A method for detecting optical engine distortion of a projector

Abstract

The present application relates to the field of projectors, in particular to a kind of projector optical machine distortion detection method. By projecting specific binary square mark image, the optical machine projection image obtained by camera is converted from camera coordinate system to optical machine coordinate system, after this conversion, the edge detected in image, in combination with the scale of image pixel and actual distance, the actual optical machine edge length and width can be calculated. It makes up for the shortcomings that the existing method can only test the performance of optical machine, and cannot detect the distortion degree of optical machine picture. At the same time, it is not necessary to measure the edge size of optical machine projection picture manually, which simplifies the operation process of optical machine distortion detection, and can realize automatic detection.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of projectors, in particular to a projector light engine distortion detection method. BACKGROUND

[0002] With the increasing of the shipment of intelligent projectors, the demand for light engines, one of the core components of projectors, also increases. Before leaving the factory, the light engine needs to be tested for multiple technical parameters, including light engine brightness, working condition, light engine projection picture distortion, etc. Efficient and accurate light engine testing process and tools can help improve the production yield of projectors and improve the user experience. The testing standards for light engine distortion often differ between light engine manufacturers and projector manufacturers. Light engines that meet the factory standards of light engine manufacturers may not meet the requirements of projector manufacturers. In particular, it is more difficult for projector manufacturers to control the projection distortion of light engines, which affects the production of projectors. Under this background, it is imperative to design a light engine distortion detection device to help projector manufacturers screen light engines that do not meet the requirements before installing the light engine.

[0003] There are many related methods for detecting projector light engines. Patent CN10095256A provides a projector light engine testing system and method. This method mainly obtains the current brightness, chrominance of the light engine projection picture and the duty cycle of red, green and blue LEDs under the current brightness through a burning board to determine whether the light engine is working properly. Patent CN208653759U provides a detection device for a projector. The light engine is fixed on a workbench, and heat dissipation fans are added around the light engine. The heat dissipation fans work simultaneously when the light engine is working to ensure stable operation of the light engine and improve the detection accuracy of the light engine performance detection. Patent CN208968783U also provides a light engine detection jig and device. The device adds a jig to fix the light engine, which adjusts the position of the light engine through the jig to improve the convenience of detecting the light engine. The devices or methods provided in the above patents focus on the performance detection and heat dissipation of the light engine, and do not involve the distortion detection of the light engine.

[0004] Defects: With the rapid development of intelligent hardware, household intelligent projectors are also favored by more and more users, and the sales of intelligent projectors are also increasing. Therefore, improving the production efficiency of projectors is a problem to be solved. As one of the core components of projectors, the light engine will be subjected to distortion detection of the original projection picture before leaving the factory. However, when developing the automatic trapezoidal correction function of the projector, the projector manufacturer also has requirements for the distortion of the original projection picture of the light engine. The standards of the two often differ, and this difference poses a risk to the trapezoidal correction function, which affects the production yield and production efficiency of the projector. In addition, repeated disassembly and assembly of the defective machine is also a time-consuming and laborious process. SUMMARY

[0005] The purpose of the application is to provide a better effect of a projector light machine distortion detection method, the specific purpose see the multiple substantial technical effects of the specific implementation part.

[0006] In order to achieve the above purpose, the application adopts the following technical scheme:

[0007] A kind of projector light machine distortion detection method, it is characterized in that, by projecting specific binary square mark image, the light machine projection image obtained by camera is converted from camera coordinate system to light machine coordinate system, after this transformation, the edge detected in image, in combination with the scale of image pixel and actual distance, the actual light machine edge length and width can be calculated.

[0008] The further technical scheme of the application is to convert the projection image from the camera coordinate system to the projector coordinate system using the binary square mark, and the edge in the converted image is the light machine projection edge, so that the edge in the image is used to replace manual measurement of the edge.

[0009] The further technical scheme of the application is that the method uses the following device, which includes a base 1, a fan 2 arranged on the base 1, and a light machine 3 arranged on the fan; it also includes a camera 4 arranged on the side of the device; and a control circuit 5 arranged above the light machine.

[0010] The further technical scheme of the application is to realize light machine detection, including the following steps:

[0011] Step 101, install the light machine to the specified position and fix it, and use the control circuit to drive the light machine to start working;

[0012] Step 102, adjust the camera to be at the same height as the light machine, and the camera plane is parallel to the picture projected by the light machine;

[0013] Step 103, control the projector to project four binary square mark images based on ArUco library and a pure white picture with the same resolution as the projector in turn, for each binary square mark, starting from the upper left corner, record the position coordinates of the upper left corner, the upper right corner, the lower right corner and the lower left corner of the mark in the clockwise direction, a total of 16 vertex coordinates;

[0014] The further technical scheme of the application is that in step 104, the camera is controlled to collect the binary square mark images and the pure white images projected by the projection device, a binary square mark detection operator is created according to the method of creating binary square mark by ArUco, and the four vertices of each binary square mark in the collected images are detected, and the 16 vertex coordinates are recorded in the order of recording the vertex coordinates in step 103.

