Digital holography

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

Off-axis configuration

In the off-axis configuration, a small angle between the reference and the object beams is used to prevent overlapping of the cross-beating contributions between the object and reference optical fields with the self-beating contributions of these fields. These discoveries were made by Emmett Leith and Juris Upatnieks for analog holography,[2] and subsequently adapted to digital holography. In this configuration, only a single recorded digital interferogram is required for image reconstruction. Yet, this configuration can be used in conjunction with temporal modulation methods, such as phase-shifting and frequency-shifting.

Phase-shifting holography

The phase-shifting (or phase-stepped) digital holography process entails capturing multiple interferograms that each indicate the optical phase relationships between light returned from all points on the illuminated object and a controlled reference beam of light. The optical phase of the reference beam is shifted from one sampled interferogram to the next. From a linear combination of these interferograms, complex-valued holograms are formed. These holograms contain amplitude and phase information of the optical radiation diffracted by the object, in the sensor plane.[3]

Frequency-shifting holography

Through the use of electro-optic modulators (Pockel cells) or acousto-optic modulators (Bragg cells), the reference laser beam can be frequency-shifted by a tunable quantity. This enables optical heterodyne detection, a frequency-conversion process aimed at shifting a given radiofrequency optical signal component in the sensor's temporal bandwidth. Frequency-shifted holograms can be used for narrowband laser Doppler imaging.[4]

Multiplexing of holograms

Addressing simultaneously distinct domains of the temporal and spatial bandwidth of holograms was performed with success for angular,[5] wavelength,[6][7] space-division,[8] polarization,[9] and sideband [10] multiplexing schemes. Digital holograms can be numerically multiplexed and demultiplexed for efficient storage and transmission. Amplitude and phase can be correctly recovered.[11] The numerical access to the optical wave characteristics (amplitude, phase, polarization) made digital holography a very powerful method.

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[12]

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. [13] [14] [15]

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.[16]

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.[17][18][19] This technique is called interferometric microscopy.

See also

References

  1. ↑ U. Schnars, W. Jüptner (2005). "Digital Holography". Springer.
  2. ↑ Leith, E. N., & Upatnieks, J. (1962). Reconstructed wavefronts and communication theory. JOSA, 52(10), 1123-1128.
  3. ↑ I. Yamaguchi and T. Zhang, "Phase-shifting digital holography," Opt. Lett. 22, 1268-1270 (1997).
  4. ↑ M. Atlan, M. Gross, B. Forget, T. Vitalis, A. Rancillac, and A. Dunn, "Frequency-domain wide-field laser Doppler in vivo imaging," Opt. Lett. 31, 2762-2764 (2006)
  5. ↑ M. Paturzo, P. Memmolo, A. Tulino, A. Finizio, and P. Ferraro. Investigation of angular multiplexing and de- multiplexing of digital holograms recorded in microscope configuration. Opt. Express , 17(11):8709–8718, 2009.
  6. ↑ J. Kühn; T. Colomb; F. Montfort; F. Charrière; Y. Emery; E. Cuche; P. Marquet; C. Depeursinge (2007). "Real-time dual-wavelength digital holographic microscopy with a single hologram acquisition". Optics Express 15 (12): 7231–724. Bibcode:2007OExpr..15.7231K. doi:10.1364/OE.15.007231. PMID 19547044.
  7. ↑ Tomohiro Kiire, Daisuke Barada, Jun ichiro Sugisaka, Yoshio Hayasaki, and Toyohiko Yatagai. Color digital holography using a single monochromatic imaging sensor. Opt. Lett. , 37(15):3153–3155, Aug 2012.
  8. ↑ Tatsuki Tahara, Akifumi Maeda, Yasuhiro Awatsuji, Takashi Kakue, Peng Xia, Kenzo Nishio, Shogo Ura, Toshihiro Kubota, and Osamu Matoba. Single-shot dual- illumination phase unwrapping using a single wavelength. Opt. Lett. , 37(19):4002–4004, Oct 2012.
  9. ↑ T. Colomb; F. Dürr, E. Cuche, P. Marquet, H. Limberger, R.-P. Salathé, and C. Depeursinge (2005). "Polarization microscopy by use of digital holography: application to optical fiber birefringence measurements". Applied Optics 44 (21): 4461–4469. Bibcode:2005ApOpt..44.4461C. doi:10.1364/AO.44.004461.
  10. ↑ N. Verrier and M. Atlan. Absolute measurement of small-amplitude vibrations by time-averaged heterodyne holography with a dual local oscillator. arXiv preprint arXiv:1211.5328 , 2012
  11. ↑ M. Paturzo; P. Memmolo; L. Miccio; A. Finizio; P. Ferraro; A. Tulino; B. Javidi (2008). "Numerical multiplexing and demultiplexing of digital holographic information for remote reconstruction in amplitude and phase". Optics Letters 33 (22): 2629–2631. Bibcode:2008OptL...33.2629P. doi:10.1364/OL.33.002629. PMID 19015690.
  12. ↑ 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
  13. ↑ P.W.M. Tsang; K. Cheung; T. Kim; Y. Kim; T. Poon (2011). "Fast reconstruction of sectional images in digital holography". Optics Letters (36): 2650–2652.
  14. ↑ E. Lam; X. Zhang, H. Vo, T.-C. Poon, G. Indebetouw (2009). "Three-dimensional microscopy and sectional image reconstruction using optical scanning holography". Applied Optics 48 (34): H113–H119. Bibcode:2009ApOpt..48..113L. doi:10.1364/AO.48.00H113.
  15. ↑ X. Zhang; E. Lam, T.-C. Poon (2008). "Reconstruction of sectional images in holography using inverse imaging". Optics Express 16 (22): 17215–17226. Bibcode:2008OExpr..1617215Z. doi:10.1364/OE.16.017215.
  16. ↑ 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
  17. ↑ Y.Kuznetsova; A.Neumann, S.R.Brueck (2007). "Imaging interferometric microscopy–approaching the linear systems limits of optical resolution". Optics Express 15 (11): 6651–6663. Bibcode:2007OExpr..15.6651K. doi:10.1364/OE.15.006651. PMID 19546975.
  18. ↑ C.J.Schwarz; Y.Kuznetsova and S.R.J.Brueck (2003). "Imaging interferometric microscopy". Optics Letters 28 (16): 1424–1426. Bibcode:2003OptL...28.1424S. doi:10.1364/OL.28.001424. PMID 12943079.
  19. ↑ M. Paturzo; F. Merola; S. Grilli; S. De Nicola; A. Finizio; P. Ferraro (2008). "Super-resolution in digital holography by a two-dimensional dynamic phase grating". Optics Express 16 (21): 17107–17118. Bibcode:2008OExpr..1617107P. doi:10.1364/OE.16.017107. PMID 18852822.

Further reading

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