CN108931357B - Test target and corresponding lens MTF detection system and method - Google Patents
Test target and corresponding lens MTF detection system and method Download PDFInfo
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- CN108931357B CN108931357B CN201710364247.5A CN201710364247A CN108931357B CN 108931357 B CN108931357 B CN 108931357B CN 201710364247 A CN201710364247 A CN 201710364247A CN 108931357 B CN108931357 B CN 108931357B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
- G01M11/02—Testing optical properties
- G01M11/0242—Testing optical properties by measuring geometrical properties or aberrations
- G01M11/0257—Testing optical properties by measuring geometrical properties or aberrations by analyzing the image formed by the object to be tested
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
- G01M11/02—Testing optical properties
- G01M11/0207—Details of measuring devices
Abstract
The invention provides a test target, which comprises a target body; an MTF test pattern formed by a slit on the target body; and the distortion correction pattern is formed by a slit on the target body and is mutually staggered with the MTF test pattern, the distance between the center of the MTF test pattern and a first origin is equal to the distance between the center of the distortion correction pattern and a second origin, the first origin is used for aligning the optical axis of the lens to be tested in the MTF test, and the second origin is used for aligning the optical axis of the lens to be tested in the distortion correction test. The invention also provides a corresponding MTF test system and a corresponding MTF test method. The invention can integrate the targets with different functions required by detecting the MTF by a slit method into a whole, thereby saving the cost; the target can be installed in place at one time in the process of detecting the MTF, so that the convenience of operation is improved; and the lens compatibility to different EFLs is strong.
Description
Technical Field
The invention relates to the technical field of optical lens detection, in particular to a test target and a corresponding optical lens image detection method and system.
Background
With the continuous improvement of the performance of the photoelectric detector and the rapid development of the computer technology, the optical inspection lens is widely applied to an industrial automatic detection system, and the requirement on the imaging quality of the lens is higher and higher. MTF (Modulation Transfer Function) is a scientific method for analyzing the resolution of a lens at present, and has become an important index for evaluating an imaging system recognized by the industry.
Currently, many different types of MTF testers for industrial production testing and laboratory applications in colleges and universities and research institutions are available at home and abroad, such as the ImageMaster series tester manufactured by TROPTIC, Germany. The ImageMaster Pro tester is suitable for online MTF detection in large-batch production of small lenses.
The ImageMaster Pro tester calculates MTF information by collecting slit images. To acquire a slit image, a slit target a for MTF test is required, and fig. 1 shows an example of the slit target a. Since the off-axis field of view is distorted, an aberration correction target B for calculating an aberration correction coefficient is required in association with the slit target a, and fig. 2 shows an example of the aberration correction target B corresponding to the slit target a of fig. 1. When the MTF test is carried out, a distortion correction target B is installed in an ImageMasterPro tester to obtain distortion correction coefficients, then the distortion correction target B is taken down, a slit target A is installed at a corresponding position to carry out the MTF test, and finally all MTF values of different positions of different view fields are calculated by combining corresponding distortion correction coefficients.
The scheme for calculating the MTF information by collecting the slit image can realize large-batch online MTF detection, and has high test precision and good repeatability. However, this solution requires two targets to be processed to complete one MTF test, which increases the cost, and requires multiple targets to be installed during the test, which cannot be completed by one test. On the other hand, in this scheme, the distortion correction target also has a problem that it is not compatible with a lens having a large difference in EFL (Effective Focal Length). For example, for the distortion correction target B shown in fig. 2, when the EFL of the lens to be measured is too small, the image exceeds the image plane, so that the distortion correction coefficient cannot be calculated, and when the EFL is too large, the image is too small, which affects the accuracy of distortion correction.
Disclosure of Invention
The present invention aims to provide an MTF detection solution that overcomes at least one of the above-mentioned drawbacks of the prior art.
