Patent ID: 8913096

Claim:
An optical scanning device that scans a scanning surface in a main scanning direction, the optical scanning device comprising: a light source that includes a surface emitting laser; an optical deflector that includes a reflection surface that reflects a light flux from the light source while rotating around a rotation axis; a monitor light receiving element that receives a monitor light flux; a synchronization detection light receiving element that receives a synchronization detection light flux; a monitor optical system that directs the monitor light flux to the monitor light receiving element, the monitor light flux reflected on the reflection surface; a synchronization detection optical system that directs the synchronization detection light flux to the synchronization detection light receiving element, the synchronization detection light flux reflected on the reflection surface; and a scanning optical system that directs a scanning light flux to the scanning surface, the scanning light flux reflected on the reflection surface, wherein a combined focal length of the monitor optical system in the main scanning direction is smaller than a combined focal length of the synchronization detection optical system in the main scanning direction, six different timings t 1 , t 2 , t 3 , t t 5 , and t 6 are in a relation in which 0<t 1 <t 2 <T and 0<t 3 <t 4 <t 5 <t 6 <T specify distinct timings during which each of the monitor light flux, the synchronization detection light flux, and the scanning light flux is individually reflected on the reflection surface, and T represents a time period during which each of the monitor light flux, the synchronization detection light flux, and the scanning light flux from the light source is sequentially reflected on the reflection surface, the monitor optical system is disposed on an optical path of the monitor light flux, which is reflected on the reflection surface during a time period from t 1 to t 2 , the synchronization detection optical system is disposed on an optical path of the synchronization detection light flux, which is reflected on the reflection surface during a time period from t 3 to t 4 , the scanning optical system is disposed on an optical path of the scanning light flux, which is reflected on the reflection surface during a time period from t 5 to t 6 , and the monitor light receiving element is in a conjugate relationship in the main scanning direction with a cross point of: an extension of a line obtained by projecting the light flux reflected on the reflection surface at the timing t 1 on a plane orthogonal to the rotation axis; and an extension of a line obtained by projecting the light flux reflected on the reflection surface at the timing t 2 on the plane orthogonal to the rotation axis.