A critical limitation imposed on all imaging systems is to achieve an optimal balance between optical resolution and bandwidth. The optical system determines and affects the relations between temporal information, spatial bandwidth, and resolution, so the resulting signal may differ for each wavelength. This is of significant importance for hyperspectral imaging in particular, because it extracts both spatial and temporal wavelength information. We present a dispersive device that can be used for hyperspectral imaging hypercube image measurements. We utilize the Vernier effect by integrating two silicon slabs that act together as a modified Fabry–Perot filter. The transition between wavelength bands is achieved by heating, utilizing the thermo-optic effect. Importantly, we show that red-shifting with concatenated slabs requires less heating than with a single slab. With the presented technique, a wide effective free spectral range of up to 90 nm around a central wavelength of 1550 nm was achieved along with 20-nm full-width-at-half-maximum resolution. With the same configuration, observing a narrower 0.7-nm free spectral range bandwidth, a fine spectrum resolution of 0.07 nm was obtained. Such variety covers most of the spatial and temporal standard limitations of current hyperspectral imaging requirements.
In attempt to supply a reasonable fire plume detection, multinational cooperation with significant
capital is invested in the development of two major Infra-Red (IR) based fire detection alternatives,
single-color IR (SCIR) and dual-color IR (DCIR). False alarm rate was expected to be high not only as a
result of real heat sources but mainly due to the IR natural clutter especially solar reflections clutter.
SCIR uses state-of-the-art technology and sophisticated algorithms to filter out threats from clutter.
On the other hand, DCIR are aiming at using additional spectral band measurements (acting as a
guard), to allow the implementation of a simpler and more robust approach for performing the same
In this paper we present the basics of SCIR & DCIR architecture and the main differences between
them. In addition, we will present the results from a thorough study conducted for the purpose of
learning about the added value of the additional data available from the second spectral band. Here
we consider the two CO<sub>2</sub> bands of 4-5 micron and of 2.5-3 micron band as well as off peak band
(guard). The findings of this study refer also to Missile warning systems (MWS) efficacy, in terms of
operational value. We also present a new approach for tunable filter to such sensor.
In this paper we present an all-optical silicon modulator, where a silicon slab (450 μm) thick is coated on both sides to get a Fabry-Perot resonator for laser beam at wavelength of 1550nm. Most of the modulators discussed in literature, are driven by electrical field rather than by light. We investigate new approaches regarding the dependence of the absorption of the optical signal on the control laser pulse at 532 nm having 5nm pulse width. Our silicon based Fabry-Perot resonator increases the intrinsic c-Si finesse to >10, instead of the uncoated silicon with natural finesse of 2.5. The improved finesse is shown to have significant effect on the modulation depth using a pulsed laser. A modulation of 12dB was attained. The modulation is ascribed to two different effects - The Plasma Dispersion Effect (PDE) and the Thermo- Optic Effect (TOE). The PDE causes increase in the signal absorption in silicon via the absorption of the control laser light. On top of that, the transmission of the signal can decrease dramatically in high finesse resonators due to change in the refractive index due to TOE. The changes in the signal's absorption coefficient and in the refractive index are the result of incremental change in the concentration of free carriers. The TOE gives rise to higher refractive index as opposed to the PDE which triggers a decrease in the refractive index. Finally, tradeoff considerations are presented on how to modify one effect to counter the other one, leading to an optimal device having reduced temperature dependence.
An evolving combat arena poses an ever-growing hostile fire threat for various ground and airborne targets. Protecting both static posts and moving military platforms against these threats require high performance and affordable solutions, favoring uncooled sensing alert technologies. By analyzing accumulated target and clutter data using new algorithmic and hardware building blocks we establish improved hostile fire indication system configurations. The paper will review new system demonstrations harnessing uncooled IR sensors technology alongside empirical field testing results.
A passive IR approach for stationary system is introduced providing protection to high value infrastructure
and strategic areas by detecting and warnings against fire shot from rifles, carbines, sub-machines and various
other small arms - SWAD.
SWAD provides protected surroundings in which it remotely detects small arms fire. By analyzing their
patterns, including duration and intensity, SWAD classifies the type of weapon being used.
Infrared staring sensors used in a large field of view (panoramic) applications such as IRST and MWS are still in need for specialized figures of merit to bridge the gap between feasible laboratory measurements and specification and actual performance. Imaging applications has so far dominated the industry attention and so the need to examine the applicability of conventional analyzing concepts and testing procedures for the new applications was overlooked. In this paper we present a universal test station for panoramic MWS/IRST sensors, designed by Elisra and built by CI-Systems Inc. Following the description of the test station configuration, a set of measurable figures of merit and corresponding test procedures that were devised by the authors to support a panoramic sensor specification are introduced. The figures of merit, replacing conventional resolution, sensitivity and pointing accuracy mapping concepts are suggested and explained as viable alternative to the analogous imaging sensors measurement concepts.