Image improvement based on sub-pixel post-integration for a staring imaging system in geostationary orbit

This paper proposes the post-integration technology based on sub-pixel image registration and image fusion to improve the signal-to-noise ratio （SNR） of remote sensing images without motion degradation caused by satellite vibration. A two-dimensional vibration system is set up to simulate satellite disturbance. Image sequences with different exposure times are captured using a high-speed CMOS camera. The displacement plots are compared with the motion data measured by the grating linear encoder. These plots indicate that the accuracy of the registration algorithm is better than 0.1 pixels. The sub-pixel image fusion shows an improvement in image quality, thus indicating that this technology is powerful for staring imaging systems in geostationary orbit.     

Non-piece-wise error compensation for grating displacement measurement system with absolute zero mark

A method for compensating the measuring error of the grating displacement measurement system with absolute zero mark is presented. It divides the full scale range into piece-wise subsections and compares the maximum variation of the measuring errors of two adjacent subsections with the threshold. Whether the specified subsection is divided into smaller subsections is determined by the comparison result. After different compensation parameters and weighted average values of the random errors are obtained, the error compensation algorithm is implemented in the left and right subsections, and the whole measuring error of the grating displacement measurement system is reduced by about 73%. Experimental results show that the method may not only effectively compensate the spike error but also greatly improve the precision of the measuring system.     

Automated image processing algorithm for Young's fringe pattern analysis

An automatic of image processing for the analysis of Young's fringe pattern is proposed. A Young's fringe patttern is first FFT treated to get two patterns of 0 degree and 90 degree phase shifted. Regular two pattern shift algorithm is used to calculate the phase of the Young's pattern. One or two times of phase shift iteration are carried out to improve the phase. Then the phase is least square fitted to get a phase plane. The displacement magnitude and direction are eaasily induced from the phase plane. Because every step is full field treatment, very precise result is achieved. The algorithm is simple and easy to implement. Theory and experiment are presented to prove the proposal. A program is designed to execute the algorithm and the processing is automated by a Personal Computer with an image board.     

Study on the wavelength calibration of type Ⅲ concave grating spectrometry system

We discuss and calibrate the spectronietry system based on concave reflection grating. The working principle, structure and parameters of the spectronietry system are introduced. For the wavelength calibration problem, three methods are put forward and discussed in detail with formulation calculation method, circular iteration method and interpolation. Interpolation is used to calibrate the concave reflection grating     

Experimental research of circular incoherently synthetic aperture imaging ladar using chirped-laser and heterodyne detection

Synthetic aperture imaging ladar (SAIL) technique belongs fully coherent processing in both the time domain and space domain and has a rather high implement difficulty. To solve this problem, the concept of circular incoherently SAIL is introduced. A speckle version image of a two-dimensional (2D) letter ’E’ target is reconstructed from E-field projection data detected by a circular incoherently SAIL system. The experimental system is constructed by three subsystems using chirped-pulse laser as the light source and heterodyne detection to get the range information of the target. The reconstruction of the image and the noise effect are also discussed in detail.     

Modeling and analysis for the image mapping spectrometer

The snapshot image mapping spectrometer(IMS) has advantages such as high temporal resolution,high throughput,compact structure and simple reconstructed algorithm.In recent years,it has been utilized in biomedicine,remote sensing,etc.However,the system errors and various factors can cause cross talk,image degradation and spectral distortion in the system.In this research,a theoretical model is presented along with the point response function(PRF) for the IMS,and the influence of the mirror tilt angle error of the image mapper and the prism apex angle error are analyzed based on the model.The results indicate that the tilt angle error causes loss of light throughput and the prism apex angle error causes spectral mixing between adjacent sub-images.The light intensity on the image plane is reduced to 95%when the mirror tilt angle error is increased to ±100 "(≈ 0.028°).The prism apex error should be controlled within the range of 0-36"(0.01°)to ensure the designed number of spectral bands,and avoid spectral mixing between adjacent images.     

Grating imaging scanning lithography

We present a grating imaging scanning lithography system for the fabrication of large-sized gratings. In this technology, ±1-order diffractive beams are generated by a phase grating and selected by a spatial filter. Meanwhile, a 4f system enables the ±1-order diffractive beams to form a grating image with a clear jagged-edge boundary on the substrate. A high-precision two-dimensional （2D） mobile stage is used for complementary cyclical scanning, thereby effectively eliminating image stitching errors. The absence of such errors results in a seamless and uniform large-sized grating. Characterized by a simple structure, high energy use, and good stability, this lithography system is highly relevant to the high-speed and cost- effective production of large-sized gratings.     

Virtual reproducing system for 5.1 channelsurround sound

An improved virtual reproducing system for 5.1 channel surround sound and signal processing algorithm of the system are proposed. Firstly, by analyzing the sound field of virtual reproducing systems for 5.1 ch surround sound, it is proved that there are some defects in current systems, including narrow listening area, sound image direction distortion, timbre change in reproduction etc. Then from theoretical analysis, it is proposed that, by decreasing the separated angle between reproducing loudspeaker pair to ±15° and using signal processing algorithm with timbre equalization, the improved system can get rid of the defects of current systems. Additionally, the signal processing algorithm of improved system is also simple. The results of psychoacoustic experiment verify theoretical analysis, and show that improved system is able to recreate sound image in half of horizontal plane (about±90°) in the front. Finally, the system and its arrangement of loudspeakers are suitable to be used in TV sets or mu     

Effects of error feedback on a nonlinear bistable system with stochastic resonance

In this paper,we discuss the effects of error feedback on the output of a nonlinear bistable system with stochastic resonance.The bit error rate is employed to quantify the performance of the system.The theoretical analysis and the numerical simulation are presented.By investigating the performances of the nonlinear systems with different strengths of error feedback,we argue that the presented system may provide guidance for practical nonlinear signal processing.     

Birefringence Grating and Surface Grating in Azobenzene Polymer Liquid Crystal Films Investigated by Near—Field Optical method

The birefringence grating and the surface grating in azobenzene polymer liquid-crystal (Azo-PLC) films are studied by a near-fied scanning optical microscope.With laser irradiation,the refractive index change caused by birefringence and the sinusoidal surface profile are observed at the near-field transmittance image and the surface topography of the grating.The grating period and the peak-to-peak value of the sinusoidal surface profile are 0.8μm and 40nm,respectively.The maximum diffractive efficiency of the grating is 2% .The dynamic process of the grating formation is probed and analysed.The mass diffusion responsible for the formation of the surface grating due to the temperature rise is analysed.