Correction method for improving optical axis temperature stability of long-focus infrared camera

Abstract

The invention discloses a correction method for improving the temperature stability of a visual axis of a long-focus infrared camera. The correction method comprises the following steps: S1, testing the offset of the visual axis of a whole machine along with the temperature in an original assembly state; s2, testing the offset of the visual axis of the whole machine along with the temperature after the installation direction of the head mirror is rotated by 180 degrees; s3, testing the offset of the optical axis of the whole machine along with the temperature after the mounting directions of the head mirror and the secondary mirror are rotated by 180 degrees; s4, calculating angles required to be rotated by the head mirror and the secondary mirror; and S5, rotating the head mirror and the secondary mirror to the target angle, and then reinstalling the head mirror and the secondary mirror. According to the method, the optical axis offset after temperature change can be effectively reduced and the temperature stability of the infrared camera can be improved by utilizing the superposition relation of the influence of different lens groups on the optical axis in temperature change without calibrating each temperature point and adopting an assembling and adjusting method under the condition that the technical state is not changed.

Description

Technical Field

[0001] The invention relates to the technical field of camera correction, and in particular to a correction method for improving the temperature stability of the visual axis of a telephoto infrared camera. Background Art

[0002] With the development of infrared technology, higher requirements are placed on the imaging performance and environmental adaptability of infrared cameras. In practical applications, as the temperature changes, the camera's visual axis will also shift to a certain extent. Visual axis stability under a wide temperature range is a common problem, especially for optical systems with long focal lengths. This problem will be more obvious because of slight changes in structural deformation, stress changes, adhesive expansion, lens group eccentricity, lens group deflection, etc. caused by changes in ambient temperature, which will cause changes in the visual axis of the final infrared imaging system. Usually, methods such as enhancing structural rigidity, controlling the gluing process, and image algorithm correction are used to deal with it. However, enhancing structural rigidity will increase weight and cost, and cannot solve the visual axis changes caused by the lens; the gluing process can only improve the temperature stability of a single lens group, and has limited effect on the entire machine; using an algorithm to align the visual axis at the image output end cannot fundamentally solve the visual axis problem, and has high requirements for the calibration environment, requiring a relatively complex calibration process. The visual axis stability problem of long-focal-length infrared cameras at different temperatures is a complex problem caused by multiple reasons, and is a difficult point in the optical and mechanical design and assembly of long-focal-length infrared cameras. Summary of the invention

[0003] In order to solve the above-mentioned deficiencies in the prior art, the present invention proposes a correction method for improving the temperature stability of the visual axis of a telephoto infrared camera.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solution: a correction method for improving the temperature stability of the visual axis of a telephoto infrared camera, comprising the following steps:

[0005] S1. Test the deviation of the visual axis of the whole machine with temperature in the original assembly state

[0006] At room temperature, align the assembled infrared camera with the collimator, heat the infrared camera to a temperature rise of 15 degrees, observe and record the visual axis offset of the infrared camera, recorded as

[0007] S2. Test the deviation of the visual axis of the whole machine due to temperature after the installation direction of the head mirror is rotated 180 degrees

[0008] After the infrared camera in step S1 is naturally cooled to room temperature, the installation angle of the head mirror is rotated 180 degrees and reinstalled;

[0009] Aim the infrared camera at the collimator, and align the center of the infrared camera output image with the fixed target point of the collimator. Fix the infrared camera so that it remains in the same position during the experiment.

[0010] Use the constant temperature heating box to heat the infrared camera again to a temperature rise of 15 degrees, observe and record the visual axis offset of the infrared camera, recorded as

[0011] S3, test the deviation of the visual axis of the whole machine with temperature after the installation direction of the head mirror and the secondary mirror are rotated 180 degrees

[0012] After the temperature of the infrared camera in step S2 drops back to normal temperature, rotate the installation angle of the secondary mirror by 180 degrees and reinstall it. During this process, ensure that the installation direction of the head mirror is consistent with that in step 2;

[0013] S4. Calculate the angles that the head mirror and the secondary mirror need to rotate

[0014] Observe and record the visual axis offset of the infrared camera, recorded as

[0015] S5. Rotate the head mirror and secondary mirror to the target angle and reinstall them. Perform another experiment to verify the deviation of the visual axis with temperature.

