Spot inspection method for test distance of fixed-focus camera module
By setting mark points on the test image card of the fixed focus camera module, capturing images and comparing the mark point spacing, the problem of test distance detection error of fixed focus camera module in the prior art is solved, and more accurate test distance judgment is achieved.
Patent Information
- Application Number
- CN202510137611.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-07
- Publication Date
- 2025-04-25
AI Technical Summary
The prior art has errors in the test distance detection of fixed-focus camera modules, especially because the module is placed in the test frame, resulting in the presence of errors when using a ruler or laser rangefinder.
By setting multiple marking points on the test diagram card of the fixed focus camera module, the image is captured at the specified test distance and the fixed camera field of view angle, the distance between any two marking points is obtained, and the setting value is compared to the test value to determine whether the test distance meets the standard.
It effectively reduces test errors, and uses the camera module to form pixel spacing of mark points in the image to accurately determine whether the test distance is within the range, improving the accuracy of the test.
Smart Images
Figure CN119880364A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the technical field of camera module detection, and in particular to a spot inspection method for a test distance of a fixed-focus camera module. Background Art
[0002] When the camera module is produced, it is necessary to check the test distance of the Chart (camera module test calibration chart). The test distance inspection refers to a test performed after the camera module is assembled to ensure that the camera can obtain a clear image within the predetermined optimal shooting distance. Especially for fixed-focus camera modules, the test distance is crucial and affects the Peak point position of the module. The test distance of the fixed-focus camera module refers to the distance between the lens and the test calibration chart after adjusting the focus AA (automatic alignment and focus). This distance should be set to the predetermined optimal shooting distance required by the customer.
[0003] The conventional distance inspection solution is to use a ruler of a specific length or a laser rangefinder for testing. In fact, because the module is placed in the test frame (there is a certain clearance height), there will be a certain error when using a ruler and a rangefinder. Summary of the invention
[0004] In order to at least solve the above-mentioned technical problems, the purpose of the present application is to provide a method for inspecting the test distance of a fixed-focus camera module, by judging whether the test distance meets the standard through the pixel spacing of the marker points in the module imaging picture, thereby effectively reducing the test error.
[0005] In order to achieve the above-mentioned purpose, the present application provides a method for inspecting the test distance of a fixed-focus camera module, including:
[0006] Set multiple marking points on the test chart of the fixed-focus camera module;
[0007] At a specified test distance and a fixed camera field of view, capturing an image of the test chart, and obtaining the distance between any two marking points from the image;
[0008] The distance between the two marking points is compared with the set value, and according to the proportional relationship between the real object and the image, it is determined whether the currently specified test distance meets the standard.
[0009] Furthermore, at least two marking points are set on the test chart of the fixed-focus camera module.
[0010] Furthermore, the two marking points are black circular marking points, and the distance between the centers of the two circular marking points is obtained by identifying the centers of the circular marking points.
[0011] Furthermore, at a specified test distance, under the premise that the camera field of view is fixed, the drawing content captured by the camera is of a fixed size, and the positions and relative distances of the two marking points in the image are fixed.
[0012] Furthermore, the step of capturing the image of the test chart at a specified test distance and a fixed camera field of view, and obtaining the distance between any two marking points from the image, further includes:
[0013] The distance between two landmarks in the image is obtained according to the following formula:
[0014] d=D / W×w or d=D / H×h
[0015] Among them, d is the theoretical distance between the two marking points in the image; D is the distance between the center positions of the two marking points on the drawing; W×H is the image size captured by the camera module; w×h is the pixel of the camera module.
[0016] Furthermore, the method further includes: monitoring the distance d' between the two marking points, and confirming whether the test distance meets the standard according to the distance.
[0017] Furthermore, it also includes: comparing and calculating the distance d' between the two marking points with a set value or a theoretical value d. If the distance is smaller than the set value or the theoretical value, it indicates that the current actual test distance is far; if the distance is larger than the set value or the theoretical value, it indicates that the current actual test distance is close.
