Passive Infrared Field Gradient Analysis and Localization of Thermal Objects in Active Fresnel Zones.

Abstract

The purpose of this research is to present efficient novel techniques in contactless thermal surveillance by devising and developing two prototype Thermal Infrared Field Gradient Detection Scanning Systems by using thermal sensors. Signals from Pyroelectric Infrared (PEIR) sensors based Scanning System-1 are analyzed for recognition of thermal gradient patterns to surveil for thermally contrasted stationary and dynamic objects in multiple active Fresnel zones (AFZs) including subzones. The advantage of surveillance in thermal infrared perspective over the visible spectrum realm lies in the fact that all objects above absolute zero emit thermal radiations, with thermal contrast in an AFZ the gradient can be effectively determined by using multi-element pyroelectric infrared sensors. Another prototype open-air thermal gradient scanning system is developed based on Non-Dispersive Infrared (NDIR) thermopile sensing array. This system is used to steer the trespasser in a quiescent vicinity by the detection of wave flow in the gravity induced carbon dioxide, which causes phase delay in density gradients at three spatial locations. The objective of this research is to analyze the first scanning system for up to four active monitoring Fresnel regions for static thermal gradients caused by thermal absorption or emission by living and non-living things and due to the movement of homeothermic body or its constituents in thermally contrasted regions in 8–14μm wide infrared bandwidth. The second scanning system analyze concentration gradient in 4.26μm narrow-band infrared region. In the first thermal scanning system, the gyratory mask-aperture maps a narrow scanning beam on the pyroelectric sensing elements through each lens of a linear Fresnel lens array. The signals from the system are linear field thermograms that are used for localization and thermal field gradients signatures analysis of stationary and dynamic objects. Discrete multilevel and continuous level thermal field analysis have been performed using three different types of pyroelectric sensors, LHI-968, LHI-1148, LHI- 1128 and NDIR thermopile sensor TPD-2T-0625-G2G20, have been used in the Scanning System-2. Thermal analysis of the pyroelectric sensor, transient and harmonic V mathematical models for the sensors and the systems are also presented to establish theoretical basis and to understand the operation of the systems. Robust Dynamic Time Warping (DTW) and Multiclass Support Vector Machines (MSVMs) algorithms with Sequential Minimal Optimization (SMO) heuristic have been utilized with distinctive lower bounded Short-Time Fourier-Transform (STFT) vector reduction algorithm to abridge recognition time in measuring dynamic distances and feature extraction. In second scanning system the direction of intrusion is determined by numerically estimating Time Difference of Arrival (TDOA) of the wave at three sensing nodes that utilized generalized correlation with phase transform technique. Scanning System-1 has been demonstrated to identify thermal gradient of stationary objects in multiple AFZs and recognized thermal patterns with over 95% true recognition rate using only one pyroelectric sensor. Dynamic objects across Fresnel zones and within sub Fresnel zones and their intermission state have been successfully identified with recognition rate of more than 94% using three pyroelectric sensors. For Scanning System- 2, the steering angle of the source is successfully estimated with recognition rate of more than 92%. Evaluation of these scanning systems shown promising results and the author suggests further research can be made in this field.