Multi-surface scattered radiation differentiation

摘要

An optical inspector includes a radiating source, a time varying beam reflector, a telecentric scan lens, a first and second waveplate, a polarizing beam splitter, a first detector, a focusing lens, a blocker, and a second detector. The radiating source irradiates the first waveplate generating circularly polarized source beam that irradiates a first position of on the time varying beam reflector with a source beam. The time varying beam reflector directs the source beam to the telecentric scan lens, which in turn directs the source beam to a sample. Reflected radiation from a sample is directed to the second waveplate generating linearly polarized beam that irradiates the polarizing beam splitter which directs a portion of the reflected radiation to the first detector. Scattered radiation from the sample is directed by the focusing lens to the second detector. Contemporaneous measurements by the first and second detectors are compared to differentiate.

主权项

1. An apparatus, comprising:
a time varying beam reflector; a radiating source that irradiates the time varying beam reflector at a first position; a first waveplate, wherein the first waveplate is positioned along a source radiation path between the radiating source and the time varying beam reflector; a telecentric scan lens that directs source radiation reflected by the time varying beam reflector onto a transparent sample and a stage, wherein the telecentric scan lens directs specular reflected radiation from the transparent sample to the time varying beam reflector at a second position symmetrically opposite the first position about a central axis of the telecentric scan lens, and wherein the irradiation of the transparent sample and the stage causes scattered radiation reflecting from the transparent sample and the stage; a beam splitter that receives specular reflected radiation from the time varying beam reflector; a second waveplate, wherein the second waveplate is positioned along a reflected radiation path between the time varying beam reflector and the beam splitter; a first detector that receives a first portion of the specular reflected radiation from the beam splitter; a focusing lens that receives the scattered radiation from the transparent sample; a blocker that redirects the scattered radiation from the stage away from the focusing lens, wherein the blocker is located between the focusing lens and an irradiated location on the stage; and a second detector located near the focal plane of the focusing lens, wherein a first surface of the transparent sample faces the telecentric scan lens, and wherein a second surface of the transparent sample does not face the telecentric scan lens.