X925 Adf Scanner Theory Of Operation - Lexmark C925 Product Study Manual

Lexmark C925/X925 Color Product Study Guide

X925 ADF Scanner Theory of Operation

The X925 duplex ADF enables the user to create duplex scans automatically, eliminating the need to flip
the media over in order to duplicate it. The ADF uses a step motor and a series of sensors to determine
the media's position in the paper path during the scan process.
The following steps are performed in creating a scan on the X925 ADF:
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The paper is placed on the flatbed or the ADF paper tray and a scan or copy command is
initiated by the user from a computer or on the scanner itself.
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Once the scan command is initiated, the ICC board on the scanner polls the paper present
sensor in the ADF to see if paper is present.
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If paper is present, the size sensors are polled to determine the length and width of the
paper. There are two paper length sensors found on the ADF input tray.
These sensors detect A4 vs. folio for non-US users, and letter vs. legal for US users.
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The ADF paper width sensor consists of three photo interrupt sensors that are actuated
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by the paper guides on the ADF tray. The position of the guides detect A4, B5, and A5
widths for non US users and statement, executive, and letter widths for US users.
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After the size of the paper determined by the width and length sensors, the cover open
sensor is polled to ensure the ADF top cover is properly closed.
If the cover is not closed, an error posts on the machine.
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If the cover is closed, the pickup sensor is polled.
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The pickup sensor determines if the pick roll is in the up or down position.
If the pick roll is in the up position, it is moved to the down position.
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If the pick roll is already in the down position, the ADF relay card signals the start of the
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pick process.
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The top sheet of paper is pulled into the ADF towards the feed roll.
•
To prevent double feeds, a separator roll provides resistance to hold other sheets in the
paper input tray.
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Once the top sheet passes the feed roll, it moves into the ADF paper path and triggers the
gap sensor actuator. At this point, the paper has a certain amount of time to pass over it
(based on the paper length) otherwise a jam error posts.
•
After passing the gap sensor, the paper reaches the paper in sensor. This is a reflective
sensor that determines the position of the paper in the paper path and activates the actual
scan image process.
•
As the paper advances to the scan area, it actuates the ADF Scan Sensor.
The ADF motor generates pulses which are stored in an on-board counter.
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This counter, along with the ADF scan sensor, ensure that the media travels at the
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correct speed through the scan area (determined by the image DPI specified by the
user).
After a predetermined number of counts, the media reaches the scan area and the image
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acquisition process is initiated.
•
While the image acquisition process is executing, the ADF scan sensor is polled to determine
if the trailing edge of the media has reached the sensor.
For Training Purposes Only 28
Rev 2.3
6/21/2011