Automatic mapping system and method for optical servo parameters of continuous zooming thermal imager

Abstract

The invention discloses an automatic mapping system for optical servo parameters of a continuous zooming thermal imager. The automatic mapping system is composed of the thermal imager, a high and low temperature test box germanium window, a collimator, a high and low temperature test box, a plurality of fan-shaped target modules with different spatial frequencies, a black body module, a high and low temperature box numerical control module, an upper computer and a power supply. The thermal imager is arranged in the high and low temperature test box, the high and low temperature test box is provided with a high and low temperature test box germanium window and a high and low temperature box numerical control module, and a collimator, a plurality of fan-shaped target modules with different spatial frequencies and a black body module are sequentially arranged in the direction of the box germanium window; the power supply is connected with the thermal imager and the upper computer through cables; the upper computer is connected with the thermal imager, the high and low temperature box numerical control module and the black body module through cables. The system can automatically adjust the temperature of the high and low temperature box and the target, and automatic mapping of optical servo parameters of the thermal imager under the condition of multiple temperature zones is realized; a quantitative calibration is provided for positioning the optical axis compensating mirror group in different temperature zones, so that the focusing precision is improved, and the image clearness of the thermal imager is ensured; and the image quality of a product and the performance of the whole machine are ensured.

Description

Technical Field

[0001] The invention relates to the field of thermal imagers, and in particular to an automatic calibration system and method for optical servo parameters of a continuous zoom thermal imager. Background Art

[0002] In recent years, in order to improve performance, thermal imagers have gradually developed into staring cooled thermal imagers, and scanning thermal imagers have gradually withdrawn from the stage of history. Domestic and foreign infrared detection technologies tend to have larger arrays, smaller pixels, ultra-high resolution, and higher sensitivity. Multi-band coverage of short-wave, medium-wave, and long-wave dual-color or three-color or even four-color, staring thermal imagers cover near-infrared, short-wave, medium-wave, long-wave, very long-wave infrared and even visible light. Some existing adjustment systems and methods for infrared thermal imaging devices all perform image quality tests (focal length, distortion) for specific fields of view (one, two or more) of thermal imagers; however, for thermal imagers using continuous zoom optical systems, since the entire zoom process requires clear imaging, the workload of optical axis calibration work has increased exponentially compared to the existing domestic continuous zoom thermal imager focus adjustment method, and it is completely unable to meet the debugging needs of continuous zoom thermal imagers.

[0003] At present, the automatic test system of the optical axis of thermal imagers in China is mainly aimed at debugging the infrared optical servo parameters of two or more fields of view. The following three problems were found in the process of investigating this method: 1. The focal length debugging system of the infrared optical system with two or more fields of view can only solve the focus debugging of two or more specific fields of view, and cannot present a stable and clear image in the continuous zoom process during the entire infrared imaging process. It is not suitable for the actual production calibration of the continuous zoom optical system thermal imager production line. 2. During the debugging process, it cannot provide an effective calibration for the continuous zoom process, so it cannot fully guarantee the accuracy of the positioning parameters of the focus compensation lens group. 3. When calculating the continuous zoom positioning parameters, the process data is too complicated. If manual auxiliary calculation is used, it will seriously affect the production efficiency. Therefore, after comparing the relevant industries and research status at home and abroad, we proposed a new automatic focus calibration system and method for the optical system of continuous zoom thermal imagers. Summary of the invention

