Camera calibration method and calibration device

Abstract

The present invention provides a calibration method and a calibration device for a camera. The calibration method includes: obtaining a functional relationship between the spacing of a plurality of pixel regions and the Z-axis coordinates; obtaining the spacing of a plurality of real-time pixel regions of an initial image obtained by a camera to be calibrated at an initial position; generating a predicted Z-axis coordinate according to the spacing of the plurality of real-time pixel regions and the functional relationship; and controlling one of the lens and the photosensitive chip to move relative to the other of the lens and the photosensitive chip from the initial position to the predicted Z-axis coordinate.

Description

Technical Field

[0001] The present invention relates to the technical field of cameras, and in particular to a calibration method for a camera and a calibration device for a camera. Background Art

[0002] As consumers' requirements for photo clarity are getting higher and higher, currently, cameras applied to mobile phones, vehicles, monitoring, and televisions have higher and higher requirements for pixels. On the one hand, due to the errors generated during the module manufacturing process, it is impossible to achieve perfect precision between the optical axis center of the lens and the optical axis center of the photosensitive chip; on the other hand, due to the assembly errors during the lens lens assembly process, it will also cause the lens and the chip to not achieve the theoretical imaging effect after assembly. The AA (Active Alignment) technology has emerged as the times require.

[0003] However, the current AA technology is to clamp the COMS (Complementary Metal Oxide Semiconductor) imaging chip with a three-axis or six-axis adjustment device and light up the chip, and then gradually adjust the Z-axis position of the chip or the lens by moving up or down to achieve the best imaging effect, resulting in a longer CT (Circle Time) for producing a camera product. Summary of the Invention

[0004] Embodiments of the present invention provide a calibration method and a calibration device for a camera, which can improve the problem of a longer CT for producing a camera product.

[0005] Embodiments of the present invention provide a calibration method for a camera, which is used to calibrate a camera. The camera includes a lens and a photosensitive chip. The calibration method includes:

[0006] Obtaining the functional relationship between the distances of multiple pixel regions and the Z-axis coordinates. Each of the pixel regions includes a plurality of sub-pixels, and the Z-axis coordinate is the coordinate of the lens relative to the photosensitive chip on the Z-axis;

[0007] Obtaining the distances of multiple real-time pixel regions of an initial picture obtained by the camera to be calibrated at an initial position;

[0008] Generating a predicted Z-axis coordinate according to the distances of the multiple real-time pixel regions and the functional relationship; and

[0009] Controlling one of the lens and the photosensitive chip to move from the initial position to the predicted Z-axis coordinate relative to the other of the lens and the photosensitive chip.

[0010] In some embodiments, the step of obtaining the functional relationship between the distances of multiple pixel regions and the Z-axis coordinates includes:

[0011] Obtaining the distances of multiple sample pixel regions and multiple sample Z-axis coordinates of multiple better pictures obtained by a sample camera within a better imaging position interval, where the model of the sample camera is the same as that of the camera to be calibrated, and the clarity of the better pictures is higher than that of the pictures obtained by the sample camera at at least one other position; and

[0012] Generating the functional relationship between the distances of the pixel regions and the Z-axis coordinates based on the distances of multiple said sample pixel regions and multiple said sample Z-axis coordinates.

[0013] In some embodiments, the step of obtaining the distances of multiple sample pixel regions and multiple sample Z-axis coordinates of multiple better pictures obtained by the sample camera within a better imaging position interval includes:

[0014] Controlling the sample camera to move to a better imaging position and multiple peripheral positions around the better imaging position, where the better imaging position interval includes the better imaging position and multiple said peripheral positions; and

[0015] Obtaining the distances of multiple said sample pixel regions and multiple said sample Z-axis coordinates of multiple said better pictures obtained by the sample camera at the better imaging position and multiple said peripheral positions.

[0016] In some embodiments, the step of controlling the sample camera to move to a better imaging position and multiple peripheral positions around the better imaging position includes:

[0017] Controlling the sample camera to move to the better imaging position; and

[0018] Controlling the sample camera to move from the better imaging position as a starting point along the positive and negative directions of the Z-axis respectively to multiple said peripheral positions around the better imaging position.

