Measuring the performance of a cathode ray tube (CRT) or liquid crystal display (LCD) is necessary to enable end-to-end system modeling and characterization of currently used high performance analog imaging systems, such as 2nd Generation FLIR systems. If the display is color, the performance measurements are made more difficult because of the underlying structure of the color pixel as compared to a monochrome pixel. Out of the various characteristics of interest, we focus on determining the gamma value of a display. Gamma quantifies the non-linear response between the input gray scale and the displayed luminance. If the displayed image can be corrected for the display’s gamma, an accurate scene can be presented or characterized for laboratory measurements such as MRT (Minimum Resolvable Temperature) and CTF (Contrast Threshold Function). In this paper, we present a method to determine the gamma to characterize a color display using the Prichard 1980A photometer. Gamma corrections were applied to the test images for validating the accuracy of the computed gamma value. The method presented here is a simple one easily implemented employing a Prichard photometer.
This paper details the development, experimentation, collected data and the results of research designed to gain an
understanding of the effects of clutter on the temporal and spatial image collection guidelines for tracking urban vehicles.
More specifically, a quantitative understanding of the relationship between human observer performance and the spatial
and temporal resolution is sought. Performance is measured as a function of the number of video frames per second,
imager spatial resolution and the ability of the observer to accurately determine the destination of a moving vehicle target
as it encounters vehicles with similar infrared signatures. The research is restricted to data and imagery collected from
altitudes typical of modern low to mid altitude persistent surveillance platforms using a wide field of view. The ability
of the human observer to perform an unaided track of the vehicle was determined by their completion of carefully
designed perception experiments. In these experiments, the observers were presented with simulated imagery from Night Vision's EOSim urban terrain simulator. The details of the simulated targets and backgrounds, the design of the experiments and their associated results are included in this treatment.
Real MWIR Persistent Surveillance (PS) data was taken with a single human walking from a known point to different tents in the PS sensor field of view. The spatial resolution (ground sample distance) and revisit rate was varied from 0.5 to 2 meters and 1/8th to 4 Hz, respectively. A perception experiment was conducted where the observer was tasked to track the human to the terminal (end of route) tent. The probability of track is provided as a function of ground sample distance and revisit rate. These results can help determine PS design requirements for tracking and back-tracking humans on the ground. This paper begins with a summary of two previous simulation experiments: one for human tracking and one for vehicle tracking.
This paper details the development, experimentation, collected data and the results of research designed to gain an understanding of the temporal and spatial image collection guidelines for tracking urban vehicles. More specifically, a quantitative understanding of the relationship between human observer performance and the spatial and temporal resolution is sought. Performance is measured as a function of the number of video frames per second, imager spatial resolution and the ability of the observer to accurately determine the destination of a moving vehicle target. The research is restricted to data and imagery collected from altitudes typical of modern low to mid altitude persistent surveillance platforms using a wide field of view. The ability of the human observer to perform an unaided track of the vehicle was determined by their completion of carefully designed perception experiments. In these experiments, the observers were presented with simulated imagery from Night Vision's EOSim urban terrain simulator. The details of the simulated targets and backgrounds, the design of the experiments and their associated results are included in this treatment.
Third generation FLIR sensors, comprised of 2-D focal plane arrays with simultaneous LWIR/MWIR detection capability, are to be fielded in the near future and are expected to play an important role in future Army sensor applications. NVESD has an effort underway to produce a simulation package that will bring Third Generation FLIR sensor performance to training and wargaming applications. This simulation product provides a wide variety of targets and backgrounds, both rural and urban, for different seasons, times of day, and atmospheric conditions and is built on the existing NVESD LWIR simulation package named NV EOSim. A sensor effects package, which is part of the simulation, uses standard NVTherm sensor decks to accurately simulate the noise, diffraction, resolution, and other design features of individual sensors. The physics of the simulation and the key Third Generation FLIR characteristics incorporated are discussed in detail.
