Patent ID: 7531794

Claim:
A method for preparing a thinned specimen by irradiating at least one of the side surfaces of the specimen with an ion beam to ion-etch the specimen, said method comprising the steps of: (a) directing the ion beam at the specimen, directing light at one side surface of the specimen, and imaging the other side surface of the specimen with an imaging device; (b) extracting high-brightness pixels which form the specimen image and which have intensities becoming greater than a given threshold value as the specimen is thinned; (c) making a decision as to whether the extracted high-brightness pixels form a continuous sequence of pixels whose number is in excess of a given number on the specimen image; and (d) stopping the ion-beam irradiation of the specimen or varying conditions under which the specimen is irradiated with the ion beam if the decision at the step (c) is affirmative (YES).