Multi-beam optical scanning device

Abstract

It is an object of the present invention to realize a multi-beam optical scanning device which is suitable for high speed and high recording density by almost completely offsetting and correcting a deviation of focusing positions in a main scanning direction of plural spots in an entire surface to be scanned without deteriorating focusing properties at all. The multi-beam optical scanning device includes: a light source device 1 having plural luminescence parts; a rotating polygon mirror 5 ; a first optical system 2 which converts plural light beams into convergent light beams or divergent light beams; and a third optical system 6 which guides the light beams onto a surface to be scanned 7 of a drum shape, and when it is assumed that a maximum value of a positional deviation amount generated in a first direction is δY 1 , a maximum value of a positional deviation amount generated in a second direction is δY 2 , and a maximum value of a positional deviation amount generated in a third direction is δY 3 , conditional expression (1) is satisfied.

1 - 10 . (canceled) 
   
   
       11 . A multi-beam optical scanning device comprising:
 light source means which has plural luminescence parts arranged apart from each other in both a main-scanning direction and a sub-scanning direction;   a rotating polygon mirror which defines a deflection plane, and which scans plural light beams emitted from the plural luminescence parts, respectively;   an incidence optical system which is arranged in an optical path leading from the light source means to the rotating polygon mirror, and which converts the plural light beams into convergent light beams or divergent light beams; and   an imaging optical system which images the plural light beams scanned in the deflection plane of the rotating polygon mirror onto a surface to be scanned, wherein the surface to be scanned is formed in a drum-like shape of which a rotation axis thereof extends along the main-scanning direction,   wherein δY 1  is defined as a maximum value of a first relative positional deviation, and the first relative positional deviation is generated when, in a sub-scanning section, the respective light beams to be made incident on the surface to be scanned are made incident such that principal rays thereof form a finite angle with respect to a normal line of the surface to be scanned, respectively, whereby the first relative positional deviation is generated between imaging points on the surface to be scanned in a first direction in parallel with the main-scanning direction,   wherein δY 2  is defined as a maximum value of a second relative positional deviation, and the second relative positional deviation is generated when, in a main scanning section, the convergent light beams or divergent light beams scanned in the deflection plane of the rotating polygon mirror are made incident on the imaging optical system, whereby the second relative positional deviation is generated between imaging points on the surface to be scanned in a second direction,   wherein δY 3  is defined as a maximum value of a third relative positional deviation, and the third relative positional deviation is generated when the plural light beams emerged from the plural luminescence parts have relative differences in respective wavelength thereof, whereby the third relative positional deviation is generated between imaging points on the surface to be scanned in a third direction in parallel with the main-scanning direction, and   wherein the conditional expression of
   |δ Y 1 +δY 2 +δY 3|≦0.014 (mm) 
   
     is satisfied, and the second direction and the third direction are directions opposite the first direction. 
   
   
       12 . An image forming apparatus comprising:
 the multi-beam optical scanning device according to  claim 11 ;   a photosensitive member arranged on the surface to be scanned;   a developing device which develops an electrostatic latent image, which is formed on the photosensitive member by a light beam used for scanning in the multi-beam optical scanning device, as a toner image;   a transfer device which transfers the developed toner image onto a material to have an image transferred thereon; and   a fixing device which fixes the transferred toner image to the material to have an image transferred thereon.   
   
   
       13 . An image forming apparatus comprising:
 the multi-beam optical scanning device according to  claim 11 ; and   a printer controller which converts code data inputted from an external device into an image signal and inputs the image signal to the multi-beam optical scanning device.