[0019] In some embodiments, after the step of controlling one of the lens and the photosensitive chip to move relative to the other of the lens and the photosensitive chip to the predicted Z-axis coordinate, it further includes:

[0020] Controlling one of the lens and the photosensitive chip to move relative to the other of the lens and the photosensitive chip through at least one movement operation to move to the final Z-axis coordinate.

[0021] In some embodiments, the clarity of the picture captured by the camera at the final Z-axis coordinate is higher than that of the picture captured by the camera at the predicted Z-axis coordinate.

[0022] In some embodiments, the Z-axis moving distance corresponding to each of the movement operations is less than the Z-axis moving distance from the initial position to the predicted Z-axis coordinate.

[0023] In some embodiments, the number of the real-time pixel regions of the initial picture is not less than 5, and the number of the sample pixel regions of each of the better pictures is not less than 5.

[0024] In some embodiments, the functional relationship is a linear functional relationship.

[0025] An embodiment of the present invention further provides a calibration device for a camera, which is used to calibrate the camera. The calibration device includes: a first clamping module for clamping the lens of the camera; a second clamping module for clamping the photosensitive chip of the camera; a memory for storing program instructions; and a processor electrically connected to the memory, the photosensitive chip, and at least one of the first clamping module and the second clamping module. The processor is configured to execute the program instructions to implement the calibration method as described above.

[0026] In the calibration method and calibration device for a camera provided by the embodiment of the present invention, the predicted Z-axis coordinates of the lens and the photosensitive chip of the camera to be calibrated are predicted through the functional relationship between the distances between multiple pixel regions and the Z-axis coordinates, and one of the lens and the photosensitive chip is controlled to move from the initial position to the predicted Z-axis coordinate relative to the other of the lens and the photosensitive chip, skipping multiple intermediate positions between gradually calibrating from the initial position to the predicted Z-axis coordinate in the prior art. Thus, the problem of the relatively long cycle time for producing one camera product is improved. Description of the Drawings

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative efforts.

[0028] Figure 1 is a working schematic diagram of the calibration device for a camera provided by an embodiment of the present invention;

[0029] Figure 2 is Figure 1 a module schematic diagram of the calibration device for the camera in

[0030] Figure 3A is Figure 1 a schematic diagram of the image captured by the camera in

[0031] Figure 3B is Figure 1 a functional relationship diagram of the distance between the relative Z-axis coordinates of the lens and the photosensitive chip of the camera in

[0032] Figure 4 a schematic flowchart of the camera calibration method provided by an embodiment of the present invention;

[0033] Figure 5 is Figure 4 a schematic diagram of the change of the MTF value of the picture taken by the camera in

[0034] Figure 6 is Figure 4 a schematic flowchart of step S1 in Detailed implementation manners

[0035] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present invention. In addition, it should be understood that the specific implementation manners described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention. In the present invention, unless otherwise stated, the orientation words such as "upper" and "lower" usually refer to the upper and lower in the actual use or working state of the device, specifically the plane direction in the drawings; and "inner" and "outer" refer to the outline of the device.

[0036] As Figure 1 and Figure 2 shown, an embodiment of the present invention provides a camera calibration device 100, including a first clamping module 1, a second clamping module 2, a processor 3, and a memory 4. The camera 6 includes a lens 60 and a photosensitive chip 61. The calibration device 100 of the camera 6 is used to calibrate the relative positions of the lens 60 and the photosensitive chip 61 in the Z-axis direction ( Figure 1 the Z direction in

[0037] The first clamping module 1 can be a three-axis or six-axis gripper for clamping the lens 60.

[0038] The second clamping module 2 can be a three-axis or six-axis gripper for clamping the photosensitive chip 61. Among them, the second clamping module 2 is used to clamp the circuit board 21 (PCB, Printed Circuit Board), and the circuit board 21 is used to be electrically connected to the photosensitive chip 61 to light up the photosensitive chip 61.

