Video surface inspection system

• US 4,675,730 A
• Filed: 09/06/1985
• Issued: 06/23/1987
• Est. Priority Date: 09/06/1985
• Status: Expired due to Term

• Current Assignee: Alcoa Incorporated (Howmet Aerospace, Inc.)
• Original Assignee: Aluminum Company of America (Howmet Aerospace, Inc.)
• Inventors: Adomaitis, Paul R., Hobi, Bernard J., Brouwer, Nicholaas L.
• Primary Examiner(s): Britton, Howard W.
• Application Number:
  US06/773,065
• Time in Patent Office: 655 Days
• Field of Search: 358/106, 358/93, 358/101, 340/675
• US Class Current: 348/131
• CPC Class Codes: G01N 2021/889 providing a bare video image, i.e. without visual measurement aids
• CPC Class Codes: G01N 21/8903 using a multiple detector array

Abstract

The invention comprises a system for continuously inspecting the surface of a moving object for defects therein while illuminating the surface of the moving object with both specular and/or diffused light of selected wavelengths, automatically detecting the presence of a defect, and automatically transmitting a visual image of a defect, when detected, to a storage vehicle capable of subsequent permanent display and electronic characterization of the visual image containing the defect.

Claims

1. A method of continuously and automatically monitoring broad surfaces of a rapidly moving metal material for the detection and analysis of surface variations which exceed established acceptable surface conditions for the purpose of determining the occurrence of surface defects that are considered rejectionable and for providing accurate defect classification of the same, comprising:

homogeneously exposing the moving surface to visible and/or invisible specular and diffused electromagnetic radiation in a selected range of wavelengths to enhance surface features and thereby aid detection of surface defects,

rendering the rapidly moving surface momentarily motionless,

detecting the presence of one or more rejectionable defects with a plurality of sensors located to view the entire width of the material,

transmitting an electronic image of the area containing a defect from one or more of the sensors to a device for storing the image for subsequent display and analysis, the image containing grey scale levels that represent varying intensities of electromagnetic energy reflected by the defect,

providing a range of grey scale levels that represent the range of intensities of electromagnetic energy reflected from a surface that is free of rejectionable defects,

comparing the grey scale levels of the image with the defect with the range of grey scale levels that represent a surface free of rejectionable defects, and

viewing and analyzing only those images of the surfaces on a freeze frame monitor that have grey scale levels outside the grey scale range of intensities that indicate a surface free from rejectionable defects.

2. The method of claim 1 including the steps of:

directing the specular light from a position above the moving surface while the diffused radiation is directed in a direction substantially parallel to the surface,

with both types of radiation being positioned to homogeneously cover the entire width of the surface.

3. A method of continuously and automatically monitoring broad surfaces of rapidly moving metal material for the detection and analysis of surface variations which exceed established acceptable surface conditions for the purpose of determining the occurrence of surface defects that are considered rejectionable and for providing accurate defect definition and classification of the same, comprising:

homogeneously exposing the moving surface to invisible and/or visible specular and diffused electromagnetic radiation in a selected range of wavelengths to enhance surface features and thereby aid detection,

rendering the moving surface momentarily motionless,

capturing images of one or more rejectionable defects on the moving surface across the width thereof at a rate of sixty per second, or multiples thereof, for a distance of one foot of the surface in the direction of travel at a speed of 1800 feet per minute, or multiples thereof, using side-by-side video cameras employing the NTSC standard of 512 scan lines per frame,

transmitting an electronic image of the area containing a defect from one or more of the cameras to a device for storing the image for subsequent display and analysis, the image containing grey scale levels representing the intensities of energy reflected by the defect,

providing a range of grey scale levels that represents the range of intensities of electromagnetic energy reflected from a surface that is free of rejectionable defects,

comparing the grey scale levels of the image with the defect with the range of grey scale levels that represent a surface free of rejectionable defects, and

viewing and analyzing only those images of the surfaces on a freeze frame monitor that have grey scale levels outside the grey scale range of intensities that indicate a surface free from rejectionable defects.