1 / 20

Optical Holography

Optical Holography. M. Janda I. Hanák Department of Computer science and Engineering University of West Bohemia. Outline. Introduction Wave Optics Principles Optical holograms. Holography. What is not holography Holodeck from Startrek What is holography Photography on steroids

fineen
Download Presentation

Optical Holography

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  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)cos[2pnt – j (p)] • u(p, t) = R{A(p)exp[i (j (p) – 2pnt)]} • u(p, t) = A(p)exp[ij (p)]exp[-i2pnt] Complex Amplitude • u(p) = A(p)exp[ij (p)] ~ ~ Phasor

  6. Interference What is it? • Combination of waves • Adding two lights together causes dark! What is it exactly? • Summation of complex amplitudes uf=u1 + u2 ~ ~ ~ Interference of two waves – constructive and destructive

  7. Interference Optical intensity • Optical quality perceived by human eye • Square of complex amplitude’s magnitude • Mathematically I=|u|2 = uu* • Intensity of interference ~ ~ ~ I = |ur + us|2 = |ur|2 + |us|2 + 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 -> 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 = F{front focal plane} Fourier Hologram • Recording through lens • F{planar image} + F{point 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

More Related