A multi-color in-line digital holographic microscope (DHM) has been developed for high speed profile measurement of micro-structures. The in-line architecture of the proposed DHM offers a high spatial resolution compared with the conventional off-axis DHM. The multi-color DHM captures the three color hologram simultaneously in one-shot recording by using a color CCD sensor and three RGB LED sources. The measurement range without phase ambiguity of the multi-color DHM is extended up to 5 micrometers compared with the 0.3 micrometer of the conventional single wavelength DHM technology. The real-time reconstruction rate of 3D profile is estimated around 20fps when using a 100 frame/sec CCD camera and a simple three-step phase shifting algorithm. The high reconstruction rate is important for the measurement in the shop floor where fast measurement and immunity to the environment disturbance are demanded. The air turbulence and floor vibration effects are further reduced by the near common-path architecture of the proposed DHM. A phase stability of better than 5nm is achieved without any need of anti-vibration instrument table and air turbulence protection cover.

Date Published: 15 November 2011
PDF: 6 pages
Proc. SPIE 8321, Seventh International Symposium on Precision Engineering Measurements and Instrumentation, 832140 (15 November 2011); doi: 10.1117/12.905847

Published in SPIE Proceedings Vol. 8321:
Seventh International Symposium on Precision Engineering Measurements and Instrumentation
Kuang-Chao Fan; Man Song; Rong-Sheng Lu, Editor(s)