image: Approximate bit rate magnitude of various telecommunication devices according to their year of introduction. Starting with the optical telegraph (or Chappe's semaphore) presented to Napoleon Bonaparte in 1798, with typical rate of transmission of approximately 2 to 3 symbols (196 different types) per minute, or 0.4 b/s. Followed by the electrical telegraph, popularized in the early 1840s using Samuel Morse's code, achieving a rate of approximately 100 b/s. Graham Bell's telephone was introduced in 1876 and supported voice frequency transmission up to 64 kb/s. The early NTSC black and white electronic television, available in the 1940s, had 525 interlaced lines and displayed images at a rate of 29.97 frames per second at a bit rate of 26 Mb/s7. The color NTSC format was introduced 10 years later and tripled the black and white bandwidth to accommodate red, green, and blue channels. More recently, the digital video format makes it easier to establish the bit rate based on pixel count (excluding compression) with HDTV 720p@1.33 Gb/s in 1990, ultra-HDTV 2160p(4K)@12.7 Gb/s in 2010, and currently 4320p(8K)@47.8 Gb/s. Holographic 3D displays is expected to have a with a data rate of 3 × 1015 b/s, and by extrapolation of the previous technology is predicted to emerge commercially by 2100. view more
Credit: by Pierre-Alexandre Blanche
The pioneers of holography, Gabor, Leith, Upatnieks, and Denisyuk, predicted very early that the ultimate 3D display will be based on this technique. This conviction was rooted on the fact that holography is the only approach that can render all optical cues interpreted by the human visual system. Holographic 3D displays have been a dream chased after for many years, facing challenges on all fronts: computation, transmission, and rendering. With numbers such as 6.6 × 1015 flops required for calculations, 3 × 1015 b/s data rates, and 1.6 × 1012 phase pixels, the task has been daunting. In a new review paper published in Light Science & Application, Prof. Blanche from the University of Arizona is reviewing the recent accomplishments made in the field of holographic 3D display. Specifically, the new developments in machine learning and neural network algorithms demonstrating that computer-generated holograms approach real-time processing. A section also discuss the problem of data transmission that can arguably be solved using clever compression algorithms and optical fiber transmission lines. Finally, we introduce the last obstacle to holographic 3D display, which is is the rendering hardware. However, there is no further mystery. With larger and faster spatial light modulators (SLMs), holographic projection systems are constantly improving. The pixel count on liquid crystal on silicon (LCoS) as well as micro electro-mechanical systems (MEMS) phase displays is increasing by the millions, and new photonic integrated circuit phased arrays are achieving real progress. It is only a matter of time for these systems to leave the laboratory and enter the consumer world.
Holography is still considered as the ultimate technology that will enable rendering of all the optical cues needed for the human visual system to see projected images in 3D. All other technologies, such as (auto) stereoscopy, light-field, or volumetric displays suffer from trade-offs that limit 3D rendering. Nonetheless, these technologies will likely prove to be stepping stones leading to better visual comfort until holographic displays are achieved.
Some of the doors that were preventing holographic television from being made possible only a few years ago have already been unlocked. The fast computation of 3D holograms to properly control occlusions and parallax is now within reach as is a solution to the problem of data transmission. The exact architecture of the network (thick or lean client) is unclear, but higher compression rates and ever faster telecommunication infrastructures supporting the Internet mobile communications make streaming the data for a holographic television feasible, if not yet accessible.
However, some challenges remain to be solved. The two main obstacles at the time this manuscript was written are the computation of photorealistic 3D holograms in a reasonable amount of time, and a suitable electronic device for the reproduction of large holographic 3D images with high resolution.
Journal
Light: Advanced Manufacturing