JPS565762A - Automatic adjusting circuit for background density in stencil paper making machine - Google Patents

Abstract

PURPOSE: To provide automatic adjustment of background density particularly in a rotary cylinder type stencil paper making machine by providing an amplifying circuit which amplifies the electrical signal obtained through photoelectric conversion of the light reflected from a copy, and analog-to-digital converting circuit, a latching circuit, an analog switching circuit and the like.

CONSTITUTION: There are provided an amplifying circuit 10 which amplifies the electrical signal obtained by photoelectric conversion (at a light-receiving element 4) of the light 3 reflected from a copy 2 placed on a base paper 1 or from the base paper 1 itself; an analog-to-digital converting circuit 20 which is composed, for example, of plural comparators and converts the output CS of the amplifying circuit 10 into a digital value D according to each of predetermined levels; a latching circuit 30 which latches the digital output D of the analog-to-digital converting circuit 20; and an analog switching circuit 40 which is turned on and off by being controlled the output of the latching circuit 30 and changes the gain of the amplifying circuit 10. Accordingly, the peak value can be latched semi-permanently and no change occurs in the gain set according to the latched value, resulting in a stable adjustment of background density.

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