Phase Measurements (3Dpm) - Waygate Technologies Everest Mentor Visual iQ VideoProbe Operating Manual

3D Phase Measurements (3DPM)
Taking 3D Phase Measurements
As with other measurement types, Phase Measurement accuracy improves as tip-to-target distance is reduced. The 3DPM Range Finder icon can be used
to gauge how close the camera is to a given surface. When the camera is farther from the surface, a single bar is shown. As the tip is moved closer to the
surface, 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. All measurements should be evaluated in the Point Cloud.
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 Blue OTA will give better results if the feature or step is horizontal. A forward
view Black or Orange OTA, or side view Green OTA will give better results if the feature or step is vertical (see image to the right). This is due to the LED
orientations in the tips.
When an application calls for placement of measurement cursors within an area that
does not include measurable image pixels, depicted by red 3D Data Mask, inserting a
Measurement Plane extends an object's surface plane beyond its existing edges (like the
surface of a broken compressor blade or the space between a blade tip and a stationary
rub strip).
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
Step 2 –Initiate the Image Capture sequence as described in the following section.
3D Phase Measurement OTA's include an LED based structured light projection system that allows the MViQ to
produce 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 below). MTD stands
for Maximum Target Distance and is the distance from the 3D Phase Measurement tip to the cursor that is
furthest from the tip. Small measurements, especially Depth or Depth Profile (~0.020" or smaller) types, accuracy
may be improved by placing the camera close to or even touching the surface. Large length measurements
can be accurately made with larger MTDs. Recommended OTA is Green 3DMP. The viewing perspective and
surface finish both significantly influence the level of noise in the 3D data and therefore the accuracy. The Point
Cloud feature should be used to verify that the level of noise present is small relative to the size of the indication
being measured.
Appendix E for verification procedures.
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