Teledyne LeCroy AORM - Advanced Optical Recording Measurements - Manual (Page 34)

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ISSUED: June 2013 923133 Rev A
The hysteresis band shown in the next figure is centered on the user- selected voltage level
threshold.
The hysteresis band divides the display into three zones. The ORM Package uses both the
voltage threshold and hysteresis settings to identify pits and spaces.
Criteria for identifying a “feature” (pit or space):
• The first feature identified after the left parameter cursor can be either a pit or space. If
the signal first enters Zone 1, the first feature identified (if additional constants are met)
will be a pit. If the signal first enters Zone 3, it will be a space.
• After first crossing into Zone 1 or Zone 3, the next time the signal crosses the voltage
threshold, it is recorded as the start time of a feature.
• If the first feature to be identified is a pit (signal entered Zone 1 first), after crossing the
voltage threshold the signal must cross into Zone 3 and then pass the voltage threshold
again to complete all conditions for identification as a pit. The first time that the signal
crosses the voltage threshold after entering Zone 3 is recorded as the end time of the pit
and the start time of the following space. The time between the start and end of the pit is
recorded as the pit width. If the first feature to be identified is a space, the signal first
entered Zone 3. The algorithm is used with directions reversed.
Zone 1
Zone 2
Zone 3
Voltage
Threshold
Pit Width
First feature
will be a pit
Start of pit
Pit meets condition of
crossing into Zone 3
End of pit. Start
of space Pit fully
identified
Space meets condition
of crossing into Zone 1
End of space.
Space fully
identified