CN110864878A - Method for detecting display distortion of high-efficiency large-view-field flat display system - Google Patents
Method for detecting display distortion of high-efficiency large-view-field flat display system Download PDFInfo
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- CN110864878A CN110864878A CN201910970734.5A CN201910970734A CN110864878A CN 110864878 A CN110864878 A CN 110864878A CN 201910970734 A CN201910970734 A CN 201910970734A CN 110864878 A CN110864878 A CN 110864878A
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- G—PHYSICS
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- 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
- G01M11/0264—Testing optical properties by measuring geometrical properties or aberrations by analyzing the image formed by the object to be tested by using targets or reference patterns
Abstract
The invention relates to a method for detecting display distortion of a high-efficiency large-view-field head-up display system, which adopts a digital image processing technology to detect and process the display distortion of a large-view-field head-up display optical system at a sub-pixel level, and eliminates the self measurement error of a camera through a bilinear interpolation algorithm, thereby improving the detection efficiency and the accuracy of the detection and correction of the display distortion. The technical support is provided for assembly debugging and batch production of the large-view-field head-up display optical system. The advantages are that: the image coordinates are converted into angle coordinates through a bilinear interpolation algorithm to eliminate the self measurement error of the camera, meanwhile, the processing flow of the display distortion is combed, and the automatic processing of the display distortion can be realized by means of a computer software technology.
Description
Technical Field
The invention belongs to the technical field of optical system calibration, and relates to a method for detecting display distortion of a high-efficiency large-view-field flat display system.
Background
The head-up display optical system is a collimating optical system, the display picture of an image source is placed on the effective focal plane of the optical system, the light rays emitted from the image surface are converted into a beam of parallel light through the optical system, and the human eyes feel that the parallel light comes from infinity when observing the parallel light.
Distortion is aberration caused by the difference in lateral magnification of images corresponding to different regions of the object plane. The large-view-field head-up display system is used as a complex off-axis visual system, the generation of display distortion is a complex systematic problem, and various links such as an optical principle, system design, hardware processing, assembly debugging and the like are involved, and a display picture needs to be corrected.
The traditional display distortion processing only processes the design distortion of an optical system or manually calibrates a display picture in a grid mode. The two methods have low accuracy in processing the display distortion, are time-consuming and labor-consuming, and are not suitable for large-scale mass production of large-view-field head-up display systems.
Disclosure of Invention
Technical problem to be solved
In order to avoid the defects of the prior art, the invention provides a method for efficiently detecting the display distortion of a large-view-field head-up display system. The technical support is provided for assembly debugging and batch production of the large-view-field head-up display optical system.
Technical scheme
A method for detecting display distortion of a high-efficiency large-view-field flat display system is characterized by comprising the following steps:
step 1: the method comprises the following steps that a waveguide display module distortion test system is adopted, a bracket is adjusted to adjust the collimator tube, a waveguide display module and a camera to be coaxial, the camera shoots a reference image with a scale grid in the collimator tube through the waveguide display module, then the waveguide display module is electrified and a test picture is input, and the camera shoots a display image with distortion on the waveguide display module;
step 2: respectively carrying out digital enhancement processing on the reference image with the scale grids and the display image with distortion acquired in the step 1 by adopting an image digital enhancement method;
step 3, establishing a mapping relation between the angle coordinate and the image coordinate: on a reference image, the angle coordinates of the intersections of the longitudinal lines and the transverse lines of the scale grids are known, and the angle coordinates of each intersection and the image coordinates are in one-to-one correspondence by adopting a two-dimensional sorting algorithm from top to bottom and from left to right; calculating the sub-pixel level image coordinates of the cross points by adopting a feature detection algorithm;
step 4, resolving the actual angle coordinate of the light spot on the display image: on the displayed image, resolving the sub-pixel level image coordinates of the center of each light spot by adopting a light spot detection algorithm, and converting the image coordinates of the light spots into angle coordinates by adopting a bilinear interpolation algorithm according to the mapping relation between the angle coordinates and the image coordinates in the step 3;
and 5: the actual angle coordinate of the light spot on the display image calculated by the step 4 is a distortion point coordinate, the angle coordinate of the light spot on the test picture in the step 1 is an ideal point coordinate, a two-dimensional sequencing algorithm from top to bottom and from left to right is adopted to establish the corresponding relation between the distortion point and the ideal point, and waveguide display distortion correction parameter calculation is carried out according to the distribution conditions of the ideal point and the distortion point;
step 6: and 5, performing display distortion correction on the input picture of the waveguide display module by adopting the distortion correction parameters obtained in the step 5, and comparing and verifying the display image through a collimator.
