JPH0554901B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method and apparatus for centering at least one lens in a compound lens constituted by a plurality of lenses. .

[Conventional technology]

Not only photographic lenses but also general lens systems are composed of a compound lens that is a combination of a plurality of lenses. When assembling a compound lens, centering work is required to align the optical axes of each lens.

Conventionally, this centering work is mainly performed visually. In other words, light from a point light source is incident on a compound lens to form a point image on a reticle or screen, and while visually observing the deviation of the image formation position, the appropriate lens is moved to eliminate the deviation of the point image. Alternatively, when visually observing a point image, the compound lens is rotated around the optical axis, and the appropriate lens is moved and adjusted to eliminate shake of the point image. However, this type of centering work based on visual observation has the disadvantage that it is difficult to maintain constant centering accuracy due to individual differences or fatigue accumulated through repeated work.

In order to solve this problem, a photoelectric element divided into four parts, for example in a fan shape, centered on the optical axis, is placed on the focal plane of the compound lens, and the outputs from these photoelectric elements are compared. A method of photoelectrically and quantitatively evaluating the deviation of a point image from the optical axis has also been used. According to this, by moving and adjusting a predetermined lens so that the output from each divided photoelectric element is equalized, that is, so that the center of the point image is at the division center of the photoelectric element, the center You will be able to adjust the output.

[Problem that the invention seeks to solve]

However, when attempting to perform centering adjustment using such a method, the optical axis of the lens system, which serves as a reference in the compound lens, must be precisely aligned with the dividing center of the photoelectric element. For example, when inspecting the misalignment of the rear group lens with respect to the front group lens or adjusting the centering, it is essential to align the optical axis of the front group lens with the dividing center of the photoelectric element in advance. Therefore, in products intended for mass production, such as photographic lenses, the optical axes must be aligned for each lens, making this task extremely troublesome.

The present invention has been made in view of such prior art, and provides a centering system for automating the centering work of compound lenses, greatly improving the work efficiency, and maintaining the centering accuracy at a constant level. The purpose of this invention is to provide a method and device.

Of course, the compound lens to be centered in the present invention can be used not only for photographic lenses but also for various optical systems. Furthermore, the lens that is moved and adjusted for centering may be two or more lens units that have been adjusted for centering in advance and are combined together.

[Means for solving problems]

In order to achieve the above object, the present invention passes a light beam through a composite lens having a positive power as a whole including a lens that is movably adjusted for centering, The object point is made incident on a detection optical system arranged so that it is located away from the image position. As a result, the light beam is formed on the focal plane of the detection optical system as a blurred image consisting of a low-luminance halo portion and a high-luminance core portion. This blurred image is captured by an imaging device, and image signals are obtained for each of the halo and core regions. Based on the image signals obtained in this way, the contours of each of the halo portion and the core portion are determined, and furthermore, their center positions are determined. The center positions of the halo portion and the core portion thus determined do not match if the centering of the complex lens is insufficient. Therefore, in the present invention, a predetermined lens, that is, a lens to be centered, is adjusted so that these center positions match, or so that the amount of deviation between the center positions is within a predetermined control value range. Centering is performed by adjusting movement within a plane perpendicular to the optical axis.

The device of the present invention for performing such centering is
A table that holds a reference lens of a compound lens, a movable table that movably holds a lens to be centered in a plane perpendicular to its optical axis, and a movable table provided on the table and the movable table. a light beam generating means for making the light beam enter the compound lens through an optical path; a detection optical system positioned at the detection optical system; an imaging device that captures an image of the halo and the nucleus formed by the detection optical system; an image calculation unit that determines contours and determines the center positions of the halo portion and the core portion from these contours; and a table drive device that moves the movable table so that each of the center positions is within a predetermined control value range. It is equipped with the following.

An embodiment of the present invention will be described below with reference to the drawings.

