GB1025886A - Improvements relating to pattern recognition devices - Google Patents

Abstract

1,025,886. Automatic character reading. ELECTRIC & MUSICAL INDUSTRIES Ltd. Jan. 7, 1963 [Jan. 11, 1962], No. 1042/62. Heading G4R. In a character recognition apparatus using mask-matching with positive and negative masks the masks are shaped to reduce the importance of the marginal areas of the character so that if the ink of the character " spreads " during printing the excess marginal areas are to some extent ignored. The positive mask, Fig. 6, may be made narrower than the expected character and the negative mask, Fig. 7, wider. The marginal areas D of the positive mask may be of half-transparency or of graded transparency. Excess marginal areas due to inkspread fall on the area D and their effect is reduced accordingly. The character may be imaged on the screen of an image converter tube. After passing through a half mirror the image is projected by an array of lenses on to the masks. The light passing through the masks is received in photo-cells. Signals from the cells corresponding to the positive and negative marks of each character are paired, the signals being subtracted. When the character is properly registered the light passing through the positive mask is a minimum and that through the negative mask is a maximum. The difference signal is amplified and a circuit determines which lead has the highest signal. The responses of the photo-cells are standardized for comparison by applying a reference pulse of light through the half mirror and the lenses to all the cells. The amplification of the cell or the corresponding amplifier is adjusted automatically so that each channel gives the same signal. The reference pulses occur in the fly-back time of the tube.