Projector correction method and system

Abstract

This invention provides a projector calibration method and system. The projector includes a collimating element and a diffractive optical element. The calibration method includes the following steps: aligning the central axis of the camera with the central axis of the collimating element placed on a fixture; identifying the pose difference between the collimating element and the diffractive optical element, and performing rotational correction based on the pose difference; selecting a pattern in a first region for defocus testing to obtain the optimal position of the vertical distance between the collimating element and the diffractive optical element, and making corresponding position adjustments; comparing the sharpness of the four corners of the obtained pattern in the first region, and performing tilt correction based on the comparison results; obtaining the position coordinates of the optical center point based on the center point coordinates of the feature points of the region pattern; and performing translational correction on the collimating element and the diffractive optical element based on the obtained center point position coordinates, so that the center point coordinates coincide with the camera center point. This invention achieves automatic calibration, which can improve the calibration accuracy and quality of the projector.

Description

Technical Field

[0001] This invention relates to the field of projector technology, and more specifically to a projector correction method and system. Background Technology

[0002] With the rise of structured light technology, the use of projectors has increased rapidly. Meanwhile, backend algorithms have stringent requirements for projector quality; therefore, high-quality projectors have a positive impact on business share. Current technologies mainly use transmissive methods to correct projectors, but this typically involves correcting only a portion of the image, resulting in significant flatness shifts. These large flatness shifts can lead to gaps in the image pattern. Summary of the Invention

[0003] To address the problems in the prior art, the present invention aims to provide a projector correction method and system. The projector correction method employs automated calibration, resulting in high calibration accuracy and good product quality.

[0004] This invention provides a projector correction method, wherein the projector includes a collimating element and a diffractive optical element, and the method includes the following steps:

[0005] Make the central axis of the camera coincide with the central axis of the collimating element placed on the fixture;

[0006] The camera identifies the pose difference between the collimating element and the diffractive optical element, and performs rotational correction based on the pose difference;

[0007] A defocus test is performed on the pattern in the first region to obtain the optimal position of the vertical distance between the collimating element and the diffractive optical element, and the position is adjusted accordingly.

[0008] The sharpness of the four corners of the obtained regional pattern of the first region is compared, and tilt correction is performed based on the comparison results;

[0009] The position coordinates of the optical center point are obtained based on the center point coordinates of the feature points of the area pattern.

[0010] Based on the obtained center point coordinates, the collimating element and the diffractive optical element are translated and corrected so that the center point coordinates coincide with the camera center point.

[0011] In some embodiments, the camera is a full-frame camera.

[0012] In some embodiments, before performing the defocus test on the pattern in the selected first region, the following steps are included:

[0013] The camera identifies the outline points of the overall pattern projected by the diffractive optical element;

[0014] The position coordinates of the pre-optical center are obtained based on the contour points;

[0015] Using the pre-optical center as the central coordinate, select the region pattern of the first region.

[0016] In some embodiments, before the camera identifies the contour points of the overall pattern projected by the diffractive optical element, the following steps are further included:

[0017] Select the area pattern of the first region centered on the camera;

[0018] Grayscale arrangement of all pixels of the selected pattern;

[0019] Select pixels with brightness below n% (High_n) and pixels with brightness above n% (Low_n), and calculate the ratio between them, where 10 ≤ n ≤ 30.

[0020] When the ratio is greater than or equal to the preset contrast threshold, the entire outline of the projected pattern is fully rendered.

[0021] In some embodiments, the camera's identification of the contour points of the overall pattern projected by the diffractive optical element further includes the following steps:

[0022] Calculate the standard deviation values ​​of the horizontal and vertical brightness in the overall pattern;

[0023] When the standard deviation value exceeds the preset standard deviation threshold, it is identified as a point in the profile, and the points of all profiles are calculated in this way.

[0024] In some embodiments, obtaining the position coordinates of the pre-optical center based on the contour points of the projection pattern includes the following steps:

[0025] Calculate the weights of the contour points to obtain the weight centers OC_weight_x and OC_weight_y;

[0026] Based on the obtained weight center, calculate the position coordinates (OC) of the pre-optical center. x OC y ).

[0027] In some embodiments, the calculation of the position coordinates (OC) of the pre-optical center x OC y ), satisfying the formula:

[0028] OC X =OC_weight_x+(OC_weight_x-Sensor_x)*factor_x;

[0029] OC Y =OC_weight_y+(OC_weight_y-Sensor_y)*factor_y;

[0030] Where sensor_x is the X coordinate of the camera center, factor_x is the distortion factor in the X direction of the camera, sensor_y is the Y coordinate of the camera center, and factor_Y is the distortion factor in the Y direction of the camera.

