A zoom camera fast calibration device

Abstract

A zoom camera fast calibration device, comprising a first calibration plate and a second calibration plate which are parallel to each other and are slidably installed on a slide rail, the slide rail is perpendicular to the plane where the calibration plates are located; the first calibration plate comprises a pair of width calibration plates which are symmetrically distributed on both sides of the slide rail, the center distance between the two width calibration plates is P1, and a center calibration plate is installed in the center of the two width calibration plates; the second calibration plate comprises at least a pair of width calibration regions which are symmetrically distributed on both sides of the slide rail, the center distance between the two width calibration regions is P2, and the second calibration plate further comprises a center calibration region located in the center of the two width calibration regions; the center calibration plate has a circular hole, and the line connecting the center of the circular hole and the center of the center calibration region is perpendicular to the two calibration plates. The calibration speed is fast, and the calibration can be completed by using only one image at each focal length; the calibration process is simple to operate, and only the center optical axis of the two calibration plates needs to be controlled to coincide.

Description

Technical Field

[0001] This utility model belongs to the field of optical technology and relates to camera calibration equipment, specifically a rapid calibration device for zoom cameras. Background Technology

[0002] In optical applications, camera calibration is a crucial step, and the calibration of the camera's field of view (FOV) is a particularly important parameter. In image-based measurement scenarios, the FOV is one of the most critical parameters to calculate. However, because the focal length of a zoom camera is continuously variable, and commonly used camera calibration methods are complex and cumbersome, typically only the maximum and minimum focal lengths of zoom cameras are calibrated or measured. In reality, it is necessary to calibrate the FOV at different focal lengths. Utility Model Content

[0003] To overcome the shortcomings of existing technologies, this utility model discloses a rapid calibration device for zoom cameras.

[0004] The zoom camera rapid 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 where 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.

[0005] The second calibration plate includes at least one pair of width calibration areas symmetrically distributed on both sides of the slide rail and not obscured 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 center calibration area located in the center of the two width calibration areas. The line connecting the center of the center calibration area and the center of the circular hole is perpendicular to the first calibration plate.

[0006] Preferably, the first calibration plate and the second calibration plate have pins that can be used to fix them to the slide rail.

[0007] Preferably, the slide rail has a scale.

[0008] Preferably, both the width calibration plate and the width calibration area have a cross pattern at their center.

[0009] Preferably, the second calibration plate includes two pairs of width calibration areas symmetrically distributed on both sides of the slide rail, and the four width calibration areas are symmetrically distributed relative to the central calibration area.

[0010] The zoom camera rapid calibration device described in this utility model has the following advantages over the prior art: fast calibration speed, calibration can be completed with only one image at each focal length; simple operation of the calibration process, only requiring the alignment of the central optical axes of the two calibration plates; and easy replacement of calibration plates of different sizes on the slide rail, allowing calibration of cameras operating under large focal length conditions in a relatively small space. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of a specific embodiment of the zoom camera rapid calibration device of this utility model;

[0012] Figure 2 This is a schematic diagram showing the angular position distribution of the two calibration plates along the sliding rail movement direction of the zoom camera rapid calibration device of this utility model.

[0013] Figure 3 This is a camera field-of-view recognition map in one specific implementation;

[0014] The attached 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-Clamping pin, 7-Center calibration plate, 8-Center calibration area. Detailed Implementation

[0015] The specific embodiments of this utility model will be further described in detail below with reference to the accompanying drawings.

[0016] The zoom camera rapid 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 7 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.

[0017] During measurement, mount the camera on the straight line of the slide rail. Observe the first and second calibration plates from the camera's field of view. Adjust the positions of the two calibration plates on the slide rail so that, when viewed from the camera, the circular hole on the center calibration plate is exactly in the center of the camera's field of view, and the center of the center calibration area can be seen through the circular hole. For convenient positioning, a locking pin 6 can be installed below the calibration plate, so that the slider below the calibration plate can be fixed on the slide rail 5.

[0018] 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.

[0019] Hfov=arctan((W2-W1) / Z).

[0020] 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.

[0021] 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:

[0022] Wi=Pd*(image_w) / (P2-P1); i=1,2.

[0023] 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.

[0024] like Figure 3 As shown, the calibration areas of the first and second calibration boards are visible within the camera's field of view. For the first calibration board, the two calibration points are the centers of the two width calibration boards 3; for the second calibration board, 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 boards and width calibration areas are typically marked with a crosshair 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 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.

[0025] 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.

[0026] The zoom camera rapid calibration device described in this utility model has the following advantages over the prior art: fast calibration speed, calibration can be completed with only one image at each focal length; simple operation of the calibration process, only requiring the alignment of the central optical axes of the two calibration plates; and easy replacement of calibration plates of different sizes on the slide rail, allowing calibration of cameras operating under large focal length conditions in a relatively small space.

[0027] 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. A rapid calibration device for a zoom camera, characterized in that, It includes a first calibration plate (1) and a second calibration plate (2) that are slidably mounted on a slide rail (5) and 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 (3) symmetrically distributed on both sides of the slide rail. The center distance between the two width calibration plates is P1. A center calibration plate (7) is 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 (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 center calibration area (8) located in the center of the two width calibration areas. The line connecting the center of the center calibration area (8) and the center of the circular hole is perpendicular to the first calibration plate (1).

2. The zoom camera rapid calibration device as described in claim 1, characterized in that, The first calibration plate and the second calibration plate (2) have pins (6) that can be fixed on the slide rail.

3. The zoom camera rapid calibration device as described in claim 1, characterized in that, The slide rail (5) has a scale.

4. The zoom camera rapid calibration device as described in claim 1, characterized in that, Both the width calibration plate (3) and the width calibration area (4) have a cross pattern in the center.

5. The zoom camera rapid calibration device as described in claim 1, characterized in that, The second calibration plate (2) includes two pairs of width calibration areas (4) symmetrically distributed on both sides of the slide rail, and the four width calibration areas are symmetrically distributed relative to the central calibration area (8).

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