[0015] The further technical solution of the present application is that, in step 105, the perspective transformation relationship from the projection image acquired by the camera to the image projected by the projector is calculated according to the 16 vertex coordinates of the four binary square marks recorded in step 103 and the 16 vertex coordinates of the four binary square marks detected in step 104, and the projection image in the camera coordinate system acquired by the camera is converted into a projection image in the projection device coordinate system through the perspective transformation relationship.

[0016] The further technical solution of the present application is that, in step 106, the perspective transformation matrix acquired in step 105 is applied to the pure white image acquired in step 104 to acquire a projection image in the projector coordinate system, and the image edge in the projection image is the edge formed by the bright field of the projected picture and the dark field of the environment. The distortion information of the light machine can be acquired by extracting the image edge.

[0017] The further technical solution of the present application is that, in step 107, a two-dimensional Gaussian template with a size of 7*7 is created, the center of the Gaussian template is aligned with the pixel of the projection image from the top left corner of the projection image, the sum of the products of all template values and the pixel values covered by the template is calculated, and the average value is taken to set the value of the pixel corresponding to the center of the template in the projection image. The template is controlled to traverse each pixel of the projection image, so that the image is smoothed and the image noise is reduced. After the image noise reduction is completed, the image edge in the projection image is searched in a scanning manner to extract the distortion degree of the projection of the light machine. The specific scanning manner is as follows: taking the center point coordinate of the image as the starting point and the horizontal right as the starting search direction, the difference between the pixel values of the previous pixel and the next pixel in the image is calculated, and the pixel values whose difference exceeds the set threshold value are recorded. When the edge of the image is searched, the search in this direction is terminated, the search starting point is set as the image center, the search direction is counterclockwise rotated by 1 degree, the above search process is repeated, and the search is terminated after the search direction is rotated by 360 degrees.

[0018] The further technical solution of the present application is that, in step 108, the edge points acquired in step 107 are classified into points on the upper, lower, left and right edges according to the horizontal and vertical middle lines of the image, and four straight lines are fitted by the least square method, the straight line equations of the four straight lines are acquired, and the intersection points of the four straight lines are calculated according to the straight line equations.

[0019] The further technical scheme of the present application is that, in step 109, the pixel distances of four edge line segments connected by four points are calculated, and according to the ratio of the image distance to the actual picture distance, the four-point pixel distance is converted into the length of the upper and lower edges of the projection picture in the horizontal direction, the height of the left and right edges of the projection picture in the vertical direction, and the angles of the upper and lower straight lines and the left and right straight lines, and the set height difference threshold and angle difference threshold are combined to determine whether the optical engine distortion meets the standard; thus, the detection of the optical engine distortion is completed

[0020] The present application has the following beneficial effects compared with the prior art: the present application remedies the defect of the prior art that only the performance of the optical engine can be tested and the distortion degree of the optical engine picture cannot be detected; at the same time, manual measurement of the edge size of the projection picture of the optical engine is not required, the operation process of the optical engine distortion detection is simplified, and automatic detection can be realized. Through the present application, the optical engine can be screened before the projector is assembled, so that the optical engine that meets the factory standard but does not meet the standard for the automatic keystone correction function of the projector can be excluded. The repeated disassembly of the projector after the projector is assembled is avoided, and the production efficiency and yield of the projector are improved. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to further illustrate the present application, the following further illustrates the present application with reference to the accompanying drawings:

[0022] Figure 1 is a schematic view of the device of the present application;

[0023] Wherein: 1, base; 2, fan; 3, optical engine; 4, camera; 5, control circuit.

[0024] Figure 2 is a step implementation diagram of the present application. DETAILED DESCRIPTION

[0025] The present application is further illustrated with reference to the accompanying drawings and specific embodiments. It should be understood that the following embodiments are only used to explain the present application and not intended to limit the scope of the present application. In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", "top", "bottom" and the like indicate the orientation or positional relationship shown in the drawings, and are only used to facilitate the description of the present application and simplify the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. In addition, unless otherwise specified and limited, the terms "mounting", "connecting", "connecting" should be broadly understood, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be connected inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0026] It should be noted that in this paper, such as the first and second relationship terms are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between the entities or operations. Moreover, the terms "include", "contain" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or includes elements inherent to such process, method, article or device.

