Optical scanning device and image forming apparatus having the same

An optical scanning device comprising:

• a plurality of light sources emitting a plurality of light beams;
• an optical system having a rotary polygonal mirror deflecting the light beams from the light sources, the optical system focusing the deflected light beams onto a scanned surface to form light spots thereon, the scanned surface being optically scanned with the light spots by a rotation of the rotary polygonal mirror;
• a light-amount monitoring unit monitoring respective amounts of the light beams emitted by the light sources;
• and
• a control unit controlling the respective amounts of the light beams emitted by the light sources, based on detection signals output from the light-amount monitoring unit,
• wherein the optical scanning device is configured to satisfy the formula:
• R·m·t<0.036·n·4−0.89·n·3+8.35·n·2−37.1·n+72
• where m is the number of the light sources, t is a time needed to complete the control of the light amount of one of the light sources after monitoring of the amount of the light beam emitted by that light source, R is the number of revolutions per minute of the rotary polygonal mirror, and n is the number of reflection surfaces of the rotary polygonal mirror.

An optical scanning device comprising:

• light source means for emitting a plurality of light beams;
• optical system means for deflecting the light beams from the light source means and for focusing the deflected light beams onto a scanned surface to form light spots thereon, the optical system means having a rotary polygonal mirror, the scanned surface being optically scanned with the light spots by a rotation of the rotary polygonal mirror;
• light-amount monitoring means for monitoring respective amounts of the light beams emitted by the light source means;
• and
• control means for controlling the respective amounts of the light beams emitted by the light source means, based on detection signals output from the light-amount monitoring means,
• wherein the optical scanning device is configured to satisfy the formula:
• A<T−m·t where A is an imaging period from a start of the optical scanning of imaging information to an end of the optical scanning, m is the number of the light sources, t is a time needed to complete the control of the light amount of one of the light sources after monitoring of the amount of the light beam emitted by that light source, T is a scanning period indicated by the equation T=60/(R·n), R is the number of revolutions per minute of the rotary polygonal mirror, and n is the number of reflection surfaces of the rotary polygonal mirror.

An image forming apparatus in which an optical scanning device is provided, the optical scanning device comprising:

• a plurality of light sources emitting a plurality of light beams;
• an optical system having a rotary polygonal mirror deflecting the light beams from the light sources, the optical system focusing the deflected light beams onto a scanned surface to form light spots thereon, the scanned surface being optically scanned with the light spots by a rotation of the rotary polygonal mirror;
• a light-amount monitoring unit monitoring respective amounts of the light beams emitted by the light sources;
• and
• a control unit controlling the respective amounts of the light beams emitted by the light sources, based on detection signals output from the light-amount monitoring unit,
• wherein the optical scanning device is configured to satisfy the formula:
• A<T−m·t where A is an imaging period from a start of the optical scanning of imaging information to an end of the optical scanning, m is the number of the light sources, t is a time needed to complete the control of the light amount of one of the light sources after monitoring of the amount of the light beam emitted by that light source, T is a scanning period indicated by the equation T=60/(R·n), R is the number of revolutions per minute of the rotary polygonal mirror, and n is the number of reflection surfaces of the rotary polygonal mirror.

An optical scanning method for use in an image forming apparatus, comprising the steps of:

• providing a plurality of light sources emitting a plurality of light beams;
• providing an optical system having a rotary polygonal mirror deflecting the light beams from the light sources, the optical system focusing the deflected light beams onto a scanned surface to form light spots thereon, the scanned surface being optically scanned with the light spots by a rotation of the rotary polygonal mirror;
• monitoring respective amounts of the light beams emitted by the light sources;
• and
• controlling the respective amounts of the light beams emitted by the light sources, based on results of the light-amount monitoring;
• wherein the optical scanning method is configured to satisfy the formula:
• A<T−m·t where A is an imaging period from a start of the optical scanning of imaging information to an end of the optical scanning, m is the number of the light sources, t is a time needed to complete the control of the light amount of one of the light sources after monitoring of the amount of the light beam emitted by that light source, T is a scanning period indicated by the equation T=60/(R·n), R is the number of revolutions per minute of the rotary polygonal mirror, and n is the number of reflection surfaces of the rotary polygonal mirror.