CN107702695A - Camera module group lens and the method for testing of imaging sensor relative position - Google Patents

Abstract

A method for testing the relative position of a camera module lens and an image sensor, 1) in a whiteboard test environment, setting the camera module sample lens parallel to the whiteboard with a clear focus distance; 2) adjusting the image sensor within a preset angle range And take images to obtain multiple images corresponding to different relative inclinations; 3) select two brightness values and use the binary method to calculate the difference between the brightness centers of each image at the two brightness values, and obtain multiple sets of relative inclinations and brightness centers Correspondence between the differences; 4) under the whiteboard test environment, the camera module to be tested takes images with the same clear focus distance as step 1, and the difference between the brightness centers when the two thresholds are calculated by the method of step 3 value, according to the data in the corresponding relationship, the relative inclination angle between the lens of the camera module to be tested and the image sensor can be obtained, and the relative offset can be further obtained. The method can be directly completed at a whiteboard test station, thereby improving test efficiency and saving test cost.

Description

Test method for the relative position of camera module lens and image sensor

technical field

The invention relates to a camera module, in particular to a method for testing the relative positions of a camera lens and an image sensor.

Background technique

A camera module refers to an optical module that at least includes a lens and an image sensor and can perform a camera function. The lens and the image sensor have a relative positional relationship, including a relative tilt angle and a relative offset. Wherein, the relative tilt angle refers to the included angle between the plane where the lens of the camera module is located and the plane where the image sensor is located. The relative offset refers to the offset between the center position of the lens of the camera module and the center position of the image sensor. Camera modules are now widely used in mobile phones, VR and other devices. These devices have certain requirements for the relative tilt angle and relative offset of the module lens and image sensor, which need to be tested during the production process. Current testing methods require a separate workstation to complete the test using specific charts. The testing method is cumbersome and the testing efficiency is low.

Contents of the invention

The invention provides a method for testing the relative inclination and relative offset of the camera module lens and the image sensor in a whiteboard environment. Compared with the current testing method, the method does not need to replace the workstation, and can be completed directly at the whiteboard testing workstation. Improve test efficiency and save test cost.

A method for testing the relative position of a camera module lens and an image sensor, including a method for testing the relative inclination of the camera module lens and the image sensor, comprising: 1) selecting a camera module sample from the same batch of camera modules to be tested, and The camera module sample is placed in the whiteboard test environment, so that the lens of the camera module sample is set parallel to the whiteboard with a clear focus distance, 2) adjust the image sensor of the camera module sample with a preset amount of change, so that the camera module sample The relative inclination angle of the image sensor of the group sample and the lens of the camera module sample is within the preset angle range, and an image is taken after each adjustment to obtain multiple images corresponding to different relative inclination angles; 3) select two The luminance value is used as the two first thresholds, and the difference between the luminance centers of each image at the two first thresholds is calculated by using the binary method, so as to obtain the corresponding relationship groups between multiple sets of relative inclination angles and the difference between the luminance centers; 4 ) Under the whiteboard test environment, one or more camera modules to be tested in the same batch as the camera module samples take images with the same clear focus distance as step 1, and calculate the two first by the method of step 3 The difference value of the brightness center at the threshold value, according to the data in the correspondence group, the relative inclination angle between the lens of the camera module to be tested and the image sensor of the camera module to be tested can be obtained.

Preferably, it also includes a method for testing the relative offset between the camera module lens and the image sensor, including: 5) for the image taken in step 4, select a second threshold and calculate the coordinates of the brightness center of the image according to the second threshold, And in combination with the coordinates of the center of the image sensor of the camera module to be tested, the first distance between the image brightness center and the center of the image sensor of the camera module to be tested is obtained. The focal length of the image sensor, and the relative inclination angle of the lens of the camera module to be tested and the image sensor of the camera module to be tested obtain the projection of the image brightness center and the lens center of the camera module to be tested on the image sensor of the camera module to be tested The second distance between the points, the difference between the first distance and the second distance is the relative offset between the lens of the camera module to be tested and the image sensor of the camera module to be tested.

Preferably, in the plane of the image sensor, the coordinate axes passing through the center of the image sensor and perpendicular to each other are taken as the x-axis and the y-axis. In the above step 3, the brightness of each image at the two first thresholds is calculated using the binary method The difference of the center in the x-axis direction, thereby obtaining the corresponding relationship group between the relative inclination angles in the y-axis direction and the brightness center difference in the x-axis direction; in the above-mentioned step 4, the method for calculating the two The difference of the brightness center in the x-axis direction at the threshold value, according to the data in the corresponding group, the relative inclination angle in the y-axis direction between the lens of the camera module to be tested and the image sensor of the camera module to be tested can be obtained.

