Rangefinder

From ArticleWorld

A rangefinder is the name given to the device that measures distance from the observer to a particular object.

The methods used for measuring distance vary from active methods (such as laser, sonar or radar) to indirect methods that involve the use of trigonometry.

Rangefinder camera

The most common application of rangefinders today is in rangefinder cameras. This type of rangefinder usually works by showing two superimposed images of the object, one of which can be adjusted by the user so that they align perfectly. The amount of adjustment required allows the camera to determine the distance to the object. If the adjustment of the rangefinder also adjusts the focus it is known as a coupled rangefinder. Older designs used uncoupled rangefinders – these required the reading from the rangefinder to be manually transferred to the lens focusing ring.

Laser rangefinder

This type of rangefinder uses a laser beam in order to determine the distance to a reflective object. The laser range finder consists of the following parts:

• A laser generator
• A target
• A highly precise timing mechanism
• A computer for converting time information into a calculated distance
• A readout

The rangefinder sends a laser beam towards the object and simultaneously starts the timing mechanism. The timing mechanism is typically graduated in microseconds or even lesser. The laser beam is reflected back by the object in the same path as it has traveled and hits the rangefinder, stopping the timing mechanism. Since the speed of light is constant, the distance to the object can easily be calculated by the computer, given the elapsed time. This resulting calculation is then displayed on the readout in feet or meters.

The disadvantage of a laser range finder is that its behavior depends upon the reflectivity of objects. Also, due to the high speed of light, this technique cannot be used for measuring extremely small distances.