Guest post by Nic Widerhold, owner, Ghost Productions.
To the average person, holography is the stuff of science fiction. Many people were first exposed to the concept of practical holography in the original “Star Wars” film, released in 1977. Although the apparent 3D images represented in the film were of relatively low resolution, the possibilities were undeniably intriguing — and undoubtedly inspirational to a generation of budding scientists. Subsequent portrayals of the inherent possibilities of this technology were explored on television series, such as “Star Trek: The Next Generation,” in the late 1980s and early 1990s.
Holography: From Science Fiction to Scientific Fact
In that imagined world, holography was vastly superior to the grainy, static-filled images portrayed in “Star Wars.” Entire interactive worlds were recreated in a special space. The unimaginably advanced technology was primarily used for recreation. This fictional technology more closely resembled the 3D interactive “worlds” promised by various recently introduced virtual reality (VR) systems. Although actual VR technology is arguably in its infancy, and interactive content is still largely lacking, these systems come closest to reproducing the experience of entering a “holodeck,” where fully realized, interactive, imagined worlds can be explored at will.
A Brief History
Of course, none of these imagined uses of holographic technology reflect present, real-world applications. That’s not to say holography doesn’t exist. It does, and has done since before the time of the original “Star Trek” series, which debuted in 1966. Although that seminal science fiction series made no mention of holography, the technology already existed in the real world, having begun conceptual development as early as the 1940s. In 1971, a Hungarian-British physicist was awarded the Nobel Prize in Physics for his invention of the holographic method. His success with optical holography was only made possible by the invention of the laser, in 1960.
In essence, a hologram is a photographic recording of a light field. The recording is subsequently projected to create a faithful 3D representation of the holographed subject. Technically speaking, it involves the encoding of a light field as an interference pattern. The pattern diffracts light to create a reproduction of the original light field. Any objects present in that original light field appear to be present, viewable from any angle.
Depth cures — such as parallax and perspective — are retained, changing as expected, depending on the viewpoint of the observer. Holograms have been compared to sound recordings. When a musician performs, the vibrations he produces are encoded, recorded, stored and later reproduced to evoke the original vibrations a listener would have experienced.
Of course, other forms of practical holography have been in common usage for decades. The so-called embossed hologram, which appears on many credit cards and even paper checks, was widely introduced in the mid-1980s. National Geographic magazine, which featured an image of a holographic eagle on its cover in 1984, marks the event among its most notable milestones.
The 2D embossed hologram image retains some of the characteristics of a traditional hologram, in that the image changes somewhat depending on one’s angle of view. It’s primarily used as a security measure, or as a marketing novelty (these mass-produced holograms have even appeared on boxes of children’s cereal). However, these illusions are not true holograms. While the National Geographic eagle was impressive, one could not simply examine the animal from any conceivable angle.
A Glimpse of the Future
Nevertheless, holography remains an intriguing and promising technology. Present practical applications include the use of digital holographic microscopy, and wide-angle, broadband holography, which is hailed as a technology that could expand the limits of large-angle holography. This development represents a potential dramatic improvement in medical imaging. Essentially, this latest advancement, pioneered by Israeli scientists, uses a nano-antenna chip in conjunction with a holography algorithm to obtain and manipulate the “phase map” of a light beam reflecting off the reference object.
Among other improvements, it could be harnessed to vastly improve present 3D imaging modalities, such as CT, in which 2D scans must be rotated, expanded, integrated and replotted repeatedly to generate the illusion of a true 3D image.
Another example of holography in medicine includes the recent demonstration that “… medical 3D-holoscopic content can be displayed on commercially available multiview auto-stereoscopic display,” as noted in a recent article published in the Journal of Endourology. Viewed in real time, the authors note that content can be viewed by multiple professionals, from different points of view, without the use of special 3D eyewear.
Using holographic technology, it should be possible to obtain a single image that faithfully reproduces structures, regardless of the angle of view. While holography largely remains an intriguing novelty, the possible applications for medical imaging — including improvements in image resolution, medical diagnosis, planning, information sharing and treatment — remains exceptionally bright.