Optical convex surface profiling and gauging apparatus and method therefor

• US 4,872,757 A
• Filed: 04/20/1988
• Issued: 10/10/1989
• Est. Priority Date: 04/20/1988
• Status: Expired due to Term

• Current Assignee: Ball Corporation
• Original Assignee: Ball Corporation
• Inventors: Cormack, Robert H., Brown, Carey S.
• Primary Examiner(s): Evans, F. L.
• Application Number:
  US07/183,763
• Time in Patent Office: 538 Days
• Field of Search: 356/376, 356/237, 356/426, 356/428, 382/8, 358/101, 358/106, 209/577, 209/585, 209/597, 209/598
• US Class Current: 356/612
• CPC Class Codes: G01B 11/2433 for measuring outlines by shadow casting
• CPC Class Codes: G01N 21/909 in opaque containers or opaque container parts, e.g. cans, tins, caps, labels

Abstract

The present invention utilizes back lighting optics to produce converging white light over an area larger than an area of the edge of the convex object being profiled by the present invention. Opposite the back lighting optics are located a shadow image detector which detects the shadow image of the edge of the convex object, which is located between the back lighting optics and the shadow image detector. The detector generates a plurality of pixel outputs from each of a plurality of vertical locations for the shadow image of the edge. A rotating stage provides relative movement between the convex object and the detector/optics arrangement. The output of the detector which is a high resolution camera is fed into a data processing system which determins a sub-pixel distance measurement for each of the plurality of vertical locations and arranges the sub-pixel distance measurements into rows and columns to construct a surface profile of the convex object.

Claims

1. An apparatus for displaying the surface profile of a convex object, said apparatus comprising:

means (40) for uniformly producing converging white light over an area larger than the area of an edge of said convex object being profiled,

means (50) opposite said producing means for detecting the shadow image (800) of said edge of said convex object as illuminated by said producing means, said converging white light being focused in said detecting means, said detecting means generating a plurality of pixel outputs for each of a plurality of vertical locations for said shadow image of said edge,

means (60) for providing movement between said object and said producing and detecting means to provide a plurality of shadow images onto said detecting means corresponding to different edges of said convex object,

means (20) connected to said detecting means and receptive of said plurality of pixel outputs for determining a sub-pixel distance measurement for each of said plurality of vertical locations, said determining means further being capable of arranging said sub-pixel distance measurements into rows of said surface profile corresponding to individual vertical measurements of said shadow image for one of said edges and into columns of said surface profile corresponding to said plurality of edges, and

means (30) connected to said determining means and receptive of said row and column measurements for displaying said surface profile.

2. The apparatus of claim 1 wherein said producing means comprises:

a light source (80) for generating white light,

an iris (100) containing a diffuser (102) receptive of said white light from said light source for uniformly diffusing said light, and

means (110) receptive of said diffused light for producing said converging white light over said area.

3. The apparatus of claim 1 wherein said detecting means comprises:

a cylindrical telescope (130) receptive of said shadow image from said edge of said object, said telescope having a field of view in the horizontal direction of said image at least one-half the field of view in the vertical direction, and

a camera (140) receptive of said shadow image through said cylindrical telescope for generating said plurality of pixel outputs.

4. The apparatus of claim 1, wherein said determining means comprises:

an interpolator (150) receptive of said plurality of pixel outputs for determining said sub-pixel distance measurement,

means (160) receptive of said sub-pixel distance measurements for assembling an X-Y surface profile of the distance measurements, and

means (170) receptive of said X-Y surface profile for spatially filtering said X-Y surface profile according to a predetermined convolution kernel in order to emphasize desired variation parameters.

5. The apparatus of claim 4 wherein said interpolator comprises means for determining the actual edge distance of said shadow image through linear interpolation between the two pixels immediately above and below the actual edge of the shadow.

6. An apparatus for displaying the surface profile of a convex object, said apparatus comprising:

means (40) for uniformly producing converging white light over an area larger than the area of an edge of said convex object being profiled,

means (50) opposite said producing means for detecting the shadow image (800) of said edge of said convex object as illuminated by said producing means, said converging white light being focused in said detecting means, said detecting means generating a plurality of pixel outputs for each of a plurality of vertical locations for said shadow image of said edge,

means in said detecting means for providing a field of view in the horizontal direction of said edge which is at least one-half the field of view along the vertical direction of said edge thereby magnifying dimensional variations in said edge,

means (60) for providing movement between said object and said producing and detecting means to provide a plurality of shadow images onto said detecting means corresponding to different edges of said convex object,

means (20) connected to said detecting means and receptive of said plurality of pixel outputs for determining a sub-pixel distance meaurement for each of said plurality of vertical locations, said determining means further being capable of arranging said sub-pixel distance measurements into rows of said surface profile corresponding to individual vertical measurements of said shadow image for one of said edges and into columns of said surface profile corresponding to said plurality of edges, and

means (30) connected to said determining means and receptive of said row and column measurements for displaying said surface profile.

