An infrared camera calibration device

Abstract

The utility model provides an infrared camera calibration device, including first calibration board and second calibration board who are parallel to each other and are slidably installed on slide rail, and the slide rail is perpendicular to the plane where calibration board is, first calibration board includes a pair of symmetrical distribution width calibration board in the both sides of slide rail, and the center calibration board is installed in the center of two width calibration board, second calibration board includes at least a pair of symmetrical distribution width calibration area in the both sides of slide rail, and second calibration board also includes the center calibration area in the center of two width calibration area, the width calibration board and width calibration area all include the hollowed part on, installs the light emitting device who is evenly distributed in the area of not belonging to the hollowed part, and the circuit board who is connected with light emitting device electricity, adopt infrared camera calibration device described in the utility model, can utilize light emitting device to combine infrared camera imaging to the field of view angle parameter of fast infrared camera calibration.

Description

Technical Field

[0001] This utility model belongs to the field of optical technology and relates to camera calibration equipment, specifically to an infrared camera calibration device. Background Technology

[0002] Currently, most common camera calibration methods and techniques are designed for visible light. Calibration methods for infrared cameras are relatively few and more expensive. This is because infrared cameras generally have much lower imaging resolution than visible light cameras, and their imaging characteristics are also very different. The applicant disclosed a zoom camera calibration device for visible light in Chinese patent application number 2025217276671, but this device is difficult to use for infrared cameras and cannot be used for calibrating the field of view of infrared cameras. Utility Model Content

[0003] To overcome the shortcomings of existing technologies, this utility model discloses an infrared camera calibration device.

[0004] The infrared camera calibration device of this utility model includes a first calibration plate and a second calibration plate that are slidably mounted on a slide rail and are parallel to each other. The slide rail is perpendicular to the plane in which the calibration plates are located. The first calibration plate includes a pair of width calibration plates symmetrically distributed on both sides of the slide rail, with a center distance of P1 between the two width calibration plates, and a center calibration plate installed in the center of the two width calibration plates. The center calibration plate has a circular hole in the center. The second calibration plate includes at least one pair of width calibration areas symmetrically distributed on both sides of the slide rail and not obstructed by the first calibration plate. The center-to-center distance between the two width calibration areas is P2, and P2 is not equal to P1. The second calibration plate also includes a central calibration area located in the center of the two width calibration areas. The line connecting the center of the central calibration area and the center of the circular hole is perpendicular to the first calibration plate. Both the width calibration plate and the width calibration area include hollowed-out portions. Light-emitting devices are uniformly distributed in areas not belonging to the hollowed-out portions, as well as circuit boards electrically connected to the light-emitting devices.

[0005] Preferably, the light-emitting device is an infrared lamp bead.

[0006] Preferably, the cutout portion is located at the geometric center of the width calibration area, the light-emitting devices are centrally symmetrically distributed around the geometric center, and the circuit board is located in the center of a pair of width calibration areas.

[0007] Preferably, the hollowed-out portion and the light-emitting device are centrally symmetrical and staggered about the geometric center of the width calibration plate, and the circuit board is located at the geometric center of the width calibration plate.

[0008] The infrared camera calibration device described in this invention can be used to quickly calibrate the field of view parameters of an infrared camera by combining the light-emitting device with the infrared camera imaging. Attached Figure Description

[0009] Figure 1 This is a schematic diagram of a specific embodiment of the infrared camera calibration device described in this utility model; Figure 2 This is a schematic diagram showing the angular position distribution of the two calibration plates of the infrared camera calibration device described in this utility model along the sliding rail movement direction; The figures are labeled as follows: 1-First calibration plate, 2-Second calibration plate, 3-Width calibration plate, 4-Width calibration area, 5-Slide rail, 6-Circuit board, 8-Center calibration area, 9-Kucker part, 10-Light-emitting device. Detailed Implementation

[0010] The specific embodiments of this utility model will be further described in detail below with reference to the accompanying drawings.

