Patent ID: 6201628
Filing Date: 2001-03-13
Classification: G01J,G06K

Abstract:
A constant pathlength optical train for coupling light to a substrate and for coupling scattered or emitted light from the substrate to a photodetector, comprising:a light source for providing a light beam;a scanning mirror assembly positioned to receive said light beam from said light source and sweep it across a steering mirror;the steering mirror having a radius of curvature equal to the distance between the scanning mirror and the steering mirror, positioned to receive said light beam from said scanning mirror assembly and reflect it to the substrate, whereby it is swept across the substrate along a scan arc;a means for collecting scattered or emitted light from the substrate and directing said scattered or emitted light to a photodetector, said emitted or scattered light possessing a substantially constant optical pathlength from excitation spot on said substrate to the photodetector;the photodetector positioned to receive emitted or scattered light from said means for collecting scattered or emitted light;said optical train being constructed and arranged such that a substantially constant optical pathlength from light source to the photodetector is maintained throughout the sweep of said beam across the substrate.