holography

January 22, 2011 [HOLOGRAPHY BY ARITRA BAKUNDI]

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1. INTRODUCTION TO HOLOGRAPHY

With its many applications holography is one of the most interesting developments in modern

optics. Its scientific importance is emphasized by awarding the 1971 Nobel Prize to its

inventor Denis Gabor. The term “holography” is a compound of the Greek words “holos =

complete” and “graphein = to write.” It denotes a procedure for three-dimensional recording

and displaying of images and information without the use of lenses. Therefore holography

opens up completely new possibilities in science, engineering, graphics and arts. Fields of

applications are interferometric measurement techniques, image processing, holographic

optical elements and memories as well as art holograms.

History of Holography

The physical basics of holography are optics of waves, especially

interference and diffraction. The first achievements are that of C.

Huygens (1629–1694), who phrased the following principle:

every point that is hit by a wave is the origin of a spherical

elementary wave. Using this statement a lot of problems of

diffraction can be calculated by adding up the elementary waves.

Importantly on the way of developing holography there are also

the works of T. Young (1733–1829), A.J. Fresnel (1788-1827)

and J. von Fraunhofer (1877–1926). Already at the beginning of

the 19th century enough knowledge was at hand to understand Fig1.1 Denis Gabor

the principles of holography. - The Father of Holography

A lot of scientists were close to the invention of this method, few of them were G. Kirchhoff

(1824–1887), Lord Rayleigh (1842–1919), E. Abbe (1840–1905), G. Lippmann (1845–1921),

W.L. Bragg (1890–1971), M. Wolfke and H. Boersch.

But it took until 1948 when D. Gabor (1900–1979)

realized the basic ideas of holography. The origin of

holography was at first connected to problems in optics

of electrons. Gabor made his first groundbreaking

experiments using mercury vapour lamp. At the

beginning the holographic technique was of minor

importance and was forgotten for some time. It was not

until the coming up of laser technology when

developments in holography experienced a significant

upturn. So 23 years after his experiments Gabor was Fig 1.2 Hologram Artwork

awarded the Nobel Prize in 1971. in the MIT Museum


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The first holograms that recorded 3D objects were made in

1962 by Yuri Denisyuk in the Soviet Union and by Emmett Leith and

Juris Upatnieks at University of Michigan, USA. Advances in

photochemical processing techniques to produce high-quality display

holograms were achieved by Nicholas J. Phillips.This technique mark

the breakthrough for the practical application of holography. Several

types of holograms were made. Transmission holograms, such as those

produced by Leith and Upatnieks, are viewed by shining laser light

through them and looking at the reconstructed image from the side of

the hologram opposite the source. Fig 1.3 Juris Upatnieks

A later refinement, the “rainbow hologram”, allows more

convenient illumination by white light or other monochromatic

sources rather than by lasers. These are commonly seen today on

credit cards as a security feature and on product packaging. These

versions of the rainbow transmission hologram are commonly

formed as surface relief patterns in a plastic film, and they

incorporate a reflective aluminium coating that provides the light

from "behind" to reconstruct their imagery. Another kind of

common hologram, the reflection or Denisyuk hologram is capable

of multicolour image reproduction using a white light illumination

source on the same side of the hologram as the viewer. Fig 1.4 A Denisyuk Hologram

One of the most promising recent

advances in the short history of

holography has been the mass

production of low-cost solid-state lasers,

such as those found in millions of DVD

recorders and used in other common

applications, which are sometimes also

useful for holography. These cheap,

compact, solid-state lasers can, under

some circumstances, compete well with

the large, expensive gas lasers

previously required to make holograms,

and are already helping to make

holography much more accessible to

low-budget researchers, artists and

dedicated hobbyists. Fig1.5 Diagram of different holograms


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2. FUNDAMENTAL OF GENERATION

2.1 PHOTOGRAPHY & HOLOGRAPHY

2.1.1 Object Wave

To see an object it has to be illuminated. In doing so light is

scattered and object wave is created. This wave contains the

complete optical information of the object. The light wave is

characterized by two parameters: the amplitude, which describes the

brightness, and the phase, which contains the shape of the object. In

Fig. 2.1 two waves of different objects are shown which have Fig 2.1 Object wave

the same amplitudes but different phases. The objects have the same brightness but a

different shape. For most holograms the colour of the objects is not important, so the first

chapters only deal with light waves of one wavelength. These change for colour holography

which uses several wavelengths.

