Qunbo Lv

Sub-block PCA-wavelet image sharpening approach for hyperspectral images

One of the most crucial issues to judge image quality is the spatial resolution. Hyperspectral image (HSI) sharpening is the process of combining spatial information to enhance spatial resolution of HSIs. Huge volumes of HSI data cause difficulties during the sharpening process. This paper proposed a practical and effective strategy to deal with HSI sharpening. We utilized sub-block method and combined PCA and wavelet fusion approaches to achieve the proposed scheme. Sub-block method helped reduce the calculation complexity and promote the efficiency. PCA and wavelet image sharpening contributed to enhance spatial resolution of HSI with less spectral distortion. The experiment demonstrated an efficient processing result and a good visualized effect. Qualitative and quantitative assessments were both used to evaluate the proposed approach.

Spectral calibration of the coded aperture spectra imaging system

Coded aperture spectroscopy allows for sources of large field to be efficiently coupled into dispersive spectrometers by replacing the traditional input slit with a patterned mask. Spectral calibration is requisite for spectroscopy to obtain the spectrum information exactly. In this paper, we described the spectral calibration’s principle and methods of coded aperture spectral imaging, and then gave the results of the experiment using a monochromatic extended source, at last we tested the accuracy of spectral calibration. The results indicate that this method can calibrate the coded aperture imaging spectrometer with high accuracy.

Applications of CS based spectrum recovery in hyperspectral images

In this paper, we consider the question regarding high spectral redundancy in hyperspectral image (HSI) which causes problems of storage as well as transmission. Efficient spectrum sampling and recovery approaches are needed. This paper addresses the application of compressed sensing (CS) based spectrum recovery in spectra and HSIs. We firstly analyze the sparsity of spectra. Then we design the appropriate processes of spectrum recovery from efficiency and speed aspects. The proposed strategy was tested using the spectral data from USGS dataset and an AVIRIS HSI data. The experiments demonstrate that it results in a high reconstruction rate and low mean square errors compared with traditional interpolation method. Besides, the reconstructed HSIs have been applied into target detection to show the feasibility and applicability, illustrating the spectrum recoverys superiority.

Multi-mode computing optical imaging technology based on software definition micro-nano satellite

In order to accomplish the software definition micro-nano satellite demands, which includes that its payload functions and parameters could be reconstructive and controllable by uploading software as needs, we have to break through the design limitations between traditional satellite platform and ordinary optical camera, one new type of optical imaging camera technology is developed based on software definition micro-nano satellite here. we gave full consideration to the possible development joint designing space between the software and the hardware of the payload. Then we analyze the influence of sub-pixel information, satellite platform parameters, optical system parameters, detector parameters, noise and atmosphere on image data processing, especially the super-resolution reconstruction. we establish the physical model and the error model according to the physical mechanism of each factor, as a priori information of the reconstruction method, we apply these prior information constraints in favor of super-resolution to the design of the camera, enabling the images captured by the camera to match the super resolution method very well. This method can simultaneously improve visual resolution and substantial resolution, while maintaining the ability of suppressing noise and may reduce the size and development difficulty of traditional cameras. At the same time, we also carry out high dynamic range imaging technology based on the definition of CMOS software, which assists multi frame image superposition, and fit in the image processing algorithm, breaking through the digital dynamic range enhancement technology, and realizing the ability of high dynamic range clear imaging over high performance CCD. We have developed a general purpose computing optical imaging camera, which integrates the super resolution imaging, dynamic range enhanced imaging, video imaging and other multi intelligent controllable imaging modes. Finally we have completed the related camera integration, testing and experiment.

Multispectral image enhancement processing for microsat-borne imager

With the rapid development of remote sensing imaging technology, the micro satellite, one kind of tiny spacecraft, appears during the past few years. A good many studies contribute to dwarfing satellites for imaging purpose. Generally speaking, micro satellites weigh less than 100 kilograms, even less than 50 kilograms, which are slightly larger or smaller than the common miniature refrigerators. However, the optical system design is hard to be perfect due to the satellite room and weight limitation. In most cases, the unprocessed data captured by the imager on the microsatellite cannot meet the application need. Spatial resolution is the key problem. As for remote sensing applications, the higher spatial resolution of images we gain, the wider fields we can apply them. Consequently, how to utilize super resolution (SR) and image fusion to enhance the quality of imagery deserves studying. Our team, the Key Laboratory of Computational Optical Imaging Technology, Academy Opto-Electronics, is devoted to designing high-performance microsat-borne imagers and high-efficiency image processing algorithms. This paper addresses a multispectral image enhancement framework for space-borne imagery, jointing the pan-sharpening and super resolution techniques to deal with the spatial resolution shortcoming of microsatellites. We test the remote sensing images acquired by CX6-02 satellite and give the SR performance. The experiments illustrate the proposed approach provides high-quality images.

