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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.

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.

Sood N.,Defence Electronics Applications Laboratory | Sen P.,Defence Electronics Applications Laboratory
IEEE MTT-S International Microwave and RF Conference 2015, IMaRC 2015 | Year: 2015

This paper describes the design and implementation of phase locked oscillator (PLO) in radio front-end applying a combination of techniques to achieve increased tolerance for withstanding high vibration environment. Elements of a PLO that have been focused upon and optimized include the loop filter parameters such as loop bandwidth and phase margin and the reference oscillator section along with overall mechanical design and packaging. The loop filter of frequency synthesizer is optimized with a trade-off among various parameters and reference oscillator is realized using internal vibration isolators to achieve exceptionally stabilized spectral performance under high vibration condition. © 2015 IEEE.

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 S.D.,Defence Electronics Applications Laboratory | Singh M.P.,Defence Electronics Applications Laboratory | Mishra A.,Defence Electronics Applications Laboratory
2013 IEEE 2nd International Conference on Image Information Processing, IEEE ICIIP 2013 | Year: 2013

The performance of the most popular unsupervised clustering algorithm, k-means depends on the initial seed points. This paper proposes a mode based adaptive seed selection algorithm, which is used to improve the performance of Wishart segmentation for the segmentation of polarimetric synthetic aperture radar images. © 2013 IEEE.

Kushwaha N.K.,Defence Electronics Applications Laboratory | Chaudhuri D.,Defence Electronics Applications Laboratory | Singh M.P.,Defence Electronics Applications Laboratory
Defence Science Journal | Year: 2013

Automatic target detection like oil tank from satellite based remote sensing imagery is one of the important domains in many civilian and military applications. This could be used for disaster monitoring, oil leakage, etc. We present an automatic approach for detection of circular shaped bright oil tanks with high accuracy. The image is first enhanced to emphasize the bright objects using a morphological approach. Then, the enhanced image is segmented using split-and-merge segmentation technique. Here, we introduce a knowledge base strategy based on the region removal technique and spatial relationship operation for detection of possible oil tanks from the segmented image using minimal spanning tree. Lastly, we introduce a supervised classifier, for identification of oil tanks, based on the knowledge database of large amount data of oil tanks. The uniqueness of the proposed technique is that it is useful for detection bright oil tanks from high as well as low resolution images, but the technique is always better for high-resolution imagery. We have systematically evaluated the algorithm on different satellite images like IRS - 1C, IKONOS, QuickBird, and CARTOSAT - 2A. The proposed technique is detected bright structures but unable to detect the dark structure. If the oil tank structures are bright relative to the background illumination in the image then the detection accuracy by the proposed technique for the high resolution image is more than 95 per cent. © 2013, 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.

Arora M.K.,Indian Institute of Technology Roorkee | Bansal S.,Indian Institute of Technology Roorkee | Khare S.,Defence Electronics Applications Laboratory | Chauhan K.,Defence Electronics Applications Laboratory
Defence Science Journal | Year: 2013

Target detection is of particular interest in hyperspectral image analysis as many unknown and subtle signals (spectral response) unresolved by multispectral sensors can be discovered in hyperspectral images. The detection of signals in the form of small objects and targets from hyperspectral sensors has a wide range of applications both civilian and military. It has been observed that a number of target detection algorithms are in vogue; each has its own advantages and disadvantages and assumptions. The selection of a particular algorithm may depend on the amount of information available as per the requirement of the algorithm, application area, the computational complexity etc. In the present study, three algorithms, namely, orthogonal subspace projection (OSP), constrained energy minimization (CEM) and a nonlinear version of OSP called kernel orthogonal subspace projection (KOSP), have been investigated for target detection from hyperspectral remote sensing data. The efficacy of algorithms has been examined over two different hyperspectral datasets which include a synthetic image and an AVIRIS image. The quality of target detection from these algorithms has been evaluated through visual interpretation as well as through receiver operating characteristic (ROC) curves. The performance of OSP algorithm has been found to be better than or comparable to CEM algorithm. However, KOSP outperforms both the algorithms. © 2013, DESIDOC.

Baisantry M.,Defence Electronics Applications Laboratory | Negi D.S.,Defence Electronics Applications Laboratory | Manocha O.P.,Defence Electronics Applications Laboratory
Defence Science Journal | Year: 2012

Change vector analysis is a very sophisticated method to evaluate land-use/land-cover changes meaningfully. By making proper choice of input data in the form of bands (for instance, red, NIR etc) or features (for instance, greenness, brightness, wetness etc), information about both the magnitude as well as the type/nature of changes can be extracted. However, improper selection of thresholds is always a hindrance to a good change detection algorithm. The paper has proposed an improved technique to select threshold appropriately by means of principal component difference and inverse triangular function. The changes have been represented using class-based circular wheel representation. Results have been shown to further testify the performance of proposed algorithm. © 2012, DESIDOC.

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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