PATTERN ANALYZER

A pattern analyzer includes a sensor (19) for picking up an image of a pattern at a plurality of sampling points and for producing a shade signal representing the depth of shade at each sampling point. The sampled shade signals are temporarily stored in a memory (23) and, at the same time, are classified into different shade depths by a histogram forming circuit (30, 31, 32 and 33). The result of the classification is such that an amount of classified shade signals reaches a peak at two different shade depths. A threshold level determining circuit (34, 35, 36 and 37) is provided for determining a threshold level of shade depth between the two different shade depths. Also, a comparator (38, 39, 40 and 41) is provided for comparing the shade signals stored in the memory with the threshold level and for producing a 1-bit binary signal for each shade signal.