According to an aspect of the present invention, there is provided a test target, including a target body, and a first origin point arranged on the target body for aligning an optical axis of a lens to be tested in an MTF test, an MTF test pattern composed of slits, a second origin point for aligning the optical axis of the lens to be tested in a distortion correction test, and a distortion correction pattern composed of slits; a distance between a center of the MTF test pattern and a first origin is equal to a distance between a center of the distortion correction pattern and a second origin; the distortion correction pattern and the MTF test pattern are staggered in position.
In one embodiment, the MTF test pattern is a cross-slit.
In one embodiment, a double cross slit is arranged at the first origin position of the target body.
In one embodiment, the distortion correcting pattern is a square frame composed of slits.
In another embodiment, the distortion correction pattern is a frame formed by slits, wherein the frame comprises an outer frame and an inner frame, and the outer frame and the inner frame are respectively suitable for different lenses to be measured with different effective focal lengths. In one embodiment, the second origins include a first kind of second origin corresponding to a center of the outer frame and a second kind of second origin corresponding to a center of the inner frame, a distance from a center of the MTF test pattern to the corresponding first origin is equal to a distance from a center of the outer frame of the field frame corresponding to the MTF test pattern to the first kind of second origin corresponding to the field frame, and a distance from the center of the MTF test pattern to the corresponding first origin is also equal to a distance from a center of the inner frame of the field frame corresponding to the MTF test pattern to the second kind of second origin corresponding to the field frame.
In one embodiment, at least two MTF test patterns for performing MTF tests in at least two fields of view are disposed on the target body, and for any field of view, a distance from a center of the MTF test pattern for MTF test in the field of view to the first origin is not equal to a distance from a center of the MTF test pattern for MTF test in other fields of view to the first origin.
In one embodiment, at least two distortion correction patterns for performing distortion correction tests in at least two fields of view are further disposed on the target body, and for any field of view, the distance from the center of the distortion correction pattern for the distortion correction test in the field of view to the second origin is equal to the distance from the center of the corresponding MTF test pattern for the MTF test in the field of view to the first origin.
In one embodiment, there are a plurality of said MTF test patterns for MTF testing in the same field of view, and the centers of said MTF test patterns are distributed on a circle centered on the first origin.
In one embodiment, the second origin is a plurality of origins, and the positions of the second origins are mutually staggered.
In one embodiment, the at least two distortion correction patterns for performing the at least two in-view distortion correction tests are arranged such that a second origin corresponding to the distortion correction pattern in any one of the at least two views is offset from a second origin corresponding to the distortion correction pattern in the other at least two views.
In one embodiment, there are a plurality of the distortion correction patterns for the distortion correction test in the same field of view, and the centers of the distortion correction patterns are distributed on a circle with the same second origin as the center; or distributed on a plurality of circumferences with a plurality of second origin points at different positions as the center.
In one embodiment, at least two of the distortion correction patterns for at least two different in-view distortion correction tests share the same second origin.
In one embodiment, a line connecting the center of the MTF test pattern and the corresponding first origin is parallel to a line connecting the center of the distortion correction pattern corresponding to the MTF test pattern and the second origin corresponding to the distortion correction pattern. Therefore, in the MTF detection process, the optical path can be converted from the distortion correction test state to the MTF test state only by simply translating the lens to be detected.
According to another aspect of the present invention, there is also provided a lens MTF detection system using the target, including: the system comprises a light source, a test target, a lens to be tested and a camera group consisting of a plurality of cameras which are sequentially arranged along a light path; wherein the test target is the test target described above.
The light source, the test target and the camera are all fixed, and the lens to be tested can move to meet the test requirements of different positions.