The image digital enhancement is a maximum between-class variance method and a morphology processing method.
The feature detection algorithm is cross point edge detection or light spot detection.
Advantageous effects
The invention provides a method for efficiently detecting display distortion of a large-field-of-view head-up display system, which aims at the key problem of detection and correction of display distortion of a large-field-of-view head-up display optical system. The invention adopts the digital image processing technology to detect and process the display distortion of the large-view-field head-up display optical system at a sub-pixel level, and eliminates the self measurement error of the camera through a bilinear interpolation algorithm, thereby not only improving the detection efficiency, but also improving the accuracy of the detection and correction of the display distortion. The technical support is provided for assembly debugging and batch production of the large-view-field head-up display optical system.
The invention has the advantages that: the invention adopts a digital image processing technology to detect and process the display distortion of a large-view-field head-up display optical system at a sub-pixel level, converts image coordinates into angle coordinates through a bilinear interpolation algorithm to eliminate the self measurement error of a camera, simultaneously combs the processing flow of the display distortion, and can realize the automatic processing of the display distortion by means of a computer software technology. The technical support is provided for assembly debugging and batch production of the large-view-field head-up display optical system.
Drawings
FIG. 1: high-efficiency large-view-field flat display system display distortion detection process
FIG. 2: schematic diagram of waveguide display module distortion testing system
FIG. 3: digitally enhanced reference and display images
a: scale lines on the reference image; b: spots on the displayed image
FIG. 4: display picture distortion caused by waveguide display module
a: inputting a picture; b: display screen
FIG. 5: display distortion is removed after adding display distortion correction
Detailed Description
The invention will now be further described with reference to the following examples and drawings:
the embodiment of the invention is shown in attached figures 1-5; FIG. 1 shows a detection process.
Step 1: the method comprises the following steps that a waveguide display module distortion test system is adopted, a bracket is adjusted to adjust the collimator tube, a waveguide display module and a camera to be coaxial, the camera shoots a reference image with a scale grid in the collimator tube through the waveguide display module, then the waveguide display module is electrified and a test picture is input, and the camera shoots a display image with distortion on the waveguide display module; the schematic diagram of the waveguide display module distortion testing system is shown in figure 2.
Step 2: respectively performing digital enhancement processing on the reference image with the scale grids and the display image with distortion acquired in the step 1 by adopting a maximum between-class variance algorithm and a morphological processing algorithm; the reference image and the display image after the digital enhancement processing are shown in fig. 3.
And step 3: establishing a mapping relation between angle coordinates and image coordinates, wherein the angle coordinates of intersections of longitudinal lines and transverse lines of a scale grid are known on a reference image, the sub-pixel level image coordinates of the intersections are obtained by calculation through a feature detection algorithm, and the angle coordinates and the image coordinates of each intersection are in one-to-one correspondence by adopting a two-dimensional sorting algorithm from top to bottom and from left to right;
and 4, step 4: calculating the actual angle coordinates of light spots on a display image, calculating the sub-pixel level image coordinates of the center of each light spot on the display image by adopting a light spot detection algorithm, finding 4 nearest cross points on a reference image for each light spot, and converting the image coordinates of the light spots into angle coordinates by adopting a bilinear interpolation algorithm;
and 5: the actual angle coordinate of the light spot on the display image calculated by the step 4 is a distortion point coordinate, the angle coordinate of the light spot on the test picture in the step 1 is an ideal point coordinate, a two-dimensional sequencing algorithm from top to bottom and from left to right is adopted to establish the corresponding relation between the distortion point and the ideal point, and waveguide display distortion correction parameter calculation is carried out according to the distribution conditions of the ideal point and the distortion point; the waveguide display module causes distortion of the display screen as shown in fig. 4.
Step 6: and 5, performing display distortion correction on the input picture of the waveguide display module by adopting the distortion correction parameters obtained in the step 5, and comparing and verifying the display image through a collimator. The display distortion is removed after the display distortion correction is added, see fig. 5.
