THEORY GUIDE Optical
10DEC05
TG4825-1
Page
59 of 120
Component Description
DIGITIZER BOARD
A3
Controls the operation of the GALVO BOARD, which moves the laser
beam.
GALVO Includes:
• MOTOR - rotates the SHAFT
• SHAFT - has a MIRROR at one end to send the laser beam
toward the F-THETA LENS
GALVO BOARD A4 Includes a feedback circuit that controls the position of the MIRROR.
The position of the MIRROR determines the position of the laser
beam. The GALVO BOARD uses the following information to define
the desired position of the MIRROR:
• clock signal from the DIGITIZER BOARD, which moves through
the desired position between the offset and amplitude.
• size of the PLATE from the DIGITIZER BOARD, which receives
the information from the BAR CODE LABEL on the CASSETTE
• values for the PLATE size, which were set up during calibration:
– offset - starting point
– amplitude - the distance to move across the SCREEN
Information from POSITION SENSORS determine the position of the
GALVO SHAFT in the scan - the actual position. The actual position
is compared to the desired position and corrections in position are
made to provide a smooth motion of the beam.
The GALVO BOARD also:
• emits “Line Start” signals to the DIGITIZER BOARD to provide the
information that a line is complete and it can start another line
• energizes the LASER DIODE DRIVER BOARD at times
determined by software
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