Autofocus device and autofocusing method for an imaging device

摘要

An autofocus device for an imaging device is provided, which has an imaging optic having a first focal plane and an object table for moving an object to be imaged relative to the first focal plane, wherein said autofocus device comprises a) an image recording module having a second focal plane, the location thereof relative to the first focal plane being known, b) a lighting module (BM) for imaging a focusing image along a lighting beam path in a focusing image plane such that, if the object is positioned in a target position at a predetermined distance to the second focal plane, the lighting beam path is folded because of reflection on the object and the focusing image, which lies in the focusing image plane, intersects the second focal plane or lies therein, and c) a control module, which activates the object table to focus the imaging device so that the object is positioned in the target position, from a signal of the image recording module, which the image recording module generates on the basis of the recording thereof of the focusing image when the object is positioned in the target position, derives the deviation of the object position from the target position, and, based on the derived deviation, the predetermined distance, and the relative location of the first and second focal planes, activates the object table so that the object is positioned in the first focal plane.

主权项

1. An autofocus device for an imaging device, comprising an imaging optic having a first focal plane and further comprising an object table for moving a to-be-imaged object relative to said first focal plane,
wherein said autofocus device includes
an image capture module having a second focal plane whose position relative to said first focal plane is known,an illumination module for projecting a focal plane along an illuminating beam path into a focusing image plane in such a way that when the object is positioned in a target position at a predetermined distance from said second focal plane, said illuminating beam path is folded by reflection from said object and a focusing image lying in said focusing image plane intersects said second focal plane at a predetermined position of the focusing image, anda control module, which, to focus said imaging device,
actuates said object table so that said object is positioned in the target position,derives the deviation of the object position from the target position from a signal of said image capture module which said image capture module generates on the basis of its captured image of said focusing image when said object is positioned in the target position, and,based on the derived deviation, the predetermined distance and the relative positions of said first and second focal planes, actuates said object table so that said object is positioned in said first focal plane; and wherein said focusing image contains a plurality of subimages that are periodically intensity-modulated in a first direction and have the same period, said subimages being mutually phase-shifted.