CN115314688A - Focal length measuring method and device of DMD projection system and storage medium - Google Patents
Focal length measuring method and device of DMD projection system and storage medium Download PDFInfo
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- CN115314688A CN115314688A CN202210933658.2A CN202210933658A CN115314688A CN 115314688 A CN115314688 A CN 115314688A CN 202210933658 A CN202210933658 A CN 202210933658A CN 115314688 A CN115314688 A CN 115314688A
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- 238000000034 method Methods 0.000 title claims abstract description 37
- 238000003384 imaging method Methods 0.000 claims abstract description 17
- 238000012545 processing Methods 0.000 claims description 9
- 238000005259 measurement Methods 0.000 claims description 7
- 238000004590 computer program Methods 0.000 claims description 3
- 238000012360 testing method Methods 0.000 description 4
- 238000004364 calculation method Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000000691 measurement method Methods 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000000945 filler Substances 0.000 description 1
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N9/00—Details of colour television systems
- H04N9/12—Picture reproducers
- H04N9/31—Projection devices for colour picture display, e.g. using electronic spatial light modulators [ESLM]
- H04N9/3191—Testing thereof
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
- G03B21/00—Projectors or projection-type viewers; Accessories therefor
- G03B21/005—Projectors using an electronic spatial light modulator but not peculiar thereto
- G03B21/008—Projectors using an electronic spatial light modulator but not peculiar thereto using micromirror devices
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T7/00—Image analysis
- G06T7/0002—Inspection of images, e.g. flaw detection
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T2207/00—Indexing scheme for image analysis or image enhancement
- G06T2207/30—Subject of image; Context of image processing
- G06T2207/30168—Image quality inspection
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- Quality & Reliability (AREA)
- Computer Vision & Pattern Recognition (AREA)
- Theoretical Computer Science (AREA)
- Multimedia (AREA)
- Signal Processing (AREA)
- Length Measuring Devices By Optical Means (AREA)
Abstract
The invention discloses a focal length measuring method, a focal length measuring device and a storage medium of a DMD projection system, wherein the method comprises the following steps: s1, a camera is arranged below a DMD projection system, so that an image projected by the DMD projection system constantly falls into an imaging area of the camera within a preset height range; s2, performing image projection through the DMD projection system to form a projection image in an imaging area of the camera; s3, moving the camera from an initial position to a final position along the Z-axis direction, and shooting images of the camera at preset step length intervals in the moving process to obtain a plurality of captured images based on the projected images at different heights; s4, analyzing the picture quality of each captured picture; s5, obtaining the optimal focal length of the DMD projection system according to the analysis result; the focal length measuring process is simple and high in precision, and the method is suitable for obtaining the optimal focal length for the DMD projection system.
Description
Technical Field
The invention relates to the technical field of DMD projection, in particular to a focal length measuring method, a focal length measuring device and a focal length measuring storage medium of a DMD projection system.
Background
The digital micromirror DMD is an important component of the LDI optical system of a pcb exposure apparatus. The DMD is made up of many small-sized aluminum reflecting mirrors, each mirror can deflect + 12 °, 0 °, 12 ° around the diagonal of each small mirror in positive direction. In the working process, the input light is reflected and output to the imaging system through the micro mirror surface, and the output light can be ensured to be focused on the imaging plane.
The DMD projection system with poor focusing may cause problems of large line width and line distance, non-uniformity of energy, energy loss, and blurring of the image pattern on the image plane, and thus it is necessary to ensure that the focal plane of the DMD projection system is highly consistent with the image plane, and to ensure the normal operation of the optical system.
However, the DMD projection system is limited by the prior art, and the focal length process of the DMD projection system is complicated, and the measurement accuracy is poor, so that the DMD projection system requirement with higher quality cannot be satisfied.
Disclosure of Invention
The invention aims to provide a focal length measuring method, a focal length measuring device and a storage medium of a DMD projection system, which have simple focal length measuring process and high precision and are suitable for obtaining the optimal focal length for the measurement of the DMD projection system.
In order to achieve the above object, the present invention discloses a focal length measuring method for a DMD projection system, which comprises the following steps:
s1, a camera is arranged below a DMD projection system, so that an image projected by the DMD projection system constantly falls into an imaging area of the camera within a preset height range;
s2, performing image projection through the DMD projection system to form a projection image in an imaging area of the camera;
s3, moving the camera from an initial position to an end position along the Z-axis direction, and in the moving process, enabling the camera to carry out image shooting at preset step length intervals so as to obtain a plurality of captured pictures based on the projected images at different heights;
s4, analyzing the picture quality of each captured picture;
and S5, obtaining the optimal focal length of the DMD projection system according to the analysis result.
