Orthogonal array based millimeter-wave (MMW) holographic imaging supports fully electronical scan with a small number of receiving and transmitting antennas.However,due to the sparse array design,the resulting images suffer from serious side gating artifacts,especially for the near-field imaging scenario.In this paper,a total variance (TV) regularized reconstruction algorithm is proposed for orthogonal array based MMW holographic imaging.By introducing a priori TV constraint,the side gating artifacts in the near-field imaging can be eliminated with guaranteed resolution.FEKO electromagnetic simulations are performed to verify the proposed method.The imaging results show that the proposed TV regularized reconstruction algorithm for orthogonal array imaging can obtain images comparable to the results from monostatic mode with 1％ of antennas only.The side gating artifacts are almost completely reduced.

Automatic Target Recognition (ATR) technology is of great significance in security inspection, while traditional object detection methods are proved not efficient in human body millimeter-wave images. In this paper, we propose a synthetic objection detection method for millimeter-wave images. We choose saliency, SIFT and HOG features to form image descriptors. According to sparse representation, the features are encoded again and fed to a linear SVM for target/non-target classification. Previous works proved that the amount of training samples would influence the efficiency of SVM classifiers. Thus, we utilize several simulating methods for data augmentation, aiming to increase the number of training samples before training linear SVM classifiers. The experimental results show that our approach is efficient in target detection of human body millimeter-wave images. Moreover, classifiers trained on larger sets with simulated samples have better performance in classification on our testing dataset.

Direct millimeter-wave (MMW) holographic imaging, which provides both the amplitude and phase information by using the heterodyne mixing technique, is considered a powerful tool for personnel security surveillance. However, MWW imaging systems usually suffer from the problem of high cost or relatively long data acquisition periods for array or single-pixel systems. In this paper, compressive sensing (CS), which aims at sparse sampling, is extended to direct MMW holographic imaging for reducing the number of antenna units or the data acquisition time. First, following the scalar diffraction theory, an exact derivation of the direct MMW holographic reconstruction is presented. Then, CS reconstruction strategies for complex-valued MMW images are introduced based on the derived reconstruction formula. To pursue the applicability for near-field MMW imaging and more complicated imaging targets, three sparsity bases, including total variance, wavelet, and curvelet, are evaluated for the CS reconstruction of MMW images. We also discuss different sampling patterns for single-pixel, linear array and two-dimensional array MMW imaging systems. Both simulations and experiments demonstrate the feasibility of recovering MMW images from measurements at 1/2 or even 1/4 of the Nyquist rate.

Millimeter-wave holographic imaging system can acquire 3D images and is nonionzing, which especially fits human imaging. Widely utilized linear antenna arrays provide high scanning speed as well as non-uniformity artifacts. In this paper, we developed a set of calibration methods and image denoising algorithms to eliminate the influences of system errors including response non-uniformity, transmission delay and background scattering. The experimental results prove that the calibration methods contribute to non-uniformity reduction. The denoising algorithm is efficient in eliminating the disturbances of artifacts related to sub-sampling.

The utility model discloses millimeter-wave holographic scanning three-dimensional imaging equipment. The equipment comprises a first millimeter-wave receiving and transmitting module; a second millimeter-wave receiving and transmitting module; a first guide-rail device, wherein the first millimeter-wave receiving and transmitting module can be connected to the first guide-rail device in a manner of sliding movement; a second guide-rail device, wherein the second millimeter-wave receiving and transmitting module can be connected to the second guide-rail device in the manner of sliding movement; and a driving device which is used for driving the first millimeter-wave receiving and transmitting module to move along the first guide-rail device, and/or driving the second millimeter-wave receiving and transmitting module to move along the second guide-rail device, wherein first and second scanning respectively carried out by the first millimeter-wave receiving and transmitting module and the second millimeter-wave receiving and transmitting module are both flat scanning. The equipment provided by the utility model can improve the scanning speed and accuracy, simplify the scanning operation, and improve the application flexibility of equipment.

硬X射线调制望远镜(Hard X-ray Modulation Telescope,HXMT)的最重要的工作模式是扫描观测,包括巡天扫描观测和小天区深度扫描观测. HXMT的标准成像需要被观测天区完整的二维扫描观测数据,而同时利用HXMT的观测数据中包含的空间调制信息和旋转调制信息,快视成像可以在只有一维扫描的情况下获得被观测天区的较粗略的流强分布,从而可以在卫星的视场扫过一块天区后很快给出被观测天区的尽可能多的信息.本文详细介绍了快视成像的过程,并通过模拟计算给出了巡天扫描观测快视成像的灵敏度、定位精度和角分辨能力的分布.快视成像能提高HXMT发现暂现源的灵敏度,及时发现并定位出现在HXMT视场中的高能爆发现象,减少较强的暂现源和爆发对标准成像干扰将是标准成像的重要补充.

We develop a new procedure to improve the angular resolution of coded-mask telescopes by the Direct Demodulation Method (DDM). DDM has been applied to both real and simulated data of INTEGRAL/IBIS. The angular resolution of IBIS/ISGR1 has been improved from about 13' to 2'.

The most popular iteration method used in Direct Demodulation Method (DD) is Richardson- (RL) Iteration. The formula of RL iteration can be rewritten in matrix form. There are two matrix multiplications which contain the main computation cost. They can be transformed into convolution if the system is shift-invariant. As is well known, convolution can be computed by Fast Fourier Transform much faster than computed directly. This paper introduces the details of the above procedure, which is called accelerated direct demodulation method (ADD), and applies the procedure to image restorations of Hard X-ray Modulation Telescope data. This paper also compares the computation cost between the original DD and ADD.