Patent ID: 7894062

Claim:
An overlay measuring apparatus, comprising: a light source which generates visible light with a plurality of wavelengths; an optical module which selects visible light with a single wavelength from the visible light generated by the light source, makes the visible light with a single wavelength incident on a plurality of overlay patterns, and uses visible light reflected from the plurality of overlay patterns to project the overlay patterns with a predetermined color; an imaging unit which acquires images of the plurality of overlay patterns according to individual wavelengths of the visible light and acquires image signals corresponding to the images; a database which sequentially stores the image signals acquired by the imaging unit; a selection unit which selects a clear image from the overlay pattern images using the image signals stored in the database; and a control unit which outputs a control signal to the optical module so that the optical module projects the overlay pattern with a specific color using information associated with the individual wavelengths of the visible light that is used to project the overlay pattern image selected by the selection unit.