Holography Slids

8/2/2019 Holography Slids

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History of Holography

Invented in 1948 by Dennis Gabor for usein electron microscopy, before the

invention of the laser Leith and Upatnieks (1962) applied laser

light to holography and introduced an

important off-axis technique


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Holography:Do you see what I see?

Shawn Kennedy


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Word Origin

Hologram is from the Greek word holos,meaning whole and gramma meaning

message.


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Coherent Light and a Solution

Coherent light is light that ismonochromatic and of a single wavelength

In 1960, the invention of the laserovercame the non-coherent light problem


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History Continued

In 1962 Emmett Leith and Juris Upatnieksrealized that holography could be used as

a 3-D visual medium From their work, they used a laser to

create the first hologram in history, that ofa toy train and bird

This type of hologram required laser lightto be viewed, though.


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White Light and High Speed

Objects In 1962 Dr. Uri Denisyuk of the former

U.S.S.R. developed a white light reflection

hologram, which could be viewed in lightfrom a normal incandescent bulb.

In 1960, with the invention of the pulsed-

ruby laser, holograms of high speedobjects was made possible


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Pulsed-Laser Holography

Laser system emits a very powerful burstof light that lasts only a few nanoseconds,

which effectively freezes movement Enables a hologram to be made of a

human

The first hologram of a person was madein 1967


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How Holograms are Made

Need a laser, lenses, mirror, photographicfilm, and an object

The laser light is separated into twobeams, reference beam and object beam

Reference beam enlarged and aimed at a

piece of holographic film


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Making Holograms

Object beam directed at subject to berecorded and expanded to illuminate

subject Object beam reflects off of object and

meets reference beam at film

Produces interference pattern which isrecorded


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Making Holograms Cont.

Film is developed

Hologram illuminated at same angle as

reference beam during original exposureto reveal holographic image


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Applications of Holography

Design of containersto hold nuclear

materials Credit cards carry

monetary value

Supermarketscanners

Optical Computers

Improve design ofaircraft wings andturbine blades

Used in aircraftheads-up display

Art

Archival Recording offragile museumartifacts


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Holography in the Future

Medical Purposes

Gaming Systems

Personal Defense

Computers

Artwork Amusement Park Rides


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Holography goes Hollywood

Holodeck from Star Trek Holodeck Clip

Star Wars Chess Game

Body Double in Total Recall

The Wizard in Wizard of Oz
http://www.geocities.com/Hollywood/Studio/1164/home288.ramhttp://calvinzone.50megs.com/videos/wookiewin.movhttp://calvinzone.50megs.com/videos/wookiewin.movhttp://www.geocities.com/Hollywood/Studio/1164/home288.ram


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Conventional vs. Holographic

photography Hologram:

Converts phase information into amplitude

information (in-phase - maximum amplitude, out-of-phase minimum amplitude)

Interfere wavefront of light from a scene with areference wave

The hologram is a complex interference pattern ofmicroscopically spaced fringes

holos Greek for whole message


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Hologram of a point source

Construction of the hologram of a point source

Any object can be represented as a collection of points

Reference wave -plane

Photosensitive plate1. Records

interferencepattern (linearresponse)

2. Emulsion has

small grainstructure ()

Object wave - spherical

Photographic plate

x

z

y


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Point object hologram construction:

Intensity distribution on plate Reference wave

Object wave

Intensity distribution on plate

ROORRROOROyxI

zyxrwhere

oeezyxozyxO

reezyxrzyxR

ikrzyxi

ikzzyxi

****2

222

),,(

),,(

),(

),,(),,(

),,(),,(


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Hologram construction

)cos(2),(

0

)cos(2),,(

22

22

krororyxI

planefilmz

ororzyxI

Maxima for kr=2m or r=m

i.e. if the OPL difference OZ OP is an integral number of wavelengths, thereferencebeam arrives at P in step with the scattered (i.e. object) beam.

Gabor zone plate


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Hologram

When developed the photographic plate will havea transmittance which depends on the intensity

distribution in the recorded plate

tb backgrond transmittance due to |R|2 term

B parameter which is a function of therecording an developing process

)(**2 ORROOBtt b


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Hologram reconstruction

When illuminated by a coherent wave, A(x,y), known asthe reconstruction wave, the optical field emerging fromthe transparency is,

i.e. a superposition of 4 waves

If A(x,y)=R(x,y), i.e. reconstruction and reference wavesare identical,

ORBOBRRBOOttyxR

ABORRABOABOOAttyxA

bp

bp

2*2*

***

)(),(

),(


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Hologram reconstruction

Three terms in the reconstructed wave

ORBOBRRBOOttyxR bp2*2*

)(),(

Direct waveidentical to

reference waveexcept for an

overall change inamplitude

Object waveidentical to object

wave except for achange in intensity

Conjugate wave complexconjugate ofobject wave

displaced by aphase angle 2


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Hologram reconstruction Three terms in the reconstructed wave of

the point hologram

ikrikrkziikz

bp erBeBeeoBttyxR

222

)(),(

Direct waveidentical to

reference wave(propagates

along z) exceptfor an overall

change inamplitude

Object waveSpherical wave

except for achange in intensity

B|r|2i.e. reconstructed wavefront

Conjugate wavespherical wave

collapsing to a pointat a distance z to theright of the hologram

-a real image- displaced by aphase angle 2kz


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Hologram :

Direct, object and conjugate waves Direct wave: corresponds to zeroth order grating

diffraction pattern Object wave: gives virtual image of the object

(reconstructs object wavefront) first orderdiffraction

Conjugate wave: conjugate point, real image(not useful since image is inside-out due to

negative phase angle) first order diffraction In general, we wish to view only the object wave

the other waves just confuse the issue


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Off-axis- Direct, object and conjugate waves

Virtual image

Real image

Direct wave

Objectwave

Conjugate

wave

Reference wave

Use an off-axis system to record the hologram, ensuring separation of the three waves on reconstruction


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Transmission hologram: reference and object wavestraverse the film from the same side

Reflection hologram: reference and object waves

traverse the emulsion from opposite sides

HologramReflection vs. Transmission

View in Transmission View in reflection


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Hologram: Some Applications

Microscopy M = r/s Increase magnification by viewing hologram with longer

wavelength Produce hologram with x-ray laser, when viewed with visible

light M ~ 106 3-d images of microscopic objects DNA, viruses

Interferometry Small changes in OPL can be measured by viewing the direct

image of the object and the holographic image (interference

pattern produce finges l) E.g. stress points, wings of fruit fly in motion, compression wavesaround a speeding bullet, convection currents around a hotfilament

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Holography Slids