS of all the hits in the 1 judgment registers DSO and [lSl, it is possible to know the presence or absence of each defect in the lens 1 to be tested. In other words, if all bits in the determination registers DSO and DSl are O, the lens to be tested 1 is determined to be good, and
'4 Comprehensive good judgment correspondence register of constant subroutine 51 ('
The 8 bit [1] of the rg constant 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 LE of the display section 6 that indicates a non-defective product is displayed.
Turn on D62B (good). On the other hand, judgment register D
If all the bits of SO and DSI are inspected and there is even one bit of l, it means that the tested lens l has some kind of defect corresponding to that bit, so the tested lens l is considered to be defective. It is determined that the register corresponding to the total failure of the determination subroutine 51 (7 of the determination register DSI) is
By) Set [1) to 1. As a result, when the contents of the determination register DS1 are transferred and stored in the display control memory, the LED 62A (defective) of the display section 6, which is an indication of a defective product, is turned on [in 23J, the determination register DS
The contents of O and DSI are written to the display control memory in the memory t2ξ. That is, by executing the process [231], each defect content as a determination result is stored in the display control memory, and the content is displayed by lighting on each LEI of the display section 6. This process is based on the handling principle that the N constant 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. This is the processing according to No. 11. The determination subroutine 51 executes the following 23 items of processing before writing. Next, the determination subroutine 52 will be explained. In this identification subroutine 52, the test lens 1 is determined based on the contrast measured in the contrast 414 subroutine 44 described above, that is, the test lens 1 is determined based on the contrast measured at the average axial image plane. As the determination criterion here, the reference value with the STD used in the determination subroutine 51 described above is used. FIG. 24 1/2 to 2/2 is a flowchart of the determination subroutine 52 shown in FIG. 16. Hereinafter, the explanation will be +53 according to the waveform of each process (in order of -r) shown in the figure. In process [1], 8 or 1 in predetermined 8 or 12 directions measured at +l equiaxial -L image plane position.
From the contrast of the two axes, find the difference between I and the minimum value. In process [2], the change limit of the best axis contrast (STDMMSA) and the maximum iCti calculated in process [11], ! : Minimum Ida (which difference (SA to TFL, A
). Here, if the force of the difference between the maximum value and the minimum value (SAMTFA) is larger than the change limit of the contrast on the best axis (MSA to STD), it is determined that the on-axis contrast is defective. Set the corresponding bit (3 hints [1) of the judgment register DSO to 1. This allows you to write to url! When the contents of the fixed register are transferred and stored in the display control memory, the LED 64A (A-ASU) of the display section 6, which indicates the defect, is turned on. Processing [31] compares the average axial contrast limit (STDMNLA) on the image plane with the process [1KN)IFLA calculated in Processing [1]. Axis 1 contrast trie E y ) (S
TDMNLA) than VIl Junyo (HKNMFLA)
is smaller, it is determined that the on-axis contrast value is insufficient, and the corresponding focus in the determination register (5 bits r, l of the determination register DSO) is set to 1. With this, "two legs" I
When the contents of the fixed register are transferred and stored in the size control memory, LE064C (A
-MTF-LOW) lights up. In process [41], the axis-1-contrast trimming (STDMNLA) on the average axial image plane is compared with the minimum value (MTFMNLA) calculated in process [1]. "Average axis" - axis at the image plane - 1 two-contrast limit ('
STDMNL) than the minimum level (MTFMNL)
If A) is smaller, it is determined that a part of the on-axis contrast value is insufficient, and the corresponding bit in the determination register (bit 6 of determination register O8O) is set to 1. With this,”
When the contents of the two-leg determination register are transferred and stored in the display control memory, the LED 64 of the display section 6, which is an indication of the defect,
Turn on D (A-MTF・PL). In process [5], a part of the off-axis contrast measurement value (data) is transferred and the data is saved. The eight or twelve off-axis contrast measurement data 1 are each stored in a dedicated save register (MTFZLO to MTFZL7 or FZLO to MTFZL11). Therefore,
When off-axis contrast is measured in 8 directions, the measurement ID of the 4th direction is 1. In other words, the save register (MTFZL
3) to the 8th direction save register (MTFZL7).
