Meaning
Signal losses in non-contact metrology occur when a sensor fails to receive a return reflection from the measured surface. These optical dropouts appear as holes or missing data points in a three dimensional scan. They are common when measuring highly transparent polymers or dark surfaces that absorb the light source.
The measurement software usually marks these areas as null values that must be interpolated or rescanned.
Measurement Artifact
Surface geometry influences the likelihood of losing the signal. Occurrences of optical dropouts on a moulded part happen when steep angles reflect the light away from the sensor aperture. This creates a shadow effect where no data can be captured.
Surface Steepness
Light rays striking a vertical wall do not bounce back to the detector. Frequency of optical dropouts is reduced by adjusting the orientation of the part to bring these steep features into a measurable range. Coaxial lighting can also help in capturing reflections from deeper cavities.
Data Integrity
Voids in the point cloud reduce the accuracy of the surface roughness calculation. High rates of optical dropouts make it difficult to verify if a part meets the required tolerance. Improving the sensor sensitivity or using a different wavelength can reduce the frequency of these errors.
