Method and apparatus for non-contact measuring of object surfaces

US5135308A · kind A · utility

Assignee

• Carl Zeiss Stiftung · DE

Inventor

• Michael Kuchel · Oberkochen, DE

Key dates

• Filing date: Mar 8, 1991
• Grant date: Aug 4, 1992
• Expiry date: Mar 8, 2011

Classification

• Technology area (CPC G): Physics
• CPC primary: G06T7/521
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

Two bar patterns are projected sequentially on the object (O) to be measured, e.g., by time-division multiplexing, at angles which are inclined toward each other. The bar patterns are produced by projectors having respective rectangular gratings. The periods of the gratings are the same, and the phase relationship of the gratings is fixed relative to each other. Each reflected bar pattern, as distorted by the surface of the object, is individually and sequentially recorded by a camera (K); and the bar phases (.psi..sub.1, .psi..sub.2) of each sequentially reflected bar pattern are calculated for each image point by a computer connected with the camera. The computer also computes the differences (.DELTA..psi.) between the bar phases of the two projections for each image point. These phase differences remain stationary even when the bar patterns are moved relative to the camera. A plurality of phase differences for each image point is stored, averaged, and then used to calculate the height measurement (z) for each image point for display on a television monitor (42).