According to another aspect of the present invention, there is provided a lens MTF detection method using the target, including the following steps:
1) changing the relative position of the lens to be tested and the test target, aligning the optical axis of the lens to be tested with a second origin on the test target, and testing the image of the distortion correction pattern on the test target to measure and calculate the distortion correction coefficient;
2) changing the relative position of the lens to be tested and the test target, enabling the optical axis of the lens to be tested to be aligned to the first original point on the test target, simultaneously acquiring images of MTF test patterns at different positions of different fields of view on the test target by the cameras distributed at different positions of different fields of view, and measuring and calculating to obtain all MTF values at different positions of different fields of view by combining corresponding distortion correction coefficients.
Wherein, when the test target includes at least two second origins corresponding to at least two fields of view or at least two distortion correction patterns, the step 1) further includes: sequentially changing the relative positions of the lens to be tested and the test target, sequentially and respectively aligning the optical axis of the lens to be tested with each second origin point on the test target, and measuring the image of each distortion correction pattern of each view field on the test target so as to measure and calculate the distortion correction coefficient of each distortion correction pattern under each view field; and after the distortion correction coefficients of all the distortion correction patterns are measured and calculated, executing the step 2).
Compared with the prior art, the invention has at least one of the following technical effects:
1. targets with different functions required by detecting MTF by a slit method can be integrated, and the cost is saved (about 50%).
2. In the process of detecting MTF, the target can be installed in place once without secondary replacement, and the convenience of operation is improved.
3. The same target can be used for measuring different lenses with EFL changing in a large range, and the compatibility is strong.
Drawings
Exemplary embodiments are illustrated in referenced figures of the drawings. The embodiments and figures disclosed herein are to be regarded as illustrative rather than restrictive.
Fig. 1 shows an example of a prior art slit target a for MTF testing;
fig. 2 shows an example of a prior art distortion correction target B corresponding to the slit target a of fig. 1;
FIG. 3 illustrates a test target for lens MTF detection provided in accordance with one embodiment of the present invention;
FIG. 4 illustrates a test target for lens MTF detection provided in accordance with another embodiment of the present invention;
fig. 5 illustrates a test target for lens MTF detection provided in accordance with yet another embodiment of the present invention;
FIG. 6 illustrates a test target for lens MTF detection provided in accordance with yet another embodiment of the present invention;
FIG. 7 illustrates a test target for lens MTF detection provided in accordance with yet another embodiment of the present invention;
FIG. 8 illustrates a test target for lens MTF detection provided in accordance with yet another embodiment of the present invention;
fig. 9 illustrates a lens MTF detection system provided in accordance with an embodiment of the present invention.
Detailed Description
For a better understanding of the present application, various aspects of the present application will be described in more detail with reference to the accompanying drawings. It should be understood that the detailed description is merely illustrative of exemplary embodiments of the present application and does not limit the scope of the present application in any way. Like reference numerals refer to like elements throughout the specification. The expression "and/or" includes any and all combinations of one or more of the associated listed items.
It should be noted that the expressions first, second, etc. in this specification are used only to distinguish one feature from another feature, and do not indicate any limitation on the features. Thus, the first lens discussed below may also be referred to as the second lens without departing from the teachings of the present application.
In the drawings, the thickness, size, and shape of the lens have been slightly exaggerated for convenience of explanation. In particular, the shapes of the spherical or aspherical surfaces shown in the drawings are shown by way of example. That is, the shape of the spherical surface or the aspherical surface is not limited to the shape of the spherical surface or the aspherical surface shown in the drawings. The figures are purely diagrammatic and not drawn to scale.
It will be further understood that the terms "comprises," "comprising," "includes," "including," "has," "including," and/or "including," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. Moreover, when a statement such as "at least one of" appears after a list of listed features, the entirety of the listed features is modified rather than modifying individual elements in the list. Furthermore, when describing embodiments of the present application, the use of "may" mean "one or more embodiments of the present application. Also, the term "exemplary" is intended to refer to an example or illustration.
As used herein, the terms "substantially," "about," and the like are used as terms of table approximation and not as terms of table degree, and are intended to account for inherent deviations in measured or calculated values that will be recognized by those of ordinary skill in the art.
Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present application will be described in detail below with reference to the embodiments with reference to the attached drawings.
Fig. 3 illustrates a test target for lens MTF detection provided in accordance with one embodiment of the present invention. In the embodiment shown in fig. 3, the test target includes a target body and 1 double cross slit 1, 8 cross slits 4 for 0.5 field test, 8 cross slits 5 for 0.7 field test, 1 distortion correction block 2 for 0.5 field test, and 1 distortion correction block 3 for 0.7 field test, which are disposed on the target body.
As shown in fig. 3, the double cross slit 1 is located at the approximate center of the target body, and both the cross slits 4 and 5 and the double cross slit 1 can transmit light. The distortion correction blocks 2 and 3 are a box-shaped structure composed of slits (i.e. the slits form the peripheral frames of the distortion correction blocks), and the slits composing the structure are light-permeable.
The 8 cross slits 4 for the 0.5 visual field test are distributed on a first circumference centered at a first origin o, and a radius R1 (which means a radius R1 of the first circumference) is set, and the radius R1 is a distance from the center of the cross slit 4 for the 0.5 visual field test to the first origin o. For example, the first origin o may be a center point of the double cross slit. The 8 cross slits 5 for the 0.7 field of view test are distributed on a second circumference centered on the first origin o, with a radius R2, which radius R2 is the distance from the center of the cross slit 5 for the 0.7 field of view test to the first origin. The specific size of the radii R1, R2 is determined by the test field of view.
The distortion correction block 2 for the 0.5 visual field test is positioned on an arc which takes a second origin a 6 as a circle center and has a radius of R1; the distortion correction block 3 for the 0.7 field test is located on an arc of radius R2 centered on another second origin b 7. In the present embodiment, the second origin a 6 and the second origin b 7 do not overlap with each other, the second origin a 6 does not overlap with the first origin o, and the second origin b 7 does not overlap with the first origin o.
In this embodiment, the 8 cross slits 4 for the 0.5 field test and the 8 cross slits 5 for the 0.7 field test are used to calculate the MTF of the lens to be tested, and the specific implementation method is as follows:
moving the lens to be measured to enable the optical axis (the optical axis is vertical to the target surface) of the lens to be measured to be aligned to the first origin o, and then collecting images of 8 cross slits 4 of 0.5 view field formed by the lens to be measured and images of 8 cross slits 5 of 0.7 view field formed by the lens to be measured by a camera;
the aberration correction block 2 under 0.5 field of view can be used to calculate the aberration correction coefficient for 0.5 field of view. For example, the lens to be measured is moved, so that the optical axis of the lens to be measured is perpendicular to the target surface and is aligned with the second origin a 6, and thus the camera can acquire an image of the distortion correction block 2 with the 0.5 view field formed by the lens to be measured, and further calculate the distortion correction coefficient of the 0.5 view field;
the 0.7-view lower distortion correction block 3 is used to calculate the distortion correction coefficient for the 0.7-view. For example, the lens to be measured is moved to make the optical axis of the lens to be measured perpendicular to the target surface and aligned with the second origin b 7, the camera acquires the image of the distortion correction block 3 of the 0.7 view field formed by the lens to be measured, and then the distortion correction coefficient of the 0.7 view field is calculated.
In this embodiment, a connection line between the center of the cross slit and the corresponding first origin point as the MTF test pattern is parallel to a connection line between the center of the distortion correction block corresponding to the cross slit and the second origin point corresponding to the distortion correction block. Therefore, in the MTF detection process, the optical path can be converted from the distortion correction test state to the MTF test state only by simply translating the lens to be detected. In addition, although in the embodiment, the optical axis of the lens to be tested is aligned with different original points on the target surface respectively by moving the lens to be tested, it can be understood that in other embodiments of the present invention, the optical axis of the lens to be tested is aligned with different original points on the target surface respectively by moving the target to change the relative position of the lens to be tested and the test target.
