Bin Xue

An improved Fourier-based sub-pixel image registration algorithm for raw image sequence of LASIS

Previous studies indicate that parallel computing for hyperspectral remote sensing synthetic image generation is quite feasible. However, due to the limitation of computing ability within single cluster, one can only generate three bands and a 1000*1000 pixels image in a reasonable time period even using a 40-50 node parallel computing cluster. In this paper, we discuss the capability of using Grid computing where the so-called eScience or cyberinfrastructure is utilized to integrate distributed computing resources to act as a single virtual computer with huge scientific computational abilities and storage spaces. The technique demonstrated in this paper demonstrates the feasibility of a Grid-Enabled Monte Carlo Hyperspectral Synthetic Image Remote Sensing Model (GRID-MCHSIM) for future coastal water quality remote sensing algorithm developments and detection of bottom features and targets in water.

Optical system design of subminiature endoscope with imaging fiber bundle

A new subminiature endoscope which used for reconnaissance and diagnosis has been designed. This subminiature endoscope is designed based on imaging fiber bundle and consist of the front object lens whose aperture is only 0.5mm, imaging fiber bundle and the post coupling lens. It realized by using subminiature optical systems . The FOV(field of view) and the focal length of the front object lens are 50° and 0.59mm. And the object distance, F number and detected imaging high of the front object lens are 3mm, 6 and 0.5mm. The total number of the imaging fiber bundle are 10000 and it’s pixel cell size is 5 μm. The effective aperture of the imaging fiber bundle is 0.46mm. The post coupling lens has a reduction ratio of 1.73. It’s object distance and imaging height are 5mm and 0.8mm. The Numerical Aperture (NA) of the front object lens, imaging fiber bundle and the post coupling lens are matching will. The coupling efficiency of the imaging fiber bundle is above 93% and the system’s design result can meet the need of the limit resolution of the imaging fiber. This kind of the fiber endoscope has the peculiarity of wide FOV, fine imaging quality, compact configuration, low finished cost and etc. It is meaningful to realize the objective of miniaturization, batch-type production and high imaging quality of the endoscope.

Panoramic camera on the Yutu lunar rover of the Chang'e-3 mission

The change-3 panoramic camera, which is composed of two cameras with identical functions, performances and interfaces, is installed on the lunar rover mast. it can acquire 3d images of the lunar surface based on the principle of binocular stereo vision. by rotating and pitching the mast, it can take several photographs of the patrol area. after stitching these images, panoramic images of the scenes will be obtained. thus the topography and geomorphology of the patrol area and the impact crater, as well as the geological structure of the lunar surface, will be analyzed and studied. in addition, it can take color photographs of the lander using the bayer color coding principle. it can observe the working status of the lander by switching between static image mode and dynamic video mode with automatic exposure time. the focal length of the lens on the panoramic camera is 50 mm and the field of view is 19.7 degrees x 14.5 degrees. under the best illumination and viewing conditions, the largest signal-to-noise ratio of the panoramic camera is 44 db. its static modulation transfer function is 0.33. a large number of ground testing experiments and on-orbit imaging results show that the functional interface of the panoramic camera works normally. the image quality of the panoramic camera is satisfactory. all the performance parameters of the panoramic camera satisfy the design requirements.

Light flow model of coded aperture snapshot spectral imager

Coded aperture snapshot spectral imager (CASSI) based on compressed sensing can capture a three-dimensional (3-D) data cube information in one snapshot without scanning, so it is a kind of novel spectral imaging technique with good prospects. In this paper, the data flow procession of two kind of CASSI were studied, which similarities and differences were depicted. The basic principle of the encoded representation of both spectral information and 2-D spatial information of a scene were presented. The numerical estimation techniques based on the compressive sensing theory were applied to reconstruct 3-D data cube.

Multispectral image compression algorithm based on spectral clustering and wavelet transform

In this paper, a method based on spectral clustering and the discrete wavelet transform (DWT) is proposed, which is based on the problem of the high degree of space-time redundancy in the current multispectral image compression algorithm. First, the spectral images are grouped by spectral clustering methods, and the clusters of similar heights are grouped together to remove the redundancy of the spectra. Then, wavelet transform and coding of the class representative are performed, and the space redundancy is eliminated, and the difference composition is applied to the Karhunen-Loeve transform (KLT) and wavelet transform. Experimental results show that with JPEG2000 and upon KLT + DWT algorithm, compared with the method has better peak signal-to-noise ratio and compression ratio, and it is suitable for compression of different spectral bands.

