Grazing incidence interferometry: the use of the Linnik interferometer for testing image-forming reflection systems

Area of Science:

• Optical Engineering
• Metrology
• Wavefront Analysis

Background:

• Accurate characterization of optical systems is essential for performance.
• Traditional methods may not be suitable for all wavelengths or configurations.
• Grazing incidence optics require specialized testing methods.

Purpose of the Study:

• To present a simple interferometric method for quantitative wavefront aberration measurement.
• To demonstrate its application in testing and aligning grazing incidence reflection optics.
• To adapt the method for short-wavelength (UV, soft X-ray) applications.

Main Methods:

• Utilizes an interferometric approach comparing the system's wavefront to a true spherical reference wave.
• Displays wavefront differences as a fringe pattern superimposed on the exit pupil image.
• Builds upon the principle described by W. P. Linnik (1933).

Main Results:

• The method quantitatively displays wavefront aberrations.
• Successful demonstration of testing and alignment for grazing incidence optics.
• Identified a variation suitable for ultraviolet and soft X-ray wavelengths.

Conclusions:

• The described interferometric method offers a versatile tool for optical system testing.
• It provides quantitative wavefront aberration data crucial for system optimization.
• The adapted design extends applicability to extreme ultraviolet and soft X-ray regimes.