Patent ID: 7538926

Claim:
An optical scanning device, comprising: light source means; deflecting means configured to scanningly deflect a light beam emitted from said light source means; and an imaging optical system configured to image the light beam scanningly deflected by said deflecting means, upon a scan surface to be scanned, wherein said deflecting means includes an oscillating element configured to reciprocally scan the scan surface with the light beam from said light source means, wherein relations ( dθ max /dt max )<( dθ 0 /dt 0 ) ( dY 0 /dθ 0 )<( dY max /dθ max ) ( dθ 0 /dt 0 )<( dθ 0.5 /dt 0.5 ) and ( dY 0.5 /dθ 0.5 )<( dY 0 /dθ 0 ) are satisfied throughout a whole effective scan region on the scan surface, where θ 0 is the deflection angle of said oscillating element as the light beam scans a centre position Y 0 of the effective scan region on the scan surface with respect to the main-san direction, and dθ 0 /dt 0 is an angular speed of said oscillating element at that time, θ max is a maximum deflection angle of said oscillating element as the light beam scans a maximum scan position Y max in the effective scan region on the scan surface with respect to the main-scan direction, and dθ max /dt max is the angular speed of said oscillating element at that time, θ 0.5 is the deflection angle of said oscillating element as the light beam scans a scan position Y 0.5 corresponding to 50% of the maximum scan position Y max in the effective scan region on the scan surface with respect to the main-scan direction, and dθ 0.5 /dt 0.5 is the angular speed of said oscillating element at that time, dY 0 is an amount of change at the centre position Y 0 on the scan surface with respect to the main-scan direction, with reference to an amount of change dθ 0 of said oscillating element at the deflection angle θ 0 , dY max is an amount of change at the maximum scan position Y max on the scan surface with respect to the main-scan direction, with reference to an amount of change dθ max of said oscillating element at the maximum deflection angle θ max , and dY 0.5 is an amount of change at the scan position Y 0.5 on the scan surface with respect to the main-scan direction, with reference to an amount of change dθ 0.5 of said oscillating element at the deflection angle θ 0.5 .