Patent ID: 7289233

Claim:
An optical film measuring device for measuring properties of a film of a measurement target at a predetermined film measurement position in an observation area, comprising: a light source for emitting white light or multi-color light; a light-projection optical system for projecting a light emitted from the light source to the observation area in the form of parallel light; a photo-detector of a region-divided type in which a plurality of detection cells for receiving the light from the observation area are collected in a two-dimensional space; an image-formation optical system for forming an image of light reflected by the measurement target in the observation area onto the photo-detector, said light being the light projected by the light-projection optical system; a spectroscopic part that can make only light in a predetermined wavelength band incident upon the photo-detector and selectively switch the wavelength band; and a signal processing portion for extracting a pattern registered beforehand from the image of the measurement target taken in by the photo-detector, defining a predetermined position in this pattern as the film measurement position, obtaining a plurality of images having different wavelengths selectively switched by the spectroscopic part with respect to the measurement target, and thereby measuring the properties of the film of the measurement target at a predetermined film measurement position based on the signals of the detection cells corresponding to the film measurement position of each of the plurality of images, wherein the signal processing portion obtains images having different wavelengths selectively switched by the spectroscopic part with respect to the measurement target and determines the film measurement position with the image in which a contrast of an image becomes highest among the plurality of images obtained.