Digital holography extends the use of holography with the ability to provide quantitative values of both amplitude and phase information of object. As in traditional holography, a variety of setups are possible in reflection and transmission modes. Digital holography has shown to be applicable in a wide variety of applications from metrology to bio imaging. In transmission digital holography, quantitative phase information of the object can be related to the height variation of a transparent medium with constant refractive index to provide 3-D surface profile of the specimen. The Confocal microscope is an high resolution technique for optical metrology. By optical sectioning, out-of-focus blur is essentially absent from confocal imaging and high-resolution quantitative 3D images of specimen can be created. In this paper 3D profiles of micro-optical diffractive components are recorded with both a transmission digital holographic microscope (TDHM) and a confocal microscope to explore their capabilities and shortcomings. The principles and characteristics of TDHM and confocal microscope are discussed specifically towards surface-profiling of micro-optical diffractive components. For some components, 3-D imaging and profile measurements obtained with TDHM and the confocal microscope method provide close agreement while for others discrepancies between TDHM and the confocal microscope method are observed. The reasons for the differences in the 3-D imaging and profile measurement of these two methods are discussed and analyzed.

Date Published: 3 October 2008
PDF: 10 pages
Proc. SPIE 7155, Ninth International Symposium on Laser Metrology, 71550B (3 October 2008); doi: 10.1117/12.814509

Published in SPIE Proceedings Vol. 7155:
Ninth International Symposium on Laser Metrology
Chenggen Quan; Anand Asundi, Editor(s)