An oversampling control system for airborne multi-field / continuous zoom thermal imager

Abstract

The present invention discloses an airborne multi-field / continuous zoom thermal imager oversampling control system, comprising an error compensation module, a quick-reflection mirror control module and a detector control module; wherein the error compensation module is connected to the signal and image processing component of the multi-field / continuous zoom thermal imager to obtain temperature, image sub-pixel displacement and field / focal length information; the detector control module is connected to the infrared detector assembly to drive the infrared detector to perform integral sampling; the quick-reflection mirror control module is connected to the airborne servo turntable and the two-dimensional quick-reflection mirror, the two-dimensional quick-reflection mirror is deployed between the thermal imager telescopic optical system and the imaging optical system, and the optical path is driven to move by the two-dimensional quick-reflection mirror. The present invention realizes the oversampling of the target image by the multi-field / continuous zoom thermal imager installed under the airborne platform, and improves the resolvable spatial frequency of the multi-field / continuous zoom thermal imager.

Description

Technical Field

[0001] The invention belongs to the technical field of thermal imager imaging, and in particular relates to an oversampling control system for an airborne multi-field / continuous zoom thermal imager. Background Art

[0002] Infrared imaging technology is one of the high technologies that countries are vigorously developing today, and it is widely used in both civilian and military fields. The resolvable spatial frequency of infrared images is one of the important indicators of infrared images, which affects the quality of infrared images and the recognition distance of targets. The resolvable spatial frequency of infrared thermal imagers is restricted by factors such as the spacing and filling factor of infrared detector detection photosensitive elements. Limited by the diffraction limit of the optical system of infrared equipment, the spacing of infrared detector detection photosensitive elements that affects the resolution of infrared imaging cannot and does not need to be infinitely reduced, so the resolvable spatial frequency of infrared images cannot be improved only by increasing the density of infrared detector detection photosensitive elements. In addition, the materials of infrared detection semiconductors and their complex preparation and production processes make it difficult for the focal plane detector filling factor to reach 100%, thereby affecting the spatial resolution index of infrared images. These two factors seriously restrict the quality of infrared images. Summary of the invention

[0003] The purpose of the present invention is to provide an airborne multi-field-of-view / continuous-zoom thermal imager oversampling control system to solve the problem of too low resolvable spatial frequency of the airborne multi-field-of-view / continuous-zoom thermal imager due to too large a spacing between photosensitive elements of the infrared detector and too small a filling factor, thereby improving image quality.

[0004] To achieve the above purpose, the technical solution provided by the present invention is as follows:

[0005] An airborne multi-field / continuous zoom thermal imager oversampling control system, comprising an error compensation module, a fast reflection mirror control module and a detector control module;

[0006] The error compensation module is connected to the multi-field / continuous zoom thermal imager signal and the image processing component for calculating and storing the corrected fast-reflection mirror control value;

[0007] The fast-reflection mirror control module is connected to the airborne servo turntable and the two-dimensional fast-reflection mirror, and generates an analog signal to control the movement of the two-dimensional fast-reflection mirror by solving the motion residual information of the airborne servo turntable and the fast-reflection mirror control value; the two-dimensional fast-reflection mirror is deployed between the telescopic optical system and the imaging optical system of the thermal imager, and the target optical path generates sub-pixel movement on the detector target surface through the movement of the two-dimensional fast-reflection mirror. The two-dimensional fast-reflection mirror includes but is not limited to electromagnetic, voice coil, and piezoelectric platforms;

[0008] The detector control module controls the integral sampling process of the infrared detector component by analyzing the position feedback information of the two-dimensional fast reflection mirror to oversample the target.

[0009] Furthermore, the error compensation module receives the temperature, image sub-pixel movement, and field of view / focal length information from the thermal imager signal and the image processing component, calculates the temperature and quick-reflex mirror control value curves under different fields of view / focal lengths based on this information, and stores the temperature and quick-reflex mirror control value curves through a storage circuit.

[0010] Furthermore, the error compensation module corrects the processing and assembly errors of the thermal imager in engineering production, corrects the nonlinearity and temperature drift errors of the displacement sensor in the two-dimensional fast mirror, and corrects the field of view / focal length value changes caused by the deformation of the thermal imager optical parts due to the change in ambient temperature; after correction, a high-precision temperature and fast mirror control value curve is obtained, and the fast mirror control value under the current field of view / focal length and temperature is obtained by calculation; the following steps are included:

[0011] S1. The calibration system includes a high and low temperature box with an infrared window, a collimator, a black body and four horizontal and vertical targets;

[0012] S2. Place the thermal imager in a temperature chamber and observe the target in front of the black body through the infrared window and collimator.

