Monday, May 07, 2018
Interesting development
Arirang reports an early-stage experiment by Korean researchers. The Center for Molecular Spectroscopy is working on ways to image internal organs with ordinary light, not X-rays or magnetic waves. They have succeeded in looking through a mouse's skull.
This latest research isn't available online yet, but an earlier paper describes the technique. It's a variation of beamforming.
Visible light, even coherent laser light, doesn't work well for imaging because tissue scatters the light. Higher frequency X-rays can penetrate better because the waves are smaller than the atoms. But the higher frequency brings with it higher energy, which can push atoms around and cause tissue damage.
These Koreans have found a trick that basically tunes in the part of the light that enters and reflects in a straight line without scattering. The trick depends on a tiny grid with even tinier pixels.
Start with a visible laser. Pass the laser light through a beam splitter. One part goes directly to half of the pixels in the grid, evenly distributed. The other split part is phase-shifted. This phase-shifted beam goes to the other half of the pixels. The output is something like a checkerboard, except that the red and black squares are different phases instead of different colors.
The neighboring pixels are small enough that they interfere with each other as they pass into the target. By changing the phase of the 'black squares', it's possible to find an interference pattern that reflects from the target more than it scatters.
¶ 1:10 AM 
