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Virtual imaging
Virtual imaging is a term coined by developers in China. It is a next-generation display technology that projects three-dimensional volumetric images into 3D space, where the images are physically volumetric rather than merely visually three-dimensional.
Broadly speaking, holographic projection can be considered a form of holographic imaging, but conventional holographic displays typically project onto a transparent "holographic plate," so the resulting image is essentially planar rather than volumetric. The fully volumetric holographic imaging technology that remains under research aims to produce physically three-dimensional images that viewers can observe from different angles without restriction and even enter into.
What is virtual imaging?
A virtual imaging system blends multiple image sources into real scenes. It typically suspends three-dimensional images within a display cabinet using a half-air imaging arrangement. The system comprises a cabinet, a beam-splitting mirror, spotlights, and video playback equipment. Based on beam-splitter imaging principles and special processing that constructs 3D models from photographed products, filmed live actors and 3D-generated objects are overlaid into real scenes via optical imaging devices, creating combined moving-and-static cinematic images. Virtual imaging offers a more direct 3D effect than conventional 3D cinemas, and viewers do not need special glasses to see the volumetric display effects, which provide strong depth perception.
The system uses widescreen environments, scene models, and lighting transformations to produce visual impact. Filmed live actors and 3D-made objects are composited into real scenes through optical imaging devices to produce mixed moving and static cinematic visuals, enabling a large amount of information to be presented in a relatively small space, transcending time and place and supporting creative presentation. Internationally, this technique is referred to as "Fanta-View Magic Vision." It uses optical imaging principles to combine footage shot with masking camera techniques and model scenery inside a display box, allowing an exhibit to vividly present themes and narratives, often accompanied by audio, lighting, and other special effects to create a strong impression.
Types of holographic projection
Holographic projection can be classified into several types. Transmission holography, such as the technique developed by Leith and Upatnieks, records holograms by illuminating a holographic film with a laser and observing the reconstructed image from the opposite side. Later improvements, such as rainbow holography, allow white light to be used for reconstruction. Rainbow holography is widely used in applications such as credit card security and product packaging; these holograms are typically embossed on a plastic film and aluminized on the back so that transmitted light reconstructs the image.
Another common approach is reflection holography, or Denisyuk holography, which uses white light from the observer's side to illuminate the film and reconstruct color images by reflection. Mirror-based holography produces three-dimensional images by controlling mirror motion on a two-dimensional surface, constructing holographic images via controlled reflection or refraction. Gabor holography reconstructs wavefronts through diffraction.
A key factor that accelerated the development of holographic projection was the mass production of low-cost solid-state lasers used in consumer devices such as DVD players. These compact, inexpensive solid-state lasers can, under certain conditions, rival the larger, costly gas lasers originally used for holography, enabling researchers, artists, and hobbyists with limited budgets to experiment with holographic techniques.
Industry developments
In June 2014, a California startup was reported to be developing a 3D holographic projection chip. The project aimed to produce a pill-sized 3D holographic projector with a reported resolution up to 5000P PI, capable of precise control of each beam's brightness, color, and angle. The initial chip was intended to project two-dimensional holographic images, with deliveries to phone manufacturers planned for summer 2015. A subsequent chip was planned to enable full volumetric 3D projection, producing floating stereoscopic images that appear like real objects. Beyond smartphones, the company planned to integrate such holographic projection chips into various display devices, including televisions, smartwatches, and holographic desktop systems.
Principles of holographic projection
Holographic projection technology, also called virtual imaging technology or front-projected holographic display, uses interference and diffraction principles to record and reproduce true three-dimensional images.
The first step uses interference to record object wave information during the exposure process. Under laser illumination, the photographed object produces a diffused object beam, while another portion of the laser serves as a reference beam that strikes the holographic plate. The interference between object and reference beams converts the phase and amplitude of the object wave at each point into spatial intensity variations. After development and fixing, the recorded plate becomes a hologram.
The second step uses diffraction to reconstruct the object wave information in the imaging process. The hologram functions as a complex grating; when illuminated by coherent laser light, a linearly recorded sinusoidal hologram typically produces two images: the real image and the conjugate image. The reconstructed image has strong stereoscopic effect and realistic visual appearance. Because each part of a hologram records information from all points of the object, in principle any fragment of the hologram can reproduce the entire original image. Multiple exposures can record different images on the same plate, which can be displayed separately without mutual interference.
