Digital Night Vision
Digital night vision is a newer consumer technology that gives results similar to Starlight technology with some additions and advantages. The positive side is that this technology can give results that are comparable to earlier Generation 1 devices at less cost and without the distortions inherent in Generation 1 “Starlight technology” night vision. The negative side is that this is about the extent of its capabilities. It does not compare to Generation 2 or later Starlight technology devices. Digital night vision also has a significantly reduced range. Even some of today’s Generation 1 night vision devices will often outperform these devices when viewing beyond reasonably close distances.
The technology for this type of night vision is quite different from standard night vision and generally works like this. The light comes into the device through an objective lens and is then processed through a highly sensitive charged coupling device (CCD) and then sent to a Liquid Crystal Display (LCD) where you can view the image. This can vary a bit and there might be an eyepiece to look into to view the output rather than a LCD screen. If you are trying to remain undetected by whom or what you are viewing, the eyepiece devices are preferable, as they will not illuminate your face as an LCD will. As with standard night vision devices, you are not looking directly at an amplified image but rather a processed and recreated image. Some digital video cameras have a “0 Lux” mode that works essentially the same way.
One great advantage of Digital Night Vision is that you can also look through these devices in the daylight without the concerns of damaging it. They are similar to Generation 1 night vision devices in that they only amplify available light and require an IR illuminator to see in dark areas. Most digital night vision devices are equipped with IR diodes (a bank of small IR lights). They also often come with multiple filters so that the image can be viewed in shades of green, red or gray. The green filters give you the greatest image contrast and detail and appear similar to standard night vision devices. Red filters are used to preserve your own night vision (like using a red light to view star charts so your eyes don’t take such a long time to readjust to the darkness). The gray or neutral filter minimizes the amount of light to your eyes and appears somewhat like a black and white display.
Thermal-Imaging
“Thermal-Imaging Night Vision” is much different than what we have looked at with light amplification devices. We will only briefly define these types of devices since many people confuse standard night vision devices with thermal-imaging abilities. At this point, the technology starts at about $10,000 which is generally cost-prohibitive for most consumers.
Thermal-imaging devices look at heat, not visible light. Unlike image-intensifiers, they are unaffected by smoke or fog and they can be used in absolute darkness since they are not dependant on visible light. They have infrared-detectors that are sensitive to the invisible infrared portion of the electromagnetic wave (heat). All objects emit heat or infrared radiation. Thermal-imaging devices have infrared-detector elements that see this portion of the spectrum only. The image is usually seen as a gray-scale view contrasting with image-enhancement technology that is viewed in green scale (that eerie green view). Some of the more expensive models even display the resulting views in color on small screens. Color representations or images are called thermograms. By convention the cooler colors are represented by blacks, blues and greens. Whites, reds, and yellows represent the warmer colors.
Detail in thermal-image viewing is also very different since you are looking at heat differences and not at light reflecting off surfaces that give you the shadows and details we are accustomed to seeing with visible light. Other details that are not seen in visible light are apparent when looking through a thermal-imaging device. Since we are looking at heat, after leaning against a wall with your hand, looking through a thermal-imaging device you would see a hand print on the wall. Even the wall itself might show the internal studs as a slightly different color since the part of the wall where the studs are attached is slightly denser and subsequently heats and cools at a different rate. Freshly painted areas would be a slightly different color or freshly dug holes in the ground show up visually, whereas in daylight these details are invisible to your eyes. These types of details make thermal-imaging devices very applicable to law enforcement type of uses.
This article comes from optics4birding edit released