Patent ID: 7911607

Claim:
A light measuring device for measuring light from a planar object, comprising: a spatial division device configured to receive in succession light emanating from different portions of the planar object; an optical condensing device positioned optically downstream of the spatial division device and configured to condense the light from the different portions of the planar object received by the operation of said spatial division device; and a detector positioned optically downstream of the optical condensing device and configured to receive the light condensed by said optical condensing device and output a signal corresponding to the received light, wherein said optical condensing device includes: a first iris member having formed therein a first aperture which transmits the light from any of the different portions of the plane light source therethrough while defining a first cross section of the light; a second iris member having formed therein a second aperture which has an aperture area smaller than that of the first aperture and transmits the light transmitted through said first iris member therethrough while defining a second cross section of the light; and a condensing optical element configured to condense the light transmitted through said second iris member onto a light receiving face of said detector.