A Ronchi Ruling, also called a Ronchi grating is a constant-interval bar and space square wave optical target that has a high edge definition and contrast ratio. Ronchi rulings are commonly manufactured through photolithographic deposition of chrome on glass or optical substrates. Ronchi rulings are used for optical testing purposes, e.g. the Ronchi test.
The Ronchi ruling is named after the Italian physicist Vasco Ronchi (1897-1988) 1.