Abstract: When a transfer is to be performed, a setting device sets a transfer voltage value VTC, which is that at which optimum transfer is obtained, as well as a transfer assuring voltage value VAC which assures transfer. A constant-current source performs constant-current control in such a manner that the transfer voltage having the set value is applied to a transfer corona discharge device so that a constant transfer current I.sub.T will flow. As a result, the transfer corona discharge device charges printing paper to a polarity opposite that of the electric charge of toner by corona discharge, thereby transferring the toner image to the paper. A voltage detector detects a voltage V.sub.T applied to the transfer corona discharge device, and a comparator compares the detected voltage V.sub.T with the transfer assuring voltage V.sub.A. If the detected voltage V.sub.T is less than the transfer assuring voltage V.sub.

Abstract: In an electrostatic recording apparatus according to the present invention, while a photosensitive drum and a drum cleaner are enabled, but an electrostatic latent image is not formed on the drum and a developing unit is not operated yet, a light emission level of an LED, which is controlled so as to keep a received light level of a photo-diode which receives the LED's light reflected from the drum, is measured as a first light emission level. If the first light emission level exceeds a predetermined level it is determined that the detector composed of the LED and the photodiode is contaminated and requires cleaning. Next, the developer is enabled while the latent image is not formed yet. The light emission level to keep the same received light level is measured as a second light emission level. If a difference between the first and second light emission levels exceeds a predetermined limit level, it is determined that the photosensitive drum and/or carrier in developer is deteriorated.

Abstract: A printing control system is applied to a laser printer having a laser beam source for emitting a modulated laser beam, a laser beam scanner, a printing data memory to modulate a laser beam, a readout circuit for reading out printing data from the printing data memory, a beam-on signal generating circuit for generating a beam-on signal to emit a start beam from the laser beam source, a start pulse generating circuit for generating a start pulse after the detection of the start beam, and a beam-on signal resetting circuit for resetting the beam-on signal after the detection of the start pulse. The beam-on signal is forcibly turned OFF and the printing data from the printing data memory to the laser beam source is inhibited when an abnormal state of the start pulse due to an instantaneous cutoff of the laser beam is detected by the printing control system. Accordingly, printing operation is continued and stoppage of the printing is avoided even if a missing start pulse is detected.

Abstract: In a light scanning apparatus, such as in a laser printer, an optical switch is provided between a light source and an acousto-optic light-modulating element for modulating the light according to data to be printed. The optical switch may be an acousto-optic light-modulating element as well. The optical switch blocks or passes the continuously input light from the light source according to a predetermined schedule, such as eight bits prior to the start of black dots and eight bits after the end of the block dots, or during a stand-by period. The time during which a fine light spot is focused on the acousto-optic light-modulating element is thus shortened. Accordingly, the life of the acousto-optic light-modulating element is increased because of the shortened duration of the focusing of the input light. Achievement of the fine spot size allows finer print-out resolution without sacrificing scan speed or the life of the element.