Being able to see in the dark is one thing that many animals are far more accomplished at than we are. This is to do with the way their eyes work, as opposed to ours. Animals that can see better in the dark have a slightly different composition of the eye, and usually a larger pupil aperture, to enable them to process vision in the dark.
This is why nocturnal animals are able to go about their nightly life oblivious to the fact it is dark. Vision is all about the way our eyes process and reflect the light that is around us, so once it becomes dark, human vision is seriously impaired.
For people who might need to work in the dark – the military, security forces, hunters and so on – the advent of night vision and thermal imaging technology has been a major bonus. There is a difference between these two methods of enhancing the ability to see in the dark, so let’s have a look at the differences between them.
How Night Vision Works
As we have said, our vision depends entirely upon light reflecting off objects and our eyes delivering that image for the brain to process. In daylight, therefore, we are at our best. At night, driving for example, we rely on street lights and the lights on other vehicles to provide this effect. When there are none present, we are hampered considerably in our vision.
Night vision lenses work by amplification; instead of sound, as in a microphone and amp, the device amplifies the light entering the lens. The first stage is to enhance the light using what is known as a photocathode. This converts the light into electrons, the form in which it can be amplified.
The electrons are amplified using a stage known as the photomultiplier, and are presented to a phosphor screen, on which they are seen as tiny flashes. Together, these flashes are seen by the viewer as a more powerful version of what the eye could see – enhanced night vision.
How Thermal Imaging Works
Thermal imaging differs from night vision in the fact it uses a heat source as the primary target. All living things give off heat in the infra-red spectrum. A specially equipped thermal imaging camera, scope or other device can use this to present an image that is recognisable.
The thermal imaging device uses an array of tiny detectors to scan the infra-red images that it is focusing on. This creates, very quickly, a thermal image of the object or objects in view. This is called a thermogram. The thermogram image is then converted into electrical impulses.
These impulses are analysed by a processing unit in the device, which converts them into the image we are familiar with from watching thermal imaging units at work. It’s a sophisticated system, but one that can be found in some very compact cameras, scopes and other items.
Which to Use
There are many civilian uses for thermal imaging devices – security around the home or commercial premises, for example – so if you think such a device would be of use to you, have a look now at the many available models on the market.Powerpoint Engineering offers some great thermal imaging devices for example.
In many ways, thermal imaging is a more potent method of ‘seeing’ in the dark than a night vision device. As it uses heat for a source, it is also more capable of finding people and animals in the dark. Military units across the world use thermal imaging scopes and headsets very successfully, and military hardware – planes, helicopters and ships – also makes use of such devices.