Optical scanning device and image forming apparatus

1. An optical scanning device comprising:

a rotating polygon mirror that rotates and deflects light that has been emitted from a light source;

a plate member that is disposed above the rotating polygon minor and having a first plane adjacent to the rotating polygon mirror that intersects orthogonally with a rotational axis of the rotating polygon mirror and a second plane that is distanced away from the rotating polygon minor relative to the first plane at an outer periphery of the first plane.

2. The optical scanning device of claim 1 , wherein the distance between the first plane of the plate member and an upper surface of the rotating polygon mirror parallel to the plate member is approximately 1.3 mm or less.

3. The optical scanning device of claim 2 , wherein a center of the first plane when seen from an axial direction of a rotating shaft of the rotating polygon minor is disposed substantially on the rotating shaft.

4. The optical scanning device of claim 3 , wherein the difference between a radius of a circumscribed circle of the rotating polygon minor and a radius of the first plane is approximately 2 mm or less when seen from the axial direction of the rotating shaft of the polygon minor.

5. The optical scanning device of claim 1 , wherein the plate member comprises a hole that penetrates the plate member and that is formed in the first plane, the hole connecting an inside and an outside of the optical scanning device.

6. The optical scanning device of claim 1 , further comprising

a side wall member that supports the plate member, and a lens member that transmits light deflected by the rotating polygon minor,

wherein the side wall member and the lens member surround deflection surfaces of the rotating polygon minor, and a part of the surrounding of the rotating polygon mirror is open.

7. An image forming apparatus comprising:

the optical scanning device of claim 1 ; and

a photoconductor on whose surface an electrostatic latent image is formed as a result of being irradiated with the light that has been emitted by the optical scanning device.

8. The optical scanning device of claim 1 , wherein the plate member is an upper cover of the optical scanning device.

9. The optical scanning device of claim 1 , wherein the first plane is configured to substantially coincide with a circumscribed circle of the rotating polygon mirror when seen from an axial direction of a rotating shaft of the rotating polygon minor.

10. The optical scanning device of claim 1 , wherein the first plane entirely covers an upper surface of the rotating polygon minor, and

the plate member further comprises a longitudinal portion extending along an axis from the outer periphery of the first plane in a direction away from the rotating polygon minor to make a connection with the second plane.

11. The optical scanning device of claim 10 , wherein the second plane extends in a horizontal direction to make a connection with an edge of a side wall member, and

the first plane, the longitudinal portion, and the second plane form a step portion.