ベストフォーカスの検出方法

Detecting method of best focus

Abstract

(57)【要約】 【目的】 観測対象物の表面状態に影響を受けにくく、 専用の装置が不要なベストフォーカスの検出方法を提供 する。 【構成】 レンズの光軸上に配置された観測対象物の、 ある直線に沿った光強度分布を得る工程と、前記光強度 分布を微分して、微分光強度分布を求める工程と、前記 微分光強度分布の前記ある直線に沿った自己相関関数を 求める工程と、前記レンズと前記観測対象物との相対距 離を変化させて、前記光強度分布を得る工程から前記自 己相関関数を求める工程までを繰り返す工程とを含む。
PURPOSE: To provide a method of detecting a best focus which is hardly affected by the surface state of an observation object and dispenses with a dedicated device. CONSTITUTION: This method comprises a first process where the distribution of light intensity of an observation object disposed on the optical axis of a lens is measured along a certain rectilinear line, a second process where the distribution of light intensity is differentiated to obtain a differentiated distribution of light intensity, a third process where the autocorrelation function of the differentiated distribution of light intensity along a certain rectilinear line is obtained, and a fourth process where the first process to the third process are repeatedly carried out changing a relative distance between a lens and the observation object. COPYRIGHT: (C)1996,JPO

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    US-7060986-B2June 13, 2006Jeol Ltd.Automated method of correcting aberrations in electron beam, method of visualizing aberrations, and automated aberration corrector
    US-8571300-B2October 29, 2013Canon Kabushiki KaishaFocus finding and alignment using a split linear mask