). Thereafter, the measured value in the seventh direction, that is, the contents of the save register (MTFZL6), is transferred to the save register (MTFZL3) in the fourth direction. This transfer of measured values is a precaution to carry out the calculation process in the next process [6], and the measurement value of the fourth direction is the data to be transferred to the personal computer PC, which will be described later. This is due to data backup work. In addition, when off-axis contrast is measured in 12 directions, all of the measured data is used, so skip the process [5] and move on to the next process [61]. From the measured values, find the difference between MTFMXLZ: maximum value KTFMNLZ: G small fI HKNMFLZ: i' uniform jli SA and TFLZ: maximum value and minimum value. In addition, when the off-axis contrast is set to 411 for 8 directions, the evacuation register (M-FZLO to MTFZL5)
From the contents of the above,

[Seek. In addition, when off-axis contrast is measured in 12 directions, each of the above-mentioned angles is determined from the contents of the save registers CMTFZLO-MTFZLll). Place J! l! In H), the measured value of the seta+1+outer contrast is returned to the original value. In other words,
If the off-axis contrast is set to 411 for 8 directions, save it to the save register (MTFZL7)! ! Saved 4th direction measurement a." to the original save register (MTFZL3)
and restore it to its original state. Now, the measured value in the 8th direction has disappeared due to the data saving operation in the process [5]. Since the measured value of the fourth direction, which is symmetrical to this, has been secured, there is no report. Furthermore, when the 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 [8J] after executing the process [61]. In the process [81], the off-axis contrast limit (STDMNLZ) at the image plane is compared with the minimum value (NTF) IIILZ calculated in the process [61]. Off-axis contrast limit at the mean on-axis image plane (ST
DMNLZ) than the minimum (drc MTFMNLZ)
If the force is small, the direction of the curvature of field should be inspected, as there may be a poor combination of field curvature and eccentricity. In addition, off-axis contrast trimming (STII
If the minimum i〆f (MTFMNLZ) is not smaller than MNLZ), the process immediately proceeds to process [lO]. The direction of field curvature has already been checked by the determination subroutine 51. In other words, (PPZGO) > (pp
zcu) then over one direction, (PPZGO) < (
PPZGU), it is under one direction. therefore,
If the image plane of the test lens is curved in one direction, it is determined that the off-axis contrast is abnormal due to the combination of the under and eccentricity, and the corresponding bit of the 1 determination register (determination register O
51 (5 bits) 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 65G (U+H) of the display unit 6, which indicates the defect, is turned on. On the other hand, if the image plane of lens 1 (7) to be tested is overcurved in one direction, it is determined that the off-axis contrast is abnormal due to a combination of overshoot and eccentricity, and the corresponding bit of the 1 judgment register (6 bits of the judgment register DSI) is determined. I is set to 1.As a result, when the contents of the determination register are transferred and stored in the display control memory, the LED of the display unit 6 that indicates the defect
Turn on 65H (0+H). In processing [91, the limit (STDMN) 12) of the 11 average value of the off-axis contrast at the image plane with 1 as the equal axis and the +i average value (HKNMFt, Z
) To'i-ratio V. Then, the limit of the 11 average value of the off-axis contrast on the 11 average axial image plane (STDM
If the average i (HKNMFLZ) is smaller than NH2), it is determined that the off-axis contrast value is insufficient, and the corresponding bit of the determination register (bit 3 [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 65E (Z-MTF/
LOW) is lit. In process [101], the best off-axis contrast change limit (STDMMSZ) is compared with the difference (5ANTFLZ) between the maximum value and minimum if calculated by 1-1 in process [61]. Here, the best off-axis contrast change limit) (, S
The difference between the maximum and minimum values (SAMT
FLZ) is larger, it is determined that there is an off-axis contrast fluctuation abnormality, and the corresponding bit of the 'r1 constant register ('I'
The 4 hits (]) of the constant disk DS1 are 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 LED 65F (Z-HEN). In process [111, 1 judgment register DSO5 and []S+
Inspect all the focus points. This is ``1g constant sub-
Processing in the register 51 (same as in the case of 221, for individual judgments in the 'I constant subroutine 52), (then a comprehensive judgment is made, and the 1 constant registers DSO and DS
Check all bits of each bit of I. That is, if all the vias in the judgment registers DSO and DSI) are O, the lens l to be tested is determined to be non-defective, and the 8-bit register ('t'J! []) is set to 1. As a result, when the contents of the 'l'4 constant register are transferred and stored in the display control memory, LE062 of the display section 6, which indicates a good product,
Turn on B (good). On the other hand, if all the focus points in the judgment register DSO and []Sl are checked and there is even one bit in l, it means that the tested lens l has some kind of defect corresponding to that bit. The test lens I is determined to be a defective product, the test lens I is determined to be a defective product, and the comprehensive defect judgment correspondence register (
7 bits 1]) of the judgment register DSI are set to 1. As a result, the contents of the determination register described in - are transferred and stored in the display control memory. LEE) 62A (defective) on the display section 6, which indicates a defective product, is turned on. In process [12], one constant register oso and DS
The contents of I are stored in the display control memory within the memory. That is, by executing the process [I2], 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 also
+iii Processing of the determination subroutine 51 described above [231
Similar to , this processing is due to handling reasons. The determination subroutine 52 executes the processes in item 12 [1] below in the order of description. “Display unit 6” (Structure) The display unit 6, as shown in FIG.
