An imaging detector chip vibration displacement testing device and method

Abstract

The application relates to an imaging detector chip vibration displacement testing device and method, which comprises an LED plane light source, a homogenizing plate, an imaging lens and an image acquisition card; the LED plane light source illuminates the imaging lens after passing through the homogenizing plate, and the position of the imaging detector chip to be tested is adjusted through a gasket so as to be just located at the focal plane position of the imaging lens; the imaging lens comprises a lens barrel, a diaphragm and a double-sided convex lens which are sequentially arranged in the inner cavity of the lens barrel according to the light path; the lens barrel adopts an integrated forming process to first mill the inner cavity of the lens barrel and finally mill a small hole; the image acquisition card is connected to the imaging detector to be tested, and the image data is read by an upper computer. After the plane light source is homogenized by the homogenizing plate to form diffuse reflection, a point light source is formed through the small hole, small spot imaging is realized by using single-lens imaging, and finally the spot centroid is directly represented by the image plate to represent the chip displacement.

Description

Technical Field

[0001] This invention relates to the field of optoelectronic testing technology, and in particular to a device and method for testing the vibration displacement of an imaging detector chip. Background Technology

[0002] Imaging detectors are a type of optoelectronic device that outputs image information. They utilize the photoelectric effect to convert or enhance visible or invisible radiation images into observable, recordable, transmitted, stored, and processed images. Common types include infrared focal plane arrays, CCDs, and CMOS sensors. Imaging detectors are widely used in commercial and civilian applications, military and defense, and environmental monitoring, such as in mobile phones, digital cameras, infrared night vision devices, optoelectronic reconnaissance pods, and satellite remote sensing platforms. In these applications, the front-end optical lens group focuses the light emitted by the object onto the imaging detector chip, achieving an image of the object. Further processing by the image processing unit then acquires crucial image information.

[0003] However, in a vibrating environment, the vibration excitation, when transmitted through multiple layers to the chip, can cause the chip to wobble due to vibration amplification, thus deviating from the mounting reference. This leads to errors or even mistakes in the quantitative interpretation of the output image data. Typically, accelerometers are attached to the detector to characterize the chip's motion amplitude. However, since accelerometers measure acceleration rather than displacement and cannot be directly attached to the chip, it is impossible to directly characterize the chip's displacement. Summary of the Invention

[0004] To address the aforementioned problems in the prior art, this invention provides a device and method for testing the vibration displacement of an imaging detector chip.

[0005] To achieve the above objectives, this invention application provides the following technical solution:

[0006] An imaging detector chip vibration displacement testing device includes an LED planar light source, a homogenizing plate, an imaging lens, and an image acquisition card. The LED planar light source illuminates the imaging lens after passing through the homogenizing plate, and the position of the imaging detector chip under test is adjusted by shims so that it is exactly located at the focal plane of the imaging lens. The imaging lens includes a lens barrel and an aperture and a double-sided convex lens arranged sequentially in the inner cavity of the lens barrel according to the optical path. The image acquisition card is connected to the imaging detector under test and reads image data through a host computer.

[0007] Furthermore, the homogenizing plate is made of frosted glass, and the mesh count of the frosted glass is selected according to the illumination power of the LED planar light source.

[0008] Furthermore, the size of the small hole in the microscope tube is determined according to the following formula:

[0009] ,

[0010] in, For small hole size, For the size of the imaging spot, Foreground focal length, Back focal length; For object distance, Image distance, L represents the size of a single pixel, and W represents the horizontal and vertical resolutions of the imaging detector chip, respectively.

[0011] Furthermore, the lens barrel structure is designed based on the aperture size, the size of the double-sided convex lens, and the focal length. Modal simulation analysis is performed on the designed lens barrel structure, and its first-order modal frequency is... If the frequency exceeds the upper limit of the vibration spectrum tested, the designed lens barrel structure is qualified, and the inner cavity of the lens barrel is first milled out using an integral molding process, and finally the small hole is milled out.

[0012] Furthermore, the outer side of the aperture has a threaded structure, and it is inserted into the inner cavity of the lens barrel by adding thread-locking adhesive.

[0013] Furthermore, the inner cavity of the lens barrel is stepped; when installing the double-sided convex lens, the lens barrel is erected, and the double-sided convex lens is placed into the inner cavity of the lens barrel using tweezers. The lens is centered by utilizing the shoulder structure of the inner cavity of the lens barrel, and the lens retainer is screwed in to attach the double-sided convex lens. Finally, epoxy resin is injected through the glue injection hole and allowed to cure.