[0016] According to the rotation angle values ​​of the head mirror and the secondary mirror obtained in step S4, the head mirror and the secondary mirror are rotated to the corresponding angles and reassembled, and the visual axis offset of the infrared camera is observed and recorded, which is recorded as

[0017] Furthermore, it also includes:

[0018] The head mirror causes the optical axis to shift pixels, the optical axis offset caused by the secondary mirror is pixels, the optical axis offset caused by other mirror groups is Pixel.

[0019] Furthermore, in step S3, it also includes:

[0020] After the temperature of the infrared camera in step S2 drops back to normal temperature, rotate the installation angle of the secondary mirror by 180 degrees and reinstall it. During this process, ensure that the installation direction of the head mirror is consistent with that in step 2, and align the infrared camera with the collimator again.

[0021] The center of the infrared camera output image is aligned with the fixed target point of the collimator. The infrared camera is fixed to keep its position unchanged during the experiment. The infrared camera is heated to a temperature rise of 15 degrees using a constant temperature heating box. The visual axis offset of the infrared camera is observed and recorded as

[0022] Furthermore, it also includes:

[0023] Assume that in the original state, the total system offset of step 1 of S1 is After the head mirror is rotated 180 degrees through step S2, the head mirror will cause the optical axis to shift - The secondary mirror causes the optical axis to shift At this time, the system offset is Calculate according to method (1).

[0024] Furthermore, the calculation method of the method (1) is:

[0025] Further, according to step S3, after the head mirror and the secondary mirror are rotated 180 degrees again, the head mirror will cause the optical axis to shift -

[0026] The secondary mirror causes the optical axis to shift - At this time, the system offset is Calculate according to method (2).

[0027] Furthermore, the method (ii) is

[0028] Furthermore, according to equations (1) and (2), the optical axis offset caused by the head mirror can be calculated:

[0029] The secondary mirror causes the optical axis to shift And other mirror groups cause the optical axis to shift During operation, the head mirror and the secondary mirror are relatively easy to rotate. and direction, that is, in Superimpose a vector on exist Superimpose a vector on The final system offset satisfies the calculation method of method (III), which is calculated as follows:

[0030] Furthermore, in step S4, it also includes: according to formula (1), formula (2) and formula (3), the head mirror rotation can be calculated secondary mirror After that, the final system offset can be That is, the total offset of the system is zero, achieving temperature stability of the optical axis.

[0031] Further, after step S5 is completed, the analysis Whether the requirements are met.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1. This method can utilize the superposition relationship of the influence of different lens groups on the visual axis during temperature changes without changing the technical status. It does not need to calibrate each temperature point. The assembly adjustment method is used to effectively reduce the optical axis offset after temperature changes and improve the temperature stability of the infrared camera.

[0034] 2. Through design simulation and experimental testing, it is found that for infrared cameras with multi-lens group transmission design, the influence of each lens group on the visual axis as the temperature changes is independent of each other. After the interaction of each lens group, the change in the overall imaging position is the superposition of the changes in direction and value under the influence of each lens group alone. At the same time, the influence of different lens groups on the imaging position varies greatly. Usually, the head mirror and secondary mirror have the most significant influence. The influence of the assembled head mirror, secondary mirror and other lens groups on the visual axis after temperature changes can be quantitatively measured by experimental methods. Then, by adjusting the installation angles of the head mirror and secondary mirror, the vector sum of the influence of the head mirror, secondary mirror and other lens groups on the visual axis is minimized, thereby correcting the temperature stability of the visual axis through installation and adjustment. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Schematic diagram of the infrared camera's line of sight offset. DETAILED DESCRIPTION

[0036] The invention is described in detail below with reference to the accompanying drawings and embodiments.

[0037] Example 1

[0038] A correction method for improving the temperature stability of the visual axis of a telephoto infrared camera, the operation steps are as follows:

[0039] The first step is to test the deviation of the visual axis of the whole machine with temperature in the original assembly state.

[0040] 1. Align the assembled infrared camera with the collimator at room temperature. Align the center of the infrared camera output image with the fixed target point of the collimator. Fix the infrared camera so that it remains in the same position during the experiment.

[0041] 2. Use a constant temperature heating box to heat the infrared camera to a temperature rise of 15 degrees.

