Sharp FACSIMILE FO-4500 Service Manual page 59

3-4. Loading the documents
1) Make sure that the documents are of suitable size and thickness,
and free from creases, folds, curls, wet glue, Wet ink, clips, sta-
ples and pins.
2) Place documents face down in the hopper.
i) Adjust the document guides to the document width.
ii) Align the top edge of documents and gently place them into
the hopper. The first page under the stack will be taken up by
the feed roller to get ready for transmission.
NOTES: 1) Curled edge of documents, if any, must be straighten
out.
2) Do not load the documents of different sizes and/or
thicknesses together.
3-5. Documents requiring use of document carrier
1) Documents smaller than B6 (128mm x 182mm).
2) Documents thinner than the thickness of 0.06mm.
3) Documents containing creases, folds, or curls, especially those
whose surface is curled (maximum allowable curl is 5mm).
4) Documents containing tears.
5) Carbon-backed documents. (Insert a white sheet of paper be-
tween the carbon back and the document carrier to avoid transfer
of carbon to the carrier.)
6) Documents containing an easily separable writing material (e.g.,
those written with a lead pencil).
7) Transparent documents.
8) Folded or glued documents.
Document in document carrier should be inserted manually into
the feeder.
4. Optical system
(1) General view
Reading line
Transfer roller (2)
Document
LED
Mirror1
(2) Composition
The optical system is composed of the document feed mechanism,
the lamp, the reflecting mirrors, the focusing lens, the CCD sensor,
and the read process circuit.
4-1. LED Lamp
The LED lamp is used to expose the document.
Mirror 2
Transfer roller (1)
Lens
CCD
Fig. 4
4-2. Lens
The lens is used to focus the light reflected from the document on the
CCD elements.
4-3. CCD
The CCD (charge coupled device) image sensor consists of a pho-
todiode array which converts the intensity of light reflected from the
document surface into series of analog voltages which are then
stored in an analog shift register. The series of analog voltages are
then converted into a digital equivalent by a black/white binary logic
circuit.
(Example) Scan signal output waveform
100%
40%
minimum
Maximum document width, 256mm
1) The minimum output from the CCD at the maximum scan width of
document (256mm) must be more than 40% of the peak value.
2) The peak output must be about 200mV under room temperature
to avoid CCD saturation.
3 – 2
FO-4500H
Mark
Fig. 5
Peak
Scan line
length
Fig. 6