Applications of Optical Holographics

The first part of the CMMPE’s three pronged research strategy revolves ariound developing applications for the exciting field of computer generated holography. A number of areas particularly interest us

  • Early stage cancer detection. Traditional imaging ignores the phase of light, only being interested in its intensity. Holographic image allows us to record the phase of light on a camera. This is extremely useful in medical imaging such as cancer detection where the extra information can make a life or death difference in diagnostics.
  • 2D holography has been used in displays and projectors for over a decade, fully 3D holograms are still in their infancy. As a bunch of trekkies, we in the CMMPE are really keen to be able to develop walk in 3D displays, not unlike the Star Trek Holodeck.
  • While 3D displays on the scale of a room are still a long way off, 3D headsets are actively being developed by multiple companies in the UK and US. The CMMPE has been integral to the development of these holding a number of key patents in the area and our alumnii working for startups around the world.
  • The internet powers the world we live in and the tiny strands of glass that connect it all together are some of the most strictly engineered devices on the planet. CMMPE and its alumnii have pioneered some of the most in-depth techniques for measuring fibre optic performance as well as improving the information density.
  • Much talked about on the news at the moment is 3D printing, also known as additive manufacture. The CMMPE is currently developing an ultra-high power system for additive manufacture using holograms.

CMMPE Strategy

What is Holography

Holography was invented by Dennis Gabor in 1948 for which he won the 1971 Nobel prize in physics. While initial research was high, interest waned due to the lack of coherent light sources and the conjugate image problem and it wasn’t until the invention of the ruby laser in 1960 by Theadore Maiman that interest in holography was rekindled.

White light holography was invented in 1962. The same year saw the first use of off-axis geometries followed in 1969 by the ’rainbow hologram’. This was soon followed by the invention of computer generated holograms (CGHs) with the first algorithms reported in 1966 based on earlier concepts by Rogers. Among early pioneers in digital holography was Joseph Goodman who pioneered many of the early commercialisations.

Initial growth in computer generated holography was slow due to the computational requirements and it wasn’t until the 80s that it found significant practical use in optical testing. It wasn’t until the invention of the kinoform, a phase rather than amplitude modulated hologram, that computer generated holography began to realise its full potential. Today, CGHs are widely using in image correction, fibre and wavelength multiplexing, image recognition, optical tweezing and video projection.

How it Works

A traditional optical camera uses a lens or lenses to focus the scattered light from an object onto a single point on a recording device. A difference in location on the device corresponds to a difference in approach vector of incident light. Loss of a portion of the record will cause a corresponding loss of a portion of the image.

Traditional Camera

Traditional Camera

Traditional Camera

A holographic system, on the other hand, collects the scattered light without requiring the use of a focusing optic instead interfering it with a reference beam. The original image can then be reconstructed by reproducing the recording conditions. The entire image is stored in any one part of the recording device and loss of a portion of the record only causes a loss in resolution of the image. Note that resolution here denotes the ability to resolve features in the image rather than referring to sampling density as it is more commonly used when describing a rastered image.

In traditional analogue holography, two steps are followed:

  • Recording - A coherent light source is collimated and split into two beams the object and reference beams. The object beam is directed onto a physical object and the resulting scattered light interfered with the reference beam. The interference fringes formed are recorded on a photosensitive film of other recording device to produce the hologram.

  • Reconstruction - A similar system is used to reproduce the hologram. An identical light source is directed onto the film leading to a visible output equivalent to viewing the object directly.

Traditional Camera

Hologram Recording

Traditional Camera

Hologram Reconstruction

Computer generated holography goes beyond this, using a known target image or scene to generate the reconstruction removing the need for a recording step.

2D vs 3D

In two dimensional holography where the target of interest is a projection onto a single plane. Examples of this include cinema projectors, lithography, beam shaping, optical tweezing, image recognition and mode sorting. You may not know it holograms are widely used in a vast array of dynamic optical systems.

An exciting new area of research is in three dimensional systems. These take into account the position of the viewer and require the inclusion of depth information and sampling at multiple planes. Examples of this include direct-to-eye systems where a 3D scene is projected directly into the eye.

Traditional 3D displays merely show a different image to each eye, so called stereoscopic vision. Holographic 3D displays go far beyond this producing images that look fully three dimensional to the viewer.


Holographic systems such as projectors have a number of advantages over traditional systems including:

  • Efficiency - High power projectors typically exhibit less than 10% efficiency with cooling representing the majority fo the bulk of modern products. The amplitude modulation element implies a physical limit to efficiency due to the requirement to block incident light. A typical colour display pixel averages at around 20% of full intensity, the remainder absorbed by the SLM. In contrast, multi-level phase holography has a near 100% theoretical efficiency and is able to use the totality of the incident light.
  • Dissipation - The use of phase modulation allows for the redirection of waste energy away from the SLM towards heat-sinks unlike in traditional systems.
  • Resolution - The continuous nature of holographic images allows for much greater control of the output image. Advanced generation algorithms allow for adaptive local resolutions in areas of interest at the expense of resolution elsewhere.
  • Robustness, Size and Cost - Holographic systems don’t require polarisers, unlike many traditional projectors, and far fewer lenses. This helps reduce system size and cost and improve reliability.
  • 3D Views - Holographic systems are capable of completely reproducing a 3D light field. Psychological depth cues including perspective, parallax, stereopsis, occlusion and defocus blur can be artificially incorporated. This is contrast to current 3D visualisation techniques that are strictly stereoscopic in their application and are known to cause vision issues for users. .