〔Example〕

In FIG. 1 schematically showing an example of the device of the present invention, a base 1 includes a lamp 2, an optical system 3 for converting light from the lamp 2 into a light beam of a constant diameter, and an optical axis of the optical system 3. A mirror 4 is provided to direct the light beam along 3a directly upward. An X-table 5 that slides in the X-axis direction (horizontal direction parallel to the plane of the paper) is attached to the top surface of the base 1, and an X-table 5 that slides in the Y-axis direction (direction perpendicular to the X-axis) is attached to the top surface of the X-table 5. A Y table 6 is attached. Furthermore, an x-table 7 that slides in the X-axis direction is provided on the Y-table 6, and a y-table 8 that slides in the Y-axis direction is further provided on the x-table 7.
is provided.

An optical path is formed in the center of each of the X table 5 and Y table 6 to allow the light beam from the optical system 3 to pass upward, as will be described later, and the x table 7 and y table 8 are It is arranged so as not to obstruct the upward passage of the light beam. A microscope 12 is provided via a support 10 to receive the light beam passing upward. An elevating mechanism 13 is interposed between the column 10 and the microscope 12, so that the microscope 13 is movable in the Z-axis direction (up and down direction parallel to the plane of the paper).

By adjusting the eyepiece of the microscope 12 to a predetermined position, or by adding an adapter lens or the like, the microscope 12 forms a real image, and this image is captured by the video camera 14. The video signal obtained from the video camera 14 is processed by an image processing section 15.
As will be described in detail later, various signal conversions and calculation processes are performed, and the results are displayed on monitor 1
6, a hard copy is made with a printer 17, or a floppy disk 18 is displayed.
information is stored in

A controller 20 configured by a microcomputer is connected to the image processing section 15, and signals are exchanged with the image processing section 15. The controller 20 also outputs a signal for controlling the operation of the stage moving mechanism 21, and this signal causes the X table 5, Y table 6, x table 7, and y table 8 to be They are slid individually via stepping motors. Similarly, the lifting mechanism 13
is also operated, and the microscope 12 is also moved up and down.

As shown in FIG. 2, which shows the main parts of the above-mentioned device, the front lens group 24a of the photographic lens 24 is
Through the sleeve 6a formed on the stage 6,
held in place. Also, the rear group lens 24b
is placed on the upper surface of the front lens group 24a and is provided on the Y stage 8.
a, it is positioned so as not to move in either the X-axis or Y-axis direction. Note that by tightening these front group lens 24a and rear group lens 24b with screws 25, they are integrated as a photographic lens 24. Also, screws 25 are attached to the frame 26 for attaching the rear group lens 24b.
Since the mounting hole 26a is formed with an inner diameter larger than the outer diameter of the mounting hole 26a, even after adjusting the position of the rear group lens 24b in the X-axis and Y-axis directions, the front group lens 24a and the rear group lens 24b can be attached with the screw 25. It is now possible to combine them into one.

The light from the lamp 2 passes through condensing lenses 27 and 50.
A pinhole plate 28 with μm pinholes formed therein;
A collimator lens 29 transforms the light into a light beam 30 with a diameter of 15 mm, which is incident on the mirror 4. mirror 4
The light beam 30 directed upward by the front lens group 24a and the rear lens group 24b pass through the front group lens 24a and the rear group lens 24b.
Since the light beam 30 is parallel light, the front lens group 2
4a and the rear group lens 24b are correctly aligned without eccentricity, the light beam 30 is focused on the focal point P ₀ of the photographic lens 24 as a point image.

The optical axis of the microscope 12 is the optical axis 3a of the light beam 30.
, and the object point P ₁ is removed from the focal point P ₀ of the photographic lens 24 by l. Therefore, when the CCD 32 of the video camera 14 is provided on the imaging plane of the microscope 12 and an image is captured, an image as shown in FIG. 6 is displayed on the monitor 16. That is, a high-luminance core portion 35 in which the point image of the photographic lens 24 spreads according to the defocus amount l, and a circular halo portion 36 with low luminance are observed.

Next, the automatic centering action for the rear group lens 24b will be explained with reference to FIG. 3 showing the functional blocks of the above device.

