Automatic focal length compensation method for infrared searching and tracking equipment

Abstract

The invention relates to an automatic focal length compensation method for infrared searching and tracking equipment. The method comprises the following steps: acquiring lens temperature data and focusing mechanism position sensor data at different temperature points; fitting a focusing curve according to the collected data; focusing curve parameters are solidified; when the infrared searching and tracking device works, focusing control is carried out according to the set focusing curve parameters, and focal length compensation is achieved. The focusing precision and the imaging quality of the infrared searching and tracking equipment in a complex temperature environment can be remarkably improved, the adaptability and the reliability of the equipment are improved, human intervention is not needed, and the method is particularly suitable for occasions requiring high precision and high reliability in a dynamic environment.

Description

Technical Field

[0001] The invention relates to the technical field of optical systems of infrared search and tracking equipment, and relates to an automatic focal length compensation method for infrared search and tracking equipment. Background Art

[0002] The optical system of existing infrared search and tracking equipment is easily affected by changes in ambient temperature, resulting in focal length offset, which in turn affects the image quality. Traditional focusing methods mostly rely on manual adjustment, which has the disadvantages of low adjustment accuracy, slow response speed, and high operator proficiency requirements. In addition, some infrared search and tracking equipment adopts athermal lens design or focusing solutions based on image feedback. The athermal lens solution has strict requirements on material selection, increases equipment cost, and is difficult to maintain stable imaging performance over a wide temperature range; while the focusing method based on image feedback is complex in calculation, has high requirements on the scene, and is easily disturbed by changes in the environmental background, making it difficult to achieve the expected focusing effect in practical applications. Therefore, there is an urgent need for an automatic focal length compensation technology based on temperature changes that can respond to focal length offsets caused by temperature fluctuations in real time and accurately, thereby effectively improving the imaging quality and system stability of infrared search and tracking equipment. Summary of the invention

[0003] The purpose of the present invention is to provide an automatic focal length compensation method for infrared search and tracking equipment, so as to solve the problem of focal length deviation caused by temperature influence of infrared search and tracking equipment in the prior art.

[0004] To achieve the above object, the technical solution of the present invention is:

[0005] An automatic focal length compensation method for an infrared search and tracking device, the infrared search and tracking device comprises an infrared lens, an infrared detector, a focus mechanism, a servo turntable, a control circuit and matching control software; the focus mechanism comprises a focus motor and a position sensor; a temperature sensor is arranged on the infrared lens;

[0006] The steps of this method are,

[0007] Step 1, collecting lens temperature data and focus mechanism position sensor data at different temperature points respectively;

[0008] Step 2: fitting a focus curve according to the collected lens temperature data and focus mechanism position sensor data;

[0009] Step 3, solidifying the parameters of the focus curve obtained in step 2;

[0010] Step 4: Monitor the temperature change of the infrared search and tracking device in real time when it is working, and perform focus control according to the set focus curve parameters.

[0011] Step 1: The method for collecting data at different temperature points is to place the infrared search and tracking device in a high and low temperature environmental test chamber, and adjust the temperature of the high and low temperature environmental test chamber to make the infrared search and tracking device work at different ambient temperatures.

[0012] Step 1: When collecting data at different working temperature points, it is necessary to first aim the infrared search and tracking device at the infrared target and focus until the imaging effect is optimal, and then collect the temperature data and the focus mechanism position sensor data at this moment.

[0013] The lens temperature data collected in step 1 comes from a temperature sensor installed on the lens, and the temperature sensor is a temperature sensor with an accuracy within ±0.1°C.

[0014] In step 1, the temperature points for collecting data are selected between -50°C and 70°C and are selected at fixed intervals.

[0015] The focusing curve in step 2 is fitted by at least three experimental data, and a polynomial or piecewise function is used to represent the corresponding relationship between the temperature and the focusing position of the focusing mechanism.

[0016] The parameter solidification of the focus curve in step three is to store the key parameters of the focus curve obtained by fitting in the solidified storage medium of the device.

[0017] The key parameters of the focus curve include at least the temperature range, the fitting coefficient of the curve and the focal length compensation value.

[0018] The infrared search and tracking device in step 4 performs focus control according to the set focus curve parameters when working, which means that the control software running in the infrared search and tracking device calculates the focal position through the focus curve and the current temperature value, and sets a focus deviation threshold at the same time; when the difference between the calculated focal position and the current focal position exceeds the threshold, the control software calculates the focal position according to the current temperature for focus control.

[0019] Focus control refers to adjusting the position distance between the infrared lens and the infrared detector.

[0020] The advantages of the present invention are: 1. It has the advantages of low cost, small calculation amount, easy implementation and high focusing accuracy; 2. It can realize automatic focal length compensation control according to temperature changes; 3. It can ensure that the infrared search and tracking equipment maintains clear focus in different temperature environments, improve the adaptability and reliability of the equipment, and does not require human intervention and maintenance. It is especially suitable for dynamic environments that require high precision and high reliability, such as infrared imaging, precision measurement and medical imaging; 4. It significantly improves the performance stability of infrared search and tracking equipment in complex environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1It is a schematic diagram of the process of the present invention.

