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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.
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.
Confocal chromatic aberration: This method has the advantage of measuring certain height ranges without a vertical scan, can measure very rough surfaces with ease, and smooth surfaces down to the single nm range. The fact that these sensors have no moving parts allows for very high scan speeds and makes them very repeatable.
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 ...
Part 602 describes this type of non-contact profilometer, incorporating a single point white light chromatic confocal sensor. The operating principle is based upon the chromatic dispersion of the white light source along the optical axis, via a confocal device, and the detection of the wavelength that is focused on the surface by a spectrometer .
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
DHM performs static measurements of 3D surface topography as many other 3D optical profilometers (white light interferometers, confocal, focus variation, ... ). It enables to retrieve, roughness and shape of many surfaces. [32] [33] [34] Use of multiple wavelengths enable to overcome the l/4 limit of traditional phase shifting interferometers ...
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