Optical scanning device and image forming apparatus

An image forming apparatus comprising:

• at least one image carrier;
• and
• an optical scanning device that scans said at least one image carrier with a light flux which is modulated corresponding to image data, wherein
• the optical scanning device includes:
• 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 shorter than a combined focal length of the synchronization detection optical system in the main scanning direction,
• six different timings t1, t2, t3, t4, t5, and t6 are in a relation in which 0<t1<t2<T and 0<t3<t4<t5<t6<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 t1 to t2,
• 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 t3 to t4,
• 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 t5 to t6, 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 t1 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 t2 on the plane orthogonal to the rotation axis.

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 t1, t2, t3, t4, t5, and t6, are in a relation in which 0<t1<t2<T and 0<t3<t4<t5<t6<T, wherein 0 represents zero and T represents a time period during which the light flux from the light source is reflected on the reflection surface,
• the monitor optical system is disposed on an optical path of a light flux which is reflected on the reflection surface during a time period from t1 to t2,
• the synchronization detection optical system is disposed on an optical path of a light flux which is reflected on the reflection surface during a time period from t3 to L4,
• the scanning optical system is disposed on an optical path of a light flux which is reflected on the reflection surface during a time period from t5 to t6,
• the monitor light receiving element is disposed closer to the optical deflector than a conjugate point in the main scanning direction with respect to a cross point of:
• an extension of a line obtained by projecting the light flux reflected on the reflection surface at the timing t1 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 t2 on the plane orthogonal to the rotation axis,
• 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 t1 to t2,
• 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 t3 to t4,
• 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 t5 to 16, 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 t1 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 t2 on the plane orthogonal to the rotation axis.