Behr & Adams
Distance sensing apparatus and method
 Apparatus for sensing distance between a pair of indicia on a surface moving relative to the apparatus has an interval detector, a sensor and a scale device. The interval detector can respond to movement of the surface. The detector can produce an interval signal signifying the time elapsing during the passage of an interval on the surface of a predetermined length. The sensor is positioned alongside the surface for sensing the arrival times of the pair of indicia at the sensor. The scale device responds to the interval detector and sensor device for producing a distance signal signifying the ratio of the time difference in arrival of the pair to the interval signal. 
G
G01B
inventional
James E. Richard D. Clarence A.
Lewis Lewis Lewis