2.1.2 PHOTOGRAPHY

During the process of vision an

object is imaged by the eye lens onto

the retina. The optical path in a

camera is similar: the objective

creates an image on the film. For

observation or to photograph an

object it has to be illuminated. The

scattered light, i.e., the object wave,

carries the information of the object.

The light wave can be made visible

in a plane of the optical path, for

example using a screen. Fig 2.2 Imaging by a Lens

The object wave appears as a very complex light field (Fig. 2.2) which results from the

superposition of all waves emerging from the individual object points. If this light field could

be recorded on a screen and displayed again, an observer (or a camera) would see an image

that is not discriminable from the object. If there is a photographic film at the position of the

screen, the object wave will cause a darkening distribution during the following processing of

the film. But only the light intensity is recorded; all information of the phase in the plane of

the screen is lost. This loss of phase also happens if the object is imaged onto a film by a lens.

Therefore the object wave can never be completely restored from a normal photographic

image. A two-dimensional image is the result.


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2.1.3 Holography

Holography uses the properties interference and diffraction of light which make it possible to

reconstruct the object wave completely. To be able to see these effects coherent laser light

has to be used. “Coherence” means that the light wave is constant and contiguous. The laser

on one hand illuminates the

object and the scattered light

hits the photographic film

(object wave) (Fig. 2.1). On

the other hand, the film is

illuminated directly with the

same laser (reference wave).

The object and the reference

waves interfere with each

other on the holographic

film. This generates

interference fringes in the

holographic layer as are

shown as a largely magnified

image in Fig. 2.4. The

distance of the fringes is in

the region of μm which is in

the order of magnitude of the

light wavelength. Fig 2.3 Principles of two stage imaging with Holography

The information of the object wave is contained in the modulation of the brightness of the

fringes and in the distance of the fringes. The photographic film is exposed and developed

resulting in the hologram. The first

step in holography, the recording, is

made. The second step, the

reconstruction or display of the

object wave, is shown in Fig. 2.3.

After developing the film the

hologram is illuminated with a light

wave that should resemble the

reference wave as best as possible.

Fig 2.4 Interference Fringes

This reconstruction wave is diffracted by the interference pattern of the hologram generating

the object wave. An observer looking at the hologram will see a three-dimensional image of

the object.


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3. Theory Behind Hologram

3.1 CONSTRUCTION AND RECONSTRUCTION OF

HOLOGRAPHY

Though holography is often referred to as 3D photography, this is a misconception. A better

analogy is sound recording where the sound field is encoded in such a way that it can later be

reproduced. In holography, some of the light

scattered from an object or a set of objects

falls on the recording medium. A second light

beam, known as the reference beam, also

illuminates the recording medium, so that

interference occurs between the two beams.

The resulting light field is an apparently

random pattern of varying intensity which is

the hologram. It can be shown that if the

hologram is illuminated by the original

reference beam, a light field is diffracted by

the reference beam which is identical to the

light field which was scattered by the object

or objects. Fig 3.1 Hologram Construction

Thus, someone who is looking into the hologram 'sees' the objects (referred to fig3.1) even

though it may no longer be there are a variety of recording materials which can be used,

including photographic film.

Fig 3.2 Hologram Reconstruction

http://en.wikipedia.org/wiki/Diffraction


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3.2 PLANE WAVEFRONTS

A diffraction grating is a structure with a repeating pattern. A simple example is a metal plate

with slits cut at regular intervals. Light rays travelling through it are bent at an angle

determined by λ, the wavelength of the light and d, the distance between the slits and is given

by sin = λ/d.

A very simple hologram can be made by superimposing two plane waves from the same light

source. One (the reference beam) hits the photographic plate normally and the other one (the

object beam) hits the plate at an angle θ. The relative phase between the two beams varies

across the photographic plate as 2π y sin/λ where y is the distance along the photographic

plate. The two beams interfere with one another to form an interference pattern. The relative

phase changes by 2π at intervals of d = λ/sin so the spacing of the interference fringes is

given by d. Thus, the relative phase of object and reference beam is encoded as the maxima

and minima of the fringe pattern.

When the photographic plate is developed, the fringe pattern acts as a diffraction grating and

when the reference beam is incident upon the photographic plate, it is partly diffracted into

the same angle θ at which the original object beam was incident. Thus the object beam has

been reconstructed. The diffraction beam created by two waves interfering has created the

“object beam” & the hologram is defined above.

