Surface topography measurement by frequency sweeping digital holography.

Area of Science:

• Metrology
• Optical Engineering
• Materials Science

Background:

• High-precision surface topography measurement is crucial for industries like opto-mechanics and deformation analysis.
• Coordinate measuring machines (CMMs) are standard but suffer from low point density, long measurement times, and potential surface damage.
• Existing methods struggle with complex geometries and require extensive measurement durations.

Purpose of the Study:

• To introduce and detail a novel method for high-precision surface topography measurement.
• To present frequency sweeping digital holography (FSDH) as an advancement over traditional techniques.
• To demonstrate FSDH's capability for complex object characterization.

Main Methods:

• Developed a frequency sweeping digital holography (FSDH) technique based on wavelength scanning interferometry.
• Designed a relatively simple optical setup for data acquisition.
• Focused on motionless data capture to improve efficiency and reduce risk of damage.

Main Results:

• Achieved high axial accuracy of 10 μm for surface topography measurements.
• Enabled measurement of objects with diameters up to several hundred millimeters.
• Demonstrated suitability for complex geometries and materials like metals, plastics, and composite structures.

Conclusions:

• FSDH provides a significant improvement for surface topography measurements, especially for complex objects.
• The motionless, high-accuracy nature of FSDH makes it ideal for advanced material characterization, including acoustic metamaterials.
• This method offers a practical and efficient alternative to CMMs for demanding metrology applications.