Optical System - Sharp Z-87 Service Manual

[8] OPTICAL SYSTEM

A. Original alignment
The original must be set in alignment to the front left corner of the
original table. An image loss appears in the shadowed area because
of paper separation.
Original lead edge guide
Original set alignment
B. Void area and image loss
1 Void area
Make a copy with the original cover left open. The area of the
paper copied white is the void area.
2 Image loss
Indicates the area of image lost on the copy.
Lens Copy lamp
Reducing Enlarging
direction direction
Table glass
(Front frame side)
– 20 –
1. General description
•
As a fixed focus lens is used in the optical unit, magnification ratio
can be varied by changing the lens position and the optical path
distance by moving the positions of the mirror-4 and mirror-5.
There are choices of four magnification ratios which can be at-
tained by selecting the magnification ratio; enlargement (x1.24),
normal (x1.00) and reduction (x0.95, x0.75).
•
Exposure is controlled by varying the copy lamp drive voltage. An
automatic exposure sensor (photo-diode) is adopted in the optical
system. Contrast of the original is determined by the automatic
exposure sensor which receives the copy lamp light reflected from
the original and the copy lamp intensity is controlled according to
the contrast of the original thus detected.
Original cover
3 Void area and image loss limits
Lead edge
Void area
Lead edge
Image loss
(Original)
Copy
Side image loss
3mm~10mm
Lead edge image loss, 1.0~5.5mm
No.2/3 mirror unit
0mm
Side 9 mm, max.
1 ∼ 7.0 mm
3 ∼ 10 mm
Side
Original
Void area,
9mm,max.