A novel operating principle in speckle interferometry: the double-focusing

Area of Science:

• Optics and Photonics
• Interferometry
• Optical Metrology

Background:

• Speckle interferometry is a powerful optical technique for measuring small displacements.
• Holographic interferometry offers high sensitivity but often involves complex setups.
• Existing speckle interferometers may require intricate optical configurations.

Purpose of the Study:

• To introduce and detail the operating principle of a new family of speckle interferometers: double-focusing interferometers.
• To highlight the advantages of double-focusing interferometers over existing techniques.
• To demonstrate the versatility in implementing this new interferometer type.

Main Methods:

• Detailed description of the operating principle of double-focusing speckle interferometers.
• Comparison of sensitivity with holographic interferometry.
• Exploration of implementation using Michelson, Mach-Zender, and in-line configurations.

Main Results:

• The double-focusing interferometer is sensitive to displacement components along the bisector of illumination and observation angles.
• No external reference beam is required, simplifying the experimental setup.
• The interferometer functions correctly when only a portion of the illuminated area deforms.

Conclusions:

• Double-focusing speckle interferometers offer a simplified and effective alternative for displacement measurement.
• The technique retains the displacement sensitivity of holographic interferometry with reduced experimental complexity.
• Flexible implementation options make this a versatile tool for various applications.