The function synthesis of this embodiment will distort the correction mark target and the target is tested to MTF is in same mark target, can practice thrift the cost greatly, improve the convenience of operation simultaneously.
It should be noted that the above-mentioned fields of view are not limited to two fields of view, i.e. 0.5 and 0.7, and other fields of view may be used in other embodiments, or more than two fields of view may be integrated; the number of the cross slits of each field of view is not limited to 8, as long as the plurality of cross slits are located on a circle with a certain first origin as a center (the radius of the circle is the radius of the target corresponding to the corresponding field of view). In other embodiments, the number of the aberration correcting blocks corresponding to each field of view is not limited to 1 (e.g., may be multiple), and the aberration correcting blocks do not coincide with the cross-shaped slit.
Fig. 4 shows a test target for lens MTF detection according to another embodiment of the present invention, the test target includes a target body and 1 double cross slit 1, 8 cross slits 4 for 0.5 field test, 8 cross slits 5 for 0.7 field test, 1 distortion correction frame 2 for 0.5 field test, and 1 distortion correction frame 3 for 0.7 field test, which are disposed on the target body. This embodiment is basically the same as the embodiment of fig. 3, except that a square-frame-shaped distortion correction pattern is used instead of a rectangular-frame-shaped distortion correction pattern. The rectangular distortion correction pattern is a rectangular frame formed by slits, and includes a large frame (referred to as an outer frame) forming the outer periphery and four small frames (referred to as inner frames) located inside. The outer frame is suitable for the lens to be tested with the large EFL, and the inner frame is suitable for the lens to be tested with the small EFL.
Since the frame shaped like a Chinese character 'tian' includes both the outer frame and the inner frame, the second origin in this embodiment is divided into two types, that is, the second origin corresponding to the center of the outer frame and the second origin corresponding to the center of the inner frame. Thus, the number of second origin points in the present embodiment is increased to four. The outer frame and the inner frame of the distortion correction frame 2 for the 0.5 field test correspond to a second origin a 6 and a second origin c 8, respectively, the center of the outer frame of the distortion correction frame 2 for the 0.5 field test is located on an arc with the second origin a 6 as the center of a circle and the radius of R1, and the center of a specific inner frame of the distortion correction frame for the 0.5 field test is located on an arc with the second origin c 8 as the center of a circle and the radius of R1. Similarly, the outer frame and the inner frame of the distortion correction frame 3 for the 0.7 visual field test correspond to the second origin b 7 and the second origin d 9, respectively, the center of the outer frame of the distortion correction frame 3 for the 0.7 visual field test is located on the circular arc with the second origin b 7 as the center and the radius R2, and the center of a specific inner frame of the distortion correction frame for the 0.7 visual field test is located on the circular arc with the second origin d 9 as the center and the radius R2.
During the distortion correction test, the optical axis of the lens to be tested is moved to align with the second origin a 6, so that the image of the outer frame of the field frame 2 for 0.5 field distortion correction can be acquired to adapt to the distortion correction of the lens to be tested with larger EFL; and moving the optical axis of the lens to be detected to align to a second origin c 8, so that the image of the specific inner frame in the field-shaped frame 2 for correcting the field distortion of 0.5 can be acquired to adapt to the distortion correction of the lens to be detected with a smaller EFL. Similarly, the image of the outer frame of the field frame 3 for 0.7 field distortion correction can be acquired by moving the optical axis of the lens to be measured to align with the second origin b 7, so as to adapt to the distortion correction of the lens to be measured with a large EFL, and the image of the specific inner frame in the field frame 3 for 0.7 field distortion correction can be acquired by moving the optical axis of the lens to be measured to align with the second origin d 9, so as to adapt to the distortion correction of the lens to be measured with a small EFL.
The distortion correction target and the MTF test target are synthesized, so that the cost can be greatly saved, the operation convenience is improved, and the compatibility of the target can be improved to a greater extent.