[0031] In some embodiments, the defocus test of the pattern in the first region further includes the following steps:

[0032] The defocus test is performed using a contrast method, and the point where the contrast is highest is the optimal position of the projector.

[0033] In some embodiments, the method of obtaining the position coordinates of the optical center point based on the center point coordinates of the feature points of the region pattern further includes the following steps:

[0034] Multiple feature points are identified by comparing with a standard template;

[0035] The position coordinates of the center point are calculated based on the feature points.

[0036] In some embodiments, obtaining the position coordinates of the optical center point based on the center point coordinates of the feature points of the region pattern further includes the following steps:

[0037] Multiple feature points are obtained through algorithm calculation;

[0038] Based on the positional relationship between the feature points and the center point, the coordinates of the zero and pole positions are determined.

[0039] In some embodiments, after performing translational correction to make the center point coordinates coincide with the camera center point, the method further includes:

[0040] The collimating element and the diffractive optical element are cured by dispensing and UV exposure.

[0041] The present invention provides a projector correction system, wherein the projector includes a collimating element and a diffractive optical element, the system includes a camera, a clamp and a controller, the clamp is used to fix the collimating element of the projector, and the system is used to implement the projector correction method as described above.

[0042] The projector correction method and system provided by this invention have the following advantages:

[0043] This invention provides a projector calibration method that enables automatic calibration and improves the calibration accuracy and quality of the product. Attached Figure Description

[0044] Other features, objects, and advantages of the invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings.

[0045] Figure 1 This is a schematic diagram of a projector correction method according to an embodiment of the present invention;

[0046] Figure 2 This is a schematic diagram of the method steps prior to the preferred step S300 provided by the present invention;

[0047] Figure 3 This is a contour view of the projected pattern acquired by a camera according to an embodiment of the present invention;

[0048] Figure 4 This is a schematic diagram of the method steps prior to step S210 in an embodiment of the present invention;

[0049] Figure 5 This is a schematic diagram of the method steps that further include step S210 in an embodiment of the present invention;

[0050] Figure 6 This is a schematic diagram of a defocus test according to an embodiment of the present invention;

[0051] Figure 7a and Figure 7b This is a schematic diagram of the projector before and after tilt correction according to an embodiment of the present invention;

[0052] Figure 8 This is a schematic diagram of finding the center point of light according to an embodiment of the present invention;

[0053] Figure 9 This is a schematic flowchart of a projector correction method provided in an embodiment of the present invention. Detailed Implementation

[0054] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, they are provided so that the invention will be thorough and complete, and will fully convey the concept of the exemplary embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar structures, and therefore repeated descriptions of them will be omitted. The words “or” and “or” in the specification may mean “and” or “or”.

[0055] like Figure 1 As shown, the present invention provides a projector correction method, wherein the projector includes a collimating element and a diffractive optical element, and the method includes the following steps:

[0056] S100: Align the central axis of the camera with the central axis of the collimating element placed on the clamp;

[0057] Specifically, the camera is a full-frame camera, capable of capturing the entire pattern projected onto the screen via the diffractive optical element. When the collimating element coincides with the center of the diffractive optical element, the axis of the center point of the entire pattern, the axis of the projector's center point, and the axis of the camera's center point coincide. The camera's center point position remains unchanged, while the pattern's center point position depends on the alignment of the collimating element and the diffractive optical element's center points. Therefore, the positions of the collimating element and the diffractive optical element can be calibrated based on the relative positional difference between the camera's center point and the center point of the projected entire pattern, resulting in a high-quality projector. Aligning the camera's central axis with the collimating element placed on the fixture ensures that the center position of the pattern formed by the diffractive optical element is as close as possible to the camera's center point, facilitating adjustments to the positional differences between the diffractive optical element and the collimating element and improving adjustment efficiency.

[0058] S200: The camera identifies the pose difference between the collimating element and the diffractive optical element, and performs rotational correction based on the pose difference;

[0059] Specifically, the camera finds the contours of the collimating element and the diffractive optical element, which are processed to present speckles. Based on the obtained contour differences, the camera obtains the pose differences of the collimating element and the diffractive optical element, and performs rotational correction on both, that is, correction around the OZ axis.

