Sensor position independent material property determination using radiant energy

US4276480A · kind A · utility

Assignee

• Accuray Incorporated · US

Inventor

• Robert M. Watson · Seattle, US

Key dates

• Filing date: Sep 28, 1979
• Grant date: Jun 30, 1981
• Expiry date: Sep 28, 1999

Classification

• Technology area (CPC G): Physics
• CPC primary: G01B2210/46
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

A radiant energy method and apparatus is used to determine a property such as thickness or weight per unit area of a material (14 or 40 or 170 or 238), e.g., a sheet, that is located or moving generally in a predetermined spatial relation to a first reference position (16a or 40a or 56a). A second reference position (22, 56 or 230) is defined. A sensor means (18 or 44; or 102, 112, 106 and 108; or 150, 154 and 158; or 214 and 216; or 236, 242 and 244) responds to a condition of the material. The relation of the sensor response to the material property is susceptible to change with changes in the distance relationship of the sensor means and one of the reference positions or the material. There is produced a distance response (26 or D.sub.2 (x) or 110 and 110 ' or .tau..sub.1 and .tau.'.sub.1 or D.sub.2 (.tau.) or D.sub.2 or 236, 236' or 258, 258') to changes in the distance from the sensor means to one of the reference positions. The distance response is systematically related (e.g., by a computer 32 or 76 or 124 or 126 and 128) to the sensor response so as to produce a material property response (34 or t(x) or S+.DELTA.S or S+.DELTA..sub.1 S+.DELTA..sub.2 S) with substantially dec…