Fig. 5 shows a test target for lens MTF detection provided in accordance with yet another embodiment of the invention, which is substantially identical to the target of the embodiment of fig. 3 except for the number of distortion correction blocks and the corresponding number of second primitives.
In this embodiment, the number of the distortion correction blocks of 0.5 field of view is four, and the distortion correction blocks are respectively located in four directions of upper, lower, left and right of the center of the target, that is, the distortion correction block 21 of 0.5 field of view located above the center of the target, the distortion correction block 24 of 0.5 field of view located below the center of the target, the distortion correction block 22 of 0.5 field of view located left of the center of the target, and the distortion correction block 23 of 0.5 field of view located right of the center of the target. The total number of the aberration correction blocks of the 0.7 view field is four, and the aberration correction blocks are respectively positioned in the upper, lower, left and right directions of the center of the target (details are not repeated). The second origin is four in total, and the four origins respectively correspond to the distortion correction squares in the upper direction, the lower direction, the left direction and the right direction. The same second origin is shared by the distortion correction squares for the 0.5 field and the 0.7 field of view in the same direction. The distortion correction squares for the 0.5 field of view in the four directions of up, down, left and right are each located on a circle centered on the corresponding second origin and having a radius R1. The distortion correction squares for the 0.7 field of view in the four directions of up, down, left and right are each located on a circle centered on the corresponding second origin and having a radius R2.
Further, fig. 6 shows a test target for lens MTF detection provided in accordance with yet another embodiment of the present invention, which increases the distortion correction blocks of 0.5 field of view and 0.7 field of view to eight, which are respectively located in the eight directions of up, down, left, right, upper left, lower left, upper right, and lower right. Similar to the embodiment of fig. 5, the same orientation of the distortion correction squares for the 0.5 field and the 0.7 field share the same second origin. The distortion correction squares for the 0.5 field of view in the eight directions of up, down, left, right, left-up, left-down, right-up, and right-down are each located on a circle centered on the corresponding second origin and having a radius of R1. The distortion correction squares for the 0.7 field of view in the eight directions of up, down, left, right, left-up, left-down, right-up, and right-down are each located on a circle centered on the corresponding second origin and having a radius of R2. The specific location of the second origin is not shown in fig. 6 for the sake of neatness of the drawing.
In addition, in the above-described embodiment, when there are a plurality of the distortion correction patterns used for the distortion correction test under the same field of view, the centers of the distortion correction patterns are distributed on a plurality of circumferences centered on a plurality of second origin points at different positions. However, it will be readily understood by those skilled in the art that the centers of the distortion correction patterns may be distributed on a circle centered on the same second origin in other embodiments of the present invention.
Fig. 7 shows a test target for lens MTF detection according to another embodiment of the present invention, which is a deformation body obtained by replacing a distortion correction block (i.e., a square frame) with a field frame on the basis of the target of the embodiment of fig. 5. The specific method for replacing the frame with the square frame can refer to the description of the embodiment in fig. 4, and is not repeated here.
Fig. 8 shows a test target for lens MTF detection according to another embodiment of the present invention, which is a deformation body obtained by replacing the distortion correction block (i.e., square frame) with a field frame on the basis of the target of the embodiment of fig. 6. The specific method for replacing the frame with the square frame can refer to the description of the embodiment in fig. 4, and is not repeated here.
Further, fig. 9 shows a lens MTF detection system provided according to an embodiment of the present invention, the lens MTF detection system of the present embodiment includes: a light source 10, a test target 20, a lens 30 to be tested, and a camera group 40 composed of a plurality of cameras, which are sequentially arranged along an optical path. Wherein the light source 10 is used to illuminate the test target 20, typically stationary. Test target 20 is the test target of the embodiment of fig. 3. The slit on the target is imaged through the lens 30 to be measured after being transmitted. In the present embodiment, the test target 20 is usually fixed, and the lens 30 to be tested can move to meet the test requirements at different positions. Each camera of the camera set 40 is arranged corresponding to a test field of view for capturing an image of the slit. In this embodiment, the cameras are arranged in an umbrella shape, and each camera corresponds to one cross slit or two cross slits on the test target. The camera is typically stationary. It should be noted that, although in the present embodiment, the optical axis of the lens to be measured is aligned with different origins on the target surface by moving the lens to be measured, it is understood that in other embodiments of the present invention, the lens to be measured may be fixed, and the optical axis of the lens to be measured is aligned with different origins on the target surface by moving the target.
