A line-drawing pattern recognizer

• Authors: Leon D. Harmon
• Venue: IRE-AIEE-ACM '60 (Western) Papers presented at the May 3-5, 1960, western joint IRE-AIEE-ACM computer conference
• Year: 1960

A machine is described which recognizes line drawings of circles, triangles, squares, pentagons, and hexagons. This identification is independent of rotation and, within limits, of size, precision of drawing, or positioning. The system will also distinguish and count separate objects up to six with limited independence of the size, shape and position of each object. This "Gestalt" recognition is accomplished by using a dilating circular scan. The virtue of such scanning is that object-size changes translate into time-of-arrival changes while object rotation preserves topological relationships. The n-gon detection depends on side counting, and the object counter uses the same logic in conjunction with a detection of discontinuities. Thirty-two small photocells arrayed in a circle are mechanically puckered across the input plane. Light signals derived from opaque line-drawings are converted into "binary representation in a special thyratron register. Time sequencing of logical operations and output displays is relay controlled. The actual decision logic uses a novel combination of optical and electronic devices in a simple but effective manner. It is also shown that this circular scan technique is applicable to automatic detection of letters and numbers over a wide variety of styles, and several examples are given.