Design and implementation of a scene-dependent dynamically selfadaptable wavefront coding imaging system

A computational imaging system based on wavefront coding is presented. Wavefront coding provides an extension of the depth-of-field at the expense of a slight reduction of image quality. This trade-off results from the amount of coding used. By using spatial light modulators, a flexible coding is achieved which permits it to be increased or decreased as needed. In this paper a computational method is proposed for evaluating the output of a wavefront coding imaging system equipped with a spatial light modulator, with the aim of thus making it possible to implement the most suitable coding strength for a given scene. This is achieved in an unsupervised manner, thus the whole system acts as a dynamically selfadaptable imaging system. The program presented here controls the spatial light modulator and the camera, and also processes the images in a synchronised way in order to implement the dynamic system in real time. A prototype of the system was implemented in the laboratory and illustrative examples of the performance are reported in this paper

A CW high specific output power Ar-He-Xe laser with transverse RF excitation

A transverse RF excited gas discharge has been successfully used to produce a CW Ar-He-Xe laser. A maximum output power of 330 mW has been obtained from an experimental device with 37 cm active length and a 2.25 (DOT) 2.25 cm2 cross-section. This corresponds to a specific output power of about 175 mW/cm3. Under these preliminary optimum conditions the gas pressure was 85 Torr (Ar:He:Xeequals59:40:1). The laser output spectrum consisted of 5 atomic xenon lines (2.03, 2.63, 2.65, 3.37 and 3.51 micrometers ). The 2.03 micrometers and 2.65 micrometers lines were the strongest ones. Complementary to this device a quartz capillary was tested as laser tube for the atomic Xe laser. With this configuration it was possible to sustain a longitudinal DC as well as a transversal RF discharge in the laser gas mixture. Combined excitation was also possible for this device. This enabled us to compare the laser performance in both the DC and the RF mode in the same device. Preliminary measurements showed us that the highest output power in the DC mode was less than 1 mW, while the RF excited laser yielded about 130 mW. The gain coefficient was found to be extremely high. Laser generation was obtained for a wide range of reflectivities R of the outcoupling mirror. At the minimum reflectivity of 5% an output power of 20 mW was obtained. Results obtained from both systems are discussed