[0027] The present application provides a variety of parallel schemes, and different expressions belong to improved schemes or parallel schemes based on the basic scheme. Each scheme has its own unique features. In addition, the technical features involved in the different embodiments of the present application described below can be combined with each other as long as there is no conflict between them. The fixing mode not described in the text can be any one of the fixing modes such as screw fixing, bolt fixing or glue bonding.

[0028] Embodiment one: combined Figure 1The application discloses a projector light machine distortion detection method, characterized in that a specific binary square mark image is projected, and a light machine projection image acquired by a camera is converted from a camera coordinate system to a light machine coordinate system; after the conversion, an edge detected in the image can calculate actual light machine edge length and width in combination with a scale of image pixels and actual distances.

[0029] The application can screen the light machine before the projector is assembled, so as to exclude the light machine that meets the factory standard but does not meet the standard for the automatic trapezoidal correction function of the projector, avoid repeated disassembly of the projector after the projector is assembled, and improve the production efficiency and yield of the projector.

[0030] Embodiment two: as a further improvable scheme or parallel scheme or alternative independent scheme, the method uses a device including a base 1, a fan 2 arranged on the base 1, a light machine 3 arranged on the fan, a camera 4 arranged on the side of the device, and a control circuit 5 arranged above the light machine.

[0031] Embodiment three: as a further improvable scheme or parallel scheme or alternative independent scheme, the light machine detection includes the following steps.

[0032] Step 101, install the light machine to a specified position and fix the light machine, and drive the light machine to start working by using the control circuit;

[0033] Step 102, adjust the camera to be substantially at the same height as the light machine, and adjust the camera plane to be parallel to the projection plane of the light machine;

[0034] Step 103, control the projector to project four binary square mark images based on the ArUco library and a pure white picture with the same resolution as the projector in sequence, record the position coordinates of the top left corner, the top right corner, the bottom right corner and the bottom left corner of each binary square mark from the top left corner in the clockwise direction, and record a total of 16 vertex coordinates;

[0035] Step 104, control the camera to collect the binary square mark image and the pure white image projected by the projection device, create a binary square mark detection operator according to the method of creating a binary square mark by ArUco, detect the four vertices of each binary square mark in the collected image, and record the 16 vertex coordinates in the order of the vertex coordinates recorded in step 103;

[0036] Step 105, according to the 16 vertex coordinates of the four binary square marks recorded in step 103 and the 16 vertex coordinates of the four binary square marks detected in step 104, calculate the perspective transformation relationship from the projection image obtained by the camera to the image projected by the projector, and convert the projection image in the camera coordinate system obtained by the camera to the projection image in the projection device coordinate system through the perspective transformation relationship;

[0037] Step 106, apply the perspective transformation matrix obtained in step 105 to the pure white image obtained in step 104 to obtain the projection image in the projector coordinate system, the image edge in the image is the edge formed by the bright field of the projection picture and the dark field of the environment, and the distortion information of the light machine can be obtained by extracting the image edge;

[0038] Step 107, create a 7x7 two-dimensional Gaussian template, align the center of the Gaussian template with the projection image pixel from the top left corner of the projection image, calculate the sum of the products of all template values and pixel values covered by the template, and then take the average value, set the average value as the value of the projection image pixel point corresponding to the template center, control the template to traverse each pixel of the projection image, which can realize image smoothing and reduce image noise; after completing image noise reduction, search for the image edge in the projection image in a scanning manner, extract the distortion degree of the light machine projection, and the specific scanning manner is as follows: taking the center point coordinate of the image as the starting point, the search direction is initially horizontal to the right, calculating the difference between the pixel values of the previous and next pixels in the image, and recording the pixel values whose difference exceeds the set threshold; when the edge of the image is searched, terminate the search in this direction, set the search starting point as the image center, and at the same time, rotate the search direction counterclockwise by 1 degree, repeat the above search process until the search direction is rotated by 360 degrees and the search is terminated;

[0039] Step 108, taking the horizontal and vertical midlines of the image as the reference, classify the edge points obtained in step 107 into points on the upper, lower, left and right edges, and fit four straight lines respectively by means of the least square method, obtain the straight line equations of the four straight lines, and calculate the intersection points of the four straight lines according to the straight line equations;

[0040] Step 109, the pixel distance of four connected edge lines is calculated, and according to the ratio of the image and the actual picture distance, the four-point pixel distance is converted into the length of the upper and lower edges of the projection picture in the horizontal direction, the height of the left and right edges in the vertical direction, and the angle of the upper and lower straight lines and the left and right straight lines, combined with the set height difference threshold and angle difference threshold, to judge whether the optical machine distortion is qualified; thus, the detection of optical machine distortion is completed.

[0041] The patent has the characteristics of realizing detection before assembly, avoiding detection failure after assembly, wasting manpower, and reducing hidden costs.

