Right, so, here’s a question for the nomenclaturally aware mechanical engineers in the audience. Last weekend, I was exposed to two equally awesome objects that include radially-opening apertures that I call “irises.” The first, to left, is Alan Rorie’s Aperture Lamp, which includes an adjustable opening to control the amount of light it emits. The second, to right, is Christopher Schaie’s brass peephole cover. Note the significant difference between these two mechanisms: Alan’s has thin leaves that overlap, Christopher’s has thicker leaves that do not overlap. Now here’s my question: Are there distinct names for these two mechanisms? And if so, what are they?