Design and first results of a Fourier Transform imaging spectrometer in the 3-5 μm range

International audienceAn imaging spectrometer in the 3-5 μm wavelength range is presented. This wavelength range reveals important information about scenes such as gas or landmine detection, but the amount of light is usually low and signal to noise ratio is a real issue. We selected a Fourier transform (FT) configuration, expecting an advantage in signal to noise ratio in the presence of detector noise. Radiometric and noise models are summarized. A Michelson interferometer with its mirrors replaced by twin mirrors arranged at right angles in a hollow roof was chosen for its nearly straight equidistant fringes localized at infinity. Because in such FT-based spectral imagers, the interferogram is acquired over the whole field of the camera while the scene of interest scans the path difference range, vignetting should be strongly limited while keeping the size of the interferometer as small as possible for manufacturability and cost reasons. The key point for that purpose is to put the entrance pupil of the imaging lens inside the interferometer and to make careful trade-offs between lens F number and angular field of view. The resulting system has a spectral resolution of about 25cm^-1 that fulfils the requirement for most targeted applications. Examples of absorption bands detection are shown

Noise sources in imaging static Fourier transform spectrometers

International audienceImaging static Fourier transform spectrometers are well-adapted instruments for remote sensing. However, the path from the raw images to the spectral images is quite long, thus multiplying the potential noise sources. In this article, we propose to review these perturbation sources. We first recall how detector or photon noise on the interferogram affects the estimated spectrum. Then, we focus on inhomogeneities of the focal plane array. Although these inhomogeneities are deterministic, they generate noise when they are ill-corrected. Finally, we describe defects due to errors that may occur during the image processing step. We also give some avenues to limit the impact of these noises

Genetic counselling difficulties and ethical implications of incidental findings from array-CGH: A 7-year national survey

International audienceMicroarray-based comparative genomic hybridization (aCGH) is commonly used in diagnosing patients with intellectual disability (ID) with or without congenital malformation. Since aCGH interrogates the whole genome, there is a risk of being confronted with incidental findings (IF). In order to anticipate the ethical issues of IF with the generalization of new genome-wide analysis technologies, we questioned French clinicians and cytogeneticists about the situations they have faced regarding IF from aCGH. Sixty-five IF were reported. Forty corresponded to autosomal dominant diseases with incomplete penetrance, 7 to autosomal dominant diseases with complete penetrance, 14 to X-linked diseases, and 4 were heterozygotes for autosomal recessive diseases with a high prevalence of heterozygotes in the population. Therapeutic/preventive measures or genetic counselling could be argued for all cases except 4. These 4 IF were intentionally not returned to the patients. Clinicians reported difficulties in returning the results in 29% of the cases, mainly when the question of IF had not been anticipated. Indeed, at the time of the investigation, only 48% of the clinicians used consents mentioning the risk of IF. With the emergence of new technologies, there is a need to report such national experiences; they show the importance of pre-test information on IF

Toxicologie predictive: les voies du futur

National audienc

Toxicologie predictive: les voies du futur

National audienc