Abstract
We present our work regarding the evaluation of protection measures against laser dazzling for imaging devices. Different approaches for the evaluation of dazzled sensor images are investigated to estimate the loss of information due to the dazzle spot: (1) counting the number of overexposed pixels, (2) based on triangle orientation discrimination, and (3) using the structural similarity index. The evaluation approaches are applied on experimental data obtained with two different sensors hardened against laser dazzling. The hardening concept of the first sensor is based on the combination of a spatial light modulator and wavelength multiplexing. This protection concept allows spatially and spectrally resolved suppression of laser radiation within the sensor’s field-of-view. The hardening concept of the second sensor utilizes the principle of “complementary bands.” The optical setup resembles a common three-chip camera, with the difference that dedicated filters with steep edges replace the regular spectral band filters. Although this concept does not really represent a “protection measure,” it allows the sensor to provide information even in laser dazzling situations. The data for the performance evaluation were acquired both in a laboratory setup using test charts comprising triangles of different size and orientation as well as in field trials.
Highlights
In recent years, there has been a particular interest in research on dazzling by continuous-wave laser radiation
Besides work on computer visualization of laser eye dazzle and the study of the influence of atmospheric scattering on human eye dazzle,[2] they introduced the very interesting concept of the “nominal ocular dazzle distance.”[3]. This approach allows the calculation of the minimum distance for the detection of targets in case of laser dazzle
⚬ Number of micromirrors Nmm that were toggled in the case of activated digital micromirror device (DMD): For the data gathered with activated DMD, we present only those results that deliver the highest recognition probability or highest value of the structural similarity (SSIM) index when varying the number of activated micromirrors Nmm
Summary
There has been a particular interest in research on dazzling by continuous-wave laser radiation. Williamson[1] put a lot of effort into the investigation of the influence of laser dazzle on the human eye. Coelho et al.[4] developed a computer model of the eye to assess laser dazzle. Besides investigations regarding laser dazzle of the human eye, laser dazzle of electro-optical sensors is quite interesting since they are highly susceptible to laser illumination. The realization of protection measures encountering laser irradiation of arbitrary wavelength is not an easy task. Conventional laser protection measures like absorbing or interference filters usually work only for specific wavelengths or a limited spectral range. For wavelengthindependent laser protection measures, other techniques have to be utilized. An overview on different possibilities for laser protection is given in a publication of Svensson et al.[5]
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