Previous analysis of ground-to-ground 3rd Generation FLIR performance (Driggers, et al<sup>1</sup>) showed two main
performance characteristics of the 3<sup>rd</sup> Gen sensor's MWIR and LWIR bands: first, that no major differences in
detection range were observed between the two bands, and second, that a significant ID range advantage for the
MWIR band over the LWIR band resulted from the smaller diffraction spot of the shorter wavelength MWIR. That
analysis predicted performance for a variety of atmospheric transmittances but only at a single, relatively low value
of atmospheric turbulence. In this paper, analysis of the effect of varying turbulence shows that increased
turbulence decreases the ID range performance of the MWIR relative to the LWIR, and that at high turbulence
values the two bands have roughly equivalent performance. Further, the LWIR band actually surpasses the ID range
performance of MWIR at high turbulence for some systems. Frequency of occurrence data collected in multiple
environments shows a predominance of moderate to high turbulence conditions in the real world. The superior ID
range performance of the MWIR is thus achievable only under limited real-world conditions, and the LWIR can
surpass the performance of the MWIR in significant scenarios (desert, day). For maximum performance under a
variety of conditions the dual band capability of 3rd Gen FLIR systems is thus required.
IR detector integration time is determined by a combination of the scene or target radiance, the noise of the sensor, and the sensor sensitivity. Typical LWIR detectors such as those used in most U.S. military systems can operate effectively with integration times in the microsecond region. MWIR detectors require much longer integration times (up to several milliseconds) under some conditions to achieve good Noise Equivalent Temperature Difference (NETD). Emerging 3rd Generation FLIR systems incorporate both MWIR and LWIR detectors. The category of sensors know as uncooled LWIR require thermal time constants, similar to integration time, in the millisecond range to achieve acceptable good NETD. These longer integration times and time constants would not limit performance in a purely static environment, but target or sensor motion can induce blurring under some circumstances. A variety of tasks and mission scenarios were analyzed to determine the integration time requirements for combinations of sensor platform movement and look angle. These were then compared to the typical integration times for MWIR and LWIR detectors to establish the suitability of each band for the functions considered.
This paper describes the modeling of multispectral infrared sensors. The current NVESD infrared sensor model, NVTherm, models single spectral band sensors. The current NVTherm model is being updated to model third generation multispectral infrared sensors. A simple model for the target and its background radiance is presented here and typical results are reported for common materials. The proposed target radiance model supports band selection studies. Spectral atmospheric propagation modeling is accomplished using MODTRAN. Example radiance calculations are presented and compared to data collected for validation. The data supports rejecting the null hypothesis that the model is invalid.
Radiometric calibration of military IR test equipment is an approach being explored to avoid perceived shortcomings of traditional thermometric calibration. This issue has profound impact on the testing of military systems: the lack of internally consistent calibration architecture can cost military customers millions of dollars in increased maintenance and spares costs due to test result inconsistencies. An example is presented to show that the lack of a standard spectral response definition in this region, and the difficulty in making such a definition, make the radiometric calibration approach seem questionable for the foreseeable future. Calibration errors of more than 7% (not even a worst-case scenario) can result. The best approach to assuring test accuracy and calibration consistency is to employ thermometric calibration in conjunction with intelligent test system design: high, flat spectral transmittance of the test system and high emissivity targets and sources. These are achievable today with proper application of existing materials and coatings.
The paper deals with the feasibility study and use of advanced composite materials in the Low Altitude Navigation and Targeting Infrared for Night (LANTIRN) program's field-test equipment. Emphasis is placed on thermal expansion in the optical test-equipment structure under elevated-temperature conditions. A design approach using a low-CTE graphite/epoxy composite for the optical bed is considered, and based on several constraints, four basic design approaches are evaluated: honeycomb, separated plate, machine solid, and thin solid. A prototype system is covered, and the test results of coupon samples of the composite baseplate material indicate that CTE is less than 1 ppm/deg C over a wide temperature range.