CN109862351B - Camera module resolution detection method - Google Patents
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- CN109862351B CN109862351B CN201910164033.2A CN201910164033A CN109862351B CN 109862351 B CN109862351 B CN 109862351B CN 201910164033 A CN201910164033 A CN 201910164033A CN 109862351 B CN109862351 B CN 109862351B
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Abstract
The invention relates to the field of camera module quality control, in particular to a camera module resolution inspection method, which comprises the following steps: A) setting a plurality of machine grabbing frames, and acquiring the MTF value of each grabbing frame; B) taking a plurality of camera module samples, and obtaining the resolution of the samples in each grabbing frame through manual test; C) obtaining the minimum resolution of a qualified sample, and taking the corresponding MTF value as the reference MTF value of each grabbing frame; D) and taking the camera module with each grabbing frame exceeding the corresponding reference MTF value as a qualified detection product by the machine. The substantial effects of the invention are as follows: through optimizing the position of grabbing the frame, make it only cover the test lines of single direction, reduce horizontal difference influence, through formulating reasonable reference value, improve the inspection accuracy.
Description
Technical Field
The invention relates to the field of quality control of camera modules, in particular to a method for testing the resolution of a camera module.
Background
The camera module is mainly applied to electronic terminal products such as mobile phones, tablet computers, unmanned aerial vehicles and medical treatment, and becomes an essential life article for people at present. Before the camera module leaves the factory, the resolution of the camera module needs to be checked to ensure that the camera module is qualified. The resolution test is an important means for ensuring and improving the quality of the camera module. The MTF value and the analytic value of the lens are both accurate measurement reflecting the lens analytic capability. The MTF values can be conveniently obtained automatically by a machine, and the resolution values need to be read manually. Generally, the qualified reference of the camera module is given in a resolution mode. Accurate resolution test requires human eyes to judge and read the scale value, and the value of the resolution can be read. The manual testing and inspection efficiency is low, and errors are easy to occur. Therefore, when the camera module resolution is inspected in a batch, the inspection is performed using MTF values substantially equivalent to the reference MTF values. The MTF value represents the rate of replication of the contrast at a certain fringe spatial frequency. The MTF value of a lens is a quantitative description of the resolution of the lens, specifically, the degree of clarity of imaging the lens, including two factors of resolution and sharpness. The MTF value is calculated by an existing calculation method using an image within a preset capture frame captured by the rack auto-processing camera module. When testing the MTF value of a Camera Module (Compact Camera Module, CCM), the test is generally performed in an optical box, a test Chart is attached to the top of the optical box, ISO12233 is usually used as the test Chart, the CCM is placed in a rack on a desktop at the bottom of the optical box, the desktop and the Chart are required to be parallel, a CCM image acquisition device is arranged in the rack, acquired image data is transmitted to a computer beside the rack by a data line, the acquired image is analyzed by test software on the computer, and the MTF value of the Camera Module is obtained through algorithm processing. In the current test of MTF value, the Chart center and each corner around each grabbing frame, and the machine judgment mode is the average value of H, V (horizontal and vertical) in the grabbing frame, which is easily affected by H, V difference. For example, taking the analysis requirement 1000 as an example, H: 1100, V: the system may also qualify 900. Resulting in some defective products in the qualified camera module inspected by the MTF value. The MTF value is a value in percentage and the resolution is a value with a direction mark. The MTF value is used for replacing the resolution value obtained manually, and the problem of reduced inspection accuracy is caused when the inspection is carried out. There is a need to find a camera module resolution batch inspection method that can filter more rejects.