According to an embodiment of the present invention, there is further provided a lens MTF detection method based on the above detection system, including the following steps:
step 1: and moving the lens to be measured to enable the optical axis of the lens to be measured to be aligned to a second origin a on the test target, and collecting the image of the 0.5 view field square frame slit so as to measure and calculate the 0.5 view field distortion correction coefficient.
Step 2: moving the lens to be measured to enable the optical axis of the lens to be measured to be aligned to a second origin point b on the target, and collecting the image of the 0.7 view field square frame slit to measure and calculate a 0.7 view field distortion correction coefficient; it should be noted that in other embodiments, if there are multiple blocks for distortion correction on the same field of view, the same measurement and calculation may be performed; if other fields (such as 0.9 field) exist, the lens to be measured is moved and measured in the same way.
And step 3: after the coefficients of all the distortion correction blocks are measured and calculated, the lens to be measured is moved to enable the lens to be measured to be aligned to the first original point o on the target, the cameras distributed at different positions of different fields of view simultaneously acquire images of the cross slits at different positions of different fields of view, then the corresponding distortion correction coefficients (obtained in the steps 1 and 2) are combined, all MTF values at different positions of different fields of view are measured and calculated, and the test is finished.
While a series of embodiments of the present invention have been described above, it should be noted that the above embodiments are merely exemplary illustrations of the test targets of the present invention, and the test targets of the present invention are not limited to the above embodiments. For example, the cross slit may be replaced with other shapes of MTF test patterns composed of slits, and the square frame and the field frame may be replaced with other shapes of distortion correction patterns.
Claims (18)
1. A test target, comprising:
a target body;
an MTF test pattern formed by a plurality of slits on the target body, wherein the center of each slit in the plurality of slits of the MTF test pattern is distributed on a circumference with a first origin as a circle center; and
an aberration correction pattern formed by a slit on the target body and staggered from the MTF test pattern,
under the same field of view, the distance between the center of each slit in the plurality of slits of the MTF test pattern and a first origin is equal to the distance between the center of the distortion correction pattern corresponding to the slit and a second origin corresponding to the distortion correction pattern, the first origin is used for aligning the optical axis of the lens to be tested in the MTF test, and the second origin is used for aligning the optical axis of the lens to be tested in the distortion correction test.
2. The test target of claim 1, wherein at least two MTF test patterns for MTF testing in at least two fields of view are disposed on the target body, and for any field of view, a distance from a center of each of the plurality of slits of the MTF test pattern for MTF testing in that field of view to the first origin is not equal to a distance from a center of each of the plurality of slits of the MTF test pattern for MTF testing in the other fields of view to the first origin.
3. The test target according to claim 1 or 2, wherein at least two distortion correction patterns for performing at least two distortion correction tests under a field of view are further provided on the target body, and for any field of view, the distance from the center of the distortion correction pattern for the distortion correction test under the field of view to the second origin is equal to the distance from the center of each of the plurality of slits of the corresponding MTF test pattern for the MTF test under the field of view to the first origin.
4. The test target of claim 3, wherein there are a plurality of MTF test patterns for MTF testing in the same field of view, and the center of each of the plurality of slits of the MTF test patterns is distributed on a circle centered at the first origin.
5. The test target of claim 3, wherein the second origin is a plurality of origin points, and the locations of the second origin points are offset from one another.
