Rapid correction mechanism and method for projector

Abstract

The invention discloses a rapid correction mechanism and method for a projector, and the method comprises the following correction steps: S1, starting correction, and carrying out the initialization and self-inspection of a system; s2, judging whether a correction triggering condition is met or not; if the conditions are met, the step S3 is carried out; otherwise, maintaining the current state; s3, projecting a first test pattern, and capturing a projection image of the first test pattern; s4, calculating the geometric distortion amount of the current picture based on the captured image, and solving a first digital correction parameter C1 according to the geometric distortion amount; s5, calculating an effective pixel utilization rate eta after the first digital correction parameter C1 is applied, wherein the value range of eta is 0-1; according to the invention, by introducing a quantitative index, namely an effective pixel utilization rate eta, an intelligent decision-making system starts high-cost optical compensation only when image quality loss is unacceptable, and efficient pure digital correction is adopted for daily slight displacement and inclination, so that a user can obtain nearly lossless image quality experience under most conditions, and the user experience is improved. And meanwhile, convenience brought by automatic correction is enjoyed.

Description

Technical Field

[0001] This invention relates to the field of image processing and projection display technology, and in particular to a rapid calibration mechanism and method for a projector. Background Technology

[0002] One of the key functions of smart projectors is automatic keystone correction, which aims to automatically correct the distorted trapezoidal image into a regular rectangle when the projector deviates from the projection position. Currently, the mainstream automatic keystone correction technologies in the industry are mainly divided into two categories: pure digital correction and correction based on optical lens shift. However, both of these technical approaches have obvious limitations and cannot achieve a good balance between image quality, cost, and efficiency.

[0003] Pure digital keystone correction technology is currently the most popular solution in consumer projectors. Its basic principle is to detect the geometric distortion of the image through a built-in sensor or camera, and then perform a reverse geometric transformation on the original image through image processing algorithms. The distortion is compensated by cropping, scaling and interpolation, so that the projected image is restored to a rectangle. Pure optical lens shift correction technology is a solution for high-end professional projectors. It changes the light path by precisely moving the position of the lens or lens group, and directly corrects the shape of the projected image physically, thereby achieving keystone correction.

[0004] While purely digital correction schemes are low-cost and fast, their method of cropping and scaling images inevitably leads to a loss of effective pixels and a decline in image quality, failing to meet users' demands for high definition. Purely optical correction schemes, on the other hand, can achieve lossless image quality, but their reliance on complex and precise optical-mechanical structures results in high costs and large size, hindering their widespread adoption in the consumer market. Existing technologies also include some correction schemes that combine optical and digital technologies, but their correction logic is usually fixed and non-intelligent. Regardless of the size of the distortion, they employ a fixed optical-digital correction sequence, failing to adaptively select the optimal strategy based on the degree of distortion. This results in insufficient efficiency for minor distortion and limited image quality improvement for severe distortion. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, the present invention aims to provide a rapid correction mechanism and method for projectors. By introducing the quantitative indicator of effective pixel utilization (η), the intelligent decision-making system only initiates high-cost optical compensation when the image quality loss is unacceptable (η < η_threshold). For minor everyday displacement and tilt (η ≥ η_threshold), efficient pure digital correction is used, so that users can obtain a near-lossless image quality experience in most cases, while also enjoying the convenience brought by automatic correction.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A rapid calibration mechanism and method for a projector, comprising the following calibration steps:

[0008] S1. Start calibration; the system initializes and performs self-test.

[0009] S2. Determine whether the correction trigger condition is met; if the condition is met, proceed to step S3; otherwise, maintain the current state.

[0010] S3. Project the first test pattern and capture its projected image;

[0011] S4. Based on the captured image, calculate the geometric distortion of the current frame, and solve for the first digital correction parameter C1 accordingly;

[0012] S5. Calculate the effective pixel utilization rate η after applying the first digital correction parameter C1, where the value of η ranges from 0 to 1.

[0013] S6. Determine whether the effective pixel utilization rate η is lower than the preset threshold η_threshold;

[0014] If η ≥ η_threshold, then proceed to step S9;

[0015] If η < η_threshold, then proceed to step S7;

[0016] S7. Drive the optical compensation device to partially compensate for image distortion.

[0017] S8. After optical compensation, recalculate the second digital correction parameter C2, and then proceed to step S9.

[0018] S9. Apply the final digital correction parameters to correct the image and complete the final focus;

[0019] S10, The calibration process is complete, and the output screen is displayed.

[0020] In one optional implementation, the triggering conditions in step S2 include: detecting a change in the projector's attitude angle exceeding a preset threshold, or receiving a user's manual correction command.

