Optical scanning apparatus including an image reading section and an image printing section that share a common optical system and a method of printing and reading an image using the common optical system

An optical scanning apparatus comprising:

• a light source disposed inside a case that emits a light beam in a light path;
• a deflector that deflects the light beam from the light source;
• a photosensitive member that receives the deflected light beam and forms an electrostatic latent image based on the light beam;
• a source document support section that supports a source document for reading disposed opposite to the photosensitive member;
• a reflecting device located between the photosensitive member and the source document support section that selectively reflects the light beam from the deflector to the source document support section to read a source document and to the photosensitive member to form an electrostatic latent image on the photosensitive member,
• wherein the case for the light source also houses a light path separation device including a beam splitter that separates the light beam in the light path from the light source and the light beam from reading the source document, and directs the light beam from the source document to a photosensor that converts the light beam to electrical signals, wherein the beam splitter separates the light beam based on a diffraction effect;
• and
• a light blocking device located on the light path that prevents diffracted light produced by the beam splitter from reaching the photosensitive member and the source document.

A method of printing an image and reading an image using a common optical system, comprising the steps of:

• emitting a light beam in a light path from a light source;
• deflecting the light beam to a reflector;
• positioning the reflector to reflect the light beam to one of a printing section and a reading section;
• forming an image based on the light beam at the printing section when the light beam is reflected to the printing section;
• and
• reading the source document by reflecting the light beam from the source document back toward the light source to a photosensor to convert the light beam to electrical signals when the light beam is reflected to the reading section, including blocking diffracted light from the light beam from reaching the photosensor and the source document.