[0004] To solve the above problems, the first aspect of the present invention provides an automatic calibration system for optical servo parameters of a continuous zoom thermal imager, which consists of a thermal imager, a high and low temperature test chamber germanium window, a collimator, a high and low temperature test chamber, a multi-rod fan-shaped target module with different spatial frequencies, a black body module, a high and low temperature chamber numerical control module, a host computer and a power supply; the thermal imager is arranged in the high and low temperature test chamber, and the high and low temperature test chamber is provided with a high and low temperature test chamber germanium window and a high and low temperature chamber numerical control module, and a collimator, a multi-rod fan-shaped target module with different spatial frequencies and a black body module are arranged in sequence in the direction of the box germanium window; the power supply is connected to the thermal imager and the host computer through a cable; the host computer is connected to the thermal imager, the high and low temperature chamber numerical control module and the black body module through a cable. The infrared target information is radiated from the black body module surface source, passes through the multi-rod fan-shaped target module target and collimator with different spatial frequencies, passes through the germanium window of the high and low temperature test chamber, enters the high and low temperature test chamber, and is received by the thermal imager lens. The multi-rod fan-shaped target module with different spatial frequencies is installed in front of the black body module to ensure that the black body radiates infrared light information. After passing through the inverted trapezoidal target, it passes through the collimator to form parallel emission infrared target information, so as to facilitate the thermal imager to collect image information. The high and low temperature test chamber works at different temperature points according to the needs of the calibration, and the temperature range covers from -40 to 70°C.

[0005] According to another aspect of the present invention, a method for automatically measuring optical servo parameters of a continuous zoom thermal imager is provided, comprising the following steps:

[0006] Step 1: Turn on the power and set the temperature of the blackbody module and the high and low temperature test chamber;

[0007] Step 2: After the temperature in the high and low temperature test chamber is uniform and stable, the target image after the optical axis is continuously zoomed is collected and stored in the digital image cache;

[0008] Step 3, set the temperature in the next high and low temperature test chamber, repeat the above step 2, and collect continuously zoomed target images at different temperatures;

[0009] Step 4: Image segmentation: intercept the target image with the black body part as the background from the continuously zoomed images of the target with the focal length from small to large acquired by the thermal imager at different temperatures in the high and low temperature test chamber; intercept the target image with the black body part as the background from the continuously zoomed images of the target with the focal length from large to small acquired by the thermal imager at different temperatures in the high and low temperature test chamber;

[0010] Step 5: Calculation of image clarity and servo control parameters;

[0011] Step six: retest the performance. If the retest passes, the calibration is complete. If it fails, re-collect data.

[0012] Furthermore, the image clarity is calculated using the Tenengrad gradient method; the Tenengrad gradient method uses the Sobel operator to calculate the gradients in the horizontal and vertical directions respectively. The higher the gradient value in the same scene, the clearer the image; its calculation formula is:

[0013] and G x (x,y),G y (x, y) is the gradient of the image pixel in the horizontal and vertical directions, and its calculation formula is:

[0014] G x (x,y)=f(x,y)*g x , G y (x,y)=f(x,y)*g y , f(x,y) is the gray value of the image at the (x,y) coordinate,

[0015]

[0016] The above-mentioned technical scheme of the present invention has the following beneficial technical effects: the cost of setting up the system is low, and it can be put into actual production and adjustment; compared with the previous domestic calibration methods, the system can automatically adjust the high and low temperature boxes and the target temperature to realize the automatic calibration of the optical servo parameters of the thermal imager under multi-temperature conditions; there is a quantitative calibration for the positioning of the optical axis compensation lens group in different temperature zones, which improves the focusing accuracy and ensures the clarity of the thermal imager image; the entire optical servo calibration process is simple for personnel to detect and operate, and the calibration of the production line can be completed after simple training; the image quality of the product and the performance of the whole machine are guaranteed. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural schematic diagram of an automatic calibration system for optical servo parameters of a continuous zoom thermal imager;

[0018] Figure 2 It is a flow chart of an automatic calibration method for optical servo parameters of a continuous zoom thermal imager;

[0019] Figure 3 It is a curve diagram showing the relationship between -40℃ clarity and compensation lens group positioning;

[0020] Figure 4 This is a curve diagram showing the relationship between 5°C clarity and compensation lens group positioning;

[0021] Figure 5 This is a curve chart showing the relationship between 40°C clarity and compensation lens group positioning.