Preferably, in the step S3, the step of taking images by the camera at preset intervals to obtain a plurality of captured images based on the projected image at different heights includes:
and when the camera moves for a preset step length at intervals, taking the preset position of the projected image as a shooting focus to shoot images so as to obtain a plurality of captured pictures based on the projected image under different heights.
Preferably, the preset position is an upper left corner, a lower left corner, a center position, an upper right corner or a lower right corner of the projected image.
Preferably, the picture quality is edge sharpness of the captured image.
Preferably, the step S4 specifically includes:
s41, respectively carrying out image processing on each captured image to obtain the gray gradient values of all pixels of each captured image;
s42, calculating the variance of the gray gradient values between adjacent pixels under the same captured image;
and S43, representing the edge sharpness of the currently captured image by the variance of the gray gradient values between adjacent pixels.
Preferably, the step S5 specifically includes:
s51, arranging the variances of the gray gradient values between adjacent pixels under all captured images from small to large in sequence;
s52, selecting a captured image with the minimum variance of the gray gradient values between adjacent pixels;
and S53, marking the distance between the camera corresponding to the captured image and the lens of the DMD projection system as the optimal focal length of the DMD projection system.
Preferably, when the projected image is a fill pattern, the micromirrors of the DMD projection system are controlled to light at intervals.
Preferably, the height value of the initial position is greater than or equal to the minimum value of the preset height range, and the height value of the end position is less than or equal to the maximum value of the preset height range.
Correspondingly, the invention also discloses a focal length measuring device of the DMD projection system, which comprises:
a DMD projection system;
the camera is arranged below the DMD projection system, so that an image projected by the DMD projection system constantly falls into an imaging area of the camera within a preset height range;
the first execution module is used for carrying out image projection through the DMD projection system so as to form a projection image in an imaging area of the camera;
the second execution module is used for moving the camera from an initial position to an end position along the Z-axis direction, and in the moving process, enabling the camera to carry out image shooting at preset step length intervals so as to obtain a plurality of captured pictures based on the projected images at different heights;
a first processing module for analyzing the picture quality of each captured picture;
and the second processing module is used for obtaining the optimal focal length of the DMD projection system according to the analysis result.
Accordingly, the present invention also discloses a storage medium for storing a computer program, characterized in that: the program when executed by a processor implements the focal length measurement method of the DMD projection system as described above.
Compared with the prior art, the method has the advantages that the camera is moved from the initial position to the end position along the Z-axis direction, in the moving process, the camera is made to carry out image shooting at preset step length intervals to obtain a plurality of captured pictures based on the projected images under different heights, the optimal focal length of the DMD projection system is obtained by analyzing the picture quality of each captured picture and according to the analysis result, the focal length measuring process is simple, the precision is high, and the method is suitable for obtaining the optimal focal length for the DMD projection system.
Drawings
FIG. 1 is a block flow diagram of a method for focal length measurement of a DMD projection system of the present invention;
FIG. 2 is a schematic view of the projected image of the present invention as a conventional graphic;
FIG. 3 is a focal plane test result of the present invention;
FIG. 4 is a schematic view of the projected image of the present invention as a fill pattern;
FIG. 5 is the focal plane test results of the present invention.
Detailed Description
In order to explain technical contents, structural features, and objects and effects of the present invention in detail, the following detailed description is given with reference to the accompanying drawings in conjunction with the embodiments.
Referring to fig. 1-5, a method for measuring a focal length of a DMD projection system of the present embodiment includes the following steps:
s1, a camera is arranged below a DMD projection system, so that an image projected by the DMD projection system constantly falls into an imaging area of the camera within a preset height range.
It is understood that the lens of the DMD projection system is comprised of a plurality of spaced micromirrors. The image projected by the DMD projection system in a normal situation is a regular pattern composed of a plurality of tiny squares spaced black and white as shown in fig. 3.
And S2, carrying out image projection through the DMD projection system so as to form a projection image in an imaging area of the camera.
And S3, moving the camera from the initial position to the end position along the Z-axis direction, and shooting images by the camera at preset step length intervals in the moving process to obtain a plurality of captured images based on the projected images at different heights.
And S4, analyzing the picture quality of each captured picture.
And S5, obtaining the optimal focal length of the DMD projection system according to the analysis result.
Preferably, in step S3, the step of taking images by the camera at preset intervals to obtain a plurality of captured images based on the projected images at different heights includes:
and when the camera moves for a preset step length at intervals, taking the preset position of the projected image as a shooting focus to shoot images so as to obtain a plurality of captured pictures based on the projected image at different heights.