[0014] Furthermore, the light-inlet area of ​​the lens barrel is provided with a mounting groove. Epoxy resin is coated on the periphery of the homogenization plate and then inverted onto the mounting groove, and cured with glue.

[0015] Accordingly, this application also provides a method for testing the vibration displacement of an imaging detector chip, comprising the following steps:

[0016] Step 1: Fix the testing device to the vibration table or other vibration excitation source;

[0017] Step 2: Apply vibration loading according to the vibration spectrum to be tested;

[0018] Step 3: After the loading stabilizes, the host computer controls the image acquisition card to read the spot data. Each frame of the image contains the grayscale value of the spot. The centroid of the light spot in each frame of the image is calculated based on the centroid formula.

[0019] Step 4: Perform statistical analysis on the time-domain data of the light spot centroid, and use the root mean square error formula and peak-valley value formula to evaluate the chip displacement.

[0020] Furthermore, the root mean square error formula is as follows:

[0021] ,

[0022] Where RMS is the root mean square error, and n is the total number of image frames acquired. , Let x and y be the centroid coordinates of the light spot in the i-th frame image, respectively. , These are the average values ​​of the centroid coordinates of the light spot along the x-axis and y-axis, respectively.

[0023] Furthermore, the formula for the peak-valley value is:

[0024] ,

[0025] in, , These are the peak and valley values ​​in the x and y directions, respectively. , Let be the centroid coordinates of the light spot in the j-th frame image in the x and y directions, respectively. , and are the centroid coordinates of the light spot in the i-th frame in the x and y directions, respectively, and n is the total number of frames acquired.

[0026] The beneficial effects of this invention are as follows: This invention utilizes a planar light source to form diffuse reflection after being homogenized by a homogenizing plate, and then forms a point light source through a small aperture. It uses a single lens to achieve small spot imaging, and finally reads the centroid of the spot through an image acquisition card to directly characterize the chip displacement. The device of this invention has a simple structure, and the small aperture and imaging lens tube are integrated into one piece, which has high rigidity mechanical properties and reduces measurement interference caused by vibration-induced structural modes. By using the point light source imaging spot as a reference, the in-plane displacement of the chip is converted into the change of the centroid of the spot, which can directly characterize the in-plane displacement of the chip and the test accuracy can reach the pixel level. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structural composition of the vibration displacement testing device in the embodiments of this application.

[0028] Figure 2 This is a three-dimensional model diagram of the vibration displacement testing device in the embodiments of this application.

[0029] Figure 3 This is an optical schematic diagram of the vibration displacement testing device in the embodiments of this application.

[0030] Figure 4 This is a flowchart illustrating the installation and use process of the vibration displacement testing device in this application embodiment.

[0031] Figure 5 This is a geometric optical path model diagram of the vibration displacement testing device in the embodiments of this application.

[0032] Figure 6This is the result of the light spot reference stability analysis of the vibration displacement testing device in the embodiments of this application.

[0033] Figure 7 This is a diagram showing the test results of chip displacement in an embodiment of this application.

[0034] Figure 8 This is the time-domain curve of the chip in the Y-direction displacement obtained after data processing in the embodiments of this application.

[0035] Figure 9 This application includes RMS, PV statistics, and corresponding spot centroid distribution diagrams in the embodiments of this application. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] Example: Figure 1 and Figure 2 As shown, this application embodiment provides an imaging detector chip vibration displacement testing device, including an LED planar light source 1, a homogenizing plate 2, an imaging lens, and an image acquisition card; the LED planar light source 1 illuminates the imaging lens after passing through the homogenizing plate 2, and adjusts the position of the imaging detector chip 8 under test through a shim 7 so that it is exactly located at the focal plane position of the imaging lens; the imaging lens includes a lens barrel 4 and an aperture 3 and a double-sided convex lens 5 arranged sequentially in the inner cavity of the lens barrel 4 according to the optical path; the image acquisition card is connected to the imaging detector 8 under test and reads image data through a host computer.

[0038] In a preferred embodiment, the homogenizing plate 2 can be made of frosted glass (or an object with the function of homogenizing light, such as a milky white acrylic sheet or a frosted plastic sheet). The mesh count of the frosted glass affects the attenuation effect. The larger the mesh count, the more obvious the attenuation effect. The specific mesh count should be selected according to the illumination power of the LED planar light source 1 to avoid overexposure of the imaging spot. For example, the homogenizing plate 2 uses 1600 mesh frosted glass.

