Holography

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Holography

  1. 1. HOLOGRAPHY<br />FROM : MUKUL TRIPATHI<br /> B.TECH FINAL YEAR (ECE)<br /> 06ESBEC049<br />
  2. 2. index<br />History of holography<br />Conventional photography<br />Holographic photography<br />Principles of holography<br />Hologram<br />Hologram construction<br />Hologram reconstruction<br />Types of hologram<br />Application of hologram<br />Conclusion<br />references<br />
  3. 3. History of Holography <br />Invented in 1948 by Dennis Gabor for use in electron microscopy, before the invention of the lASER<br />Leith and Upatnieks (1962) applied laser light to holography and introduced an important off-axis technique <br />
  4. 4. Conventional photography<br /><ul><li>2-d version of a 3-d scene
  5. 5. Photograph lacks depth perception or parallax
  6. 6. Film sensitive only to radiant energy
  7. 7. Phase relation (i.e. interference) are lost </li></li></ul><li>Holographic photography <br /><ul><li>Freezes the intricate wavefront of light that carries all the visual information of the scene
  8. 8. To view a hologram, the wavefront is reconstructed
  9. 9. View what we would have seen if present at the original scene through the window defined by the hologram
  10. 10. Provides depth perception and parallax </li></li></ul><li>Principle of holography<br />Fundamental technology<br />1 : Diffraction grating – bends light <br />2 : Can be superposed <br />3 : Effect (bending) persists superposition <br />4 : Hologram  super complex diffraction grating <br />
  11. 11. Hologram<br /><ul><li>Converts phase information into amplitude information (in-phase - maximum amplitude, out-of-phase – minimum amplitude)
  12. 12. Interfere wavefront of light from a scene with a reference wave
  13. 13. The hologram is a complex interference pattern of microscopically spaced fringes
  14. 14. “holos” – Greek for whole message </li></ul>  <br />
  15. 15. Hologram construction<br />When developed the photographic plate will have a transmittance which depends on the intensity distribution in the recorded plate <br /> tb – backgrond transmittance due to |R|2 term <br />B – parameter which is a function of the recording an developing process <br />
  16. 16. Hologram reconstruction<br />Direct wave – identical to reference wave (propagates along z) except for an overall change in amplitude <br />Object wave – Spherical wave except for a change in intensity B|r|2<br /> i.e. reconstructed wavefront <br />Conjugate wave – spherical wave collapsing to a point at a distance z to the right of the hologram<br /> 1 : a real image <br /> 2 : displaced by a phase angle 2kz <br />
  17. 17. Types of hologram<br />Transmission hologram<br />Reflection hologram<br />Holographic Stereograms<br />Rainbow hologram<br />Colour holograms<br />Lens hologram<br />Fourier hologram<br />
  18. 18. Transmission hologram<br />reference and object waves traverse the film from the same side <br />
  19. 19. Reflection hologram<br />reference and object waves traverse the emulsion from opposite sides <br />
  20. 20. Holographic Stereograms<br /><ul><li>Recording of multiple views through slit
  21. 21. Reconstruction: only single focus depth </li></li></ul><li>Rainbow hologram<br /><ul><li>2 Stages of recording </li></ul>1 : Record regular hologram <br />2 : Record rainbow hologram through slit <br /><ul><li>Visible on white light: multiple color images </li></li></ul><li>Colour hologram<br /><ul><li>Common hologram: rainbow due to diffraction
  22. 22. 3 holograms + 3 wavelengths: larger gamut
  23. 23. Achromatic holograms: holographic stereograms</li></ul>1 : Overlapping/coplanar colors <br />
  24. 24. Lens hologram<br /><ul><li>Different optical material: slowdown/diffraction of waves
  25. 25. Use of thin lens: assumption on lack of diffraction
  26. 26. Back focal plane = F{front focal plane} </li></li></ul><li>Fourier hologram<br /><ul><li>Recording through lens
  27. 27. F{planar image} + F{point source}
  28. 28. Reconstruction through lens
  29. 29. Both virtual & real image in focus </li></li></ul><li>Applications of hologram<br />Microscopy M = r/s<br />Increase magnification by viewing hologram with longer wavelength <br />Produce hologram  with x-ray laser, when viewed with visible light M ~ 106<br />3-d images of microscopic objects – DNA, viruses <br />Interferometry<br />Small changes in OPL can be measured by viewing the direct image of the object and the holographic image (interference pattern produce finges  Δl) <br />E.g. stress points, wings of fruit fly in motion, compression waves around a speeding bullet, convection currents around a hot filament <br />
  30. 30. conclusion<br />Holography is the only visual recording and playback process that can record our three-dimensional world on a two-dimensional recording medium and playback the original object or scene to the unaided eyes as a three dimensional image. The image demonstrates complete parallax and depth-of-field and floats in space either behind, in front of, or straddling the recording medium.<br />
  31. 31. references<br />BOOKS REFERED<br /> 1 : Barrekette’s application of holography<br /> 2 : Ostrovsky’s holography<br />Noble lecture by DENIS GABOR on his holographic module<br />www.google.com<br />
  32. 32. QUERY<br /> ?<br />

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