Chromatic confocal sensor-based on-machine measurement for microstructured optical surfaces featuring a self-aligned...

Area of Science:

• Metrology and Measurement Science
• Optical Engineering
• Manufacturing Technology

Background:

• Ultra-precision machining requires accurate form error identification and compensation.
• On-machine measurement using chromatic confocal sensors is effective but faces challenges with alignment.
• Traditional spiral scanning methods for sensors are tedious and require precise alignment.

Purpose of the Study:

• To develop an on-machine measurement system for ultra-precision diamond turning machines.
• To propose a self-alignment method for chromatic confocal sensors, eliminating the need for tedious spiral center alignment.
• To enhance the efficiency and flexibility of measuring microstructured optical surfaces.

Main Methods:

• Development of an on-machine measurement system with a uniform spiral scanning motion for the sensor probe.
• Implementation of a self-alignment method to identify optical axis deviation by matching measured and designed surface points.
• Validation through numerical simulation considering noise and system dynamics, followed by practical application and off-machine verification.

Main Results:

• The proposed self-alignment method successfully identified optical axis deviation without additional equipment.
• On-machine measured points were reconstructed after calibrating alignment deviation for a microstructured surface.
• Practical measurements were verified by off-machine white light interferometry, confirming the method's accuracy.

Conclusions:

• The developed self-alignment method significantly simplifies the on-machine measurement process for ultra-precision components.
• Eliminating tedious operations and special artefacts improves measurement efficiency and flexibility.
• This approach is highly beneficial for generating and verifying microstructured optical surfaces.