Area array type infrared distance measuring camera based on APD

Abstract

The utility model relates to an area array type infrared distance measuring camera based on an APD (avalanche photo diode), which comprises an APD detector, an MCU (microprogrammed control unit) control module, a bias compensation circuit, an exposure control module, an exposure execution mechanism, a current acquisition circuit, a signal amplification circuit, an AD (analog-to-digital) conversion circuit, an image processing module, a laser control module, a laser pulse generator and an FPGA (field programmable gate array) processing circuit. The APD device comprises a plurality of groups of APD devices which are arranged in an area array. According to the infrared distance measurement camera, no auxiliary equipment is needed, the pulse laser generator is controlled to emit laser pulse signals to an object, and after the APD device receives laser pulse echo signals, laser distance measurement and infrared imaging of the object can be achieved by collecting current signals generated by the APD device and processing the current signals. According to the infrared distance measurement camera, data or signals do not need to be transcoded, forwarded and the like, the problem that the data or the signals are not synchronous is solved, and the complexity and the data processing amount of a whole machine system can be remarkably reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of infrared detection, in particular to an APD-based array infrared ranging camera. Background Art

[0002] Infrared small target detection has attracted many scholars at home and abroad to study it because of its great application value in many fields. To solve this problem, the industry generally equips auxiliary equipment such as rangefinders or radars to complete auxiliary detection, which is also one of the most widely used methods. The use of auxiliary equipment in the industry is mainly to upload the object distance information of the current detected target to the processing center of the whole system in real time at a certain frequency. The processing center decodes and packages it and forwards it to the infrared thermal imaging camera and other detection systems. Then the infrared camera zooms and focuses according to the current object distance change to achieve continuous detection of the target of interest.

[0003] Since the above solution involves the coordinated use of two independent devices, a series of problems will arise: (1) The physical assembly of the auxiliary device and the infrared camera must be highly consistent; (2) The data exchange between the rangefinder and the infrared camera must go through several decoding and forwarding steps, which will inevitably lead to data asynchrony; (3) The additional ranging device will increase the complexity of the entire system and the amount of data processing. Utility Model Content

[0004] Based on the above description, the utility model provides an APD-based area array mid-band infrared ranging camera to reduce the complexity of the system.

[0005] The technical solution of the utility model to solve the above technical problems is as follows:

[0006] An APD-based array infrared ranging camera comprises an APD detector, an MCU control module, a bias compensation circuit, an exposure control module, an exposure actuator, a current acquisition circuit, a signal amplification circuit, an AD conversion module, an image processing module, a laser control module, a laser pulse generator and an FPGA processing circuit; the APD detector comprises a plurality of APD devices arranged in an array; the bias compensation circuit is connected to the MCU control module and to the APD device, and is used to output a bias control signal to the APD device; the exposure control module is connected to the MCU control module and to the exposure actuator, and is used to control The exposure time of the APD device; the current acquisition circuit is connected to the APD device, and is used to acquire the photogenerated current of the APD device; the signal amplification circuit is connected to the current acquisition circuit, and is used to amplify the photogenerated current acquired by the current acquisition circuit; the AD conversion module is connected to the signal amplification circuit, and is used to convert the photogenerated current signal into a digital signal; the FPGA processing circuit is connected to the MCU control module and to the exposure control module, and is used to perform phase shift processing on the exposure control signal; the laser control module is connected to the MCU control module and to the pulse laser generator, and is used to control the laser pulse generator.

[0007] As a preferred solution: the APD detector is a 256×256 APD array detector.

[0008] As a preferred solution: the APD device is an APD device based on mercury cadmium telluride material.

[0009] As a preferred solution: the FPGA processing circuit includes a delay module and a differential drive module. After obtaining the specified object distance, the FPGA processing circuit calculates the exposure delay time Delay Data of the APD detector and latches it into the register of the pulse rising edge delay module. The delay module starts counting the internal counter after detecting the rising edge of the pulse signal output by the MCU control module. When the count value is equal to the Delay Data value, the delay module outputs a pulse signal for camera exposure; the pulse signal is sent to the exposure control module in a differential manner through the differential drive module. After receiving the pulse signal, the exposure control module controls the action of the exposure actuator.

