Last year when Jess and I were visiting a bison herd in the Badlands National Park, I had a late night encounter with a large bison bull that made me think that having night vision goggles could come in handy for dealing with my own herd. We were camping at the Park's Sage Creek Campground and I had been experimenting with long exposure night photography using black and white film. A massive lightening storm was approaching our region from the west and I decided I would try to drive our car a few miles away from the camp ground and set up my camera along one of the less travelled roads. About a mile down the road I reached an intersection and turned left onto the crossing road. As I turned onto the road, my headlights settled on a big bison bull standing not 30 feet away. He was completely surprised and disoriented by the headlights and bolted forward. This massive furry mountain was suddenly hurtling across the landscape in a complete state of panic. Fortunately, I was not in the direction he was facing when I surprised him with the headlight, so he only went sailing by me instead of into me. This experience did, however, make me think about options for moving about the ranch at night.
Flash forward several months and I am now the owner of an Armasight Spark CORE Gen I night vision monocular. While I do not yet have any bison to monitor with the monocular, it has already proven useful and saved me a few hundred dollars. Last weekend at the ranch I lost my glasses somewhere along a couple hundred yards of trail. The glasses are thin framed and tan-colored and nearly impossible to distinguish from natural vegetation. I spent hours retracing my steps and going over the trail time after time. Right around sun-down I gave up and left with Jess in the truck for our planned evening out at the local pizza shop. I brooded about it for the length of the drive and while we were waiting for our food, but, as the order arrived, it suddenly dawned on me that it might be possible to use my night vision monocular to spot the glasses. My hypothesis was that the lenses and frames of my lost glasses would appear in more contrast against their surrounding when viewed using a night vision monocular with its NIR illuminator. The moment we arrived back at the ranch that evening I put I tested this theory out and, sure enough, within 10 minutes I found my glasses.
For those of you who are unfamiliar with night vision, I'll give a brief overview of what night vision is and why I thought it would be useful. Over the years the technical definition of "night vision" has been muddied and confused for a variety of reasons that I'd rather not delve into, so, rather than write some long authoritative and well documented text outlining what the term means, I'm just going to briefly break-down the term as I see it. In other words, what follows is my opinion, so take it or leave it (if you do have more technical definitions, though, feel free to post it as a comment).
Basically, night vision is a technology designed to make it possible for humans to more clearly view their surroundings in low-light environments. One way of making this possible is to amplify the image produced by light from existing light sources, such as the moon and stars. Various electronic methods of this image amplification have been developed using what are known as "image intensifier" tubes. This what is most commonly defined as "night vision" and is the classic green-hued imagery you see in the movies. Over the years these intensifiers have become more technologically sophisticated to give users (primarily military) a greater advantage. The improvements are grouped into successive technological "generations" (e.g. gen 1, gen 2, etc.).
In addition to the image intensification method of night vision, there are two other methods worth mentioning. One way people can view their surroundings at night is through the use of thermal imaging. This method is fundamentally different in that it is sensing invisible light or electromagnetic energy being radiated from objects in the form of heat or far-infrared and converting that sensed heat information into an image composed of visible light. This method of imaging has, until only very recently, been very expensive and primarily only used by governments and companies. The other method of "night vision" is achieved by combining the CCD sensors commonly used in most digital cameras with reflected near-infrared or NIR. NIR is the wavelength of light just outside of what we can see. Most people (I've heard of occasional exceptions) cannot see NIR, but the CCD sensors in digital cameras can. During normal daylight conditions the NIR being sensed by a CCD would be out-weighed by all of the visible light, but, if you use a filter to eliminate the visible light or use an infrared illuminator when no other light is available, you will be able to record an image.
This now leads me to one final piece of complication regarding the concept of night vision and an explanation for why though I would be able to find my glasses. First, when describing image intensification night vision, I forgot to mention that, in addition to intensifying visible light, these tubes (similar to CCDs) are also able to pick up NIR. As you can see in the above images of NIR captured by CCD sensors, reflected NIR does not always behave in ways you would expect. Objects that might normally seem very dark toned in visible light, might appear very bright in NIR light and vice versa. For instance, dark green vegetation and certain types of dark fabrics will often appear very bright, while water, the sky, and some types of shiny metal will be almost black. Indeed this was the case with the glasses I had dropped in the field. The normally bronze or brass colored thin frames stood out in bold relief against the uniformly bright background of dried dead grass.