[0022] Reference numerals:

[0023] 1: Thermal imager; 2: Germanium window of high and low temperature test chamber; 3: Infrared target information; 4: Collimator; 5: High and low temperature test chamber; 6: Multi-rod fan-shaped target module with different spatial frequencies; 7: Black body module; 8: High and low temperature chamber numerical control module; 9: Communication cable; 10: Host computer; 11: Power supply; 12: Communication cable; 13: Power cable; 14: Communication cable; 15: Power cable; 16: Collect target images of thermal imager at different focal lengths at different temperatures; 17: Digital image cache; 18: Dynamic segmentation of digital image; 19: Calculate image clarity; 20: Calculate the servo numerical calibration and fitting parameter curve of the compensation mirror group in a specific temperature zone; 21: Servo parameter writing; 22: Performance retest; 23: Calibration completed. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. It should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.

[0025] like Figure 1As shown, a continuous zoom thermal imager optical servo parameter automatic calibration system is provided, which consists of a thermal imager 1, a high and low temperature test box germanium window 2, a collimator 4, a high and low temperature test box 5, a multi-rod fan-shaped target module 6 with different spatial frequencies, a black body module 7, a high and low temperature box numerical control module 8, a host computer 10 and a power supply 11; the thermal imager 1 is arranged in the high and low temperature test box 5, the high and low temperature test box germanium window 2 and the high and low temperature box numerical control module 8 are arranged on the high and low temperature test box 5, the collimator 4, the multi-rod fan-shaped target module 6 with different spatial frequencies and the black body module 7 are arranged in sequence in the direction of the box germanium window 2, the infrared target information 3 is radiated from the black body module 7 surface source, passes through the multi-rod fan-shaped target module 6 with different spatial frequencies and the collimator 4, passes through the high and low temperature test box germanium window into the high and low temperature test box and is received by the thermal imager lens; the power supply is connected to the thermal imager and the host computer through a cable; the host computer is connected to the thermal imager, the high and low temperature box numerical control module and the black body module through a cable. The multi-rod sector target module 6 with different spatial frequencies is installed in front of the black body module 7 to ensure that the black body radiates infrared light information. After passing through the inverted trapezoidal target, it passes through the collimator 4 to form parallel emission infrared target information 3, so as to facilitate the thermal imager 1 to collect image information. The high and low temperature test box 5 works at different temperature points according to the needs of the calibration, and the temperature range covers from -40 to 70°C. The host computer 1 includes an image acquisition module, a digital image cache module, a digital image dynamic segmentation module, an image transfer function Sitf calculation module, and a module for calculating the servo numerical calibration and fitting parameter curve of the compensation mirror group in a specific temperature zone; the image acquisition module is used to collect images of the thermal imager under different temperature conditions in a high and low temperature test chamber and during the continuous zooming process of the thermal imager when the black body temperature difference is a constant value; the digital image cache module is used to store the collected digital images for preprocessing; the digital image dynamic segmentation module is used to perform image segmentation; the image transfer function Sitf calculation module is used to process the segmented images and calculate the corresponding grayscale value and transfer function; the module for calculating the calibration values ​​of different focal lengths in a specific temperature zone and fitting parameter curves is used to calculate the servo control point parameters when continuous zooming obtains a clear image at each ambient temperature, and fits them into a set of smooth focusing servo control parameters; through the synergistic effect of the above modules, the image collected by the image acquisition module is used as the basic basis to jointly complete the calibration of the automatic focusing of the optical axis of the thermal imager.

[0026] The target adopts a special multi-rod fan-shaped design. Within a certain range, the spatial frequency of the target has the characteristics of continuous distribution. The target adopts this design mainly to deal with the continuous change of the focal length of the thermal imager within a certain range. If a traditional four-rod target is used, its spatial frequency is fixed. The four-rod target used for debugging when the thermal imager is in the short-focus state may not be suitable for use when the thermal imager is in the long-focus state. At this time, the spatial frequency of the target is too low. When the thermal imager compensation mirror moves within a certain range, the thermal imager's imaging is clear, and it is difficult for the staff to determine the best compensation mirror position. The use of a newly designed target can perfectly solve this problem. If the highest frequency of the target is designed as the characteristic frequency of the thermal imager, no matter how the thermal imager continuously zooms, there will always be a local target available for debugging to collect image details.

