Automatic alignment method of multi-group periscopic camera module

Abstract

The invention discloses an automatic alignment method of a multi-group periscopic camera module, and belongs to the technical field of camera modules, a second group of lenses are assembled in a voice coil motor iron shell, automatic focusing movement can be realized, a basis is provided for a focusing function, and a third group of lenses are assembled through structural assembly equipment. Adjusting the inclination angle between the second group of lenses and the third group of lenses to be not more than 0.2 degree by using a line scanning camera, and determining a distance reference value between the third group of lenses and the second group of lenses by taking the current value of the far-focus motor as a target; meanwhile, the physical centers of the second group of lenses and the third group of lenses are aligned by using a visual camera, the eccentricity does not exceed 50 microns, and after the primary processing of the two lens groups is completed, the displacement and inclination angle of the first group of lenses matched with the image sensor are adjusted by adopting an image algorithm for the first group of lenses and the image sensor, so that accurate assembly is realized. Through the optimized image algorithm, strict requirements of a high-end camera module on image definition, detail reduction degree and the like can be met.

Description

Technical Field

[0001] This invention belongs to the field of camera module technology, and particularly relates to an automatic alignment method for a multi-group periscope camera module. Background Technology

[0002] With the development of periscope camera modules, the technology has evolved from two-element lens groups to multi-element lens groups, and may even rival the dozen or more lens groups in SLR lenses in the future. During the production of camera modules, the assembly precision of the lens groups significantly affects image quality. To achieve high-resolution, high-quality image capture, precise alignment between each lens group and the sensor is crucial.

[0003] Traditional assembly processes often rely on manual operation or simple mechanical alignment methods, which are insufficient to meet the requirements of modern high-precision camera modules. For example, in multi-lens camera modules, the tilt angle, spacing, and relative positional deviation of each lens group with the sensor can significantly affect key image parameters such as resolution, astigmatism, and linear astigmatism, leading to problems such as blurring and distortion in the captured images. Therefore, an automatic alignment method for multi-group periscope camera modules is needed. Summary of the Invention

[0004] This invention overcomes the shortcomings of the prior art and provides an automatic alignment method for a multi-group periscope camera module to solve the problems existing in the prior art.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is: an automatic alignment method for a multi-group periscope camera module, comprising the following steps:

[0006] S1. Assemble the second and third groups of lenses in the multi-lens camera module. Assemble the second group of lenses in the voice coil motor housing so that it can move for automatic focusing. Use the structural assembly equipment and line scan camera to adjust the tilt angle between the second and third groups of lenses to no more than 0.2°. Determine the distance between the second and third groups of lenses based on the current value of the telephoto motor. Use a vision camera to align the physical centers of the second and third groups of lenses, with an eccentricity of no more than 50µm.

[0007] S2. The spatial frequency response function algorithm is used to calculate the image resolution. The calculation area is the central area plus 5 regions of 0.8 field of view rhombus. The spatial frequency response function values ​​are obtained in the horizontal and vertical directions. The autofocus motor drives the second group of lenses to scan the defocus curve. Based on the curve, multiple test indicators are defined, including the peak motor current value of each region, the horizontal and vertical separation value of the field of view region, astigmatism and linear astigmatism.

[0008] S3. Collect the degree-of-freedom and sensitivity data of the first group of lenses and the image sensor, oscillate the degree-of-freedom of the first group of lenses around the X-axis and the Y-axis, and the degree-of-freedom of the image sensor around the X-axis and the Y-axis, analyze their correlation with astigmatism and linear astigmatism, and establish a quaternary linear polynomial equation to solve for the position of pixel linear astigmatism and astigmatism.

[0009] S4. When the second group of lens motors stops at the center Peak position, move the first group of lenses by translating along the X-axis and along the Y-axis, take images and calculate the center spatial frequency response function value. Determine the position of the translation motors along the X-axis and along the Y-axis corresponding to the maximum spatial frequency response function value through curve fitting, and swing the first group of lenses to that position.