First, set the front group lens 24a on the sleeve 6a of the Y table 6, and place the rear group lens 24b on top of it.
is placed and held horizontally by the clamp lever 8a. After that, the keyboard 40 is connected to the microprocessor unit 41 (hereinafter referred to as MPU 4).
When a start signal is input to the second
A drive signal is supplied to each of the elevation drive unit 43, the X table drive unit 44, the Y table drive unit 45, the x table drive unit 46, and the y table drive unit 47 shown in the figure. And these drive parts 43~
Stepping motor 49, 50, 5 by 47
1, 52, and 53 are rotated by a certain amount, and each is set at a preset measurement start position. Further, the object point P ₁ of the microscope 12 is positioned so as to be at a constant defocus amount l corresponding to the focal length of the photographic lens 24 . Note that data necessary for setting this measurement start position and operating programs for each drive section are stored in the ROM 55.

When each part is thus set at the measurement start position and this set completion signal is fed back to the MPU 41, the image formed on the CCD 32 by the microscope 12 is read as an electrical signal.
The image signal read by CCD32 is
The A/D converter 57 inputs each dot to the image calculation section 58 as a digital signal representing the brightness. The digital signal obtained in this way is
The image data is stored in the VRAM 59 as image data associated with dot coordinates. Then, the MPU 41 first binarizes the image data stored in the VRAM 59 at a predetermined brightness level using the first threshold level signal, and associates this binarized information with dot coordinates. Te BRAM60
Store in. Note that the first threshold level signal is stored in the RAM 61 by input from the keyboard 40 together with a second threshold signal of a higher brightness level. Further, the image signal stored in the VRAM 59 as a digital signal is subjected to signal processing for displaying the image by the signal processing section 62, and thereby the monitor 1
6 displays an image as shown in FIG. This image corresponds to the eccentricity of the rear group lens 24b,
The image is projected as a blurred image consisting of a high-brightness core portion 35 with an irregular shape and a low-brightness halo portion 36 that spreads out in a frame-like direction around the core portion 35.

By the way, as mentioned above, the BRAM 60 has two thresholds depending on the first threshold level signal.
Valued binary data is stored. The brightness level of this first threshold signal is determined corresponding to the brightness of the halo portion 36. Then, the MPU 41 refers to the binarized data of the BRAM 60 and calculates the center position as the coordinate position in the X-axis direction and the Y-axis direction. An arithmetic program for calculating this center position is stored in the ROM 55. For example, the center of gravity of the halo portion 36 can be determined from the outline of the halo portion 36 in FIG. Bye.
Once the center position of the halo portion 36 is determined in this manner, its coordinate data is stored at a predetermined location in the RAM 61. Note that the above-mentioned contour does not necessarily mean only the contour line, but may be any shape as long as the shape of the halo portion 36 can be specified.

In this way, the center position of the halo portion 36 is set to RAM6.
1, the MPU 41 stores the VRAM 59 based on the second threshold level signal.
The image data stored in the image data is binarized again. With this newly binarized data,
The image data in BRAM 60 is rewritten. Since the brightness level of this second threshold level signal is determined in accordance with the brightness of the core portion 35, the BRAM 60 stores data representing the shape of the core portion 35 at this point. Subsequently, the MPU 41 refers to the binarized data in the BRAM 60, repeats the same process as described above, determines the center position of the core portion 35, and stores this as coordinate data in a predetermined location in the RAM 61.

Through the above processing, the halo portion 36 and the core portion 3 are
After finding the center position of each of 5, MPU41
compares the respective center positions stored in the RAM 61. As already mentioned, when there is misalignment between the front group lens 24a and the rear group lens 24b, as shown in FIG. The difference between Δx and Δy appears. When the deviations of Δx and Δy are detected in this way, the MPU 41 causes the x table drive unit 46 and the y table drive unit 47 to set the deviations to values within predetermined management value ranges (ideally, each is “0”). Provides a drive signal. As a result, the rear group lens 24b is adjusted to move in the X-axis direction and the Y-axis direction together with the Y-table 8 so that eccentricity with respect to the front group lens 24a is reduced. In the process of this movement adjustment, for example, as shown in FIG.
a and the center position 35a of the core portion 35 are approaching each other. Note that the magnification of the microscope 12 is adjusted appropriately, and the x table 7 and the y table 8 are
The centering accuracy can be improved by expanding and adjusting the corrected movement amount of, for example, k=1.4 as Δx×k and Δy×k, respectively. Of course, the value of k will be set as appropriate depending on the configuration of the optical system to be subjected to centering processing.

