Polaroid SprintScan SS35, Руководство по ремонту

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Slide Scanner Repair Manual Functional Description
43
Associated Analog Signal Processing Support Circuitry
The CCD image sensor is clocked out on a line-by-line basis. Global timing signals (line
sync, color sync, and color order) are controlled by the microcontroller on the main controller
PC board. CCD image sensor clocks and other timing signals are generated by an on-board
state machine and are derived from these input control signals. The on-board state machine
clocks a number of Imager Driver Chips (IDC's), which perform level shifting and provide
sufficient drive to clock the CCD image sensor. The on-board state machine clocks and
timing are generated by the XILINX Chip on the main controller PC board. Limited circuitry
on the CCD sensor PC board de-muxes the signals.
Other timing signals control the analog signal processing, dark reference pixel sampling, and
the analog-to-digital (A/D) converter. Scanning parameters (global dark levels, individual
dark levels, and individual gain adjustments) are also controlled by input data following the
scanner calibration.
The output of the CCD is buffered and multiplexed into the Video Signal Processor (VSP) on
the main controller PC board.
Main Controller PC Board
The main controller PC board consists of a video signal processor (VSP), an analog-to-digital
(A/D) converter, a primary correction ASIC, DRAM based buffer memory, a secondary color
correction ASIC, a microcontroller, a SCSI interface, and its support electronic circuitry. Refer to
simplified block diagram (Figures 2-5 and 2-6) and the main controller PC board schematics in
Section 6 of this Repair Manual when reading the description of the main controller PC board.
The main controller PC board provides the following:
• Analog Signal Processing
• Digital Signal Processing
• Scanner Control
• System Interface
Digital image data (10-bit for SS35/SS35 ES, 12-bit for SS35 PLUS) is provided from the CCD
board at 2 MHz, one color line at a time. The microcontroller performs system memory test
followed by an automatic self calibration on system power-up. Dark uniformity correction
factors are derived by imaging a fixed dark uniformity target (carriage and shutter act as the
uniformity target for the SS35 PLUS).
Multiple lines of data are acquired and stored unprocessed in the main controller PC board’s
DRAM. The data is read and analyzed by the microcontroller which derives correction factors
and writes them into the correction factor SRAM. The same operation is repeated on a white
uniformity target to derive gain uniformity factors. All other digital signal processing parameters
are derived from stored defaults or are down loaded from the host computer, and applied to the
image data in real time while scanning. Processed data and scan status are returned to the
host computer via the SCSI interface.