Abstract: The present invention relates to an apparatus for detecting an object-to-be-printed and aims at providing an apparatus for detecting an object-to-be-printed which is capable of discriminating whether the object-to-be-printed is plain paper or special paper. The apparatus includes an infrared sensor for detecting infrared rays 4 radiated by heating the object-to-be-printed 1 with heating means 2 and is capable of discriminating whether the object-to-be-printed is plain paper or special paper.

Abstract: An automatic exposure control circuit for a camera or the like includes a memory circuit comprising a series connection of a capacitor and an impedance element connected to an input of a high input impedance circuit to enable the measurement of the amount of mean light during photography under a fluorescent lamp.

Abstract: An electric shutter circuit is disclosed, which linearly varies the resistance in a bias electric power source for setting exposure factors for an automatic exposure control to thereby adjust the collector current of an electric current controlling transistor in a negative feedback circuit, and which even at the time of the manual exposure time setting, linearly varies the resistance in the bias electric power source for introducing exposure factor and setting the exposure time manually to adjust the collector current in an electric current controlling transistor in the negative feedback circuit. This circuit features that the collector current in an exposure time controlling transistor is equalized to the collector current in the electric-current controlling transistor, so that the trigger level in a comparator detector in a time constant circuit will be maintained constant.