The purpose of night vision systems is to provide drivers during night and adverse weather with visual information beyond the range of their headlamps and beyond the glare of an oncoming vehicle's headlamp. Thus the driver has more time to react in case of unexpected and dangerous situations.
Basically, two different concepts can be followed up. Passive night vision systems visualize the thermal radiation emitted by the objects themselves [1] while active night vision systems image near-infrared radiation which is reflected by the objects in the scene.
Unlike passive systems, active night vision systems need powerful near-infrared light sources and cameras which are considered especially with respect to automotive requirements. Halogen light sources are the most promising candidates because about 25 percent of the total radiated power of a 60 W lamp lies in the near-infrared wavelength range from 800nm to 1100nm. Furthermore the optimization capabilities of halogen and gas discharge light sources are discussed.
Based on the specifications of optimized light sources and cameras and on the reflectance data of typical objects in the traffic scene the visibility range of an active night vision system is estimated.
