Forward Looking Infrared System Research Articles

Evaluation of Range Estimation Performance of FLIR with Field Requirements Criteria

Thermal imaging performance depends on many variables, ranging from the properties of the imaged object to atmospheric transmittance and system parameters. After clarification of the functional needs in system design or procurement, system parameters of the design that can meet these needs should be determined. Diagnosis/recognition from a distance is one of the foremost of these needs. The following briefly introduces the Forward Looking Infrared (FLIR) systems, followed by explanations for calculating the theoretical diagnostic range. After the theoretical information, sample systems are given, and high-performance FLIR systems are presented. To accurately analyze, measure and predict the performance of FLIR systems, a model should calculate summary performance measures of the system in the form of Minimum Resolvable Temperature (MRT) and Modulation Transfer Function (MTF) between a target and its background and estimate range for a given scenario electro-optical required for the performance evaluation of the system. The accuracy of these calculations will ultimately determine the accuracy of the model by which the performance of the FLIR system is evaluated.

Forces and Heat Variation Laws of Pine Materials Processing and Microcosmic Characteristics of Surface Damage

Pinus massoniana material was processed on a shaper in which a quartz three-component dynamometer and forward-looking infrared (FLIR) system were used to measure the cutting forces and cutting zone temperature, respectively. In addition, a high-speed camera and the FLIR systems were used to capture the chip formation process. Cutting forces and cutting zone temperature were measured under the cutting conditions of three different rake angles (25°, 40°, and 50°) and four different cutting depths (0.1 mm, 0.2 mm, 0.3 mm, and 0.5 mm), while feed speed was kept constant. Analysis of the experimental data and chip formation process showed that the cutting forces and cutting zone temperature of pine material were both decreased by increases of rake angle and increased by increases of cutting depth. Cutting forces were decreased under the cutting conditions of 0.3 mm cutting depth and rake angles of 40° and 50° due to the cleavage failure parallel to pine grain. The cutting temperature was not decreased under that cutting condition. The microcosmic characteristics of surface damage were mainly fiber burrs and fiber traces.

Helicopter thermal imaging for detecting insect infested cadavers

One of the most common techniques applied for searching living and even dead persons is the FLIR (Forward Looking Infrared) system fixed on an aircraft like e.g. a helicopter, visualizing the thermal patterns emitted from objects in the long-infrared spectrum. However, as body temperature cools down to ambient values within approximately 24h after death, it is common sense that searching for deceased persons can be just applied the first day post-mortem. We postulated that the insect larval masses on a decomposing body generate a heat which can be considerably higher than ambient temperatures for a period of several weeks and that such heat signatures might be used for locating insect infested human remains.We examined the thermal history of two 70 and 90kg heavy pig cadavers for 21days in May and June 2014 in Germany. Adult and immature insects on the carcasses were sampled daily. Temperatures were measured on and inside the cadavers, in selected maggot masses and at the surroundings. Thermal imaging from a helicopter using the FLIR system was performed at three different altitudes up to 1500ft. during seven day-flights and one night-flight.Insect colonization was dominated by blow flies (Diptera: Calliphoridae) which occurred almost immediately after placement of the cadavers. Larvae were noted first on day 2 and infestation of both cadavers was enormous with several thousand larvae each. After day 14 a first wave of post-feeding larvae left the carcasses for pupation. Body temperature of both cadavers ranged between 15°C and 35°C during the first two weeks of the experiment, while body surface temperatures peaked at about 45°C. Maggot masses temperatures reached values up to almost 25°C above ambient temperature. Detection of both cadavers by thermal imaging was possible on seven of the eight helicopter flights until day 21.

A Model for the Passive Infrared Detection of Naval Targets through FLIR: Model Description and Preliminary Results Applicable in the Eastern Mediterranean Sea

The maritime environment is a very unique system with respect to the environmental conditions that affect the transmission of electromagnetic energy, and especially the part of the spectrum that falls in the infrared band. This paper proposes an end-to-end model for the detection of ships at the environmental conditions of the eastern Mediterranean Sea, with the use of a Forward Looking Infrared (FLIR) system. The model: a) covers the issues regarding the detection and classification of simple model targets in various states of temperature conditions, by applying the Moser and O’Neill criteria, b) takes into account existing environmental conditions, by using data obtained from the Hellenic National Meteorological Service (HNMS) and the British Atmospheric Data Centre (BADC) for the years 2004–05, and c) uses the LOWTRAN 7 code for the calculation of the transmission through the maritime atmosphere. In the calculation of the atmospheric transmission, turbulence is taken into account through the introduction of a Modulation Transfer Function (MTF), to model the specific phenomenon. The FLIR system is also modeled as a series of MTF functions, with each one of those covering the characteristics of major subsystems of the detection device. Finally, the observer’s MTF is included in the model, and the probability of completing the specific task is calculated and presented for a range of observer to target distances.

