Teledyne LeCroy AORM - Advanced Optical Recording Measurements - Manual (Page 33)

AORM Software Package
923133 Rev A ISSUED: June 2013
31
Pit or Space Identification
This is determined uniquely by the threshold, hysteresis, and edge polarity of threshold crossings.
A positive threshold crossing indicates the start of a positive polarity pit and the end of a negative
polarity space. A positive threshold crossing followed by a negative threshold crossing fully
delineates a pit. A negative crossing followed by a positive crossing fully delineates a space, as
illustrated in the following figure.
In order to prevent false pit and space identifications, hysteresis is provided. Hysteresis adds an
additional condition that must be met before a threshold crossing is recognized as a pit/space
edge. It requires that the waveform make an excursion of a certain distance from the threshold
before the next threshold crossing is recognized.
The next figure shows a threshold crossing that would result in incorrect pit identification without
hysteresis.
Voltage
Threshold
Space Pit
False
Pit
Level
Threshold