In recent months, one company after another has come out with products that appear to create holograms—but according to optics experts, most do not use true holography to create their three-dimensional (3D) effects.
"A lot of people abuse the word 'holography,'" says James R. Fienup, Robert E. Hopkins Professor of Optics, and a professor of Electrical and Computer Engineering at the University of Rochester. "It's kind of a catchy thing"—a quick way to evoke the futuristic coolness of this sci-fi staple—"so they call things 'holograms' that have nothing to do with holography."
A notorious example is the so-called "Tupac hologram," which stunned audiences at the 2012 Coachella music festival by appearing to show the rapper Tupac Shakur performing on stage years after he had been killed. The stunt, which became an Internet sensation, only reinforced the public's misconception of what a hologram is. In fact, the effect didn't use holography at all; rather, it repurposed a classic magician's trick called Pepper's Ghost, an illusion created through the clever use of carefully angled mirrors.
The article is fine. BUT, the photograph in the Figure 1 with caption "Learning medicine in three dimensions with Microsoft's HoloLens" is completely opposite to what the author is saying in the abstract. Microsoft HoloLens is not producing any holographic image at all. On the contrary Microsoft HoloLens is just a see through stereoscopic head mounted display. It contains two diffractive mirror which are pre-fabricated reflection lenses manufactured either by diamond turning or optical holography. There is no holographic processing at all. A stereoscopic image pair is projected in front of the spectators' eyes through the diffractive mirrors.
The following comment was submitted on 11/16/2016:
Johnston, Holograms: A Cultural History (Oxford: Oxford University Press, 2016)
Johnston, 'Hologram: the story of a word and its cultural uses', Leonardo 49 (2017) [http://www.mitpressjournals.org/doi/abs/10.1162/LEON_a_01329?journalCode=leon#.WCwtmrKLSUk]
The following letter was published in the Letters to the Editor in the March 2017 CACM (http://cacm.acm.org/magazines/2017/3/213824).
Although Marina Krakovsky's news article "Bringing Holography to Light" (Oct. 2016) was timely (the visual interface will indeed dominate the future), the photo in the article's Figure 1 above the caption "Learning medicine in three dimensions with Microsoft's HoloLens." was completely opposite of what Krakovsky said in the article's opening sentence. Microsoft HoloLens is not even designed to produce a holographic image. On the contrary, Microsoft HoloLens is just a see-through stereoscopic head-mounted display, with two diffractive mirrors that are prefabricated diffractive reflection lenses manufactured either by diamond turning or optical holography. There is neither holographic processing nor holographic image reconstruction. In the HoloLens, a stereoscopic image pair is projected before the user's eyes through the diffractive mirrors. There is a marked difference between a stereoscopic 3D image and a holographic image. A holographic image can reproduce true 3D perspectives, whereas a stereoscopic 3D image cannot.
Kolkata, West Bengal, India
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