Chinese patent CN101122544A, published 2008, 2/13, provides an MTF measurement system, an MTF measurement method, an MTF measurement device, and an MTF measurement program. The efficiency of the evaluation and measurement operation of the lens performance is improved. A lens performance evaluation method for an optical lens system includes the steps of generating measurement result screen data indicating an object image and an MTF curve image based on object image data acquired by imaging the object and MTF curve image data indicating an MTF curve generated from the MTF data as an index for evaluating lens performance, displaying a measurement result screen based on the generated measurement result screen data, and displaying the measurement result screen indicating the object image and the MTF curve image in real time when a lens performance evaluation measurement operation is performed. However, it cannot solve the problem that the MTF value is used instead of the resolution value obtained manually, and the inspection accuracy is lowered when the inspection is performed.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: the technical problem that the accuracy of the resolution batch test of the existing camera module is low is solved. A camera module resolution inspection method optimizing the grabbing frame selection and result judgment method is provided.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows: a camera module resolution detection method comprises the following steps: A) setting a plurality of machine grabbing frames, and acquiring the MTF value of each grabbing frame; B) taking a plurality of camera module samples, and obtaining the resolution of the samples in each grabbing frame through manual test; C) obtaining the minimum resolution of a qualified sample, and taking the corresponding MTF value as the reference MTF value of each grabbing frame; D) and taking the camera module with each grabbing frame exceeding the corresponding reference MTF value as a qualified detection product by the machine.
Preferably, the method for setting the plurality of machine grabbing frames comprises the following steps: the machine grabbing frame is set to be the same direction as the line covered by the single grabbing frame, the grabbing frames cover the direction of the line required by the test, and the line direction comprises the transverse direction, the longitudinal direction, the radial direction and the circumferential direction.
Preferably, the method for manually testing the resolution of the obtained sample comprises the following steps: B1) installing a camera module sample on a lighting instrument; B2) the shooting resolution test uses chart to obtain a shot picture; B3) the resolution value corresponding to each grab frame position is read manually.
Preferably, the method for obtaining the lowest resolution of the qualified sample comprises the following steps: C11) screening qualified products in the plurality of samples; C12) obtaining the lowest value of the resolution corresponding to each grabbing frame position in the qualified products; C13) and taking the MTF value obtained by the machine station corresponding to the lowest resolution value of each grabbing frame as the reference MTF value of the position of the grabbing frame.
Preferably, the method for obtaining the lowest resolution of the qualified sample comprises the following steps: C21) obtaining a resolution and MTF value data pair corresponding to each grabbing frame; C22) obtaining a fitting function of each captured MTF value to the resolution through fitting, wherein the fitting is linear fitting; C23) carrying out weighted average on fitting functions corresponding to the grabbing frames covering the lines in the same direction to obtain a final fitting function; C24) and substituting the resolution requirement value into the final fitting function of each grabbing frame to obtain the reference MTF value of each grabbing frame.
Preferably, the final fitting function M ═ n (j) is obtained by:
wherein M is MTF value, J is resolution value, N is the number of grabbing frames covering the same direction of the line, and N isiFor grabbing the fitting function corresponding to box i, ciFor the capture frame i, the sum of the resolution and the resolution in the MTF value data pair, C ═ C1+c2+…+cn。
The substantial effects of the invention are as follows: through optimizing the position of grabbing the frame, make it only cover the test lines of single direction, reduce horizontal difference influence, through formulating reasonable reference value, improve the inspection accuracy.
Drawings
Fig. 1 is a block diagram illustrating a method for checking resolution of a camera module according to an embodiment of the present invention.
Fig. 2 is a schematic view of the current position of the grab box.
FIG. 3 is a schematic diagram illustrating a position of a portion of the capture frame according to an embodiment.
Detailed Description
The following provides a more detailed description of the present invention, with reference to the accompanying drawings.
The first embodiment is as follows:
a method for checking resolution of a camera module, as shown in fig. 1, the embodiment includes the following steps: A) setting a plurality of machine grabbing frames, and acquiring the MTF value of each grabbing frame; B) taking a plurality of camera module samples, and obtaining the resolution of the samples in each grabbing frame through manual test; C) obtaining the minimum resolution of a qualified sample, and taking the corresponding MTF value as the reference MTF value of each grabbing frame; D) and taking the camera module with each grabbing frame exceeding the corresponding reference MTF value as a qualified detection product by the machine.
