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Transport-of-intensity equation

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The transport-of-intensity equation (TIE) is a computational approach to reconstruct the phase of a complex wave in optical and electron microscopy.[1] It describes the internal relationship between the intensity and phase distribution of a wave.[2]

The TIE was first proposed in 1983 by Michael Reed Teague.[3] Teague suggested to use the law of conservation of energy to write a differential equation for the transport of energy by an optical field. This equation, he stated, could be used as an approach to phase recovery.[4]

Teague approximated the amplitude of the wave propagating nominally in the z-direction by a parabolic equation and then expressed it in terms of irradiance and phase:

where is the wavelength, is the irradiance at point , and is the phase of the wave. If the intensity distribution of the wave and its spatial derivative can be measured experimentally, the equation becomes a linear equation that can be solved to obtain the phase distribution .[5]

For a phase sample with a constant intensity, the TIE simplifies to

It allows measuring the phase distribution of the sample by acquiring a defocused image, i.e. .

TIE-based approaches are applied in biomedical and technical applications, such as quantitative monitoring of cell growth in culture,[6] investigation of cellular dynamics and characterization of optical elements.[7] The TIE method  is also applied for phase retrieval in transmission electron microscopy.[8]


  1. ^ Bostan, E. (2014). "Phase retrieval by using transport-of-intensity equation and differential interference contrast microscopy" (PDF). 2014 IEEE International Conference on Image Processing (ICIP). pp. 3939–3943. doi:10.1109/ICIP.2014.7025800. ISBN 978-1-4799-5751-4. S2CID 10310598.
  2. ^ Cheng, H. (2009). "Phase Retrieval Using the Transport-of-Intensity Equation". 2009 Fifth International Conference on Image and Graphics. pp. 417–421. doi:10.1109/ICIG.2009.32. ISBN 978-1-4244-5237-8. S2CID 15772496.
  3. ^ Teague, Michael R. (1983). "Deterministic phase retrieval: a Green's function solution". Journal of the Optical Society of America. 73 (11): 1434–1441. doi:10.1364/JOSA.73.001434.
  4. ^ Nugent, Keith (2010). "Coherent methods in the X-ray sciences". Advances in Physics. 59 (1): 1–99. arXiv:0908.3064. Bibcode:2010AdPhy..59....1N. doi:10.1080/00018730903270926. S2CID 118519311.
  5. ^ Gureyev, T. E.; Roberts, A.; Nugent, K. A. (1995). "Partially coherent fields, the transport-of-intensity equation, and phase uniqueness". JOSA A. 12 (9): 1942–1946. Bibcode:1995JOSAA..12.1942G. doi:10.1364/JOSAA.12.001942.
  6. ^ Curl, C.L. (2004). "Quantitative phase microscopy: a new tool for measurement of cell culture growth and confluency in situ". Pflügers Archiv: European Journal of Physiology. 448 (4): 462–468. doi:10.1007/s00424-004-1248-7. PMID 14985984. S2CID 7640406.
  7. ^ Dorrer, C. (2007). "Optical testing using the transport-of-intensity equation". Opt. Express. 15 (12): 7165–7175. Bibcode:2007OExpr..15.7165D. doi:10.1364/oe.15.007165. PMID 19547035.
  8. ^ Belaggia, M. (2004). "On the transport of intensity technique for phase retrieval". Ultramicroscopy. 102 (1): 37–49. doi:10.1016/j.ultramic.2004.08.004. PMID 15556699.