[0010] In a preferred embodiment of the present invention, the method for determining the calculation area of ​​the spatial frequency response function algorithm and the definition of each test index are as follows: the calculation area is selected from five regions including the central region plus a 0.8 field of view rhombus. Five points are selected in the horizontal and vertical directions to calculate the spatial frequency response function value, for a total of 10 points. The peak motor current value of each curve is defined as the CT_H_Peak motor current value and CT_V_Peak motor current value of the central region, and the F08_UL_H_Peak and F08_UL_V_Peak of each corner region of the F08 field of view. The horizontal and vertical separation value, left and right astigmatism, up and down astigmatism, left and right linear astigmatism, and up and down linear astigmatism of the field of view are calculated through these peak motor current values.

[0011] In a preferred embodiment of the present invention, the four-variable linear polynomial equations are established as A1x1+B1x2+C1x3+D1x4=y1, A2x1+B2x2+C2x3+D2x4=y2, A3x1+B3x2+C3x3+D3x4=y3, and A4x1+B4x2+C4x3+D4x4=y4, where x1 = the degree of freedom of rotation of the first group of lenses around the X-axis, x2 = the degree of freedom of rotation of the first group of lenses around the Y-axis, x3 = the degree of freedom of rotation of the image sensor around the X-axis, and x4 = the degree of freedom of rotation of the image sensor around the Y-axis. A1-D4 are coefficients determined based on the correlation between the degrees of freedom of the first group of lenses and the image sensor and astigmatism and linear astigmatism. If there is no correlation, the coefficients are 0.

[0012] In a preferred embodiment of the present invention, y1 represents left-right line astigmatism, y2 represents top-bottom line astigmatism, y3 represents left-right image astigmatism, and y4 represents top-bottom image astigmatism.

[0013] In a preferred embodiment of the present invention, the parameters of the translational attitude along the X-axis and along the Y-axis of the first group of lenses are ±0.15mm, the step size is 0.025mm, and 12 images are captured for each movement to calculate the center spatial frequency response function value.

[0014] The present invention also discloses a multi-group periscope camera module, which is assembled and optimized using the aforementioned automatic alignment method for a multi-group periscope camera module.

[0015] This invention addresses the shortcomings of the prior art and has the following beneficial effects:

[0016] 1. Through optimized image algorithms, astigmatism and linear astigmatism are effectively reduced, and image resolution is improved. As can be clearly seen from the curve effect display, the peak motor current values ​​in each area are more ideal after adjustment, and the image quality is significantly improved, which can meet the strict requirements of high-end camera modules for image clarity, detail reproduction, etc.

[0017] 2. The automatic alignment method of the present invention realizes the automated assembly and adjustment process of the camera module. Compared with the traditional manual assembly and debugging method, it greatly shortens the production cycle. The precise control and rapid data processing of each link greatly improve the production efficiency of the camera module, reduce the production cost, and enhance the competitiveness of the product in the market.

[0018] 3. This invention adopts standardized algorithms and processes, enabling unified testing and adjustment of each camera module during the production process, ensuring consistent product quality. Whether it is different batches of products in mass production or individual camera modules in the same batch, they can all achieve similar high-performance standards, improving product reliability and stability.

[0019] 4. The automatic alignment method of the present invention is not only applicable to the current multi-lens camera module architecture, but can also be flexibly adjusted and expanded according to different camera module designs and performance requirements. Through optimization of algorithm parameters and assembly processes, it can be applied to the production of camera modules of various specifications and types, and has broad application prospects. Attached Figure Description

[0020] The present invention will be further described below with reference to the accompanying drawings and embodiments;

[0021] Figure 1 This is a schematic diagram of the assembly structure of a multi-group periscope camera module according to a preferred embodiment of the present invention;

[0022] Figure 2 This is a chart of image resolution testing according to a preferred embodiment of the present invention;

[0023] Figure 3 This is a schematic diagram of the calculation region of the spatial frequency response function algorithm according to a preferred embodiment of the present invention;

[0024] Figure 4 This is a diagram showing the collection of degree-of-freedom sensitivity data in a preferred embodiment of the present invention;

[0025] Figure 5 This is a schematic diagram of the search motion for the central space frequency response function in a preferred embodiment of the present invention;

[0026] Figure 6 This is a curve effect diagram of a preferred embodiment of the present invention. Detailed Implementation

[0027] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0028] This embodiment provides an automatic alignment method for a multi-group periscope camera module, which includes the following steps.