The specific process is as follows:
1) capturing source image and distorted display image
A) Placing the flat display optical system on a rotary table, adjusting the rotary table to align the origin, the transverse axis and the longitudinal axis of the optical system with the collimator, and locking the rotary table;
B) adjusting exposure parameters of a camera to enable grid scale lines of 1 degree multiplied by 1 degree on the collimator to be clearly visible, and shooting a picture of the collimator to obtain a source image;
C) displaying a 1 ° × 1 ° grid picture on the head-up optical system, and capturing a distorted display image by a camera;
2) preprocessing a source image and a distorted display image
A) Respectively converting the source image and the distorted display image into gray level images;
B) adopting a digital enhancement algorithm to perform detail enhancement on the gray level image, performing line sharpening enhancement on a source image, and performing spot enhancement on a distorted image;
3) reference point recognition and marking of source images
A) Carrying out image segmentation on a source image to ensure that each sub-image only contains an intersection point of a longitudinal scale mark and a transverse scale mark, wherein the intersection points are reference points;
B) detecting and identifying a longitudinal line segment and a transverse line segment in the subimage;
C) and (3) establishing a linear equation of the longitudinal scale lines and the transverse scale lines, and solving reference point coordinates of the sub-pixel level.
4) Distortion point identification and marking of distorted display images
A) Carrying out image segmentation on the distorted display image to ensure that each sub-image only contains one light spot, wherein the center of the light spot is the position of a distortion point;
B) and (5) carrying out light spot detection on the sub-images, and solving the distortion point coordinates of the sub-pixel level.
5) Resolving distortion correction parameters
Selecting a pincushion type distortion model according to the distribution conditions of the reference points and the distortion points, and resolving display distortion correction parameters;
6) analyzing and verifying effectiveness of distortion correction parameters
And (5) pre-correcting the display picture by using the distortion correction parameters calculated in the step 5), and comparing and verifying the effectiveness of distortion correction through a collimator.
Claims (3)
1. A method for detecting display distortion of a high-efficiency large-view-field flat display system is characterized by comprising the following steps:
step 1: the method comprises the following steps that a waveguide display module distortion test system is adopted, a bracket is adjusted to adjust the collimator tube, a waveguide display module and a camera to be coaxial, the camera shoots a reference image with a scale grid in the collimator tube through the waveguide display module, then the waveguide display module is electrified and a test picture is input, and the camera shoots a display image with distortion on the waveguide display module;
step 2: respectively carrying out digital enhancement processing on the reference image with the scale grids and the display image with distortion acquired in the step 1 by adopting an image digital enhancement method;
step 3, establishing a mapping relation between the angle coordinate and the image coordinate: on a reference image, the angle coordinates of the intersections of the longitudinal lines and the transverse lines of the scale grids are known, and the angle coordinates of each intersection and the image coordinates are in one-to-one correspondence by adopting a two-dimensional sorting algorithm from top to bottom and from left to right; calculating the sub-pixel level image coordinates of the cross points by adopting a feature detection algorithm;
step 4, resolving the actual angle coordinate of the light spot on the display image: on the displayed image, resolving the sub-pixel level image coordinates of the center of each light spot by adopting a light spot detection algorithm, and converting the image coordinates of the light spots into angle coordinates by adopting a bilinear interpolation algorithm according to the mapping relation between the angle coordinates and the image coordinates in the step 3;
and 5: the actual angle coordinate of the light spot on the display image calculated by the step 4 is a distortion point coordinate, the angle coordinate of the light spot on the test picture in the step 1 is an ideal point coordinate, a two-dimensional sequencing algorithm from top to bottom and from left to right is adopted to establish the corresponding relation between the distortion point and the ideal point, and waveguide display distortion correction parameter calculation is carried out according to the distribution conditions of the ideal point and the distortion point;
step 6: and 5, performing display distortion correction on the input picture of the waveguide display module by adopting the distortion correction parameters obtained in the step 5, and comparing and verifying the display image through a collimator.
2. The method for detecting display distortion of a high-efficiency large-field-of-view flat display system according to claim 1, wherein: the image digital enhancement is a maximum between-class variance method and a morphology processing method.
3. The method for detecting display distortion of a high-efficiency large-field-of-view flat display system according to claim 1, wherein: the feature detection algorithm is cross point edge detection or light spot detection.
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| CN113920145A (en) * | 2021-12-08 | 2022-01-11 | 天津大学 | Projection image quality evaluation and calculation method for projection system |
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