[0039] The memory 4 is electrically connected to the processor 3 and is used to store a plurality of program instructions. Exemplarily, the memory 4 can be arranged on the circuit board 21. The memory 4 can be a non-permanent memory in a computer-readable medium, in the form of a random access memory (Random Access Memory, RAM) and / or a non-volatile memory, such as a read-only memory (Read-Only Memory, ROM) or a flash memory (Flash RAM).

[0040] The processor 3 is electrically connected to the first clamping module 1 and / or the second clamping module 2 to control the movement of the first clamping module 1 and / or the second clamping module 2. The processor 3 is also electrically connected to the photosensitive chip 61 to process the picture 70 taken by the photosensitive chip 61 through the lens 60. Exemplarily, the processor 3 can be arranged on the circuit board 21. The processor 3 can be a micro controller unit (MCU), an integrated chip, a control circuit, etc. The processor 3 is used to execute a plurality of the program instructions to implement a calibration method for a camera.

[0041] Please refer to Figure 4 , the calibration method of the camera includes:

[0042] Step S1, obtaining the functional relationship between the spacing of multiple pixel regions and the Z-axis coordinates.

[0043] As Figure 3A shown, through experiments, the inventor found that the spacing P between multiple pixel regions 71 (i.e., Blocks, including multiple sub-pixels) at the best position (i.e., the best clear position) of the picture 70 taken by camera products of the same model approaches a fixed value. Exemplarily, the spacing between 5 or more pixel regions at the best clear position of the picture taken by the first camera is approximately equal to the spacing between 5 or more pixel regions at the best clarity position of the picture taken by the second camera of the same model. As Figure 3BAs shown, the inventor also found that there is a stable functional relationship between the pitch P between multiple pixel regions 71 and the Z-axis coordinate, where the Z-axis coordinate is the Z-axis coordinate of the lens 60 relative to the photosensitive chip 61. Thus, the inventor utilized this law and proposed an inventive concept of saving the calibration time of other products during the production process by automatically learning the optimal clear position once for the same batch of camera products. Therefore, the functional relationship between the pitch P of multiple pixel regions of the same model product and the Z-axis coordinate can be stored in the instruction library of the memory 4 for the processor 3 to obtain.

[0044] Specifically, the numerical index for measuring the clarity of the picture 70 can adopt the spatial frequency response function (SFR) or the modulation transfer function (MTF) at a selected frequency.

[0045] Step S2: Obtain the pitches of multiple real-time pixel regions of the initial picture obtained by the camera to be calibrated at the initial position.

[0046] Please refer to Figure 5 , Figure 5 is a schematic diagram of the change of the MTF value of the picture taken by the camera relative to the Z-axis coordinate. By controlling the camera 6 to take pictures at the initial position (i.e., the starting position Z0), the processor 3 can obtain the initial picture of the camera 6 at the initial position. By analyzing the data of the initial picture, the processor 3 can obtain the pitches of multiple real-time pixel regions at the optimal clarity position.

[0047] Step S3: Generate a predicted Z-axis coordinate according to the pitches of multiple real-time pixel regions and the functional relationship.

[0048] Please refer to Figure 5 , by substituting the pitches of multiple real-time pixel regions into the functional relationship, the processor 3 can obtain the corresponding Z-axis coordinate and use the obtained Z-axis coordinate as the predicted Z-axis coordinate (i.e., the predicted position Z6).

[0049] Step S4: Control one of the lens 60 and the photosensitive chip 61 to move from the initial position to the predicted Z-axis coordinate relative to the other of the lens 60 and the photosensitive chip 61.