[0029] 1. Assembly Process Implementation: In actual production, the second group of lenses (G2) is first accurately installed inside the voice coil motor (VCM) housing to ensure normal autofocus movement. Then, using structural assembly equipment, a line scan camera is activated to adjust the tilt angle of the second and third group of lenses (G3), monitoring in real time and controlling the tilt angle within 0.2°. Simultaneously, the distance reference value between the third and second group of lenses is determined based on the telephoto motor current value, ensuring that the distance meets design requirements. Next, a vision camera is used to align the physical centers of the second and third group of lenses. Image processing algorithms are used to precisely control the eccentricity to not exceed 50µm. After assembling the second and third group of lenses, for the first group of lenses (G1) and the image sensor, image algorithms are used to adjust the displacement and tilt angle of the first group of lenses in conjunction with the image sensor according to a pre-set program and algorithm logic, achieving precise assembly of the two.

[0030] 2. Image Resolution Test and Index Calculation: Align the assembled camera module with the test chart and activate the autofocus motor to drive the second group of lenses to scan the defocus curve. During the curve scanning process, according to the requirements of the spatial frequency response function (SRF) algorithm, image data is acquired in the horizontal and vertical directions for five regions with a 0.8 field of view rhombus added to the central region. The spatial frequency response function value of each region is calculated, resulting in a total of 10 data points. Based on these data, the peak motor current value of each region (such as CT_H_Peak motor current value, CT_V_Peak motor current value, etc.) is calculated. The horizontal and vertical separation values, left and right astigmatism, vertical astigmatism, left and right linear astigmatism, and vertical linear astigmatism of the four regions of the F08 field of view are calculated according to the definition. The calculated indicators are compared with the preset AA target card controlled astigmatism and linear astigmatism specifications (5µm) to evaluate whether the performance of the camera module meets the standards.

[0031] 3. Degrees of Freedom Sensitivity Collection and Equation Solving: Five material samples were selected, and a precision oscillation device was used to perform oscillation operations on the first group of lenses (rotation around the X-axis and Y-axis, with angles within ±0.4 degrees and oscillation steps of 0.1 degrees of freedom) and the image sensor (rotation around the X-axis and Y-axis). After each oscillation, corresponding image data was collected, astigmatism and linear astigmatism values ​​were calculated, and the data were recorded and their correlation was analyzed. Based on the correlation analysis results, the coefficients A1-D4 in the quaternary linear polynomial equation (A1x1+B1x2+C1x3+D1x4=y1, etc.) were determined (0 if there is no correlation). By solving this equation, the values ​​of the first group of lenses' rotation around the X-axis, the first group of lenses' rotation around the Y-axis, the image sensor's rotation around the X-axis, and the image sensor's rotation around the Y-axis, which meet the astigmatism and linear astigmatism position requirements, were obtained, providing a theoretical basis for further adjustments to the camera module.

[0032] 4. Implementation of Optimal Search for Center Spatial Frequency Response Function: When the autofocus (second group of lenses) motor stops at the center Peak position, the automatic control device is activated. Following the set parameters (±0.15mm, step size 0.025mm), the first group of lenses is moved along the Y-axis. After each movement, 12 images are captured, and the center spatial frequency response function value is calculated for each image using image analysis software. These spatial frequency response function values ​​are then curve-fitted to find the position of the Y-axis translation motor corresponding to the curve peak. The first group of lenses is then translated and swung along the Y-axis to that position. Next, the first group of lenses is moved along the X-axis in the same manner, and images are captured, spatial frequency response function values ​​are calculated, and curve fitting is performed to determine the position of the X-axis translation motor corresponding to the maximum spatial frequency response function value. The first group of lenses is then translated and swung along the X-axis to that position, completing the optimal search for the center spatial frequency response function.

[0033] 5. Automated Alignment Algorithm Execution: Throughout the entire camera module production process, the automated alignment algorithm is strictly followed. From initial component preparation and preliminary assembly, to image resolution testing, degree-of-freedom sensitivity collection and analysis, optimal search for the center spatial frequency response function, and precise adjustment of components based on calculation results, each step works closely together to form an automated and efficient production process. After each step is completed, the performance of the camera module is tested and evaluated. If it does not meet the preset standards, it returns to the corresponding step for readjustment until all performance indicators of the camera module meet the requirements.

