Subsurface damage in precision ground ULE(R) and Zerodur(R) surfaces.

Area of Science:

• Materials Science
• Optical Engineering
• Manufacturing Processes

Background:

• Large optics made of ULE (Ultra Low Expansion) and Zerodur are critical components in various advanced applications.
• Achieving high precision and minimizing defects during the manufacturing of these optics is essential for performance.
• Current grinding processes can be time-consuming and may introduce undesirable surface and subsurface characteristics.

Purpose of the Study:

• To investigate methods for improving the total process cycle time for large ULE and Zerodur optics.
• To compare the subsurface damage in ULE and Zerodur glass after grinding using a specific grinding mode.
• To characterize the grinding response by analyzing surface roughness, surface profile, and subsurface damage.

Main Methods:

• Grinding of ULE and Zerodur optical materials using a selected grinding mode.
• Characterization of the grinding response through measurements of surface roughness.
• Analysis of surface profile and quantification of subsurface damage depth zones.

Main Results:

• The study identified that a precise and rapid grinding process can significantly improve cycle times for ULE and Zerodur optics.
• Subsurface damage was observed and quantified in both ULE and Zerodur materials.
• The observed subsurface damage was found to be separable into two distinct depth zones: 'process' related and 'machine dynamics' related.

Conclusions:

• Optimizing grinding parameters can lead to reduced process cycle times for large optics.
• Understanding the distinct zones of subsurface damage is crucial for controlling and minimizing defects.
• The findings provide insights into enhancing the manufacturing precision of advanced optical materials like ULE and Zerodur.