[0018] Furthermore, the method further includes: obtaining the actual test distance of the current drawing according to the following formula, and determining the distance by which the drawing needs to be moved farther or closer:
[0019] d' / d=actual test distance / target test distance
[0020] Where d' is the actual test distance between two marker points in the image; d is the theoretical distance between two marker points in the image.
[0021] Furthermore, it also includes: a linkage automation device, and the automation device is used to realize automatic movement calibration of the drawing.
[0022] Furthermore, the method also includes: simultaneously checking the clarity of the center of the camera module.
[0023] The method for inspecting the test distance of the fixed-focus camera module of the embodiment of the present application includes: setting a plurality of marking points on the test chart of the fixed-focus camera module; capturing the image of the test chart at a specified test distance and a fixed camera field of view, and obtaining the distance between any two marking points from the image; comparing the distance between the two marking points with a set value, and judging whether the currently specified test distance meets the standard according to the proportional relationship between the real object and the image. Confirm whether the test distance is within the range by the pixel spacing of the marking points in the imaging screen of the camera module. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] The accompanying drawings are used to provide a further understanding of the present application and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the present application and do not constitute a limitation of the present application. In the accompanying drawings:
[0025] Figure 1 It is a schematic diagram of a method for spot checking the test distance of a fixed-focus camera module according to an embodiment of the present application;
[0026] Figure 2 It is a schematic diagram of two marking points of an embodiment of the present application. DETAILED DESCRIPTION
[0027] The embodiments of the present application will be described in more detail below with reference to the accompanying drawings. Although certain embodiments of the present application are shown in the accompanying drawings, it should be understood that the present application can be implemented in various forms and should not be construed as being limited to the embodiments described herein. Instead, these embodiments are provided to provide a more thorough and complete understanding of the present application. It should be understood that the drawings and embodiments of the present application are only for exemplary purposes and are not intended to limit the scope of protection of the present application.
[0028] It should be understood that the various steps described in the method implementation of the present application can be performed in different orders and / or performed in parallel. In addition, the method implementation may include additional steps and / or omit the steps shown. The scope of the present application is not limited in this respect.
[0029] The term "including" and its variations used herein are open inclusions, i.e., "including but not limited to". The term "based on" means "based at least in part on". The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments". The relevant definitions of other terms will be given in the following description.
[0030] It should be noted that the modifications of "one" and "plurality" mentioned in this application are illustrative rather than restrictive, and those skilled in the art should understand that unless otherwise clearly indicated in the context, it should be understood as "one or more". "Plurality" should be understood as two or more.
[0031] Hereinafter, embodiments of the present application will be described in detail with reference to the accompanying drawings.
[0032] An embodiment of the present application provides a method for inspecting the test distance of a fixed-focus camera module, comprising: setting a plurality of marking points on a test chart of the fixed-focus camera module; capturing an image of the test chart at a specified test distance and a fixed camera field of view, and obtaining the distance between any two marking points from the image; comparing the distance between the two marking points with a set value, and determining whether the currently specified test distance meets the requirements according to the proportional relationship between the actual object and the image.
[0033] Figure 1 This is a flow chart of a spot inspection method for the test distance of a fixed-focus camera module according to an embodiment of the present application. Figure 1 , the specific implementation methods of this application are described in detail.
[0034] First, in step 101, a plurality of marking points are set on a test chart of a fixed-focus camera module.
[0035] In the embodiments of the present application, at least two mark points need to be added to the test chart of the fixed-focus camera module (full name: Camera Compact Module, abbreviated as CCM), and the specific design definition is based on the drawing (referring to the design drawing based on the SFR test requirements of the module (the position and size of the captured ROI), and the number, position, and spacing of the mark points are planned and defined to avoid interference between the two and affect the SFR test results). Here, the drawing and the test chart can be the same or different. The difference is that the test chart is used for actual testing.
[0036] In some exemplary embodiments, it is recommended to use black circular marking points to facilitate identification of the center of a circle, and the distance between the centers of two circular marking points can be obtained by identifying the center of the circular marking points.
