Received: 12 May 2017 DOI: 10.1002/mop.30858 Development of an efficient approach for MMW imaging system to identify concealed targets inside the book Bambam Kumar 1 | Prabhat Sharma 2 | Dharmendra Singh 1 1 Department of Electronics and Communication Engineering, Indian Institute of Technology, Roorkee 247667, India 2 Scientist-‘D’, Instrument Research and Development Establishment, Raipur, Dehradun, Uttarakhand, India Correspondence Dharmendra Singh, Department of Electronics and Communication Engineering, Indian Institute of Technology Roorkee, IIT Roorkee, Roorkee 247667, India. Email: dharmfec@gmail.com Abstract The most puzzling task faces by security agency is detec- tion and identification of the targets like, blade, and knife inside the book and capability to differentiate with book mark. Millimeter wave (MMW) imaging system may have good potential for this because of its resolution and pene- tration capability. Therefore, in this paper a statistics based adaptive algorithm is proposed for detection and identifi- cation of targets like blade, knife and book mark inside the book for MMW imaging system. KEYWORDS curve fitting, entropy, MMW imaging, standard deviation, time gating 1 | INTRODUCTION Nowadays detection and identification of concealed targets are taking too much attention by various researchers because of its applications, mainly in security. Every target has unique electromagnetic (EM) signature which depends upon its shape, size, and dielectric property. Researchers have demonstrated several imaging techniques in various EM spectra like, microwave, millimeter wave (MMW), THz, infrared, and X-rays for concealed target detection, medical, and industry application. 1–5 For detection and identification, the system should have good penetration capability with its range and cross range resolution. The range and cross range resolution mainly depends upon the bandwidth and fre- quency of imaging system. 6 Microwave radar imager (3 GHz to 30 GHz) has relatively poor cross range resolution in com- parison to THz and infrared due to its low operating fre- quency. THz imaging system has a limitation of its penetration capability. The infrared imaging techniques attract more attention of researchers due to high spatial reso- lution and harmlessness of human body on the cost of pri- vacy of human and also less standoff distance due to high atmospheric loss. 7,8 MMW imaging system has some trade off among micro- wave, infrared, and THz. Now a days, researchers attract towards active MMW imaging technique for concealed target detection and identification using some image processing techniques. 9 Different techniques has been reported for con- cealed weapon detection and identification using MMW imaging such as compressed sensing, 10,11 polarimetric imag- ing technique. 12 Each of these techniques has advantages as well as limitations such as compressed sensing technique reduces the number of sensors on the cost of large computa- tional time, 11 polarimetric technique can improve detection, and enhance the image by highlighting raised objects, edges and corners but suffers from reducing the reflection from smooth surfaces. 12 Although these techniques are quite com- plex and difficult to process in real time. Therefore, in this paper, an attempt has been made to develop the statistics based detection and identification tech- niques for a concealed targets likes blade, knife, and plastic book mark under various layer of book at any position and orientation. This paper is organized as follows. Section 2 presents the data accusation, Section 3 presents preprocess- ing steps. Section 4 provides statistics based image detection and identification, Section 5 discusses validation of proposed model and Section 6 concludes this paper. 2 | DATA ACQUISTION The targets has been concealed under book at different posi- tion and orientation from a standoff distance of 100 cm from antenna of imaging system. The dimension of book, blade, knife, and plastic book mark are (18 3 16 3 1.5) cm, (4.5 3 2.5) cm, (7 3 3) cm, and (10 3 2.5) cm, respectively. The concealed target under book has been mounted on 2-D wooden movable frame. The movable frame has been moved in horizontal and vertical direction to scan concealed targets. The distance between two consecutive scan positions is kept 1 cm in both horizontal as well as vertical direction. Three type of scanning methodology has been used for data accusa- tion namely, A-scan, B-scan, and C-scan. 6 Total numbers of scanning steps are 16 each in horizontal and vertical direc- tion respectively. Now position of these three targets have 2982 | KUMAR ET AL.