Patent GB-1261222-A (GB)
Title: Data processing system for curves recorded on charts
Inventor: MINAMI SHIGEO
IPC: G06T17/05
Filed: 1969-02-06
Abstract: 1,261,222. Reading charts photo-electrically. HITACHI Ltd. Feb. 6, 1969, No. 6570/69. Heading G1A. [Also in Division G4] A data processing system photo-electrically reading a curve, recorded on a chart, and deriving therefrom a new curve proportional to the moving average position of both edges of the recorded curve, comprises Fig. 1 a rotary drum 2 with driving means 1 recorded with curve 6 representing y = f 1  (x) with a certain width and curve 5 defining y = g(x) which as shown is y = a. An optical head comprises a light source focussed on the chart and a photo-transducer 12 on which is focussed light reflected from the chart; the head being translated axially of the drum by a lead screw 3 in x sense, while the drum is rotated at constant speed in y sense. A rotation of the drum produces electric signals (a) Fig. 4 wherein P 1  corresponds to line y = a and P 2  corresponds to curve y = f 1  (x) of certain width; the signals from transducer 12 being amplified and differentiated at 14 Fig. 3 to signals P<SP>1</SP> 1  and p<SP>11</SP> 1  corresponding to edges e 0 <SP>1</SP> and e a <SP>1</SP> of line 5, and P 2 1 and P 2 <SP>11</SP> corresponding to edges e o  and e a  of curve 6. These trigger generators 15, 15<SP>1</SP> of rectangular waves 4(c), 4(d) of widths equal to the intervals P 1 <SP>1</SP> , P 2 <SP>1</SP> and p<SP>11</SP> 1 , P 2 <SP>11</SP> which are summed at analog integrator 16 for display at 17 of a curve proportional to the average position of edges e o , e a  of curve 6. In a modification Fig. 5 (not shown) the rectangular waves operate gates respectively clocked from 19 direct and over delay to supply pulses numerically representative of the widths of the respective rectangular waves, which are displayed after summation at a digital integrator. In a further modification Fig. 6 (not shown) the light beam projected on the chart is of width 1 x  in the x direction and the reflected light falls on plural equally spaced photo-transducers so that the image corresponding to 1 x  is projected. Each photo-transducer supplies a transistorized circuit Fig. 7a (not shown) comprising amplifier, Schmitt shaper and trigger pulse generator, with a first rectangular wave generator utilizing a flip-flop and connected to the trigger pulse generator and a second rectangular wave generator. The outputs of the first and second wave generators for each photo-transducer circuit are summed over function setting resistors Fig. 7b (not shown) at an integrating circuit which supplies a capacitative holding circuit coupled to a recorder and filter over a FET; switching being provided for discharging the integrator and holding circuit, linked for opening and closure once per rotation of the drum. On rotation of the latter, signals representing the edge positions of the curve representing y = gx and the edge positions of the curve representing y = f 1  (x) are derived from each photo-transducer element displaced along the x axis, and operate circuits of Figs. 7a and 7b (not shown) to produce rectangular signals for each element; of widths equivalent to the intervals between corresponding edges of curves y = gx and y = f 1  (x). After weighting by the function setting resistors according to a predetermined law Fig.8 (not shown) the rectangular waves are summed at the integrating circuit; whereby if the weighting function is f 2 (x) the convolution. where a, b are values related to a projected length of the width of the photo-transducers on chart 7 Fig. 6 (not shown) and the integrator is periodically discharged and its signal transferred to the holding circuit for supply to the filter-recorder, so that for motion of the optical head one pitch in the x sense for each drum rotation, a wave proportional to the average position of the edges of curve y = fix and which is a weighted moving average of the function y = fix is recorded.