Abstract: An apparatus for converting an analog image signal to a digital image signal based on a reference voltage, includes a counter having a control terminal, for counting a first signal and outputting a counted value in digital form, a D/A converter for converting the counted value to an analog voltage signal served as the reference voltage, an A/D converter for converting the analog image signal to the digital image signal based on the reference voltage generated by the D/A converter, and a comparator for comparing in magnitude the digital image signal and a threshold level used for limiting the magnitude of the digital image signal, thereby outputting a control signal based on the results of comparison. The counter continues to count the first signal until the control signal derived from the comparator is supplied to the control terminal of the counter.

Abstract: An image forming apparatus has a control device for controlling an optical output of a semiconductor laser. An operation of controlling the optical output is started with a timing before an incoming signal which indicates an effective image region in a sub scanning direction of a photosensitive body and responsive to a timing signal (or power check start signal) having a predetermined period.

Abstract: An image forming apparatus includes a fixing speed setting unit for selectively setting the fixing speed in accordance with a desired mode of operation, a fixing unit for fixing a reproduced image of an original formed on a image forming medium at a variable fixing speed in accordance with the fixing speed setting unit, and a scanning unit provided with opto-electrical elements arranged in one line extended laterally to a predetermined scanning direction for optically receving an image of the original through the opto-electrical elements. The opto-electrical elements are carrying out a scanning operation in the predetermined scanning direction with varied scanning speed by changing a sweep spacing of an image data with averaging every N line of the image data in accordance with the operation mode with using every N-1 lines of the image data to reproduce the image of the original on the image forming medium.

Abstract: An image forming apparatus comprising a photosensitive body, a scanner including a laser light source for scanning the photosensitive body by a laser beam emitted from the laser light source, a modulation circuit for pulse-width-modulating or pulse-number-modulating the laser beam by an input digital image data which is synchronized to a clock signal, and a driving circuit for driving the laser light source by an output modulated image data of the modulation circuit. The modulation circuit includes a high-speed clock generator for generating a high-frequency clock signal which has a frequency higher than the clock signal, a counter for counting pulses of the high-frequency clock signal, a resetting circuit for resetting the counter when a counted value reaches a predetermined value, and a pulse signal generator for generating as the modulated image data a pulse signal having a pulse width or number dependent on the input digital image data and the counted value of the counter.

Abstract: A semiconductor laser control apparatus for controlling an optical output of a semiconductor laser to a predetermined value comprises a switching part coupled in series with the semiconductor laser and controlled by an N-bit image signal, N constant current supply circuits coupled in parallel to each other and in series with the switching part for supplying currents to the switching part so that a driving current is supplied to the semiconductor laser from the switching part, a detector for detecting the optical output of the semiconductor laser and for outputting a detection signal indicative of the detected optical output, and a control part responsive to the detection signal from the detector for controlling the driving current by controlling the N constant current supply circuits so that the optical output of the semiconductor laser becomes the predetermined value.

Abstract: An exposure value control system for a copying machine of the narrow slit exposure type in which a fluorescent lamp and a fiber lens array are used as a source of light and an imaging optical system, respectively. This exposure value control system comprises a lighting device for the fluorescent lamp, a manually-adjustable D-C voltage generator, and control means for electrically controlling a lamp current supplied from the lighting device to the fluorescent lamp in dependence upon the D-C voltage from the generator.

Abstract: An effective voltage across a load such a lamp (L) is squared by means of a field effect transistor (FET) to produce an output voltage which varies in proportion to the power through the load (L). A trigger phase of a thyristor (TRC) connected between an A.C. power source (PS) and the load (L) is automatically varied in such a manner that the output voltage and thereby the power through the lamp (L) are regulated to a desired value.