Holographic Technology

Summary

Holographic technology employs beams of light to record information and then rebuilds that information so that the reconstruction appears three-dimensional. Unlike photography, which traditionally produces fixed two-dimensional images, holography re-creates the lighting from the original scene. It results in a hologram that can be viewed from different angles and perspectives as if the observer were seeing the original scene. The technology, which was greatly improved with the invention of the laser, is used in various fields such as product packaging, consumer electronics, medical imaging, security, architecture, geology, and cosmology.

Definition and Basic Principles

Holography is a technique that uses interference and diffraction of light to record a likeness and then rebuild and illuminate that likeness. Holograms use coherent light, which consists of waves that are aligned with one another. Beams of coherent light interfere with one another as the image is recorded and stored, thus producing interference patterns. When the image is re-illuminated, diffracted light allows the resulting hologram to appear three-dimensional. Unlike photography, which produces a fixed image, holography re-creates the light of the original scene and yields a hologram, which can be viewed from different angles and different perspectives just as if the original subject were still present.

Several basic types of holograms can be produced. A transmission hologram requires an observer to see the image through light as it passes through the hologram. A rainbow hologram is a special kind of transmission hologram in which colors change as the observer moves their head. This type of transmission hologram can also be viewed in white light, such as that produced by an incandescent lightbulb. A reflection hologram can also be viewed in white light. This type allows the observer to see the image with light reflected off the surface of the hologram. The holographic stereogram uses attributes of both holography and photography. Industry and art utilize the basic types of holograms as well as create new and advanced technologies and applications.

Background and History

Around 1947, Hungarian-born physicist Dennis Gabor developed the basics of holography while attempting to improve the electron microscope. Early efforts by scientists to develop the technique were restricted by the use of the mercury arc lamp as a monochromatic light source. This inferior light source contributed to the poor quality of holograms, and the field advanced little throughout the next decade. Laser light was introduced in the 1960s and was considered stable and coherent. Coherent light contains waves that are aligned with one another and is well-suited for high-quality holograms. Subsequently, discoveries and innovations in the field began to increase and accelerate.

In 1960, American physicist Theodore Harold Maiman of Hughes Research Laboratories developed the pulsed ruby laser. This laser used rubies to operate and generated powerful bursts of light lasting only nanoseconds. The pulsed ruby laser, which acted much like a camera's flashbulb, became ideal for capturing images of moving objects or people.

In 1962, while working at the University of Michigan, scientists Emmett Leith and Juris Upatnieks decided to improve on Gabor's technique. They produced images of three-dimensional (3-D) objects—a toy bird and train. These were the first transmission holograms and required an observer to see the image through light as it passed through the holograms.

Also in 1962, Russian scientist Yuri Nikolaevich Denisyuk combined his own work with the color photography work of French physicist Gabriel Lippmann. This resulted in a reflection hologram that could be viewed with white light reflecting off the surface of a hologram. Reflection holograms do not need laser light to be viewed.

In 1968, electrical engineer Stephen Benton developed the rainbow hologram. When an observer of a rainbow hologram moves their head, they see the spectrum of color, as in a rainbow. This type of hologram can also be viewed in white light.

Holographic art appeared in exhibits beginning in the late 1960s and early 1970s, and holographic portraits made with pulsed ruby lasers found some favor beginning in the 1980s. Advances in the field have continued, and many and varied types of holograms are used in many different areas of science and technology, while artistic applications have lagged in comparison.

How It Works

A 3-D subject captured by conventional photography becomes stored on a medium, such as photographic film, as a two-dimensional (2-D) scene. Information about the intensity of the light from a static scene is acquired, but information about the path of the light is not recorded. Holographic creation captures information about the light, including the path, and the whole field of light is recorded.

A beam of light first reaches the object from a light source. Wavelengths of coherent light, such as laser light, leave the light source “in phase” (in sync) and are known collectively as an object beam. These waves reach the object, are scattered, and then are interfered with when a reference beam from the same light source is introduced. A pattern occurs from the reference beam interfering with the object waves. This interference pattern is recorded on the emulsion. Re-illumination of the hologram with the reference beam results in the reconstruction of the object's light wave, and a 3-D image appears.

Light Sources. An incandescent bulb generates light in a host of different wavelengths, whereas a laser produces monochromatic wavelengths of the same frequency. Laser light, also referred to as coherent light, is used most often to create holograms. The helium-neon laser is the most commonly recognized type.

Types of lasers include all gas-phase iodine, argon, carbon dioxide, carbon monoxide, chemical oxygen-iodine, helium-neon, and many others.

To produce wavelengths in color, the most frequently used lasers are the helium-neon (for red) and the argon-ion (for blue and green). Lasers at one time were expensive and sometimes difficult to obtain, but modern-day lasers can be relatively inexpensive and are easier to use for recording holograms.

Recording Materials. Light-sensitive materials such as photographic films and plates, the first resources used for recording holograms, still prove useful. Since the color of light is determined by its wavelength, varying emulsions on the film that are sensitive to different wavelengths can be used to record information about scene colors. However, many different types of materials have proven valuable in various applications.

Other recording materials include dichromate gelatin, elastomers, photoreactive polymers, photochromics, photorefractive crystals, photoresists, photothermoplastics, and silver-halide sensitized gelatin.

Applications and Products

Art. Holographic art, prevalent in the 1960s through the 1980s, still exists. Although fewer artists practice holography exclusively, many artistic creations contain holographic components. A small number of schools and universities teach holographic art.

Digital Holography. Digital holography is one of the fastest-growing realms and has applications in the artistic, scientific, and technological communities. Computer processing of digital holograms lends an advantage, as a separate light source is not needed for re-illumination.

