A number of studies suggest that the Short Wave InfraRed (SWIR) band (0.9-1.7μm), offers a significant advantage over the visible for long-range daytime scenarios. This advantage of SWIR is due in particular to its excellent optical penetration in the presence of aerosols thanks to reduced light-scattering effects, allowing good scene contrast to be maintained over very long distances. This study reports the results of a field evaluation campaign, involving Lynred’s SNAKE TECLESS (TL) sensor (640x512@15μm, InGaAs) along size narrow field optics. This year-long campaign features a variety of atmospheric conditions, weathers and aerosol types. Those targets are at distances ranging between 10km and 84km. Finally, we compare the image obtained with SWIR sensors having a pixel pitch of 15μm and 10μm, with the same objective lenses, in order to conclude on the interest of reducing the pixel pitch for a gain in range.
We present an innovative optical particulate matter sensor. This optical sensor ‘on-a-chip’ combines a visible fibered light source and a custom-made CMOS image sensor chip. By illuminating a single particle in an air channel, we can record the light scattering signature on the photodiode matrix. A piece realized in 3D printing achieves fiber alignment and an efficient stray light protection.
A specific scattering pattern occurs from the interaction of light with a single particle. Unlike traditional optical PM sensors based on a single photodiode detection, we measure a lens-free projection of the scattering signature on the nearby image sensor (1.5mm projection distance). This allows us to count particles and determine their size and refractive index. These parameters are retrieved through image processing and by comparison with a radiometric model that calculates the projection of a Lorenz-Mie’s scattering pattern.
We describe the sensing technique, the architecture and fabrication of this sensor as well as the characterization results, which are in good agreement with our theory-based predictions. In particular, we show that it is possible to differentiate calibrated particulates of different sizes (monodisperse polystyrene-latex spheres). The sensor is sensitive enough to detect single particle and smallest than 1μm.
We present our latest advances in the field of miniature optical particulate matter sensors. By illuminating a single particle in an air channel, one can record the light scattering signature with a CMOS image sensor and then classify particles. This signature is optically pre-processed with an advanced, millimeter-sized, monolithic, refracto-reflective optical system. It performs notably a Fourier transform with very wide field of view of scattering angles, and includes as well integrated fluidics and alignment. Functional prototypes were fabricated using laser micro machining on glass, selective polishing, and were replicated with epoxy resin using a molding process.
We present several integrated technologies on Silicon, from visible to mid-infrared, for particulate matter and gas detection. We present new concepts to detect in the visible particulate matter with a high sensitivity and a discrimination of both particle sizes and refractive indices. For gas detection, mid-infrared technologies developments include on one hand, microhotplate thermal emitters, as a cheap solution for gas sensing, eventually enhanced by plasmonics, and on the other hand quantum cascade lasers-based photoacoustic sensors, for high precision measurement, and for which the integration on Silicon is pushed forward for a reduction of costs.
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