See-in-the-Darlc Project

This useful and interesting project shows how to build a device capable of seeing in total darkness. Unlike conventional devices requiring the minute light from the stars or other ambient background light, this system contains its own infrared source, allowing covert viewing of the desired subject (see Figure 23-1).

Assembly is shown in two parts, the high voltage power supply and the final enclosure with optics and an illuminator. Expect to spend $50 to $100 for this useful infrared imaging system with all the special­ized pans available from www. amazingl. com.

General Description

Lhis project shows how to construct a device capable of allowing one to see in total darkness. It can be used to view a subject for recognition or evidence – gathering reasons without any indication lo the target subject that he or she is under surveillance. It is an invaluable device when used for detection, the align­ment of infrared alarms, invisible-laser gun sights, and in communications systems. This technology can also be used to detect diseased vegetation in ccriain types of crops from the air. to serve as an aid to nighttime varmint hunting, and to view high-temperature ther­mographic scencs where heat is used to produce the image. This device is excellent for use with the infrared laser described in Chapter 9. “Handheld Burning Diode Laser Ray Gun,” with a perlormance that is as good operationally as units that cost much more.

The unit is built using readily available parts for the enclosure and basic optics. The batteries are enclosed into the housing and do not require side packs, cables, and so on. The range and field of view­ing are determined by the intensity of the integrated infrared source and the viewing angle of the optics. Readily available and low-cost optics are usable, but they may have spherical aberration and other adverse effects. This approach keeps the basic cost down for those not requiring actual viewing of detailed scenes. Improved optics will eliminate these effects and can be obtained at most video supply houses as an option.

Assembly foeuses around common polyvinyl chlo­ride (PVC) tubing as the main housing and a spe­cially designed, patented, miniature power source for energizing the image tube. The tube is a readily avail­able image converter being used by most manufac­turers of similar devices. This tube establishes the limits of viewing resolution and is suitable for most applications but may be limited if one desires video perfection.

See-in-the-Darlc Project

Figure 23-1 See-in-the-dark viewer

The viewing range is determined mainly by the intensity of the infrared source and can be controlled by varying this parameter. Our basic unit is shown
utilizing a 2-D cell flashlight with an integrated filter placed over the lens to prevent the subject from see­ing the source. This provides a working range of up to 50 feet (reliably) and can be increased to several hun­dred using a more powerful source such as a 5 to 6 cell flashlight. Needless to say. the builder can choose his or her infrared source and adjust the optics to meet his or her needs. Infrared light-emitting diodes (LEDs) or lasers, as described in our catalog, are also good illumination sources. Long-range, quick viewing may utilize a small, two-cell light with eight nickel – cadmium (NiCad) A A cells to replace the normal two D cells, providing a significantly brighter infrared source yet lasting for less time than the normal D cell would.

The unit can also be operated using external sources such as super-intense Q-beam handheld lamps with an added filter extending the range out to 400 to 500 feet, providing a wide field of illumination. Note the viewing of active infrared sources such as lasers does not require the internal infrared source.

An optional long-range, infrared illuminator for viewing up to 300 feet is available. See #HLR10 at www. amazmgl. com and optional equipment can be found on the parts list at the site.

Basic Theory

A subminiature high-voltage power supply produces approximately 15 Kv at several hundred microam­peres from a 7- to 9-volt rechargeable nickle cad­mium (NiCad) or alkaline battery. This voltage is applied to the tube (IR16) with the “plus” going to the viewing end and the “negative" to the objective end. A focus voltage is taken from a tap in the multi­plier circuit and is approximately Чь of the total potential.

An objective lens (LENSI) with an adjustable focal length gathers the reflected image, illuminated by the infrared lens, and focuses this image at the objective end of the tube. Image conversion now takes place inside the tube and is displayed on the viewing screen of the tube in a greenish tinge. The viewing resolution is usually adequate to provide

subject identification at a distance of 50 feet or more depending on the intensity of the infrared source and the quality of the optics.

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