Vision inspection system and method

• US 5,680,215 A
• Filed: 02/27/1995
• Issued: 10/21/1997
• Est. Priority Date: 02/27/1995
• Status: Expired due to Term

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: Lockheed Martin Space Operations Company (Martin Marietta Corporation)
• Inventors: Williams, Rick A., Huber, Edward D.
• Primary Examiner(s): Pham, Hoa Q.
• Application Number:
  US08/395,847
• Time in Patent Office: 967 Days
• Field of Search: 356/371, 356/237, 356/445, 356/446, 356/376, 356/237 G
• US Class Current: 356/600
• CPC Class Codes: G01B 11/306 for measuring evenness
• CPC Class Codes: G01N 2021/8472 Investigation of composite materials
• CPC Class Codes: G01N 21/88 Investigating the presence of flaws or contamination
• CPC Class Codes: G01N 21/8806 Specially adapted optical and illumination features

Abstract

An optical vision inspection system (4) and method for multiplexed illuminating, viewing, analyzing and recording a range of characteristically different kinds of defects, depressions, and ridges in a selected material surface (7) with first and second alternating optical subsystems (20, 21) illuminating and sensing successive frames of the same material surface patch. To detect the different kinds of surface features including abrupt as well as gradual surface variations, correspondingly different kinds of lighting are applied in time-multiplexed fashion to the common surface area patches under observation.

Claims

1. An optical system for inspecting characteristically different kinds of variations in a surface, said system comprising:

first and second optical subsystems for multiplexed illumination of a predetermined sequence of selected common portions of a material surface region under optical inspection sequenced in alternating succession;

said first optical subsystem providing diffuse illumination;

said second optical subsystem providing fringe illumination taking into account phase information;

an inspection subsystem for viewing common portions of material surface regions in connection with illumination by said first and second optical subsystems; and

a data processing system for processing optical inspection data from both said first and second optical subsystems;

wherein

said second optical subsystem comprises a module for performing ordered phase unwrapping, in which a raw phase map having many pixels is produced, and a quality metric is applied to each pixel in the raw phase map to rank pixels for an order in which they will be unwrapped.

2. The optical system according to claim 1, wherein said data processing system produces a consolidated data base summarizing multiple kinds of surface variations in a selected inspection surface which has been inspected by both said first and second optical subsystems.

3. The optical system according to claim 1, comprising a system for positioning said first and second optical subsystems with respect to common portions of a material surface to be visually inspected.

4. The optical system according to claim 1, comprising a system for carrying said first and second optical subsystems along a predetermined path on a material surface under visual inspection.

5. The optical system according to claim 4, comprising a system for conducting a raster illumination and detection scan of a selected material surface.

6. The optical system according to claim 1, wherein said data processing system compares current data from said first and second optical subsystems with earlier data as to corresponding inspected locations taken by said first and second optical subsystems.

7. The optical system according to claim 1, wherein said first optical subsystem includes a first illumination system for general illumination of a selected portion of a region under optical inspection.

8. The optical system according to claim 1, wherein said second optical subsystem includes a second illumination system for fringe line illumination of a selected portion of a region under optical inspection.

9. The optical system according to claim 1, wherein said first optical subsystem includes a first illumination system for general illumination of a selected portion of a region under optical inspection, and said second optical subsystem includes a second illumination system for fringe line illumination of a selected portion of a region under optical inspection.

10. The optical system according to claim 9, wherein said first illumination system is a diffuse illuminator.

11. The optical system according to claim 9, wherein said first illumination system includes a ring flash lamp.

12. The optical system according to claim 9, wherein said first illumination system includes an elliptical reflector.

13. An optical system for inspecting characteristically different kinds of variations in a surface including both gradual and abrupt surface variations, said system comprising:

first and second optical subsystems for multiplexed illumination and inspection of a predetermined sequence of selected common portions of a material surface region under optical inspection, said first optical subsystem illuminating a coincident area to highlight abrupt surface variations and said second optical subsystem including an illumination system which produces fringe lines taking into account phase information for highlighting gradual surface variations; and

a data processing system for processing optical inspection data from both said first and second optical subsystems;

wherein

second optical subsystem comprises a module for performing ordered phase unwrapping, in which a raw phase map having many pixels is produced, and a quality metric is applied to each pixel in the raw phase map to rank pixels for an order in which they will be unwrapped.

14. The optical system according to claim 13, comprising a video detection system which detects illuminated images highlighted by said first and second optical subsystems during successive illumination intervals.

15. The optical system according to claim 13, wherein said first and second optical subsystems are mounted on a common beam.

16. The optical system according to claim 15, wherein said first and second optical subsystems are laterally offset from each other with respect to common surface areas under alternating illumination.

17. The optical system according to claim 13, wherein said data processing system includes a data correlator for comparing observed surface features with a preestablished data base of surface features.

18. The optical system according to claim 13, said data processing system further comprising a parallel processing system for processing microdamage and macrodamage information to identify both microdamage and macrodamage features.

19. A method of inspecting a surface having macrodamage and microdamage features with a multimode illumination system highlighting microdamage features during one mode of illumination and highlighting macrodamage features in another mode of illumination and including an optical detection system for image detection of illuminated macrodamage and microdamage features, said method including the steps of:

projecting fringe illumination taking into account phase information onto a selected surface patch;

image detecting macrodamage features within the selected surface patch;

projecting diffuse illumination onto the selected surface patch; and

image detecting microdamage features within the selected surface patch;

wherein

said step of projecting fringe illumination is a single-set-of-fringe-lines process for measuring in three-dimensional coordinates the surface shape contours of the surface patch, said process comprising the substeps of;

placing the surface patch into the field of view of a projector assembly;

activating the projector assembly to project a single set of fringe lines on the surface patch to obtain a raw phase map giving a phase at each of a plurality of pixels corresponding to the surface patch;

unwrapping the phases using ordered phase unwrapping; and

converting the set of unwrapped phases onto a set of three-dimensional coordinates.

20. The method of claim 19 further comprising processing image detection data for micro- and macrofeatures to measure predetermined surface features.

21. The method of claim 20 including correlation of measured surface features with surface features of a pre-established data base of features.

22. The method of claim 19 wherein the projector assembly comprises:

a fringe line projector that illuminates the surface patch with a single set of fringe lines of sinusoidally varying intensity; and

a camera having a field of view that includes at least a portion of said surface patch illuminated by the fringe lines;

wherein

a single camera frame of data is entered into with a stationary transparent slide that contains said fringe lines, said slide being located within said projector, by means of commanding a computer that is coupled to the camera to sequentially process sets of pixels that are spatially separated from each other on said frame of camera data by specified amounts of phase shift.