A light-emitting lamp 1 arranged on a display panel 61 displays a constant result.
” (LED). The display panel 61 includes a total r1 constant (7) LED 62A.
62B and 1 Judgment unit 5 corresponds to t'l 'AI and each judgment unit [j different LED (63A, 63B, 64A, 6
4B-64C・64Dφ65A-65B・65C・65
D, 65E, 65F, 65G, and 65H), or are placed at predetermined positions as shown in FIG. Incidentally, a power switch 66 for the lens tester LT, a start switch for all operations, etc. are also arranged in the display panel 61. (Function) Each LED arranged on the display panel 61 is a display provided in a microcomputer that is connected to the control section 4 and has a constant voltage 5, as explained in the above-mentioned section regarding the determination section 5. 1!, < is controlled by the control memory. That is, the display control memory stores the above-mentioned judgment register O5 which stores the judgment result by the l'lI constant section 5.
The contents of O and DSI are stored. Each LED of the display panel 61 corresponds to the content of the display control memory, that is, each bit of the determination registers DSO and DSI in the determination unit 5, and the state of each bit +! ; Blinking is controlled in accordance with (0 or l). In other words, each LED has its corresponding bit state O.
In this case, the light is turned off. In the case of ■, it is lit. Each LED and the rII constant register are connected to the DSO and DSI.
The correspondence with each bit, that is, which LED corresponds to which bit of the judgment registers O5O and DSL, is explained in the explanation 1 of the 1 judgment subroutines 51 and 52 in each case. , will be omitted here. Next, the jL type display contents by each LED will be explained. The overall judgment LEDs 62A and 62B are 62A when the tested lens 1 is a defective product (that is, one of the various judgment criteria has been missed). In this case, one of the LEDs for each inspection item II described later is always lit. ) lights up, and 62B is the test lens 1.
Lights up when the product is good (judgment of type // satisfies 1x complete). The LEDs for each judgment zrtn are: 63A, 63B75 < Mechanical puncture focus failure, 64A to 64D indicate a defect in the lens support 1, that is, the center, and 65A to 65H indicate a defect outside the lens axis, that is, a defect in the periphery. , and when it lights up, it indicates the defect. Below, each r4 constant HM'l is displayed (lit) by LED.
will be explained individually. When the test lens l passes all judgments, 62B, which indicates a good product, lights up. If it is defective, 62A, which indicates a defective product, lights up.
The details (reasons) of the defect are displayed by lighting up the LEDs for each of the bolts 111 from 63A to 65H. 63A is a mechanical back focus excessive defect (fb
Lights up when large. 63B is defective due to lack of mechanical focus back (fb
/j1) Lights up. 64A lights up when there is an axial failure, that is, a failure due to an abnormal change in the on-axis peak (A-ASU). Possible causes of this defect include eccentricity of the constituent lenses constituting the test lens 1tl and poor polishing. 64B lights up when there is a frame failure, that is, a failure due to an abnormal change in the best axial contrast (A-CON). Possible causes of this defect include eccentricity and poor polishing of the constituent lenses constituting the lens 1 to be tested. 64C is defective due to lack of axial contrast, that is, average axis]
2. Lights up when MTF I is too small (A-MTFLO). A possible cause of this defect is poor polishing of the components that make up the lens 1 to be tested. 64D is defective (A
-NTFPL). This is a milder defect among the defects shown by 64C. Therefore, 6
When 4C lights up, 64D also lights up. 65A lights up when there is an under-defect, that is, a defect (UND) in which the off-axis image plane is too far toward the lens side than the axial 1° image plane. 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 error (0VER) in which the off-axis image plane is farther from the lens side than the image plane. The cause of this defect may be poor spacing or large eccentricity of the constituent lenses constituting the lens 1 to be tested. 65G lights up when there is an off-axis astral defect, that is, a defect where the off-axis image surface is tilted (Z, -ASU). This bad boy! ;
(The reason may be the eccentricity of the constituent lenses constituting the test lens 1. 65D lights up when there is an off-axis coma defect, that is, an abnormal change in the best off-axis contrast (Z-COM).
