Phase Measurements (3Dpm) - GE Mentor Visual iQ User Manual

3D Phase Measurements (3DPM)
more bars are illuminated. Large length measurements may be performed with
few bars illuminated, while still achieving good accuracy. In general, the best
accuracy is achieved by getting as close to the surface as possible.
Accuracy is generally best when viewing a surface from approximately a 45°
angle, especially on surfaces that are shiny or have a speckled appearance.
When measuring surfaces with steps or long, deep features, a side view tip will
give better results if the feature or step is horizontal (as shown at right). A front
view tip will give better results if the feature or step is vertical. This is due to the
LED orientations in the tips.
To Capture a 3D Phase Measurement Image:
Step 1 – Attach either a forward view or side view 3D Phase Measurement
optical tip to the probe. Each measurement tip must be factory calibrated to
a particular probe, and may be calibrated to more than one probe. To ensure
measurement accuracy, verify the tip's accuracy each time it is installed. Refer
to Appendix E for verification procedures.
Step 2 – Verify that the Visual iQ system has automatically identified the 3DPM
optical tip. The range finder appears near the upper right corner of the live image.
Step 3 – Initiate the Image Capture sequence as described in the following
section.
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3D Phase Measurement optical tips and probe capture a three-dimensional surface scan of the object. Measurements are
then made directly on the surface and displayed on the image. Preliminary steps of matching cursors or marking shadow
lines are not necessary.
Maximum Target Distance - MTD Number
The 3D Phase Measurement system will display a number on-screen after a measurement is complete. While taking the
measurement, an MTD number will appear (see the upper left corner of the figure to the right). MTD stands for Maximum
Target Distance and is the distance from the 3D Phase Measurement tip to the surface at the point of the active cursor.
Unlike stereo measurements, 3D Phase Measurements do not use Accuracy Index.
Taking 3D Phase Measurements
As with other measurement types, Phase Measurement accuracy improves as tip-to-target distance is reduced. The range
finder bar icon can be used to gauge the suitability of the current tip-to-target distance for a given measurement. When the
surface is too far for measurement, a single bar is shown, and measurement should not be attempted. As the tip is moved
closer to the surface,
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