You only need 4 lenses and some patience to recreate the University of Rochester’s invisibility cloak
Whether you’re a science fan, Harry Potter fanatic, or a little bit of both, chances are you’ve heard of Rochester University’s real-life invisibility cloak, unveiled earlier this year. The university’s project details suggest that you can create your own cloak at home, using materials that total less than $100.
The Rochester Cloak uses 4 lenses to bend light around objects, meaning that viewers can see past an item rather than look directly at it. The lenses, which have different focal lengths, focus light on a point behind the interrupting object.
Business Insider outlines instructions for setting up the lenses at home, at their correct distances:
Obtain two sets of two lenses with different focal lengths. The first set will have one focal length while the other set will have a different focal length. You will have four lenses in total, which should cost you no more than $30. The lens provider will include the focal length information (sometimes denoted as FL) so you don’t have to calculate it yourself.
2. Using an optics bench, select one lens with the first focal length and a second lens with the second focal length. Separate them by a distance that is the sum of their focal lengths. For example, if your first lens has a focal length of 5 inches and your second lens has a focal length of 3 inches, then separate these lenses by 5+3 = 8 inches.
3. Now, do the same with your remaining two lenses.
4. Lastly, you need to know how far apart to separate your two sets. This will take a little math, but here’s an example using the same measurements in Step 2: D=[2 (3) (5+ 3) ]/ (5— 3) = 12 inches should be the distance between your two lenses with the focal length of 3 inches.
University of Rochester’s original diagram illustrates focal length formulas:
Rochester’s discovery comes at a time of increased research into invisibility and light distortion. Duke University produced a cloaking technology that attains similar effects by splitting light wavelengths. However, the Rochester Cloak is the first to demonstrate multidirectional invisibility, meaning that objects are hidden even when viewed from from a slight angle (from below, above, etc.). Currently, “invisibility” is limited to a 15 degree radius from each angle; further research into lens technology may widen this scope.