User:Egelberg/Digital holography

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Digital holography is the technology of acquiring and processing

holographic measurement
data, typically via a CCD camera or a similar device. In particular, this includes the numerical reconstruction of object data from the recorded measurement data, in distinction to an optical reconstruction which reproduces an aspect of the object. Digital holography typically delivers three-dimensional surface or optical thickness data. There are different techniques available in practice, depending on the intended purpose. [1]

Digital analysis of holograms

Phase-shifting holograms

The phase-shifting digital holography process entails capturing multiple

interferograms
that each indicate the optical phase relationships between light returned from all sampled points on the illuminated surface and a controlled reference beam of light that is collinear to the object beam (in-line geometry). From a set of these interferograms, holograms are computed that contain information defining the shape of the surface. Multiple holograms gathered at multiple laser light wavelengths are then combined to compile the full shape of the illuminated object over its full dimensional extent.

Off-axis configuration

At the off-axis configuration where a small angle between the reference and the object beams is used. In this configuration, a single recorded digital hologram is sufficient to reconstruct the information defining the shape of the surface, allowing real-time imaging.

Multiplexing of holograms

Digital holograms can be numerically multiplexed and demultiplexed for efficient storage and transmission. Amplitude and phase can be correctly recovered.[2] The numerical access to the optical wave characteristics (amplitude, phase, polarization) made digital holography a very powerful method. Numerical optics can be applied to increase the depth of focus (numerical focalization) and compensate for aberration.[3]

interferograms obtained for different wavelengths.[4]
) or different polarizations [5]

Super-resolution in Digital Holography

Superresolution is possible by means of a dynamic phase diffraction grating for increasing synthetically the aperture of the CCD array[6]

Optical Sectioning in Digital Holography

Optical sectioning, also known as sectional image reconstruction, is the process of recovering a planar image at a particular axial depth from a three-dimensional digital hologram. Various mathematical techniques have been used to solve this problem, with inverse imaging among the most versatile. [7] [8]

Extending Depth-of-Focus by Digital Holography in Microscopy

By using the 3D imaging capability of Digital Holography in Amplitude an Phase it is possible to extend the depth of focus in Microscopy. [9]

Combining of holograms and interferometric microscopy

The digital analysis of a set of holograms recorded from different directions or with different direction of the reference wave allows the numerical emulation of an objective with large numerical aperture, leading to corresponding enhancement of the resolution.[10][11][12] This technique is called interferometric microscopy.

See also

References

  1. ^ U. Schnars, W. Jüptner (2005). "Digital Holography". Springer. {{cite journal}}: Cite journal requires |journal= (help)
  2. PMID 19015690.{{cite journal}}: CS1 maint: date and year (link
    )
  3. PMID 17106474. {{cite journal}}: Check date values in: |year= and |year= / |date= mismatch (help
    )
  4. PMID 19547044.{{cite journal}}: CS1 maint: date and year (link
    )
  5. PMID 16047894.{{cite journal}}: CS1 maint: date and year (link
    )
  6. ^ Super-resolution in digital holography by a two-dimensional dynamic phase grating M. Paturzo, F. Merola, S. Grilli, S. De Nicola, A. Finizio, and P. Ferraro Optics Express 16, 17107-17118 (2008). http://dx.doi.org/10.1364/OE.16.017107
  7. PMID 19956281.{{cite journal}}: CS1 maint: date and year (link
    )
  8. PMID 18958002.{{cite journal}}: CS1 maint: date and year (link
    )
  9. ^ Extended focused image in microscopy by digital holography P. Ferraro, S. Grilli, D. Alfieri, S. De Nicola, A. Finizio, G. Pierattini, B. Javidi, G. Coppola, and V. Striano Optics Express 13, 6738-6749 (2005). http://dx.doi.org/10.1364/OPEX.13.006738
  10. PMID 19546975.{{cite journal}}: CS1 maint: date and year (link
    )
  11. PMID 12943079.{{cite journal}}: CS1 maint: date and year (link
    )
  12. PMID 18852822.{{cite journal}}: CS1 maint: date and year (link
    )

Further reading

External links

Category:Holography

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