Method and apparatus for optically evaluating the conformance of unknown objects to predetermined characteristics

• US 5,078,501 A
• Filed: 02/05/1990
• Issued: 01/07/1992
• Est. Priority Date: 10/17/1986
• Status: Expired due to Fees

• Current Assignee: E. I. du Pont de Nemours and Company (Corteva, Inc.)
• Original Assignee: E. I. du Pont de Nemours and Company (Corteva, Inc.)
• Inventors: Buck, Robert D., Hekker, Roeland M. T., Livny, Izhak M., Haran, Terence M.
• Primary Examiner(s): Arnold, Bruce Y.
• Assistant Examiner(s): Lerner, Martin
• Application Number:
  US07/476,130
• Time in Patent Office: 701 Days
• Field of Search: 364/822, 350/162.12, 350/162.13, 350/162.14, 382/2, 382/4, 382/31, 382/39, 382/50, 250/550
• US Class Current: 359/561
• CPC Class Codes: G01B 11/24 for measuring contours or curvatures
• CPC Class Codes: G01N 21/95623 using a spatial filtering method per se G02B
• CPC Class Codes: G02B 27/46 Systems using spatial filters
• CPC Class Codes: G06E 3/005 using electro-optical or opto-electronic means
• CPC Class Codes: G06V 10/88 Image or video recognition using optical means, e.g. reference filters, holographic masks, frequency domain filters or spatial domain filters

Abstract

The conformance of an unknown object to predetermined characteristics is evaluated through a characteristic signature, using its transform image. The presence at an inspection station of each successive one of the objects to be inspected is detected. The inspection system includes a rotatable disk having mask apertures that move into the line of sight of a light detector. Signals produced by scanning of timing marks upon the disk reflect which one of the plurality of masks is present in the optical path, and the photodetector determines the intensity of the transform image sampled by said mask means. The signals representing these intensities, correlated to the domain from which they emanate, are collected to form a signature for the object. This signature is compared to a known signature.

Claims

1. A method for optically evaluating the conformance of an unknown object to a standard comprising the steps of:

a) generating a plurality of optical transform images of a corresponding plurality of samples of a known object;

b) sampling light from different angular and radial components of the spatial domains of the plurality of transform images of the corresponding plurality of samples of the known object and generating electrical signal data representative of the different domains thereof independent of any electrical signal generated in response to the detection of the real image of the plurality of samples of the known object;

c) collecting the electrical signal data representing the different angular and radial components of the spatial domains of the plurality of transform images of the corresponding plurality of samples of the known object and collectively defining and storing a composite electric signature vector representing the transform images of the plurality of samples of the known object;

d) generating an optical transform image of an unknown object;

e) sampling light from different angular and radial components of the spatial domains of the transform image of the unknown object and generating electrical signal data representative of the different domains thereof independent of any electrical signal generated in response to the detection of the real image of the known object;

f) collecting the electrical signal data representing the different angular and radial components of the spatial domains of the transform image of the unknown object and collectively defining a characteristic electric signature vector representing the transform image of the unknown object; and

g) comparing the electric signature vectors representing the transform images of the unknown object and the plurality of samples of the known object and determining whether the signature vector of the unknown object conforms to the composite signature vector for the known plurality of samples of the object, and thus determining whether the unknown object qualifies as an acceptable object.

2. The method of claim 1 wherein the steps of generating transform optical images comprises generating optical transform images using light reflected from a representation of an object.

3. The method of claim 1 wherein the steps of sampling light and generating electrical signal data representing a transform image of an object comprises sampling light from multiple angular and radial components of the spatial domains of the transform image and generating electrical signals representative of the intensity of the light in each of the different domains sampled.

4. The method of claim 1 wherein the step of collecting, for the plurality of samples of the known object, the electrical signal data and defining and storing a composite signature vector comprises correlating the electrical signal data to the angular and radial components of the spatial domain it represents and storing the correlated signal data in a predetermined order according to the domain it represents.

5. The method of claim 1 wherein the step of sampling light from different angular and radial components of the spatial domains of the transform image of the unknown object comprises sampling light from different angular and radial components of the spatial domains of the transform image of the unknown object that correspond to the angular and radial components of the spatial domains sampled from the transform image of the known object.

