Image forming apparatus

A scanning optical device comprising:

• a plurality of laser sources;
• scanning means for scanning laser beams emitted by said plurality of laser sources;
• two light-receiving elements juxtaposed in a main scanning direction to detect the laser beams scanned by said scanning means;
• means for comparing output signals from said two light-receiving elements, and outputting a reference timing signal indicating that each of the scanned laser beams has reached a substantially middle position between said two light-receiving elements;
• and
• control means for synchronizing write operations of said plurality of laser sources in the main scanning direction on the basis of the reference timing signal.

A method of detecting a write start position in a main scanning direction in an image forming apparatus having a plurality of laser sources, comprising the steps of:

• scanning laser beams emitted by said plurality of laser sources;
• detecting the scanned laser beams scanned by two light-receiving elements juxtaposed in the main scanning direction;
• comparing output signals from said two light-receiving elements, and outputting a reference timing signal indicating that each of the scanned laser beams has reached a substantially middle position between said two light-receiving elements;
• and
• synchronizing write operations of said plurality of laser sources in the main scanning direction on the basis of the reference timing signal.

An image forming apparatus comprising:

• a plurality of laser sources;
• scanning means for scanning laser beams emitted by said plurality of laser sources onto a recording medium;
• two light-receiving elements juxtaposed in a main scanning direction to detect the laser beams scanned by said scanning means;
• means for comparing output signals from said two light-receiving elements, and outputting, for said plurality of laser sources, reference timing signals each indicating that each of the scanned laser beams has reached a substantially middle position between said two light-receiving elements;
• and
• control means for synchronizing write operations of said plurality of laser sources in the main scanning direction on the basis of the reference timing signals respectively outputted for said plurality of laser sources.

A scanning optical device comprising:

• a plurality of laser sources;
• scanning means for scanning laser beams emitted by said plurality of laser sources;
• two light-receiving elements juxtaposed in a main scanning direction to detect the laser beams scanned by said scanning means;
• means for comparing output signals from said two light-receiving elements, and outputting, for said plurality of laser sources, reference timing signals each indicating that each of the scanned laser beams has reached a substantially middle position between said two light-receiving elements;
• and
• control means for synchronizing write operations of said plurality of laser sources in the main scanning direction on the basis of the reference timing signals respectively outputted for said plurality of laser source.

A method of detecting a write start position in a main scanning direction in an image forming apparatus having a plurality of laser sources, comprising the steps of:

• scanning laser beams emitted by said plurality of laser sources;
• detecting the scanned laser beams scanned by two light-receiving elements juxtaposed in the main scanning direction;
• comparing output signals from said two light-receiving elements, and outputting, for said plurality of laser sources, reference timing signals each indicating that each of the scanned laser beams has reached a substantially middle position between said two light-receiving elements;
• and
• synchronizing write operations of said plurality of laser sources in the main scanning direction on the basis of the reference timing signals respectively outputted for said plurality of laser sources.