[0011] The infrared camera calibration device described in this utility model, such as Figure 1 and Figure 2 The system includes a first calibration plate 1 and a second calibration plate 2 that are slidably mounted on a slide rail and are parallel to each other. The slide rail 5 runs perpendicular to the plane in which the calibration plates are located. The first calibration plate 1 includes a pair of width calibration plates 3 symmetrically distributed on both sides of the slide rail, with a center-to-center distance of P1 between the two width calibration plates, and a center calibration plate installed in the center of the two width calibration plates. The second calibration plate 2 includes at least a pair of width calibration areas 4 symmetrically distributed on both sides of the slide rail and not obstructed by the first calibration plate, with a center-to-center distance of P2 between the two width calibration areas. The second calibration plate also includes a center calibration area located in the center of the two width calibration areas. The center calibration plate has a circular hole in the center, and the line connecting the center of the circular hole and the center of the center calibration area 8 is perpendicular to the two calibration plates.

[0012] Both the width calibration plate and the width calibration area include a cutout portion 9. Light-emitting devices 10 are evenly distributed in areas not belonging to the cutout portion, and a circuit board 6 electrically connected to the light-emitting devices is installed.

[0013] During measurement, the infrared camera is mounted on the straight line of the slide rail. The first and second calibration plates are observed from the camera's field of view. The positions of the two calibration plates on the slide rail are adjusted so that, when viewed from the camera, the circular hole on the central calibration plate is precisely in the center of the camera's field of view, and the center of the central calibration area can be seen through the hole. For easier positioning, a locking pin can be installed below the calibration plate, allowing the slider below the calibration plate to be fixed to the slide rail 5.

[0014] Can Figure 1 As shown, a cross pattern is cut out in the central calibration area to facilitate observation by the infrared camera.

[0015] The light-emitting device is turned on. The light-emitting device is preferably an infrared lamp bead that emits only infrared light. After the light-emitting device is turned on, combined with the evenly distributed hollow part and the light-emitting device, the infrared camera can quickly identify whether the center calibration area is located in the circular hole by relying on existing image recognition software, as well as identify the geometric center of the width calibration plate and the width calibration area.

[0016] After the above adjustments are completed, the camera's optical center is aligned with the optical axis, simplifying the imaging matrix calculation. The camera's horizontal field of view Hfov can be calculated using the following set of formulas. Hfov=arctan((W2-W1) / Z).

[0017] Z represents the distance between the first and second calibration plates on the slide rail. To facilitate the detection of Z, a scale can be marked on the slide rail.

[0018] W1 and W2 are the horizontal widths of the first and second calibration plates coinciding with the camera's field of view, respectively, calculated using the following formula: Wi=Pd*(image_w) / (P2-P1); i=1,2.

[0019] image_w is the horizontal pixel width of the camera, P2-P1 is the difference in the horizontal pixel sequence of two calibration points measured on the image obtained by the camera, and Pd is the true spatial distance between the two corresponding calibration points.

[0020] like Figure 1 As shown, these are the calibration points of the first calibration plate 1 and the second calibration plate 2 as seen within the camera's field of view. For the first calibration plate, the two calibration points are the centers of the two width calibration plates 3; for the second calibration plate, the two calibration points are the centers of the two width calibration areas 4. To facilitate rapid recognition by existing image recognition software, the centers of the width calibration plates and width calibration areas are usually marked with a cross pattern. Existing image recognition software can identify the horizontal pixel sequence values ​​of the calibration points and calculate the difference in the horizontal pixel sequence values ​​between the two calibration points, thereby calculating W1 and W2. After calculating the camera's horizontal field of view, the vertical field of view of the camera can be obtained by using the same method or by directly multiplying it by the camera's horizontal-to-vertical pixel ratio, thus achieving the calibration of the camera's field of view parameters.

[0021] In actual operation, when positioning the second calibration plate, it is usually not easy to precisely adjust the center of the central calibration area to be located at the center of the camera's field of view and to ensure that the calibration plate is completely perpendicular to the camera's optical axis. Therefore, for the second calibration plate, two or more sets of width calibration areas can usually be set up, symmetrically distributed relative to the central calibration area of ​​the second calibration plate. In specific calculations, each set of width calibration areas obtains a W2 value, and finally the average value of each W2 value is taken. Since each calibration area is symmetrically distributed relative to the central calibration area, the average value can offset the error of each set of width calibration areas and improve accuracy.