[0042] The basic principle, main features and advantages of the present application are shown and described above. Those skilled in the art should understand that the present application is not limited by the above examples, and the above examples and descriptions in the specification are only to illustrate the principles of the present application, and various changes and improvements can be made without departing from the spirit and scope of the present application, and these changes and improvements all fall within the scope of protection.

Claims

1. A method for detecting optical engine distortion of a projector, characterized in that, The method comprises: By projecting a specific binary square marker image, the camera-acquired optical machine projection image is converted from the camera coordinate system to the optical machine coordinate system. After this conversion, the edges detected in the image can calculate the actual optical machine edge length and width in combination with the scale of the image pixels and the actual distance. Wherein, the optical machine detection comprises the following steps: Step 103, control the projector to project four binary square marker images based on ArUco library and a pure white picture with the same resolution as the projector. Each binary square marker records the position coordinates of the top left corner, top right corner, bottom right corner and bottom left corner in a clockwise direction, a total of 16 vertex coordinates. Step 104, control the camera to capture the binary square marker images and the pure white image projected by the projector. According to the method of creating binary square markers by ArUco, create a binary square marker detection operator to detect the four vertices of each binary square marker in the captured image, and record the 16 vertex coordinates in the order of recording vertex coordinates in step 103. Step 105, according to the 16 vertex coordinates of the four binary square markers recorded in step 103 and the 16 vertex coordinates of the four binary square markers detected in step 104, calculate the perspective transformation relationship of the projection image acquired by the camera to the image projected by the projector, and convert the projection image in the camera coordinate system acquired by the camera to the projection image in the projector coordinate system through the perspective transformation relationship. Step 106, apply the perspective transformation matrix obtained in step 105 to the pure white image obtained in step 104 to obtain the projection image in the projector coordinate system. The image edges in the projection image are the edges formed by the bright field of the projected picture and the dark field of the environment. Extract the image edges to obtain the distortion information of the optical machine. Step 107, a two-dimensional Gaussian template with a size of is created, the center of the Gaussian template is aligned with the pixel of the projection image from the upper left corner of the projection image, the sum of the product of all template values and the pixel values covered by the template is calculated, the average value is taken, the average value is set as the value of the pixel point of the projection image corresponding to the template center, the template is controlled to traverse each pixel of the projection image, the image smoothing is realized, after the image denoising is completed, the image edge in the projection image is searched in a scanning manner, and the distortion degree of the optical-mechanical projection is extracted. Step 108, classify the edge points obtained in step 107 based on the horizontal and vertical center lines of the image, and divide them into points on the upper, lower, left and right edges. Four straight lines are fitted by least squares method respectively, the straight line equations of the four straight lines are obtained, and the intersection points of the four straight lines are calculated according to the straight line equations. Step 109, calculate the pixel distance of the four edge line segments connected by the four points, and convert the pixel distance to the length of the upper and lower edges of the projection picture in the horizontal direction, the height of the left and right edges of the projection picture in the vertical direction, and the angles of the upper and lower straight lines and the left and right straight lines according to the ratio of the image distance to the actual picture distance. Combine the set height difference threshold and angle difference threshold to determine whether the optical machine distortion meets the standard. Thus, the optical machine distortion detection is completed.

2. The method for detecting optical engine distortion in a projector as described in claim 1, characterized in that, The binary square marker is used to convert the projection image from the camera coordinate system to the projector coordinate system. The edges in the converted image are the optical machine projection edges, so the edges in the image are used to replace manual measurement of the edges.

3. The method for detecting optical engine distortion in a projector as described in claim 1, characterized in that, The method uses the following device, the device contains the base (1), the base (1) is arranged with fan (2), fan is arranged with light machine (3);Also contains the camera (4) arranged in the device side;Above the light machine contains control circuit (5).

4. The method of claim 1, wherein the method further comprises the steps of: before the step 103, the method further comprises the following steps: Before the step 103, the method further comprises the following steps: Step 101, install the light machine to the designated position and fixed, using control circuit drive the test light machine start working; Step 102, adjust the camera and light machine is basically at the same height, and the camera plane and light machine projection picture parallel.

5. The method of claim 1, wherein the method further comprises the steps of: The specific scanning mode in the step 107 is as follows: take the center point coordinate of the image as the starting point, the search direction is horizontal right, calculate the difference between the pixel value of the previous pixel and the next pixel in the image, record the pixel value whose difference exceeds the set threshold value; When the edge of the image is searched, the search in this direction is terminated, the search starting point is set to the image center, at the same time, the search direction is rotated counterclockwise by 1 degree, the above search process is repeated until the search direction is rotated 360 degrees, and the search is terminated.

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