Diffractive lens in 8- to 10-μm forward-looking infrared system

We realize for the first time a forward-looking IR (FLIR) sys- tem using a diffractive optical element (DOE) in its optics made of ger- manium in the 8- to 10-mm IR wavelength. We describe the design and the performance of the DOE optics. The IR diffractive lens made of ger- manium is proposed to correct the axial chromatic aberration in optics of the FLIR system. Compared with conventional optics of an FLIR system the optics using a DOE singlet instead of ZnSe achromat, we have a DOE system modulation transfer function (MTF) that is almost equal to the conventional one. The DOE singlet instead of ZnSe achromat ap- pears to be enough to compensate for the chromatic aberration of the optical system. Using the DOE system, the numbers of lens elements, the mass, and the cost are reduced. © 2002 Society of Photo-Optical Instrumen- tation Engineers. (DOI: 10.1117/1.1487365)

Mechanically active athermalization of a forward looking infrared system

This study discusses the mechanically active athermalization of a forward looking infrared (FLIR) system. Athermalization is the principle of stabilizing the optical performance with respect to temperature. First optical design for a FLIR system that makes thermal imaging at 8–12 μm band is done using a commercial design and analysis program. Then the optical elements are transferred to a 3D solid modeling program where the housing for the system is designed using the optomechanical engineering principles. Subsequently, all the system with lenses, electronic cards and housing are transferred to a finite element analysis (FEA) software. Initial conditions and obtained results are verified by a laboratory study. After making thermal and structural analysis by FEA software; the temperature distribution, expansions and contractions in the system are determined. These data are used to optimize the system and as a result to ensure the system work at different environmental temperatures.

Infrared image registration and high-resolution reconstruction using multiple translationally shifted aliased video frames

Forward looking infrared (FLIR) detector arrays generally produce spatially undersampled images because the FLIR arrays cannot be made dense enough to yield a sufficiently high spatial sampling frequency. Multi-frame techniques, such as microscanning, are an effective means of reducing aliasing and increasing resolution in images produced by staring imaging systems. These techniques involve interlacing a set of image frames that have been shifted with respect to each other during acquisition. The FLIR system is mounted on a moving platform, such as an aircraft, and the vibrations associated with the platform are used to generate the shifts. Since a fixed number of image frames is required, and the shifts are random, the acquired frames will not fall on a uniformly spaced grid. Furthermore, some of the acquired frames may have almost similar shifts thus making them unusable for high-resolution image reconstruction. In this paper, we utilize a gradient-based registration algorithm to estimate the shifts between the acquired frames and then use a weighted nearest-neighbor approach for placing the frames onto a uniform grid to form a final high-resolution image. Blurring by the detector and optics of the imaging system limits the increase in image resolution when microscanning is attempted at sub-pixel movements of less than half the detector width. We resolve this difficulty by the application of the Wiener filter, designed using the modulation transfer function (MTF) of the imaging system, to the high-resolution image. Simulation and experimental results are presented to verify the effectiveness of the proposed technique. The techniques proposed herein are significantly faster than alternate techniques, and are found to be especially suitable for real-time applications.

An integrated DSP-based architecture for FLIR optical scanning mirror calibration and control

A galvanometric optical scanner in a FLIR (forward looking infrared) system is controlled so as to adhere to a highly linear scan pattern using a DSP-based control architecture. Position sensor scale factor accuracy is calibrated with ten optical feedback loop, position-based FLIR imaging pulses are produced, and diagnostic self-test procedures are run, all with the same DSP used for position control. >

State-of-the-Art for Thermal Imaging

Substantial improvements in the thermal imaging state-of-the-art are occurring in forward-looking infrared (FLIR) system technology. These far infrared imaging systems have achieved broadcast television standards for frame rate, resolution, and signal-to-noise ratio, and are moving toward the standardization and volume production necessary for wider dissemination of the technology. Current techniques permit a single-detector system to approach within a factor of two the theoretical limit of thermal sensitivity using a photon detector. FLIR systems now use mechanical scanners and the mini-mum number of detectors necessary to achieve the needed performance, but performance requirements are increasing, and future systems may use mosaics of self scanned detec-tors. Then problems of element-to-element nonuniformities and of background substraction must be solved.

TV-Compatible Forward Looking Infrared

In this paper we describe a new Forward Looking Infrared (FLIR) development. Two basic types of scanning are presently representative of most FLIR systems, parallel scanning and serial scanning. Historically, the first high performance FLIRs utilized parallel scanning. The recent development of (Hg,Cd)Te detectors has made possible the use of serial scanning. This paper describes a serial scanned TV-compatible FLIR.