It is one of the most interesting and recent technologies to join the group of systems known as ADAS, designed to assist drivers to mitigate the risk of an accident and sometimes even avoid it altogether. Night vision devices have been carried over to the automotive world directly from the electronics sector, after having been installed on cameras and special optical equipment to see in dark and dimly lit environments or simply at night.
Experimentation follows military use. The first examples of night vision systems date back to World War II when infrared converters were used. These vacuum tubes made infrared light visible but could not amplify it. It was during the Vietnam war that the real development of night vision devices occurred with the first visors for helicopter pilots and telescopic viewfinders for automatic weapons.
The debut in 2000
Night vision systems on cars use a thermographic camera to increase the driver's perception to see in the dark or in bad weather conditions far beyond the range of the headlights.
The technology was first introduced on the Cadillac Deville in 2000, combining instruments such as infrared cameras, GPS, radar and Lidar. The latter is the acronym of Laser Imaging Detection and Ranging, a remote sensing technique used to determine the distance of an object or surface using a laser pulse.
There are two types of night vision systems: passive and active. The former systems are based on technologies that detect the thermal radiation emitted by humans, animals and other objects on the road, while the latter illuminate objects at a significant distance using infrared light sources.
More about active systems...
Active Night Vision systems exploit the ability of surfaces to reflect in the near-infrared spectrum (i.e. NIR with wavelengths close to those of visible red light). In other words, the thermal cameras fitted on cars image the radiation reflected by the objects in the scene by the active lighting of the headlights and not the emissions of the objects themselves. Of course, the environment will continue to appear dark to anyone not using an infrared visor.
More in detail, the advantages of active systems are high image resolution, the ability to detect inanimate objects clearly and better operation in normal weather conditions. On the contrary, they do not perform as well in fog and rain, offer less contrast for the animals and have a shorter range (150-200 metres) compared to passive systems.
The automakers that followed this trend are Toyota since 2002 (the major experimentation in the field having been entrusted to Lexus) and Mercedes-Benz, that addressed the matter in 2003 with the F500 concept before making the Night View Assist standard two years later on the S-Class.
...and about the passive ones
Passive systems integrate a thermal imaging camera that works by detecting the infrared radiation that all objects emit at a temperature different from ambient temperature. This implies that there is no need for illumination by an external source. The objects are the source of the radiation needed by the system themselves.
The image appears rather different from what we are normally accustomed to. Thermal cameras detect intensities proportional to the surface temperatures of the objects and the brighter ones are the warmer ones and not those that reflect visible light better. The pros of passive systems are a range of up to 300 metres and higher contrast for animals and people, while the cons include grainer images, poorer operation in warmer weather conditions and the need to mount a larger sensor.
Following the concept of these systems, that have evolved from one generation to the next, are Audi (on the A8 since 2010), BMW (on the 7 Series since 2005), Honda (on the Legend in 2004), the previously mentioned pioneer Cadillac and DS, that since becoming an autonomous brand in the PSA group is pushing hard on the matter with the flagship DS7 Crossback.