Study of diseased tissue and biological samples through a microscope can often be complicated by multiple layers of surrounding tissues. The resulting image may be too distorted to be of any value. Although there are modern microscopes that compensate for this using fluorescent ‘guide stars,’ this technique can be invasive and damaging of the specimen being studied.
To get around this issue, scientists at Weizmann Institute of Science in Rehovot have developed a new adaptive optics technique to focus laser light through dense tissue without the need for a guide star. The method can resolve a point less than a micron across.
“Imagine shining a flashlight through a thick fogbank to try to see a single dot,” said Prof. Yaron Silberberg, Principal Investigator of the Ultrafast Optics Group at Weizmann. “The light would become so scattered as it traveled through the fog that you wouldn’t be able to make out what was hidden inside. By carefully shaping the light going in, however, it would be possible to home in on your target. That is exactly what the researchers were able to achieve in a way no one has ever done before.”
The researchers incorporated a high-resolution wavefront shaping device to a standard two-photon scanning microscope that uses bursts of laser light to build a picture point-by-point and then line-by-line. The wavefront shaping device enables the microscope to peer through a visually opaque layer that would otherwise produce a blurred image.
“What we have discovered is that it’s possible to efficiently ‘pre-correct’ the laser beam using the nonlinear fluorescence signal,” said researcher Ori Katz. “The end result is that instead of having a distorted, blurred light source on the object to be imaged, we have a tightly focused, or in this case, refocused beam of light.”