Preferably, it also includes a test method for the relative offset between the camera module lens and the image sensor in the x-axis direction, including: 5) for the image taken in step 4, select a second threshold and calculate the value of the image according to the second threshold The coordinates of the brightness center on the x-axis, combined with the coordinates of the image sensor center of the camera module to be tested on the x-axis, obtain the first position on the x-axis between the image brightness center and the image sensor center of the camera module to be tested. Distance, according to the focal length of the lens center of the camera module to be tested to the image sensor of the camera module to be tested, and the relative inclination angle of the lens of the camera module to be tested and the image sensor of the camera module to be tested in the y-axis direction to obtain the image brightness center The second distance on the x-axis between the lens center of the camera module to be tested and the projection point on the image sensor of the camera module to be tested, the difference between the first distance and the second distance is the camera module to be tested The relative offset between the center of the lens and the center of the image sensor of the camera module to be tested in the x-axis direction.

Preferably, in the above step 3, the step of using the binary method to calculate the difference between the brightness centers of each image in the x-axis direction at the two first thresholds includes: using the binary method to respectively calculate the brightness value greater than two The pixels of the first threshold are set to 255, the pixels whose brightness values are less than two first thresholds are set to 0, and the abscissas of the pixels whose brightness values are 255 are added and averaged to obtain each image respectively The coordinates of the brightness center on the x-axis at the two first thresholds, and subtracting the obtained two coordinates is the difference of the brightness center in the x-axis direction.

Preferably, a six-axis adjuster is used to adjust the image sensor of the sample camera module to change the inclination angle between the image sensor of the sample camera module and the lens of the sample camera module.

Preferably, the angle between the lens of the sample camera module and the image sensor of the sample camera module is adjusted with a preset variation between -5° and 5°.

Preferably, the preset amount of variation is no more than 0.2° each time.

Preferably, in step 5, 90-95% of the maximum brightness value of the image is selected as the second threshold, and the coordinates of the brightness center of the image are calculated.

Preferably, the second distance is the product of the tangent of the relative inclination and the focal length.

Description of drawings

The above features and technical advantages of the present invention will become clearer and easier to understand by describing its embodiments in conjunction with the following drawings.

Fig. 1 is a schematic diagram one showing an embodiment of the present invention;

Fig. 2 is the basic principle drawing two that represent the embodiment of the present invention;

Fig. 3 is a schematic diagram three showing the embodiment of the present invention;

Fig. 4 is the basic schematic diagram four of the embodiment of the present invention;

5 is a diagram showing the positional relationship between the lens of the camera module sample and the image sensor of the camera module sample according to the embodiment of the present invention;

Fig. 6 is a positional diagram 1 showing the lens of the camera module to be tested and the image sensor of the camera module to be tested according to an embodiment of the present invention;

7 is a diagram 2 showing the positional relationship between the lens of the camera module to be tested and the image sensor of the camera module to be tested according to the embodiment of the present invention.

detailed description

Embodiments of the method for testing the relative positions of the camera module lens and the image sensor according to the present invention will be described below with reference to the accompanying drawings. Those skilled in the art would recognize that the described embodiments can be modified in various ways or combinations thereof without departing from the spirit and scope of the invention. Accordingly, the drawings and description are illustrative in nature and not intended to limit the scope of the claims. Also, in this specification, the drawings are not drawn to scale, and like reference numerals denote like parts.

First, briefly explain the basic principle of the present invention. Take an image under the whiteboard test environment, calculate the brightness value of each pixel in the image, and connect the pixels with equal brightness. As shown in Figure 1 and Figure 2, when the plane where lens A is located is parallel to the plane where image sensor B is located, the isoluminance lines are a set of concentric circles (isoluminance lines refer to curves with equal brightness values on an image). A set of thresholds is selected, and the image is binarized to calculate the brightness center of the image. The binarization process of the image is to set the gray value of the pixels on the image to 0 or 255, that is, to present the entire image with an obvious visual effect of only black and white. The threshold value is selected between 0 and 255. The brightness center positions corresponding to each threshold should be the same point, that is, the common center of each isoluminance line.

