Real-time concealed-object detection and recognition with passive millimeter wave imaging

Abstract

Millimeter wave (MMW) imaging is finding rapid adoption in security applications such as concealed object detection under clothing. A passive MMW imaging system can operate as a stand-off type sensor that scans people in both indoors and outdoors. However, the imaging system often suffers from the diffraction limit and the low signal level. Therefore, suitable intelligent image processing algorithms would be required for automatic detection and recognition of the concealed objects. This paper proposes real-time outdoor concealed-object detection and recognition with a radiometric imaging system. The concealed object region is extracted by the multi-level segmentation. A novel approach is proposed to measure similarity between two binary images. Principal component analysis (PCA) regularizes the shape in terms of translation and rotation. A geometric-based feature vector is composed of shape descriptors, which can achieve scale and orientation-invariant and distortion-tolerant property. Class is decided by minimum Euclidean distance between normalized feature vectors. Experiments confirm that the proposed methods provide fast and reliable recognition of the concealed object carried by a moving human subject.

Hidden Object Detection and Recognition in Passive Terahertz and Mid-wavelength Infrared

“…In [21], Martinez presented effective but timeconsuming method based on non-local means (NLM) and iterative steering kernel regression (ISKR) for denoising and local binary fitting (LBF) for segmentation. Yeom proposed a method using global and local segmentation, a Gaussian mixture model with parameters initialised using vector quantisation [22] and additional k-means clustering [23]. A method proposed by Agarwal et al [24] uses a mean standard deviation-based segmentation technique.…”

A W-Band Radiometer with the Offset Parabolic Antenna for Radiometric Measurements

“…For the common 12-bit and 16-bit ADCs, the settling time is integrator with a cutoff frequency of 20 kHz. In addition, a step of 30% of full-scale voltage is caused by the injected noise on top of the receiver noise, and the obtained settling time is approximately 0.17 ms by inserting the above parameters into (9). Thereafter, the duty cycle should be less than 0.33 considering that the switching frequency of the noise source is 1 kHz.…”

“…As the ceramic weapons and the plastic explosive cannot be detected by conventional metal detection techniques, MMW radiometric imaging is increasingly being seen for personnel screening applications [6,7]. And an accurate radiometric measurement of interested items is also necessary to evaluate the performances of MMW imaging systems and to offer database for the contraband items detection, classification, and identification [8,9].…”

Multiview three-dimensional reconstruction by millimetre-wave portable camera

“…For example, it is usual to classify the systems as passive or active depending on if they require emitting or not some kind of wave. Among passive systems , radiometers are able to capture the spontaneous radiation of bodies at a given temperature by using high gain antennas 5, 6 so that information of small spots can be collected yielding the final image. In general, these setups have been used to image in the range of tens of metres due to the distance required by the involved large antennas to focus the scene.…”