How In-dash Night-vision Systems Work

The human eye can see images which reflect light from violet to red in the electromagnetic color spectrum. Beyond the visible spectrum for humans is the light known as short-wave infrared, light. The human eye is unable to see that light. Short-wave infrared light is a term that actually encompasses all infrared light, but can be broken down into subcategories.

Infrared light actually falls into three classifications: near-infrared (near-IR or NIR), mid-infrared (mid-IR or MIR) and far-infrared (far-IR or FIR), also known as thermal-infrared. The difference between the three types of infrared light comes down to wavelengths. Near-IR, or NIR, has the shortest wavelength -- smaller than 1.5 microns -- and is closest to what we as humans can see as visible light. Far-IR, or FIR, is quite different. Thermal infrared wavelengths can be up to 30 microns and FIR is emitted from an object rather than reflected. In other words, FIR gives off thermal signatures while the other two types of infrared radiation do not.

The two main methods of night vision are thermal imaging and photon detection or image enhancing. Both are used regularly and both have their own advantages and drawbacks. Thermal imaging isn't quite as clear, but it is especially effective for picking up heat signatures. For instance, a soldier looking through a set of thermal imaging night-vision goggles would be able to spot an enemy that is hiding behind a bush or another object that gives off a colder signal. Unfortunately, the bright image could also be a friendly troop. Thermal imaging simply isn't clear enough to show that kind of detail.

Image enhancement on the other hand is very clear. Perhaps you've seen an example of imaging enhancement night vision on a news broadcast or military show. Oftentimes the picture is green, but other than that, the visual is clear as day. Image enhancing takes protons from ambient light and converts them into electrons. These electrons are then chemically and electrically converted into images that appear to be similar to watching an old black-and-white movie.

Next, let's take a look at how the automakers make use of night vision systems.

In 2000, General Motors offered a thermal night-vision system in its Cadillac line of vehicles. The system was innovative, but it was also expensive and didn't produce very clear images. Toyota also gave night vision a shot, and even now the automaker continues to offer an in-dash system in some Lexus models. The Lexus system has its fans, but if it's so effective, then why hasn't this technology spread to every vehicle on the road? One theory is that it seems as if the technology just isn't fully ready for automotive applications. Not yet, anyway. As you can imagine, night-vision technology is expensive and if you use inexpensive components, the quality simply won't be there.

Two of Germany's automotive stalwarts, BMW and Mercedes-Benz, have taken a damn-the-torpedoes approach to in-dash night-vision systems. These two auto manufacturers have been offering night-vision systems in vehicles since 2006. Fittingly, the two automakers, which have been competing against each other in the luxury market for the better part of 50 years, offer systems on complete opposite ends of the proverbial spectrum. Each system accomplishes its goal and each has its benefits and costs.

In the next section, we'll learn how these two companies are making use of the latest in night-vision technology.

As you might imagine, the two auto moguls get from point A to point B in entirely separate ways. Mercedes-Benz uses an active system or near-IR system that illuminates the night with projected infrared light, much like optics found in military-issue night-vision goggles. BMW's passive system, on the other hand, uses far-IR or FIR technology in its onboard night-vision systems.

Unlike night-vision optics used for military applications, BMW's system registers images based on body heat and produces images that resemble a photo negative. While that works well for deciphering between animals and people, it doesn't do much for revealing a dead animal in the middle of the road or perhaps a large rock or a fallen tree. BMW's infrared system uses complementary metal oxide semiconductor (CMOS)-based sensors on the front of the car that pick up heat from objects and processes the thermal signature to display images on a quarter video graphics array (QVGA) display (320x240-pixel resolution) mounted on the dash in the center of the vehicle's console. In a nutshell, the BMW's system picks up the heat of the animal or pedestrian and displays it as a bright image. The warmer the target, the brighter the image displays. It has a range of around 980 feet (299 meters) and can pan in the direction the vehicle is heading. The FIR night vision system illuminates what's directly in front of the vehicle reasonably well, but doesn't offer the clarity found in the Mercedes system.

In contrast, the Mercedes system uses NIR technology and produces an even, clear picture in the dark. This system is similar to night-vision goggles soldiers use. Like the military-issued night-vision goggles, the NIR system in the Mercedes illuminates everything as if it were in the high beams of the vehicle. By utilizing a series of projection bulbs and cameras, the Mercedes' active night-vision system picks up the faintest traces of light and transforms it into a clear picture. The advantage is that the Mercedes system can see warmer living things just as clear as it can spot colder, dead animals or non-living objects. The drawback to the Mercedes system is its range: The system has a maximum effective range of less than 600 feet (183 meters). Another drawback is the Mercedes' NIR system doesn't handle fog well, while the BMW's FIR system can see through the dense conditions. But unlike the BMW's system, the Mercedes monitor is located behind the steering wheel, directly in the driver's line of sight to the road, and the image quality is also crisper on the NIR system.

Both systems can be turned on or off by the driver with controls found near the high-beam lever and neither system is affected by oncoming bright lights. Both are easy on the eyes too, so sensitivity to light should not be a problem for most drivers. Researchers from the two companies are also in the process of perfecting warning indicators on the night-vision systems. The challenge is to be able to decipher what's a hazard and what's merely a heat signature. The goal is for the systems to be able to set off an alarm when a pedestrian or animal is close enough to the road to be hazardous.

Both systems cost an extra $2,000 to $2,500. While that may sound like a significant amount of money, when you look at the price tag of a 7-Series BMW or S-Class Mercedes, two vehicles that can easily top $100,000, it somehow seems a bit more reasonable -- especially when you consider the benefit of being able to see through the darkness.

You can read more about light, night vision and other related topics on the next page.