Opto-mechanical instrument to accurately measure linear distances on flat or curved surfaces

摘要

A self-contained, electronic, hand-held scaler for a map or other illustration uses a rotary element and an optical sensor at its tip to generate digital pulses when the tip is moved over a map surface. The pulses are counted by a microprocessor that also operates on different pulse counts to automatically scale distances on the map. The microprocessor is supplied with the number of, eg., miles on the scale line of the map and the tip is then run over the length of the scale line; the processor uses the ratio of the number and the pulse count to scale an arbitrary distance on the map. A digital readout shows the scaled distance in, eg., miles corresponding to the line run over the map. The rotary element can be a wheel in an axle or a sphere held in a retainer, like a ball-point pen ball. The sensor has a lamp and photocell to generate pulses by a pattern of reflective and non-reflective areas on the rotary element. The housing has switches for resetting, calibrating, and initializing, a map-illuminating light. Battery power is cut off after long non-use.