PMMW data collection results

Particle filtering has been proved effective for the state estimation of nonlinear and non-Gaussian systems. To solve the problems of sample degradation and depletion in standard particle filtering tracking algorithm, a novel immune particle filtering target tracking method is proposed in Passive Millimeter Wave (PMMW) imaging. Particle filtering provides a framework in which the posterior density of PMMW target state is represented by a weighted sample set. By using the artificial immune algorithm combined with the Mean Shift algorithm, the samples are optimized during the evolution process. To achieve robust description of the PMMW targets, both gray and gradient orientation distributions are taken into account. Besides, the observation density is established by computing the Bhattacharyya distance between the distribution of the target model and that of the candidate. Experimental results demonstrate that the proposed algorithm is superior to traditional ones when tracking scale changing PMMW targets.

As Passive Millimeter Wave (PMMW) imagers mature, users have located them in more and more challenging locations. Because PMMW systems typically use natural sky coldness as a contrast source, indoor installations can become problematic. A number of semi-active illumination systems have been proposed, with various degrees of success. A problem many of them suffer from is reversed contrast - the illumination source is considerably hotter than the ambient scene, causing the cameras to act in unexpected ways. The relatively narrow extent of the illumination source is another problem, with speckle and glint often dominating the image. There are a number of unintended illumination sources in indoor locations, and all are poorly understood. This paper will examine several of them, as well as their polarametric properties, and discuss their effects on image quality.

The purpose of this paper is to propose an algorithm and a novel method for fusion of Passive Millimeter Wave (PMMW) images with their visible images by using Non-subsampled Shearlet Transform (NSST) based on the Spiking Cortical Model (SCM) fusion rule. The parameters of NSST and Improved SCM (ISCM) are selected and optimized based on time consumption and the output of the optimization function like QAB/F. In addition, an effective thresholding method in contourlet transform for PMMW and visible images fusion, which is proposed in our previous paper, is applied to the fusion procedure. Furthermore, NSST is used for analysis of the initial images in different resolutions and directions, followed by using of the ISCM neural network as the fusion rule. Combination of the proposed fusion and thresholding processes resulted in better output images containing visual information close to that of the visible image as well as the hidden object in the millimeter wave image. Moreover, a new evaluation criterion is proposed which does not suffer the shortcomings of the available criteria and improves the previous results for detecting hidden objects by up to 23% with 5% extra time consumption. Finally, the obtained results are evaluated with the available and standard metrics, and all the images exhibited better values than those of the other methods. In fact, the value obtained for the gun image is also acceptable. The results indicate that the proposed fusion method realizes almost all the considered objectives, and the fused image show the objects distinctly in an image with visible details.

A passive millimeter wave (PMMW) camera capable of generating real time displays of the imaged scene, similar to video cameras, has been developed at TRW over the past two years. The camera operates at 89 GHz, has a 15 degree(s) X 10 degree(s) field-of-view, an aperture of 18' diameter, and displays the acquired image at a frame rate of 17 Hz. A major enabling technology is the focal plane array of direct detection MMIC receivers which enables this camera to be reliable and low cost, in addition to providing it with unique operational features. A state-of-the-art W-band passive millimeter wave FPA consisting of 1040 highly integrated direct detection MMIC pixels capable of generating real time images has been developed. We will discuss the assembly and test of high performing, high frequency GaAs MMIC chips in high volume and at low cost. This work reports on progress achieved to date in the development and manufacturing of this new sensor technology.

An aperture synthesis passive millimeter wave (PMMW) imager using 256 antennas with 1 GHz bandwidth is currently under development in Beihang University. This imager is designed for concealed contraband detection on human body in indoor environment at video imaging rate. Design of the digital cross-correlation subsystem is presented in this paper. High-speed clocked comparators are used to perform 1-bit A/D convention, while FPGAs are used to perform further signal processing. The cross-correlation system is split into three parts: 1-bit A/D conversion, data distribution and signal processing. The analog signals from receivers are sampled and distributed to several cross-correlation processors based on FPGA. A sampling scheme performing per-bit deskew and serial-to-parallel conversion and a correlator performing cross-correlation of 128 channels on a signal FPGA are presented in this paper. Test results from a 64-channel test board are also presented, which prove the design works.

Linear Tapered Slot Antennas (TSA) have significant advantages over traditional horn antennas, dielectric rod antenna when used as feed elements in Focal Plane Arrays (FPA) of Passive MilliMeter Wave(PMMW) imaging. In this paper, a novel Antipodal Linear Tapered Slot Antenna(ALTSA) is designed and optimized. The proposed antenna, the gain of which is improved by loading metamaterial structure, is fed by the Substrate Integrated Waveguide(SIW). Simulation and measure analysis show that the good impedance characteristics, low sidelobe levels, high and smooth gain are all achieved in a wide frequency band. Meanwhile, the designed antenna has a smaller aperture width and is easier to form a denser feed array in the focal plane to improve the spatial resolution of passive millimeter wave imaging.

