METHOD OF CLASSIFYING CHARACTERS WHEREIN THE EFFECTS OF VARIATIONS IN CONTRAST BETWEEN A PRESENTED CHARACTER AND ITS BACKGROUND AND VARIATIONS IN BACKGROUND BRIGHTNESS ARE REDUCED, AND THE APPARATUS THEREFOR

摘要

A method of reducing the effects upon character classification attributed to variations in the contrast between a presented character and its background and to variations in background brightness, and the apparatus therefor, are disclosed in accordance with the teachings of the present invention. A presented character is partitioned into a plurality of raster areas and a voltage representing the light intensity of each raster area is produced. A reference voltage proportional to the light intensity of a background area is also produced and difference voltages corresponding to the difference between the reference voltage and each raster area voltage are generated. The difference voltages together with the reference voltage are combined in resistor networks representing predetermined classes of characters to produce output voltages. Each output voltage is compared to a comparison voltage to determine which output voltages lie within certain predetermined limits. The presented character corresponds to the one predetermined class of characters represented by those resistor networks that produce such proper output voltages.