Kuli Ah Ke 13 Opt e Holography
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Transcript of Kuli Ah Ke 13 Opt e Holography
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Optik Terapan: HolographyKuliah ke 13
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Holografi:
Teori dikembangkan oleh seorang Ahli bernamaDennis Gabor pada tahun 1947 dan
mememangkan hadial Nobel pada Tahun 1971
Asal Kata : Holography di ambil dari bahasaYunani, kata hlos, "whole/seluruh" + graf,
"writing, drawing/menulis
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3
History of Holography
Invented in 1948 by Dennis Gabor for use inelectron microscopy, before the invention of thelaser
Leith and Upatnieks (1962) applied laser light toholography and introduced an important off-
axis technique
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Whats holography?
Holografi adalah sebuah proses atau teknikmembuat gambar / image 3 Dimensi daribenda.
Sebuah Hologram dihasilkan karena interaksi duacahaya laser.
Satu cahaya laser datang melalui benda ke film
/recorder Cahaya yang lain adalah cahaya referensi yangdatang langsung dari sumbernya ke film.
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For a better understanding of the process, it isnecessary to understand interferenceanddiffraction
Interferensi terjadi jika satu atau lebih mukagelombang berimpit atau bertemu.
Difraksi terjadi bila sebuah muka gelombangmembentur sebuah benda.
Physics of Holography
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Principle of Holography
Selama proses perekamam, object wave (gelombang yangmenyinari benda) dan reference wave (datang langsung daribenda) berinterferensi dalam bidang medium perekaman danmenghasilkan frinji interferensi. This photographic plate yangmenyimpang pola ini disebut Hologram.
Frinji Interferensi ini mengandung semua informasi tentangintensitas dan fase dari cahaya yang di hamburkan oleh benda.
Dalam Proses Rekonstruksi, hologramnya bertindak sepertisebuah kisi difraksi. Ini disinari oleh sebuah gelombang yangdisebut gelombang rekonstruksi. (n most cases this is similar tothe reference wave used for recording the hologram) and theimage of the object is reconstructed from the hologram.
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Merekam dan Melihat Hologram
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Konstruksi Suatu Hologram Membutuhkan Sebuah Laser (sumber cahaya yang koheren dan
monokromatik), lpembagi sinar, lensa cermin, film Fotografi, dan sebuahobjek atau benda.
Pembagi Sinar memisahkan cahaya laser menjadi dua berkas cahaya; Berkasreferensi dan berkas untuk benda.
Reference beam aimed at a piece of holographic film by mirrors. Object beam directed at object to be recorded to illuminate object and then
meets reference beam at film.
Menghasilkan pola interferensi dari berkas benda dan referensi yang
kemudian di rekam.
Film is developed./dicuci, hasilnya disebut hologram.
Hologram ni mengandung semua informasi tentang intensitas dan fase darigelombang-gelombang yang dihamburkan oleh objek/benda.
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Construction of HologramConstruction of Holograms
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Rekonstruksi sebuah Bayangan/gambar darisebuah hologram
To view the image, the hologram is again illuminated with anotherlaser beam called the reconstruction beam which is at same angle asreference beam.
Hologram acts as a diffraction grating.
This form a real image in front of the hologram and a virtual imagebehind the hologram.
The virtual image has all the characteristic of the object. The realimage can be photographed directly without using a lens.
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Reconstruction of an image from Hologram
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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 plate
1. Records
interference
pattern (linear
response)
2. Emulsion has
small grain
structure ( )
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
planef ilmz
ororzyxI
Maxima for kr=2m or r=m
i.e. if the OPL difference OZ OP is an integral number of
wavelengths, the referencebeam arrives at Pin step with the
scattered (i.e. object)beam.
Gabor zone
plate
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Hologram reconstruction
When illuminated by a coherent wave, A(x,y), known asthe reconstructionwave, 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 wave
identical to
reference waveexcept for an
overall change in
amplitude
Object wave
identical to object
wave except for a
change in intensity
Conjugate wavecomplex
conjugate of
object wave
displaced by a
phase angle 2
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Hologram reconstruction Three terms in the reconstructed wave of thepoint hologram
ikrikrkziikz
bp erBeBeeoBttyxR
222
)(),(
Direct wave
identical to
reference
wave
(propagates
along z)
except for an
overall change
Object wave
Spherical waveexcept for a
change in
intensity B|r|2i.e. reconstructed
wavefront
Conjugate wave
spherical wavecollapsing to a
point at a
distance z to the
right of the
hologram
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Direct, object and conjugate waves
Virtual
image
Real image
-z z
Direct wave
Object
wave
Conjuga
te wave
z=
Reference
wave
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Hologram :Direct, object and conjugate waves
Direct wave: corresponds to zeroth order gratingdiffraction pattern
Object wave: gives virtual image of the object(reconstructs object wavefront) first orderdiffraction
Conjugate wave: conjugate point, real image (notuseful 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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21Off-axis- Direct, object and conjugate waves
Virtual
image Real image
Direct wav
Object
wave
Conjuga
te 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 sameside
Reflectionhologram: reference and object waves
traverse the emulsion from oppositesides
HologramReflection vs. Transmission
View inTransmission View inreflection
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Hologram: Wavelength With a different color, the virtual image will
appear at a different angle (i.e. as a grating,
the hologram disperses light of differentwavelengths at different angles) Volume hologram: emulsion thickness >> fringe
spacing Can be used to reporduce images in their original color
when illuminated by white light. Use multiple exposures of scene in three primary
colors (R,G,B)
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Holography vs. Photography
Photography is 2D record of a 3D object whereas holography gives athree dimensional form of original object. If any object is hidden justbehind another object then the observer can see the hidden object inviewing the hologram.
Hologram is the positive pattern whereas in conventional photographynegative pattern is produced.
In ordinary photography each region contains separate and individualpart of the original object. Destruction of a portion of a negative leads to
an irreparable loss of information corresponding to the destroyed part.On the other hand, each part of a hologram contains information aboutthe entire object. Destruction of a part of hologram does not cause a lossof information about the object, each separate fragment is capable ofproducing image with a reduced clarity.
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Holography vs. Photography (contd)
The information holding capacity of a hologram isextremely high by recording several images of theobject whereas in ordinary photography a photofilmcannot be used to record several images.
Without the knowledge of the reference wavefrontthe hologram cannot be deciphered/read.
Holography vs. Photography
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Although there are no actual dots in a hologram, it could be
said that each of a hologram's "dots" contains the whole image.
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Views from different angles of the image reconstructed
by a hologram, showing changes in perspective.
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Applications of Holography
Mendesain Kontainer untukmenyimpan material nuklir
Kartu Kredit yang membawa
nilai mata uang Supermarket scanners
Optical Computers
Improve design of aircraftwings and turbine blades
Used in aircraft heads-updisplay
Art/Seni
Archival Recording of fragilemuseum artifacts/ Perekamanbarang museum yangsensitif/peka
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Applications of Holography
Microscopy M = r/s Increase magnification by viewing hologram with
longer wavelength
Produce hologram with x-ray laser, when viewed withvisible 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 waves around a speeding bullet,convection currents around a hot filament
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Star Wars : Obi-Wan - Hologram