Method and apparatus for the automatic recognition and evaluation of optical crack indications on the surface of workpieces

US4207593A · kind A · utility

Assignee

• Karl Deutsch Prüf—und Messgerätebau GmbH + Co KG · DE

Inventors

• Volker Deutsch · Wuppertal, DE
• Ernst Becker · Bensheim, DE
• Ulrich Forstermann · Sprockhövel, DE

Key dates

• Filing date: Jul 27, 1977
• Grant date: Jun 10, 1980
• Expiry date: Jul 27, 1997

Classification

• Technology area (CPC G): Physics
• CPC primary: G01N21/89
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

A method and device for the automatic detection and evaluation of optical crack indication on the surface of workpieces is disclosed. In such method and device, visual displays are converted into electrical bright-dark signals by the use of light sensitive device, for example, an image recording tube. The surface under observation is scanned by the light-sensitive device line by line, the width of each of which (either as individual line or groups of adjacent lines) corresponds to the maximum optical display width from which evaluation is to proceed. The bright-dark signals thus obtained from three lines or lines groups are compared. From the signal of the middle line or line group and the signals of the two other line or line groups there is formed a difference signal which is evaluated to generate an error evaluation signal of a minimum value is exceeded.