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White light interferometry is commonly used for detecting deformations of the wafer surface based on optical measurements. Low-coherence light from a white light source passes through the optical top wafer, e.g. glass wafer, to the bond interface. Usually there are three different white light interferometers: diffraction grating interferometers
The most important features of the light source are its wavelength and coherence length. The coherence length determines the width of the correlogram, which relies on the spectral width of the light source, as well as on structural aspects such as the spatial coherence of the light source and the numerical aperture (NA) of the optical system ...
Figure 2. File:Twyman-Green interferometer set up as a white light scanner. Vertical scanning interferometry is an example of low-coherence interferometry, which exploits the low coherence of white light. Interference will only be achieved when the path length delays of the interferometer are matched within the coherence time of the light source.
The advantages of white light, which produced a distinctive colored fringe pattern, far outweighed the difficulties of aligning the apparatus due to its low coherence length. [29] This was an early example of the use of white light to resolve the "2 pi ambiguity".
Fig. 2 shows use of a coherent (laser) source. Narrowband spectral light from a discharge or even white light can also be used, however to obtain significant interference contrast it is required that the differential pathlength is reduced below the coherence length of the light source. That can be only micrometers for white light, as discussed ...
Optical coherence tomogram of a fingertip. It is possible to observe the sweat glands, having "corkscrew appearance" Interferometric reflectometry of biological tissue, especially of the human eye using short-coherence-length light (also referred to as partially-coherent, low-coherence, or broadband, broad-spectrum, or white light) was investigated in parallel by multiple groups worldwide ...
Anthony Richardson scored on a 2-point conversion run up the middle with 12 seconds remaining in the fourth quarter to give the Indianapolis Colts a 25–24 win over the New England Patriots on ...
Early implementations of ms/LCI were in the time domain using lock-in detection in order to take advantage of long scanning depths as well narrow detection bandwidths. [2] As in traditional OCT, the beam interference coherence gates the light in order to filter out photons that have not traveled a sufficient path length.