[0039] The imaging detector 8 has a photosensitive surface size of 8.2mm × 4.8mm, a pixel size of 4μm × 4μm, and a frame rate of 900fps @ 400 pixels × 400 pixels. The right side of the lens barrel 4 has a conical aperture. Based on calculations using lens and detector parameters, and considering the feasibility of aperture fabrication, the aperture diameter is chosen to be Ф0.2mm.

[0040] The lens barrel 4 and aperture 3 can be made of aluminum alloy 7075 or other high specific stiffness metals (Young's modulus to density ratio, recommended not less than 25.5×106m2 / s2). The lens barrel 4 and aperture 3 are made with a blackening process to reduce the influence of stray light. The LED planar light source 1 can be replaced with a fluorescent lamp or a low-power laser, provided that it meets the sensitive wavelength of the imaging detector 8 chip.

[0041] The dimensions of the four small holes in the lens tube are determined according to formula (1):

[0042] (1)

[0043] in, For small hole size, For the size of the imaging spot, Foreground focal length, Back focal length; For object distance, Image distance, L represents the size of a single pixel (if the pixel is not square, then the shorter side length is used), and W represents the horizontal and vertical resolutions of the imaging detector chip 8, respectively (generally not less than 100).

[0044] Based on the aforementioned aperture dimensions, double-convex lens 5 dimensions, and focal length, the lens barrel 4 structure was designed. The inner diameter of the lens barrel 4 was minimized as much as possible without obstruction to improve its rigidity. After the preliminary structural design was completed, modal simulation analysis was performed, yielding the first-order modal frequency as follows: ,like If the frequency exceeds the upper limit of the test vibration spectrum, it indicates that the structure of the lens barrel 4 has good rigidity and can be used for subsequent tests. Otherwise, the structure of the lens barrel 4 should be reinforced until the requirements are met. After the design is finalized, the inner cavity of the lens barrel 4 is milled first using an integral molding process, and finally the small hole is milled to complete the integrated small hole-lens barrel 4 manufacturing process.

[0045] In the embodiments of this application, such as Figure 3 As shown, the light emitted from the LED planar light source 1 is transmitted through a double-convex lens 5 and reaches the imaging detector chip 8 to achieve imaging. This optical system uses only one transmission device, ensuring a compact structure, resistance to vibration, and a near-Gaussian distribution and regular shape of the light spot, facilitating subsequent image processing. Figure 3In the diagram, points A and B are points on the object; the entire vertical arrow AB represents the object, and point B is the bottom endpoint of the object on the optical axis (the dashed line at the center). Points A' and B' are points on the image; the entire inverted vertical arrow A'B' represents the image formed by the object, and point B' is the bottom endpoint of the image on the optical axis. Points H and H' are principal points; point H is the first principal point, called the object-side principal point, located in object space; point H' is the second principal point, called the image-side principal point, located in image space. Points F and F' are foci; point F is the first focus, called the object-side focus; point F' is the second focus, called the image-side focus. Points H1 and H2 are the intersections of the light rays with the first principal plane. and points y' is the intersection of the ray and the second principal plane. y and y' are the lateral height of the object and the lateral height of the image, respectively. -x is the distance from the object to the first focal point. -f is the first focal length, called the object-side focal length, representing the horizontal distance from the first focal point F to the first principal point H (negative to the left). f' is the second focal length, called the image-side focal length, representing the horizontal distance from the second principal point H' to the second focal point F' (positive to the right). x' is the distance from the image to the second focal point. -l represents the horizontal distance from object B to the first principal point H, and -l' represents the distance from the second focal point F' to the image point B'.

[0046] In the embodiments of this application, such as Figure 4 As shown, the installation and use process of the vibration displacement testing device is as follows:

[0047] S101: Begin;

[0048] S102: Add some thread-locking adhesive to the outer thread of the aperture 3, then screw it into the inner cavity of the lens barrel 4 and wait for the thread-locking adhesive to cure.

[0049] S103: Stand the lens barrel 4 upright, and slowly insert the double-sided convex lens 5 into the inner cavity of the lens barrel 4 with tweezers. Use the shoulder structure of the inner cavity of the lens barrel 4 to center the double-sided convex lens 5. Slowly screw in the lens retainer 6 to stick to the surface of the double-sided convex lens 5, and inject epoxy resin through the glue injection hole. Wait for the glue to cure.

