AR-651 (serv.man11). Laser optical unit - Sharp Copying Equipment Service Manual (repair manual). Page 4

AR-651/810  LASER & OPTICAL UNIT  8 - 4

(2) Polygonal motor unit

This unit consists of the polygonal motor, polygonal

mirror and polygonal mirror cover.

a. Polygonal motor

This motor rotates the polygonal mirror at high

speed.

The DC motor controls the rotation speed of the

mirror polygon as follows:

During standby

:10,000.000 rpm (approx.)

During copying

:37,216.337 rpm (approx.)

b.

Polygonal mirror

Laser beams emitted from the laser diode are

reflected by this mirror. As the polygonal mirror

is rotated by the polygonal motor, the reflected

laser light moves in sync with the rotation. The

direction of the movement is the primary

scanning direction of the image. Two scans are

performed on one plane of the polygonal mirror.

As the polygonal mirror has eight planes, sixteen

scans are performed in one rotation of the

polygonal mirror.

c. Polygonal mirror cover

Polygonal mirror cover reduces the wind

and noise, prevents adhesion of foreign objects

onto the mirror surface and releases heat.

Laser light

Drum

Laser light

Drum

Laser light

Drum

(C)

(B)

(A)

2 scans are completed by completion of steps (A) to (C).
There are two lines of data are written on one plane of
the polygonal mirror. 16 lines of data can be written with
one rotation of the polygonal mirror.