Canon BJC-55 Series, Service Bulletin

Page: 158 / 249

8) Scanner controller
The scanner controller is an IC that controls the BASIS and processes the analog
signal output from the BASIS. The scanner controller also controls the following
image processing:
• Black level Correction
The black level is set to maximum BASIS output.
• A/D Converter
The A/D converter converts the image signals to 10 bits image data.
• Shading Correction
The variation of the image signal is corrected by the shading correction. Due to (i)
the variation of the sensivities of the BASIS sensor elements and (ii) the uneven
distribution of light transmitted through the center and the periphery of the lenses,
the intensity of each scanned line is not uniform. The scanned data is compared
against a standard white data to even out and correct the density.
• Carriage Scanning Direction Resolution Converter
The carriage scanning direction resolution converter converts the resolution of the
output in the scanning direction according to the carriage direction.
• Edge emphasis
• Binary image processing function
The scanner controller has a built-in SRAM used for output buffer memory.
Scanner cartridge cannot be disassembled, reassembled.
As the imaging lens is used for forming an image on the BASIS, it is moved
from its fixed position to adjust the optical path for focusing. Focusing
cannot be conducted during servicing.
Part 4: Technical Reference
BJC-50
4-48