Abstract: An alignment detection apparatus for detecting the alignment of a superfine exposure system including an interrupted emission light source. The apparatus is equipped with an output variation monitoring sensor to detect an output variation of the light source and further a photoelectric conversion device to perform the photoelectric conversion of the alignment light to generate discrete photoelectric conversion signals. Also included in the apparatus is an integration and hold circuit to integrate and peak-hold each of the photoelectric conversion signals. This peak-hold values are corrected on the basis of the detected light-source output variation due to the monitoring sensor to output stepwise continuous signals from which a harmonic component is removed by a filter so as to obtain a smooth analog waveform. This analog waveform is processed by a phase detector. The output of the phase detector allows an accurate alignment irrespective of using the interrupted emission light source.

Abstract: A color printing system for color-printing images or characters on a surface of a writing sheet. The color printing system includes a plurality of printing heads which are successively arranged in parallel to each other and a feeding device for moving the writing sheet in a direction perpendicular to the head-reciprocating directions. Each of the printing heads linearly reciprocates so as to go and return in directions along the surface of the writing sheet for the color printing and has a plurality of ink-discharging nozzles. The plurality of ink-discharging nozzles are successively arranged with a pitch which is equal to or greater than twice the pitch of the finally printed lines so as to write the images or characters on the writing sheet. The feeding device moves the writing sheet in a direction perpendicular to the head-reciprocating directions by predetermined distances.