Two-wavelength micro-interferometry for 3-D surface profiling

Surface Micro Topography Measurement Using Interferometry

“…Several phase-shifting algorithms have been developed with a view to reduce the effect of the phase shift and other errors on phase calculation (Kumar, et al, 2009). The evaluated phase is wrapped between   and  due to arctangent function.…”

“…Using the first stored phase-shifted frames ( 02 j ), the phase distribution of the object can be expressed as follows (Kumar, et al, 2009):…”

Structure light telecentric stereoscopic vision 3D measurement system based on Scheimpflug condition

“…The traditional contact-detection method, for example, Micro-CMM [1,2] has not satisfied the requirements of fast, highly accurate, and non-destructive detection in the microelectronics manufacturing industry. Therefore, many scholars-both domestic and foreign-have proposed non-contact optical measurement methods, such as confocal microscopy [3,4], white-light interferometry [5,6], and microscopic fringe projection [7][8][9][10]. Even if the resolution of confocal microscopy and whitelight interferometry reach nano-level, the measurement range is merely several millimeters.…”

Quadrature wavelength scanning interferometry

“…Another disadvantage of PSI is the 2π ambiguity that is encountered when measuring discontinuous surfaces with step heights larger than half the wavelength of the light used [8]. Dual-wavelength methods allow one to extend the unambiguos measurement range to typical distances of few micrometres but do not avoid it [9,10].…”