[0042] 3. Observe and record the visual axis offset of the infrared camera, recorded as

[0043] The second step is to test the deviation of the visual axis of the whole machine due to temperature after the installation direction of the head mirror is rotated 180 degrees.

[0044] 1. After the first step of the experiment, wait for the temperature of the infrared camera to drop back to normal temperature, then rotate the installation angle of the head mirror 180 degrees and reinstall it.

[0045] 2. Aim the infrared camera at the collimator again. Align the center of the infrared camera output image to the fixed target point of the collimator. Fix the infrared camera so that it remains in the same position during the experiment.

[0046] 3. Use a constant temperature heating box to heat the infrared camera to a temperature rise of 15 degrees.

[0047] 4. Observe and record the visual axis offset of the infrared camera, recorded as

[0048] The head mirror causes the optical axis to shift pixels, the optical axis offset caused by the secondary mirror is pixels, the optical axis offset caused by other mirror groups is pixels, the total offset of the system is

[0049] Assume that in the original state, the total system offset is After rotating the head mirror 180 degrees, the head mirror will cause the optical axis to shift - The secondary mirror causes the optical axis to shift At this time, the system offset is Calculation method (I) is:

[0050]

[0051] The third step is to test the offset of the visual axis of the whole machine due to temperature after the installation directions of the head mirror and the secondary mirror are rotated 180 degrees.

[0052] 1. After the second step of the experiment, wait for the temperature of the infrared camera to return to normal temperature, rotate the installation angle of the secondary mirror 180 degrees and reinstall it. During this process, ensure that the installation direction of the head mirror is consistent with that in the second step.

[0053] 2. Aim the infrared camera at the collimator again. Align the center of the infrared camera output image to the fixed target point of the collimator. Fix the infrared camera so that it remains in the same position during the experiment.

[0054] 3. Use a constant temperature heating box to heat the infrared camera to a temperature rise of 15 degrees.

[0055] 4. Observe and record the visual axis offset of the infrared camera, recorded as

[0056] After the head mirror and the secondary mirror are rotated 180 degrees, the head mirror will cause the optical axis to shift - The secondary mirror causes the optical axis to shift -

[0057] At this time, the system offset is Calculation method (II) is:

[0058] According to equations (1) and (2), the optical axis offset caused by the head mirror can be calculated: The secondary mirror causes the optical axis to shift And other mirror groups cause the optical axis to shift During operation, the head mirror and the secondary mirror are relatively easy to rotate. and direction, that is, in Superimpose a vector on

[0059] exist Superimpose a vector on The final system offset satisfies calculation method (III), which is:

[0060]

[0061] The fourth step is to calculate the angles that the head mirror and secondary mirror need to rotate.

[0062] According to formula (1), formula (2) and formula (3), calculate the head mirror rotation secondary mirror

[0063] Step 5: Rotate the head mirror and secondary mirror to the target angle and reinstall them. Perform another experiment to verify the temperature deviation of the visual axis.

[0064] 1. According to the rotation angle values ​​of the head mirror and secondary mirror obtained in step 4, rotate the head mirror and secondary mirror to the corresponding angles and reassemble them.

[0065] 2. Align the assembled infrared camera with the collimator at room temperature. Align the center of the infrared camera output image with the fixed target point of the collimator. Fix the infrared camera so that it remains in the same position during the experiment.

[0066] 3. Use a constant temperature heating box to heat the infrared camera to a temperature rise of 15 degrees.

[0067] 4. Observe and record the visual axis offset of the infrared camera, recorded as

[0068] 5. According to formula (1), formula (2) and formula (3), the head mirror rotation can be calculated secondary mirror After that, the final system offset can be That is, the total system offset is zero, achieving temperature stability of the optical axis.

[0069] Whether the requirements are met.

[0070] The above embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for those of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the patent and protection scope of the present invention shall be subject to the attached claims.

