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:
May. 17, 1988
Filed:
Apr. 11, 1986
Hitachi, Ltd., Tokyo, JP;
Abstract
An apparatus for measuring a difference in level in a sample comprises a light source section which provides illumination light of a variable-wavelength. The illumination light is irradiated onto the sample. A group of filters is provided for shielding diffraction light rays of O-order or other than O-order of the light reflected from the sample. The intensity of interference light of the light rays not shielded by the filter group is detected by a light detector which in turn converts it into an electric signal. An arithmetic operation unit receives the electric signal while the wavelength of the illumination light from the light source section is continuously varied. In the arithmetic unit, wavelengths at which the electric signal or detected light intensity takes extreme values are determined, and the level difference in the sample is determined on the basis of those wavelengths.