THEORY GUIDE Optical
10DEC05
TG4825-1
Page
63 of 120
Component Description
DIGITIZER BOARD
A3
Controls the operation of the GALVO BOARD A4 and the PMT/DAS
BOARD A5 to provide for the measurement and collection of image
data at the correct time:
• sends a signal to the GALVO to rotate the MIRROR to move the
laser beam in the fast scan direction across the SCREEN
• sends a signal to the PMT/DAS BOARD A5 to measure the
emitted light at controlled times. Each measurement makes a pixel
in the completed image.
LIGHT COLLECTOR Provides the collection of the blue light emitted from the SCREEN
and sends it toward the PMTs. The inside surface of the
COLLECTOR is reflective.
BLUE FILTER Removes any red laser light reflected from the SCREEN, allowing
only the blue light to reach the PMTs.
PHOTOMULTIPLIER
TUBES (PMT)
2 LIGHT SENSORS, which emit a current signal corresponding to the
light reaching the FACE of the PMT. The PMTs use a high-voltage
POWER SOURCE to operate. The voltage of the POWER SOURCE
determines the sensitivity of the PMTs.
PMT/DAS BOARD
A5
• Changes analog signals from the PMTs to digital format:
– amplifies the signals from the 2 PMTs
– adds the signals from the PMTs
– filters the summed signal
– changes the summed signal to a digital format
• Measures the strength of the laser beam and changes it to digital
format.
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