3.3 POINT SOURCES

A slightly more complicated hologram can be made using a of light as object beam and

a plane wave as reference beam to illuminate the photographic plate. An interference pattern

is formed which in this case is in the form of curves of decreasing separation with increasing

distance from the centre.

The photographic plate is developed giving a complicated pattern which can be considered to

be made up of a diffraction pattern of varying spacing. When the plate is illuminated by the

reference beam alone, it is diffracted by the grating into different angles which depend on the

local spacing of the pattern on the plate. It can be shown that the net effect of this is to

reconstruct the object beam, so that it appears that light is coming from a point source behind

the plate, even when the source has been removed. The light emerging from the photographic

plate is identical to the light that emerged from the point source that used to be there. An

observer looking into the plate from the other side will "see" a point source of light whether

the original source of light is there or not.

This sort of hologram is effectively a concave lens, since it "converts" a plane wavefront into

a divergent wave-front. It will also increase the divergence of any wave which is incident on

it in exactly the same way as a normal lens does. Its focal length is the distance between the

point source and the plate.

http://en.wikipedia.org/wiki/Diffraction_grating


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3.4 COMPLEX OBJECTS

To record a hologram of a complex object, a laser beam is first split into two separate beams

of light using a beam-splitter of half-silvered glass. One beam illuminates the object,

reflecting its image onto the recording medium as it scatters the beam. The second (reference)

beam illuminates the recording medium directly. According to diffraction theory, each point

in the object acts as a point source of light. Each of these point sources interferes with the

reference beam, giving rise to an interference pattern. The resulting pattern is the sum of a

large number (strictly speaking, an infinite number) of point source + reference

beam interference patterns. When the object is no longer present, the holographic plate is

illuminated by the reference beam. Each point source diffraction grating will diffract part of

the reference beam to reconstruct the wave-front from its point source. These individual

wave-fronts add together to reconstruct the whole of the object beam. The viewer perceives a

wave-front that is identical to the scattered wave-front of the object illuminated by the

reference beam, so that it appears to him or her that the object is still in place. This image is

known as a "virtual" image as it is generated even though the object is no longer there.

3.5 MATHEMATICAL MODEL

A light wave can be modeled by a complex number U which represents the electric

or magnetic field of the light wave. The amplitude and phase of the light are represented by

the absolute value and angle of the complex number. The object and reference waves at any

point in the holographic system are given by Uo and UR. The combined beam is given be Uo +

UR. The energy of the combined beams is proportional to the square of magnitude of the

electric wave:

If a photographic plate is exposed to the two beams, and then developed, its transmittance, T,

is proportional to the light energy which was incident on the plate, and is given by

where k is a constant. When the developed plate is illuminated by the reference beam, the

light transmitted through the plate, UH is

It can be seen that UH has four terms. The first of these is kUo, since URU*Ris equal to one,

and this is the re-constructed object beam. The second term represents the reference beam

whose amplitude has been modified by UR2. The third also represents the reference beam

which has had its amplitude modified by Uo2; this modification will cause the reference beam

to be diffracted around its central direction. The fourth term is known as the "conjugate

object beam." It has the reverse curvature to the object beam itself, and forms a real image of

the object in the space beyond the holographic plate.


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4. DIVISIONS OF HOLOGRAMS

4.1 TRANSMISSION AND REFLECTION HOLOGRAMS

In this chapter the properties of different hologram types are presented. One differentiates

between transmission and reflection holograms depending on whether the hologram is to be

viewed in transmitted or in reflected light. The geometrical setup during recording specifies

which type of hologram is realized.

Fig 4.1 Transmission Hologram Fig 4.2 Reflection Hologram

It was referred several times to that hologram can be understood as a complicated diffraction

grating. After development the grating is formed by the opaque silver grains. During

reconstruction the light wave is diffracted and partially absorbed; hence these holograms are

called “amplitude holograms.” By using “bleaching baths” the silver can be converted into

translucent halide or even be removed completely from the emulsion. The diffraction grating

is then formed by areas of different index of refraction; a “phase hologram” is created.

4.2 THICK AND THIN HOLOGRAMS

Another characteristic to distinguish holograms is the thickness of the emulsion, d, compared

to the mean lattice constant in the hologram, dg. If d<< dg, one speaks of a “thin” hologram.

