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Figure 1: Schematic layout of a White-light Interferometer. A CCD image sensor like those used for digital photography is placed at the point where the two images are superimposed. A broadband “white light” source is used to illuminate the test and reference surfaces. A condenser lens collimates the light from the broadband light source.
Figure 3. White light interferometric microscope. White-light interferometry scanning (WLS) systems capture intensity data at a series of positions along the vertical axis, determining where the surface is located by using the shape of the white-light interferogram, the localized phase of the interferogram, or a combination of both shape and phase.
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
Diffraction-grating interferometer (white light) Double-slit interferometer; Dual-polarization interferometry; Fabry–Pérot interferometer; Fizeau interferometer; Fourier-transform interferometer; Fresnel interferometer (e.g. Fresnel biprism, Fresnel mirror or Lloyd's mirror) Fringes of Equal Chromatic Order interferometer (FECO) Gabor hologram
They can also use coherence scanning interferometry (CSI) with a white-light source to measure steep or rough surfaces, including machined metal, foam, paper and more. As is the case with all optical techniques, the interaction of light with the sample for this instruments is not fully understood.
Figure 1. The light path through a Michelson interferometer.The two light rays with a common source combine at the half-silvered mirror to reach the detector. They may either interfere constructively (strengthening in intensity) if their light waves arrive in phase, or interfere destructively (weakening in intensity) if they arrive out of phase, depending on the exact distances between the ...
Michelson interferometers using a white light source White light has a tiny coherence length and is difficult to use in a Michelson (or Mach–Zehnder ) interferometer. Even a narrowband (or "quasi-monochromatic") spectral source requires careful attention to issues of chromatic dispersion when used to illuminate an interferometer.
Interferometric scattering microscopy (iSCAT) refers to a class of methods that detect and image a subwavelength object by interfering the light scattered by it with a reference light field. The underlying physics is shared by other conventional interferometric methods such as phase contrast or differential interference contrast , or reflection ...