[0021] In one optional implementation, the specific operation of "calculating the first digital correction parameter C1" in step S4 is as follows:

[0022] S41. Project a predefined ideal test pattern;

[0023] S42. Capture the image of the distortion test pattern caused by the projection environment using the built-in camera;

[0024] S43. Process the distorted image and extract the pixel coordinates of its key feature points;

[0025] S44. Match the extracted feature point coordinates with the corresponding feature point coordinates in the ideal test pattern to obtain at least 4 sets of matching point pairs;

[0026] S45. Based on the multiple sets of matching point pairs, the homography matrix is ​​calculated by solving the perspective transformation model and used as the first digital correction parameter C1.

[0027] In one optional implementation, the "solving the perspective transformation model" in step S45 employs a direct linear transformation algorithm.

[0028] In one optional implementation, the effective pixel utilization rate η in step S5 is a quality loss assessment parameter, which characterizes the ratio of the pixel area of ​​the effective display area after digital correction to the total area of ​​the projector's original physical pixels.

[0029] In one optional implementation, the specific steps for "calculating the effective pixel utilization rate η" in step S6 are as follows:

[0030] S61. Define the original physical resolution width and height of the projector display chip as W_native and H_native, respectively;

[0031] S62. Map the boundary point coordinates of the original resolution image through the inverse transformation of the first digital correction parameter C1 to obtain the area occupied by the corrected image in the original pixel coordinate system.

[0032] S63. Calculate the width W_corrected and height H_corrected of the minimum bounding rectangle of the region;

[0033] S64. Calculate the effective pixel utilization rate η = (W_corrected × H_corrected) / (W_native × H_native).

[0034] In one optional implementation, the specific operation of "driving the optical compensation device to partially compensate for image distortion" in step S7 is as follows:

[0035] S71. Perform matrix decomposition on the first digital correction parameter C1, and decompose the geometric transformation it implies into high image quality loss components and low image quality loss components.

[0036] S72. Convert the high-quality loss component into the target driving quantity of the optical compensation device;

[0037] S73. Drive the optical compensation device to execute the target driving amount, and use closed-loop control to make its actual output amount approach the target driving amount.

[0038] In one optional implementation, the high-quality loss components in step S71 mainly include rotation transformation and shearing transformation, and the low-quality loss components mainly include translation transformation and scaling transformation.

[0039] In one optional implementation, the specific steps of "recalculating the second digital correction parameter C2" in step S8 are as follows:

[0040] S81. After optical compensation, project the second test pattern and capture its projected image;

[0041] S82. Based on the newly captured image, calculate the residual distortion of the image;

[0042] S83. Solve for the second digital correction parameter C2 based on the residual distortion.

[0043] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0044] 1. By introducing the quantitative indicator of effective pixel utilization (η), the intelligent decision-making system only activates high-cost optical compensation when the loss of image quality is unacceptable (η < η_threshold). For minor displacement and tilt in daily life (η ≥ η_threshold), it adopts efficient pure digital correction, so that users can obtain a near-lossless image quality experience in most cases, while also enjoying the convenience brought by automatic correction.

[0045] 2. Since the optical mechanism only starts working when necessary, the number of its actions and the range of motion are greatly reduced, thereby reducing mechanical wear, reducing the failure rate, and improving the long-term reliability of the entire system.

[0046] 3. The requirement of this invention for the optical compensation mechanism is "auxiliary compensation" rather than "independent completion of all corrections". Therefore, it is not necessary to design a complex optical-mechanical structure with a long stroke, extremely high precision and high cost. A micro swing mechanism with a short stroke and controllable cost can meet the requirements. The lack of hardware cost is made up for by algorithm innovation, so that high-performance correction function can be popularized in mainstream consumer products.

[0047] 4. The image quality protection threshold (η_threshold) can be used as an adjustable parameter. Users who are extremely demanding in terms of image quality can increase the threshold (e.g., 95%) to force the system to use optical compensation more frequently to ensure image quality. Users who are sensitive to speed can appropriately decrease the threshold (e.g., 85%) to make the system more inclined to use fast digital correction, providing a personalized user experience. Attached Figure Description

[0048] Figure 1 This is a flowchart illustrating a rapid calibration mechanism and method for a projector.

[0049] Figure 2 A flowchart illustrating the calculation method of the first digital correction parameter C1 in a rapid correction mechanism and method for a projector;

[0050] Figure 3 This is a flowchart illustrating the calculation method for the effective pixel utilization η of a projector's rapid calibration mechanism and method. Detailed Implementation

[0051] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0052] Please refer to Figure 1-3 A rapid calibration mechanism and method for a projector, wherein the calibration steps are as follows:

[0053] S1. Start calibration; the system initializes and performs self-test.

