Automatic laser glare suppression in electro-optical sensors.

Gunnar Ritt,Bernd Eberle

doi:10.3390/s150100792

Abstract

Progress in laser technology has led to very compact but nevertheless powerful laser sources. In the visible and near infrared spectral region, lasers of any wavelength can be purchased. Continuous wave laser sources pose an especially serious threat to the human eye and electro-optical sensors due to their high proliferation and easy availability. The manifold of available wavelengths cannot be covered by conventional safety measures like absorption or interference filters. We present a protection concept for electro-optical sensors to suppress dazzling in the visible spectral region. The key element of the concept is the use of a digital micromirror device (DMD) in combination with wavelength multiplexing. This approach allows selective spectral filtering in defined regions of interest in the scene. The system offers the possibility of automatic attenuation of dazzling laser radiation.

Highlights

Electro-optical sensors are widely used in many different applications, but they are susceptible to overexposure and to optical damage
Laser dazzling can pose a severe problem to electro-optical sensors used in autonomous or surveillance systems [3], so adequate protection against dazzling is highly desirable
With the implementation of wavelength multiplexing, we were able to significantly improve upon the concept of Tomilin and Danilov

Summary

Introduction

Electro-optical sensors are widely used in many different applications, but they are susceptible to overexposure and to optical damage. Current laser protection measures are typically realized using conventional optical filters based on absorption or interference effects These filters work only for predefined wavelengths, but not beyond. Among them are active systems like shutters, frequency agile filters or spatial light modulators Such active systems are useless against short-duration laser pulses since they suffer from the disadvantage of a finite response time. In order to realize such an operating principle, it is necessary to place the spatial light modulator in the intermediate focal plane of an optical system. This method is primarily useful to protect electro-optical sensors against laser radiation.

Operating Principle

Optical Setup

Control Loop Implementation

Field Trials

Laboratory Tests

Theoretical Estimation of the Maximum Attainable Attenuation