For the case of d >>dg, one speaks of a “volume hologram.” This difference plays an

important role in the diffraction efficiency, i.e., the brightness of the reconstructed image.

Thin holograms in principle have low diffraction efficiency whilst volume holograms exhibit

a larger brightness in the reconstructed image. In this chapter equations for the diffraction

efficiency of the individual holograms are derived and discussed.


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4.2 SPECIAL TYPES OF HOLOGRAMS

4.2.1 Computer Generated Holography

It is the method of digitally generating holographic interference

patterns. A holographic image can be generated e.g. by

digitally computing a holographic interference pattern and

printing it onto a mask or film for subsequent illumination by

suitable coherent light source. Alternatively, the holographic

image can be brought to life by a holographic 3D display Fig 4.3 3D Hologram

(a display which operates on the basis of interference of coherent light), bypassing the need

of having to fabricate a "hardcopy" of the holographic interference pattern each time.

Consequently, in recent times the term "computer generated holography" is increasingly

being used to denote the whole process chain of synthetically preparing holographic light

wave-fronts suitable for observation.

Computer generated holograms have the advantage

that the objects which one wants to show do not have

to possess any physical reality at all (completely

synthetic hologram generation). On the other hand, if

holographic data of existing objects is generated

optically, but digitally recorded and processed, and

brought to display subsequently, this is termed CGH

as well. Fig 4.4 Computer Generated Hologram

Ultimately, computer generated holography might serve all the roles of current computer

generated imagery: holographic computer displays for a wide range of applications

from CAD to gaming, holographic video and TV programs, automotive and communication

applications (cell phone displays) and many more.

4.2.2 Specular Holography

Specular holography is a technique for making

three dimensional images by controlling the

motion of specularities on a two-dimensional

surface. The image is made of much specularity

and has the appearance of a 3D surface-

stippling made of dots of light. Unlike

conventional wave-front holograms, specular

holograms do not depend on wave optics,

photographic media, or lasers. Fig 4.5 Specular Hologram of a Mummy

http://en.wikipedia.org/wiki/Holography

http://en.wikipedia.org/wiki/Interference_(wave_propagation)



http://en.wikipedia.org/wiki/3D_display

http://en.wikipedia.org/wiki/Computer

http://en.wikipedia.org/wiki/Computer-aided_design

http://en.wikipedia.org/wiki/3D

http://en.wikipedia.org/wiki/Stippling

http://en.wikipedia.org/wiki/Holograms


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The principle of operation is purely one

of geometric optics: A point light source produces a

glint on a curved specular (shiny) surface; this glint

appears to travel on the surface as the eye or light

source moves. If that motion is protectively

consistent with binocular disparity, the viewer will Fig 4.6 Specular Hologram of a Frog

perceive --- via stereo sis --- the illusion that the glint occurs at a different depth than the

surface that produces it. A specular hologram contains many such curved surfaces, all

embedded in a host surface. Each produces a glint and the brain integrates the many 3D cues

to produce a percept of a 3D shape.

4.2.3 Touchable Holography

Mid-air displays which project floating images in

free space have been seen in SF movies for

several decades. Recently, they are attracting a

lot of attention as promising technologies in the

field of digital signage and home TV, and many

types of holographic displays are proposed and

developed. You can see a virtual object as if it is

really hovering in front of you. But that amazing

experience is broken down the moment you reach

for it, because you feel no sense on your hand. Fig 4.7 Touchable Hologram of Rain Drops

That is achieved by our original tactile display [Iwamoto et al. 2008]. The given figure

explains the technologies employed for a “Touchable Holography.”

We use “Holo [Provision 2009],” a holographic display which provides floating images from

an LCD by utilizing a concave mirror. The projected images float at 30 cm away from the

display surface. A user can get near to the image and try to touch it. Of course, his fingers

pass through it with no tactile sensation.

“Airborne Ultrasound Tactile Display [Iwamoto et al. 2008]” is a tactile display which

provides tactile sensation onto the user’s hand. It utilizes the nonlinear phenomenon of

ultrasound; acoustic radiation pressure. When an object interrupts the propagation of

ultrasound, a pressure field is exerted on the surface of the object. The acoustic radiation

pressure P [Pa] is written as P = αE where E [J/m3] is the energy density of ultrasound & α is

a constant ranging from 1 to 2 depending on the reflection coefficient at the object surface.

