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Kumar A.,Defence Electronics Applications Laboratory | Jassal B.S.,Graphic Era University
Defence Science Journal | Year: 2015

Standoff detection of concealed threat, using millimeter wave radiometer, is being experimented worldwide for enhancing the frame rate and detection probability, as an alternative to personnel frisking, for enhancing passenger service rate and avoiding exposure to harmful radiations. The development of 94 GHz Dicke radiometer and experimentation to bench mark its operational parameters like spatial sampling rate, scan rate and dwell time for the detection of concealed threat, under the fabrics of a human is described. The experimentation provided operational methodology and imaging phenomenology in a given background for the detection of metallic threats. The experimental results have established that radiometer can be considered as an alternate to frisking of personnel and celebrities at public places for security reasons. © 2015, DESIDOC.

Porwal S.,Defence Electronics Applications Laboratory
Defence Science Journal | Year: 2013

Three-dimensional visualization of the geographic data using a digital globe model has been an integral part of a modern GIS system. The visualization of the digital globe model presents many challenges not found in traditional terrain visualization system. The representation of the digital earth (globe) model is important to efficiently render the geographical data without any distortion either at equator or Polar Regions. This paper presents a uniform scheme for efficient quad tree based level-of-details (LOD) representation of the digital globe to minimize the distortion at Polar Regions and meets the requirement of fast frame rate rendering. © 2013, DESIDOC.

Chaudhuri D.,Integration Center | Porwal S.,Defence Electronics Applications Laboratory
Defence Science Journal | Year: 2014

Low contrast and noisy image limits the amount of information conveyed to the user. With the proliferation of digital imagery and computer interface between man-and-machine, it is now viable to consider digital enhancement in the image before presenting it to the user, thus increasing the information throughput. With better contrast, target detection and discrimination can be improved. The paper presents a sequence of filtering operations in frequency and spatial domains to improve the quality of the thermal infrared (IR) images. Basically, two filters - homomorphic filter followed by adaptive Gaussian filter are applied to improve the quality of the thermal IR images. We have systematically evaluated the algorithm on a variety of images and carefully compared it with the techniques presented in the literature. We performed an evaluation of three filter banks such as homomorphic, Gaussian 5×5 and the proposed method, and we have seen that the proposed method yields optimal PSNR for all the thermal images. The results demonstrate that the proposed algorithm is efficient for enhancement of thermal IR images. © 2014 DESIDOC.

Singh V.K.,Defence Electronics Applications Laboratory
IET Microwaves, Antennas and Propagation | Year: 2010

This study presents the design of a micromachined microstrip patch antenna at Ka-band frequencies. The design of the antenna is based on selective lateral etching by micromachining techniques to enhance the performance of a microstrip patch antenna on silicon (Si) substrate. In this design, the silicon material is removed laterally underneath the radiating patch to provide a cavity that consists of a combination of air and substrate in a defined ratio. The effect of the cavity is to produce a low effective dielectric region around the patch. The test results show superior performance over conventional designs where the bandwidth and efficiency have increased by as much as 50 and 25%, respectively. © 2010 The Institution of Engineering and Technology.

Chaudhuri D.,Defence Electronics Applications Laboratory
Defence Science Journal | Year: 2013

More and more images have been generated in digital form around the world. There is a growing interest in finding images in large collections or from remote databases. In order to find an image, the image has to be described or represented by certain features. Shape is an important visual feature of an image. Searching for images using shape features has attracted much attention. There are many shape representation and description techniques in the literature. Object classification often operates by making decisions based on the values of several shape properties measured from an image of the object. Shape analysis is a useful tool for recognition of an object. This paper treats various aspects that are needed to solve shape matching problems: choosing the precise problem of global contour and region based shape analysis, selecting the properties of the similarity measure that are needed for the problem and choosing the specific similarity measure to compute the similarity. © 2013, DESIDOC.

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