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<div><font face="Arial" size="+1" color="#000000">Seminar on<br>
<b>Modern Optics and Spectroscopy<br>
<br>
<br>
Gabriel Popescu</b>, MIT<br>
<br>
<i><b>Quantitative phase imaging: watching cells waltz<br>
<br>
</b></i>October 3, 2006<br>
<br>
12:00 noon - 1:00 p.m.<br>
<br>
<b>Abstract:<br>
<br>
</b>Phase contrast (PC) and differential interference contrast (DIC)
microscopy have been used for several decades to infer morphometric
features of live cells without the need for exogenous contrast agents.
These techniques transfer the information encoded by the phase of the
imaging field into the intensity distribution of the final image.
Thus, the optical phase shift through a given sample can be regarded
as a powerful endogenous contrast agent, as it contains information
about both the thickness and refractive index of the sample. However,
both PC and DIC are<i> qualitative</i> in terms of optical path-length
measurement, i.e. the relationship between the irradiance and phase of
the image field is generally nonlinear.<i> Quantifying</i> the optical
phase shifts associated with biological structures gives access to
information about morphology and dynamics at the nanometer scale. Over
the past decade, the development of quantitative phase imaging
techniques has received increased scientific interest. At the MIT
Spectroscopy Laboratory, we have developed several interferometric
phase imaging techniques, which are characterized by sub-nanometer
optical path-length sensitivity over broad time scales, i.e.
milliseconds to days. These novel optical methods offer a fresh look
at basic cell biophysics, such as cell motility, cell growth and
membrane fluctuations. Furthermore, this type of investigation may
provide a better understanding of diseases such as malaria and sickle
cell anemia.</font></div>
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