Hidden-mark observing apparatus and hidden-mark observable lens-meter

摘要

A progressive power lens (L) is illuminated with a collimated light beam through an illuminating optical system (2) comprising an LED (5), a pinhole plate (6), and a collimator lens (7). The shadow of the hidden mark of the progressive power lens (L) is projected onto a screen (4) by the light beam transmitted through the progressive power lens (L).