[Possible causes include poor polishing of the constituent lenses constituting the lens 1 to be tested and eccentricity. 65E has a lack of off-axis contrast value, that is, qi average 1h
11 Outer item/Totest toy〆(is too small defective (Z-MT
Lights up when FLO). Possible causes of this "A" and "Good" are decentering of the constituent lenses constituting the lens to be tested (1) and alignment defects such as changes in the distance (2). 65F lights up when there is a defect (Z-HEN) in which the off-axis contrast fluctuates, that is, the off-axis contrast changes drastically. 65G lights up when a part of the off-axis contrast is small and under-defective (lJ,)l). D of this defect (The cause may be poor alignment of the constituent lenses constituting the lens to be tested 1. 65H is a defect when -1 of the off-axis contrast is small and the defect is over (0+H) 111r lights up. This defect D; (The cause may be poor alignment of the constituent lenses constituting the test lens 1. By displaying the following defective ratios, it is possible to identify the defect of the test lens L. In addition to the 14-degree identification, it is also possible to perform classification by cause of failure, making it possible to improve the efficiency of inspection work. Connect the personal computer section PC as shown in Figure 26 to create lens tester system 1.
, which enables processing of information (δIII determination and determination data) from the lens tester LT. (Configuration) The personal computer section PC is a so-called 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 the control section 5 of the lens tester LT, and the measured values of the lens tester LT and commands from the personal computer section PC are transmitted to the microcomputer that constitutes the control section 4 and the control section 5 of the lens tester LT. I° Ini Uke is supposed to be passed. (Function) The personal computer IPc can integrate and process the data manually inputted from the lens tester LT to create secondary data useful for managing defect countermeasures for the tested lens l, etc. This data can also be printed out by printer 74. In addition, the measurement data and secondary data are displayed on the CRT display 7.
3-1- can be displayed as a graph and can be printed out using the printer 74. This allows the measurement data to be visualized, and it becomes possible to grasp more detailed image plane conditions, etc., which cannot be understood from the judgment display on the display unit 6 of the lens test LT. Figure 27 shows the CRT display 7.31 of measurement data;
This is an example of graph display. The graphical display is - - 4 types of graphs on the screen (The graph on the left side of the screen is called G1. The graph on the bottom left of the screen is called 62, the graph on the right side of the screen is called 63, and the graph on the bottom right side of the screen is called of.)
are displayed at the same time, and these clearly represent the characteristics of the lens l to be tested. The coordinates of each graph are graph Gl, the vertical axis of G2 is the contrast and image plane position, graph G3... The vertical axis of G4 represents the contrast, and the horizontal axis represents the direction in each graph. Graphs G3 and G4 represent the 8 directions (X? or 12 force positions) in the contrast Jllll constant subroutine 44. Next, each graph will be explained individually. Graph Gl is the contrast) +!llll constant subroutine The peak of the on-axis contrast in each direction measured in 43 ((i) and its image plane position (best off-axis image plane position) are shown, and the solid line indicates the peak value of the conotrast at each measurement point. The position (best image plane position) is indicated by a dashed dotted line.The designed image plane position is also displayed to make it easier to understand changes in the image plane state of the lens to be tested. Graph G2 is calculated by contrast measurement subroutine 43.
The peak value of off-axis contrast in each determined direction and its image plane position (best off-axis image plane position) are plotted with the peak value of contrast at each off-axis measurement point as a solid line, and the position (A &
The position of the good image plane is indicated by a dashed-dotted line. It should be noted that, similar to the graph Gl, the image plane position of the camera is also displayed (71 is displayed. Graph G3 is a contrast) J11 constant subroutine 4
4 is a graph of the contrast for each direction Q at the 7 positions, and the axis-1 contrast is shown as a solid line.
In addition, the quality of the lens to be tested: "i 't! 1 constant, (the deviation value is shown by a dashed line. Therefore, "++
In J graph 3G, if the contrast shown by the solid line exceeds the pass/fail judgment value, it is determined that the lens is good in terms of axial contrast. Graph G4 shows the contrast Jllll constant subroutine. 4
This is a graph of the off-axis contrast for each direction at the image plane position measured in step 4, and the off-axis contrast is shown as a solid line. (The quasi-fda 1 is shown by a dashed line. Therefore, in the graph 4G, similar to the graph 3G, the contrast shown by the solid line is the quality judgment)
(If it exceeds /i, it is determined that the lens is of good quality in terms of off-axis contrast.) From the two graphs, 5 For example, the optical time of the test lens is determined as shown below. (1) In graph G2, as shown in Figure 28, the graph of the off-axis image plane position of each measurement point is shown intersecting with the design image plane position. 30(a), it can be seen that the image plane is tilted.Such a state 5L occurs when the constituent lenses of the test lens l are decentered. (2) As shown in Figure 29, in the graph Gl, the axis of each measurement point -
The image plane position graph of 1- is near the designed image plane position,
In graph G2, the graph of the off-axis image plane position of each measurement point is on either the upper or lower side from the designed image plane position (at 1Δ, it is approximately 11 lines away from the lens). It can be seen that the image plane is curved (curved toward the bottom side in the figure) as shown in FIG. 30(b).
