Optical scanning device and image forming apparatus

1 . An optical scanning device comprising:

a light source configured to emit a luminous flux;

a rotatable polygon mirror configured to deflect the luminous flux emitted from the light source and scan in a main scanning direction;

an optical member configured to guide the luminous flux scanned by the rotatable polygon mirror to an image bearing member;

a beam detector provided on an upstream side of the optical member in the main scanning direction and configured to output a synchronization signal corresponding to receiving the luminous flux, the synchronization signal being used to determine a writing start position on the image bearing member in the main scanning direction;

a light quantity detecting unit provided on the upstream side of the beam detector in the main scanning direction and configured to detect a light quantity of the luminous flux; and

a control unit configured to control the light source based on the signal outputted from the beam detector and the light quantity detected by the light quantity detecting unit,

wherein the light quantity detecting unit and the beam detector are arranged such that, during scanning by a same reflecting surface of the rotatable polygon mirror, the luminous flux reflected by the same reflecting surface scans over the light quantity detecting unit before scanning over the beam detector in the main scanning direction,

wherein the luminous flux reaching the light quantity detecting unit is reflected at a position closer to an end portion of a reflecting surface of the rotatable polygon mirror with respect to the main scanning direction than the luminous flux reaching the beam detector, and

wherein the light quantity detecting unit outputs a pulse signal having a pulse width corresponding to a period during which the detected light quantity exceeds a threshold, and the control unit detects deterioration of reflectance of the reflecting surface based on a change in the pulse width and corrects a light quantity of the luminous flux emitted from the light source based on the detected deterioration.

2 . An optical scanning device according to claim 1 , wherein the optical member is defined as a first optical member, and further comprising a second optical member provided between the rotatable polygon mirror and the beam detector, and configured to guide the luminous flux scanned by the rotatable polygon mirror not to the light quantity detecting unit but to the beam detector.

3 . An optical scanning device according to claim 1 ,

wherein the control unit corrects the light quantity of the luminous flux emitted from the light source based on pulse width.

4 . An optical scanning device according to claim 1 , wherein the control unit corrects a deviation of a position where the luminous flux scans in a sub-scanning direction perpendicular to the main scanning direction based on the pulse width.

5 . An optical scanning device according to claim 1 , wherein the control unit corrects a writing start position on the image bearing member in the main scanning direction based on the synchronization signal outputted from the beam detector.

6 . An optical scanning device comprising:

a light source configured to emit a luminous flux;

a rotatable polygon mirror configured to deflect the luminous flux emitted from the light source and scan in a main scanning direction;

a first optical member configured to guide the luminous flux scanned by the rotatable polygon mirror to an image bearing member;

a second optical member provided on an upstream side of the first optical member in the main scanning direction;

an output unit provided on the upstream side of the first optical member in the main scanning direction and configured to output a signal corresponding to receiving the luminous flux which is scanned by the rotatable polygon mirror and condensed in the main scanning direction by the second optical member;

a reflecting member provided on the upstream side of the second optical member in the main scanning direction and configured to reflect the luminous flux scanned by the rotatable polygon mirror and guide to the output unit without passing through the second optical member; and

a control unit configured to control the light source based on the signal outputted from the output unit,

wherein the output unit detects a light quantity of the luminous flux which is the upstream side, in the main scanning direction, of the luminous flux condensed in the main scanning direction by the second optical member and which is not condensed in the main scanning direction, and

wherein the control unit controls the light quantity of the luminous flux not condensed in the main scanning direction.

7 . An optical scanning device according to claim 6 , further comprising an optical box configured to accommodate the rotatable polygon mirror, the first optical member and the second optical member,

wherein the reflecting member is provided integrally with the optical box.

8 . An optical scanning device according to claim 7 , wherein a reflectance of the reflecting member is 30% or more.

9 . An optical scanning device according to claim 8 , wherein an incident angle at which the luminous flux scanned by the rotatable polygon mirror enters the reflecting member is 70° or more.

10 . An optical scanning device according to claim 9 , wherein the light source is rotatable and adjustable about an optical axis, and

wherein the light source is rotatably adjusted about the optical axis so that a ratio of a s-polarized light in the luminous flux reflected by the reflecting member is larger than a ratio of a p-polarized light in that.

11 . An optical scanning device, comprising:

a light source configured to emit a luminous flux;

a rotatable polygon mirror configured to deflect the luminous flux emitted from the light source and scan in a main scanning direction;

a first optical member configured to guide the luminous flux scanned by the rotatable polygon mirror to an image bearing member;

a second optical member provided on an upstream side of the first optical member in the main scanning direction;

an output unit provided on the upstream side of the first optical member in the main scanning direction and configured to output a signal corresponding to receiving the luminous flux which is scanned by the rotatable polygon mirror and condensed in the main scanning direction by the second optical member; and

a control unit configured to control the light source based on the signal outputted from the output unit,

wherein the output unit detects a light quantity of the luminous flux which is the upstream side, in the main scanning direction, of the luminous flux condensed in the main scanning direction by the second optical member and which is not condensed in the main scanning direction,

wherein the control unit controls the light quantity of the luminous flux not condensed in the main scanning direction, and

wherein the second optical member includes a first portion configured to cause the luminous flux scanned by the rotatable polygon mirror to condense in the main scanning direction and to enter the output unit, and a second portion provided on the upstream side of the first portion in the main scanning direction and configured to cause the luminous flux scanned by the rotatable polygon mirror not to condense in the main scanning direction and to enter the output unit.

12 . An optical scanning device according to claim 6 , wherein, of the luminous flux reaching the output unit, the luminous flux not condensed in the main scanning direction is reflected at a position closer to an end portion of a reflecting surface of the rotatable polygon mirror with respect to the main scanning direction than the luminous flux condensed in the main scanning direction by the second optical member.

13 . An optical scanning device according to claim 6 , wherein the rotatable polygon mirror includes a reflecting surface configured to reflect the luminous flux,

wherein the output unit detects a deterioration of a reflectance of the reflecting surface by detecting the light quantity of the luminous flux not condensed in the main scanning direction, and

wherein the control unit corrects the light quantity of the luminous flux emitted from the light source based on the light quantity of the luminous flux not condensed in the main scanning direction.

14 . An optical scanning device according to claim 6 , wherein the control unit corrects a deviation of a position where the luminous flux scans in a sub-scanning direction perpendicular to the main scanning direction based on the light quantity of the luminous flux not condensed in the main scanning direction.

15 . An optical scanning device according to claim 6 , wherein the control unit corrects a writing start position on the image bearing member in the main scanning direction based on the signal outputted from the output unit.