8.8 Object Tool
8.8.1 Object Tool: Input Parameters
Use the Input parameters to configure how the tool analyzes an image.
Figure 201. Object Tool—Input Parameters
ROI
The Region of Interest (ROI) is the user-defined group of pixels in the image that the sensor analyzes.
Figure 202. ROI Parameters
The ROI is a line of pixels that can be shortened, lengthened, or widened as needed for the inspection. Tool analysis follows the direction of the arrow. Set the width and the sample rate for the region of interest. The ROI automatically displays on the Image pane when a tool is added.
ROI Width
The ROI width increases in increments of 4 pixels (for example, 1, 5, 9, 13, ...) up to the total FOV size.
Note that:
• Narrow ROIs execute faster but could miss the edge
• Wide ROIs are more consistent but don't execute as fast
• A wide ROI provides an average value/location, which results in improved repeatability
• The ROI must be 13 pixels or wider to calculate the rotation of a part (Locate tool only) Sample Rate
The sample rate sets the number of samples per pixels (one sample per pixel, two samples per pixel, etc.). The sample rate determines the sub-pixel resolution, which increases the resolution of the tool, and increases the inspection time.
Figure 203. 1 px Wide ROI Figure 204. 13 px Wide ROI
Threshold
The Threshold parameter marks the grayscale transition point.
The tool marks the edge where the pixel intensity crosses the threshold level. From the Threshold Type list, select one of the following:
• Absolute
• Relative (default)
• Edge Strength
Threshold Type: Relative
Finds an edge at a relative pixel intensity. This is the default threshold setting.
Figure 205. Relative Threshold Parameters
The brightest grayscale level found along the ROI is 100% and the darkest is 0%. While Relative threshold is more tolerant of light fluctuations between inspections than other transition types, it may find false edges.
Relative Threshold: Percent
Choose the percentage value at which the edge should be marked.
Object Type
Select the type of object the inspection is looking for.
• Bright—Finds objects brighter than the threshold value
• Dark—Finds objects darker than the threshold value
• Bright or Dark—Finds any object Relative Threshold: Edge Profile Graph
Figure 206. Relative Threshold—Edge Profile Graph
For relative threshold, the x axis is the length of the ROI. The y axis is the pixel intensity along the ROI, with 0% as the darkest pixel in the ROI and 100% as the lightest pixel in the ROI. The light blue line shows the percentage pixel intensity relative to the horizontal gray threshold line. The threshold line moves up or down with the percent value.
NOTE: Because the pixel intensity is relative to what is seen in the ROI, this does not necessarily mean that 0% = pure black or that 100% = pure white.
Point to a location on the graph—the corresponding location is the yellow line on the tool ROI displayed on the image.
Threshold Type: Absolute
Finds an edge at a specific grayscale level.
Figure 207. Absolute Threshold Parameters
While Absolute threshold is less likely to find a false edge than Relative threshold, it may miss edges if the light level changes between inspections.
Absolute Threshold: Value
Enter a specific grayscale value from 0 to 255.
Object Type
Select the type of object the inspection is looking for.
• Bright—Finds objects brighter than the threshold value
• Dark—Finds objects darker than the threshold value
• Bright or Dark—Finds any object Absolute Threshold: Edge Profile Graph
Figure 208. Absolute Threshold—Edge Profile Graph
For absolute threshold, the x axis is the length of the ROI. The y axis is the actual grayscale value from 0 to 255. The light blue line shows the absolute pixel intensity. The horizontal gray threshold line moves up or down with the threshold value.
Point to a location on the graph—the corresponding location is the yellow line on the tool ROI displayed on the image.
Threshold Type: Edge Strength
Measures the rate of change of grayscale values and needs sharply-defined transitions to find edges.
Figure 209. Edge Strength Threshold Parameters
Edge strength ignores gradual changes in light levels across the tool better than other threshold types and it filters out weak or gradual edges.
Edge Strength Threshold: Edge Strength Enter an edge strength value from 1 to 255.
Edges are selected by the edge strength method, which measures the rate of change from bright to dark or dark to bright.
Enter an edge strength threshold in the range from 1 to 255. The default value is 20. As this value is reduced, the tool finds weak, blurry, or more gradual edges.
Object Type
Select the type of object the inspection is looking for.
• Bright—Finds objects brighter than the threshold value
• Dark—Finds objects darker than the threshold value
• Bright or Dark—Finds any object
Edge Strength Threshold: Edge Profile Graph
Figure 210. Edge Strength Threshold—Edge Profile Graph
For edge strength threshold, the x axis is the length of the ROI. The y axis has two measurements. The first is the light blue axis. It represents Edge Strength, a measure of the rate of change of pixel grayscale values. The second is the dark gray axis. It represents Edge Profile, which gives the absolute grayscale level across the tool ROI. The blue line is the rate of change of the grayscale value along the ROI. The two horizontal gray lines are the edge strength threshold plus and minus.
Point to a location on the graph—the corresponding location is the yellow line on the tool ROI displayed on the image.
Filters
Set filters for tool analysis.
Figure 211. Object Tool Filters Smoothing
Runs a rolling average along the ROI length. It filters out sharp changes in the edge profile.
Object Width
Filters out objects and spaces that are smaller than the minimum and larger than the maximum values specified.
Enable End Objects
When enabled, pixels that touch the ends of the ROI are ignored. This may ingnore one or more objects.
Edge Profile
The Edge Profile graph changes depending on which threshold type is selected. Refer to the Threshold section and the specific threshold types for details on the Edge Profile graph.
Image Overlays
Chose whether to display or hide the annotations or the ROI when this tool is not selected.
Figure 212. Image Overlays—Default
These options override the ROI view buttons on the Image Pane Parameters when no tool is selected. When a specific tool is selected, the ROI information is shown.
Hide Annotations
Hides the annotations on the live image for the tool, even when the tool is selected.
Figure 213. Show Object Tool Annotations Figure 214. Hide Object Tool Annotations
Hide ROI
Hides the ROI when the tool is not selected.
Tool Histogram
The Tool Histogram graphically displays pixel intensity information within the current ROI.
Figure 215. Example Histogram
Select the Tool Histogram checkbox to enable the histogram. The default is enabled. Expand the Tool Histogram parameter to view the histogram.
The histogram is a display of the grayscale values on the x axis and the number of pixels on the y axis. The histogram displays the amount of pixels for each grayscale value. The graph displays information for all grayscale values (0 to 255).
Move the pointer anywhere over the histogram to view specific information. The information updates as the position of the pointer changes.
Inspection Pass/Fail
Select the Contribute to Inspection Pass/Fail check box (default) if the tool will influence the Pass/Fail status of the inspection.
Figure 216. Inspection Pass/Fail The Pass/Fail contribution influences the following:
• Discrete output Pass
• Discrete output Fail
• Pass/Fail results counter
• Pass (Green) and Fail (red) LEDs on the Sensor
Select this checkbox if the overall Pass/Fail status of the inspection is dependent on the current tool.