[0027] like Figure 2 As shown, a method for automatically measuring the optical servo parameters of a continuous zoom thermal imager based on the above-mentioned automatic measuring system for the optical servo parameters of a continuous zoom thermal imager is provided, comprising the following steps:

[0028] Step 1: Turn on the power and set the temperature of the blackbody module and the high and low temperature test chamber;

[0029] Step 2: After the temperature in the high and low temperature test chamber is uniform and stable, the target image after the optical axis is continuously zoomed is collected and stored in the digital image cache;

[0030] Step 3, set the temperature in the next high and low temperature test chamber, repeat the above step 2, and collect continuously zoomed target images at different temperatures;

[0031] Step 4: Image segmentation: intercept the target image with the black body part as the background from the continuously zoomed images of the target with the focal length from small to large acquired by the thermal imager at different temperatures in the high and low temperature test chamber; intercept the target image with the black body part as the background from the continuously zoomed images of the target with the focal length from large to small acquired by the thermal imager at different temperatures in the high and low temperature test chamber;

[0032] Step 5: Calculation of image clarity and servo control parameters;

[0033] Step six: retest the performance. If the retest passes, the calibration is complete. If it fails, re-collect data.

[0034] The image clarity is calculated using the Tenengrad gradient method; the Tenengrad gradient method uses the Sobel operator to calculate the gradients in the horizontal and vertical directions respectively. The higher the gradient value in the same scene, the clearer the image; its calculation formula is:

[0035] and G x (x,y),G y(x, y) is the gradient of the image pixel in the horizontal and vertical directions, and its calculation formula is:

[0036] G x (x,y)=f(x,y)*g x , G y (x,y)=f(x,y)*g y , f(x,y) is the gray value of the image at the (x,y) coordinate,

[0037]

[0038] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0039] Example 1: The optical axis servo calibration is performed on a thermal imager produced by a certain company. The blackbody temperature difference is set to 30°C. The 25-700mm focal length thermal imager is set at 700mm focal length. When the working environment temperature is -40°C, 5°C, and 40°C, 30 servo calibration points are set, the target image is collected, and the servo control parameters of the thermal imager are calculated.

[0040] The main hardware configuration of the mapping device is as follows: the host computer 10 is a computer with a Camerlink interface, and has a VCE-CLEX02 Camerlink acquisition card and a dedicated cable and Framelink Express acquisition software; the target 6 has a spatial frequency of 0.3-8c / mrad; the collimator 4 has a focal length of 2000mm and an aperture of 250mm.

[0041] The testing methods of the detection system include: image acquisition and preprocessing, image segmentation, image clarity, and calculation of servo control parameters.

[0042] The servo control parameter calibration steps include:

[0043] (1) Turn on the black body module 7 and set the temperature to 30°C, set the temperature in the high and low temperature test chamber 5 to -40°C, turn on the power supply 11, the host computer 10 and the thermal imager 1;

[0044] (2) connecting the host computer 10 to the thermal imager 1, the power supply 11, the black body module 7, the high and low temperature test chamber 5 and the numerical control module 8;

[0045] (3) The host computer 10 selects the standard temperature in the high and low temperature test box 5, and after the temperature in the high and low temperature test box is uniform and stable, the Camerlink video acquisition card of the host computer 10 is used to collect the target image after the optical axis is continuously zoomed, and the image is stored in the host memory;

[0046] (4) The high and low temperature chamber numerical control module 8 is controlled by the host computer 10, the temperature in the high and low temperature chamber 5 is selected to be 5° C., and the above step A3 is repeated to collect continuously zoomed target images at different temperatures;

[0047] (5) The high and low temperature chamber numerical control module 8 is controlled by the host computer 10, the temperature in the high and low temperature chamber 5 is selected to be 40°C, and the above step A3 is repeated to collect continuously zoomed target images at different temperatures.

[0048] (6) When the external working environment temperature of the thermal imager is -40°C, 5°C, and 40°C, infrared images collected at different working temperatures are intercepted within the range of the sector-shaped target portion with different spatial frequencies.