Claims

1. A correction method for improving the temperature stability of the visual axis of a telephoto infrared camera, characterized in that: The following steps are involved: S1. Test the deviation of the visual axis of the whole machine with temperature in the original assembly state At room temperature, align the assembled infrared camera with the collimator, heat the infrared camera to a temperature rise of 15 degrees, observe and record the visual axis offset of the infrared camera, recorded as S2. Test the deviation of the visual axis of the whole machine due to temperature after the installation direction of the head mirror is rotated 180 degrees After the infrared camera in step S1 is naturally cooled to room temperature, the installation angle of the head mirror is rotated 180 degrees and reinstalled; Aim the infrared camera at the collimator, and align the center of the infrared camera output image with the fixed target point of the collimator. Fix the infrared camera so that it remains in the same position during the experiment. Use the constant temperature heating box to heat the infrared camera again to a temperature rise of 15 degrees, observe and record the visual axis offset of the infrared camera, recorded as S3, test the deviation of the visual axis of the whole machine with temperature after the installation direction of the head mirror and the secondary mirror are rotated 180 degrees After the temperature of the infrared camera in step S2 drops back to normal temperature, rotate the installation angle of the secondary mirror by 180 degrees and reinstall it. During this process, ensure that the installation direction of the head mirror is consistent with that in step 2; S4. Calculate the angles that the head mirror and the secondary mirror need to rotate Observe and record the visual axis offset of the infrared camera, recorded as S5. Rotate the head mirror and secondary mirror to the target angle and reinstall them. Perform another experiment to verify the deviation of the visual axis with temperature. According to the rotation angle values ​​of the head mirror and the secondary mirror obtained in step S4, the head mirror and the secondary mirror are rotated to the corresponding angles and reassembled, and the visual axis offset of the infrared camera is observed and recorded, which is recorded as 2. A correction method for improving the temperature stability of the visual axis of a telephoto infrared camera as claimed in claim 1, characterized in that: Also includes: The head mirror causes the optical axis to shift pixels, the optical axis offset caused by the secondary mirror is pixels, the optical axis offset caused by other mirror groups is Pixel.

3. A correction method for improving the temperature stability of the visual axis of a telephoto infrared camera as claimed in claim 2, characterized in that: In the S3 step, it also includes: After the temperature of the infrared camera in step S2 drops back to normal temperature, rotate the installation angle of the secondary mirror by 180 degrees and reinstall it. During this process, ensure that the installation direction of the head mirror is consistent with that in step 2, and align the infrared camera with the collimator again. Align the center position of the infrared camera output image with the fixed target point of the collimator. Fix the infrared camera so that it remains in the same position during the experiment, use a constant temperature heating box to heat the infrared camera to a temperature rise of 15 degrees, observe and record the visual axis offset of the infrared camera, recorded as 4. A correction method for improving the temperature stability of the visual axis of a telephoto infrared camera as claimed in claim 3, characterized in that: Also includes: Assume that in the original state, the total system offset of step 1 of S1 is After the head mirror is rotated 180 degrees through step S2, the head mirror will cause the optical axis to shift - The secondary mirror causes the optical axis to shift At this time, the system offset is Calculate according to method (1).

5. A correction method for improving the temperature stability of the visual axis of a telephoto infrared camera as claimed in claim 4, characterized in that: The calculation method of method (1) is:

6. A correction method for improving the temperature stability of the visual axis of a telephoto infrared camera as claimed in claim 5, characterized in that: According to step S3, after the head mirror and the secondary mirror are rotated 180 degrees again, the head mirror will cause the optical axis to shift - The secondary mirror causes the optical axis to shift - At this time, the system offset is Calculate according to method (2).

7. A correction method for improving the temperature stability of the visual axis of a telephoto infrared camera as claimed in claim 6, characterized in that: The method (ii) is 8. A correction method for improving the temperature stability of the visual axis of a telephoto infrared camera as claimed in claim 7, characterized in that: According to equations (1) and (2), the optical axis deviation caused by the head mirror can be calculated: The secondary mirror causes the optical axis to shift And other mirror groups cause the optical axis to shift During operation, the head mirror and the secondary mirror are relatively easy to rotate. and direction, that is, in Superimpose a vector on exist Superimpose a vector on The final system offset satisfies the calculation method of method (3), which is calculated as follows:

9. A correction method for improving the temperature stability of the visual axis of a telephoto infrared camera as claimed in claim 8, characterized in that: In step S4, it also includes: according to formula (1), formula (2) and formula (3), the head mirror rotation can be calculated secondary mirror After that, the final system offset can be That is, the total offset of the system is zero, achieving temperature stability of the optical axis.

10. A correction method for improving the temperature stability of the visual axis of a telephoto infrared camera as claimed in claim 9, characterized in that: After step S5 is completed, the analysis Whether the requirements are met.

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