Passive millimeter wave (PMMW) sensors have been proposed as forward vision sensors for enhanced vision systems used in low visibility aircraft landing. This work reports on progress achieved to date in the development and manufacturing of a demonstration PMMW camera. The unit is designed to be ground and flight tested starting 1996. The camera displays on a head-up or head-down display unit a real time true image of the forward scene. With appropriate head-up symbology and accurate navigation guidance provided by global positioning satellite receivers on-board the aircraft, pilots can autonomously (without ground assist) execute category 3 low visibility take-offs and landings on non-equipped runways. We shall discuss utility of fielding these systems to airlines and other users.

<div class="htmlview paragraph">We examine the requirements for on-board aircraft sensor systems that would allow pilots to “see through” poor weather, especially fog, and land and rollout aircraft under conditions that currently cause flight cancellations and airport closures. Three visual aspects of landing and rollout are distinguished: guidance, hazard detection and hazard recognition. The visual features which support the tasks are discussed. Three broad categories of sensor technology are examined: passive millimeter wave (PMMW), imaging radar, and passive infrared (IR). PMMW and imaging radar exhibit good weather penetration, but poor spatial and temporal resolution. Imaging radar exhibits good weather penetration, but typically relies on a flat-earth assumption which can lead to interpretive errors. PMMW systems have a narrow field of view. IR has poorer weather penetration but good spatial resolution. We recommend using both millimeter-wave and infrared sensor systems, blending the images using multiresolution digital-image pyramid-processing technology, and fusing the resulting real-time images with stored database imagery of the same scene.</div>

Single-pixel Passive Millimeter Wave (PMMW) imaging system has drawn much attention for its low cost and low complexity. Nowadays, researchers put more effort into the study of the single-pixel PMMW imaging technology as the wide application of Compressive Sensing technology. Previous studies have indicated that the key of the single-pixel imaging technology is the design of coding template. In most studies, a large number of single-templates are applied for coding sampling. These kinds of methods are not suitable for engineering applications due to their low imaging speed. Therefore, a coding method based on quasi cyclic S matrix is proposed, and a novel coding template is designed to improve the imaging speed in this paper. The algorithms of OMP and TVAL3 simulation results in MaTLAB verity the effectiveness of the proposed method.

Synthetic aperture radiometer imaging use sparse antennas array for reducing the cost.In this process,phase errors of the visibility function will sharply degrade the imaging quality.This paper presents a detailed analysis of system imperfections and a calibration modeling.Meanwhile,we introduce a real time calibration method-Redundant Spacing Calibration(RSC).And its simulation result proves that this calibration method is very efficient under the two kinds of antenna arrays.

A PMMW image denoising based on adaptive manifolds and high-dimensional mean median filter

An algorithm is presented to detect moving targets in Passive Millimeter Wave (PMMW) images with dynamic scenes. This algorithm incorporates the maximum mutual information registration method for background registration, and frame difference method for detection. Experiments' results demonstrate its effectiveness.

Passive millimeter wave (PMMW) imagers are increasingly becoming practical sensor candidates for target detection tasks. This paper is devoted to the ship detection by land-based W band passive polarized imager. The radiation characteristics of sky, sea surface and the atmospheric absorption characteristics of sea area near Qingdao are calculated based on sounding data. And the W band radiation characteristic of painted metal is measured. Then, the experiments of detection for sea surface ship are carried out in different ranges including 2,5, and 15 kilometers. The results show that land-based PMMW imager can detect and locate ship target from sea surface more than tens of kilometers away in thick fog, and polarization selection has influence on detection performance.

In this paper, an autonomous real-time mine detection algorithm based on improved YOLOv5 in a complex underwater environment is proposed. The target recognition system based on the optical image is used to guide autonomous underwater vehicles (AUV) to achieve high precision mine exploration and assist the autonomous mine hunting weapon system to finish the mine-hunting task. In view of all kinds of various interference information of the underwater optical images, a set of image preprocessing systems has been added to the algorithm based on YOLOv5 which has the advantages of both detection accuracy and detection speed. The original data are processed by data enhancement, image enhancement, sample equalization, negative sample addition, and Poisson fusion, which can reduce the problem of poor detection results caused by the input image quality to some extent. At the same time, the number of layers of YOLOv5 is reduced, which makes the detection algorithm meet the requirements of the AUV embedded system without affecting the detection accuracy, and improves the real-time detection of the mobile terminals. The experimental results show that the proposed method could effectively improve the detection accuracy and real-time performance of the underwater mine detection system.

Passive millimeter wave imaging has been shown to be a useful for enhanced vision and concealed weapons detection applications. Trex Enterprises is developing a second generation passive millimeter wave imaging system which operates in real time with a 20 X 30 degree field of view and a 2K temperature sensitivity. This system is based on a pupil-plane aperture architecture used in a first generation system, but also includes advances in technology which improve system performance and utility. These include a flat panel dielectric antenna and W-band amplifiers, detectors, and processors. This second generation system will serve as the basis for a production millimeter-wave imager.