| Night Vision helps humans see in what we call the | | | | strong one. The few photons that exist in the dim light |
| dark. Humans see in only a small part of the light | | | | are converted to electrons. The electrons, pushed by |
| spectrum. Light is made of waves of energy and the | | | | a strong voltage within the tube, collide with the sides |
| longer the wave is, the less energy it has. The shorter | | | | of the slightly bent tube to create thousands of |
| a wave is, the more energy it contains which means | | | | electrons. Electrons hitting other electrons in the micro |
| that the visible light we see has a range of energy | | | | channels of the vacuum tube generate thousands |
| levels. Red is the lowest. Violet has the highest energy. | | | | more electrons than there were to start with. There is |
| The colour spectrum increases in energy as you go | | | | a screen covered with phosphers at the end of the |
| from red, orange, yellow, green, blue, indigo, and the | | | | tube. When the electrons hit the phosphers they |
| highest violet. Below the visible red waves, we can | | | | become excited. A greenish light is given off in the |
| see are even lower energy waves called infrared. We | | | | image of what there is to be seen. |
| can also call these heat waves. The infrared part of | | | | Another way night vision is achieved is by using the |
| the light spectrum can be divided into three types. Near | | | | heat objects give off. This is how thermal imaging |
| infrared is closest to visible red light. Mid infrared | | | | works. The light given off by warm objects is focused |
| waves are longer and farther away from visible red | | | | by a specially designed lens. This infrared light hits an |
| light. Thermal infrared has longer wavelengths still. | | | | electronic detector device, which creates a detailed |
| Violet is the highest visible wavelength, which humans | | | | pattern of the differences in temperature. This pattern |
| can see. Above the violet coloured waves, we see in | | | | is called a thermogram. The information held in the |
| the visible light spectrum, are the ultra violet waves, | | | | thermogram is transformed into electrical impulses. A |
| which has higher energy waves than visible violet light. | | | | little computer creates usable data from the electrical |
| Night vision devices can help you see a great distance | | | | impulses and the data is processed more and sent to |
| away on a cloudy night when there is no moon light | | | | a display where it is seen as various colours, |
| and it works in two ways. | | | | depending on how much infrared light an object was |
| One way uses light that that we cannot see toward | | | | giving off. There must be a temperature difference |
| the infrared end of the light spectrum. This light is | | | | between objects and their surroundings to detect |
| amplified to the point where we can see images. | | | | images. This image can be viewed through a scope |
| A lens focuses visible and infrared light into a special | | | | like in a pair of binoculars or on a monitor screen. |
| electronic tube that intensifies a dim image into a | | | | |