Optical Holography - PowerPoint PPT Presentation

1 / 20
About This Presentation
Title:

Optical Holography

Description:

Optical Holography M. Janda I. Han k Department of Computer science and Engineering University of West Bohemia Outline Introduction Wave Optics Principles Optical ... – PowerPoint PPT presentation

Number of Views:873
Avg rating:3.0/5.0
Slides: 21
Provided by: heraklesZ
Category:

less

Transcript and Presenter's Notes

Title: Optical Holography


1
Optical Holography
  • M. Janda I. Hanák
  • Department of Computer science and Engineering
  • University of West Bohemia

2
Outline
  • Introduction
  • Wave Optics
  • Principles
  • Optical holograms

3
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
4
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
5
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
6
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
7
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.
8
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

9
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

10
Diffraction And Again
11
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

12
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

13
Holography Principles in Pictures
  • Recording
  • Reconstruction

14
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

15
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

16
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

17
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

18
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

19
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
Write a Comment
User Comments (0)
About PowerShow.com