AUTO FOCUS CONTROL APPARATUS, SEMICONDUCTOR INSPECTING APPARATUS AND MICROSCOPE

摘要

An auto focus control apparatus is provided to perform an auto focus adjustment using astigmatism without being affected by a pattern on a surface. A light receiving optical system includes an unpolarized beam splitter 420 separating a reflection light from an object into a first reflection light and a second reflection light, a first astigmatism producing means 430 arranged on an optical path of the first reflection light, a second astigmatism producing means 450 arranged on an optical path of the second reflection light, a first light detector 440 receiving a light passing through the first astigmatism producing means, and a second light detector 460 receiving a light passing through the second astigmatism producing means. The light source optical system 310 is arranged such that an image forming point of a focus error detecting light is defocused from an observation plane by a predetermined distance.

主权项

1. An auto focus control apparatus for controlling a relative position of a surface of an object with respect to an observation plane in order to inspect the surface of the object using an observation optical system including an image sensor, comprising:
a light source optical system including a light source which emits a focus error detecting light; a condenser lens condensing the focus error detecting light to an incident light to the surface of the object; a light receiving optical system receiving a reflection light from the object through the condenser lens; and a focus error signal generator generating a focus error signal using a receiving signal from the light receiving optical system, wherein the light receiving optical system comprises an unpolarized beam splitter separating the reflection light from the object into a first reflection light and a second reflection light; a first astigmatism producing means arranged on an optical path of the first reflection light; a second astigmatism producing means arranged on an optical path of the second reflection light; a first light detector receiving a light passing through the first astigmatism producing means; and a second light detector receiving a light passing through the second astigmatism producing means, wherein the focus error signal generator generates the focus error signal using the receiving signal from the first light detector and the second light detector, wherein the light source optical system is arranged such that an image forming point of the focus error detecting light is defocused from the observation plane by a predetermined distance, and wherein the light receiving optical system comprises an offset adjustment lens which adjusts such that the reflection light of the light defocused from the observation plane by the predetermined distance is focused on receiving surfaces of the first light detector and the second light detector.