[0049] (7) When the operating temperature is -40℃, calculate Figure 3 As shown, the maximum value of clarity is 6980.1 at this time, and the corresponding compensation lens group position is 125795.4;

[0050] (8) When the operating temperature is 5°C, calculate Figure 4 As shown, the maximum value of clarity is 8295.7 at this time, and the corresponding compensation lens group position is 148279.8;

[0051] (9) When the operating temperature is 40°C, calculate Figure 5 As shown, the maximum clarity at this time is 7452.0, and the corresponding compensation lens group position is 166050.6.

[0052] Embodiment 2: In this embodiment, all steps and the blackbody temperature difference remain unchanged as in embodiment 1, the focal length of the thermal imager is changed to 380 mm, images are collected and the servo parameters of the optical compensation lens group are calculated.

[0053] The data of compensation lens group and clarity value when the working environment temperature is -40℃: the maximum clarity value is 12859.6, and the corresponding compensation lens group position is 148152.0;

[0054] The data of compensation lens group and clarity value when the working environment temperature is 5℃: the maximum clarity value is 18626.9, and the corresponding compensation lens group position is 154302.0;

[0055] The data of compensation lens group and clarity value when the working environment temperature is 40℃: the maximum clarity value is 20715.8, and the corresponding compensation lens group position is 106867.0.

[0056] The specific embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention.

[0057] It should be understood that the above specific embodiments of the present invention are only used to illustrate or explain the principles of the present invention, and do not constitute a limitation of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc. made without departing from the spirit and scope of the present invention should be included in the protection scope of the present invention. In addition, the appended claims of the present invention are intended to cover all changes and modifications that fall within the scope and boundaries of the appended claims, or the equivalent forms of such scope and boundaries.

Claims

1. An automatic measurement system for optical servo parameters of a continuous zoom thermal imager, characterized in that: It consists of a thermal imager, a high and low temperature test box germanium window, a collimator, a high and low temperature test box, a multi-rod fan-shaped target module with different spatial frequencies, a black body module, a high and low temperature box numerical control module, a host computer and a power supply; the thermal imager is arranged in the high and low temperature test box, the high and low temperature test box is provided with a high and low temperature test box germanium window and a high and low temperature box numerical control module, and the collimator, the multi-rod fan-shaped target module with different spatial frequencies and a black body module are arranged in sequence in the direction of the box germanium window; the power supply is connected to the thermal imager and the host computer through a cable; the host computer is connected to the thermal imager, the high and low temperature box numerical control module and the black body module through a cable.

2. A method for automatically measuring optical servo parameters of a continuous zoom thermal imager based on the automatic measuring system for optical servo parameters of a continuous zoom thermal imager according to claim 1, characterized in that: The following steps are involved: Step 1: Turn on the power and set the temperature of the blackbody module and the high and low temperature test chamber; Step 2: After the temperature in the high and low temperature test chamber is uniform and stable, the target image after the optical axis is continuously zoomed is collected and stored in the digital image cache; Step 3, set the temperature in the next high and low temperature test chamber, repeat the above step 2, and collect continuously zoomed target images at different temperatures; Step 4: Image segmentation: intercept the target image with the black body part as the background from the continuously zoomed images of the target with the focal length from small to large acquired by the thermal imager at different temperatures in the high and low temperature test chamber; intercept the target image with the black body part as the background from the continuously zoomed images of the target with the focal length from large to small acquired by the thermal imager at different temperatures in the high and low temperature test chamber; Step 5: Calculation of image clarity and servo control parameters; Step six: retest the performance. If the retest passes, the calibration is complete. If it fails, re-collect data.

3. The method for automatically measuring optical servo parameters of a continuous zoom thermal imager according to claim 2, characterized in that: The image clarity is calculated using the Tenengrad gradient method; the Tenengrad gradient method uses the Sobel operator to calculate the gradients in the horizontal and vertical directions respectively. The higher the gradient value in the same scene, the clearer the image; its calculation formula is: and G x (x,y),G y (x, y) is the gradient of the image pixel in the horizontal and vertical directions, and its calculation formula is: G x (x,y)=f(x,y)*g x , G y (x,y)=f(x,y)*g y , f(x,y) is the gray value of the image at the (x,y) coordinate,

Images