Design of the relay lens for infrared system coupled with imaging fiber bundle

Relay lens is an important element for infrared system coupled with imaging fiber bundle. According to the basic composition and structural characteristics of infrared system coupled with imaging fiber bundle, this paper put forward the general principle and method of its relay lens design, then a material relay lens has been designed by ZEMAX with definite performance index. It has a working spectral coverage from 3.7μm to 4.8μm, focal length of 33.5mm, magnification of -0.6, linear field of view of 12mm, objective numerical aperture of 0.15. It is objective telecentric and is adapted to the relay of infrared detector and imaging fiber bundle. The total lens has two aspheric surfaces and only four pieces of singlet. Its MTF value is 0.7@17 lp/mm, and distortion is -0.19%. After necessary tolerance analysis and structural design, this relay lens has been fabricated. The optical performances fulfill the design requirements and clear images have been got by this lens. These prove the validity and rationality of the design method. It gives a foundational guidance for such relay lens design.

Research on color constancy computation based on YCbCr color space and gray surface

Color constancy is of important for many computer vision applications, such as image classification, color object recognition, object tracking and so on. But unlike the human visual system, imaging device cannot be able to compute color constant descriptors which do not vary with the color of the illuminant, so solving color constancy problem is necessary. In the calculation of color constancy, illuminant estimation is the key. Because grey surfaces can perfectly reflect the color of the scene illumination, many methods have been proposed to identify grey surfaces to estimate the illuminant. But they either rely on the camera’s parameters, lacking universality, or work inaccurate in worse conditions. In order to solve these problems, in this paper, an iterative method is proposed. The quality of the proposed method is tested and compared to the previous color constancy methods on the Macbeth Chart and two data sets of synthetic and real images. Through MATLAB simulation, experimental pictures and quantitative data for performance evaluation were gotten. The simulated results show that the proposed algorithm is accurate and efficient in identification of the grey surfaces, even in worse condition. And it performs well in color constancy computation on both synthetic and real images.

Color interpolation algorithm of CCD based on green components and signal correlation

Signal CCD/CMOS sensors capture image information by covering the sensor surface with a color filter array(CFA). For each pixel, only one of three primary colors(red, green and blue) can pass through the color filter array(CFA). The other two missing color components are estimated by the values of the surrounding pixels. In Bayer array, the green components are half of the total pixels, but both red pixel and blue pixel components are quarter, so green components contain more information, which can be reference to color interpolation of red components and blue components. Based on this principle, in this paper, a simple and effective color interpolation algorithm based on green components and signal correlation for Bayer pattern images was proposed. The first step is to interpolate R, G and B components using the method-bilinear interpolation. The second step is to revise the results of bilinear interpolation by adding some green components on the results of bilinear interpolation. The calculation of the values to be added should consider the influence of correlation between the three channels. There are two major contributions in the paper. The first one is to demosaick G component more precisely. The second one is the spectral-spatial correlations between the three color channels is taken into consideration. At last, through MATLAB simulation experiments, experimental pictures and quantitative data for performance evaluation-Peak Signal to Noise Ratio(PSNR) were gotten. The results of simulation experiments show, compared with other color interpolation algorithms, the proposed algorithm performs well in both visual perception and PSNR measurement. And the proposed algorithm does not increase the complexity of calculation but ensures the real-time of system. Theory and experiments show the method is reasonable and has important engineering significance.

Design of camera and spectrometer dual-use system

Imaging spectrometers based on prism-grating-prism (PGP) have advantage of direct vision, as a basis for the design of an optical system for a spectrometer and camera dual-use, the system can plug the light splitting element to switch between the spectrometer and camera. This paper has discussed the working principles and structure of the PGP and spectrometer, collimating and focusing lens design principles, then the design result has been presented. The spectral range of the system is 400-800nm, the pixel size of CCD used is 10um × 10um, 1010 × 1018 pixels, the object space numerical aperture is 0.1. In order to reduce the cost and eliminate aberration, collimating lens and focusing lens have symmetric structure, in order to improve the diffraction efficiency, PGP uses the volume phase holographic transmission grating. After optimization the design by ZEMAX software, the whole spectral range resolution is better than 1nm in average, the MTF at Nyquist frequency is greater than 0.7, the length of the whole system is 87mm.

A novel weighted-direction color interpolation

A digital camera capture images by covering the sensor surface with a color filter array (CFA), only get a color sample at pixel location. Demosaicking is a process by estimating the missing color components of each pixel to get a full resolution image. In this paper, a new algorithm based on edge adaptive and different weighting factors is proposed. Our method can effectively suppress undesirable artifacts. Experimental results based on Kodak images show that the proposed algorithm obtain higher quality images compared to other methods in numerical and visual aspects.