[0060] S300: Select the pattern in the first region for defocus testing to obtain the optimal position of the vertical distance between the collimating element and the diffractive optical element, and make corresponding position adjustments;

[0061] The optimal position of the vertical distance between the collimating element and the diffractive optical element is the position of the clearest point of the two elements in the Z-axis direction. When the two elements are adjusted to the optimal position in the Z-axis direction, the pattern will be the clearest pattern in the Z-axis direction.

[0062] S400: Compare the sharpness of the four corners of the obtained area pattern of the first area, and perform tilt correction based on the comparison results;

[0063] Specifically, when the collimating element and the diffractive optical element are tilted at an angle, the resulting regional pattern in the first region will show a clear central area and a blurred edge area. Therefore, by adjusting the tilt angle of the diffractive optical element relative to the collimating element, i.e., rotating it along the OX and OY directions, the entire region of the pattern can be made clear.

[0064] S500: Obtain the position coordinates of the optical center point based on the center point coordinates of the feature points of the area pattern;

[0065] S600: Based on the obtained center point position coordinates, the collimating element and the diffractive optical element are translated and corrected so that the center point coordinates coincide with the camera center point.

[0066] Specifically, when the coordinates of the center point of the area pattern are obtained, the planar position coordinates of the optical center point of the projector are the same as those of the center point of the area pattern. Therefore, the positional differences between the diffractive optical element and the collimating element and the camera's center point in the X and Y directions can be obtained from the center point coordinates of the pattern. Adjusting these positional differences allows the centers of the collimating element and the diffractive optical element to be aligned, completing the projector calibration. This projector calibration method ensures that the rotation angle of the finished projector is controlled below 0.5°; the positional offset of the collimating element and the diffractive optical element on the plane is less than 2 pixels; the splicing gap between the unit patterns formed by the projector is less than 2 pixels; and the calibration capacity is 100-120 units per hour. This projector calibration method improves product accuracy and quality, and increases production efficiency.

[0067] like Figure 2 As shown, before selecting the pattern in the first region for defocus testing in step S300, the following steps are also included:

[0068] S210: The camera identifies the outline points of the overall pattern projected by the diffractive optical element;

[0069] S220: Obtain the position coordinates of the pre-optical center based on the contour points;

[0070] S230: Using the pre-optical center as the central coordinate, select the region pattern of the first region.

[0071] like Figure 3 As shown, the overall pattern outline points identified by the camera are the shape enclosed by the area indicated by the arrow, that is, the brighter area shown in the figure, which can be distinguished as multiple squares. The remaining areas outside the outline points, such as the area indicated by the circle, cannot be found due to their low brightness, but this does not affect the subsequent calculations.

[0072] like Figure 4 As shown, before the camera identifies the contour points of the overall pattern projected by the diffractive optical element in step S210, the method further includes the following step:

[0073] S201: The area pattern of the first region centered on the machine;

[0074] S202: Grayscale arrangement of all pixels of the selected pattern;

[0075] S203: Take the pixels with brightness before n% High_n and the pixels with brightness after n% Low_n, and calculate the ratio between the two, where 10≤n≤30;

[0076] S204: When the ratio is greater than or equal to the preset contrast threshold, the outline of the entire projected pattern is fully rendered.

[0077] The six-axis and gripper used for position adjustment are highly precise; therefore, the pattern projected by the diffraction optics should appear near the center of the camera. In this embodiment, a 300-pixel * 300-pixel area is selected with the camera center as the center point. All pixels within the selected area are arranged in grayscale from 0 to 255. In this embodiment, pixels with brightness values ​​in the top 20% (High_20) and pixels with brightness values ​​below 20% (Low_20) are selected, and the ratio of High_20 to Low_20 is calculated, i.e., ratio = High_20 / Low_20. Pre-clarification is performed based on the contrast value. When the contrast value is greater than or equal to the contrast threshold set for pre-clarification, it indicates that pre-clarification is complete, and the overall projected outline is presented. The contrast threshold is an empirical value obtained through a large number of images.

[0078] After the overall outline of the projected pattern has been pre-defined, the outline of the pre-defined pattern needs to be determined, such as... Figure 5 As shown, step S210, where the camera identifies the contour points of the overall pattern projected by the diffractive optical element, further includes the following steps:

[0079] S211: Calculate the standard deviation of the brightness of the horizontal and vertical unit patterns in the overall pattern;

[0080] S212: When the standard deviation value exceeds the preset standard deviation threshold, the unit pattern is confirmed as a point in the contour, and the points of all contours are calculated in this way.

