Exact ray-tracing computation of narcissus-equivalent temperature difference in scanning thermal imagers

Rayces, Juan L.; Lebich, Lan

doi:10.1117/12.130755

Cited by 7 publications

(3 citation statements)

References 4 publications

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“…(1). Suppose there are m i;j rays that meet the judgement criteria; the cold return of surface S j to field i can be obtained by [2] …”

Section: B Narcissus Calculation Of Single Surfacementioning

confidence: 99%

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Accurate and fast narcissus calculation based on sequential ray trace

Liu¹,

Xiao-bing²,

Zhong³

et al. 2013

Appl. Opt.

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A narcissus calculating method for cryogenic infrared imaging systems is proposed in this paper. The accuracy is largely improved compared to the traditional paraxial analysis, as ray blocking of the optical opertures is taken into account and real ray data are used during the calculation. The narcissus distribution on the full focal plane can be obtained via analyzing field by field. Meanwhile, it can be implemented simply and fast as sequential ray tracing is utilized and rays only pass through three surfaces during the cold return statistics for every retro-reflecting surface. According to this method, a general narcissus calculation package was realized using the macro language of optical design software Code V. The performance of the new method was tested by calculating an example system using this package and comparing it with traditional methods. The results showed that the new method produced the same result accuracy and information quantity as the nonsequential ray trace, while the whole analysis took only 5 s, which was significantly shortened compared with the nonsequential ray trace, which took about 30 min.

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“…(1). Suppose there are m i;j rays that meet the judgement criteria; the cold return of surface S j to field i can be obtained by [2] …”

Section: B Narcissus Calculation Of Single Surfacementioning

confidence: 99%

“…Narcissus is a unique stray light effect of cryogenic infrared imaging systems caused by retro-reflection of optical lens surfaces [1][2][3]. So far there are two main methods for narcissus calculation:…”

Section: Introductionmentioning

confidence: 99%

Accurate and fast narcissus calculation based on sequential ray trace

Liu¹,

Xiao-bing²,

Zhong³

et al. 2013

Appl. Opt.

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“…𝜎 is the surface cold return. This parameter, as defined by Akram [8] S.H.Ashlan [4] 𝜎 = , is the ratio of the solid angle Ω of the radiation reflected back on the detector by surface j, to the detector pixel i cold shield solid angle Ω It is assumed that camera housing and scene radiate as blackbodies, so if M is the total number of rays traced outward starting from the detector pixel 𝑖 and m is the number of rays falling through the cold shield aperture back on to the cooled FPA surface after reflection from the lens surface j, the fraction of the solid angle for pixel i and surface j, 𝜎𝑖𝑗 transferring cold energy from the cooled detector surface to the detector pixel is [13] 𝜎 = m 𝑀…”

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confidence: 99%

Focused Narcissus evaluation in a MWIR zoom system

Rosales,

Moreno Serrano

2024

Optical Design and Engineering IX

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There has been a notable advance in detection systems during the last decades. On one hand, these advances allow the design of systems with higher resolution and better performance, but on the other hand, they are more sensitive to unwanted light. In infrared systems, Narcissus is one of the major problems of unwanted light to avoid. This problem is especially more difficult to control in zoom infrared systems, where there are a considerable number of zoom positions which must be carefully checked to analyze the presence of Narcissus. Usually, Narcissus can be eliminated using an offset nonuniformity correction (NUC) or One Point NUC (OPN). In order to be eliminated through this algorithm, it is necessary that the NITD of the system at all zoom positions is under certain level according to the detector sensitivity. But although the system can fulfill this requirement, we have found situations where Narcissus is highly sharp but still exhibiting low levels of NITD. This sharp Narcissus is not possible to eliminate through OPN. The sharp Narcissus was first found during measurement test and then reproduced through simulations in Zemax. These simulations allowed us to find the root cause of the sharp Narcissus. These findings trigger the need to establish solid requirements to avoid not only Narcissus under certain NITD values, but also focused Narcissus. In this paper we present Narcissus measurements and simulations results, pointing out the root cause for Narcissus, and potential solutions for this problem.

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