A Rochester Cloak is a cloaking device which can be built using inexpensive, everyday materials. John Howell, a professor of physics at the University of Rochester, and graduate student Joseph Choi developed the device, which features four standard lenses that allows an object to appear invisible as the viewer moves several degrees away from the optimal viewing positions.
Rochester Cloak Wikipedia
The cloaked region is a cylindrical [annular] region between the first and last lenses.
For a shorter 3 lens symmetric cloak the middle lens can be diverging to give a '3D triangular-ring' cloaked region be- tween the first and last lenses.
The scientists at University of Rochester provided steps to make this cloaking device. These 4 steps are required to be followed:
1.Purchase 2 sets of 2 lenses with different focal lengths f1 and f2 (4 lenses total, 2 with f1 focal length, and 2 with f2 focal length).
2.Separate the first 2 lenses by the sum of their focal lengths (So f1 lens is the first lens, f2 is the 2nd lens, and they are separated by t1= f1+ f2).
3.Do the same in Step 2 for the other two lenses.
4.Separate the two sets by t2=2 f2 (f1+ f2) / (f1-- f2) apart, so that the two f2 lenses are t2 apart.
The Rochester Cloak was referenced in the NBC show "The Blacklist: Redemption". In this episode, a version of the Rochester Cloak was used to make the contents of a truck invisible.