| Abstract: | Summary A source of light emils light, the intensity of which varies with a frequency which is kept constant by means of an oscillating
quartz crystal. A plane mirror is placed at a distance of 10–30 km from the source of light. The mirror reflects the light
back to a phototube placed in the neighbourhood of the source of light. The above-mentioned crystal controls the sensitivity
of the tube, which thus varies with the same frequency as the source of light. Thereby, the electrical currents from the tube
will vary with the distance, depending on whether the incoming light impulses are more or less timed to the cycles of sensitivity
of the phototube. Thus the variation of the current is periodic with the distance. With the actual rate of crystal frequency,
the same strength of current is repeated every 18th meter that the mirror is moved. When measuring distances the periodical
change with the distance is employed as a scale. The size of the scale is once and for all determined from a known distance.
A special arrangement causes the currents to reverse every 9th meter of change in distance. Thus the currents pass through
zero and have their greatest rate of change in relation to a change in distance. The 0-points represent the division-lines
of the scale of distance used. The constancy of the distance between the division-lines is directly dependent on the constancy
of the frequency. The determination of a distance is accurate to about one in one million. |