[0010] As a preferred solution: the infrared ranging camera also includes a temperature detection module, a voltage acquisition circuit, a first switch unit and a second switch unit; wherein the temperature detection module is a chip temperature sensor, which is mounted on the back of the APD detector and is used to detect the temperature of the APD detector, the output end of the temperature detection module is connected to the MCU control module, the input end of the voltage acquisition circuit is connected to the output end of the bias compensation circuit, the output end of the voltage acquisition circuit is connected to the MCU control module, the first switch unit is connected between the voltage output end of the bias compensation circuit and the voltage input end of the APD detector, the control signal output end of the MCU control module is connected to the control end of the first switch unit, the second switch unit is connected between the control signal output end of the laser control module and the driving end of the pulse laser generator, and the control signal output end of the MCU control module is connected to the control end of the second switch unit.

[0011] As a preferred solution: during the operation of the infrared ranging camera, the temperature detection module detects the temperature of the APD device in real time and feeds back the temperature detection result to the MCU control module; the MCU control module compares the detected temperature with a preset temperature threshold. When the former is greater than the latter, the MCU control module reads the voltage value collected by the voltage acquisition circuit and compares the collected voltage value with a default bias voltage. When the difference between the collected voltage value and the default bias voltage is greater than a preset value, the MCU control module controls the first switch unit to change from an on state to an off state; when the difference between the collected voltage value and the default bias voltage is less than a preset value, the MCU control module controls the second switch unit to change from an on state to an off state.

[0012] Compared with the prior art, the technical solution of the present application has the following beneficial technical effects: the infrared ranging camera does not require auxiliary equipment, and only needs to control the pulse laser generator to send a laser pulse signal to the object. After the APD device receives the laser pulse echo signal, the current signal generated by the APD device is collected and processed to achieve laser ranging and infrared imaging of the object. There is no need to transcode or forward the data or signal, and there will be no problem of data or signal asynchrony. The infrared ranging camera can significantly reduce the complexity of the entire system and the amount of data processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a circuit schematic diagram of the infrared ranging camera in Example 1;

[0014] Figure 2 is a schematic diagram of the FPGA processing circuit in Example 1;

[0015] Figure 3 This is a circuit schematic diagram of the infrared ranging camera in Example 2. DETAILED DESCRIPTION

[0016] Embodiment 1:

[0017] Reference Figure 1 A mid-band infrared ranging camera based on APD includes an APD detector, an MCU control module, a bias compensation circuit, an exposure control module, an exposure actuator, a current acquisition circuit, a signal amplification circuit, an AD conversion module, an image processing module, a laser control module, a laser pulse generator and an FPGA processing circuit.

[0018] The APD detector includes multiple groups of APD devices arranged in a planar array.

[0019] The control signal input terminal of the bias compensation circuit is connected to the control signal output terminal of the MCU control module, and the voltage output terminal of the bias compensation circuit is connected to the voltage input terminal of the APD device. The bias compensation circuit is used to output a bias control signal to the APD device.

[0020] The command signal input terminal of the exposure control module is connected to the command signal output terminal of the MCU control module, and the control signal output terminal of the exposure control module is connected to the driving terminal of the exposure actuator. The exposure actuator is used to control the exposure time of the APD device.

[0021] The input end of the current collection circuit is connected to the signal output end of the APD device, and is used to collect the photogenerated current of the APD device; the input end of the signal amplification circuit is connected to the output end of the current collection circuit, and is used to amplify the signal of the photogenerated current collected by the current collection circuit.

[0022] The input end of the AD conversion module is connected to the input end of the signal amplification circuit, which is used to convert the photocurrent signal into a digital signal. The output end of the AD conversion module is connected to the sampling signal input end of the MCU control module, and the output end of the AD conversion module is connected to the image processing module.

[0023] The input end of the FPGA processing circuit is connected to the I / O port of the MCU control module, and the output end of the FPGA processing circuit is connected to the signal input end of the exposure control module. The laser control module is connected to the MCU control module for communication, and the control signal output end of the laser control module is connected to the driving end of the pulse laser generator. The laser control module is used to control the laser pulse generator.

