Inspection method and apparatus
AssigneeNikon Corporation
InventorKouji Yoshida
Life of this patent
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Abstract
A statistical processing unit compares the gray levels at identical positions in raw and reference images using a raw image having three or more gray levels obtained by sensing an object by an image pick-up unit. As the reference image, a predetermined designed image or at least one shift image obtained by shifting the raw image by an integer multiple of the repetition period in the repetition direction of a specific pattern is used. The statistical processing unit statistically analyzes the occurrence state of the difference between the raw and reference images, thus accurately obtaining the formation state of repetitive patterns on the object.
Claims38
An inspection method for inspecting an object on which a specific pattern is periodically and repetitively formed along a predetermined direction, comprising:
- picking-up an image of said object using not less than three gray levels;
- and
- obtaining formation information of said specific pattern by statistically analyzing a difference between a raw image obtained as an image pick-up result in said image picking-up, and a reference image.
An inspection apparatus which inspects an object on which a specific pattern is periodically and repetitively formed along a predetermined direction, comprising:
- an image pick-up unit which pick up an image of said object using not less than three gray levels;
- and
- a statistical processing unit which obtains formation information of the specific pattern by statistically analyzing a difference between a raw image which is obtained as an image sensing result obtained by using said image pick-up unit, and a reference image.
Dependencies are inferred from the claim text.