Evaluation of protection measures against laser dazzling for imaging sensors

Abstract

We present the latest results of our work regarding the evaluation of protection measures against laser dazzling for imaging devices. Three different approaches for the evaluation of dazzled sensor images are investigated and compared to estimate the loss of information due to the dazzle spot by a) counting the number of overexposed pixels, b) based on triangle orientation discrimination (TOD) and c) using the structural similarity (SSIM) index. The performance evaluation approaches are applied on experimental data obtained with two different imaging 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 active 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 3-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 was acquired both in a dedicated laboratory setup using test charts comprising triangles of different size and orientation as well as in field trials.