| 摘要 |
<p>PURPOSE: To prevent an operating failure from occurring, even if an image density is high by changing the emission duty ratio of a light-emitting diode in accordance with the detected temperature of a temperature detection means, in an area in which the cumulative value of a black pixel exceeds a specified level. CONSTITUTION: A control CPU in a printer control circuit 402 monitors the surface temperature of a switching element for an LED turning-on power supply 435 by a temperature detection signal from a thermister. If the control CPU detects that the surface temperature of the switching element exceeds a limited level, and, by an input signal from a black data count means, that the proportion of black data of image data has increased, the control CPU controls ROM for controlling a quantity of emitted light so that the pulse width of an emission enable signal decreases by changing a signal for selecting a quantity of emitted light. Thus a pulse width for the quantity of emitted light of an LED element 406 is reduced and the number of times of light emission is decreased so that the lighting energy of the LED element 406 is saved with the diminishment of the number of times of light emission to inhibit an increase in the temperature of the LFD turning-on power supply 435.</p> |
