InfraRed and Thermal Cameras, the Solution for Low Light Challenges

Our previous entry, Light - What It Is, and Isn’t, explored the electro-magnetic spectrum and noted what a small portion visible light occupied. While visible light may be small in the big scheme of things, it is the only

type our eyes can utilize for vision.

Cameras also need visible light to capture an image, and they process it in pretty much the same way. There are some species of animals, though, that can function in a minimum of light. The same can be said of certain types of IP cameras, which is a good thing since there are times when it is necessary to capture an event in less than optimal lighting,or even harder, no light at all. As available light decreases, there is a range of surveillance cameras we can turn to.

Low Light IP Cameras  

Owls and cats are both thought of as being nocturnal; a word Merriam Webster defines as active at night. And just what allows these two creatures of the night to carry on life as usual long after the sun has set?  They both have proportionately large eyes; eyes that contain more light receptors than do the eyes of the rest of us, creatures who require a well-lighted situation. Nonetheless, even nocturnal animals need a low level of light. They cannot function in total darkness. The same holds true for low light cameras. They need some light 

A low light camera depends on large image processors to collect as much of the scant light as possible and the CMOS and CCD chips available today are especially good at picking up light. Some low-light color cameras amplify whatever light is available by switching to monochrome mode in order to increase light sensitivity.   

Another way to increase light sensitivity is to choose a lens with a low f number of 1.4 or less. The lower the f number the more light the lens will admit.

IR cameras

When the available light is below the threshold at which low-light cameras operate, we turn to what are also known as day/night cameras. Day/night cameras have infrared or IR sensitivity, meaning they are able to function under infrared illumination.

 The infra in infrared light means below and refers to the fact that infrared light radiates at wavelengths of 700 – 1400 m, a lower frequency than the red portion of light visible to our eyes. Like the rest of the electro-magnetic spectrum, infrared light is always present.

Because infra-red light affects the color capability of  image sensors, day/night cameras are equipped with removable filters to control IR sensitivity. The filters are kept in place during the day but removed at night and the camera switches to mono-chrome mode in which it can utilize infrared light.

Since an I-R camera needs more infra-red light than what occurs naturally, we need to supplement it  Some day/night cameras, like the Vivotek FD-6112V, come with special bulbs or built-in LED IR illumination,

allowing it to function without any other illumination for a distance just over 30 feet. Other I-R cameras require add-on IR illumination. More powerful illuminators are needed for greater distances, and the narrower the beam the better. Some of the more powerful provide a 6 degree beam, lighting as much as 1300 feet. When using IR illumination, we also need to use a lens rated for IR use.

Since infrared light is not visible to the human eye, IR cameras are popular in covert operations when it is necessary that people not know they are being filmed. In extremely covert operations carried out totally dark or conditions impenetrable by light, we can turn to a particular type of IR cameras, those with thermal imaging capability.

Thermal Imaging Cameras

Thermal imaging cameras, technically known as thermo graphic imaging cameras are able to function when there is absolutely no visible light. Thermal refers to the fact that the sensor incorporated into this type of IR camera is sensitive to temperatures higher than the surrounding environment. Thus it can sense the heat radiating from a person

or animal, and can detect this heat energy through conditions such as smoke, fog or blowing sand that would render a  conventional light-dependent camera useless.

Thermal imagine IR cameras are able to function in these conditions because, if you recall from Light - What It Is, and Isn’t, infra-red light radiates at a lower frequency but its wavelengths are longer. The added length allows it to pass through light obstructing particles, off of which,due to its shorter wavelengths, visible light would bounce. The infra-red light penetrates these obscurants, making it possible for the camera’s thermal imager to detect the found object's radiated heat energy.

Thermal imaging cameras are sometimes referred to as FLIR, for Forward Loading Looking Infra –Red

cameras. The name stems from military operations in which planes are outfitted with this type of camera facing forward.

Thermal imaging applications are also used in police forensic work. In fact it was a thermal imaging device that put an end to the search for the surviving Boston Marathon bomber this month. When the owner of a house discovered fresh blood on a tarp covering the winter-stored boat in his backyard, he alerted police. Using a thermal imager, a specially trained officer detected the outline of a cowering figure, and Boston was able to breathe again.

Since thermal imaging promises to play a vital role in our security, our next entry will look at it in more detail, and explore areas and applications that can benefit from its use.

If you would like more information on any of the cameras discussed here, visit www.kintronics.com or fill out out a request for information form and one of  our sales engineers will respond. Or if you'd prefer, call 914-944-3425