Scattered light measurement system

摘要

An optical collection and detection system for use in a surface inspection system for inspecting a surface of a workpiece. The surface inspection system has an incident beam projected through a back quartersphere and toward a desired location on the surface, which is a scanned spot having a known scanned spot size. The incident beam impinges on the surface to create scattered light that is collected by a collector module. The collector module includes collection optics for collecting and focusing the scattered light to form focused scattered light. A collector output slit is positioned at an output of the collector module, through which the collection optics focus the scattered light. The scattered light that is associated with the scanned spot forms an imaged spot at the collector output slit. The collector output slit has a width that is selected to be proportional to the scanned spot size, so as to allow passage of the focused scattered light associated with the scanned spot, and exclude the focused scattered light associated with the workpiece regions other than the desired spot. A collector output varying subsystem varies the collector output slit so as to at least one of minimize passage of Rayleigh light scatter through the collector output slit or optimize a signal to air-scatter-noise ratio.

主权项

1. An optical collection and detection system for use in a surface inspection system for inspecting a surface of a workpiece, the surface inspection system having an incident beam projected through a back quartersphere and toward a desired location on the surface comprising an scanned spot having a known scanned spot size, the incident beam impinging on the surface to create scattered light that is collected by a collector module, the collector module comprising:
collection optics for collecting and focusing the scattered light to form focused scattered light; a collector output slit positioned at an output of the collector module and through which the collection optics focus the scattered light, with scattered light associated with the scanned spot forming an imaged spot at the collector output slit; the collector output slit having a width that is selected to be proportional to the scanned spot size to allow passage of the focused scattered light associated with the scanned spot but to exclude the focused scattered light associated with the workpiece regions other than the desired spot; at least one of the collector output slit width and side-to-side position disposed so as to minimize passage of Rayleigh light scatter through the collector output slit.