A two-dimensional surface profile imaging technique that uses a low-coherence heterodyne interferometer is proposed. A double-grating frequency shifter was used in a tandem interferometer to provide the achromatic frequency shift for low-coherence light. A chopper, together with a processing circuit, was implemented to modulate the interference fringes. The surface profile was measured from the interference fringes taken by a CCD camera using a five-step method. The uncertainty in the displacement measurement is 0.34 μm for a displacement range of 43 μm. The surface profile of a glass sample with low effective reflectivity was acquired.
© 2005 Optical Society of America
(040.2840) Detectors : Heterodyne
(050.5080) Diffraction and gratings : Phase shift
(110.4980) Imaging systems : Partial coherence in imaging
(120.3180) Instrumentation, measurement, and metrology : Interferometry
(120.6660) Instrumentation, measurement, and metrology : Surface measurements, roughness
(190.2640) Nonlinear optics : Stimulated scattering, modulation, etc.
Original Manuscript: November 3, 2004
Revised Manuscript: February 1, 2005
Manuscript Accepted: March 9, 2005
Published: August 1, 2005
Kaiwei Wang and Lijiang Zeng, "Two-dimensional surface profile imaging technique based on a double-grating frequency shifter," Appl. Opt. 44, 4625-4630 (2005)