As shown in fig. 2, the current grabbing frame covers multiple directions of test lines, resulting in MTF being the synthesis, i.e. the average, of the camera module resolutions in each direction, which reduces the accuracy of the test. In this embodiment, the method for setting the plurality of machine-grabber frames includes: the machine grabbing frame is set to be the same direction as the line covered by the single grabbing frame, the grabbing frames cover the direction of the line required by the test, and the line direction comprises the transverse direction, the longitudinal direction, the radial direction and the circumferential direction. As shown in fig. 3, the areas covered by the grasping blocks B1 and B2 are transverse test lines, and the areas covered by the grasping blocks B9 and B10 are longitudinal test lines. According to the requirement of the test, a plurality of grabbing frames are added, so that all grabbing frames can cover all the line directions to be tested together. In this embodiment, a central grab box similar to the grab box B0 in fig. 2 is provided for grabbing the resolution in the circumferential direction, which is not shown in fig. 3.
The method for obtaining the resolution of the sample by manual test comprises the following steps: B1) installing a camera module sample on a lighting instrument; B2) the shooting resolution test uses chart to obtain a shot picture; B3) the resolution value corresponding to each grab frame position is read manually.
The method for obtaining the lowest resolution of qualified samples comprises the following steps: C11) screening qualified products in the plurality of samples; C12) obtaining the lowest value of the resolution corresponding to each grabbing frame position in the qualified products; C13) and taking the MTF value obtained by the machine station corresponding to the lowest resolution value of each grabbing frame as the reference MTF value of the position of the grabbing frame.
The method for obtaining the lowest resolution of qualified samples comprises the following steps: C21) obtaining a resolution and MTF value data pair corresponding to each grabbing frame; C22) obtaining a fitting function of each captured MTF value to the resolution through fitting, wherein the fitting is linear fitting; C23) carrying out weighted average on fitting functions corresponding to the grabbing frames covering the lines in the same direction to obtain a final fitting function; C24) and substituting the resolution requirement value into the final fitting function of each grabbing frame to obtain the reference MTF value of each grabbing frame.
The final fitting function M ═ n (j) is obtained by:
wherein M is MTF value, J is resolution value, N is the number of grabbing frames covering the same direction of the line, and N isiFor grabbing the fitting function corresponding to box i, ciFor the capture frame i, the sum of the resolution and the resolution in the MTF value data pair, C ═ C1+c2+…+cn. As shown in FIG. 3, the final fitting function in the transverse direction
Wherein c isH1Resolution value, c, manually read for grab Block B1H2Resolution values read manually for the grab Box B2, CH＝cH1+cH2，NH1(J) Fitting function, N, of linear fitting or quadratic difference fitting from the corresponding resolution and MTF value data pairs of the grab boxes B1 of several samplesH1(J) Fitting functions are fitted by linear fitting or quadratic difference fitting of the resolution and MTF value data pairs corresponding to the grab boxes B2 of several samples. And substituting the required resolution value into the final fitting function to obtain a corresponding MTF value, and after proper modification, rounding up and setting a reserved amount to be used as a reference MTF value of a corresponding grabbing frame B1 and a grabbing frame B2 for inspection. The reference MTF values for the remaining grab frame positions are analogized.
The above-described embodiments are only preferred embodiments of the present invention, and are not intended to limit the present invention in any way, and other variations and modifications may be made without departing from the spirit of the invention as set forth in the claims.
Claims (6)
1. A method for testing resolution of a camera module is provided,
the method comprises the following steps:
A) setting a plurality of machine grabbing frames, and acquiring the MTF value of each grabbing frame;
B) taking a plurality of camera module samples, and obtaining the resolution of the samples in each grabbing frame through manual test;
C) obtaining the minimum resolution of a qualified sample, and taking the corresponding MTF value as the reference MTF value of each grabbing frame;
D) taking the camera module with each grabbing frame exceeding the corresponding reference MTF value as a qualified product by the machine;
the method for obtaining the lowest resolution of qualified samples comprises the following steps:
C11) screening qualified products in the plurality of samples;
C12) obtaining the lowest value of the resolution corresponding to each grabbing frame position in the qualified products;
C13) and taking the MTF value obtained by the machine station corresponding to the lowest resolution value of each grabbing frame as the reference MTF value of the position of the grabbing frame.
