Telecentric, parfocal, multiple magnification optical system for videoinspection apparatus

摘要

An objective lens is secured in an afocal mode to a support for movement vertically toward and away from a workpiece. An illumination collimator fixed on the support above the objective lens projects the image of a reticle downwardly and successively through a second lens assembly, a beamsplitter plate, and coaxially of the objective lens to the workpiece. A combined image of the reticle and workpiece is then projected by the objective lens upwardly onto the beamsplitter, and laterally to a mirror which projects the combined image upwardly along an axis spaced from and parallel to the axis of the objective lens, and through one of several different magnifying lens assemblies to the image detector of a video camera. The magnifying lens assemblies can be selectively indexed one at a time into registry with the camera, and each has a telecentric opening or stop which always registers with the rear focal point of the objective lens each time such assembly is indexed into its operative position.