Abstract:SignaltoNoise Ratio (SNR) is a key parameter for low light level imaging systems. It determines the performance and image quality of an imaging system. A SNR calculation model of low light level imaging systems based on CMOS imaging sensors is given. The relationship between the SNR and the signal and noise of a system is simulated. A SNR test environment is set up and SNR test experiment is completed. The experimental results show that the theoretical value is consistent with the measured value. Finally, the parameters of a given system are optimized according to the SNR analysis results. The calculation results show that the optimized system improves its SNR up to 4.5 under 1 mlux. This study of SNR provides the theoretical basis for the overall design and optimization of low light level imaging system based on CMOS image sensors.

Abstract:The reference based Non-Uniformity Correction (NUC) is susceptible to the special application situation and the working condition drift of the instrument. This may result in the output images with poor quality. To solve this problem, a scenebased NUC algorithm for the total variation model is realized on the Field Programmable Gate Array (FPGA) platform. The application principle of the model and some measures for suppressing image ghosts and degradation are presented. Function debugging and performance testing are completed in some cooled LWIR detectors. The experimental results show that this algorithm can accomplish correction convergence in 20 frames and satisfactory imaging quality is achieved.

Abstract:In recent years, hyperspectral imagers have developed rapidly. With their use in more and more complicated applications, higher requirements are put forward for the processing precision of remote sensing images. As an important step in the processing of remote sensing images, image registration is crucial to the subsequent processing of remote sensing images. There are many registration methods for remote sensing images. At present, most mature registration methods are those methods which conduct registration in the case of different sensors and same resolution. There are few registration methods for the remote sensing images in the case of different sensors and different resolution. A new registration algorithm for extracting point features on the basis of image edge features is proposed. Image registration results are obtained and validated. Compared with the existing registration algorithms, the registration precision of the algorithm is improved greatly.

Abstract:With the development of signal processing algorithms, the algorithm updatable requirement is put forward for the Field Programmable Gate Array (FPGA) used in the field of space. Since traditional fixed algorithm models could not meet this requirement, the inorbit reconfigurable design of FPGAs onboard satellites becomes the key to solve the problem. A FPGA reconfigurable design scheme based on the satellite-to-ground link is proposed. In the scheme, the configuration data are uploaded through the satellite-to-ground link and are stored in the Electrically Erasable Programmable read only memory (EEPROM). Then, an antifuse device is used to implement large scale algorithm reconfiguration on the FPGA. This design scheme is verified and the flexibility of the spaceborne FPGAs is improved.

Abstract:Doublelayer diffractive optical elements (DOEs) can work within a wide spectral band and have high diffraction efficiency. A mathematical analytic model of the polychromatic bandwidth integration average diffraction efficiency for doublelayer DOEs in a certain incident angle range is proposed. A 0.4 to 0.9 μm wide waveband optical system containing doublelayer DOEs is designed. The optical system has a focal length of 28 mm, a F/# of 2 and a field of view of 18°. It uses a Petzval objective structure consisting of four lenses. Its Modulation Transfer Function (MTF) is greater than 0.67 at 60 lp/mm. The bandwidth integration average diffraction efficiency of its doublelayer DOEs is above 91% in the 0.4 to 0.9 μm waveband. In the optical system, the incident angle upon the diffractive surface is within the range of 0° to 8.62°. The comprehensive bandwidth integration average diffraction efficiency of the double-layer DOEs is 97.36%. Compared with the traditional refractive wide waveband optical system, this wide waveband optical system containing double-layer DOEs has a simpler structure and higher resolution.

Abstract:Since the scene adaptive nonuniformity correction (NUC) algorithm based on neural network is easy to generate the phenomenon of "ghost" when it removes the noise in the images output by infrared imaging systems, an improved adaptive nonuniformity correction algorithm is proposed. By applying kernel regression interpolation to the neural network algorithm, the probability of "ghost" phenomenon caused by the adaptive nonuniformity algorithm is reduced effectively. The experimental results show that compared with the traditional neural network algorithm, the proposed algorithm not only can eliminate nonuniformity noise effectively, but also can restrain the generation of "ghost" phenomenon greatly under the same conditions.

Abstract:A high temperature CO₂ flow field was set up in a high frequency plasma wind tunnel. The profiles of temperature and mole fraction were obtained through measurement and calculation. At the same time, infrared spectrum measurement experiment was carried out. The equipment, principle and method used in the experiment were given. Experiment was made under four different temperature conditions between 1500 K and 3000 K. The infrared spectral data of v₃ vibration band of CO₂ near 4.3 μm at different temperatures were acquired. It was found that the peak position of the spectral curve moved in the direction of long wavelength as temperature increased. Through theoretical analysis, the reason about the "red shift" occurred in the measurement of infrared radiation of CO₂ at high temperature and its difference from the red shift in astrophysics were obtained. This theory could be used in the measurement of high temperature gas.

Abstract:Infrared reflectance spectroscopy was used to test six kinds of plastic imitation materials for gems in jewelry market. Those materials were compared with the corresponding six real gem materials including pink coral, ivory, rhodochrosite, green chalcedony, rock crystal and synthetic black opal. The results showed that the infrared spectra of plastic imitations were significantly different from those of real gemstones due to the differences in material composition and molecular structure. Infrared spectroscopy not only could identify and classify plastics according to the number, position, morphology, strength and spectral division of infrared spectral peaks, but also was a quick, accurate and nondestructive means for testing plastic imitations. In particular, for the identification of those high imitation products with appearance and basic physical characteristics quite similar to their corresponding real stones (such as imitations for synthetic black opal), conventional identification means were not effective, but infrared reflectance spectroscopy could play an irreplaceable role.