Brother DCP375CW Service Manual page 92

(1) ADF scanning: Document moves across stationary CIS unit (Only for models with
ADF)
Placing a document face down in the ADF activates the document front sensor, switching to
ADF scanning.
The CIS drive mechanism (details below) operates for each scanning command executed. First,
the CIS motor moves the CIS unit to the white reference film for white level compensation.
Secondly, the ADF motor rotates the document pull-in roller* to pull the document into the
ADF. (*This roller is used in this series of machines in order to pull in documents horizontally
placed.) Thirdly, the CIS motor again moves the CIS unit to the ADF scanning position.
The document separation roller feeds the pages one at a time, starting from the bottom, to the
document feed rollers (1 and 2), which rotate to move the page in a curve left, up, and right. The
page is scanned as it passes over the CIS unit. It then leaves the machine face up onto the
ejected document support section of the document guides. The machine ejects subsequent pages
under this one to preserve the document page order.
(2) Flat-bed scanning: CIS unit moves under stationary document
The user lifts the document cover, places a page (or open book) face down on the glass plate,
and closes the document cover.
The CIS drive mechanism (details below) operates for each scanning command executed. The
CIS unit first moves to the white reference film for white level compensation. It then moves
right, scanning as it goes. It returns to its home position after the scan.
CIS drive mechanism
The contact image sensor (CIS) unit rides along the CIS rail, driven by the CIS drive belt.
Clockwise motion of the CIS motor moves the unit to the right; counterclockwise motion, to the
left.
This unit consists of the document illumination LED array, the lens array gathering the light
reflected from the scanned image, the CIS PCB converting the light input to pixel data output,
and the CIS glass.
The CIS unit used in the machine supports color scanning. In scanning color documents, the
CIS unit illuminates them by turning on the red (R), green (G), and blue (B) LEDs alternately.
In scanning monochrome documents, it turns on the green LEDs only.
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