2. The method for inspecting resolution of camera module according to claim 1,
the method for setting the plurality of machine grabbing frames comprises the following steps: the machine grabbing frame is set to be the same direction as the line covered by the single grabbing frame, the grabbing frames cover the direction of the line required by the test, and the line direction comprises the transverse direction, the longitudinal direction, the radial direction and the circumferential direction.
3. The method for inspecting resolution of camera module according to claim 1 or 2,
the method for obtaining the resolution of the sample by manual test comprises the following steps:
B1) installing a camera module sample on a lighting instrument;
B2) the shooting resolution test uses chart to obtain a shot picture;
B3) the resolution value corresponding to each grab frame position is read manually.
4. The method for inspecting resolution of camera module according to claim 1 or 2,
C21) obtaining a resolution and MTF value data pair corresponding to each grabbing frame;
C22) obtaining a fitting function of each captured MTF value to the resolution through fitting, wherein the fitting is linear fitting;
C23) carrying out weighted average on fitting functions corresponding to the grabbing frames covering the lines in the same direction to obtain a final fitting function;
C24) and substituting the resolution requirement value into the final fitting function of each grabbing frame to obtain the reference MTF value of each grabbing frame.
5. The method for inspecting resolution of camera module according to claim 3,
C21) obtaining a resolution and MTF value data pair corresponding to each grabbing frame;
C22) obtaining a fitting function of each captured MTF value to the resolution through fitting, wherein the fitting is linear fitting;
C23) carrying out weighted average on fitting functions corresponding to the grabbing frames covering the lines in the same direction to obtain a final fitting function;
C24) and substituting the resolution requirement value into the final fitting function of each grabbing frame to obtain the reference MTF value of each grabbing frame.
6. The method for inspecting resolution of camera module according to claim 5,
the final fitting function M ═ n (j) is obtained by:
wherein M is MTF value, J is resolution value, N is the number of grabbing frames covering the same direction of the line, and N isiFor grabbing the fitting function corresponding to box i, ciFor the capture frame i, the sum of the resolution and the resolution in the MTF value data pair, C ═ C1+c2+…+cn。
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| CN101063639A (en) * | 2006-04-28 | 2007-10-31 | 九骅科技股份有限公司 | Optical spatial frequency reaction amount measuring method |
| KR20090012612A (en) * | 2007-07-30 | 2009-02-04 | 김대봉 | Test chart for inspection apparatus of camera module |
| CN101557537A (en) * | 2009-04-20 | 2009-10-14 | 欧学平 | Method for automatically judging resolution |
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| NL9001265A (en) * | 1990-06-05 | 1992-01-02 | Philips Nv | METHOD FOR DETERMINING A MODULATION TRANSFER FUNCTION OF A DIGITAL IMAGING SYSTEM. |
| CN105025290B (en) * | 2014-04-23 | 2017-07-04 | 宁波舜宇光电信息有限公司 | A kind of inclined method between adjust automatically camera module sensor and camera lens |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101063639A (en) * | 2006-04-28 | 2007-10-31 | 九骅科技股份有限公司 | Optical spatial frequency reaction amount measuring method |
| KR20090012612A (en) * | 2007-07-30 | 2009-02-04 | 김대봉 | Test chart for inspection apparatus of camera module |
| CN101557537A (en) * | 2009-04-20 | 2009-10-14 | 欧学平 | Method for automatically judging resolution |
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Denomination of invention: A resolution test method for camera module Effective date of registration: 20220622 Granted publication date: 20200717 Pledgee: Dongyang Branch of China Construction Bank Co.,Ltd. Pledgor: HENGDIAN GROUP DMEGC JOINT-STOCK Co.,Ltd. Registration number: Y2022330001024 |
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