Abstract:A compact field hyperspectral imaging spectrometer based on a prism-grating-prism structure is presented. The system is designed for the wavelength range from visible light to near infrared. It has 344 spectral bands with the spatial resolution higher than 10 nm and the spectral resolution higher than 1 mrad. To study the unmixing of mixed pixels, the basic principle of the field hyperspectral imaging spectrometer is described, the main specifications of the system is analyzed, the design of the system is discussed in detail and related tests are conducted. The test results show that the system has both higher spatial resolution and higher spectral resolution. Because of its compactness and reliable operation, it is very suitable for field applications. Thus, the feasibility of the use of a compact field hyperspectral imaging spectrometer in the research on the unmixing of mixed pixels is verified.

Abstract:Operating distance is an important specification of infrared systems for detecting low temperature targets in space. By taking the noise of an infrared focal plane detector as the main factor, an operating distance estimation equation for point targets is derived. A calculation example of the operating distance of a typical infrared detection system is given. For the low temperature point target in space, the operating distance of the infrared detection system is verified by using both an energy equivalent method and a dimension equivalent method according to the signal-to-noise criterion in laborotary. The measured result is in agreement with the theoretical estimation. The test shows that the method can be used to evaluate the operating distance of an infrared detection system for detecting low temperature point targets in laboratory.

Abstract:Fiber optical gyro (FOG) is a new developed inertial measurement unit for inertial navigation systems. Its performance geatly depends on the photoelectric devices such as optical sources, integrated chips and photoelectric detectors used. The main noise mechanisms of high precision fiber optic gyros are presented and the Allan variance analysis of two gyros with different precision is made. The content of white noise and fractal noise in a FOG is judged according to the estimated noise parameters of the FOG. Thus, the precision of the FOG is verified and the improved schemes for FOGs with different precision are given so as to provide theoretical guidance for the improvement of the precision of FOGs.

Abstract:The ZnS thin film is deposited on a porous Si substrate by using a pulsed laser deposition method. The crystalline structure, surface morphology and optical properties of the ZnS thin film are studied respectively by using a X-ray diffraction instrument, a scanning electron microscopy and a fluorescence spectrophotometer. The results show that the ZnS film has a crystalline structure in cubic phase and is grown in a prefered orientation along the β-ZnS (111) direction. After annealing in vacuum at 300℃ for 30min, the X-ray diffraction peak intensity of the ZnS film is increased and its surface becomes rough. In the visible spectral region, the film has an average transmittance of 80\%. So, it is suitable for the buffer layer of solar cells, infrared antireflection coating, infrared windows and domes etc.. In the photoluminescence spectra of the annealed ZnS/porous Si composite system, besides the blue light emission of the ZnS film at the high energy end and the red light emission of the porous Si at the low energy end, there appears a new green light emission at about 550nm. This is attributed to the defect-center luminescence generated by the defect energy level formed in the annealing process of the ZnS film. According to the tricolor overlay principle, the blue and green light of the ZnS is combined with the red light of the porous Si. As a result, more intensive white light is generated from the ZnS/porous Si composite system. This opens a new way for the realization of solid white light emitted devices.

Abstract:Noise equivalent temperature difference is of great importance to the evaluation of the performance of infrared systems. It is helpful to the performance improvement, cost reduction and production periode shortening of infrared systems. Noise equivalent temperature difference is one of the important specifications for measuring the performance of infrared detector systems. It is related to the total atmospheric transmittance and detector performance parameters etc.. The expression of the noise equivalent temperature difference is deduced. The performance of a particular infrared detector is characterized by using the noise equivalent temperature difference and various performance influence factors are examined through a special program we wrote.

Abstract:A hollow beam has its particular physical properties and has wide applications in the fields of optical information process, microelectronics, isotope seperation and molecule optics etc.. A TFT-LCD is proposed to be used to fabricate a phase-mode Fresnel Zone Plate and hence a hollow beam can be formed by the plane wave via the TFT-LCD. The experimental result shows that the hollow beam generated from the Fresnel Zone Plate based on a TFT-LCD has the advantages of real-time adjustability, simplicity and accuracy.

Abstract:Three kinds of different age rank milk powder are identified by using the near infrared spectroscopy with support vector machines (SVM). First, the Kennard-Stone method is used to select 120 training sets from 150 samples and other 30 samples are used as the prediction sets. In the experiment, the radial basis function is selected as the kernel function and the two-step grid searching and five-fold cross validation are used to optimize two model parameters: kernel function γ and penalty factor C. The optimal γ and C are 0.03125 and 2048 respectively. The correction model established with the optimal parameters has an identification rate of 100% for both training sets and prediction sets. By comparison with the principal component analysis (PCA), the SVM exhibits its higher identification accuracy. This shows that the near infrared spectroscopy can identify the varieties of different age rank milk powder quickly and accurately.

Abstract:Although the light scattering technology can be used to detect the proteins in milk, there are many factors which have influence on its detection accuracy in practical use. The light scattering characteristics of the proteins in milk are analyzed. On the basis of this analysis, the Mie scattering theory and optical simulation software are used to study the factors such as laser wavelength, scattering angle and ambient temperature etc which have influence on the scattering light intensity of the proteins in milk to be detected. Through simulation, the best laser wavelength is determined to be 1333nm or 1660nm; the better scattering angles are determined to be 0°, ± 30° and ±90° and the suitable ambient temperature is from 40℃ to 60℃. This can provide the data support for the improvement of the detection accuracy of an instrument. The method does not need any actual detection instruments. Thus, it can avoid the complicated operation of a detection instrument and eliminate any artificial errors. Moreover, all parameters can be adjusted according to the requirement in experiment and the study cost can be saved.

Abstract:A practical first-order simulation method for simulating the temperature field of a cadmium zinc telluride crystal growth furnace is presented. The method is based on the heat transfer principle, uses the Monte Carlo method to calculate the angle factors without analytical expressions and utilizes the matrix computation function in MATLAB to solve the multi-variable linear algebraic equations. It is simple and easy to use.

Abstract:Uncooled infrared thermal imagers have the features of low price, low weight, low power dissipation, small size and reliability etc.. An uncooled infrared thermal imager with an infrared micro-bolometer focal plane array is used to analyze the temperature distribution and lesions of human bodies. Because infrared grey scale images have lower contrast and the grey scales of the images of different parts of a human body are different, the pseudo-color images obtained by the infrared thermal imager are processed by using an adaptive threshold processing method. The processing results are of great convenience for analyzing the location and size of lesions.