Laser For Emergencies
In search & rescue operations, it is generally assumed that lasers have little application. This is not entirely correct. A normal laser, with a normal, thin, collimated beam does have little use because such a beam is nearly worthless as a signaling device. For example, you and your companions are on the side of a mountain, doing entomological research, when an accident occurs. The radios are lost, and the only tools left for signaling are a flashlight and a pocket laser brought along for research use. Of the two devices, only the flashlight is practical for signaling because its wide beam can be seen over a wide area in the valley below. Trying to signal with the laser is nearly useless because the odds of people in the distance seeing the laser dot or the narrow beam is incredibly small. Indeed, if someone does see the beam, it may be because you just hit them in the eye, which means they are now probably in pain and thus not able, or interested, in offering assistance. However, if the laser’s beam is first converted from its normal shape into a thin line, several arc degrees in length, the laser can become a useful signaling tool, perhaps better than flashlights or many of the small emergency signal flashers available.
Lasers are available which project a long, thin line instead of a dot and special lens systems are available to convert a normal laser beam into a line. In an emergency, if a need for signaling arises, an ingenious person may be able to fabricate their own conversion lens. The simplest way to do this is to secure a piece of clear glass or plastic tubing against the end of the laser, so that one side of the tubing lies directly over the orifice where the laser beam exits. When properly positioned, the laser beam should pass through both sides of the tubing, at the tubing‘s widest point. Things such as medicine droppers and pipettes might work well for this purpose. If tubing isn’t available, a piece of broken bottle might be used to produce the thin laser line needed. How wide and long the line is depends on the diameter and wall thickness of the tubing, and to a lesser degree its composition. It should be noted that the longer the laser line is, the less bright it will be at any point along its length.
A laser that outputs a line is used for signaling is merely waving it back and forth in the direction of those you wish to signal. Because the beam is now a long, thin line, and not a collimated beam, it poses little danger to the eyes of people in the distance - which should improve your odds of being rescued.
If there is no possible way to fabricate a lens to go on the laser, there may be a way to create a visible line by reflecting a laser beam off a body of water. For instance, if the village at the base of the aforementioned mountain should lay alongside a river, you might be able to reflect the beam of your laser off the surface of the water which, if you are fortunate, might result in a huge, vertical line being projected onto the side of a building in the village. The best chance of accomplishing this feat is to aim for the edge of the water nearest the village.
By moving the laser along the river’s edge, thus moving the glowing vertical line throughout the town, you might get someone’s attention and perhaps some aid.