Meaning
Instantaneous shifts in the oscillation cycle of light waves as they bounce off a surface identify this optical phenomenon. Accurate measurements of phase change on reflection are necessary when using interferometry to inspect moulded lenses or mirrors. If the part and the reference standard have different optical properties, the reported height can be off by several nanometres.
Calculation errors occur when operators fail to account for the refractive index of the plastic versus the metal master.
Height Accuracy
Correction for this phase shift ensures that the virtual surface measured by light matches the physical surface of the tool. Miscalculating the change leads to incorrect assessments of mould surface roughness. Fine-tuning the software eliminates this phantom height from the data.
Metrology Limit
Metallic coatings on plastic reflectors create high phase changes compared to transparent surfaces. Variations in coating thickness cause localised shifts that look like physical defects in the topography. Stable measurements require a deep understanding of how light interacts with specific resin chemistries.
Analytical Result
Calibration against known materials helps to null out the systemic offset caused by the shift. Ensuring the instrument is calibrated for the specific sample material prevents systematic measurement errors. Proper compensation maintains the reliability of the quality report.