[0013] S3, focusing the temperature box to a corresponding temperature;

[0014] S4. Operate the thermal imager to a certain field of view / focal length and adjust the focus until the target is clear;

[0015] S5, collecting target images, and calculating pixel displacement between different image frames by using the extended phase correlation method through the thermal imager signal and the image processing component;

[0016] S6, controlling the movement of the two-dimensional fast reflex mirror so that the image pixel displacement is the oversampling design value, and recording the field of view / focal length value, thermal imager temperature value and two-dimensional fast reflex mirror control value at this time;

[0017] S7, repeat steps S4-S6 to traverse all fields of view / focal lengths of the thermal imager;

[0018] S8, repeat steps S3-S7 to traverse all operating temperatures of the thermal imager;

[0019] S9, calculating the temperature and fast mirror control value curves under different fields of view / focal lengths;

[0020] S10, storing the temperature and fast mirror control value curves under different fields of view / focal lengths in a storage circuit;

[0021] S11, when the thermal imager is working, the error compensation module obtains the current field of view / focal length value and temperature, and retrieves the temperature and fast mirror control value curve in the storage circuit to calculate the two-dimensional fast mirror control value.

[0022] Furthermore, the fast mirror control module is based on an FPGA processor and adopts a high-precision DA conversion circuit to generate an analog quantity as a two-dimensional fast mirror driving signal to meet the requirements of high-speed and high-precision response of the two-dimensional fast mirror; the FPGA processor pins are protected and isolated as a communication interface connected to the airborne servo turntable to obtain the angle residual value after the airborne servo turntable is stabilized; the airborne servo turntable adopts a multi-stage stable structure. In order to improve the stability of the thermal imager during the oversampling process, the airborne servo turntable transmits its own stabilized angle residual value to the fast mirror control module through the communication interface; the communication interface adopts a clock line and a signal line communication method, and the clock line occupies 1 FP GA pin, the number of signal lines is determined by negotiation with the airborne servo turntable; when one data line is used, the data transmission rate is not less than 2Mb / s, and if multiple data lines are used, the transmission rate will be greatly improved; the residual value is 16-bit data, and its update rate is higher than 100KHz, which can meet the requirements for the driving speed of the two-dimensional fast reflex mirror; the FPGA processor calculates the driving amount of the two-dimensional fast reflex mirror according to the fast reflex mirror control value of the error compensation module and the residual value of the airborne servo turntable, and after high-precision AD conversion circuit, generates analog driving amount to control the movement of the two-dimensional fast reflex mirror; in order to improve the response speed of the two-dimensional fast reflex mirror, the maximum value of the driving amount is limited but not smoothed;

[0023] Furthermore, the detector control module is connected to the two-dimensional fast reflex mirror position feedback circuit, performs high-precision AD sampling on the analog quantity of the two-dimensional fast reflex mirror position signal, sets the position signal threshold, and when the position signal reaches the threshold, instructs the two-dimensional fast reflex mirror to move into position, generates a drive level signal, and drives the detector to start integral sampling; since the timing of the movement of the two-dimensional fast reflex mirror in two directions can be known in advance, the detector control module only needs to perform AD sampling on the two-dimensional fast reflex mirror position signal in one direction of movement, and then generates the drive level signal in a timing manner within a scanning cycle, thereby reducing the scale of the AD sampling circuit.

[0024] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0025] 1. The present invention is applicable to airborne multi-field / continuous zoom thermal imagers, realizing oversampling control of thermal imagers and improving the resolvable spatial frequency of thermal imagers;

[0026] 2. The control error compensation method is used to compensate for the oversampling control error caused by the nonlinearity of the two-dimensional fast mirror position sensor and the deformation of the thermal imager optical parts due to processing, assembly, and changes in ambient temperature in the production of thermal imagers;

[0027] 3. The two-dimensional reflector of the present invention has fast control speed and high precision, making the oversampling process of the thermal imager stable and reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a principle block diagram of the present invention;

[0029] Figure 2 is a diagram of the deployment position of a two-dimensional fast reflection mirror in a thermal imager in an embodiment of the present invention;

[0030] Figure 3 is a diagram of a driving level signal generated by a detector control module in an embodiment of the present invention;

[0031] Figure 4 is a normal sampling image in an embodiment of the present invention;

[0032] Figure 5 is an oversampled image in the embodiment of the present invention.