[0054] S2. Determine whether the correction trigger condition is met; if the condition is met, proceed to step S3; otherwise, maintain the current state.

[0055] S3. Project the first test pattern and capture its projected image;

[0056] S4. Based on the captured image, calculate the geometric distortion of the current frame, and solve for the first digital correction parameter C1 accordingly;

[0057] S5. Calculate the effective pixel utilization rate η after applying the first digital correction parameter C1, where the value of η ranges from 0 to 1.

[0058] S6. Determine whether the effective pixel utilization rate η is lower than the preset threshold η_threshold;

[0059] If η ≥ η_threshold, then proceed to step S9;

[0060] If η < η_threshold, then proceed to step S7;

[0061] S7. Drive the optical compensation device to partially compensate for image distortion.

[0062] S8. After optical compensation, recalculate the second digital correction parameter C2, and then proceed to step S9.

[0063] S9. Apply the final digital correction parameters to correct the image and complete the final focus;

[0064] S10, The calibration process is complete, and the output screen is displayed.

[0065] In a preferred embodiment of the present invention, the triggering conditions in step S2 include: detecting that the change in the projector's attitude angle exceeds a preset threshold, or receiving a user's manual correction command.

[0066] In a preferred embodiment of the present invention, the specific operation of "calculating the first digital correction parameter C1" in step S4 is as follows:

[0067] S41. Project a predefined ideal test pattern;

[0068] S42. Capture the image of the distortion test pattern caused by the projection environment using the built-in camera;

[0069] S43. Process the distorted image and extract the pixel coordinates of its key feature points;

[0070] S44. Match the extracted feature point coordinates with the corresponding feature point coordinates in the ideal test pattern to obtain at least 4 sets of matching point pairs;

[0071] S45. Based on the multiple sets of matching point pairs, the homography matrix is ​​calculated by solving the perspective transformation model and used as the first digital correction parameter C1.

[0072] In a preferred embodiment of the present invention, the "solving the perspective transformation model" in step S45 adopts the direct linear transformation algorithm.

[0073] In a preferred embodiment of the present invention, the effective pixel utilization rate η in step S5 is a parameter for evaluating image quality loss, which represents the ratio of the pixel area of ​​the effective display area after digital correction to the total area of ​​the original physical pixels of the projector.

[0074] In a preferred embodiment of the present invention, the specific steps for "calculating the effective pixel utilization rate η" in step S6 are as follows:

[0075] S61. Define the original physical resolution width and height of the projector display chip as W_native and H_native, respectively;

[0076] S62. Map the boundary point coordinates of the original resolution image through the inverse transformation of the first digital correction parameter C1 to obtain the area occupied by the corrected image in the original pixel coordinate system.

[0077] S63. Calculate the width W_corrected and height H_corrected of the minimum bounding rectangle of the region;

[0078] S64. Calculate the effective pixel utilization rate η = (W_corrected × H_corrected) / (W_native × H_native).

[0079] In a preferred embodiment of the present invention, the specific operation of "driving the optical compensation device to partially compensate for image distortion" in step S7 is as follows:

[0080] S71. Perform matrix decomposition on the first digital correction parameter C1, and decompose the geometric transformation it implies into high image quality loss components and low image quality loss components.

[0081] S72. Convert the high-quality loss component into the target driving quantity of the optical compensation device;

[0082] S73. Drive the optical compensation device to execute the target driving amount, and use closed-loop control to make its actual output amount approach the target driving amount.

[0083] In a preferred embodiment of the present invention, the high-quality loss components in step S71 mainly include rotation transformation and shearing transformation, and the low-quality loss components mainly include translation transformation and scaling transformation.

[0084] In a preferred embodiment of the present invention, the specific steps of "recalculating the second digital correction parameter C2" in step S8 are as follows:

[0085] S81. After optical compensation, project the second test pattern and capture its projected image;

[0086] S82. Based on the newly captured image, calculate the residual distortion of the image;

[0087] S83. Solve for the second digital correction parameter C2 based on the residual distortion.

[0088] Working principle: When the user moves the projector from the coffee table to the desk and turns it on, the rapid calibration process is triggered. The IMU (Inertial Measurement Unit) senses the angle change, the system starts, the projector projects a checkerboard test pattern, the camera captures the image, the processor identifies the corner points and calculates the homography matrix to obtain the first digital calibration parameter C1, and calculates the effective pixel utilization rate η after applying C1. The calculation shows that η = 75% (i.e., the image quality loss reaches 25%), which is lower than the preset threshold of 90%. The system determines that hybrid calibration needs to be started, performs matrix decomposition on C1, and obtains the rotation / shearing components mainly compensated by lens deflection. Drives the lens swing mechanism to move to the target angle for optical compensation. After compensation, a simplified pattern is projected again, and the second digital calibration parameter C2 is calculated. At this time, the new effective pixel utilization rate η_optimized is calculated, and its value has been improved to 98%. The optimized parameter C2 is applied, and the final focus is performed. The entire process is completed within 3 seconds, and the user obtains a clear, square, and almost lossless projected image on the desk.