When the plane where the image sensor B in the camera module is located is not parallel to the plane where the lens A is located, it means that the image sensor B has rotated a certain angle from a parallel state around the rotation axis, and the rotation axes are coordinate axes perpendicular to each other in the image sensor B plane. For example, if the image sensor is a rectangle, pass through the center of the image sensor B, take the long side direction of the image sensor B as the x-axis, and take the short side direction of the image sensor as the y-axis. Rotate the image sensor in Figure 1 around the x-axis or y-axis by a certain angle, and the plane where the lens A is located is no longer parallel to the plane where the image sensor B is located. As shown in FIG. 3 and FIG. 4 , the image sensor B is rotated around the y-axis, and the arrangement of the isoluminance lines formed is no longer concentric circles. Also select a set of thresholds, binarize the image, and calculate the brightness center of the image. The brightness center position corresponding to each threshold is no longer the same point, but a different point on the x-axis, as shown in Figure 4. P100, P150, and P200 are the brightness centers obtained when the thresholds are 100, 150, and 200, respectively. The larger the relative inclination angle between the lens A and the image sensor B, the larger the deviation between the center points.

The present invention calculates the relative positions of the lens and the image sensor, that is, the relative inclination angle and the relative offset, by using the differences in brightness center positions corresponding to different thresholds. The present embodiment will be described below in conjunction with FIGS. 5 to 7 . In this embodiment, the calculation method of the relative inclination angle Tilt _y in the y-axis direction and the relative offset Shift _x in the x-axis direction is taken as an example for illustration, and the relative inclination angle Tilt _x in the x-axis direction and the relative offset in the y-axis direction can also be calculated in the same way. Relative offset Shift _y . The relative tilt angle Tilt _y in the y-axis direction is the angle between the two planes caused by the rotation of the image sensor around the y-axis causing the plane where the lens is located to be non-parallel to the plane where the image sensor is located. The angle between the two planes is equivalent to the method of two planes The included angle of the line, as indicated by Tilt _y in Figure 3. The test method is specifically described below.

1) Select the camera module sample, place the camera module sample in the whiteboard test environment, make the plane where the lens A1 of the camera module sample is located parallel to the plane where the whiteboard C is located, and the distance between the lens A1 of the camera module sample and the whiteboard C is Its clear focusing distance refers to the focusing distance at which clear images can be captured. The camera module sample is selected from the same batch of camera modules to be tested, and the lens A1 of the camera module sample has the same focal length as the lens A2 of the camera module to be tested. The camera module sample mentioned above refers to the unpackaged one, and the image sensor B1 of the camera module sample can be rotated and adjusted. And the camera module to be tested hereinafter has been packaged and processed. The positional relationship between the image sensor B2 of the camera module to be tested and the lens A2 of the camera module to be tested has been fixed and cannot be adjusted. The present invention will test the relationship between them. Whether the positional relationship of is up to standard.

2) Adjust the image sensor B1 with a preset amount of change, that is, rotate the image sensor B1 around the y-axis, so that the relative tilt angle Tilt _y1 between the image sensor B1 and the lens A1 of the camera module sample is within the preset angle range, and in One image is taken after each adjustment, and multiple images corresponding to different inclination angles are obtained. In this embodiment, 50 images are taken.

3) Each image is processed by a binary method, and the difference in the x-axis direction between the brightness centers corresponding to the two first thresholds is calculated. In this embodiment, 100 and 200 are selected, and the difference between the brightness center of each image in the x-axis direction at the two first thresholds is calculated respectively, so as to obtain the difference between multiple sets of relative inclination Tilt _y1 and the brightness center difference in the x-axis direction Correspondence. First calculate the brightness center of the image at the threshold of 100: set the brightness of pixels with a brightness value greater than 100 to 255, and set the brightness of pixels with a brightness value less than 100 to 0, and calculate the corresponding brightness center of the image at the threshold of 100 on the x-axis The coordinates of P _{100_X} . Use the same method to obtain the coordinate P _{200_X} of the brightness center corresponding to the image at the threshold of 200 on the x-axis. P _{100_X} -P _{200_X} is the difference in the x-axis direction between the brightness centers corresponding to the thresholds 100 and 200 of the image. After calculation, 50 groups of corresponding relations between the relative inclination Tilt _y1 and the brightness center difference in the x-axis direction can be obtained, and the data of this group are stored in the database, so that the data can be recalled at any time.

4) Carry out batch testing. In the whiteboard test environment, place the camera module to be tested at the same focusing distance as in step 1 to take images, that is, the distance from the lens A2 of the camera module to be tested to the whiteboard is the same as the distance from the camera module sample. The distance from lens A1 to the whiteboard is the same. Also calculate the difference between the brightness centers of the two first thresholds 100 and 200 in the x-axis direction, and according to the correspondence between multiple sets of relative inclination angles Tilt _y1 and the difference between the brightness centers in the x-axis direction, the camera model to be tested can be obtained. The lens A2 of the group and the image sensor B2 of the camera module to be tested are relatively tilted by an angle Tilt _y2 . and so on.