[0033] In the figure: 1- Two-dimensional fast mirror. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific implementation methods described herein are used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various implementation methods of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0035] The airborne multi-field / continuous zoom thermal imager oversampling control system of the embodiment of the present invention is as follows: Figure 1 As shown, it includes an error compensation module, a fast mirror control module and a detector control module; the error compensation module is connected to the multi-field / continuous zoom thermal imager signal and the image processing component to calculate and store the corrected fast mirror control value; the fast mirror control module generates an analog signal to control the two-dimensional fast mirror to perform N×N scanning movement by solving the motion residual information of the airborne servo turntable and the fast mirror control value; the two-dimensional fast mirror 1 is deployed between the thermal imager telescopic optical system and the imaging optical system, as shown Figure 2 As shown, the target light path generates a 1 / N pixel movement on the detector target surface by moving a two-dimensional fast mirror, and the two-dimensional fast mirror includes but is not limited to electromagnetic, voice coil, and piezoelectric platforms; the detector control module controls the integral sampling process of the infrared detector component by analyzing the position feedback information of the two-dimensional fast mirror, and oversamples the target.

[0036] In this embodiment, the error compensation module receives the temperature, image sub-pixel movement, and field of view / focal length information sent by the thermal imager signal and the image processing component, calculates the temperature and fast mirror control value curves under different fields of view / focal lengths based on this information, and stores the temperature and fast mirror control value curves through a storage circuit.

[0037] The error compensation module corrects the processing and assembly errors of the thermal imager in engineering production, corrects the nonlinearity and temperature drift errors of the displacement sensor in the two-dimensional fast mirror, and corrects the field of view / focal length value changes caused by the deformation of the thermal imager optical parts due to changes in ambient temperature. After correction, a high-precision temperature and fast mirror control value curve is obtained. The curve takes temperature as the horizontal coordinate and the fast mirror control value as the vertical coordinate. The fast mirror control value under the current field of view / focal length and temperature is obtained by calculation, including the following steps:

[0038] S1. The calibration system includes a high and low temperature box with an infrared window, a collimator, a black body and four horizontal and vertical targets;

[0039] S2. Place the thermal imager in a temperature chamber and observe the target in front of the black body through the infrared window and collimator.

[0040] S3, focusing the temperature box to a corresponding temperature;

[0041] S4. Operate the thermal imager to a certain field of view / focal length and adjust the focus until the target is clear;

[0042] S5, collecting target images, and calculating pixel displacement between different image frames by using the extended phase correlation method through the thermal imager signal and the image processing component;

[0043] S6, controlling the movement of the two-dimensional fast reflex mirror so that the image pixel displacement is the oversampling design value, and recording the field of view / focal length value, thermal imager temperature value and two-dimensional fast reflex mirror control value at this time;

[0044] S7, repeat steps S4-S6 to traverse all fields of view / focal lengths of the thermal imager;

[0045] S8, repeat steps S3-S7 to traverse all operating temperatures of the thermal imager;

[0046] S9, calculating the temperature and fast mirror control value curves under different fields of view / focal lengths;

[0047] S10, storing the temperature and fast mirror control value curves under different fields of view / focal lengths in a storage circuit;

[0048] S11, when the thermal imager is working, the error compensation module obtains the current field of view / focal length value and temperature, and retrieves the temperature and fast mirror control value curve in the storage circuit to calculate the two-dimensional fast mirror control value.

