The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Apr. 05, 1983
Filed:
Sep. 05, 1980
U.S. Philips Corporation, New York, NY (US);
Abstract
In a scanning electron microscope, a periodic structure in the object plane is used for the detection of the focus condition of a spot-focussed electron beam scanning an object in order to correct defocusing and astigmatism in the scanning electron beam spot. To achieve this the detector comprises a plurality of individual elements which can be pair-wise read and an electronic circuit for forming a control signal for controlling the excitation of a spot-forming lens and a stigmator, respectively, from signals representing movement of the electron interference pattern at the detector, relative to the object scan, due to an out of focus condition. The signals are derived from corresponding pairs of detector elements which are situated at a fixed distance from each other in order to correct the focus and compensate for the astigmatism in the electron beam respectively. In the case of astimatism, signals from at least two pairs of detector elements spaced in directions at right-angles to one another, are used.