While camera-based and marker-less hand tracking systems are demonstrated these days, we

use Wiimote (Nintendo) which has an infrared (IR) camera for simplicity. A retro reflective

marker is attached on the tip of user’s middle finger. IR LEDs illuminate the marker and two

Wiimotes sense the 3D position of the finger. Owing to this hand-tracking system, the users

can handle the floating virtual image with their hands.

The developed system can render various virtual objects because not only visual but also

tactile sensation is refreshable based on digital data. It is useful for video games, 3D CADs,

and so on. Here we show an example of demos. Fig. 4.5 shows a demo in which rain drops

http://en.wikipedia.org/wiki/Geometric_optics

http://en.wikipedia.org/wiki/Specular

http://en.wikipedia.org/wiki/Binocular_disparity

http://en.wikipedia.org/wiki/Stereopsis


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fall from above. When the rain drop hits the user’s palm, he feels tactile sensation created by

the ultrasound.

5. HOLOGRPHIC RECORDING MEDIA

Suitable media for a holographic recording should exhibit a high sensitivity for the laser

wavelengths used, a high resolution, a linear recording behaviour, low noise, the possibility

of erasing the recording, and reuse it as well as a low price. Depending on the application

area different recording media can be used which are listed in Table.

Table 5.1 Holographic Recording Media

5.1 SILVER HALIDE EMULSIONS

For decades silver halide emulsions have been used as a photographic film material; in

holography these are also the most widely used recording media. They exhibit a high

sensitivity and can be sensitized for the desired laser wavelengths by deposition of dyes.

These emulsions are used in laboratories that produce artistic or graphic works. In the past

few years many manufacturers such as Agfa, Ilford, and Kodak gave up production of

holographic emulsions. There are still some Agfa products around, but Agfa does not sell the

former 8E56/8E75 and 10E56/10E75. Compared to photography the silver halide crystals in

holographic emulsions are much smaller (30 to 90 nm diameter) such that the resolution

increases from about 100 to more than 5000 lines/mm.

5.2 WORKING PRINCIPLE

Silver halide layers for holography usually consist of a 5 to 7 μm thick layer of neutral

gelatine which is applied to a glass or film substrate. In this a suspension of silver halide

crystals, mostly AgBr, is deposited. By adding heavy metal ions and a weak reaction with

sulphide ions the layer is sensitized, i.e., it is made photosensitive. By using special colour

additives a sensitization for different wavelength areas can be accomplished. During exposure

of the emulsion silver is created according to the following equation:


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AgBr + hf = Ag + Br

During exposure only single Ag seeds are produced inside the AgBr grains which act as a

catalytic centre. A so-called latent image is created. During the developing process the

exposed grain is then completely reduced to silver producing an “amplification” of a factor of

106. That way these emulsions are much more sensitive than others (Tab. 5.1). The reduced

silver absorbs light and the emulsion appears black. Due to this amplitude holograms are

created; these can be transformed into phase holograms by bleaching.

Table 5.2 Properties of holographic silver halide emulsions

5.3 RESOLUTION

For volume holograms the grating constant dg inside the holographic layer can be calculated

from the Bragg condition:

dg = 𝜆 𝑛

2 sin (𝛿 2 )

Where δ denotes the angle between the object and reference wave inside the layer whilst λn =

λ/n denotes the wavelength in the emulsion with refraction index n. For example, this yields

for typical transmission holograms with δ = 60◦, λ = 633 nm, and n = 1.64 a spatial frequency

of σ = 1/λn = 2590 lines/mm. For white light reflection holograms with δ = 180◦ the spatial

frequency with σ = 5180 lines/mm is twice as high. Common photographic layers cannot be

used for holography due to their low resolution (σ = 40 to 600 lines/mm). The carrier

frequency for special holographic layers is around 5000 lines/mm (see Table 5.1). Some of

the new emulsions shown in Table 5.2 are still in the process of development [28–30].

Therefore within few years the properties of available holographic materials may change.

Today the Genet material has the highest resolution. As a consequence the exposure is


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comparatively high. Very much used in holographic laboratories are Slavich PFG-01 and Fuji

F-HL. Hypersensitisation using TEA is always necessary.