[0050] S104: Secure the imaging detector 8 with screws. The specific installation method can be adjusted according to the position of the chip in the imaging detector 8. For example, use an adapter plate or a shim 7 to adjust the front and back position of the chip along the light direction so that the chip is in the best imaging position and the size of the imaging spot satisfies formula (1).

[0051] S105: Apply epoxy resin to the edges of the homogenizing plate 2 and invert it onto the pre-reserved mounting position of the homogenizing plate 2 on the lens barrel 4, with the side with glue in contact with the lens barrel 4, and wait for the glue to cure.

[0052] S106: Secure the LED planar light source 1 with tape to prevent large displacement during vibration;

[0053] S107: Connect the image acquisition card and the imaging detector 8, turn on the LED planar light source 1, and read the image data through the host computer; if the light spot is overexposed, reduce the brightness of the LED planar light source 1 or replace it with a frosted glass with a higher mesh count.

[0054] S108: Fix the test device to the vibration table or other vibration excitation source;

[0055] S109: Apply vibration loading according to the vibration spectrum to be tested;

[0056] S110: After the loading stabilizes, the host computer controls the image acquisition card to read the spot data. Each frame of the image contains the spot gray value I(x,y). The spot centroid of each frame of the image is obtained according to the centroid formula (2):

[0057] (2)

[0058] Where X and Y are the coordinates of the centroid of the image spot in the x and y directions;

[0059] S111: After collecting data for a period of time, stop data collection and vibration loading;

[0060] S112: Perform statistical analysis on the time-domain data of the light spot centroid, and use formulas (3) and (4) to evaluate the chip displacement magnitude using the root mean square error (RMS) and peak-to-valley value (PV);

[0061] (3)

[0062] Where RMS is the root mean square error, and n is the total number of image frames acquired. , Let x and y be the centroid coordinates of the light spot in the i-th frame image, respectively. , These are the average values ​​of the centroid coordinates of the light spot along the x-axis and y-axis, respectively.

[0063] (4)

[0064] in, , These are the peak and valley values ​​in the x and y directions, respectively. , Let be the centroid coordinates of the light spot in the j-th frame image in the x and y directions, respectively. , , where are the centroid coordinates of the light spot in the i-th frame in the x and y directions, respectively, and n is the total number of frames acquired;

[0065] S113: End.

[0066] In this preferred embodiment, such as Figure 5The geometric model shown has a double-sided convex lens with a standard spherical surface, a radius of curvature of 24.5 mm, a focal length of 25.4 mm, a back focal length of 22.2 mm, an object distance of 79.7 mm, an image distance of 32.3 mm, a mechanical diameter of Ф25.4 mm, an edge thickness of 1.9 mm, a center thickness of 9.0 mm, and is made of N-BK7 material with no surface coating. It has a wavelength range of 350 nm to 2000 nm and good transmittance in the entire visible and near-infrared light regions.

[0067] In this embodiment of the application, by modal analysis, all degrees of freedom of the four mounting holes at the bottom are constrained, and the frequencies of the first two modes are 2376.4 Hz and 2799.9 Hz, indicating that the stiffness of the entire test device is very good.

[0068] In the embodiments of this application, Figure 6 The results of the stability analysis of the light spot reference in the embodiment are shown. Simulations were performed to measure the displacement of the light spot 3 at the chip location after the light passes through the imaging lens tube 4 in two in-plane directions. The black curve represents the vibration input spectrum of the displacement testing device, with a frequency range of 15Hz to 2000Hz and a root mean square value of 0.94g. Figure 5 For example, the vibration direction is X-axis (i.e., perpendicular to the paper plane). Under this vibration condition, the root mean square values ​​of the X-axis and Y-axis displacements of the imaging detector 8 chip are 0.0267 μm and 0.0002 μm, respectively, which are much smaller than the size of a single pixel. This indicates that the imaging spot stability of the point light source in this displacement testing device is good and can be used as a reference benchmark for the chip.

[0069] In the embodiments of this application, Figure 7 The chip displacement test results of the embodiment are shown on the left and right sides, respectively, the original spot image and the spot centroid coordinates obtained by the centroid extraction algorithm. Figure 8 This is the time-domain curve of the chip in the Y-axis displacement obtained after data processing. Figure 9 The RMS and PV statistics and the corresponding spot centroid distribution map are shown. The RMS value is 0.0228 pixels and the PV value is 0.1703 pixels.

