Electro-optical imaging sensors are widely distributed and used for many different tasks in military operations and civil security. However, their operational capability can be easily disturbed by laser radiation. The likeliness of such an incidence has dramatically increased in the past years due to the free availability of high-power laser pointers. These laser systems, offering laser powers of several watts, pose an increased risk to the human eye as well as to electro-optical sensors. An adequate protection of electro-optical sensors against dazzling is highly desirable. Such protection can be accomplished with different technologies; however, none of the existing technologies can provide a sufficient protection. All current protection measures possess individual advantages and disadvantages. We present the results on the performance of two different protection technologies. The evaluation is based on automatic optical pattern recognition of sensor images taken from a scene containing triangles
The continuous development of laser systems toward more compact and efficient devices constitutes an increasing threat to electro-optical imaging sensors, such as complementary metal-oxide-semiconductors (CMOS) and charge-coupled devices. These types of electronic sensors are used in day-to-day life but also in military or civil security applications. In camera systems dedicated to specific tasks, micro-optoelectromechanical systems, such as a digital micromirror device (DMD), are part of the optical setup. In such systems, the DMD can be located at an intermediate focal plane of the optics and it is also susceptible to laser damage. The goal of our work is to enhance the knowledge of damaging effects on such devices exposed to laser light. The experimental setup for the investigation of laser-induced damage is described in detail. As laser sources, both pulsed lasers and continuous-wave (CW)-lasers are used. The laser-induced damage threshold is determined by the single-shot method by increasing the pulse energy from pulse to pulse or in the case of CW-lasers, by increasing the laser power. Furthermore, we investigate the morphology of laser-induced damage patterns and the dependence of the number of destructive device elements on the laser pulse energy or laser power. In addition to the destruction of single pixels, we observe aftereffects, such as persistent dead columns or rows of pixels in the sensor image.
Summary form only given. Many organic and inorganic materials like dyes, carbon based nanomaterials and inorganic nanoparticles were found to show strong interaction with laser light. Nanoparticles offer the advantage that they can be designed specifically with respect to their composition, size, shape, and surface chemistry, what gives unique properties to them. Thus, nanoparticles can be used for numerous technical applications as well as in biology and medicine, and they are good to investigate fundamental questions. We evaluate a variety of different kinds of nanoparticles suspended in various solvents regarding their nonlinear attenuation characteristics with respect to nanosecond laser pulses. Generally, in a first step the samples are characterized with respect to their linear optical properties by spectral absorption measurements, their particles' size and size distribution estimated by dynamic light scattering, and their structure analyzed by scanning electron microscopy. Subsequently, we measure the nonlinear attenuation of the samples along the optical axis using our standard experimental setup [1-3]. Additional nonlinear scattering measurements allow us to discriminate against nonlinear absorption and thus to learn about the involved physical processes leading to the nonlinear extinction. Thus by measuring nonlinear scattering and nonlinear attenuation we are able to estimate the nonlinear absorption of the various samples. In order to further improve the nanoparticle's absorption coefficient we have to identify the most important material properties influencing the extinction of the samples. That task is performed by means of a Principal Component Analysis (PCA). Due to the large amount of data the analyses are limited to nanosecond pulses at the wavelength of 532 nm. In parallel, we started to perform numerical calculations to simulate the attenuation of suspended nanoparticles caused by nonlinear scattering. Nonlinear scattering is an induced process resulting from local heating of the nanoparticle and its surrounding. To learn about the details of the thermal heating processes we use a finite elements method to solve the heat transport problem. The simulation provides insight into the temporal size evolution of induced scattering centers. Furthermore, it allows us to calculate the influence of Mie scattering on the attenuation process. We outline, that this method can be used to predict the dependency on various material properties. A comparison of simulated results with experimental ones can lead to a further understanding of the interaction between the different mechanisms involved [4]
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