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Optical Engineering

Approach to higher spatial resolutions in a laser probe measurement system using a phase-only pupil filter
Author(s): Lirong Qiu; Weiqian Zhao; Zhengde Feng; Xuemei Ding
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Paper Abstract

Phase-only pupil-filtering differential confocal measurement, a new approach, is proposed to improve the spatial resolution of a laser probe measurement system (LPMS) for ultraprecise measurement of microstructural workpieces. The proposed approach uses a lateral superresolution pupil filter for sharpening the main lobe of the Airy spot to improve the LPMS lateral resolution and uses the differential confocal measurement method to improve the LPMS axial resolution, thereby improving the LPMS spatial resolution. In addition to improving the spatial resolution, linearity, and antiinterference capability of a confocal measurement system, the proposed approach can be used for bipolar absolute measurement and improvement of the measurement range. Experimental comparison and analyses indicate that the lateral resolution of a phase-only pupil-filtering differential confocal system can be improved by 50% over that of an LPMS with the same parameters, and a lateral resolution better than 0.27 μm and an axial resolution better than 3 nm can be achieved when the wavelength of the incident beam is λ=632.8 nm, the numerical aperture of the measuring lens is NA=0.65, and μM=4. It is therefore concluded that the phase-only pupil filtering differential confocal measurement method is a new approach to a higher spatial resolution of LPMSs and can be used for ultraprecise measurement of surface microcontours and microdimensions.

Paper Details

Date Published: 1 November 2006
PDF: 8 pages
Opt. Eng. 45(11) 113601 doi: 10.1117/1.2388944
Published in: Optical Engineering Volume 45, Issue 11
Show Author Affiliations
Lirong Qiu, Beijing Institute of Technology (China)
Weiqian Zhao, Harbin Institute of Technology (China)
Zhengde Feng, Harbin Institute of Technology (China)
Xuemei Ding, Harbin Institute of Technology (China)

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