uOttawa photonics researchers give coins and medal a surprising pulsating effect for a good cause
Using tiny mirrors to create a unique illusion in a silver coin is yet another example of how photonics – the science and technology of light – applies in so many diverse ways in our lives.
Researchers at the Centre for Research in Photonics at the University of Ottawa developed a surface mirror technology that, when integrated on coins, produces a pulsating effect. In collaboration with the Royal Canadian Mint, this new technology was used to design a Pulsating Maple Leaf coin and a COVID-19 recognition medal.
When you tilt the coin or the medal, the maple leaf and the heart appear to expand and contract, giving the impression that it’s pulsating.
“I was inspired by the "eye shine effect," commonly observed when photographing animals at night, as well as reflectors on bicycles,” said Dr. Jaspreet Walia, post-doctoral fellow in the Department of Physics at the University of Ottawa.
“The structures used on the coins are effectively modified reflectors which control how light enters the eye.”
Dr. Walia was primarily responsible for the development of the micromirror technology, under the supervision of Full Professor Arnaud Weck and Distinguished Professor and University Research Chair in Surface Plasmon Photonics, Pierre Berini, who is also the Director of the Centre for Research in Photonics at the University of Ottawa.
According to Dr. Walia, unlike banknotes, observing an optical effect on a coin is not very common.
“The main hurdles in this connection are keeping costs low while still maintaining the ability to mass produce the optical effect on the surface of a metal part,” he noted.
Through this research collaboration, the University of Ottawa and the Royal Canadian Mint were able to realize such a technology that is easily integrated into the traditional minting process.
It resulted in four different products: the pulsating maple leaf, the V-Day coin, the 2021 Maple Leaf Fractional Set, and the COVID-19 recognition medal.
“The research involved computer modelling and optical simulations to understand the physics of various micromirror arrangements,” explained Dr. Jaspreet Walia. “Once promising sets of structures were identified, prototype samples were machined using CNC milling and laser micromachining to confirm a visually pleasing optical effect had been achieved.”
The project was conducted over a year, from May 2018 to May 2019, and required resources and tools available at uOttawa and at the Mint. The project was funded by Mitacs and the Royal Canadian Mint.
The first pulsating maple leaf coins were released in September 2019 and have since sold out. The Recognition medal is available here.
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