3 occurs when there is a change in the distance between the lenses of the lenses 1 to be tested. [Efficacy of IJJ+J! ] As explained above, according to the present invention, the peak position is calculated from the contrast with respect to defocus in the lens to be tested, and the step movement amount of the detection means is updated to decrease in accordance with the peak position. The measurement of the contrast for defocus and the calculation of its peak position are performed multiple times, and the average of the multiple peak positions obtained by this is taken as the best image plane position, so the optical lens (
The best image plane position of the lens under test can be searched with high precision and efficiency. Therefore, by making a judgment about the above-mentioned best image plane position in the judgment section that constitutes a lens tester, the judgment section can make a comprehensive judgment of the quality of the optical lens, and thereby the optical lens can be tested with good viscosity. .

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a schematic configuration of a lens tester to which a preferred embodiment of the best image plane position detection method of a lens according to the present invention is applied, FIG. 2 is a plan view of a lens mount, and FIG.
The figure is the ■-■ cross-sectional view, Figure 4 is the configuration diagram of the light source section,
The figure is a graph showing the radiation or transmission spectral characteristics of each component of the light source section, Figure 6 is a plan view of the chart, Figure 7 is a top view of a part of the off-axis mirror, Figure 8 is its left side view, Fig. 9 is a plan view of the sensor section, Fig. 10 is a sectional view taken along line XX, Fig. 11 is a sectional view taken along line XI-XI in Fig. 9, Fig. 12 is a block diagram of the calculation circuit, and Fig. 13 is a calculation An explanatory diagram of a sine wave signal related to contrast calculation in the circuit. Figures 14 and 15 are sections showing off-axis measurement point positions, Figure 16 is a flowchart of the control section and judgment section, and Figure 17 is a diagram showing the difference obtained by measurement. Characteristic curve of contrast value with respect to focus amount, Fig. 18 is a flowchart of the contrast measurement subroutine, Fig. 19 is a conceptual diagram of the scanning average register group, Fig. 20
Figure 522 is an explanatory diagram showing the relationship between the reference image plane position and the average image plane position;
The figure is a flowchart of the determination subroutine, 25UA is a plan view of the display panel, FIG. 26 is a block diagram of the configuration of a lens tester system to which the lens tester LT according to the present invention is applied, and FIG. 27 is a diagram of the display of measurement results by the personal computer section. Figures 28 and 29 are illustrations of the display in Figure 27, 3θ diagrams are illustrations of image plane changes corresponding to Figures 28 and 29, and Figure 31 is a conventional example. FIG. 32 is a graph showing the M T F tlh line, and FIG. 33 is a diagram explaining the estimation of the characteristic MTF of the tested lens from the MTF value at a single spatial frequency. . l...Test lens CA, CZ...Chart (lattice chart) 31A/3
1Z... CCD sensor (detection means) 3... Contrast measuring means T... Lens tester diagram (%) (a) ('/1) (b) Wavelength (nm) Wavelength (nm) Wavelength (nm) Wavelength (nm) Figure Figure Figure Number ↓! (16b) Figure Figure Figure Figure Figure Movement on the optical axis of CCD sensor Figure Illustration Figure Direction Figure Direction Figure Spatial Frequency Procedure Correction (Method) % Formula % Name of Invention Lens Relationship with the Case of Person Who Corrects the Best Image Surface Position Detection Method Patent Applicant (052) Asahi Optical Industry Co., Ltd.

Claims (1)

[Claims] A chart image of a lattice chart formed by a lens to be tested is detected by a detection means that can be moved in steps in the optical axis direction of the lens to be tested, and a contrast measuring means that operates in conjunction with the step movement of the detection means detects the chart image of the lattice chart. In a lens tester that continuously obtains a large number of image contrasts based on a chart image detection result by the detection means,
The detection means is operated to detect and move by a predetermined amount of steps, and as a result, a large number of contrasts are continuously obtained from the contrast measurement means, and the peak position is determined by comparing the magnitudes of these contrasts as the contrast for the defocus of the lens to be tested. At the same time, the step movement amount of the detection means is updated to decrease in accordance with the peak position, and the contrast with respect to the defocus is measured and the peak position is calculated multiple times, and the multiple peak positions obtained thereby are updated. A method for detecting the best image plane position of a lens, characterized by using the average as the best image plane position.