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5.4 SPECTRAL RESOLUTION The sensitivity of AgBr layers depends on the size of the light sensitive grains which governs

the degree of resolution. This means that high resolution films exhibit a low sensitivity (Table

5.2); it varies strongly with the laser wavelength. Depending on the type of laser used it is

advisable to to use different emulsions. For the red (He–Ne laser and ruby laser) and the blue

(argon and frequency-doubled neodymium laser) region special film material is available.

The spectral sensitivity is shown in Fig. 5.1, which illustrates the required energy density for

typical holograms using different wavelengths. Note that the red sensitive films have a gap in

the green region whilst the blue/green sensitive are insensitive for red light. This makes it

possible to work in the darkroom using the complimentary colour as illumination.

5.5 SPECTRAL RESOLUTION The sensitivity of AgBr layers depends on the size of the light sensitive grains which governs

the degree of resolution. This means that high resolution films exhibit a low sensitivity (Table

5.2); it varies strongly with the laser wavelength. Depending on the type of laser used it is

advisable to to use different emulsions. For the red (He–Ne laser and ruby laser) and the blue

(argon and frequency-doubled neodymium laser) region special film material is available.

The spectral sensitivity is shown in Fig. 5.1, which illustrates the required energy density for

typical holograms using different wavelengths. Note that the red sensitive films have a gap in

the green region whilst the blue/green sensitive are insensitive for red light. This makes it

possible to work in the darkroom using the complimentary colour as illumination.

5.6 DIFFRACTION EFFICIENCY Typical diffraction efficiency curves are given in Fig. 5.1. VRP-M and PFG- 01 of Slavich

are shown again. The highest diffraction efficiency is reached at 110 μJ/cm2 for PFG-01 and

about 80 μJ/cm2 for VRP-M. These values correspond with an optical density of 2.

5.7 SCATTERED LIGHT In Section 5.2 (noise) it was said that the granularity of the AgBr crystals produces scattered

light. Fine-grained films exhibit lower scattering than coarse-grained; the scattering occurs

mainly for small angles, i.e., for low spatial frequencies. In general the scattering decreases

with increasing wavelength; blue light is scattered stronger than red light. During the


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bleaching process of amplitude holograms to transform them into phase holograms the

diffraction efficiency increases but so does the noise.

6. APPLICATIONS OF HOLOGRAPHY

6.1 SECURITY

Security holograms are very difficult to forge because

they are replicated from a master hologram which

requires expensive, specialized and technologically advanced equipment. They are used

widely in many currencies such as the Brazilian real 20 note, British pound 5/10/20

notes, Canadian Fig 6.1 Master Card

Fig 6.2 20 £ Note

dollar 5/10/20/50/100 notes, Euro 5/10/20/50/100/200/500 notes, South Korean

Won 5000/10000/50000 notes, Yen 5000/10000 notes, etc. They are also used in credit and

bank cards as well as passports, books, DVDs, and sports equipment.

In 1983 MasterCard International, Inc. became the first to use hologram technology in bank

card security.

6.2 DATA STORAGE

Holography can be put to a variety of uses other than recording images. Holographic data

storage is a technique that can store information at high density inside crystals or

photopolymers. The ability to store large amounts of information in some kind of media is of

great importance, as many electronic products incorporate storage devices. As current storage

techniques such as Blu-ray Disc reach the limit of possible data density (due to

the diffraction-limited size of the writing beams), holographic storage has the potential to


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become the next generation of popular storage media.

The advantage of this type of data storage is that the

volume of the recording media is used instead of just the

surface.

Currently available SLMs can produce about 1000

different images a second at 1024×1024-bit resolution.

With the right type of media (probably polymers rather

than something like LiNeO3), this would result in about

1 gigabit per second writing speed. Read speeds can

surpass this and experts believe 1-terabit per second readout is possible.

In 2005, companies such as Opt-ware and Maxell have produced a 120 mm disc that uses a

holographic layer to store data to a potential 3.9 TB (terabyte), which they Fig 6.3

Holographic Versatile Disc plan to market under the name Holographic Versatile Disc.

Another company, In Phase Technologies, is developing a competing format.

While many holographic data storage models have used "page-based" storage, where each

recorded hologram holds a large amount of data, more recent research into using sub

micrometer-sized "micro holograms" has resulted in several potential 3D optical data

storage solutions. While this approach to data storage cannot attain the high data rates of

page-based storage, the tolerances, technological hurdles, and cost of producing a commercial

product are significantly lower.