[0037] like Figure 2 As shown, the two marking points are two black dots on the left and right. At a specified test distance, under the premise that the camera's field of view is fixed, the drawing content captured by the camera is of a fixed size. For example:
[0038] For a camera module with a 78° field of view and a test distance of 400mm, the captured image size is 537×402.8mm, so the positions and relative distances of the two markers in the image are also fixed.
[0039] Correspondingly, for a camera module with a pixel of w×h and a field of view of a°, at a test distance of b mm, the captured image size is W×H mm, and the distance between the center positions of the two mark points on the drawing is D mm.
[0040] In step 102, an image of a test chart is captured at a specified test distance b and a fixed camera field of view, and a distance d' between any two marking points is obtained from the image.
[0041] In some exemplary embodiments, at a specified test distance, the camera field of view is fixed, and the size of the drawing content captured is fixed. Therefore, for a camera module with a pixel of w×h and a field of view of a°, at a test distance b, the captured image size is W×H, and the distance between the center positions of the two Mark points on the drawing is D. The theoretical distance d between the two Mark points in the image can be obtained by one of the following two formulas.
[0042] d=D / W×w
[0043] d=D / H×h
[0044] Where: d is the theoretical distance between the two mark points in the image (the center spacing of the output image), unit: mm; D is the distance between the center positions of the two mark points on the drawing (the center spacing on the drawing), unit: mm; W×H is the image size captured by the camera module, unit: mm; w×h is the pixel of the camera module.
[0045] In step 103, d' is monitored, and it is determined whether the test distance b meets the standard according to the value of d'.
[0046] In the embodiment of the present application, according to the proportional relationship between the real object and the image, the distance between the mark points of the image is used to determine whether the real object distance (i.e., the actual test distance) meets the standard. This standard is set as the predetermined optimal shooting distance required by the customer, such as the common camera test distance. The customer gives a target value of 40cm and an interval of 40±0.5cm. The d' value is used to confirm whether the test distance b is within the test interval, thereby making a judgment.
[0047] In some exemplary embodiments, d' is compared with a set value (theoretical value) d to determine whether the current test distance is close or far. If d' is less than the set value or theoretical value d, it means that the current actual test distance is far; if d' is greater than the set value or theoretical value d, it means that the current actual test distance is close.
[0048] In some exemplary implementations, we can also obtain the actual test distance of the current drawing according to the following formula, and the software will give a prompt to inform how many mm the drawing needs to be moved further or closer.
[0049] d' / d=actual test distance / target test distance
[0050] Where d' is the measured distance between two landmark points in the image;
[0051] d is the theoretical distance between two landmarks in the image.
[0052] In some exemplary embodiments, automated equipment may also be linked to achieve automatic movement calibration of the drawing.
[0053] In some exemplary embodiments, during the inspection process, the clarity (SFR / MTF) of the center of the camera module can also be checked simultaneously to prevent the camera module from being damaged due to repeated inspections (such as being crushed, which affects the inspection results).
[0054] MTF is the abbreviation of Modulation Transfer Function in English, and in Chinese it is Modulation Transfer Function. The function Q of how the modulation changes with the spatial frequency is called the modulation transfer function. The transfer function was originally used to illustrate the capabilities of the lens. MTF is often used in various camera lenses to describe the MTF curve of the lens to indicate the capabilities of the lens. These curves are obtained by testing under ideal test conditions while minimizing the attenuation of the resolution of the lens by other systems. But in fact, MTF can also cover the evaluation of the resolution of the entire imaging system. The closer the MTF value is to 1, the better the imaging effect of the lens.
[0055] SFR is the abbreviation of Spatial Frequency Response, which is mainly used to measure the impact of increasing spatial frequency lines on a single image. In short, SFR is another test method of MTF. This test method greatly simplifies the test process. The final calculation of SFR is to obtain the MTF curve. Although the calculation method of SFR is different from that of MTF, the results are basically the same.