7. An apparatus for displaying the surface profile of a convex object, said apparatus comprising:

means (40) for uniformly producing converging white light over an area larger than the area of an edge of said convex object being profiled,

means (50) opposite said producing means for detecting the shadow image (800) of said edge of said convex object as illuminated by said producing means, said converging white light being focused in said detecting means, said detecting means generating at least four pixel outputs for each of a plurality of vertical locations for said shadow image of said edge,

means in said detecting means for providing a field of view in the horizontal direction of said edge which is at least twice the field of view in the vertical direction of said edge thereby magnifying variations in said edge,

means (60) for providing movement between said object and said producing and detecting means to provide a plurality of shadow images onto said detecting means corresponding to different edges of said convex object,

means (20) connected to said detecting means and receptive of said plurality of pixel outputs for determining a sub-pixel distance measurement for each of said plurality of vertical locations, said determining means further being capable of arranging said sub-pixel distance measurements into rows of said surface profile corresponding to individual vertical measurements of said shadow image for one of said edges and into columns of said surface profile corresponding to said plurality of edges, and

means (30) connected to said determining means and receptive of said row and column measurements for displaying said surface profile.

8. An apparatus for displaying the severity of dents in the surface of a convex object according to a predetermined classification, said apparatus comprising:

means (40) for uniformly producing converging white light over an area larger than the area of an edge of said convex object being profiled,

means (50) opposite said producing means for detecting the shadow image (800) of said edge of said convex object as illuminated by said producing means, said converging white light being focused in said detecting means, said detecting means generating a plurality of pixel outputs for each of a plurality of vertical locations for said shadow image of said edge,

means (60) for providing movement between said object and said producing and detecting means to provide a plurality of shadow images onto said detecting means corresponding to different edges of said convex object,

means (20) connected to said detecting means and receptive of said plurality of pixel outputs for determining a sub-pixel distance measurement for each of said plurality of vertical locations, said determining means further being capable of classifying dents based upon said sub-pixel distance measurements into said predetermined classification, and

means (30) connected to said determining means and receptive of said classification of dents for displaying said severity of said dents according to said classification.

9. A method for displaying the surface profile of a convex object, said apparatus comprising:

uniformly converging white light over an area larger than the area of an edge of said convex object being profiled,

detecting the shadow image of the edge of said convex object as illuminated by said white light,

generating a plurality of pixel outputs for each of a plurality of vertical locations for said shadow image of said edge in response to the detection of the shadow image,

providing movement to the object to provide a plurality of shadow images corresponding to different edges of said convex object,

determining a sub-pixel distance measurement for each of said plurality of vertical locations,

arranging said sub-pixel distance measurements into rows of said surface profile corresponding to individual vertical measurements of said shadow image for one of said edges and into columns of said surface profile corresponding to said plurality of edges, and

displaying said surface profile.

10. A method for displaying the surface profile of a convex object, said apparatus comprising:

uniformly converging white light over an area larger than the area of an edge of said convex object being profiled,

detecting the shadow image of the edge of said convex object as illuminated by said white light,

generating a plurality of pixel outputs for each of a plurality of vertical locations for said shadow image of said edge in response to the detection of the shadow image,

providing a field of view in the horizontal direction of said edge which is at least one-half the field of view along the vertical direction of said edge thereby magnifying dimensional variations in said edge,

providing movement to the object in order to provide a plurality of shadow images corresponding to different edges of said convex object,

determining a sub-pixel distance measurement for each of said plurality of vertical locations,

arranging said sub-pixel distance measurements into rows of said surface profile corresponding to individual vertical measurements of said shadow image for one of said edges and into columns of said surface profile corresponding to said plurality of edges, and

displaying said surface profile.

11. A method for displaying the surface profile of a convex object, said apparatus comprising:

uniformly converging white light over an area larger than the area of an edge of said convex object being profiled,

detecting the shadow image of said edge of said convex object as illuminated by said white light,

generating at least four pixel outputs for each of a plurality of vertical locations for said shadow image of said edge,

providing a field of view in the horizontal direction of said edge which is at least one-half the field of view in the vertical direction of said edge thereby magnifying variations in said edge,

providing movement to the object to provide a plurality of shadow images onto said detecting means corresponding to different edges of said convex object,

determining a sub-pixel distance measurement for each of said plurality of vertical locations,

arranging said sub-pixel distance measurements into rows of said surface profile corresponding to individual vertical measurements of said shadow image for one of said edges and into columns of said surface profile corresponding to said plurality of edges, and

displaying said surface profile.

12. A method for displaying the severity of dents in the surface of a convex object according to a predetermined classification, said apparatus comprising:

uniformly converging white light over an area larger than the area of an edge of said convex object being profiled,

detecting the shadow image of said edge of the convex object,

generating a plurality of pixel outputs for each of a plurality of vertical locations for said shadow image of said edge,

providing movement to said object to provide a plurality of shadow images corresponding to different edges of said convex object,

determining a sub-pixel distance measurement for each of said plurality of vertical locations,

classifying dents based upon said sub-pixel distance measurements into said predetermined classification, and

displaying said severity of said dents according to said classification.