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Electronic speckle pattern interferometry (ESPI), [1] also known as TV holography, is a technique that uses laser light, together with video detection, recording and processing, to visualise static and dynamic displacements of components with optically rough surfaces. The visualisation is in the form of fringes on the image, where each fringe ...
Digital holography is the acquisition and processing of holograms with a digital sensor array, [1] [2] typically a CCD camera or a similar device. Image rendering, or reconstruction of object data is performed numerically from digitized interferograms. Digital holography offers a means of measuring optical phase data and typically delivers ...
A laser is divided into two beams by a beam splitter tilted by 45 degrees. The two beams propagate in the two perpendicular arms of the interferometer, are reflected by mirrors located at the end of the arms, and recombine on the beam splitter, generating interferences which are detected by a photodiode. An incoming gravitational wave changes ...
This is important because two waves of different frequencies do not produce a stable interference pattern. The coherence length of the laser determines the depth of field which can be recorded in the scene. A good holography laser will typically have a coherence length of several meters, ample for a deep hologram.
Linnik interferometer (microscopy) LUPI variant of Michelson; Lummer–Gehrcke interferometer; Mach–Zehnder interferometer; Martin–Puplett interferometer; Michelson interferometer; Mirau interferometer (also known as a Mirau objective) (microscopy) Moiré interferometer (see moiré pattern) Multi-beam interferometer ; Near-field interferometer
Since its introduction, vibrometry by holographic interferometry has become commonplace. Powell and Stetson have shown that the fringes of the time-averaged hologram of a vibrating object correspond to the zeros of the Bessel function (), where (,) is the modulation depth of the phase modulation of the optical field at , on the object. [1]
Although the Interferometric microscopy has been demonstrated only for optical images (visible light), this technique may find application in high resolution atom optics, or optics of neutral atom beams (see Atomic de Broglie microscope), where the Numerical aperture is usually very limited .
A vibrometer is generally a two beam laser interferometer that measures the frequency (or phase) difference between an internal reference beam and a test beam. The most common type of laser in an LDV is the helium–neon laser, although laser diodes, fiber lasers, and Nd:YAG lasers are also used.