Third-generation naval IRST using the step-and-stare architecture

Nougues, Pierre-Olivier; Baize, P.; Roland, Flavien; Olivier, J; Renaudat, Mathieu

doi:10.1117/12.773953

Cited by 12 publications

(12 citation statements)

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“…At long range a target is viewed as a point source when its angular subtense is smaller than the instantaneous field-of-view (IFOV) of the system. IRST systems are available in two distinctive spectral bands: mid-wave (MW) from 3 to 5 μm [1,2] and long-wave (LW) from 8 to 12 μm [3]. Many have compared the performance of MWIR IRST with that of LWIR IRST for various cases [4].…”

Section: Introductionmentioning

confidence: 99%

Comparison of IRST systems by SNR

Kim

Meyer

2014

SPIE Proceedings

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Infrared (IR) cameras are widely used in systems to search and track. IR search and track (IRST) systems are most often available in one of two distinct spectral bands: mid-wave IR (MWIR) or long-wave IR (LWIR). Many have compared both systems in a number of ways. The comparison included field data and analysis under different scenarios. Yet, it is a challenge to make a right decision in choosing one band over the other band for a new scenario. In some respects, the attempt is like choosing between an apple and an orange. The signal-to-noise ratio (SNR) of a system for a point-like target is one criterion that helps one to make an informed decision. The formula for SNR commonly uses noise equivalent irradiance (NEI) that requires front optics. Such formalism cannot compare two bands before a camera is built complete with front optics. We derive a formula for SNR that utilizes noise equivalent differential temperature (NEDT) that does not require front optics. The formula is further simplified under some assumptions, which identifies critical parameters and provides an insight in comparing two bands. We have shown an example for a simple case. Keywords: Infrared search and track (IRST), MWIR, LWIR, SNR, NEI INTRODUCTIONThe first goal of an infrared search and track (IRST) system is to detect signatures as far as possible. Signatures of interest may include aircraft, helicopters and missiles. At long range a target is viewed as a point source when its angular subtense is smaller than the instantaneous field-of-view (IFOV) of the system. IRST systems are available in two distinctive spectral bands: mid-wave (MW) from 3 to 5 μm [1, 2] and long-wave (LW) from 8 to 12 μm [3]. Many have compared the performance of MWIR IRST with that of LWIR IRST for various cases [4]. Each has pros and cons. Ideally, both would be used simultaneously to enjoy all the pros. Performance metrics and the weighting of those metrics peculiar to the application often drive the choice.The key metrics for evaluating IRST system performance are signal-to-noise ratio (SNR), resolution and clutter rejection. Clutter rejection is related to the environment such as the sun and clouds. In this paper, we focus on SNR. Further, we exclude any noises due to the scan for search and non-uniformity among the pixels for focal plane array (FPA). It is common to use noise equivalent irradiance (NEI) in defining SNR [5]. NEI, however, depends on the camera system as a whole and is inadequate for comparing MWIR IRST with LWIR IRST when one is interested in making a choice before building the corresponding system with front optics. On the other hand most manufacturers provide noise equivalent differential temperature (NEDT) [6] for both MWIR and LWIR detectors that do not require optical systems during measurement.We introduce the measurement of NEDT and derive its relation to the corresponding temporal noise. The SNR for a point target in the field is obtained by approximating target signature. The signal in SNR means the signal difference between the signal an...

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Section: Introductionmentioning

confidence: 99%

Comparison of IRST systems by SNR

Kim

Meyer

2014

SPIE Proceedings

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“…In the wide-area reconnaissance/search mode, the camera can obtain high-resolution images of the target area efficiently, which requires the aerial reconnaissance cameras to have the characteristics of high resolution and wide coverage. In the surveillance/tracking mode, the camera can obtain the target image and trajectory in real time, which requires the aerial reconnaissance camera to have the characteristics of a high frame frequency and positioning accuracy [ 1 , 2 , 3 , 4 , 5 ]. There are four common aerial camera imaging modes: staring imaging, linear array scanning imaging, step and stare imaging, and dynamic scan and stare imaging [ 6 , 7 , 8 , 9 , 10 , 11 ].…”