[0024] The working principle of the infrared ranging camera in this embodiment is:

[0025] After the camera is started, the MCU control module sends a control signal to the bias compensation circuit, causing the bias compensation circuit to output a default bias voltage to the APD device. The bias voltage enables the APD device to operate in a linear mode, that is, the APD device operates in a linear amplification region below the avalanche breakdown voltage. In the linear mode, the intensity of the photocurrent signal generated by the APD device is proportional to the intensity of the laser pulse signal irradiating the APD device.

[0026] After the camera is started, the laser control module controls the pulse laser generator to send a laser pulse signal to the object. The laser pulse signal is reflected after irradiating the object, and the reflected echo signal irradiates the APD device, causing the APD device to start generating a photocurrent signal. While controlling the laser pulse generator to emit a laser pulse signal, the laser control module sends a synchronization signal to the MCU control module. After receiving the synchronization signal, the MCU control module starts to read the collected photocurrent signal and starts timing.

[0027] After the photocurrent signal collected by the current acquisition circuit is amplified and converted, the converted signal is further processed and digitized by the image processing module to form an infrared image of the object being measured.

[0028] Because the echo signal photons of the laser pulse signal will cause an avalanche event in the APD device when they reach the APD device, which will cause the current signal intensity of each APD device to change differently. When the current signal output by the APD device does not continue to change, the MCU control module calculates the time of each APD device during the entire current change period, so that the distance between the detected object and each APD device can be calculated, and further the object distance between the object and the ranging camera can be calculated.

[0029] After the MCU control module calculates the object distance information, the image processing module processes the object distance information on the image at the back end.

[0030] This enables laser ranging and infrared imaging of objects.

[0031] The infrared ranging camera in this embodiment does not require any auxiliary equipment. It only needs to control the pulse laser generator to send a laser pulse signal to the object. After the APD device receives the laser pulse echo signal, it can realize laser ranging and infrared imaging of the object by collecting the current signal generated by the APD device and processing the current signal. There is no need to transcode or forward the data or signal, and there will be no problem of data or signal asynchrony. The infrared ranging camera can significantly reduce the complexity of the entire system and the amount of data processing.

[0032] The APD detector in this embodiment is a 256×256 APD area array detector. In addition, the APD device in this embodiment is an APD device based on mercury cadmium telluride material.

[0033] The infrared ranging camera in this embodiment can detect the target at the specified object distance by performing phase shift processing on the exposure control signal of the APD detector. Specifically, after the user determines the specified object distance to be detected, the specified object distance is input into the MCU control module, and the MCU control module feeds back the specified object distance information to the FPGA processing circuit.

[0034] Reference Figure 2 , the FPGA processing circuit in this embodiment includes a delay module and a differential drive module.

[0035] After the FPGA processing circuit obtains the specified object distance, it calculates the exposure delay time Delay Data of the APD detector and latches it into the register of the pulse rising edge delay module. After detecting the rising edge of the pulse signal output by the MCU control module, the delay module starts the internal counter counting. When the count value is equal to the Delay Data value, the delay module outputs a pulse signal for camera exposure; the pulse signal is sent to the exposure control module in a differential manner through the RS422 differential drive module. After receiving the pulse signal, the exposure control module controls the action of the exposure actuator, thereby realizing the delay control of the exposure of the APD device, so that the interference echo signals of objects at other object distances can be shielded, and only the objects at the specified object distance can be detected.

[0036] Embodiment 2:

[0037] Reference Figure 3 The difference between this embodiment and the first embodiment is that the infrared ranging camera in this embodiment further includes a temperature detection module, a voltage acquisition circuit, a first switch unit and a second switch unit.

[0038] The temperature detection module is a chip temperature sensor, which is mounted on the back of the APD detector and is used to detect the temperature of the APD detector. The output end of the temperature detection module is connected to the sampling signal input end of the MCU control module.

