Optical Holography

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Optical Holography

• M. Janda I. Hanák
• Department of Computer science and Engineering
• University of West Bohemia

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Outline

• Introduction
• Wave Optics
• Principles
• Optical holograms

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Holography

• What is not holography
• Holodeck from Startrek
• What is holography
• Photography on steroids
• Both amplitude and phase is recorded
• Different intensity in different directions

Photo vs. Holo
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Holography A Tase Of Principle

• Fundamental technology
• Diffraction grating bends light
• Can be superposed
• Effect (bending) persists superposition
• Hologram ? super complex diffraction grating

Effect of diffraction grating on a direction of
light
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Wave Nature of Light

• Light
• Light El./Mag. radiation 300 800 nm
• A Bit of Mathematics
• u(p, t) A(p)cos2pnt j (p)
• u(p, t) RA(p)expi (j (p) 2pnt)
• u(p, t) A(p)expij (p)exp-i2pnt
• Complex Amplitude
• u(p) A(p)expij (p)

Phasor
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Interference

• What is it?
• Combination of waves
• Adding two lights together causes dark!
• What is it exactly?
• Summation of complex amplitudes
• ufu1 u2

Interference of two waves constructive and
destructive
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Interference

• Optical intensity
• Optical quality perceived by human eye
• Square of complex amplitudes magnitude
• Mathematically
• I u2 uu
• Intensity of interference

I ur us2 ur2 us2 urus urus
Ir Is 2? I1I2 cos(jr js)










This all is true only if coherent light is
assumed.
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Coherence

• Purpose
• Neglect temporal dependence
• Coherence light -gt stable interference
• Degree of coherence interference fringes
  visibility
• What light is coherent
• Monochromatic temporal coherence
• Coherence length
• Spherical waves spatial coherence
• Coherence area
• Formal description
• Binary relation
• Cross correlation between two signals

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Diffraction - Again

• What exactly is diffraction
• Everything not being reflection or refraction
• Interference of many sources
• Scalar Diffraction
• Easier in certain environment
• Huygens-Fresnel principle
• More precise formulations
• Kirchhoff
• Rayleigh-Sommerfeld

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Diffraction And Again
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Holography principle

• Recording
• Encoding phase and amplitude as interference
  fringe pattern
• Two beams interfering
• Reference beam known properties
• Scene beam recorded light field
• Complex diffraction grating is created hologram

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Holography principle

• Recording
• Encoding phase and amplitude as interference
  fringe pattern
• Two beams interfering
• Reference beam known properties
• Scene beam recorded light field
• Complex diffraction grating is created hologram
• Reconstructing
• Hologram illuminated with reference beam
• Diffraction occurs
• Resulting light field contains original scene beam

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Holography Principles in Pictures

• Recording
• Reconstruction

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In-line Hologram

• Recording
• Reference, object, hologram aligned in line
• Mostly transparent and planar objects
• Lower spatial frequency
• Reconstruction
• Images disturbed by blurred counterparts and zero
  order
• Special setup blurred image became background

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Off-axis Hologram

• Recording
• Non-zero angle between reference wave and object
  wave
• 3D opaque objects
• Higher spatial frequency
• Reconstruction
• Orders diffracted into different directions
• Clean original optical field

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Lens Fourier Hologram

• Lens
• Different optical material slowdown/diffraction
  of waves
• Use of thin lens assumption on lack of
  diffraction
• Back focal plane Ffront focal plane
• Fourier Hologram
• Recording through lens
• Fplanar image Fpoint source
• Reconstruction through lens
• Both virtual real image in focus

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Other holograms

• Holographic Stereograms
• Recording of multiple views through slit
• Reconstruction only single focus depth
• Rainbow Hologram
• 2 Stages of recording
• Record regular hologram
• Record rainbow hologram through slit
• Visible on white light multiple color images
• Color Hologram
• Common hologram rainbow due to diffraction
• 3 holograms 3 wavelengths larger gamut
• Achromatic holograms holographic stereograms
• Overlapping/coplanar colors

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Physical Representations

• Thin Amplitude Hologram
• Zero and first order only
• First order 6 of energy
• Thin Phase Hologram
• Multiple orders
• First order 33 of energy
• Volume Hologram
• Multiple layers of fringes
• Reflective ? transmission
• Sensitive only to selected wavelength

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Holography A Tase Of Principle

• Fundamental technology
• Diffraction grating bends light
• Can be superposed
• Effect (bending) persists superposition
• Hologram ? super complex diffraction grating

Effect of diffraction grating on a direction of
light
20
Physical Representations

• Thin Amplitude Hologram
• Zero and first order only
• First order 6 of energy
• Thin Phase Hologram
• Multiple orders
• First order 33 of energy
• Volume Hologram
• Multiple layers of fringes
• Reflective ? transmission
• Sensitive only to selected wavelength