Section: Introductionmentioning

confidence: 99%

Conceptual Design and Image Motion Compensation Rate Analysis of Two-Axis Fast Steering Mirror for Dynamic Scan and Stare Imaging System

Sun

Ding

Zhang

et al. 2021

Sensors

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In order to enable the aerial photoelectric equipment to realize wide-area reconnaissance and target surveillance at the same time, a dual-band dynamic scan and stare imaging system is proposed in this paper. The imaging system performs scanning and pointing through a two-axis gimbal, compensating the image motion caused by the aircraft and gimbal angular velocity and the aircraft liner velocity using two two-axis fast steering mirrors (FSMs). The composition and working principle of the dynamic scan and stare imaging system, the detailed scheme of the two-axis FSM and the image motion compensation (IMC) algorithm are introduced. Both the structure and the mirror of the FSM adopt aluminum alloys, and the flexible support structure is designed based on four cross-axis flexural hinges. The Root-Mean-Square (RMS) error of the mirror reaches 15.8 nm and the total weight of the FSM assembly is 510 g. The IMC rate equations of the two-axis FSM are established based on the coordinate transformation method. The effectiveness of the FSM and IMC algorithm is verified by the dynamic imaging test in the laboratory and flight test.

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“…The third-generation IRST systems utilize the FPAs with step/stare imaging to achieve wide area coverage. The new IRST achieves greater performances than the previous generation thanks to their staring nature, i.e., to longer integration times (milliseconds rather than microseconds) [3][4][5][6][7][8].…”

Section: Introductionmentioning

confidence: 99%

“…They also suffer from more false alarms [2].The third-generation IRST systems utilize the FPAs with step/stare imaging to achieve wide area coverage. The new IRST achieves greater performances than the previous generation thanks to their staring nature, i.e., to longer integration times (milliseconds rather than microseconds) [3][4][5][6][7][8].In step/stare imaging applications, a high-resolution narrow FOV sensor is rapidly stepped or indexed across an area of interest, stopping at intervals to stare and collect imagery. Then the images at each location are stitched together to form a large but high-resolution image.…”

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confidence: 99%

Non-Rotationally Symmetric Field Mapping for Back-Scanned Step/Stare Imaging System

Xin

Zhang

et al. 2020

Applied Sciences

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Step/stare imaging with focal plane arrays (FPAs) has become the main approach to achieve wide area coverage and high resolution imaging for long range targets. A fast steering mirror (FSM) is usually utilized to provide back-scanned motion to compensate for the image motion. However, the traditional optical design can just hold one field point relatively stable, typically the central or on-axis field point, on the FPA during back-scanning; all other field points may wander during the exposure due to imaging distortion characteristics of the optical system, which reduces the signal to noise ratio (SNR) of the target. Aiming toward this problem, this paper proposes a non-rotationally symmetric field mapping method for the back-scanned step/stare imaging system, which can make all field points stable on the FPA during back-scanning. First of all, the mathematical model of non-rotationally symmetric field mapping between object space and image space is established. Then, a back-scanned step/stare imaging system based on the model is designed, in which this non-rotationally symmetric mapping can be implemented with an afocal telescope including freeform lenses. Freeform lenses can produce an anamorphic aberration to adjust distortion characteristics of the optical system to control image wander on an FPA. Furthermore, the simulations verify the effectiveness of the method.

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Third-generation naval IRST using the step-and-stare architecture

Cited by 12 publications

References 0 publications

Comparison of IRST systems by SNR

Comparison of IRST systems by SNR

Conceptual Design and Image Motion Compensation Rate Analysis of Two-Axis Fast Steering Mirror for Dynamic Scan and Stare Imaging System

Non-Rotationally Symmetric Field Mapping for Back-Scanned Step/Stare Imaging System

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