Optical scanning device and image forming apparatus using the same

Abstract

An optical scanning device includes a synchronism detecting element for detecting a light beam scanningly deflected by a deflecting surface of an optical deflector, to determine an image-writing start position of the light beam on a scan surface in a main-scan direction, and a synchronism detecting optical element for directing the light beam scanningly deflected by the optical deflector to the synchronism detecting element, wherein the synchronism detecting optical element is comprised of a prism having a plurality of reflecting surfaces being unified and having a power in a sub-scan direction, and wherein, in a sub-scan section, the prism is configured to place the deflecting surface of the optical deflector and a light-receiving surface of the synchronism detecting element in an optically conjugate relationship with each other.

1 . An optical scanning device, comprising:
 light source means;   an optical deflector configured to scanningly deflect a light beam emitted from said light source means;   an imaging optical system configured to image the light beam scanningly deflected by a deflecting surface of said optical deflector, upon a scan surface to be scanned;   a synchronism detecting element configured to detect the light beam scanningly deflected by the deflecting surface of said optical deflector, to determine an image-writing start position of the light beam on the scan surface in a main-scan direction; and   a synchronism detecting optical element configured to direct the light beam scanningly deflected by the deflecting surface of said optical deflector to said synchronism detecting element;   wherein said synchronism detecting optical element is comprised of a prism having two flat surfaces providing reflection surfaces, the flat surfaces defining a right angle in the sub-scan section and being unified, said prism having a power in the sub-scan direction,   wherein, in a sub-scan section, said prism is configured to place the deflecting surface of said optical deflector and a light-receiving surface of said synchronism detecting element in an optically conjugate relationship with each other, and   wherein, when an imaging magnification in the sub-scan direction between the deflecting surface of said optical deflector and the light-receiving surface of said synchronism detecting element is denoted by βbd, a relation
   0.5< |βbd|< 1.5 
   
     is satisfied. 
   
   
       2 . An image forming apparatus, comprising:
 an optical scanning device as recited in  claim 1 ;   a photosensitive drum disposed at a scan surface to be scanned;   a developing device for developing an electrostatic latent image formed on said photosensitive drum surface with a light beam scanningly deflected by said optical scanning device, to produce a toner image;   a transferring device for transferring the developed toner image onto a transfer material; and   a fixing device for fixing the transferred toner image, on the transfer material.   
   
   
       3 . An image forming apparatus, comprising:
 an optical scanning device as recited in  claim 1 ; and   a printer controller for converting code data supplied from an outside machine into an image-wise signal and for inputting the image-wise signal into said optical scanning device.