Agora20120509--waves in complex media

Agora is a paper discussion session of our group.
This week, I will chair the discussion for the review paper of A. Mosk '

Controlling waves in space and time for imaging and focusing in complex media'. 

Based on the wave equation given above and Maxwell equations, if the material is non-absorbing and reciprocal, then the wave exhibit time reversal symmetry, due to this symmetry, a wave that propagating outwards can thus be back-propagated to the exact starting. 

It is due to the development of Spatial Light Modulator(SLM) that now one can control the field at optical frequency at a much simple and fast way, even for strongly scattering medium.  

Our Agora session of this month ended on May 23th, 2012. A summary of the discussion have been given in Agora_may2012. If people are interested in, you can have a look. 

Internship finished--Laser Speckle Contrast Analysis for Hemodynamics measurement

The internship is with a company on cardiology. The purpose is to build up a Laser speckle contrast imaging setup and algorithm in order to measure important parameters for blood flow, for instance, the heart rate and velocity.

An example of Laser Speckle pattern

A laser speckle is the coherence interference pattern of surface or material due to the local refractive index variation. Speckle sometimes is considered as noise for coherent optical imaging method like OCT. But actually, it contains much information about the material itself and the illuminating light. For example, the laser speckle contrast is modified by the periodic pulsed blood flow,  one can easily extract the heart rate info from the speckles.

Laser spot on a fingertip

Master Thesis--Extended Nijboer Zernike theory for imaging simulation of optical systems

I have successfully passed the master thesis on the topic 'Extended Nijboer Zernike theory'. A link to the abstract of this work can be found in the group's blog--Lei Wei Master thesis