6. The method of claim 1 wherein the step of collecting, for the unknown object, the electrical signal data and defining a signature vector comprises collecting the electrical signal data and defining a signature vector in the same manner as was done for the known object.

7. The method of claim 1 wherein the step of collecting, for the plurality of samples of the known object, the electrical signal data and defining and storing a composite signature vector comprises defining and storing a signature vector including predetermined acceptable data ranged derived from the collected electrical signal data.

8. The method of claim 1 further including the step of generating electrical data signals representative of the difference between the signature vectors of a plurality of samples of the known object.

9. The method of claim 1 wherein the step of collectively defining a signature vector further comprises generating statistical data representing variations among predetermined ones of the collected electrical signal data and deriving an optimum value therefor based upon the determined variation.

10. The method of claim 9 wherein the step of generating statistical data comprises determining the Euclidian distance for the signal data in different spatial domains of the transform image of the objects.

11. The method of claim 9 wherein the step of generating statistical data comprises determining the largest separation between features in different spatial domains of the transform image of the objects.

12. The method of claim 1 wherein the step of defining and storing a composite electrical signature vector representing the transform images for the plurality of samples of the known object comprises defining and storing a single composite signature vector representing a range of acceptable signal data values of the angular and radial components of the spatial domain on the transform image, with the range being defined between the highest and lowest signal data for the spatial domain for the plurality of samples of a known object.

13. Means for optically evaluating the conformance of an unknown object to a standard comprising:

a) means for generating a plurality of optical transform images of a corresponding plurality of samples of an object;

b) means for sampling light from different angular and radial components of the spatial domains of the plurality of transform images of the corresponding plurality of samples of the object and generating electrical signal data representative of the different domains thereof independent of any electrical signal generated in response to the detection of the real image of the plurality of samples of the known object;

c) means for collecting the electrical signal data representing the different angular and radial components of the spatial domains of the plurality of transform images of the corresponding plurality of samples of the object and collectively defining and storing a composite electric signature vector representing the transform images of the known object;

d) means for comparing the electric signature vectors representing the transform images of unknown object and the plurality of samples of the known object and determining whether the signature vector of the unknown object conforms to the composite signature vector for the plurality of samples of the known object, and thus determining whether the unknown object qualifies as an acceptable object.

14. The apparatus of claim 13 wherein the means for generating transform optical images comprises means for generating optical transform images using light reflected from a representation of an object.

15. The apparatus of claim 13 wherein the means for sampling light and generating electrical signal data representing a transform image of an object comprises means for sampling light from multiple angular and radial components of the spatial domains of the transform image and generating electrical signals representative of the intensity of the light in each of the different domains sampled.

16. The apparatus of claim 13 wherein the means for collecting the electrical signal data and defining and storing a signature vector comprises means for correlating the electrical signal data to the angular and radial components of the spatial domain it represents and storing the correlated signal data in a predetermined order according to the domain it represents.

17. The apparatus of claim 13 wherein the means for sampling light from different angular and radial components of the spatial domains of the transform image of the unknown object comprises means for sampling light from different angular and radial components of the spatial domains of the transform image of the unknown object that correspond to the angular and radial components of the spatial domains sampled from the transform image of the known object.

18. The apparatus of claim 13 wherein the means for collecting the electrical signal data and defining and storing a signature vector comprises means for defining and storing a signature vector including any predetermined acceptable data ranged derived from the collected electrical signal data.

19. The apparatus of claim 13 further including means for generating electrical data signals representative of the differences between the signature vectors of a plurality of samples of the known objects.

20. The apparatus of claim 13 wherein the means for collectively defining a signature vector further comprises means for generating statistical data representing variations among predetermined ones of the collected electrical signal data and deriving an optimum value therefor based upon the determined variation.

21. The apparatus of claim 13 wherein the means for defining and storing a signature vector representing a composite transform image for the plurality of samples of the known object comprises means for defining and storing a single signature vector representing a range of acceptable signal data values for the angular and radial components of the spatial domain of the transform image, with the range being defined between the highest and lowest signal data for the spatial domain.