  Micron-scale randomness during manufacturing can ensure anti-counterfeiting
labels are unclonable. However, this security typically comes at the expense of
complex hardware being needed for authentication (e.g., microscopy systems). We
demonstrate unclonable labels that can be authenticated using a standard
light-emitting diode and smartphone camera. The labels consist of a microlens
array laminated to a polymer film that is doped with luminescent
microparticles. The micron-scale random overlap of focal volumes and
microparticles leads to a pattern of bright points of visible light emission
that can be easily imaged by a smartphone camera. 10 000 comparisons of images
demonstrate that the labels can be robustly authenticated, and that the
probability of a false authentication is on the order of $10^{-15}$. The
ability for microlens arrays to simplify the hardware needed for authentication
of unclonable labels is generalizable, and attractive for the implementation of
unclonable labels in anti-counterfeiting systems.
