Israeli scientists find way to see through frosted glass
By David Szondy
October 28, 2012
Taking a shower while secure in the knowledge that no one can see through the curtains may soon be a thing of the past. Researchers Ori Katz, Eran Small and Yaron Silberberg of the Weizmann Institute of Science, Rehovot, Israel, have developed a method for de-scattering light to form coherent images in real time. In other words, they have found a way to look through shower curtains, frosted glass and other image-blurring materials. The technique may one day aid scientists in seeing through living tissue or around corners.
Frosted glass, tissue and other materials aren’t opaque, but we can’t see through them because they scatter light so that that any image seen through them is hopelessly blurred. An ordinary lens isn’t any good because it just magnifies and focuses a blurry image that stays blurry. What’s needed is a way of de-scattering the light, which the Weizmann team achieves through the use of “wavefront shaping” technology. This allows them to not only re-create blurry images, but do so in three dimensions and in real time.
The technique involves taking the scattered light and passing it through a Spatial Light Modulator (SPL). This is may sound daunting, but an SPL is a common device found in overhead projectors for showing computer images. It works by modulating the phase and intensity of light. In wavefront shaping, the SPL takes the frosted glass or other light-scattering medium and uses the modulation to change it into a light-scattering lens with a known focal length. That is, instead of having one big fuzzy image, you get a lot of little focused fuzzy images. These little images interfere with one another to produce a “memory effect” that recreates the original image. This is then passed through a bandpass filter that removes unwanted optical wavelengths and enhances the image, which a lens can then focus.
This technology can not only make shower curtains transparent, it can also recreate in real time images reflected off of walls that would otherwise be invisible, so it can effectively “see” around corners.
The practical applications for this real-life x-ray vision are considerable. In aviation, the military and firefighting it can be used to see through fog and smoke. Doctors can use it to see through tissues, which is especially important for microscopy. Also, astronomers would benefit because de-scattering images would counteract the problems of trying to see clearly through atmospheric turbulence.
The downside of this technology is that it also works on frosted-glass bathroom windows and shower curtains. If it becomes generally available, expect to see a jump in sales for opaque shower curtains and bathroom window blinds.