| 摘要 |
995, 871. Photo-electric investigation. STANDARD TELEPHONES & CABLES Ltd. April 6, 1962 [April 7, 1961], No. 13358/62. Heading G1A. [Also in Division G4] In apparatus for reading characters a potential field representing the character is created on a body of resistive material, there being means for determining potential gradients in the field and means for identifying the character from the gradients. The character, illuminated by a lamp, is imaged onto the plate 1, Fig. 1 of photo-conductive material by lens 4. Conductors 2 and 3 secured to opposite edges apply a voltage potential across it, the equipotential lines of which would normally be parallel to each other and to the conductors 2, 3. When the character image falls on the plate the potential lines are distorted as shown at P1-P4, Fig. 2, the line P1, if this is the most positive, being pushed down towards the negative conductor and the other lines crowded in consequence. The potential in the neighbourhood of the image is therefore higher than at positions on the same horizontal level remote from the image. A horizontal line of probes such as A1, A2, A3, Fig. 1 will detect, when the image is in the left hand position shown, three different potentials, the highest being at A1 nearest the image and the least at A3. As the moving image reaches the probe A1 it detects a maximum voltage and a further movement the voltage falls. The potential values on a line of three probes therefore indicate the position of the character image in that horizontal line. The potentials are sampled when the character image lies on the centre probe by making the circuit operative when the centre probe potential is a maximum or a certain predetermined value. In Fig. 3 a straight limb of the image over the middle probe gives the potential values a1, a2, a3 where a1 = a3 and both are less than a2. Where the limb of the image is a curve open to the left, as in Fig. 4, a2 is still highest but a1 is larger than a3. A reversed relationship results from a curve open to the right. Inside a closed loop the potential is uniform, Fig. 6, so that the potentials a1 and a2 are equal and greater than a3. In Fig. 1 there are three sets of probes each in a horizontal line and the values on each set are evaluated in circuits L.C. For a character "2" the top set A1-A3 will detect a curve open to the left and the bottom set C1-C3 a curve open to the right. The middle set may detect either element. The shape elements derived are combined in a recognition circuit to indicate on one of ten leads the character sensed. The character may alternatively be sensed while stationary. Specification 825,597 is referred to. |