In an optional embodiment, according to the relative inclination angle between the camera lens A2 of the camera module to be tested and the image sensor B2 of the camera module to be tested, the center of the camera lens A2 of the camera module to be tested and the camera module to be tested can also be calculated. The relative offset of the center of the image sensor B2 in the x-axis direction, including: the steps

5) For the image taken in step 4, select the second threshold to calculate the coordinate O _1X of the brightness center O ₁ of the image on the x-axis, and combine the coordinate O _2X of the center O ₂ of the image sensor B2 on the x-axis to obtain an image A first distance O _1X O _2X between the center of brightness and the center of the image sensor B2.

According to the distance between the center O ₄ of the lens A2 of the camera module to be tested and the image sensor B2 as the focal length f, and the inclination Tilt _y2 , the image brightness center O ₁ and the center O ₄ of the lens A2 of the camera module to be tested are in the image sensor B2 The second distance O _1X O _3X between the projected points O ₃ on

O _1X O _3X ＝f*tan(Tilt _y2 )

The difference between the two distances is the relative offset Shift _x between the lens A2 of the camera module to be tested and the image sensor B2 in the x-axis direction. The calculation formula is:

Shift _x =O _2X O _3X =O _1X O _2X -O _1X O _3X .

Wherein, Shift _x may be a positive value or a negative value, as shown in Figure 7, the center _O2 of the image sensor B2 is located at the image brightness center O1 and the center _{O4 of} the lens A2 of the camera module to be tested is in the image sensor When between the projection point O and ₃ on B2, Shift _x is a negative value.

In an optional embodiment, a six-axis adjuster can be used to adjust the inclination angle of the image sensor B1 of the sample camera module.

In an optional embodiment, the angle between the lens A1 and the image sensor B1 of the sample camera module is gradually adjusted within an angle range of -5° to 5° with a preset amount of variation.

In an optional embodiment, the preset amount of change is no more than 0.2° for each change. The smaller the variation, the more precise its calculation accuracy.

In an optional embodiment, in step 5, the preset threshold is selected as 90-95% of the maximum brightness value of the image as the threshold, and the x-axis coordinate O _1X of the brightness center position O ₁ of the image is calculated.

In an optional embodiment, in step 3, the abscissas of all pixels with a brightness value of 255 are added, and their average value is calculated, so as to obtain the corresponding brightness center of the image at the selected threshold value on the x-axis coordinate value. Corresponding to the threshold 100 and the threshold 200, the coordinate P 100_X of the brightness center on the x-axis corresponding to the image at the threshold 100 is obtained, and the coordinate P _{200_X} of the brightness center on the x-axis corresponding to the image at the threshold 200 can be obtained by the same _method .