[0081] like Figure 3As shown, the projected overall pattern consists of multiple square patterns with varying brightness. The square patterns outside the contour points have the lowest brightness, while those inside the contour points have higher brightness. When calculating the standard deviation of the brightness of the first row of square patterns, if the standard deviation exceeds a preset standard deviation threshold, it is considered that the contour point of the pattern boundary has been reached, and the position of the contour point in that row can be confirmed. This process is repeated to obtain all contour points in the horizontal and vertical directions. The preset standard deviation threshold is an empirical value obtained from a large number of images.

[0082] Once the overall outline points of the projected pattern are determined, the position coordinates of the pre-optical center can be obtained based on the outline points of the projected pattern, including the following steps:

[0083] Calculate the weights of the contour points to obtain the weight centers OC_weight_x and OC_weight_y;

[0084] Based on the obtained weight center, calculate the position coordinates (OC) of the pre-optical center. x OC y ).

[0085] The calculation of the position coordinates (OC) of the pre-optical center x OC y ), satisfying the formula:

[0086] OC X =OC_weight_x+(OC_weight_x-Sensor_x)*factor_x;

[0087] OC Y =OC_weight_y+(OC_weight_y-Sensor_y)*factor_y;

[0088] Where sensor_x is the X coordinate of the camera center, factor_x is the distortion factor in the X direction of the camera, sensor_y is the Y coordinate of the camera center, and factor_Y is the distortion factor in the Y direction of the camera.

[0089] When there is a displacement deviation in the planar position of the collimating element and the diffractive optical element, the resulting projection pattern will be distorted. It is necessary to compensate for this distortion to obtain the position coordinates of the pre-optical center of the contour. The accuracy of the pre-optical center can be controlled within 15 pixels.

[0090] Once the coordinates of the pre-optical center are determined, select a 300-pixel * 300-pixel area centered on the pre-OC, such as... Figure 6As shown, using a contrast-based defocusing method, the optimal vertical distance between the collimating element and the diffractive optical element in the Z-axis direction is determined, i.e., the area within which the image is sharpest. Therefore, step S300, which involves selecting the pattern in the first region for defocusing testing, further includes the following steps:

[0091] The defocus test is performed using a contrast method, and the point where the contrast is highest is the optimal position of the projector.

[0092] Figure 6 This is a contrast-defocus curve graph for multiple projectors. The higher the contrast, the clearer the image. Figure 6 The horizontal axis represents the vertical distance between the collimating element and the diffractive optical element, and the vertical axis represents the projector's resolution value, i.e., the contrast value. When the contrast value reaches its peak, the horizontal axis corresponding to the peak point is the optimal vertical distance between the collimating element and the diffractive optical element. The vertical distance between the collimating element and the diffractive optical element can be adjusted according to the obtained optimal vertical position.

[0093] When the collimating element and the diffractive optical element are tilted at an angle, the sharpness (i.e., contrast) of the image in the central region will differ, such as... Figure 7a As shown in the circled area in the upper right corner, the image within the circled area is blurrier than the pattern in the center. Once the contrast at all four corners of the image is equal, meaning the four corners are clear, the tilt correction is complete. Figure 7b As shown.

[0094] Next, step S500 obtains the position coordinates of the optical center point based on the center point coordinates of the feature points of the region pattern, and also includes the following steps:

[0095] Multiple feature points are found by comparing with a standard template or by algorithmic calculation.

[0096] The position coordinates of the center point are calculated based on the feature points.

[0097] like Figure 8 As shown, the ellipse in the vertical direction of the middle area contains 12 feature points. The coordinates of the light center are obtained by the positional relationship between the feature points and the coordinates of the light center. Figure 8 The point indicated by the small circle in the central region is the coordinate of the obtained light center point. Based on the obtained position coordinates of the light center point, the collimating element and the diffractive optical element are translated and adjusted so that the center of the camera coincides with the light center point, thus completing the correction of the collimating element and the diffractive optical element.

[0098] After the translational correction is performed to make the center point coordinates coincide with the camera center point, the method further includes:

[0099] The collimating element and the diffractive optical element are cured by dispensing and UV exposure to form the corrected projector module.

[0100] Figure 9 The diagram shows the process flow of the projector calibration method, which is a simplified flowchart of the above steps. As can be seen from the diagram, the process includes loading, rotation calibration, pre-clarification, pre-optical centering, defocusing, tilt calibration, optical center calibration, UV (Ultraviolet) curing, and unloading. According to the above steps, the calibration of the alignment element and the diffractive optical element can be completed, resulting in a projector with high calibration accuracy and good quality.

