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Embossed holograms are used widely on credit cards, banknotes, and high value products for authentication purposes. [3] It is possible to print holograms directly into steel using a sheet explosive charge to create the required surface relief. [15] The Royal Canadian Mint produces holographic gold and silver coinage through a complex stamping ...
The hologram keeps the information on the amplitude and phase of the field. Several holograms may keep information about the same distribution of light, emitted to various directions. The numerical analysis of such holograms allows one to emulate large numerical aperture, which, in turn, enables enhancement of the resolution of optical microscopy.
Computer-generated holography (CGH) is a technique that uses computer algorithms to generate holograms.It involves generating holographic interference patterns.A computer-generated hologram can be displayed on a dynamic holographic display, or it can be printed onto a mask or film using lithography. [1]
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.
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]
Volume holograms are holograms where the thickness of the recording material is much larger than the light wavelength used for recording. In this case diffraction of light from the hologram is possible only as Bragg diffraction, i.e., the light has to have the right wavelength (color) and the wave must have the right shape (beam direction, wavefront profile).
The rainbow hologram (also known as Benton hologram) is a type of hologram that was invented in 1968 by Dr. Stephen A. Benton at Polaroid Corporation (later MIT). [1] Rainbow holograms are designed to be viewed under white light illumination, rather than laser light which was required before this.
Unlike conventional wavefront holograms, specular holograms do not depend on wave optics, photographic media, or lasers. The principle of operation is purely one of geometric optics: A point light source produces a glint on a curved specular (shiny) surface; this glint appears to travel on the surface as the eye or light source moves.