[0039] The input end of the voltage acquisition circuit is connected to the output end of the bias compensation circuit, and the output end of the voltage acquisition circuit is connected to the sampling signal input end of the MCU control module.

[0040] The first switch unit is connected between the voltage output terminal of the bias compensation circuit and the voltage input terminal of the APD detector, and the control signal output terminal of the MCU control module is connected to the control terminal of the first switch unit.

[0041] The second switch unit is connected between the control signal output end of the laser control module and the driving end of the pulse laser generator, and the control signal output end of the MCU control module is connected to the control end of the second switch unit.

[0042] During operation of the infrared ranging camera in this embodiment, the temperature detection module detects the temperature of the APD device in real time and feeds back the temperature detection result to the MCU control module; the MCU control module compares the detected temperature with a preset temperature threshold value. When the former is greater than the latter, the MCU control module reads the voltage value collected by the voltage acquisition circuit and compares the collected voltage value with the default bias voltage. When the difference between the collected voltage value and the default bias voltage is greater than the preset value, the MCU control module controls the first switch unit to change from the on state to the off state; when the difference between the collected voltage value and the default bias voltage is less than the preset value, the MCU control module controls the second switch unit to change from the on state to the off state.

[0043] APD detector temperature that is too high may cause device damage, and excessive bias voltage or excessive laser pulse signal may cause the APD detector to overheat.

[0044] Through the above scheme, when it is detected that the temperature of the APD detector is too high, it is first determined whether the bias voltage changes too much. If so, the first switch unit is disconnected to make the bias compensation circuit stop outputting the bias voltage to the APD device, so that the APD device can stop working; otherwise, the second switch is disconnected to make the laser control module stop outputting the control signal to the pulse laser generator, so that the pulse laser generator can stop emitting the laser signal; the above measures can play the role of high temperature emergency protection of the APD device.

[0045] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An APD-based array infrared ranging camera, characterized by: The invention comprises an APD detector, an MCU control module, a bias compensation circuit, an exposure control module, an exposure actuator, a current acquisition circuit, a signal amplification circuit, an AD conversion module, an image processing module, a laser control module, a laser pulse generator and an FPGA processing circuit; the APD detector comprises a plurality of APD devices arranged in a planar array; the bias compensation circuit is connected to the MCU control module and to the APD device, and is used to output a bias control signal to the APD device; the exposure control module is connected to the MCU control module and to the exposure actuator, and is used to control the exposure time of the APD device; the current acquisition circuit is connected to the APD device, and is used to acquire the photogenerated current of the APD device; the signal amplification circuit is connected to the current acquisition circuit, and is used to amplify the signal of the photogenerated current acquired by the current acquisition circuit; the AD conversion module is connected to the signal amplification circuit, and is used to convert the photogenerated current signal into a digital signal; the FPGA processing circuit is connected to the MCU control module and to the exposure control module, and is used to perform phase shift processing on the exposure control signal; the laser control module is connected to the MCU control module and to the pulse laser generator, and is used to control the laser pulse generator.

2. The APD-based array infrared ranging camera according to claim 1, characterized in that: The APD detector is a 256×256 APD area array detector.

3. The APD-based array infrared ranging camera according to claim 1, characterized in that: The APD device is an APD device based on mercury cadmium telluride material.

4. The APD-based array infrared ranging camera according to claim 1, characterized in that: The infrared ranging camera also includes a temperature detection module, a voltage acquisition circuit, a first switch unit and a second switch unit; wherein the temperature detection module is a chip temperature sensor, which is mounted on the back of the APD detector and is used to detect the temperature of the APD detector. The output end of the temperature detection module is connected to the MCU control module, the input end of the voltage acquisition circuit is connected to the output end of the bias compensation circuit, the output end of the voltage acquisition circuit is connected to the MCU control module, the first switch unit is connected between the voltage output end of the bias compensation circuit and the voltage input end of the APD detector, the control signal output end of the MCU control module is connected to the control end of the first switch unit, the second switch unit is connected between the control signal output end of the laser control module and the driving end of the pulse laser generator, and the control signal output end of the MCU control module is connected to the control end of the second switch unit.

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