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24
Chapter 3
3.2
Laser Module Theory of Operation
Figure 14 shows the functionality of the Laser Module. The following sections detail
the theory of operation for each of the blocks in Figure 14.
The circuit block diagrams for each laser mode of operation are shown in Figure 15,
Figure 16, and Figure 17. The theory of operation for each mode of operation is
discussed in Sections 3.2.9 - 3.2.11.
To
icroprocessor
Modulation
Input Port
-
+
Photodiode
3.2.1
Laser Interface
The laser interface provides optically isolated serial communications between the
laser board and the microprocessor. Control signals are passed to the laser board to
set the laser board status, current limit, current set points, and photodiode feedback
functions. Instructions and data are sent over the serial interface to the optical
barrier. Status and data are serially passed back to the microprocessor.
Limit DAC
A/D Converter
Optically
Isolated
Serial
Bus
Fault Monitors
Output On/Off
Slow Turn-On
Set Point
DAC
Figure 14 - Laser Module Block Diagram
Principles of Operation
and
Voltage
Sensing
Current
Feedback
Unregulated DC
Voltage
Regulator
Pass
Transistor
Output
Output
Shorting
Current
Sensing
Laser
Diode
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