Human and algorithmic imaging performance in the presence of speckle

Optical Engineering · 2026-02-23

In support of target recognition and tracking, we seek to compare the effects of speckle on human observation of moving objects with those of fixed-pattern spatial noise and Gaussian temporal noise through a dynamic minimum resolvable contrast (DMRC) test. In addition, a simple motion tracker algorithm built with a Kalman filter allows for a point of comparison between human and machine perception of speckled imagery. The results of the DRMC test show that speckle causes a greater degradation in observer performance than either temporal or fixed-pattern spatial noise, strongly correlated with target spatial frequency. The results from the simple motion tracker also show that speckle acts as neither temporal nor fixed-pattern spatial noise, and the ability to clearly track a speckled target is dependent upon the relative sizes of target and speckle diameter, which furthers the argument that speckle cannot be simply treated as conventional noise in an incoherent imaging system. Such outcomes will help inform the design and implementation of future active electro-optical systems that perform target recognition and tracking with coherent illumination.

Active imaging radiometry—not always 1/R ²

Applied Optics · 2026-03-09

In this paper, we derive general expressions for the signal-to-noise ratio (SNR) of active imaging systems that employ range-dependent illuminator divergence control and receiver zoom configurations. Many practical systems adjust both parameters with range, causing the received focal-plane power to deviate from the standard 1/ R 2 dependence used in conventional radiometric calculations. We show that, with an appropriate choice of receiver zoom configuration, the SNR becomes independent of range, aside from range-dependent atmospheric transmission. To illustrate these principles, we analyze a laser-range-gated imaging system that implements illuminator divergence control with two receiver zoom configurations: constant-f/# and constant aperture size. We frame the analysis as a radiometric tutorial for both resolved and unresolved targets. Ultimately, we show that the optimal configuration combines range-dependent illuminator divergence control with a constant-f/# zoom configuration. These results inform design considerations and performance requirements for active imaging systems.

Coherent imaging performance: noise-equivalent angle validation

2025-05-30

Design and Simulation of Metalens Arrays for Enhanced MWIR Imaging Array Performance

Journal of Electronic Materials · 2025-06-29 · 3 citations

Abstract Emerging flat optical components based on single layers of metamaterials and metasurfaces have introduced a new approach to microlens arrays. These components hold promise for seamless integration with narrow-bandgap semiconductor-based infrared focal plane arrays, aiming to increase operating temperatures and improve imaging sensitivity. This study focuses on the design and rigorous coupled-wave analysis-based simulation of dielectric-transmissive metalens arrays, specifically tailored to optimize the performance of mid-wavelength infrared imaging arrays. Both Si and Ge metalenses are modeled and compared to spherical lenses, with Ge requiring a smaller aspect ratio than Si due to its higher refractive index, simplifying fabrication. Simulations demonstrate that pixel-registered flat metalenses achieve focusing efficiencies comparable to conventional spherical lenses by reducing the pillar pitch to 1 µm, improving phase profile accuracy and minimizing high-order diffraction losses. These findings highlight the potential of customized metalenses to advance infrared imaging technology and provide practical insights for optimizing imaging array performance through integration with microlens arrays.

Assessing UAV flight dynamics using platform-mounted sensor MTFs

2025-05-29

For field-deployed sensors, it's essential to measure the MTF under actual operational conditions. This is particularly important when the sensor is mounted on a moving platform like a UAV. Factors such as mechanical vibrations, flight dynamics, and flight path linear motions affect system performance and result in blurred imagery. Different UAV types, like vertical takeoff and landing (VTOL) and fixed-wing platforms, experience varying degrees of motion blur. These platforms operate at high speeds which causes the performance to be limited by linear motion blur. It is also not possible to directly measure the component MTFs of the three main factors of motion blur for these platforms. To isolate the effects of the platform, the measured MTF is corrected for linear motion blur by dividing out the component linear motion MTF. This corrected system MTF can then be compared to the static field MTF to evaluate performance degradation. This comparison aids in optimizing sensor systems designed for specific UAV platforms and quantifying platform stability.

Performance characterization of electronic FMCW active imagers

Applied Optics · 2025-09-05 · 1 citations

In an electronic frequency-modulated continuous-wave active imager (eFMCW), the intensity of the transmitted signal is modulated with a chirped frequency, and the received echo is demodulated using a copy of the original modulation pattern (local oscillator). Using this system design technique, the target's distance and range-dependent velocity are simultaneously recoverable. In this study, the signal-to-noise ratio (SNR) and range precision of a notional eFMCW active imager are modeled and compared with two additional range-resolving imaging techniques. The results of this modeling show that eFMCW is a promising system design technique due to its increased sensitivity and range precision when compared to similar methods. These findings assist in motivating the development of a prototype eFMCW imager, which is also presented in this study.

Fixed pattern noise impact on pilotage sensor performance

2025-05-29

Resolution and sensitivity of superband sensors

2025-05-30

Active imaging with a mercury-cadmium-telluride avalanche photodiode versus a commercial-off-the-shelf camera at 1.645 μm

Optical Engineering · 2025-06-19

Active imaging techniques can provide an increased signal-to-noise ratio over passive imaging approaches, particularly in the reflective infrared bands (NIR, SWIR, and eSWIR) where passive solar illumination is reduced relative to the visible band, and cloud cover and time of day can further reduce available illumination. However, providing sufficient illuminator power at long range can introduce severe size, weight, and power trade-offs for system designers, as the strength of the illumination scales proportionally to the inverse square of the illuminator-to-target distance (for a resolved laser spot). Active systems must therefore use illuminator photons efficiently. Avalanche photodiodes (APDs) offer high gain in the electron domain, allowing the detection of a small number of photons by boosting the signal above the floor imposed by read noise. Using both experimental data and modeling, we compare the contrast-to-noise ratio performance of a mercury-cadmium-telluride APD camera and a commercial-off-the-shelf InGaAs SWIR camera with an illuminator at 1.645 μm as a function of illuminator power. Radiometric NVIPM modeling of the sensors is presented and compared to the measured data.

Scene contrast temperature in two different climates

Applied Optics · 2025-08-27

Scene contrast temperature (SCT) is a measurement of temperature and photon flux variation in an emissive scene used to calculate targeting task performance, a metric used to determine the ability of an observer to perform visual tasks. While previous research has compared the SCT of midwave infrared (MWIR) and longwave infrared (LWIR) systems in a hot, dry climate, little work has been done to compare the performance of these systems in different climates. This paper compares the SCT of a hot, dry climate and a cold, dry climate in MWIR and LWIR. The results indicate that SCT is higher in the LWIR in most conditions, except for cold, daylight environments.