An image sharpening strategy based on multiframe super resolution for multispectral data

Spatial resolution is one of the most important assessments to evaluate an image. Enhancing spatial resolution consequently becomes a hot issue. As is all known, multispectral (MS) image, which is widely studied in remote sensing (RS) field, can be fused with the corresponding high-resolution panchromatic image to promote spatial-quality. In this paper, we consider the question regarding how to enhance the spatial resolution of multispectral image in the case that we do not have high-resolution panchromatic image. The only inputs are the MS data and the same spatial-resolution multi-frame panchromatic image. This paper addresses the application of super-resolution (SR) reconstruction technique and provides a suggestion for MS image sharpening. We generate a high-resolution panchromatic image based on SR. Then we adjust it and the low-resolution MS image into the same size. At last, we fuse them via a hybrid image sharpening technique. Experiments demonstrated an effective processing result and a good performance.

Lightweight design and finite element analysis of primary mirror for the space telescope

In order to satisfy the strict requirements of the lightweight ratios and high dimensional stability for space mirror, the design method of lightweight structure and the flexible supporting structure of the primary mirror is proposed. Subsequently, the surface deformations of two different lightweight structures for primary mirror are discussed for analyzing the influence of the mirror weight on its surface. Finally, the finite element models for primary mirror assembly are built for calculating the surface deformation caused by different gravity orientations and various thermal environments. It is proved that the weight, stiffness and surface accuracy of the structure design for primary mirror can meet the engineering requirement.

Analysis for simplified optics coma effection on spectral image inversion of coded aperture spectral imager

As a novel spectrum imaging technology was developed recent years, push-broom coded aperture spectral imaging (PCASI) has the advantages of high throughput, high SNR, high stability etc. This coded aperture spectral imaging utilizes fixed code templates and push-broom mode, which can realize the high-precision reconstruction of spatial and spectral information. But during optical lens designing, manufacturing and debugging, it is inevitably exist some minor coma errors. Even minor coma errors can reduce image quality. In this paper, we simulated the system optical coma error’s influence to the quality of reconstructed image, analyzed the variant of the coded aperture in different optical coma effect, then proposed an accurate curve of image quality and optical coma quality in 255×255 size code template, which provide important references for design and development of push-broom coded aperture spectrometer.

Optical system design of the snapshot imaging spectrometerusing image replication based on Wollaston prism

Imaging spectral is a novel detection approach which simultaneously acquires two-dimensional visual picture and one-dimensional spectral information.The imaging spectrometer not only provides abundant data for aeronautics and astronautics remote sensing, but also offers promising applications on biomedical imaging, conservation and identification of art works,surveillance of food safety,prevention and control of plant diseases and elimination of pests,and so forth. In this paper, the snapshot imaging spectrometer using image replication based on Wollaston prisms is designed. This system includes the telescope objective, the collimator lens, the wave plates, Wollaston prisms, and the imaging lens.The imaging spectrometer system based on multi-configuration can obtain a high diffraction efficiency. Every configuration provide a kind of wave. The 16 configurations are in one mechanical structure. The system’s MTF at 56 line pairs is better than 0.75. The RMS of the spots are all in one pixel.The imaging spectrometer can obtain perfect data.

Geometric superresolution by using a two-dimensional orthogonal encoding mask

In many modern optical systems, the resolution is limited not only by the diffraction caused by physical dimensions of the optics lens, but also by the CCD’s nonzero pixel size. Especially for the traditional incoherent illumination, the restriction of CCD pixel is greater than that of optical diffraction. Here we develop a novel approach to enhancing resolution beyond the limit set by CCD’s pixels, in which a two-dimensional and orthogonal encoding mask is attached before the imaging lens to modulate frequency on input target spectrum. Here we focus on the design about a 4f optical imaging system, considering the ability of Fourier transformation to achieve the equivalent conversion between space and frequency domain. And to prevent the loss of frequency in the overlapping regions when sampled by classical CCD, there must be some proportion between the spatial range of object plane and corresponding frequency plane. Meaning while, the wavefront aberration of Fourier lens needs to be controlled to fulfill the mathematical features of Fourier transformation. We apply to improving and revising the theoretical design for the encoding mask based on the design limit of opticalmechanical engineering, and we analyze the different orthogonal forms of encoding masks which can bring the spectra diffraction to the imaging area. According to the theoretical discussion, revision and algorithm simulation, the results in the preliminary testing system show that the encoding mask can be used to produce enhancement of resolution by a factor of 2 in-exchange for decreasing the field of view by the same factor.