When the above movement adjustment is performed and each value of Δx and Δy becomes a value within a predetermined control value range, the outlines of the halo portion 36 and the core portion 35 become circular as shown in FIG. center position 36a, 3
5a matches. In this state, each of the front group lens 24a and the rear group lens 24b is aligned without eccentricity, that is, the centering is completed, so it is necessary to tighten the screw 25 to join them together. The assembly of the photographic lens 24 is thus completed. Then, when an end signal is input from the keyboard 40, the X table 5 or Y table 6 is moved, and the photographic lens 24 is moved to the microscope 12.
Since it is moved to the retracted position from below, the adjusted photographic lens 24 is taken out and a new front group lens 24a and rear group lens 24b are set for the next adjustment.

In the example shown in FIG. 6, the respective center positions 35a and 36a also coincide with the center position of the screen, that is, the optical axis 3a of the light beam 30. However, the respective center positions 35a and 36a of the core portion 35 and the halo portion 36 are different from the optical axis 3a.
The center position of the screen does not need to be considered when matching these center positions 35a and 36a. Therefore, even at other positions outside the center position within the screen, the center positions 35a, 36
It is possible to match a.

However, when the front group lens 24a is set in the sleeve 6a, the set state is not necessarily constant. Therefore, when the X table 5 and Y table 6 are moved to the preset measurement start position, the optical axis center of the front group lens 24a may be shifted from the optical axis 3a of the light beam 30. .
If this deviation is too large, not only the core portion 35 but also the halo portion 36 will be affected.
The CCD 32 may not be able to capture the image. In such a case, a program for correcting the measurement start position stored in the ROM 55 is activated.
The X table 5 and the Y table 6 are adjusted to a position where the CCD 32 can capture the halo portion 36.

Furthermore, the position of the rear group lens 24b temporarily clamped by the clamp lever 8a is set to the position of the front group lens 24b.
If the halo portion 36 is largely eccentric with respect to 4a, the halo portion 36 will spread to the full extent of the imaging screen, making it impossible to specify its outline and center position, and furthermore, making it impossible to identify the core portion 35. In such a case, the Z-axis correction program stored in the ROM 55 is started, and the microscope 12 is moved in the Z-axis direction via the lift drive unit 43.
Reduce the defocus amount l. As the defocusing amount l decreases, the area of the halo portion 36 decreases and the core portion 35 also appears. Note that when executing this Z-axis correction program, the position of the microscope 12 is first adjusted to a position where the nuclear portion 35 is detected while referring to the image data stored in the VRAM 59. Thereafter, the microscope 12 will be positioned such that the outline of the halo portion 36 is obtained.

Whether or not the outline of the halo portion 36 can be obtained can be determined based on the area of the halo portion 36. That is, since the area of the halo portion 36 can be calculated from the image data stored in the VRAM 59, the Z-axis correction program may be repeated until the area value thus calculated falls within a predetermined range. Furthermore, even when the area value of the halo portion 36 is too small, the Z-axis correction program is executed so that this area value falls within the predetermined range. As a result, the halo part 3
6 and the core portion 35 are of appropriate size,
The deviation amounts Δx and Δy between the respective center positions can also be set to appropriate values that are easy to adjust.

In such a centering method, the front group lens 24a
There is an advantage that the optical axis of the light beam 30 does not necessarily have to coincide with the optical axis 3a of the light beam 30. That is, the data for performing centering adjustment are the center positions of the halo portion 36 and the core portion 35;
This has nothing to do with the position of the optical axis 3a of the light beam 30 or the optical axis of the front group lens 24a serving as a reference. That is, the halo portion 36 and the core portion 35
Since it is sufficient to capture each of them within the imaging plane of the CCD 32, the setting of the measurement start position becomes easy and can be completely automated as described above.

The present invention has been described above in accordance with the illustrated embodiment, but even if a point light source is placed at a constant object distance from the photographic lens 24, there will be a point light source above the focal point _P0 on the optical axis 3a. A point image is formed at a predetermined position. Therefore, even if the object point of the microscope 12 is set at a position away from this imaging position, centering can be performed using almost the same process, but when considering versatility and ease of processing,
It is also preferable to use the collimator lens 29 to generate a parallel light beam 30.