[0070] In the description of embodiments of the present invention, the terms "first," "second," "third," and "fourth" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first," "second," "third," or "fourth" may explicitly or implicitly include one or more of that feature. In the description of the present invention, unless otherwise stated, "a plurality of" means two or more.

[0071] In the description of embodiments of the present invention, the term "and / or" is used only to describe the relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A alone, A and B simultaneously, and B alone. Additionally, the character " / " generally indicates that the preceding and following associated objects are in an "or" relationship.

[0072] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A vibration displacement testing device for an imaging detector chip, characterized in that, The system includes an LED planar light source, a homogenizing plate, an imaging lens, and an image acquisition card. The LED planar light source illuminates the imaging lens after passing through the homogenizing plate, and the position of the imaging detector chip under test is adjusted by shims so that it is exactly at the focal plane of the imaging lens. The imaging lens includes a lens barrel and an aperture and a double-sided convex lens arranged sequentially in the optical path inside the lens barrel. The lens barrel is manufactured using a one-piece molding process, first milling out the inner cavity of the lens barrel, and finally milling out a small hole. The image acquisition card is connected to the imaging detector under test and reads image data through a host computer.

2. The imaging detector chip vibration displacement testing device according to claim 1, characterized in that, The homogenizing plate is made of frosted glass, and the mesh count of the frosted glass is selected according to the lighting power of the LED planar light source.

3. The imaging detector chip vibration displacement testing device according to claim 1, characterized in that, The size of the aperture in the microscope tube is determined according to the following formula: ， in, For small hole size, For the size of the imaging spot, Foreground focal length, Back focal length; For object distance, Image distance, L represents the size of a single pixel, and W represents the horizontal and vertical resolutions of the imaging detector chip, respectively.

4. The imaging detector chip vibration displacement testing device according to claim 1, characterized in that, The lens barrel is designed based on the aperture size, the size of the double-convex lens, and the focal length. Modal simulation analysis is performed on the designed lens barrel structure, and its first-order modal frequency is... If the frequency exceeds the upper limit of the vibration spectrum tested in the experiment, then the designed lens tube structure is qualified.

5. The imaging detector chip vibration displacement testing device according to claim 1, characterized in that, The outer side of the aperture has a threaded structure, and it is inserted into the inner cavity of the lens barrel by adding thread-locking adhesive.

6. The imaging detector chip vibration displacement testing device according to claim 1, characterized in that, The inner cavity of the lens barrel is stepped. When installing the double-sided convex lens, the lens barrel is erected, and the double-sided convex lens is placed into the inner cavity of the lens barrel using tweezers. The lens is centered by utilizing the shoulder structure of the inner cavity of the lens barrel, and the lens retainer is screwed in to attach the double-sided convex lens. Finally, epoxy resin is injected through the glue injection hole and the glue is allowed to cure.

7. The imaging detector chip vibration displacement testing device according to claim 1, characterized in that, The light-inlet of the lens barrel is provided with a mounting groove. Epoxy resin is coated on the edges of the homogenization plate and then placed upside down on the mounting groove, and cured with glue.

8. A method for testing the vibration displacement of an imaging detector chip, comprising the imaging detector chip vibration displacement testing device as described in any one of claims 1 to 7, characterized in that, Includes the following steps: Step 1: Fix the testing device to the vibration table or other vibration excitation source; Step 2: Apply vibration loading according to the vibration spectrum to be tested; Step 3: After the loading stabilizes, the host computer controls the image acquisition card to read the spot data. Each frame of the image contains the grayscale value of the spot. The centroid of the light spot in each frame of the image is calculated based on the centroid formula. Step 4: Perform statistical analysis on the time-domain data of the light spot centroid, and use the root mean square error formula and peak-valley value formula to evaluate the chip displacement.

9. The method for testing the vibration displacement of an imaging detector chip according to claim 8, characterized in that, The formula for the root mean square error is: ， Where RMS is the root mean square error, and n is the total number of image frames acquired. , Let x and y be the centroid coordinates of the light spot in the i-th frame image, respectively. , These are the average values ​​of the centroid coordinates of the light spot along the x-axis and y-axis, respectively.

10. The method for testing the vibration displacement of an imaging detector chip according to claim 8, characterized in that, The formula for the peak-valley value is: ， in, , These are the peak and valley values ​​in the x and y directions, respectively. , Let be the centroid coordinates of the light spot in the j-th frame image in the x and y directions, respectively. , and are the centroid coordinates of the light spot in the i-th frame in the x and y directions, respectively, and n is the total number of frames acquired.

Images