6. The test target of claim 5, wherein the at least two distortion correction patterns for performing at least two in-view distortion correction tests have second origins that are offset from second origins that correspond to distortion correction patterns in other views.
7. The test target of claim 5, wherein there are a plurality of the aberration correction patterns for aberration correction testing under the same field of view, and the centers of the aberration correction patterns are distributed on a circle centered on the same second origin; or distributed on a plurality of circumferences with a plurality of second origin points at different positions as the center.
8. The test target of claim 3, wherein at least two of the distortion correction patterns for distortion correction testing of the same direction under at least two different fields of view share the same second origin.
9. The test target of any one of claims 1, 2, 4-8, wherein a line connecting a center of each of the plurality of slits of the MTF test pattern with the corresponding first origin is parallel to a line connecting a center of the distortion correction pattern corresponding to the MTF test pattern with the corresponding second origin.
10. The test target of any one of claims 1, 2, 4 to 8, wherein the MTF test pattern is a cross slit.
11. The test target of any one of claims 1, 2, 4-8, wherein a double cross slit is provided at the first origin position of the target body.
12. The test target of any one of claims 1, 2, 4 to 8, wherein the distortion correction pattern is a square frame of slits or a field frame of slits.
13. The test target of claim 12, wherein the frame comprises an outer frame and an inner frame, the outer frame and the inner frame being adapted for different lenses to be tested having different effective focal lengths, respectively.
14. The test target of claim 13,
the second origin points include a first kind of second origin point corresponding to the center of the outer frame and a second kind of second origin point corresponding to the center of the inner frame,
the distance from the center of each slit in the plurality of slits of the MTF test pattern to the corresponding first origin is equal to the distance from the center of the outer frame of the field frame corresponding to the MTF test pattern to the first origin of the first kind corresponding to the field frame,
the distance from the center of each slit in the plurality of slits of the MTF test pattern to the corresponding first origin is equal to the distance from the center of the inner frame of the field frame corresponding to the MTF test pattern to the second origin of the second type corresponding to the field frame.
15. A lens MTF detection system, comprising: the system comprises a light source, a test target, a lens to be tested and a camera group consisting of a plurality of cameras which are sequentially arranged along a light path; characterized in that the test target is a test target according to any one of claims 1 to 14.
16. The MTF detection system of claim 15, wherein the light source, test target, and camera are stationary, and the lens under test is movable to accommodate testing needs at different positions.
17. A lens MTF detection method based on any one of the test targets 1 to 14, comprising:
1) changing the relative position of the lens to be measured and the test target, aligning the optical axis of the lens to be measured with the second origin on the test target, and collecting the image of the distortion correction pattern on the test target formed by the lens to be measured so as to measure and calculate the distortion correction coefficient; and
2) changing the relative position of the lens to be measured and the test target, enabling the optical axis of the lens to be measured to be aligned to the first origin point on the test target, simultaneously collecting images of MTF test patterns at different positions of different fields of view on the test target through the lens to be measured by cameras distributed at different positions of different fields of view, and measuring and calculating to obtain all MTF values at different positions of different fields of view by combining with the corresponding distortion correction coefficients.
18. The method of claim 17, wherein when the test target includes at least two second origins corresponding to at least two fields of view or at least two distortion correction patterns, the step 1) further comprises:
and sequentially changing the relative position of the lens to be measured and the test target to ensure that the optical axis of the lens to be measured is sequentially and respectively aligned to each second origin point on the test target, wherein the image of each distortion correction pattern of each view field on the test target is acquired through the lens to be measured so as to calculate the distortion correction coefficient of each distortion correction pattern under each view field.
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| DE102020125064A1 (en) | 2020-09-25 | 2022-03-31 | Trioptics Gmbh | MTF test device and its use |
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| CN113064247A (en) * | 2021-03-29 | 2021-07-02 | 南昌欧菲光电技术有限公司 | Multi-lens group shooting lens correction method and detection system |
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