A W-band auto-focus holographic imaging system for security screening

Abstract

Millimeter-wave Holography is a promising technique for security screening to detect concealed weapons. However, a crucial disadvantage of this technique is that the close-range large-aperture operation result in a very short depth of focus. In this paper, a W-band auto-focus holographic imaging system is presented. By calculating and comparing the amplitude integral value of holographic imaging results reconstructed at different focusing distances, the algorithm can assess focusing quality of each imaging result, choose the optimal focusing distance, and extract the optimum viewing image from the imaging results. The scheme of imaging system is described in detail. Both simulation and experimental results are provided to demonstrate that the focusing performance of new auto-focus imaging system is much better than conventional holographic system.

Impacts of phase-locked loop bandwidth on millimeter wave three-dimensional imaging system

“…Then the obtained I and Q signals are digitized by highspeed analog to digital converter (ADC), and finally the image-reconstruction algorithm is applied to rebuild the MMW images. The imaging resolution is mainly dependent on the frequency and bandwidth of the transmitting signals [4,10]. Once the frequency is selected, an effective method to raise resolution is to increase SNR of the system.…”

“…MMW imaging systems have been widely used for concealed weapon detection at security checkpoints during the recent years [1,2,3,4]. Practical application of these systems needs to be improved [5].…”

“…The SNR of imaging system with different bandwidths.IEICE Electronics Express, Vol.16, No.11,[1][2][3][4][5][6] …”

$V$- and $W$-Band Millimeter-Wave GaN MMICs

“…Security screening for weapon detection is currently used at Ka-band frequencies, but also at 92 GHz, e.g. [10]. Imaging and gesture detection has been shown commercially from a Google Soli device at 60 GHz [11] and is being developed at 94 GHz [12].…”

An Accurate Millimeter-Wave Imaging Algorithm for Close-Range Monostatic System

“…It is noted that the scattering data are the convolution of reflectivity function and Green’s function in spatial domain, which can be more efficiently handled as the multiplication of their Fourier transforms in the wavenumber domain and converted back through FFT technique. Therefore, many efficient wavenumber-domain algorithms have been developed, such as the holographic algorithm [ 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 ], range Doppler (RD) algorithm [ 31 , 32 ], chirp scaling (CS) algorithm [ 33 , 34 ], and range migration algorithm (RMA) [ 35 , 36 , 37 ], among which the holographic algorithm has been being heavily studied for its proven commercial potential. In particular, monostatic configuration is often assumed for simplicity and efficiency.…”