[0022] Figure 1 In the specific embodiment shown, for the width calibration area 4 of the second calibration plate 2, the hollow portion 9 is located at the geometric center of the width calibration area 4, the light-emitting device 10 is centrally symmetrically distributed around the geometric center, and the circuit board 6 is located in the center of a pair of width calibration areas.

[0023] Since the second calibration plate 2 is located behind the slide rail 5, the width calibration area 4 can be adjacent to each other. A single circuit board 6 can be used to power the light-emitting devices of the two width calibration areas 4. The cutout part only needs to be drilled in the width calibration area, which simplifies the processing of the width calibration area.

[0024] Figure 1 In the specific embodiment shown, the hollow portion 9 and the light-emitting device 10 are centrally symmetrical and staggered about the geometric center of the width calibration plate, and the circuit board is located at the geometric center of the width calibration plate.

[0025] Since the first calibration board 1 is located in front of the second calibration board 2, the width calibration board 3 cannot block the second calibration board behind it, resulting in a large distance between the width calibration boards. The circuit board 6 can only supply power to the light-emitting device on one width calibration board at a time.

[0026] Circuit boards typically contain electronic components such as batteries, driver chips for light-emitting devices, and switches. The specific configuration is existing technology in this field and will not be described in detail here. For ease of implementation, the first calibration board and the second calibration board can be PCB boards, and the circuit board and light-emitting devices can be directly arranged on the PCB board.

[0027] The infrared camera calibration device described in this invention allows for the rapid calibration of the field of view parameters of an infrared camera using a light-emitting device combined with infrared camera imaging. This invention primarily addresses the rapid and simple calibration of infrared cameras, calibrating only the camera's field of view parameters without considering imaging distortion, such as radial and tangential distortion. Severe distortion in these two areas can negatively impact the calculated field of view parameters. This invention is suitable for relatively simple applications, such as low-precision infrared distance and width measurement, rapid verification of product consistency, and acceptance testing of incoming products—applications where the calculation can be completed based primarily on the camera's field of view parameters.

[0028] The foregoing descriptions are preferred embodiments of this utility model. Unless there is a clear contradiction between the preferred embodiments or a prerequisite for a particular preferred embodiment, the preferred embodiments can be arbitrarily combined and used. The embodiments and specific parameters described are only for clearly illustrating the utility model verification process of the inventor and are not intended to limit the patent protection scope of this utility model. The patent protection scope of this utility model is still subject to its claims. Similarly, any equivalent structural changes made based on the description and drawings of this utility model should also be included within the protection scope of this utility model.

Claims

1. An infrared camera calibration device, comprising a first calibration plate (1) and a second calibration plate (2) slidably mounted on a slide rail (5) and parallel to each other, wherein the slide rail is perpendicular to the plane in which the calibration plates are located; the first calibration plate comprises a pair of width calibration plates (3) symmetrically distributed on both sides of the slide rail, the center distance between the two width calibration plates being P1, and a center calibration plate mounted in the center of the two width calibration plates, wherein the center calibration plate has a circular hole in the center; The second calibration plate (2) includes at least one pair of width calibration areas (4) symmetrically distributed on both sides of the slide rail and not obscured by the first calibration plate. The center distance between the two width calibration areas (4) is P2, and P2 is not equal to P1. The second calibration plate also includes a central calibration area (8) located in the center of the two width calibration areas. The line connecting the center of the central calibration area (8) and the center of the circular hole is perpendicular to the first calibration plate (1). Its features are, Both the width calibration plate and the width calibration area include a cutout portion (9), and a uniformly distributed light-emitting device (10) is installed in the area that is not part of the cutout portion, as well as a circuit board (6) electrically connected to the light-emitting device.

2. The infrared camera calibration device as described in claim 1, characterized in that, The light-emitting device (10) is an infrared lamp bead.

3. The infrared camera calibration device as described in claim 1, characterized in that, The hollow portion (9) is located at the geometric center of the width calibration area (4), the light-emitting devices (10) are centrally symmetrically distributed around the geometric center, and the circuit board (6) is located in the center of a pair of width calibration areas.

4. The infrared camera calibration device as described in claim 1, characterized in that, The hollowed-out portion (9) and the light-emitting device (10) are centrally symmetrical and staggered about the geometric center of the width calibration plate (3), and the circuit board (6) is located at the geometric center of the width calibration plate (3).

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