Patent GB-850500-A (GB)
Title: Apparatus for analysing the distribution of a variable quantity
Inventor: TAYLOR WILFRED KENELM
IPC: G06V10/36
Filed: 1957-08-29
Abstract: 850,500. Recognizing characters. NATIONAL RESEARCH DEVELOPMENT CORPORATION. Aug. 29, 1958 [Aug. 29, 1957], No. 27274/57. Class 106 (1). [Also in Group XXXVI] Apparatus for analysing the distribution over an area of a variable quantity comprises means for producing representative signals from a number of zones of the area, a resistance network comprising a plurality of pairs of terminals to one of which (the transfer terminal) is applied the representative signal and to the other of which (the output terminal) is applied a fraction of the same signal, each transfer terminal being connected by equal resistors with a number of adjacent output terminals and vice versa, the arrangement being such that modified signals are obtained from the output terminals which are greater at those output terminals corresponding to zones where the quantity is changing in magnitude and are smaller or zero where the magnitude is constant. The input signals may be voltages derived from light-sensitive transducers, e.g. a matrix of photo-cells P1-P9, Fig. 7, a character image being projected on to them as shown in Fig. 6. The signals are applied through inverting amplifiers A1-A9 to transfer terminals T1-T9 and through resistors r1-r9 to the output terminals 01-09. The matrix is shown in Fig. 1. The inputs on terminals I1 to I9 are applied through resistors r to the output terminals 0, shown as inner rings, and through amplifiers A to the transfer terminals T, shown as outer rings. The transfer terminals are connected by eight resistors R to each of the nearest output terminals. The gain of amplifiers A and the values of resistors rand R are so chosen that input signals over regions of constant signal can be eliminated, the positive signal through resistor r being balanced by the combined negative signals through resistors R from the eight connected transfer terminals. This balance does not apply where the magnitude signal of the signal of a zone is different from the adjacent zones. In Fig. 2a the input signals are shown as background values ib plus an amount # on certain terminals corresponding to a light-coloured character " T." The effect of the resistance network of Fig. 1 is to produce signals on the output terminals O as shown in Fig. 2b, the shape of the T being represented by positive signals and surrounded by negative signals. A rectifier may be connected to each terminal O as shown in Fig. 1 to eliminate the negative signals and the result is therefore as shown in Fig. 2c the extremities of the letter giving a larger signal than the centre part. If the letter is printed in dark ink, the corresponding zones have a smaller signal ib - # as shown in Fig. 3a. The matric produces the signals of Fig. 3b and the rectifier may eliminate the negative signals to leave an outline of the character, Fig. 3c. Diagonal connections in the network may be omitted or connections may also be made to more remote neighbouring terminals. Matrix construction.-The matrix may be formed by cutting or moulding grooves (or tunnels) 9, Fig. 4, in the surface of four insulating slabs, the grooves connecting alternate rows of input terminals and passing at 45 degrees through their intersections. The grooves are filled with resistive material and a conductive disc D makes contact with it at each terminal point. Two holes H of different sizes are made in each disc and the underlying resistive and insulating materials and the holes alternate in position as shown. The four slabs are arranged one above the other as shown in Fig. 4e, conductors W are passed through the holes making contact with the smaller holes but not with the larger holes. Wires W1 form the transfer terminals T and wires W2 form the output terminals O. Because of the longer length of diagonal grooves the resistance is greater than for vertical or horizontal grooves but the function of the network is unimpaired. Specification 831,741 is referred to.