[0050] Please refer to Figure 5, the processor 3 sends the Z-axis coordinate to the first clamping module 1 and / or the second clamping module 2, and controls the first clamping module 1 and / or the second clamping module 2 to move, so that one of the lens 60 and the photosensitive chip 61 clamped by the first clamping module 1 and the second clamping module 2 moves relative to the other of the lens 60 and the photosensitive chip 61 from the initial position to the predicted Z-axis coordinate. In this way, one of the lens 60 and the photosensitive chip 61 moves directly from the starting position Z0 to the predicted position Z6 relative to the other of the lens 60 and the photosensitive chip 61, skipping a plurality of intermediate positions, such as Z1-Z5 (please see the shaded part in the figure) in the prior art for gradually adjusting from the starting position Z0 to the predicted position Z6, and reducing the adjustment time of the lens 60 and the photosensitive chip 61.

[0051] Step S5: Control one of the lens 60 and the photosensitive chip 61 to move relative to the other of the lens 60 and the photosensitive chip 61 through at least one movement operation to move to the final Z-axis coordinate.

[0052] Please refer to Figure 5 , since the predicted Z-axis coordinate is not necessarily the Z-axis coordinate corresponding to the optimal imaging position, after controlling the camera 6 to reach the predicted Z-axis coordinate, the processor 3 can further control the first clamping module 1 and / or the second clamping module 2 to perform at least one movement operation, so that one of the lens 60 and the photosensitive chip 61 moves relative to the other of the lens 60 and the photosensitive chip 61 to the final Z-axis coordinate (i.e., the end position Z11). Exemplarily, the final Z-axis coordinate may be the Z-axis coordinate corresponding to the optimal imaging position (i.e., the optimal position Z8), and the clarity of the picture obtained by the camera 6 at the final Z-axis coordinate is higher than the clarity of the picture obtained by the camera 6 at the predicted Z-axis coordinate.

[0053] Since in step S4, the camera 6 is controlled to directly move from the initial position to the predicted Z-axis coordinate by applying the calibration rule discovered by the inventor, the calibrated camera 6 is already close to the final Z-axis coordinate corresponding to the optimal imaging position. Therefore, next, only the Z-axis coordinate of the lens 60 of the calibrated camera 6 relative to the photosensitive chip 61 needs to be finely adjusted to quickly reach the final Z-axis coordinate. Therefore, the Z-axis moving distance corresponding to each movement operation (i.e., the fine adjustment operation) is less than the Z-axis moving distance from the initial position to the predicted Z-axis coordinate.

[0054] Please refer to Figure 6 , further, the step S1 includes:

[0055] S10. Obtain the distances between multiple sample pixel regions and multiple sample Z-axis coordinates of multiple better pictures obtained by a sample camera within a better imaging position range, where the sample camera has the same model as the camera 6 to be calibrated.

[0056] The better imaging position range includes a better imaging position and multiple peripheral positions. The processor 3 controls the first clamping module 1 and / or the second clamping module 2 to move multiple times, and controls the next movement parameters by analyzing the clarity of the picture taken at the movement position reached in the previous movement. Eventually, it can control one of the lens and the photosensitive chip of the sample camera to move relative to the other of the lens and the photosensitive chip to the better imaging position. Among them, the clarity of the better picture corresponding to the better imaging position is higher than the clarity of the pictures obtained by the sample camera at at least one other position. For example, the better imaging position can be the optimal imaging position.

[0057] Further, starting from the better imaging position, the processor 3 controls the first clamping module 1 and / or the second clamping module 2 to move, so as to control one of the lens and the photosensitive chip of the sample camera to move relative to the other of the lens and the photosensitive chip along the positive and negative directions of the Z-axis respectively at intervals of a certain distance (such as 10 microns) for multiple times, so as to move to multiple peripheral positions around the better imaging position. Exemplarily, the number of multiple peripheral positions can be 10.

[0058] The processor 3 processes the multiple better pictures obtained by the sample camera at the better imaging position and multiple peripheral positions, so as to obtain the distances between multiple sample pixel regions and multiple sample Z-axis coordinates.

[0059] S11. Generate the functional relationship between the distance of the pixel region and the Z-axis coordinate according to the distances between multiple sample pixel regions and multiple sample Z-axis coordinates.

