Absolute interferometric test for high numerical-aperture spherical concave surfaces: Gravitational effect. (December 2016)

• Record Type: Journal Article
• Authors: Hibino, Kenichi; Hanayama, Ryohei; Kim, Yangjin
• Is Part Of: Measurement. Volume 94(2016)
• Page Start: 920
• Page End: 926
• Publication Date: 2016-12
• Subjects: Spherical concave test -- Fizeau interferometer -- Phase measurement -- Gravitational deformation -- Phase shift; Weights and measures -- Periodicals; Measurement -- Periodicals; Measurement; Weights and measures; Periodicals; 530.8
• DOI: 10.1016/j.measurement.2016.03.067
• Languages: English
• ISSNs: 0263-2241

Abstract

Highlights: We examine the optical aberrations that are generated in spherical concave surfaces. We utilize a two-surface comparison to quantify the gravitational deformation. Certain aberrations vary with rotation around the optical axis. We separate and subtract away the aberrations caused by gravitational deformation. Abstract: Spherical concave surfaces with high numerical apertures are required in industry for lithography optics at ultraviolet and X-ray wavelengths. Among the systematic errors in these spherical-surface test, the gravitational deformation has not been separated from the other optical aberrations. We utilized a two-surface comparison method to quantify the gravitational deformation in a vertical Fizeau interferometer. Certain aberrations vary with rotation around the optical axis. We averaged the ordinary aberrations and isolated the aberration caused by gravitational deformation. Experimental results show that a 4-in concave surface with an F -number 0.75 reveals to have a gravitational deformation of 7 nm peak-to-valley.