Digital holography first appeared in the late 1970s. The process initially involved two steps: first writing a string of digital images onto film, then converting the images into a hologram. Around 1988, holographer Ken Haines invented a process for creating digital holograms in one step. In the twenty-first century, artificial intelligence technology is being applied to hologram creation.

Digital holographic microscopy (DHM) can be used noninvasively to study changes in the cells of living tissue subjected to simulated microgravity. Information is captured by a digital camera and processed by software.

Display. Different types of holograms can be displayed in store windows; as visual aids to accompany lectures or presentations; in museums; at art, science, or technology exhibits; in schools and libraries; or at home as simple decorations hung on a wall and lit by spotlights.

Embossed Holograms. Embossed holograms, which are special kinds of rainbow holograms, can be duplicated and mass-produced. These holograms can be used as a means of authentication on credit cards and driver's licenses as well as for decorative use on wrapping paper, book covers, magazine covers, bumper stickers, greeting cards, stickers, and product packaging.

Holograms in Medicine and Biology. The field of dentistry provided a setting for an early application in medical holography. Creating holograms of dental casts markedly reduced the space needed to store dental records for Britain's National Health Service (NHS). Holograms have also proved useful in regular dental practice and dentistry training.

The use of various types of holograms has proved beneficial for viewing sections of living and nonliving tissue, preparing joint replacement devices, noninvasive scrutiny of tumors or suspected tumors, and viewing the human eye. A volume-multiplexed hologram can be used in medical-scanning applications.

Moving Holograms. Holographic movies created for entertaining audiences in a cinema are in development. While moving holograms can be made, limitations exist for the production of motion pictures. Somewhat more promising is the field of holographic video and possibly television.

Security. A recurring issue in world trade is that of counterfeit goods. Vendors increasingly rely on special holograms embedded in product packaging to combat the problem. The creation of complex brand images using holographic technology can offer a degree of brand protection for almost any product, including pharmaceuticals.

Security holography garners a large segment of the market. However, makers of security holograms, whose designs are used for authentication of bank notes, credit cards, and driver's licenses, face the perplexing challenge of counterfeit security images. As time progresses, these images become increasingly easier to fake; therefore, this area of industry must continually create newer and more complex holographic techniques to stay ahead of deceptive practices.

Stereograms. Holographic stereograms, unique and divergent, use attributes of both holography and photography. Makers of stereograms have the potential to create both very large and moving images. Stereograms can be produced in color and also processed by a computer.

Nonoptical Holography. Types of holography exist that use waves other than light. Some examples include acoustical holography, which operates with sound waves; atomic holography, which is used in applications with atomic beams; and electron holography, which utilizes electron waves.

Careers and Course Work

Outside of fine arts, careers that include holographic applications are varied. While studies should be concentrated in a particular industry or area of interest, students should have a basic foundation in chemistry, electronics, mathematics, and physics. Advanced courses in these subjects should be taken according to the requirements of the overall industry of interest. Coursework in computer science, software engineering, electrical engineering, laser technology, optics, and photography should also be given consideration. Students should earn at least a Bachelor of Science in their chosen field. For advanced career positions, a master's or doctorate degree is generally required.

Social Context and Future Prospects

Holography in one form or another is prevalent in modern society, whether as a security feature on a credit card, a component of a medical technique, or a colorful wrapping paper. Holograms have even allowed people to attend the concerts of long-dead musicians like Elvis Presley and Tupac Shakur. Holograms have been interwoven into daily life and will likely continue to increase their impact in the future.

Next-generation holographic storage devices have been developed, setting the stage for companies to compete for future markets. Data is stored on the surface of DVDs. However, devices have been invented to store holographic data within a disk. The significantly enlarged storage capacity is appealing for customers with large storage needs who can afford the expensive disks and drives, but some companies are also interested in targeting an even larger market by revising existing technology. Possible modification of existing technology could potentially result in less expensive methods of playing 3-D data. As the twenty-first century progressed, the use of holographic technology continued to be explored in the medical, communications, education, entertainment, printing, and security fields.

Bibliography

Ackerman, Daniel. "Using Artificial Intelligence to Generate 3D Holograms in Real-Time." Massachusetts Institute of Technology News, 10 Mar. 2021, news.mit.edu/2021/3d-holograms-vr-0310. Accessed 30 May 2024.

Ackermann, Gerhard K., and Jürgen Eichler. Holography: A Practical Approach. Wiley, 2007.

Hariharan, P. Basics of Holography. Cambridge UP, 2002.

Harper, Gavin D. J. Holography Projects for the Evil Genius. McGraw-Hill, 2010.

Johnston, Sean F. “Absorbing New Subjects: Holography as an Analog of Photography.” Physics in Perspective, vol. 8, no. 2, 2006, pp. 164–88. Academic Search Complete, search.ebscohost.com/login.aspx?direct=true&db=a9h&AN=21195787. Accessed 27 Oct. 2016.

Saxby, Graham, and Stanislovas Zacharovas. Practical Holography. 4th ed., CRC Press, 2016.

Shatkov, Dmitry. “How Holographic Technology Is Revolutionizing Cinema.” Hypervsn, 21 Mar. 2023, hypervsn.com/blog/how-holographic-technology-is-revolutionizing-cinema.html. Accessed 30 May 2024.

Veltman, Chloe. “What's Behind the So-Called 'Hologram' Celebrity Concerts.” NPR, 17 Mar. 2024, www.npr.org/2024/03/17/1239078698/whats-behind-the-so-called-hologram-celebrity-concerts. Accessed 30 May 2024.

Yaroslavsky, Leonid. Digital Holography and Digital Image Processing: Principles, Methods, Algorithms. Kluwer Academic, 2004.