[0060] The processor 3 can generate the functional relationship between the distance of the pixel region and the Z-axis coordinate of a camera with the same model as the sample camera by analyzing the obtained distances between multiple sample pixel regions and multiple sample Z-axis coordinates. Through further experiments, it is found that the distance of the pixel region and the Z-axis coordinate show a stable linear relationship.

[0061] The above has introduced the embodiments of the present invention in detail. Specific examples are used herein to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those skilled in the art, according to the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A calibration method for a camera, used to calibrate the camera, the camera including a lens and an image sensor chip, characterized in that, The calibration method includes: Obtaining the functional relationship between the spacing of multiple pixel regions and the Z-axis coordinate, each of the pixel regions including a plurality of sub-pixels, and the Z-axis coordinate being the Z-axis coordinate of the lens relative to the photosensitive chip; Obtaining the spacing of multiple real-time pixel regions of an initial image obtained by a camera to be calibrated at an initial position; Generating a predicted Z-axis coordinate according to the spacing of the multiple real-time pixel regions and the functional relationship; and Controlling one of the lens and the photosensitive chip to move from the initial position to the predicted Z-axis coordinate relative to the other of the lens and the photosensitive chip; Wherein, the step of obtaining the functional relationship between the spacing of multiple pixel regions and the Z-axis coordinate includes: Obtaining the spacing of multiple sample pixel regions and multiple sample Z-axis coordinates of multiple better images obtained by a sample camera within a better imaging position interval, the sample camera having the same model as the camera to be calibrated, and the clarity of the better images being higher than that of images obtained by the sample camera at at least one other position; and Generating the functional relationship between the spacing of the pixel regions and the Z-axis coordinate according to the spacing of the multiple sample pixel regions and the multiple sample Z-axis coordinates.

2. The calibration method for a camera according to claim 1, characterized in that, The step of obtaining the spacing of multiple sample pixel regions and multiple sample Z-axis coordinates of multiple better images obtained by the sample camera within the better imaging position interval includes: Controlling the sample camera to move to a better imaging position and multiple peripheral positions around the better imaging position, the better imaging position interval including the better imaging position and the multiple peripheral positions; and Obtaining the spacing of the multiple sample pixel regions and the multiple sample Z-axis coordinates of the multiple better images obtained by the sample camera at the better imaging position and the multiple peripheral positions.

3. The calibration method for a camera according to claim 2, characterized in that, The step of controlling the sample camera to move to a better imaging position and multiple peripheral positions around the better imaging position includes: Controlling the sample camera to move to the better imaging position; and Controlling the sample camera to move from the better imaging position as a starting point to the multiple peripheral positions around the better imaging position along the positive and negative directions of the Z-axis respectively.

4. The calibration method for a camera according to claim 1, characterized in that, After the step of controlling one of the lens and the photosensitive chip to move to the predicted Z-axis coordinate relative to the other of the lens and the photosensitive chip, it further includes: Controlling one of the lens and the photosensitive chip to move to a final Z-axis coordinate relative to the other of the lens and the photosensitive chip through at least one movement operation.

5. The calibration method for a camera according to claim 4, characterized in that, The clarity of the image obtained by the camera at the final Z-axis coordinate is higher than that of the image obtained by the camera at the predicted Z-axis coordinate.

6. The calibration method for a camera according to claim 4, characterized in that, The Z-axis moving distance corresponding to each movement operation is less than the Z-axis moving distance from the initial position to the predicted Z-axis coordinate.

7. The calibration method for a camera according to claim 1, characterized in that, The number of the multiple real-time pixel regions of the initial image is not less than 5, and the number of the sample pixel regions of each better image is not less than 5.

8. The calibration method for a camera according to claim 1, characterized in that, The functional relationship is a linear functional relationship.

9. A calibration device for a camera, used to calibrate the camera, characterized in that, including: The first clamping module is used to clamp the lens of the camera; The second clamping module is used to clamp the photosensitive chip of the camera; The memory is used to store program instructions; And The processor is electrically connected to the memory, the photosensitive chip, and at least one of the first clamping module and the second clamping module. The processor is used to execute the program instructions to implement the calibration method according to any one of claims 1 to 8.

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