It can be understood that the preset step length of this embodiment may be different values such as 0.01mm, 0.02mm, 0.1mm, 1mm, and the specific value of the preset step length needs to be set according to the type of the DMD projection system and the imaging requirement, which is not limited herein.
Preferably, the preset position is an upper left corner, a lower left corner, a center position, an upper right corner or a lower right corner of the projected image.
It can be understood that, in this embodiment, each step is executed with any one of the preset positions as a focus, and the obtained optimal focal distance is based on the current preset position, and actually, in order to allow an operator to better judge whether the focal plane of the DMD projection system is in a leveling state, the optimal focal distance at the preset position may be respectively calculated with the upper left corner, the lower left corner, the central position, the upper right corner, or the lower right corner as a focusing object, so that the operator refers to whether the focal plane of the DMD projection system is in a leveling state, thereby facilitating the operator to better adjust the focal plane of the DMD projection system.
Preferably, the picture quality is edge sharpness of the captured image.
Preferably, the step S4 specifically includes:
s41, respectively carrying out image processing on each captured image to obtain the gray gradient value of all pixels of each captured image;
s42, calculating the variance of the gray gradient values between adjacent pixels under the same captured image;
and S43, representing the edge sharpness of the currently captured image by the variance of the gray gradient values between adjacent pixels.
Preferably, the step S5 specifically includes:
s51, arranging the variances of the gray gradient values between adjacent pixels under all captured images from small to large in sequence;
s52, selecting a captured image with the minimum variance of the gray gradient values between adjacent pixels;
and S53, marking the distance between the camera corresponding to the captured image and the lens of the DMD projection system as the optimal focal length of the DMD projection system.
Fig. 2 shows the focal plane test results at different heights obtained by the focal length measuring method of the DMD projection system of the present embodiment, and it can be seen from the curve in the figure that the lowest position of the curve is the optimal focal length.
Preferably, when the projected image is a fill pattern, the micromirrors of the DMD projection system are controlled to light at intervals.
It will be appreciated that due to the gaps between the micromirrors of the DMD, the image out of focus and the image in focus will vary greatly as shown in fig. 4. In the conventional method, the contour and the area of the contour of a projected closed image are obtained for calculation, and the calculation result is unstable under the influence of the micro-mirror gap. In order to reduce the influence of the micromirror gap, the micromirrors of the DMD projection system are controlled to light at intervals so that the filler image can obtain the photographing effect of the conventional pattern as shown in fig. 2, thereby reducing the influence of the micromirror gap of the DMD on the projected image. Fig. 5 shows a measurement result chart based on image quality after the micromirrors of the DMD projection system are lit at intervals, which has a relatively stable measurement curve, and the stability of the result of repeated measurement reaches 0.02mm, effectively meeting the test requirements.
Preferably, the height value of the initial position is greater than or equal to the minimum value of the preset height range, and the height value of the end position is less than or equal to the maximum value of the preset height range.
It should be noted that the picture quality in this embodiment is the edge sharpness of the captured image, focal lengths of the DMD projection system at different heights are analyzed through the edge sharpness of the captured image, and in other preferred manners, the picture quality may also be represented through image parameters such as an exposure rate, a resolution, a contrast, and the like of the captured image, and at this time, the specific analysis step of the picture quality needs to be adaptively adjusted, which is not described herein again.
Correspondingly, the invention also discloses a focal length measuring device of the DMD projection system, which comprises:
a DMD projection system;
the camera is arranged below the DMD projection system, so that an image projected by the DMD projection system constantly falls into an imaging area of the camera within a preset height range;
the first execution module is used for carrying out image projection through the DMD projection system so as to form a projection image in an imaging area of the camera;
the second execution module is used for moving the camera from an initial position to an end position along the Z-axis direction, and in the moving process, enabling the camera to carry out image shooting at preset step length intervals so as to obtain a plurality of captured pictures based on the projected images at different heights;
a first processing module for analyzing the picture quality of each captured picture;
and the second processing module is used for obtaining the optimal focal length of the DMD projection system according to the analysis result.
Accordingly, the present invention also discloses a storage medium for storing a computer program, which is characterized in that: the program when executed by a processor implements the focal length measurement method of the DMD projection system as described above.
With reference to fig. 1-5, the present invention moves the camera from the initial position to the end position along the Z-axis direction, and in the moving process, the camera performs image shooting at preset step lengths to obtain a plurality of captured images based on the projected image at different heights, and obtains the optimal focal length of the DMD projection system by analyzing the image quality of each captured image and according to the analysis result, and the focal length measuring process is simple and highly accurate, and is suitable for obtaining the optimal focal length for the DMD projection system.
