Sharp AL-840, Digital Copier, AL-800 service manual Image process section

The scanning mirror is a 6-surface mirror. Six lines are printed for one rotation of the scanning motor. Laser beams reflected by the scan- ning mirror are passed to the curved mirror by the No. 1 reflection mirror. Before reaching the curved mirror, the laser beams enter the laser beam sensor on the start position detection PWB to make horizontal synchronization (generating SYNC signal).

The laser beams from No. 1 reflection mirror are arranged to be parallel beams by the curved mirror and passed to No. 3 reflection mirror. The laser beams reflected by No. 3 reflection mirror are passed through No. 2 cylinder lens to the photoconductor drum.

No. 2 cylinder lens corrects deflection of laser beams due to varia- tions in the duplex scanning mirror installing angle, and leads the stable laser beams for each line to the photoconductor drum.

Part name	Function
Laser diode	The laser power is controlled by the
	APC (Auto Power Control) circuit. In
	addition, the paper empty sensor is
	provided.
	The laser diode radiates 780nm infrared
	semiconductor laser beams under
	control of the laser control PWB.
Collimator lens	The collimator lens arranges laser
	beams radiated from the laser diode to
	be parallel beams and converges them
	on the photoconductor drum.
No. 1 cylindrical lens	Adjusts the direction of the laser beams.
Scanning motor/	Used to rotate the scanning mirror.
Scanning mirror	Started by the drive signal (PMD_) from
	the PCU. The RPM is controlled by the
	clock signal (PMCLK_). The motor RPM
	is 11811 RPM.
	The scanning mirror is a6-surface
	mirror, and it reflects laser beams. By
	this operation, 6 lines of printing is made
	for one rotation of the scanning motor.
No. 1 mirror	This mirror reflects laser beams to the
	curved mirror.
Laser beam sensor	Used to detect laser beams to make
PWB (Start position	horizontal synchronization.
detection PWB)	The photo sensor on the PWB detects
	laser beams to generate SYNC signal.
No. 2 mirror (Curved	Laser beams are scanned by the
mirror)	scanning mirror. But the dot interval of
	laser beams radiated onto the
	photoconductor differs at the center and
	at the corners. This mirror corrects this
	difference to provide even dot interval of
	laser beams. For this reason, it is of
	curved structure.
No. 3 mirror	This mirror passes the laser beams
	reflected from the curved mirror to the
	photoconductor mirror.
No. 2 cylindrical lens	This lens is used to correct laser beam
	deflection due to variations in the
	scanning mirror angle.

D. Image process section

(1) Outline

This section is composed of the photoconductor section, the develop- ing section, the transfer/separation section. Images formed by laser beams formed by the scanner (Writing) section are converted into a latent electrostatic images, which are formed into visible images by toner development. The toner images are transferred onto paper.

1 – 14