Light scanning unit, method of detecting failure of synchronization signal, and electrophotographic image forming apparatus using light scanning unit

A method of detecting a failure of a synchronization signal of a light scanning unit comprising a light source which emits a light beam according to an image signal, a light deflector which deflects and scans the light beam emitted from the light source in a main scanning direction, and a synchronization sensor which receives a portion of the light beam deflected and scanned from the light deflector to the synchronization signal and comprises an effective light-receiving surface whose width in the main scanning direction varies in a sub scanning direction, the method comprising:

• driving the light source;
• driving the light deflector;
• receiving the portion of the light beam deflected and scanned from the light deflector to detect the synchronization signal;
• and
• if a width of the detected synchronization signal is smaller than a reference value, determining the detected synchronization signal as a failure, and if the width of the detected synchronization signal exceeds the reference value, determining the detected synchronization signal as high quality.

An electrophotographic image forming apparatus comprising:

• image holding bodies;
• light scanning units which scan light beams onto to-be-scanned surfaces of the image holding bodies to form electrostatic latent images;
• and
• developers which feed toners to the electrostatic latent images formed on the image holding bodies to develop the electrostatic latent images,
• wherein the light scanning units comprise:
• light sources which emit light beams according to image signals;
• light deflectors which deflect and scan the light beams emitted from the light sources in a main scanning direction;
• and
• synchronization sensors which receive portions of the light beams deflected and scanned from the light deflectors to detect synchronization signals and comprise effective light-receiving surfaces whose widths vary in a sub scanning direction.

An electrophotographic image forming apparatus comprising:

• an image holding body;
• a light scanning unit configured to scan light beams onto a to-be-scanned surface of the image holding body to form an electrostatic latent image;
• and
• a developer which feeds toner to the electrostatic latent image formed on the image holding body to develop the electrostatic latent image, wherein the light scanning unit comprises:
• a light source which emits a light beam according to image signals;
• a light deflector which deflects and scans the light beam emitted from the light source in a main scanning direction;
• and
• a synchronization sensor which receives portions of the light beam deflected and scanned from the light deflector to detect a synchronization signal and comprises an effective light-receiving surface whose width varies in a sub scanning direction.