Edge PresencePlus P4, User Manual

Page: 89 / 182

01/05
P/N 120413
81
User’s Manual Object Tool Setup
Banner Engineering Corp. • Minneapolis, MN USA
www.bannerengineering.com • Tel: 763.544.3164
-------------------------------------------------------------------------------------
Threshold Example
The following image shows an Object tool, scanning three bars from left to right.
Transition Type (default: Relative)
The drop-down list of Object tool transition types includes the following
choices:
Relative Threshold
-
Finds an edge at a relative pixel intensity.
- Is more tolerant of light fluctuations between inspections than other
transition types.
- May find false edges.
Absolute Threshold
-
Finds an edge at a specific gray scale level.
- Is less likely to find a false edge than other transition types.
- May miss edges if the light level changes between inspections.
Edge Strength Threshold
-
Detects edges on surfaces that are not uniformly illuminated.
- Finds edges in low-contrast images.
- Is more tolerant of gradual changes in light levels across the tool than
other transition types.
- Filters out weak or gradual edges.
Object Polarity (default: Bright or Dark)
-
Choose Bright or Dark to find all objects.
- Choose Bright to find objects that are brighter than the background.
- Choose Dark to find objects that are darker than the background.
See
Object Polarity
on page 85 for an inspection example.
Threshold Percent (default: 50)
Threshold Value (default: 128)
Threshold Edge Strength (default: 20)
This option sets the threshold value (moves the dotted green line on the
Edge Profile graphs).
- Percent is displayed when the Transition Type is Relative Threshold.
- Value is displayed when the Transition Type is Absolute Threshold.
- Edge Strength is displayed when the Transition Type is Edge Strength.