Optical apparatus and focus correction method

Abstract

An optical apparatus according to the present embodiment includes a detector for detecting detection light of illumination light reflected by a sample, an optical system for illuminating the sample with the illumination light and guiding the detection light reflected by the sample to the detector, a displacement measurement unit for measuring a displacement drift indicating the amount of drift in the position of an optical element included in the optical system, a storage unit for storing the correlation between the displacement drift and a focus drift indicating the amount of drift in the distance between the sample and the optical system when the detection light detected by the detector is brought into focus, and a prediction unit for predicting a focus drift from the measured displacement drift by using the correlation.

Dependencies are inferred from the claim text.