[0049] The fast mirror control module is based on an FPGA processor and uses a high-precision DA conversion circuit to generate analog quantities as two-dimensional fast mirror drive signals to meet the requirements of high-speed and high-precision response of the two-dimensional fast mirror. The FPGA processor has high-speed data transmission capabilities, and its pins are directly connected to the airborne servo turntable as a communication interface after protection and isolation to obtain the angle residual value after the airborne servo turntable is stabilized. The airborne servo turntable adopts a multi-level stable structure. In order to improve the stability of the thermal imager during the oversampling process, the airborne servo turntable transmits its own stabilized angle residual value to the fast mirror control module through the communication interface. The communication interface uses a clock line and a signal line to communicate, and the clock line occupies 1 FPGA pin, the number of signal lines is determined through negotiation with the airborne servo turntable; when 1 data line is used, the data transmission rate is not less than 2Mb / s, and the transmission rate will be greatly improved if multiple data lines are used; the residual value is 16-bit data, and its update rate is higher than 100KHz, which can meet the requirements for the driving speed of the two-dimensional fast reflex mirror; the FPGA processor superimposes the fast reflex mirror control value of the error compensation module and the residual value of the airborne servo turntable to obtain the driving amount of the two-dimensional fast reflex mirror, and after a high-precision AD conversion circuit, an analog driving amount is generated to control the movement of the two-dimensional fast reflex mirror; in order to improve the response speed of the two-dimensional fast reflex mirror, the maximum value of the driving amount is limited but not smoothed.

[0050] The detector control module is connected to the two-dimensional fast mirror position feedback circuit, performs high-precision AD sampling on the analog quantity of the two-dimensional fast mirror position signal, sets the position signal threshold, and when the position signal reaches the threshold, it instructs the two-dimensional fast mirror to move into place and generates a driving level signal, such as Figure 3 As shown, the detector is driven to start integration sampling. After the sampled image passes through the thermal imager signal and image processing components, the resolvable spatial frequency of the thermal imager is effectively improved, as shown in Figure 4 and Figure 5 As shown; since the timing of the movement of the two-dimensional fast mirror in two directions can be known in advance, the detector control module only needs to perform AD sampling on the position signal of the two-dimensional fast mirror in one movement direction, and then generate a driving level signal in a timing manner within a scanning cycle, thereby reducing the scale of the AD sampling circuit.

[0051] In summary, the present invention provides an airborne multi-field / continuous zoom thermal imager oversampling control system, including an error compensation module, a fast reflex mirror control module and a detector control module, each module is integrated in the multi-field / continuous zoom thermal imager; wherein the error compensation module is connected to the signal and image processing component of the multi-field / continuous zoom thermal imager to obtain temperature, image sub-pixel displacement and field of view / focal length information; the detector control module is connected to the infrared detector assembly to drive the infrared detector for integral sampling; the fast reflex mirror control module is connected to the airborne servo turntable and the two-dimensional fast reflex mirror, the two-dimensional fast reflex mirror is deployed between the thermal imager telescopic optical system and the imaging optical system, and the optical path is driven to move by the two-dimensional fast reflex mirror, and the two-dimensional fast reflex mirror includes but is not limited to electromagnetic, voice coil, and piezoelectric platforms. The present invention realizes the oversampling of the target image by the multi-field / continuous zoom thermal imager installed under the airborne platform, and improves the resolvable spatial frequency of the multi-field / continuous zoom thermal imager.

[0052] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. An airborne multi-field / continuous zoom thermal imager oversampling control system, characterized in that: It includes an error compensation module, a fast reflection mirror control module and a detector control module; The error compensation module is connected to the multi-field / continuous zoom thermal imager signal and the image processing component to calculate and store the corrected fast-reflection mirror control value; The fast-reflection mirror control module is connected to the airborne servo turntable and the two-dimensional fast-reflection mirror, and generates an analog signal to control the movement of the two-dimensional fast-reflection mirror by solving the motion residual information of the airborne servo turntable and the control value of the fast-reflection mirror; the two-dimensional fast-reflection mirror is deployed between the telescopic optical system and the imaging optical system of the thermal imager, and the target optical path generates sub-pixel movement on the detector target surface through the movement of the two-dimensional fast-reflection mirror; The detector control module controls the integral sampling process of the infrared detector component by analyzing the position feedback information of the two-dimensional fast reflection mirror to oversample the target.

2. The airborne multi-field / continuous zoom thermal imager oversampling control system according to claim 1, characterized in that: Two-dimensional fast mirrors include electromagnetic, voice coil, and piezoelectric platforms.

3. The airborne multi-field / continuous zoom thermal imager oversampling control system according to claim 1, characterized in that: The error compensation module receives the temperature, image sub-pixel movement, and field of view / focal length information from the thermal imager signal and the image processing component, calculates the temperature and fast mirror control value curves under different fields of view / focal lengths based on this information, and stores the temperature and fast mirror control value curves through a storage circuit.

