Laser scanning unit and method and apparatus for calibrating a post-scan assembly in a laser scanning unit

1. A laser scanning unit comprising:

a separate upper housing portion and a separate lower housing portion;

means attaching said upper housing portion and said lower housing portion to for a housing for said laser scanning unit,

a scanning assembly including a scanning device;

a first light beam source directing a first light beam toward said scanning device;

a second light beam source directing a second light beam toward said scanning device; and

first and second post-scan optical assemblies located to receive first and second scanning beams reflected from said scanning device, each said post-scan optical assembly comprising a first, second and third fold mirror, a first f-theta lens located between said first and said second fold mirrors, and a second f-theta lens located to receive light reflected from said third fold mirror and output a compensated scanning beam for generating a scan line on a corresponding photoconductive member, each said first and second fold mirror and said first f-theta lens being mounted in said upper housing portion and each said fold mirror and said second f-theta lens being mounted in said lower housing portion.

2. The laser scanning unit as set forth in claim 1 , wherein light reflected from each of said second fold mirrors toward a respective one of said third fold mirrors lies in a plane which is generally parallel to a plane containing the light beam produced by a respective one of said first and second light beam sources.

3. The laser scanning unit as set forth in claim 1 , wherein at least one of said first and second post-scan optical assemblies includes an adjustment mechanism for adjusting its corresponding second f-theta lens whereby a scan line formed by a scanning beam passing through said corresponding second f-theta lens is adjusted.

4. The laser scanning unit as set forth in claim 3 , wherein said adjustment mechanism adjusts said corresponding second f-theta lens in linear movement in a process direction generally perpendicular to the scan line.

5. The laser scanning unit as set forth in claim 3 , wherein said corresponding second f-theta lens includes opposing,first and second longitudinal ends and said adjustment mechanism provides independent adjustment of said first and second ends to adjust one or more of a process direction position of the scan line, bow of the scan line, and skew orientation of the scan line.

6. The laser scanning unit as set forth in claim 1 , wherein said third fold mirror of at least one of said first and second post-scan optical assemblies is rotatably adjustable about a longitudinal axis of said third fold mirror to adjust the bow and process direction position of the corresponding scan line.

7. The laser scanning unit as set forth in claim 1 , wherein each of said first fold mirrors reflects a respective scanning beam inwardly and downwardly and said s and fold mirrors of said first and second post-scan optical assemblies are located substantially below said scanning device for receiving the reflected scanning beams passing through aid first f-theta lenses from said first fold mirrors.

8. The laser scanning unit as set forth in claim 1 , wherein said scanning device comprises a polygon mirror supported for rotation about a rotational axis and said first light source and said second light source are located on the same side of a plane containing said rotational axis of said polygon mirror and extending perpendicular to the scan lines, and said first and second light sources are located at substantially similar mirror mi e angles to parallel lines which are substantially parallel to the scan lines.