Flash forward several months and I am now the owner of an Armasight Spark CORE Gen I night vision monocular. While I do not yet have any bison to monitor with the monocular, it has already proven useful and saved me a few hundred dollars. Last weekend at the ranch I lost my glasses somewhere along a couple hundred yards of trail. The glasses are thin framed and tan-colored and nearly impossible to distinguish from natural vegetation. I spent hours retracing my steps and going over the trail time after time. Right around sun-down I gave up and left with Jess in the truck for our planned evening out at the local pizza shop. I brooded about it for the length of the drive and while we were waiting for our food, but, as the order arrived, it suddenly dawned on me that it might be possible to use my night vision monocular to spot the glasses. My hypothesis was that the lenses and frames of my lost glasses would appear in more contrast against their surrounding when viewed using a night vision monocular with its NIR illuminator. The moment we arrived back at the ranch that evening I put I tested this theory out and, sure enough, within 10 minutes I found my glasses.
For those of you who are unfamiliar with night vision, I'll give a brief overview of what night vision is and why I thought it would be useful. Over the years the technical definition of "night vision" has been muddied and confused for a variety of reasons that I'd rather not delve into, so, rather than write some long authoritative and well documented text outlining what the term means, I'm just going to briefly break-down the term as I see it. In other words, what follows is my opinion, so take it or leave it (if you do have more technical definitions, though, feel free to post it as a comment).
Basically, night vision is a technology designed to make it possible for humans to more clearly view their surroundings in low-light environments. One way of making this possible is to amplify the image produced by light from existing light sources, such as the moon and stars. Various electronic methods of this image amplification have been developed using what are known as "image intensifier" tubes. This what is most commonly defined as "night vision" and is the classic green-hued imagery you see in the movies. Over the years these intensifiers have become more technologically sophisticated to give users (primarily military) a greater advantage. The improvements are grouped into successive technological "generations" (e.g. gen 1, gen 2, etc.).
In addition to the image intensification method of night vision, there are two other methods worth mentioning. One way people can view their surroundings at night is through the use of thermal imaging. This method is fundamentally different in that it is sensing invisible light or electromagnetic energy being radiated from objects in the form of heat or far-infrared and converting that sensed heat information into an image composed of visible light. This method of imaging has, until only very recently, been very expensive and primarily only used by governments and companies. The other method of "night vision" is achieved by combining the CCD sensors commonly used in most digital cameras with reflected near-infrared or NIR. NIR is the wavelength of light just outside of what we can see. Most people (I've heard of occasional exceptions) cannot see NIR, but the CCD sensors in digital cameras can. During normal daylight conditions the NIR being sensed by a CCD would be out-weighed by all of the visible light, but, if you use a filter to eliminate the visible light or use an infrared illuminator when no other light is available, you will be able to record an image.
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| A near-infrared image of a split-rail fence captured on a summer day in Wisconsin using a digital camera in normal daylight with an infrared filter (i.e. filters out everything but infrared). |
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| A near-infrared image captured on a digital camera at night (ignore the date-time stamp) using a normal CCD sensor and an infrared flash. |
This now leads me to one final piece of complication regarding the concept of night vision and an explanation for why though I would be able to find my glasses. First, when describing image intensification night vision, I forgot to mention that, in addition to intensifying visible light, these tubes (similar to CCDs) are also able to pick up NIR. As you can see in the above images of NIR captured by CCD sensors, reflected NIR does not always behave in ways you would expect. Objects that might normally seem very dark toned in visible light, might appear very bright in NIR light and vice versa. For instance, dark green vegetation and certain types of dark fabrics will often appear very bright, while water, the sky, and some types of shiny metal will be almost black. Indeed this was the case with the glasses I had dropped in the field. The normally bronze or brass colored thin frames stood out in bold relief against the uniformly bright background of dried dead grass.