Near optical coaxial phase measuring deflectometry for measuring structured specular surfaces

Area of Science:

• Optical metrology
• Surface metrology
• Precision engineering

Background:

• Phase measuring deflectometry (PMD) is crucial for specular surface form measurement.
• Conventional stereo-PMD struggles with structured surfaces due to large system volume and measurement shadows caused by non-coaxial optical paths.

Purpose of the Study:

• To introduce a novel near optical coaxial PMD (NCPMD) system.
• To overcome limitations of conventional stereo-PMD for structured specular surfaces.

Main Methods:

• Utilizing a plate beamsplitter to achieve near optical coaxial alignment.
• Developing a portable NCPMD prototype with stereo imaging sensors.
• Comparing NCPMD with conventional PMD using a specular step measurement.

Main Results:

• NCPMD significantly reduces system volume and measurement shadows compared to conventional PMD.
• The proposed configuration allows perpendicular capture of the surface under test, enhancing efficiency.
• Experimental results validate the comparable accuracy and advanced performance of the portable NCPMD prototype.

Conclusions:

• The NCPMD system offers a compact and efficient solution for specular surface form measurement.
• It demonstrates superior performance for portable and embedded applications, especially for discontinuous surfaces.
• The plate beamsplitter approach effectively minimizes measurement errors associated with shadows.