The above disclosure is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the scope of the present invention, therefore, the present invention is not limited by the appended claims.
Claims (10)
1. A focal length measuring method of a DMD projection system is characterized by comprising the following steps:
the camera is arranged below the DMD projection system, so that an image projected by the DMD projection system constantly falls into an imaging area of the camera within a preset height range;
performing image projection by the DMD projection system to form a projected image in an imaging area of the camera;
moving the camera from an initial position to an end position along the Z-axis direction, and shooting images of the camera at intervals of preset step length in the moving process to obtain a plurality of captured images based on the projected images at different heights;
analyzing the picture quality of each captured picture;
and obtaining the optimal focal length of the DMD projection system according to the analysis result.
2. The method according to claim 1, wherein the moving the camera from an initial position to an end position along the Z-axis direction, and during the moving, the camera performs image capturing at preset steps to obtain a plurality of captured images based on the projected image at different heights, and the camera performs image capturing at preset steps to obtain a plurality of captured images based on the projected image at different heights, specifically comprises:
and when the camera moves for a preset step length at intervals, taking the preset position of the projected image as a shooting focus to shoot images so as to obtain a plurality of captured pictures based on the projected image under different heights.
3. The method of claim 2, wherein the predetermined position is an upper left corner, a lower left corner, a center position, an upper right corner, or a lower right corner of the projected image.
4. The method of claim 1, wherein the picture quality is edge sharpness of the captured image.
5. The method according to claim 4, wherein the analyzing the picture quality of each captured picture comprises:
respectively carrying out image processing on each captured image to obtain the gray gradient value of all pixels of each captured image;
calculating the variance of the gray gradient values between adjacent pixels under the same captured image;
the edge sharpness of the currently captured image is characterized by the variance of the gray scale gradient values between adjacent pixels.
6. The method according to claim 1, wherein the obtaining the optimal focal length of the DMD projection system according to the analysis result comprises:
arranging the variances of the gray gradient values between adjacent pixels under all captured images from small to large in sequence;
selecting a captured image with the minimum variance of the gray gradient values between adjacent pixels;
marking the distance between the camera corresponding to the captured image and the lens of the DMD projection system as the optimal focal length of the DMD projection system.
7. The method according to claim 1, wherein when the projected image is a fill pattern, the micromirrors of the DMD projection system are controlled to be lit at intervals.
8. The method of claim 1, wherein the height of the initial position is greater than or equal to the minimum of the predetermined height range, and the height of the final position is less than or equal to the maximum of the predetermined height range.
9. A focal length measuring device for a DMD projection system, comprising:
a DMD projection system;
the camera is arranged below the DMD projection system, so that an image projected by the DMD projection system constantly falls into an imaging area of the camera within a preset height range;
the first execution module is used for carrying out image projection through the DMD projection system so as to form a projection image in an imaging area of the camera;
the second execution module is used for moving the camera from an initial position to an end position along the Z-axis direction, and in the moving process, enabling the camera to carry out image shooting at preset step length intervals so as to obtain a plurality of captured pictures based on the projected images at different heights;
a first processing module for analyzing the picture quality of each captured picture;
and the second processing module is used for obtaining the optimal focal length of the DMD projection system according to the analysis result.
10. A storage medium for storing a computer program, characterized in that: the program, when executed by a processor, implements a method of focal length measurement for a DMD projection system as recited in any one of claims 1-8.
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| CN109698946A (en) * | 2017-10-24 | 2019-04-30 | 深圳市Tcl高新技术开发有限公司 | Projection device Atomatic focusing method, projection device and computer readable storage medium |
| US20190253677A1 (en) * | 2016-06-14 | 2019-08-15 | Zte Corporation | Method and projector for adjusting projected image |
| CN113497925A (en) * | 2020-04-02 | 2021-10-12 | 深圳光峰科技股份有限公司 | Projection focusing method and projection focusing device |
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- 2022-08-04 CN CN202210933658.2A patent/CN115314688A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20190253677A1 (en) * | 2016-06-14 | 2019-08-15 | Zte Corporation | Method and projector for adjusting projected image |
| CN109698946A (en) * | 2017-10-24 | 2019-04-30 | 深圳市Tcl高新技术开发有限公司 | Projection device Atomatic focusing method, projection device and computer readable storage medium |
| CN108267299A (en) * | 2017-12-22 | 2018-07-10 | 歌尔股份有限公司 | AR glasses interpupillary distance test methods and device |
| CN113497925A (en) * | 2020-04-02 | 2021-10-12 | 深圳光峰科技股份有限公司 | Projection focusing method and projection focusing device |
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