PARAMETERS DVD BLU-RAY HVD

Capacity 4.7GB 25 GB 3.9 TB

Laser Wavelength 650 nm (red) 405 nm (blue) 532 nm (green)

Disc Diameter 120 mm 120 mm 120 mm

Hard Coating no yes yes

Data Transfer rate

(raw data ) 11.08mbps 36 mbps 1 gbps

Data Transfer rate

(audio/video) 10.08mbps 54 mbps 1gbps

Table 6.1 Comparison of DVD, BLU-RAY & HVD

6.3 ART

Early on artists saw the potential of holography as a medium and gained access to science

laboratories to create their work. Holographic art is often the result of collaborations between

scientists and artists, although some holographers would regard themselves as both an artist

and scientist.


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S Dali claimed to have been the first to employ

holography artistically. He was certainly the first

and best-known surrealist to do so, but the 1972

New York exhibit of Dalí holograms had been

preceded by the holographic art exhibition which

was held at the Cranbrook Academy Art in

Michigan in 1968 and by the one at the Finch

College gallery in New York in 1970, which

attracted national media attention.

During the 1970s a number of arts studios and schools were established, each with their

particular approach to holography. Notably there was the San Francisco School of

holography established by Llyod Cross.

Fig 6.4 Self Holographic Portrait The Museum of Holography in

New York founded by Rosemary (Possie) H. Jackson, the Royal College of Art in London

and the Lake Forest College Symposiums

organized by Tung Jeong (T.J) . None of

these studios still exist, however there is the

Center for the Holographic Arts in New

York and the HOLO center in Seoul which

offer artists a place to create and exhibit

work.

A small but active group of artists use

holography as their main medium and many

more artists integrate holographic elements

into their work. The MIT Museum and Jonathan Ross both have extensive collections of

holography and on-line catalogues of art holograms. Since the beginning of holography,

experimenters have explored the uses of holography. Starting in 1971 Lloyd Cross started the

San Francisco School of Holography and started to teach Fig 6.6 3D Hologram of

Bananas amateurs the methods of making holograms with inexpensive equipment. This

method relied on the use of a large table of deep sand to hold the optics rigid and

damp vibrations that would destroy the image.

Many of these holographers would go on to produce art holograms. In 1983, Fred Unterseher

published the Holography Handbook, a remarkably easy to read description of making

holograms at home. This brought in a new wave of holographers and gave simple methods to

use the then available AGFA silver halide recording materials.

In 2000 Frank DeFreitas published the Shoebox Holography Book and introduced using

inexpensive laser pointers to countless hobbyists. This was a very important development for

amateurs as the cost for a 5mw laser dropped from $1200 to $5 as semiconductor laser diodes

reached mass market. Now there are hundreds to thousands of amateur holographers

worldwide.

http://en.wikipedia.org/wiki/Silver_halide


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In 2006 a large number of surplus Holography Quality Green Lasers (Coherent C315)

became available and put Dichromate Gelatin (DCG) within the reach of the amateur

holographers. The holography community was surprised at the amazing sensitivity of DCG to

green light. It had been assumed that the sensitivity would be nonexistent. Jeff Blythe

responded with the G307 formulation of DCG to increase the speed and sensitivity to these

new lasers.

Many film suppliers have come and gone from the silver halide market. While more film

manufactures have filled in the voids, many amateurs are now making their own film. The

favorite formulations are Dichromate Gelatin, Methylene Blue Sensitized Dichromatic

Gelatin and Diffusion Method Silver Halide preparations. Jeff Blythe has published very

accurate methods for making film in a small lab or garage.

A small group of amateurs are even constructing their own pulsed lasers to make holograms

of moving object.

6.4 HOLOGRAPHIC

INTERFEROMETRY

Holographic interferometry is a technique

which enables static and dynamic

displacements of objects with optically

rough surfaces to be measured to optical

interferometric precision (i.e. to fractions of

a wavelength of light). It can also be used

to detect optical path length variations in

transparent media, which enables, for example, fluid flow to be visualized and analyzed. It

can also be used to generate contours representing the form of the surface. It has been widely

used to measure stress, strain, and vibration in engineering structures.

Fig 6.7 Interferometric Hologram

6.5 INTERFEROMETRIC MICROSCOPY

The hologram keeps the information on the amplitude and phase of the field. Several

holograms may keep information about the same distribution of light, emitted to various

directions. The numerical analysis of such holograms allows one to emulate large numerical

aperture which, in turn, enables enhancement of the resolution of optical microscopy. The

corresponding technique is called. Recent achievements of interferometric microscopy allow

one to approach the quarter-wavelength limit of resolution.


