Utilisation d’une lame de Savart pour un système de projection de franges interférométriques pour la mesure de forme 3D

Conference (2009, November 18)

Non-contact optical measurement methods are essential tools in many industrial domain. Hololab developed an original out of plane, in line and almost common path interferometer based on polarization ... [more ▼]

Non-contact optical measurement methods are essential tools in many industrial domain. Hololab developed an original out of plane, in line and almost common path interferometer based on polarization states separation using a coated prism for fringes projection. This setup has proven efficient in the field of arts and archaeology but does not meet the demands of the industrial world. Above the acquisition speed and the post treatment process, one of the disadvantages comes from the sensitivity of the system to the environment. To overcome this disadvantage, the coated prism is substituted by a Savart plate. This device has already been used in another field of optical metrology as a shearing device. Many advantages of the prism substitution are discussed and recorded fringes patterns will be shown. [less ▲]

Daytime light exposure dynamically enhances brain responses.

in Current Biology (2006), 16(16), 1616-21

In humans, light enhances both alertness and performance during nighttime and daytime [1-4] and influences regional brain function [5]. These effects do not correspond to classical visual responses but ... [more ▼]

In humans, light enhances both alertness and performance during nighttime and daytime [1-4] and influences regional brain function [5]. These effects do not correspond to classical visual responses but involve a non-image forming (NIF) system, which elicits greater endocrine, physiological, neurophysiological, and behavioral responses to shorter light wavelengths than to wavelengths geared toward the visual system [6-11]. During daytime, the neural changes induced by light exposure, and their time courses, are largely unknown. With functional magnetic resonance imaging (fMRI), we characterized the neural correlates of the alerting effect of daytime light by assessing the responses to an auditory oddball task [12-15], before and after a short exposure to a bright white light. Light-induced improvement in subjective alertness was linearly related to responses in the posterior thalamus. In addition, light enhanced responses in a set of cortical areas supporting attentional oddball effects, and it prevented decreases of activity otherwise observed during continuous darkness. Responses to light were remarkably dynamic. They declined within minutes after the end of the light stimulus, following various region-specific time courses. These findings suggest that light can modulate activity of subcortical structures involved in alertness, thereby dynamically promoting cortical activity in networks involved in ongoing nonvisual cognitive processes. [less ▲]

Narrow band-width wavelength filter by guided mode resonance

in Optical Engineering : The Journal of the Society of Photo-Optical Instrumentation Engineers (2004), 43(11), 2631-2639

Simple resonant structures that permit holographic reflection filtering are studied. The filters under study work under a 45-deg incidence for a wavelength of λ=632.8 nm, a condition useful for future ... [more ▼]

Simple resonant structures that permit holographic reflection filtering are studied. The filters under study work under a 45-deg incidence for a wavelength of λ=632.8 nm, a condition useful for future inclusion in substrate mode systems. First, the influence of the structural parameters of the grating and the waveguide on the position and the shape of the resonance peaks are studied by numerical computation. The numerical results, obtained within the rigorous coupled wave theory, are compared with the measured response of some filters. These filters contain a grating recorded by holography deposited on the substrate. In the case of the bilayer filter, a waveguide is introduced between the grating and the substrate. Second, the numerical results are used for the conception of an active substrate mode spectral filter built from electro-optic zinc oxide. [less ▲]

Achromatic four quadrants phase mask coronagraph using the dispersion of form birefringence

in Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series (2003, February 01)

We describe an alternative design for the 4-quadrant phase mask coronagraph described recently by Rouan et al. 2000. Based on the same principle, i.e. producing a very efficient nulling by mutually ... [more ▼]

We describe an alternative design for the 4-quadrant phase mask coronagraph described recently by Rouan et al. 2000. Based on the same principle, i.e. producing a very efficient nulling by mutually destructive interferences of the coherent light from the main source, our mask realises the pi phase shift using some properties of ZOGs (Zeroth Order Gratings) and according to an original scheme respecting the 4-quadrant symmetry. When the period of the one-dimension grating structure is smaller than the wavelength of the incident light, the structure becomes birefringent. The effective refractive indices depend on the wavelength. Using this feature, we can design a mask whose nulling e±ciency is maintained within a wide wavelength range. Numerical simulations were made according to the RCWT (Rigorous Coupled Wave Theory). [less ▲]