The present invention provides an optical exposer unit having a large space for containing black toner, and a color image forming apparatus comprising the optical exposer unit. In an optical exposer unit, first and second laser beams, which are reflected on the respective reflection surfaces of ...http://www.google.com.hk/patents/US5818506?utm_source=gb-gplus-share專利 US5818506 - Image forming apparatus having light beams that intersect with each other between first and second lens to provide an optical characteristic 
