According to the application requirements of airship-borne photoelectric payload, a low-noise miniaturized signal processing system for airship-borne multi-spectral infrared camera is designed and implemented. The system includes medium wave signal processing circuit, long wave signal processing circuit and integrated control circuit. High integrated design technology is adopted in medium wave signal processing circuit and long wave signal processing circuit to achieve high-precision bias voltage generation, low-noise analog signal conditioning, detector focal plane temperature monitoring, detector timing generation, image processing, data transmission. The size of each signal processing circuit is only 84mm×50mm×20mm. The integrated control circuit realizes the image data framing and encoding based on ARINC818 standard of the Avionics Digital Video Bus in FPGA, and sends the encoded high-speed digital video to the airship platform through optical fiber, which realizes the highly reliable and lightweight data transmission. After the introduction of the key technologies of each circuit, the experimental verification of the signal processing system for airship-borne multi-spectral infrared camera is carried out. The experimental results show that the design scheme of the signal processing system is reasonable and feasible. While realizing the miniaturization design, the system noise is lower than 0.3mV and the data transmission rate is up to 2.125Gbps, which meets the requirements of camera system.
In this paper, according to the detection requirements of space infrared camera with large dynamic range and high sensitivity, a Time Delay and Integration (TDI) infrared imaging circuit with large dynamic range is introduced. The designed imaging circuit consists of 1024×7 TDI infrared detector, analog conditioning circuit and data processing circuit. 1024×7 TDI infrared detector is composed of 1024 pixel of seven photosensitive elements on which Time Delay and Integration is performed through the readout integrated circuit. In Time Delay and Integration part, an adaptive TDI stages adjustment circuit is presented, which can automatically switch seven TDI stages or one TDI stage for each pixel according to the intensity of camera detection signal,and the TDI stage mark for each pixel is provided. In analog conditioning circuit part,background subtraction circuit,programmable gain amplification circuit and 14bit ADC are designed. The background signal level is produced by 12bit DAC and the digital data of DAC is calculated from the downloaded image data of the space camera. On the basis of downloaded image data, the digital data can be dynamically uploaded to digital to analog converter by upper computer. The output analog signal of infrared detector is subtracted from background signal level, and then the effective analog signals after the background subtraction are amplified by programmable gain amplification circuit to adapt to the input scale of high precision ADC, which can reduce the equivalent input noise and can improve the dynamic range of space camera. Digital data processing circuit is implemented with FPGA. According to TDI stage mark for each pixel, the TDI stages normalization of each pixel is performed to reconstruct the pixel data in data processing circuit, and the normalized pixel data is corrected by pixel response non-uniformity correction algorithm to improve the quality of images. The designed imaging circuit system is tested, and test results show that the design scheme of the imaging circuit system is reasonable and feasible, which can effectively improve the dynamic range of space infrared camera.
With the increasing demand of users for the extraction of remote sensing image information, it is very urgent to significantly enhance the whole system’s imaging quality and imaging ability by using the integrated design to achieve its compact structure, light quality and higher attitude maneuver ability. At this present stage, the remote sensing camera’s video signal processing unit and image compression and coding unit are distributed in different devices. The volume, weight and consumption of these two units is relatively large, which unable to meet the requirements of the high mobility remote sensing camera. This paper according to the high mobility remote sensing camera’s technical requirements, designs a kind of space-borne integrated signal processing and compression circuit by researching a variety of technologies, such as the high speed and high density analog-digital mixed PCB design, the embedded DSP technology and the image compression technology based on the special-purpose chips. This circuit lays a solid foundation for the research of the high mobility remote sensing camera.
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