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DETAILED SECTION DESCRIPTIONS
SCANNER
5. Image Scanning
[A]
The scanner consists of the scanner roller [A] and a contact image sensor
(CIS) assembly [B]. Inside the CIS are an exposure glass, a optical lens ar-
ray, an image sensor, and an LED array.
The image sensor consists of a row of 2048 photosensitive elements (256
mm width x 8 dots/mm). Light from the LED array is reflected from the docu-
ment and focused onto the image sensor by the optical lens array. Because
of the short optical path inside the CIS, the focal depth is much shorter than
for a CCD type scanner. The spring [C] pushes the CIS up, so that the docu-
ment always touches the exposure glass at the scan line.
The white level is stored in the SRAM on the FCU at the factory. The white
level must be adjusted when the ROM or CIS is replaced in the field, after
every time a RAM clear is done.
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.
Cross reference
White level adjustment: Service Table and Procedures (chapter 4), section 4.1.15
[B]
[C]
2-4
August 7th, 1995
H068D004.wmf
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