[0022] Figure 2 It is a schematic diagram of a scenario for collecting lens temperature data and focus mechanism position sensor data in the present invention.

[0023] Figure 3 It is a structural schematic diagram of the infrared search and tracking device of the present invention. DETAILED DESCRIPTION

[0024] The present invention is further described below in conjunction with the accompanying drawings, which are only used for exemplary description and cannot be understood as limiting the present invention.

[0025] In order to more concisely describe the present embodiment, some parts known to those skilled in the art but not related to the main content of the present invention are omitted in the drawings or descriptions. In addition, for the convenience of description, some parts in the drawings are omitted, enlarged or reduced, but they do not represent the size or entire structure of the actual product.

[0026] The invention discloses an automatic focal length compensation method for infrared search and tracking equipment. Figure 3 As shown, the infrared search and tracking device includes an infrared lens, an infrared detector, a focusing mechanism, a servo turntable, a control circuit and supporting control software; the focusing mechanism includes a focusing motor and a position sensor; preferably, the focusing motor can be a servo motor or a stepper motor, etc., and the position sensor can be an absolute encoder, a linear displacement sensor or other sensors that can be used to measure position offset.

[0027] Among them, the accuracy of the position sensor needs to be selected according to the actual optical design. Generally, the optical accuracy of infrared search and tracking equipment is required to be controlled within 0.1mm. A temperature sensor is set on the infrared lens;

[0028] like Figure 1 As shown, the method steps include:

[0029] Step 1: Collect lens temperature data and focus mechanism position sensor data at different temperature points.

[0030] Among them, the method of collecting data at different temperature points is to place the infrared search and tracking device in a high and low temperature environmental test box, and adjust the temperature of the high and low temperature environmental test box to make the infrared search and tracking device work at different ambient temperatures.

[0031] Furthermore, when collecting data at different operating temperature points, it is necessary to first aim the infrared search and tracking device at the infrared target and focus until the imaging effect is optimal, and then collect the temperature data and the focus mechanism position sensor data at this moment.

[0032] The collected lens temperature data is derived from a temperature sensor installed on the lens. Preferably, the temperature sensor is a temperature sensor with an accuracy within ±0.1° C. to ensure the accuracy of the temperature data.

[0033] To ensure the reliability of the collected temperature data, the temperature sensor data needs to be collected multiple times and then filtered. Similarly, the focus mechanism position sensor data also needs to be collected multiple times and then filtered.

[0034] The selection of different temperature points is determined according to the working environment temperature that the infrared search and tracking equipment needs to adapt to, and is selected at fixed intervals within the working environment temperature range; the temperature adjustment range of the high and low temperature environment test chamber needs to cover the working range required by the infrared search and tracking equipment. For example, the general infrared search and tracking equipment requires a working range between -50℃ and 70℃. The selection of temperature points for data collection is selected at fixed intervals between -50℃ and 70℃.

[0035] like Figure 2 As shown in the figure, when collecting data, the infrared search and tracking device works in a high and low temperature environment test chamber. The infrared search and tracking device is connected to an external test computer through a cable, and the imaging effect of the infrared search and tracking device is viewed through the test computer. The temperature of the high and low temperature environment test chamber can be adjusted to make the infrared search and tracking device work at different ambient temperatures.

[0036] When collecting data at different operating temperature points, it is necessary to first aim the infrared search and tracking device at the infrared target and focus to the best imaging effect, and then collect the temperature data and focus mechanism position sensor data at that time. The infrared target can be a cross or strip grid target.

[0037] Step 2: fitting a focus curve according to the collected lens temperature data and focus mechanism position sensor data;

[0038] The focusing curve is fitted by at least three experimental data, and a polynomial or piecewise function is used to represent the corresponding relationship between the temperature and the focusing position of the focusing mechanism.

[0039] In the case where the focus position changes smoothly with temperature, the relationship between the temperature T and the focus position F(T) can be expressed by an n-order polynomial. The following example uses a cubic polynomial fitting;

[0040] F(T)=a3T 3 +a2T 2 +a1T+a0;

[0041] Where T is temperature (unit: °C), F(T) is focus position (unit: 0.01 mm or encoder position), a3, a2, a1, a0 are polynomial coefficients.

[0042] When the relationship between the focus position and temperature presents nonlinear and discontinuous changes, a piecewise function can be used to describe the focus position in different temperature ranges.

[0043]

[0044] Among them: a n ,a n-1 ,...,a0,b n ,b n-1 ,...,b0, are piecewise function coefficients, each interval (T i ,T i+1 ) adopts different linear or nonlinear models, which is suitable for situations where the focal length changes greatly or suddenly with temperature, and can meet the needs of complex scenes and occasions with high precision requirements.