[0034] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. An automatic alignment method for a multi-group periscope camera module, characterized in that, Includes the following steps: S1. Assemble the second and third groups of lenses in the multi-lens camera module. Assemble the second group of lenses in the voice coil motor housing so that it can move for automatic focusing. Use the structural assembly equipment and line scan camera to adjust the tilt angle between the second and third groups of lenses to no more than 0.2°. Determine the distance between the second and third groups of lenses based on the current value of the telephoto motor. Use a vision camera to align the physical centers of the second and third groups of lenses, with an eccentricity of no more than 50µm. S2. The spatial frequency response function algorithm is used to calculate the image resolution. The calculation area is the central area plus 5 regions of 0.8 field of view rhombus. The spatial frequency response function values ​​are obtained in the horizontal and vertical directions. The autofocus motor drives the second group of lenses to scan the defocus curve. Based on the curve, multiple test indicators are defined, including the peak motor current value of each region, the horizontal and vertical separation value of the field of view region, astigmatism and linear astigmatism. S3. Collect the degree-of-freedom and sensitivity data of the first group of lenses and the image sensor, oscillate the degree-of-freedom of the first group of lenses around the X-axis and the Y-axis, and the degree-of-freedom of the image sensor around the X-axis and the Y-axis, analyze their correlation with astigmatism and linear astigmatism, and establish a quaternary linear polynomial equation to solve for the position of pixel linear astigmatism and astigmatism. S4. When the second group of lens motors stops at the center Peak position, move the first group of lenses by translating along the X-axis and along the Y-axis, take images and calculate the center spatial frequency response function value. Determine the position of the translation motors along the X-axis and along the Y-axis corresponding to the maximum spatial frequency response function value through curve fitting, and swing the first group of lenses to that position.

2. The automatic alignment method for a multi-group periscope camera module according to claim 1, characterized in that, The method for determining the calculation area of ​​the spatial frequency response function algorithm and the definition of each test index are as follows: The calculation area is selected from five regions, including the central region plus a 0.8 field of view rhombus. Five points are selected in the horizontal and five in the vertical directions to calculate the spatial frequency response function value, for a total of 10 points. The peak motor current value of each curve is defined as the CT_H_Peak motor current value and CT_V_Peak motor current value of the central region, and the F08_UL_H_Peak and F08_UL_V_Peak of each corner region of the F08 field of view. The horizontal and vertical separation value, left and right astigmatism, up and down astigmatism, left and right linear astigmatism, and up and down linear astigmatism of the field of view are calculated through these peak motor current values.

3. The automatic alignment method for a multi-group periscope camera module according to claim 2, characterized in that, The four-variable linear polynomial equations are established as A1x1+B1x2+C1x3+D1x4=y1, A2x1+B2x2+C2x3+D2x4=y2, A3x1+B3x2+C3x3+D3x4=y3, and A4x1+B4x2+C4x3+D4x4=y4, where x1 = the degree of freedom of rotation of the first group of lenses around the X-axis, x2 = the degree of freedom of rotation of the first group of lenses around the Y-axis, x3 = the degree of freedom of rotation of the image sensor around the X-axis, and x4 = the degree of freedom of rotation of the image sensor around the Y-axis. A1-D4 are coefficients determined based on the correlation between the degrees of freedom of the first group of lenses and the image sensor and astigmatism and linear astigmatism. If there is no correlation, the coefficients are 0.

4. The automatic alignment method for a multi-group periscope camera module according to claim 3, characterized in that, y1 represents horizontal line dispersion, y2 represents vertical line dispersion, y3 represents horizontal image dispersion, and y4 represents vertical image dispersion.

5. The automatic alignment method for a multi-group periscope camera module according to claim 1, characterized in that, The parameters for the X-axis and Y-axis translation of the first group of lenses are ±0.15mm, with a step size of 0.025mm. Twelve images are captured for each movement to calculate the central spatial frequency response function value.

6. A multi-group periscope camera module, characterized in that, The assembly and optimization are carried out using the automatic alignment method for a multi-group periscope camera module as described in any one of claims 1-5.

Images