The present invention discloses an overlay alignment measurement apparatus and method. The overlay target is periodic and is illuminated by coherent radiation; a Fourier transform lens optically computes the Fourier transform of the target. Analysis of the spatial frequencies at the Fourier plane yields overlay alignment information.

 
Web www.patentalert.com

< Optical scanning device and image forming apparatus

> Optical system and method for inferring a disturbance

> Beam combiner employing a wedge-shaped cross-section

~ 00578