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:
Jul. 04, 1989
Filed:
Jan. 27, 1988
Lionel R Baker, Oprington, GB;
Sira Limited, Chislehurst, GB;
Abstract
Apparatus for comparing a test surface 23 with a reference surface 8 comprising detector means 16.17, a test channel TC for receiving radiation from the test surface 23 and a reference channel RC for receiving radiation from the reference surface 8. A selector means 12 is provided to pass radiation from the test channel means TC and the reference channel means RC to the detector means. Varying means 5 is provided to vary the radiation passed along the test channel TC and reference channel RC. Cycle means is provided to cycle the selector means 12 between a first state in which more radiation from the test channel TC than the reference channel RC is passed to the detector means and vice versa. Control means is provided to control the radiation varying means 5 to provide a zero or minimum variation of radiation received by the detector means as the selector means 12 is cycled.