Super resolution reconstruction (SRR) improves resolution by increasing the effective sampling frequency. Target acquisition range increases but the amount of increase depends upon the relationship between the optical blur diameter and the detector size. Range improvement of up to 52% is possible. Modern systems digitize the scene into 12 or more bits but the display typically presents only 8 bits. Gray scale compression forces scene detail to fall into a gray level and thereby "disappear." Local area processing (LAP) readjusts the gray scale so that scene detail becomes discernible. Without LAP the target signature is small compared to the global scene dynamic range and this results in poor range performance. With LAP, the target contrast is large compared to the local background. The combination of SRR and LAP significantly increases range performance.

10.1117/12.724482

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Infrared imaging systems: Design, analysis, modeling, and testing; Proceedings of the Meeting, Orlando, FL, Apr. 16-18, 1990

Gerald C. Holst

Recent experimental and theoretical investigations in IR system design, analysis, and modeling are examined in reports and reviews. Topics discussed are modeling second-generation thermal imaging systems, performance improvement of an IR imaging system using subsystem MTF analysis, human recognition of IR images, spatial frequency performance of SPRITE detectors, and optimization of Schottky-barrier IR detectors for solar blindness. IR system testing is also considered, focusing on such problems as tolerancing methodology for an IR optical telescope, system response function approach to minimize IR testing errors, and portable MRTD collimator system for fast in situ testing of FLIRs and other thermal imagers.

Collimator

Source

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Building Envelope Inspection

SPIE eBooks (2000)

Gerald C. Holst

Building envelope inspections are carried out for two specific purposes: (1) quality control of new or retrofitted wall assemblies and (2) existing building condition assessment. The purpose of quality control of new construction is to verify that there are no hidden defects that could result in premature material deterioration. Quality control of new construction is the more difficult task: the thermographer does not have the luxury of visual symptoms of material deterioration or failure. The thermographer has to make assessments and recommendations based on available construction drawings and thermal imagery of assemblies that do not show any visible evidence of problems . This chapter describes heat loss through exterior walls and the next chapter is devoted to roofs. The primary difference is that a roof survey usually relies on the sun to heat entrapped moisture. Since the walls are often shielded from the sun, a temperature difference between the interior and exterior is necessary. This is generally requires heating or cooling the interior. Evaporative cooling can also identify entrapped moisture. Building inspections are usually qualitative.

Building envelope

Envelope (radar)

10.1117/3.2588945.ch13

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Appendix C: Thermal Sensing and Imaging 1980-1999

SPIE eBooks (2000)

Gerald C. Holst

10.1117/3.2588945.ap3

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Image Quality

SPIE eBooks (2017)

Gerald C. Holst

Most system resolution metrics (see Chapter 15, Resolution) are based solely on system parameters. This chapter includes the human visual system (HVS) and therefore displayed contrast is part of image quality metrics. Image quality is a subjective impression, ranking the imagery from poor to excellent. It is somewhat a learned ability. It is a perceptual one, accomplished by the brain, affected by and incorporating other sensory systems, emotions, learning, and memory. The relationships are many and not well understood. Seeing varies between individuals and temporarily within an individual. There exist large variations in an observer’s judgment as to the correct rank ordering from worst to best and therefore image quality cannot be placed on an absolute scale. Visual psychophysical investigations have not measured all the properties relevant to imaging systems.

Observer (physics)

Impression

Rank (graph theory)

10.1117/3.2588947.ch16

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Airborne minefield detection system using IR sensing

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE (1992)

Eugene L. Cloud Herbert A. Duvoisin Michael Inderhees Gerald C. Holst George B. Maksymonko

This paper describes the work completed by Martin Marietta in support of the U.S. Army's standoff minefield detection system, advanced technology transition demonstration. This paper discusses the high priority and urgent need for the standoff mine detection system within the Army Combat Engineers, it presents the results of the successful application of non developmental technology/hardware in an airborne mine/minefield detection system, and it discusses the significant payoff of applying advanced ATR and high speed parallel processing. The technologies discussed include the IR imager as the source of mine imagery, advanced image processing algorithms including neural nets, and a high speed parallel processor unique to Martin Marietta called GAPP (geometric arithmetic parallel processor).

10.1117/12.138085

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Sampling artifacts, system design, and image processing

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE (2007)

Gerald C. Holst

Imaging system resolution depends upon Fλ/d where F is the focal ratio, λ is the wavelength, and d is the detector size. Assuming a 100% fill factor, no aliasing occurs when Fλ/d ≥ 2. However, sampling artifacts are quite acceptable and most systems have Fλ/d < 1. Sampling artifacts are most noticeable with periodic targets (bar patterns, picket fences, plowed fields, etc). Since real targets are aperiodic, the sampling theorem (frequency domain analysis) does not directly provide guidance in algorithm development. Sampling creates an edge location ambiguity of one pixel. Phasing effects and edge ambiguity are often overlooked when designing image processing algorithms.

Aperiodic graph

Aliasing

10.1117/12.747757

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