[0045] In some embodiments, 3 to 5 sets of data can be collected at each temperature point, and the correspondence between temperature and the focus position of the focus mechanism is represented by a polynomial or piecewise function depending on the actual data results. For example, if the data is linearly distributed between -50°C and 70°C, a polynomial function can be used to represent it. If the distribution pattern of the data in a certain temperature range is significantly different from that in other temperature ranges, a piecewise function can be selected for representation.

[0046] Step three, solidify the parameters of the focus curve obtained in step two.

[0047] The parameter solidification of the focus curve is to store the key parameters of the fitted focus curve in the solidified storage medium of the device. The key parameters of the focus curve include at least the temperature range, the curve fitting coefficient and the focal length compensation value.

[0048] Step 4: monitor the temperature change of the infrared search and tracking device in real time when it is working, and perform focus control according to the set focus curve parameters.

[0049] Specifically, the infrared search and tracking device performs focus control according to the set focus curve parameters when working, which means that the control software running in the infrared search and tracking device calculates the focal position through the focus curve and the current temperature value, and sets a focus deviation threshold at the same time; when the difference between the calculated focal position and the current focal position exceeds the threshold, the control software calculates the focal position according to the current temperature to perform focus control to achieve focal compensation, so that the focal length matches the ambient temperature, thereby ensuring clear imaging. The selection of the threshold needs to be combined with the results of the optical design of the infrared search and tracking device. For example, in some optical designs, a temperature change of more than 10°C will cause a focus offset, affecting the imaging effect, and the threshold setting should be less than 10°C.

[0050] Focus control refers to adjusting the position distance between the infrared lens and the infrared detector.

[0051] The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of the present invention. That is, any equivalent changes and modifications made according to the content of the patent application scope of the present invention should be within the technical scope of the present invention.

Claims

1. An automatic focus compensation method for an infrared search and tracking device, the infrared search and tracking device comprising an infrared lens, an infrared detector, a focus mechanism, a servo turntable, a control circuit and supporting control software; the focus mechanism comprises a focus motor and a position sensor; a temperature sensor is arranged on the infrared lens; Features: The steps of this method are, Step 1, collecting lens temperature data and focus mechanism position sensor data at different temperature points respectively; Step 2, fitting a focus curve according to the collected lens temperature data and focus mechanism position sensor data; Step 3, solidifying the parameters of the focus curve obtained in step 2; Step 4: monitor the temperature change of the infrared search and tracking device in real time when it is working, and perform focus control according to the set focus curve parameters.

2. The automatic focus compensation method for infrared search and tracking equipment according to claim 1, characterized in that: Step 1: The method for collecting data at different temperature points is to place the infrared search and tracking device in a high and low temperature environmental test chamber, and adjust the temperature of the high and low temperature environmental test chamber to make the infrared search and tracking device work at different ambient temperatures.

3. The automatic focus compensation method of infrared search and tracking equipment according to claim 2, characterized in that: Step 1: When collecting data at different working temperature points, it is necessary to first aim the infrared search and tracking device at the infrared target and focus until the imaging effect is optimal, and then collect the temperature data and the focus mechanism position sensor data at this moment.

4. The automatic focus compensation method of infrared search and tracking equipment according to claim 3, characterized in that: The lens temperature data collected in step 1 comes from a temperature sensor installed on the lens, and the temperature sensor is a temperature sensor with an accuracy within ±0.1°C.

5. The automatic focus compensation method of infrared search and tracking equipment according to claim 4, characterized in that: In step 1, the temperature points for collecting data are selected between -50°C and 70°C and are selected at fixed intervals.

6. The automatic focus compensation method of infrared search and tracking equipment according to claim 1, characterized in that: The focusing curve in step 2 is fitted by at least three experimental data, and a polynomial or piecewise function is used to represent the corresponding relationship between the temperature and the focusing position of the focusing mechanism.

7. The automatic focus compensation method of infrared search and tracking equipment according to claim 1, characterized in that: The parameter solidification of the focus curve in step three is to store the key parameters of the focus curve obtained by fitting in the solidified storage medium of the device.

8. The automatic focus compensation method of infrared search and tracking equipment according to claim 7, characterized in that: The key parameters of the focus curve include at least the temperature range, the fitting coefficient of the curve and the focal length compensation value.

9. The automatic focus compensation method of infrared search and tracking equipment according to claim 1, characterized in that: The infrared search and tracking device in step 4 performs focus control according to the set focus curve parameters when working, which means that the control software running in the infrared search and tracking device calculates the focal position through the focus curve and the current temperature value, and sets a focus deviation threshold at the same time; when the difference between the calculated focal position and the current focal position exceeds the threshold, the control software calculates the focal position according to the current temperature for focus control.

10. The automatic focus compensation method of infrared search and tracking equipment according to claim 9, characterized in that: Focus control refers to adjusting the position distance between the infrared lens and the infrared detector.

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