4. The airborne multi-field / continuous zoom thermal imager oversampling control system according to claim 1, characterized in that: The error compensation module corrects the processing and assembly errors of the thermal imager in engineering production, corrects the nonlinearity and temperature drift errors of the displacement sensor in the two-dimensional fast reflex mirror, and corrects the field of view / focal length value changes caused by the deformation of the thermal imager optical parts due to changes in ambient temperature. After correction, a high-precision temperature and fast reflex mirror control value curve is obtained. The curve takes temperature as the horizontal coordinate and the fast reflex mirror control value as the vertical coordinate. The fast reflex mirror control value under the current field of view / focal length and temperature is obtained by calculation.

5. The airborne multi-field / continuous zoom thermal imager oversampling control system according to claim 4, characterized in that: The calculation steps of the fast mirror control value are as follows: S1. The calibration system includes a high and low temperature box with an infrared window, a collimator, a black body and four horizontal and vertical targets; S2. Place the thermal imager in a temperature chamber and observe the target in front of the black body through the infrared window and collimator. S3, focusing the temperature box to a corresponding temperature; S4. Operate the thermal imager to a certain field of view / focal length and adjust the focus until the target is clear; S5, collecting target images, and calculating pixel displacement between different image frames by using the extended phase correlation method through the thermal imager signal and the image processing component; S6, controlling the movement of the two-dimensional fast reflex mirror so that the image pixel displacement is the oversampling design value, and recording the field of view / focal length value, thermal imager temperature value and two-dimensional fast reflex mirror control value at this time; S7, repeat steps S4-S6 to traverse all fields of view / focal lengths of the thermal imager; S8, repeat steps S3-S7 to traverse all operating temperatures of the thermal imager; S9, calculating the temperature and fast mirror control value curves under different fields of view / focal lengths; S10, storing the temperature and fast mirror control value curves under different fields of view / focal lengths in a storage circuit; S11, when the thermal imager is working, the error compensation module obtains the current field of view / focal length value and temperature, and retrieves the temperature and fast mirror control value curve in the storage circuit to calculate the two-dimensional fast mirror control value.

6. The airborne multi-field / continuous zoom thermal imager oversampling control system according to claim 1, characterized in that: The fast mirror control module is based on an FPGA processor and uses a high-precision DA conversion circuit to generate analog quantities as two-dimensional fast mirror drive signals to meet the requirements of high-speed and high-precision response of the two-dimensional fast mirror; the FPGA processor pins are protected and isolated as a communication interface to connect to the airborne servo turntable to obtain the angle residual value after the airborne servo turntable is stabilized; the airborne servo turntable adopts a multi-level stable structure. In order to improve the stability of the thermal imager during the oversampling process, the airborne servo turntable transmits its own angle residual value after stabilization to the fast mirror control module through the communication interface; The communication interface adopts the communication mode of clock line and signal line. The clock line occupies one FPGA pin, and the number of signal lines is determined by negotiation with the airborne servo turntable. When one data line is used, the data transmission rate is not less than 2Mb / s. If multiple data lines are used, the transmission rate will be greatly improved. The residual value is 16-bit data, and its update rate is higher than 100KHz, which meets the requirements of the driving speed of the two-dimensional fast reflex mirror. The FPGA processor calculates the driving amount of the two-dimensional fast reflex mirror according to the fast reflex mirror control value of the error compensation module and the residual value of the airborne servo turntable, and after high-precision AD conversion circuit, generates analog driving amount to control the movement of the two-dimensional fast reflex mirror. In order to improve the response speed of the two-dimensional fast reflex mirror, the maximum value of the driving amount is limited but not smoothed.

7. The airborne multi-field / continuous zoom thermal imager oversampling control system according to claim 1, characterized in that: The detector control module is connected to the two-dimensional fast reflex mirror position feedback circuit, performs high-precision AD sampling on the analog quantity of the two-dimensional fast reflex mirror position signal, sets the position signal threshold, and when the position signal reaches the threshold, instructs the two-dimensional fast reflex mirror to move into position, generates a driving level signal, and drives the detector to start integral sampling; since the timing of the movement of the two-dimensional fast reflex mirror in two directions is known in advance, the detector control module only needs to perform AD sampling on the two-dimensional fast reflex mirror position signal in one movement direction, and then generates a driving level signal in a timing manner within a scanning cycle to reduce the scale of the AD sampling circuit.

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