Image Scanning - Ricoh FAX3700l Service Manual

August 2nd, 1995 DETAILED SECTION DESCRIPTIONS
SCANNER

4. Image Scanning *

[G]
[A]
[B]
[F]
[C]
[D]
[E]
H516D544.wmf
The scanner consists of a shading plate [A] and a contact image sensor
(CIS) assembly [B]. Inside the CIS are an exposure glass [C], a rod lens ar-
ray [D], an image sensor [E], and an LED array [F].
The image sensor consists of a row of 2048 photosensitive elements (B4
width x 8 dots/mm). Light from the LED array is reflected from the document
and focused onto the image sensor by the rod lens array. Because of the
short optical path inside the CIS, the focal depth is much shorter than for a
CCD type scanner. Because of this, the spring [G] pushes the shading plate
[A] so that the document surface always touches the exposure glass at the
scan line.
The image sensor assembly is adjusted at the factory, so it does not need
any adjustment at replacement in the field.
The image sensor scans the original one line at a time, and outputs an ana-
log signal for each line. The voltage from each element depends on the
intensity of the light reflected from the original onto the element; the intensity
of the light depends on the darkness of the area of the document it was re-
flected from.
2-3