Imaging systems that combine a phase mask in the pupil and digital postprocessing may have better performance than conventional ones. We have built such a system to enhance the depth of field of an uncooled thermal camera. The phase masks are binary, their structures are optimized thanks to an image quality criterion, and they have been realized with three different technologies that give equivalent results. The deconvolution postprocessing is performed in real time with a graphics processing unit. A significant increase of the depth of field of a factor 3 has been obtained.

Increasing the depth of field (DOF) of compact visible high resolution cameras while maintaining high imaging performance in the DOF range is crucial for such applications as night vision goggles or industrial inspection. In this paper, we present the end-to-end design and experimental validation of an extended depth-of-field visible High Definition camera with a very small f-number, combining a six-ring pyramidal phase mask in the aperture stop of the lens with a digital deconvolution. The phase mask and the deconvolution algorithm are jointly optimized during the design step so as to maximize the quality of the deconvolved image over the DOF range. The deconvolution processing is implemented in real-time on a Field-Programmable Gate Array and we show that it requires very low power consumption. By mean of MTF measurements and imaging experiments we experimentally characterize the performance of both cameras with and without phase mask and thereby demonstrate a significant increase in depth of field of a factor 2.5, as it was expected in the design step.

We report on the design fabrication and characterization a 3-period grating composed of subwavelength ridges of progressively varying widths for operation at 10.6 m. The grating is blazed into the first transmitted order (an efficiency of 80% is measured) under TM polarization and over a broad range of angles of incidence. The fabrication involves contact photolithography, reactive-ion etching, and an evaporation deposition over the etched structure. The result validates the use of photolithography, a low-cost technology, for the manufacture of efficient blazed binary diffractive elements for thermal imaging (the 8-to 12-m IR band).

International audienceThe very large glass forming system, GeSe2-Ga2Se3-CsI, has been recently investigated. The 72GeSe2-18Ga2Se3-10CsI glass composition, which is a stable composition against crystallization and presents good chemical durability, has been selected for different optical measurements. This free-arsenic glass is slightly transparent in the visible up to 12 μm, allowing a great range of applications in thermal imaging. The refractive index has been measured as function of wavelength in the 2-12 μm infrared range at room temperature and the thermo refractive index dn/dT has been determined at 1310 and 1532 nm. Furthermore, the possibility to shape this glass composition by thermal molding without crystallization effect is demonstrated. Also antireflection coating has been optimized for this glass and 97% of average transmission from 8 to 11.5 μm has been achieved

International audienceThe thermal imaging market has experienced a strong growth during the recent years due to continued cost redn. of night vision devices. The development of uncooled focal plane detector arrays is the major reason for the cost redn. Another reason is the continuous improvement of the optical soln. In this paper, we present a new multispectral material which responds to the increasing demand for optics operating simultaneously in the visible​/SWIR (Short Wave IR) and the thermal IR region. The most important properties of some glasses from the GeS2-​Ga2S3-​CsCl system are highlighted in this study. A stable compn. 15Ga2S3-​75GeS2-​10CsCl allowed the synthesis of a large glass without crystn. The refractive index of this glass was precisely measured from 0.6 to 10.4μm by using the Littrow method. The chromatic dispersion was then calcd. and compared with other multispectral materials