Scanning and image capture system
The flatbed image scanner captures an electronic image of the document on the glass. The scanner does this
by illuminating the document with LEDs (red, green, and blue) and capturing the image in the image sensor to
create an electronic format of the document. The flatbed scanner consists of three main elements.
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CIS scanner
The CIS (contact image sensor) scanner captures an image using the product's optical path. Red, green,
and blue LEDs sequentially illuminate a small strip of the document (often called a raster line), and the
optical system captures each color in a single row of CCD sensors that cover the entire page width.
Because only one color is captured for each line per exposure, the three colors are recombined
electronically to create the full color image. For monochromatic scans or copies, all three LEDs are
illuminated to create a white light for the scan so the raster line can be captured in one exposure.
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Mechanical drive system
The drive system moves the CIS scanner along the document length to create the image. In this product,
the drive system consists of a small DC motor with an optical encoder, a drive belt, and a guide rod. The
speed of the drive system is proportional to the scan resolution (300 ppi is much faster than 1200 ppi)
and also proportional to the type of scan (color scans are slower than monochromatic scans).
The carriage drive moves the CIS scan head along the document length to create the image. In this
product, a small DC motor with an optical encoder creates this motion. The speed of the carriage drive is
proportional to the scan resolution (300 ppi is much faster than 600 ppi) and also proportional to the
type of scan (color scans are three-times slower than monochromatic scans).
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Image processing system (formatter)
The formatter processes the scanner data into either a copy or a scan to the computer. For copies, the
image data is sent directly to the product without being transmitted to the computer. Depending on
user selections for the copy settings, the formatter enhances the scanner data significantly before
sending it to the product. Image data is captured at 300 ppi for copies and is user selectable for scans to
the computer. Each pixel is represented by 8 bits for each of the three colors (256 levels for each color),
for a total of 24 bits per pixel (24-bit color).
Scanner power-on sequence of events
When the product is turned on, it performs the following tests:
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Motor test. The product moves the motor left and right to confirm operation. It reports a scanner error
12 if no motion is detected in the motor encoder system.
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Wall find. The scan carriage moves slowly to the left while watching an encoder on the carriage motor
to determine when the carriage has found the side wall or stop. This enables the product to identify the
document origin (position of the original). If the document origin cannot be located, a default position is
used instead.
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LED check. The product moves the carriage to the white calibration label under the left side of the
flatbed image scanner, and it verifies that the minimum and maximum response is acceptable. It
reports a scanner error 14 if the response is unacceptable.
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Home find. The scan carriage uses the optical scanner to find physical reference features that relate to
the document origin at the left side of the image glass. This process ensures accurate location of the
ENWW Scanning and image capture system 27
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