[0089] Although only certain components and embodiments of this application have been illustrated and described, many modifications and alterations (e.g., variations in the size, dimensions, structure, shape and proportion of the various elements, installation arrangement, material use, color, orientation, etc.) will be conceived by those skilled in the art without actually departing from the scope and spirit of the claims.

[0090] Finally, it should be noted that the above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A fast correction mechanism and method for a projector, characterized by, The correction steps are as follows: S1, start correction, the system is initialized and self-checked; S2, determine whether the correction trigger condition is met; if the condition is met, proceed to step S3; otherwise, maintain the current state; S3, project the first test pattern and capture its projection image; S4, based on the captured image, calculate the geometric distortion of the current picture, and solve the first digital correction parameter C1 accordingly; S5, calculate the effective pixel utilization rate η after applying the first digital correction parameter C1, wherein η ranges from 0 to 1, wherein η ranges from 0 to 1; S6, determine whether the effective pixel utilization rate η is lower than the preset threshold η_threshold, wherein η_threshold ranges from 0 to 1; If η ≥ η_threshold, proceed to step S9; If η < η_threshold, proceed to step S7; S7, drive the optical compensation device to partially compensate for the picture distortion; S8, after optical compensation, recalculate the second digital correction parameter C2, and then proceed to step S9; S9, apply the final digital correction parameter to correct the picture and complete the final focusing; S10, the correction process is completed, and the picture is output.

2. The quick correction mechanism and method for a projector according to claim 1, wherein, The trigger condition in step S2 includes detecting that the projector pose angle changes more than a preset threshold, or receiving a user manual correction instruction.

3. The fast correction mechanism and method for a projector according to claim 1, wherein, The specific operation of "calculating the first digital correction parameter C1" in step S4 is as follows: S41, project a predefined ideal test pattern; S42, capture the distorted test pattern image caused by the projection environment through the built-in camera; S43, process the distorted image and extract the pixel coordinates of its key feature points; S44, match the extracted feature point coordinates with the corresponding feature point coordinates in the ideal test pattern to obtain at least 4 matching point pairs; S45, according to the at least 4 matching point pairs, calculate the homography matrix as the first digital correction parameter C1 by solving the perspective transformation model.

4. The quick correction mechanism and method for a projector according to claim 3, wherein: The "solving the perspective transformation model" in step S45 uses the direct linear transformation algorithm.

5. The quick correction mechanism and method for a projector according to claim 1, wherein: The effective pixel utilization rate η in step S5 is a picture quality loss evaluation parameter, which represents the ratio of the pixel area of the effective display area after applying digital correction to the total area of the original physical pixels of the projector.

6. The quick correction mechanism and method for a projector according to claim 1, wherein, The specific steps of "calculating the effective pixel utilization rate η" in step S6 are as follows: S61, define the original physical resolution width and height of the projector display chip as W_native and H_native respectively; S62, map the boundary point coordinates of the original resolution picture through the inverse transformation of the first digital correction parameter C1 to obtain the area occupied by the corrected picture in the original pixel coordinate system; S63, calculate the width W_corrected and height H_corrected of the minimum bounding rectangle of the area; S64, calculate the effective pixel utilization rate η = (W_corrected × H_corrected) / (W_native × H_native).

7. The quick correction mechanism and method for a projector according to claim 1, wherein, The detailed operation of "driving the optical compensation device to partially compensate the screen distortion" in step S7 is as follows: S71, matrix decomposition is performed on the first digital correction parameter C1 to decompose the geometric transformation contained therein into a high-quality loss component and a low-quality loss component; S72, the high-quality loss component is converted into a target driving amount of the optical compensation device; S73, the optical compensation device is driven to execute the target driving amount, and a closed-loop control is adopted to make the actual output of the optical compensation device close to the target driving amount.

8. A fast correction mechanism and method for a projector according to claim 7, characterized in that: The high-quality loss component in step S71 mainly includes rotation transformation and shear transformation, and the low-quality loss component mainly includes translation transformation and scaling transformation.

9. The fast correction mechanism and method for a projector according to claim 1, wherein, The detailed operation of "recomputing the second digital correction parameter C2" in step S8 is as follows: S81, after optical compensation, a second test pattern is projected and a projection image thereof is captured; S82, based on the newly captured image, a residual distortion amount of the screen is calculated; S83, the second digital correction parameter C2 is solved according to the residual distortion amount.

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