The present invention selects samples from the same batch of camera modules, obtains multiple photographed images of the samples in a whiteboard test environment, and uses a binary method to process the multiple photographed images, using brightness center differences corresponding to different thresholds to obtain The relative inclination angle of the lens of the sample and the image sensor of the sample is obtained, and the corresponding relationship group between the relative inclination angle and the brightness center difference can be obtained, so that the relative inclination of the lens of the camera module to be tested and the image sensor of the camera module to be tested can be obtained angle, and further get its relative offset. Compared with the traditional test method, this method does not need to replace the station, and can be completed directly on the whiteboard test station, which improves the test efficiency and saves the test cost.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. a method for testing the relative position of camera module lens and image sensor, is characterized in that, comprises the test method of camera module lens and image sensor relative inclination angle, comprises: 1) Select a camera module sample from the same batch of camera modules to be tested, place the camera module sample in a whiteboard test environment, and set the lens of the camera module sample parallel to the whiteboard with a clear focus distance, 2) Adjust the image sensor of the camera module sample with a preset amount of change, so that the relative inclination angle between the image sensor of the camera module sample and the lens of the camera module sample is within the preset angle range, and each adjustment After taking an image, multiple images corresponding to different relative inclination angles are obtained; 3) Select two luminance values as the two first thresholds, and use the binary method to calculate the difference between the luminance centers of each image at the two first thresholds, so as to obtain the difference between multiple groups of relative inclination angles and the difference between the luminance centers Correspondence group; 4) Under the whiteboard test environment, one or more camera modules to be tested in the same batch as the camera module samples take images with the same clear focus distance as in step 1, and calculate the two first The difference between the brightness centers at a threshold value, according to the data in the correspondence group, the relative inclination angle between the lens of the camera module to be tested and the image sensor of the camera module to be tested can be obtained. 2. the method for testing the camera module lens and the relative position of the image sensor according to claim 1, further comprising a method for testing the relative offset between the camera module lens and the image sensor, including: 5) For the image taken in step 4, select the second threshold and calculate the coordinates of the brightness center of the image according to the second threshold, and combine the coordinates of the image sensor center of the camera module to be tested to obtain the image brightness center and the camera to be tested. the first distance between the image sensor centers of the module, According to the focal length of the lens of the camera module to be tested to the image sensor of the camera module to be tested, and the relative inclination angle of the lens of the camera module to be tested and the image sensor of the camera module to be tested, the image brightness center and the camera module to be tested are obtained The second distance between the projection points of the lens center on the image sensor of the camera module to be tested, The difference between the first distance and the second distance is the relative offset between the lens of the camera module to be tested and the image sensor of the camera module to be tested. 3. the method for testing the camera module lens and the relative position of the image sensor according to claim 1, characterized in that, In the plane of the image sensor, the coordinate axes passing through the center of the image sensor and perpendicular to each other are the x-axis and the y-axis, In the above step 3, the binary method is used to calculate the difference of the brightness center in the x-axis direction of each image at the two first thresholds, so as to obtain multiple groups of relative inclination angles in the y-axis direction and the difference of the brightness center in the x-axis direction Correspondence groups between; In the above step 4, the difference between the brightness center in the x-axis direction when the two thresholds are calculated by the method of step 3, according to the data in the corresponding relationship group, the lens of the camera module to be tested and the lens to be tested can be obtained. The relative tilt angle of the image sensor of the camera module in the y-axis direction. 4. the method for testing the relative position of camera module lens and image sensor according to claim 3, is characterized in that, also comprises the test method of the relative displacement of camera module lens and image sensor x-axis direction, comprises: 5) For the image taken in step 4, select the second threshold and calculate the coordinates of the brightness center of the image on the x-axis according to the second threshold, and combine the coordinates of the image sensor center of the camera module to be tested on the x-axis, Obtain the first distance on the x-axis between the image brightness center and the image sensor center of the camera module to be tested, According to the focal length from the lens center of the camera module to be tested to the image sensor of the camera module to be tested, and the relative inclination angle of the lens of the camera module to be tested and the image sensor of the camera module to be tested in the y-axis direction, the image brightness center and the image sensor to be tested are obtained. The second distance on the x-axis between the lens center of the test camera module and the projection point on the image sensor of the camera module to be tested, The difference between the first distance and the second distance is the relative offset in the x-axis direction between the lens center of the camera module to be tested and the image sensor center of the camera module to be tested. 5. The method for testing the relative position of the camera module lens and the image sensor according to claim 3, characterized in that, in the above-mentioned step 3, the brightness center of each image is calculated at the two first thresholds using the binary method The step of determining the difference in the x-axis direction includes: using a binary method to respectively set pixels whose brightness values are greater than the two first thresholds to 255, set pixels whose brightness values are smaller than the two first thresholds to 0, and set Add the abscissas of the pixels whose brightness value is 255 and calculate the average value, so as to obtain the coordinates of the brightness center of each image on the x-axis at the two first thresholds, and subtract the two obtained coordinates to obtain the brightness The difference between the centers in the x-axis direction. 6. the method for testing the relative position of camera module lens and image sensor according to claim 1, is characterized in that, The image sensor of the sample camera module is adjusted by using a six-axis adjuster, and the inclination angle between the image sensor of the sample camera module and the lens of the sample camera module is changed. 7. The method for testing the relative position of the camera module lens and the image sensor according to claim 1, wherein the camera lens and camera lens of the camera module sample are adjusted between -5° and 5° with a preset amount of change. The angle between the image sensors of the module samples. 8 . The method for testing the relative position of the camera module lens and the image sensor according to claim 7 , wherein the preset amount of change is no more than 0.2° each time. 9. The method for testing the relative position of the camera module lens and the image sensor according to claim 2, wherein in step 5, 90% to 95% of the maximum brightness value of the image is selected as the second threshold, and the value of the image is calculated. Brightness center coordinates. 10 . The method for testing the relative position of the camera module lens and the image sensor according to claim 2 , wherein the second distance is the product of the tangent of the relative inclination and the focal length. 11 .