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7. CONCLUSIONS

Holography is one of the most recent developments in the field of science and technology.

Although it’s full potential has not been established but its increasing popularity and variety

of uses is amazing. The production cost of holograms and holographic images is the main

factor which is restraining its growth. With the use holography a very realistic picture can be

produced i.e., the 3-D images.

Its use in the field of security purpose helps us to protect important documents.

Holograms are used to give guarantee on not only electronic product and documents but also

currencies. Its use in the field of medical sciences has helped the doctors to detect diseases

more accurately.

Holography helps us to store a data much securely and for a prolonged period of time

as holograms are not easily destroyed. With the development of HVD i.e. holographic

versatile disc, a whopping 3.9 Terabytes (Tb) of data can be stored in a single disc. It will

also have a data transfer rate of 1Gbps i.e. 1 Gigabytes per second. When fully developed and

marketed the holographic optical storage devices, which HVD is a part of will definitely be

the very best.

FUTURE SCOPE

Dell monitoring advancements in optical technology and expects the cost and performance of

CD-RW drives become more competitive with the magnetic formats. Dell plan to offer CD-

RW/DVD ROM Combo Drives when reasonably priced. Reliable devices become available.

These devices should eventually replace current CD-RW drive and offer convenience, large

storage capacity that are backward compatible with previous CD formats, and DVD ROM

readability. Dell expects DVD-RAM systems to be adopted by high end users initially.

Rambo systems when available are expected to provide another system in a evolution to a

universal RMSD providing a larger capacity drive capable of reading and writing to the most

popular CD, DVD format.

HVD is still in the late stages of development, nothing is written in stone; but you've

probably noticed that the projected introductory price for an HVD is a bit steep. An initial

price of about $120 per disc will probably be a big obstacle to consumers. However, this

price might not be so insurmountable to businesses, which are HVD developers' initial target

audience. Opt-ware and its competitors will market HVD's storage capacity and transfer

speed as ideal for archival applications, with commercial systems available as soon as late

2006. Consumer devices could hit the market around this year.


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BIBLIOGRAPHY

WEB:

1. http://www.enteleky.com/holography/index.html

2. http://optics.caltech.edu/publications/SciAm-Nov1995/article.html

3. http://www.sciam.com/2000/0500issue/0500toigbox5.html

4. http://www.tweak3d.net/articles/howholo/print.shtml

5. http://www.research.ibm.com/journal/rd/443/ashley.html

6. http://www.sciam.com/1998/0198issue/0198working.html

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8. http://www.ub.rug.nl/eldoc/dis/science/g.malliaras/

9. http://www.espci.fr/Optique/photoref.htm

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12. http://www.demon.co.uk/cambsci/book10.htm

13. http://www.sawseek.com/prody3.html

14. http://www.almazoptics.com/homepage/LiNbO3.htm

15. http://www.elan.spb.ru/material/linbo.htm

16. http://b3020.phy.qub.ac.uk/phy803/files/twocolor.html

17. http://www.sciam.com/1998/0998issue/0998techbus3.html

18. http://www.guenthernet.com/holo/index_holo.html

19. http://allen.comm.virginia.edu/hp3e/ET/

20. http://www.bell-labs.com/org/physicalsciences/projects/hdhds/1.html

21. http://optics.caltech.edu/echuang/compact.html

22. http://optics.caltech.edu/steckman/Polymer/PMMA_PQ/PMMA_PQ.html

23. http://www.obara.elec.keio.ac.jp/projects/prc/interfero.htm

24. http://chem.pmf.hr/~mduksi/holografija

BOOKS:

1. Holography - A Practical Approach - G. Ackermann, J. Eichler (Wiley-VCH, 2007) WW.

2. Recording Materials for Holography and their Processing. Berlin: Springer, 1998.

3. Kasper, J.E.; Feller, S.A. The Complete Book of Holograms. New York: Dover, 2001.

4. Hariharan, P. Basics of Holography. Cambridge: Cambridge University Press, 2002.

http://chem.pmf.hr/~mduksi/holografija

holography

Documents

applications holography

photography holography

principles of holography

father of holography

theoriginof holography

history of holography

changefor colour holography

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