[0101] This invention also provides a projector correction system. The projector includes a collimating element and a diffractive optical element. The system includes a camera, a clamp, and a controller. The clamp is used to fix the collimating element of the projector. The system is used to implement the projector correction method described above.

[0102] The projector correction method and system provided by this invention have the following advantages:

[0103] This invention provides a method for correcting a projector, which can achieve pattern synchronization between an industrial camera and a projector, resulting in high calibration accuracy, good product quality, and high production efficiency.

[0104] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A projector correction method, characterized in that, The projector includes a collimating element and a diffractive optical element, and the method includes the following steps: Make the central axis of the camera coincide with the central axis of the collimating element placed on the fixture; The camera identifies the pose difference between the collimating element and the diffractive optical element, and performs rotational correction based on the pose difference. The camera finds the contours of the collimating element and the diffractive optical element, which are processed to present speckle patterns. Based on the obtained contour difference, the camera obtains the pose difference between the collimating element and the diffractive optical element, and performs rotational correction on the collimating element and the diffractive optical element. A defocus test is performed on the pattern in the first region to obtain the optimal position of the vertical distance between the collimating element and the diffractive optical element, and the position is adjusted accordingly. The sharpness of the four corners of the obtained regional pattern of the first region is compared, and tilt correction is performed based on the comparison results; The position coordinates of the optical center point are obtained based on the center point coordinates of the feature points of the area pattern. Based on the obtained center point coordinates, the collimating element and the diffractive optical element are translated and corrected so that the center point coordinates coincide with the camera center point.

2. The projector correction method according to claim 1, characterized in that, The camera in question is a full-frame camera.

3. The projector correction method according to claim 1, characterized in that, Before performing the defocus test on the pattern selected in the first region, the following steps are included: The camera identifies the outline points of the overall pattern projected by the diffractive optical element; The position coordinates of the pre-optical center are obtained based on the contour points; Using the pre-optical center as the central coordinate, select the region pattern of the first region.

4. The projector correction method according to claim 3, characterized in that, Before the camera identifies the outline points of the overall pattern projected by the diffractive optical element, the following steps are also included: Select the area pattern of the first region centered on the camera; Grayscale arrangement of all pixels of the selected pattern; Select pixels with brightness below n% (High_n) and pixels with brightness above n% (Low_n), and calculate the ratio between them, where 10≤n≤30. When the ratio is greater than or equal to the preset contrast threshold, the entire outline of the projected pattern is fully rendered.

5. The projector correction method according to claim 3, characterized in that, The camera's identification of the contour points of the overall pattern projected by the diffractive optical element further includes the following steps: Calculate the standard deviation values ​​of the horizontal and vertical brightness in the overall pattern; When the standard deviation value exceeds the preset standard deviation threshold, it is identified as a point in the profile, and the points of all profiles are calculated in this way.

6. The projector correction method according to claim 3, characterized in that, Obtaining the position coordinates of the pre-optical center based on the contour points includes the following steps: Calculate the weights of the contour points to obtain the weight centers OC_weight_x and OC_weight_y; Based on the obtained weight center, calculate the position coordinates (OC) of the pre-optical center. x OC y ).

7. The projector correction method according to claim 6, characterized in that, The calculation of the position coordinates (OC) of the pre-optical center x OC y ), satisfying the formula: OC_weight_x + (OC_weight_x - Sensor_x) factor_x ； OC_weight_y + (OC_weight_y - Sensor_y) factor_y ； Where sensor_x is the X coordinate of the camera center, factor_x is the distortion factor in the X direction of the camera, sensor_y is the Y coordinate of the camera center, and factor_Y is the distortion factor in the Y direction of the camera.

8. The projector correction method according to claim 1, characterized in that, The process of selecting the pattern in the first region for defocus testing also includes the following steps: The defocus test is performed using a contrast method, and the point where the contrast is highest is the optimal position of the projector.

9. The projector correction method according to claim 1, characterized in that, The method for obtaining the position coordinates of the optical center point based on the center point coordinates of the feature points of the region pattern also includes the following steps: Multiple feature points are identified by comparing with a standard template; The position coordinates of the center point are calculated based on the feature points.

10. The projector correction method according to claim 1, characterized in that, After performing translational correction to make the center point coordinates coincide with the camera center point, the method further includes: The collimating element and the diffractive optical element are cured by dispensing and UV exposure.

11. A projector correction system, the projector comprising a collimating element and a diffractive optical element, the system comprising a camera, a clamp, and a controller, the clamp being used to fix the collimating element of the projector, characterized in that, The system is used to implement the projector correction method according to any one of claims 1-10.

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