Optical scanning apparatus and image forming apparatus using it

An optical scanning apparatus comprising:

• a light source having a plurality of light-emitting portions arranged as inclined with respect to a main scanning direction;
• a deflector for deflecting a plurality of light beams emitted from said light source;
• an imaging system for guiding the plurality of light beams deflected and reflected by said deflector, onto a scanned surface;
• a photosensor arranged substantially at the same position as said scanned surface and in a normal direction to said main scanning direction, said photosensor detecting scanning positions of the plurality of light beams and a difference between pass times of the plurality of light beams, thereby detecting deviation of the scanning positions and variation of magnification;
• a correction system for correcting drawing positions of the plurality of light beams on said scanned surface;
• and
• a temperature detector provided in said optical scanning apparatus,
• wherein said temperature detector detects a temperature in said optical scanning apparatus after power-on of said optical scanning apparatus and said correction system corrects the drawing positions of the plurality of light beams, based on the result of detection by said photosensor, in accordance with change of the temperature detected, or every time the temperature detected reaches a preset temperature.

An optical scanning apparatus comprising:

• a light source having a plurality of light-emitting portions arranged as inclined with respect to a main scanning direction;
• a deflector for deflecting a plurality of light beams emitted from said light source;
• an imaging system for guiding the plurality of light beams deflected and reflected by said deflector, onto a scanned surface;
• a photosensor arranged substantially at the same position as said scanned surface and in a normal direction to said main scanning direction, said photosensor detecting scanning positions of the plurality of light beams and a difference between pass times of the plurality of light beams, thereby detecting deviation of the scanning positions and variation of magnification;
• a correction system for correcting drawing positions of the plurality of light beams on said scanned surface;
• and
• a time counter for measuring a time after power-on of said optical scanning apparatus,
• wherein said correction system corrects the drawing positions of the plurality of light beams, based on the result of detection by said photosensor, in accordance with the time measured by said time counter, or at a preset time.

An image forming apparatus comprising:

• a light source having a plurality of light-emitting portions arranged as inclined with respect to a main scanning direction;
• a deflector for deflecting a plurality of light beams emitted from said light source;
• an imaging system for guiding the plurality of light beams deflected and reflected by said deflector, onto an image carrier surface;
• a photosensor arranged substantially at the same position as said image carrier surface and in a normal direction to said main scanning direction, said photosensor detecting scanning positions of the plurality of light beams and a difference between pass times of the plurality of light beams, thereby detecting deviation of the scanning positions and variation of magnification;
• a correction system for correcting drawing positions of the plurality of light beams on said image carrier surface;
• and
• a printed-sheet counter for calculating a number of printed sheets after power-on of said image forming apparatus,
• wherein, based on a signal from said printed-sheet counter, said correction system corrects the drawing positions of the plurality of light beams, based on the result of detection by said photosensor.

An optical scanning apparatus comprising:

• a light source having a plurality of light-emitting portions arranged as inclined with respect to a main scanning direction;
• a deflector for deflecting a plurality of light beams emitted from said light source;
• an imaging system for guiding the plurality of light beams deflected and reflected by said deflector, onto a scanned surface;
• a photosensor arranged substantially at the same position as said scanned surface and in a normal direction to said main scanning direction, said photosensor detecting scanning positions of the plurality of light beams and a difference between pass times of the plurality of light beams, thereby detecting deviation of the scanning positions and variation of magnification of said optical scanning apparatus;
• and
• a correction system for correcting drawing positions of the plurality of light beams on said scanned surface, based on the result of detection by said photosensor.

An optical scanning apparatus comprising:

• a light source having a plurality of light-emitting portions;
• a deflector for deflecting a plurality of light beams emitted from said light source;
• an imaging system for guiding the plurality of light beams deflected by said deflector, onto a scanned surface;
• a photosensor for detecting deviation of scanning positions and variation of magnification of the plurality of light beams ocurring with environmental changes of said optical scanning apparatus;
• and
• a correction system for correction drawing positions of the plurality of light beams on said scanned surface, based on the result of detection by said photosensor.