Fizeau digital interferometry with a diffraction-generated spherical wave for testing focusing optics

Area of Science:

• Optical metrology
• Interferometry
• Diffraction physics

Background:

• Fizeau digital interferometry typically uses a spherical autostigmatizing mirror for testing focusing optics.
• Existing methods may have limitations in precision or complexity for certain optical tests.

Purpose of the Study:

• To introduce and validate a new method for testing focusing optics using a small, reflective spherical particle.
• To demonstrate the particle's function as a secondary coherent point source generating a spherical wave via diffraction.

Main Methods:

• Replacing the traditional spherical autostigmatizing mirror with a small, reflective spherical particle placed at the test lens's focus.
• Utilizing the diffraction pattern generated by the particle to create the test beam in a Fizeau interferometer.
• Analyzing the relationship between the diffraction-generated wave and the particle's size and shape.

Main Results:

• The small particle successfully acts as a coherent point source, producing a spherical wave through diffraction.
• The study establishes guidelines for selecting appropriate diffracting elements (particles) based on wave characteristics.
• Experimental validation confirms the high accuracy of this particle-based interferometry technique.

Conclusions:

• A small, reflective spherical particle is a viable and accurate replacement for the spherical autostigmatizing mirror in Fizeau digital interferometry.
• This diffraction-based approach offers a precise method for testing focusing optics.
• The technique's accuracy is experimentally verified, highlighting its potential in optical metrology.