[0056] In some exemplary embodiments, the core components of the camera module include lenses, image sensors, image processing chips, etc., which work together to achieve the conversion from light to electricity and image processing. The lens is responsible for capturing light and focusing it on the image sensor to form a clear image; the image sensor converts light into electrical signals; the image processing chip further processes these electrical signals, such as noise reduction, sharpening, etc., and finally outputs digital image signals.
[0057] The method for spot checking the test distance of the fixed-focus camera module provided in this application confirms whether the test distance meets the standard by the pixel spacing of the Mark point (mark point, also known as the reference point or optical positioning point) in the imaging screen of the camera module. At the same time, the validity of the spot check sample can also be determined by combining the clarity of the image (SFR / MTF).
[0058] Although the embodiments disclosed in the present invention are as above, the contents are only embodiments adopted to facilitate understanding of the present invention and are not intended to limit the present invention. Any technician in the field to which the present invention belongs can make any modifications and changes in the form and details of implementation without departing from the spirit and scope disclosed in the present invention, but the patent protection scope of the present invention shall still be subject to the scope defined in the attached claims.
Claims
1. A method for inspecting the test distance of a fixed-focus camera module, characterized in that: include: Set multiple marking points on the test chart of the fixed-focus camera module; At a specified test distance and a fixed camera field of view, capturing an image of the test chart, and obtaining the distance between any two marking points from the image; The distance between the two marking points is compared with the set value, and according to the proportional relationship between the real object and the image, it is determined whether the currently specified test distance meets the standard.
2. The method for inspecting the test distance of a fixed-focus camera module according to claim 1, characterized in that: Set at least two marking points on the test chart of the fixed-focus camera module.
3. The method for inspecting the test distance of a fixed-focus camera module according to claim 2, characterized in that: The two marking points are black circular marking points, and the distance between the centers of the two circular marking points is obtained by identifying the centers of the circular marking points.
4. The method for inspecting the test distance of a fixed-focus camera module according to claim 2, characterized in that: At a specified test distance, under the premise that the camera's field of view is fixed, the drawing content captured by the camera is of a fixed size, and the positions and relative distances of the two marking points in the image are fixed.
5. The method for inspecting the test distance of a fixed-focus camera module according to claim 1, characterized in that: The step of capturing the image of the test chart at a specified test distance and a fixed camera field of view, and obtaining the distance between any two marking points from the image, further includes: The distance between two landmark points in the image is obtained according to the following formula: d=D / W×w or d=D / H×h Among them, d is the theoretical distance between the two marking points in the image; D is the distance between the center positions of the two marking points on the drawing; W×H is the image size captured by the camera module; w×h is the pixel of the camera module.
6. The method for inspecting the test distance of a fixed-focus camera module according to claim 1, characterized in that: Also includes: The distance d' between the two marking points is monitored, and whether the test distance meets the standard is confirmed based on the distance.
7. The method for inspecting the test distance of a fixed-focus camera module according to claim 1, characterized in that: Also includes: The distance d' between the two marking points is compared and calculated with the set value or theoretical value d. If the distance is smaller than the set value or theoretical value, it means that the current actual test distance is far; if the distance is larger than the set value or theoretical value, it means that the current actual test distance is close.
8. The method for inspecting the test distance of a fixed-focus camera module according to claim 1, characterized in that: Also includes: The actual test distance of the current drawing can be obtained according to the following formula, and the distance to which the drawing needs to be moved further or closer can be determined: d' / d=actual test distance / target test distance Where d' is the distance between two landmarks in the image; d is the theoretical distance between two landmarks in the image.
9. The method for inspecting the test distance of a fixed-focus camera module according to claim 8, characterized in that: Also includes: The automated equipment is linked, and the automated equipment is used to realize automatic movement calibration of the drawings.
10. The method for inspecting the test distance of a fixed-focus camera module according to claim 1, characterized in that: Also includes: At the same time, check the clarity of the center of the camera module.