Triangle orientation discrimination: the alternative to minimum resolvable temperature difference and minimum resolvable contrast

Bijl, Piet; Valeton, J. M.

doi:10.1117/1.601904

Cited by 68 publications

(27 citation statements)

References 22 publications

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“…7 Fundamentally, TOD is similar to MRT in that the result is a curve of minimum contrast versus target size. However, there are several key differences between the two metrics.…”

Section: Todmentioning

confidence: 96%

“…Despite its deep entrenchment in the infrared community, numerous shortcomings of MRT have been cited repeatedly. 2,3,4,5,6,7 Two main focal points of criticism are the subjective nature of the test and the periodic test pattern, which exacerbates aliasing phenomena when evaluating under-sampled imagers. However, another weakness of MRT testing that has been ignored thus far in industry literature is the implicit assumption that imaging performance is static over the course of the test.…”

Section: Mrtmentioning

confidence: 99%

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TOD versus MRT when evaluating thermal imagers that exhibit dynamic performance

et al. 2003

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While it is universally recognized that image quality of a thermal sensor is a strong function of spatial uniformity, the metrics commonly used to assess performance do not adequately measure the effectiveness of non-uniformity correction (NUC). Image uniformity is generally not static, particularly if correction terms are updated intermittently (with periodic shuttering) or gradually (with scene-based NUC). Minimum Resolvable Temperature (MRT), the most prevalent test for characterizing overall imaging performance, is poorly suited for characterizing dynamic performance. The Triangle Orientation Discrimination (TOD) metric proposed by Bijl and Valeton, because of its short observation window, provides better capability for evaluating sensors that exhibit non-negligible uniformity drift. This paper compares the effectiveness of MRT and TOD for measuring dynamic performance. TOD measurements of a shutter-based thermal imager are provided immediately after shutter correction and 3 minutes later. The drift in TOD performance shows excellent corre lation to drift in system noise. BACKGROUNDJust five years ago, achieving noise equivalent temperature difference (NEdT) of 100 mK with an uncooled detector was considered a daunting challenge; today, several uncooled cameras tout sensitivity below 25 mK . Furthermore, pixel sizes have been continuously shrinking while focal plane array (FPA) formats have grown larger. As a result of the rapid progress, the uncooled infrared community places considerable attention on these three attributes -temporal NEdT, pixel size, and array format. Indeed, these parameters have emerged as de facto criteria by which uncooled systems are compared and judged. Unfortunately, these criteria completely neglect spatial uniformity (also called spatial noise) as a component of image quality. Consequently, the importance of effective NUC is often disregarded despite experimental evidence that spatial noise is in fact more detrimental to overall performance than temporal. 1 A more complete method of evaluating a Forward Looking Infrared (FLIR) system is MRT, which is commonly held as the best measure of overall imaging performance. One of the positive attributes of MRT is that it includes spatial noise in the assessment of performance. However, this advantage is undermined by the fact that no standard methods have been defined for adequately representing true NUC effectiveness when measuring MRT. For example, there are no definitive guidelines prescribing how often to update NUC terms when evaluating a system that periodically employs a shutter-based correction or how to handle performance drift between updates. Furthermore, MRT test conditions are poorly suited for assessing systems that use scenebased NUC, and there are no defined procedures for resolving this issue either. So while MRT does not completely disregard spatial noise, it does not always capture true performance in real-world conditions. Therefore, results can be very deceiving.Significant resources are being directed by the ...

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“…7 Fundamentally, TOD is similar to MRT in that the result is a curve of minimum contrast versus target size. However, there are several key differences between the two metrics.…”

Section: Todmentioning

confidence: 96%

Section: Mrtmentioning

confidence: 99%

TOD versus MRT when evaluating thermal imagers that exhibit dynamic performance

et al. 2003

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“…Instead of a test chart consisting of characters, we decided to utilize test charts consisting of triangular optotypes according to the "triangle orientation discrimination" (TOD) method. 12 TOD is a common method to characterize the performance of electro-optical systems. Triangular optotypes oriented in four possible orientations (up, down, left, or right) are presented to observers, which have to indicate the triangle orientation.…”

Section: Pattern Recognitionmentioning

confidence: 99%

Evaluation of protection measures against laser dazzling for imaging sensors

Ritt

Eberle

2017

Opt. Eng

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Abstract. We present our work regarding the evaluation of protection measures against laser dazzling for imaging devices. Different approaches for the evaluation of dazzled sensor images are investigated to estimate the loss of information due to the dazzle spot: (1) counting the number of overexposed pixels, (2) based on triangle orientation discrimination, and (3) using the structural similarity index. The evaluation approaches are applied on experimental data obtained with two different sensors hardened against laser dazzling. The hardening concept of the first sensor is based on the combination of a spatial light modulator and wavelength multiplexing. This protection concept allows spatially and spectrally resolved suppression of laser radiation within the sensor's field-of-view. The hardening concept of the second sensor utilizes the principle of "complementary bands." The optical setup resembles a common three-chip camera, with the difference that dedicated filters with steep edges replace the regular spectral band filters. Although this concept does not really represent a "protection measure," it allows the sensor to provide information even in laser dazzling situations. The data for the performance evaluation were acquired both in a laboratory setup using test charts comprising triangles of different size and orientation as well as in field trials. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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“…Instead of characters, we decided to utilize triangular test patterns according to the triangle orientation discrimination (TOD) method developed by the Netherlands Organisation for Applied Scientific Research. 16 TOD is a common method to characterize the performance of electro-optical systems. Triangular test patterns that can be oriented in four possible orientations (up, down, left, or right) and are presented to observers who have to indicate the triangle orientation.…”

Section: Performance Assessment Of Laser Protectionmentioning

confidence: 99%

Protection performance evaluation regarding imaging sensors hardened against laser dazzling

et al. 2015

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Abstract. Electro-optical imaging sensors are widely distributed and used for many different purposes, including civil security and military operations. However, laser irradiation can easily disturb their operational capability. Thus, an adequate protection mechanism for electro-optical sensors against dazzling and damaging is highly desirable. Different protection technologies exist now, but none of them satisfies the operational requirements without any constraints. In order to evaluate the performance of various laser protection measures, we present two different approaches based on triangle orientation discrimination on the one hand and structural similarity on the other hand. For both approaches, image analysis algorithms are applied to images taken of a standard test scene with triangular test patterns which is superimposed by dazzling laser light of various irradiance levels. The evaluation methods are applied to three different sensors: a standard complementary metal oxide semiconductor camera, a high dynamic range camera with a nonlinear response curve, and a sensor hardened against laser dazzling. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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Triangle orientation discrimination: the alternative to minimum resolvable temperature difference and minimum resolvable contrast

Cited by 68 publications

References 22 publications

TOD versus MRT when evaluating thermal imagers that exhibit dynamic performance

TOD versus MRT when evaluating thermal imagers that exhibit dynamic performance

Evaluation of protection measures against laser dazzling for imaging sensors

Protection performance evaluation regarding imaging sensors hardened against laser dazzling

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