〔Effect of the invention〕

As explained above, according to the present invention, when centering at least one lens in a compound lens, the halo portion and the core portion formed at a position shifted from the focal plane of the compound lens in the optical axis direction are The centers of each image are obtained by capturing images and processing the images, and the centering is performed by keeping the deviation between these center positions within a predetermined control value range. There is. Therefore, it is possible to obtain images of the halo and core portions without having to precisely match the reference optical axis of the compound lens with the optical axis of the measurement light beam, which eliminates the need for conventional centering work. It is now possible to omit or completely automate focusing, optical axis alignment, etc., which are indispensable as pre-processing, and it is possible to perform centering efficiently and with satisfactory accuracy.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing an example of the apparatus of the present invention. FIG. 2 is a sectional view of a main part of the device shown in FIG. 1. FIG. 3 is a functional block diagram schematically showing the circuit configuration used in the device of FIG. 1. FIGS. 4 to 6 are explanatory diagrams showing changes in the halo portion and the core portion during the centering process. 1...Base, 2...Lamp, 5...X table, 6...Y table, 7...x table, 8...
...Y table, 12...Microscope, 13...Elevating mechanism, 14...Video camera, 24...Photo lens, 24a...Front group lens, 24b...Rear group lens, 35...Nuclear portion, 36... halo part.

Claims (1)

[Claims] 1. Centering of a complex lens in which at least one of a plurality of lenses constituting a complex lens with positive power is centered so that its optical axis coincides with the optical axis of the complex lens. In the method, after passing a light beam through the compound lens, the light beam is incident on a detection optical system disposed on the optical axis of the light beam, so that a low-intensity light is projected onto an imaging plane of the detection optical system. An image consisting of a halo portion and a high-intensity core portion is formed, and this image is captured by an imaging device to measure the center positions of the halo portion and the nucleus portion, respectively, and the amount of deviation between these center positions is determined. A method for centering a compound lens, characterized in that the at least one lens is moved in a plane perpendicular to an optical axis so that the value falls within a predetermined control value range. 2. Extracting a region with luminance above a predetermined level from the halo portion imaged by the imaging device, identifying the contour of the halo portion from this region, and determining the center position of the halo portion from the thus obtained contour. A method for centering a compound lens according to claim 1, characterized in that: 3. By moving the at least one lens Δx×k, Δy×k (where k is a positive number), where the amounts of deviation between the respective center positions are Δx and Δy, respectively, 2. The method for centering a compound lens according to claim 1, wherein the amount of deviation between the center positions of the two is kept within a predetermined control value range. 4 Calculate the area of the halo portion before measuring the center position of the halo portion, and when this area value is outside a predetermined range, move the detection optical system along the optical axis of the light beam. A method for centering a compound lens according to claim 1, characterized in that: 5. A first table that holds a reference lens among the composite lenses that have positive power as a whole;
a second table that movably holds at least one other lens of the compound lenses in a plane perpendicular to its optical axis; a light beam generating means for making the light beam incident on the compound lens; and an object disposed along the optical axis of the light beam and located away from the focal point of the light beam by the compound lens in the direction of the optical axis of the light beam. a detection optical system positioned so that the point is aligned; an imaging device that captures an image of the halo and the nucleus formed by the detection optical system; and an image calculation unit that determines the contours of the halo portion and the nucleus portion, and determines the respective center positions from the contours of the halo portion and the nucleus portion, and the respective center positions determined by the image calculation unit are made to coincide with each other. A compound lens centering device comprising: a table driving device for moving the second table. 6. The first table is movable in a plane perpendicular to the optical axis, and when the halo portion is not imaged by the imaging device, the first table is moved so that the halo portion is captured by the imaging device. 6. The centering device for a composite sash according to claim 5, wherein the centering device is adapted to be moved. 7. Claim 5, wherein the light beam generating means comprises a light source and a collimator lens that converts the light from the light source into a parallel light beam, and the parallel light beam is incident on the compound lens. Centering device for the compound lens described.