Image exposure apparatus

An image exposure apparatus comprising:

• a semiconductor laser device for generating a beam;
• scanning means for causing the beam generated by said semiconductor laser device to scan a surface of a photosensitive body;
• a beam detector for detecting the arrival of the beam caused to scan by said scanning means at a predetermined position on a rotating drum bearing the photosensitive body and for generating a beam detection signal upon detecting the beam arrival;
• a bias current circuit including,
• a photodiode for monitoring an intensity of the beam generated by said semiconductor laser device;
• a comparator for determining if the intensity of the beam monitored by said photodiode exceeds a predetermined intensity value;
• and
• an up-down counter set to a sufficiently small value immediately after said semiconductor laser device begins to generate the beam, said up-down counter having a count thereof decremented when said comparator determines that the intensity of the beam has exceeded the predetermined intensity value, said up-down counter having the count thereof incremented when said comparator determines that the intensity of the beam remains below the predetermined intensity value;
• wherein said bias current circuit outputs a bias current corresponding to the count of said up-down counter in order to maintain the intensity of the beam generated by said semiconductor laser device at a time when a first reference signal is detected, said first reference signal comprising one of a clock signal and the beam detection signal;
• a driving circuit for adding the bias current from said bias current circuit and an externally input image signal and providing an output indicative thereof, said driving circuit driving said semiconductor laser device in accordance with the output of the driving circuit;
• a drum driving unit for rotating the rotating drum at a predetermined rotating speed corresponding to a second reference signal, said second reference signal comprising one of the clock signal and the beam detection signal;
• an oscillating circuit for generating the clock signal;
• and
• a switching circuit for switching said second reference signal from said clock signal to said beam detection signal, said switching circuit also switching said first reference signal for the bias current circuit from the clock signal to the beam detection signal, the switching circuit concurrently switching said first and second reference signals at a predetermined period of time after said semiconductor laser device begins to generate the beam;
• wherein said clock signal is said first and second reference signals during the predetermined period of time after said semiconductor laser device begins to generate the beam, and said beam detection signal is said first and second reference signals after the predetermined period of time after the semiconductor laser device begins to generate the beam.

An image exposure apparatus for exposing a photosensitive body comprising:

• beam emitting means for emitting a beam having an intensity to expose said photosensitive body;
• beam control means for controlling said beam emitting means, the intensity of the beam being raised gradually from a low level so as not to destroy the beam emitting means to a predetermined level higher than said low level so as to adequately expose said photosensitive body by said beam emitting means after an activation of said beam emitting means;
• scanning means for causing the beam emitted by said beam emitting means to scan the photosensitive body in a direction of main scanning at a predetermined scanning cycle;
• beam detecting means for detecting an arrival of the beam caused to scan by said scanning means at a predetermined position, said beam detecting means further generating a beam detection signal upon detecting the arrival of the beam at the predetermined position;
• reference clock generating means for generating a clock signal, said clock signal having a cycle substantially being the same as said scanning cycle;
• photosensitive body moving means for moving the photosensitive body in a direction of sub scanning at a predetermined speed in accordance with a reference signal, said reference signal being one of the clock signal and the beam detection signal;
• and
• switching means for switching said reference signal from the clock signal to the beam detection signal, said switching means switching said reference signal after detecting the beam detection signal emitted by said beam detecting means;
• wherein said photosensitive body moving means is driven in accordance with the clock signal generated by said reference clock generating means, before said beam detection signal is detected;
• said photosensitive body moving means being further driven in accordance with the beam detection signal detected by said beam detecting means, after said beam detection signal is detected.