Automatic optical inspection apparatus

• US 4,509,075 A
• Filed: 06/15/1981
• Issued: 04/02/1985
• Est. Priority Date: 06/15/1981
• Status: Expired due to Fees

• Current Assignee: Oxbridge Incorporated
• Original Assignee: Oxbridge Incorporated
• Inventors: Haney, Jerry D., Simms, R. John
• Primary Examiner(s): Orsino, Jr., Joseph A.
• Application Number:
  US06/273,508
• Time in Patent Office: 1,387 Days
• Field of Search: 358/93, 358/106, 356/390, 356/394, 250/223 B, 209/528, 209/526, 209/524, 283/21, 40/310
• US Class Current: 348/129
• CPC Class Codes: B07C 5/34 Sorting according to other particular properties material testing per se G01N; quality control G07C3/14
• CPC Class Codes: G06T 5/50 using two or more images, e.g. averaging or subtraction

Abstract

An automatic optical inspection method apparatus wherein optical preprogramming means are utilized to designate the locations of reference features on a reference object, and to instruct the system regarding the reference feature characteristics, and of reference feature parameters, the automatic optical inspection apparatus is then utilizing information obtained from the optical pre-programming means to analyze image data obtained from objects under inspection, the apparatus initially obtaining a larger amount of optical imaging data and systematically thereafter reducing the quantity of such data by appropriate signal processing and gating, so that an accept or reject decision is based upon a small portion of the originally obtained data.

Claims

1. An automatic inspection apparatus for inspecting a series of illuminated objects comprising

means positionable on a properly configured object for identifying portions on the properly configured object;

means for recognizing the identifying means on the properly configured object including means for obtaining reference data from the identified portions and for deriving inspection instructions from the identifying means and from the reference data; and

data processing means responsive to the inspection instructions for evaluating data in accordance with the inspection instructions to derive an accept-or-reject decision, the data originating from subsequent objects, wherein the data processing means evaluate data corresponding to portions of the subsequent objects which portions are the counterparts of the identified portions of the properly configured object.

2. The automatic inspection apparatus, as recited in claim 1, wherein the identifying means include a target which is capable of being affixed to the properly configured object, the target comprising a plurality of optically readable indicia which identify to the recognizing means the presence of one of the identified portions of the properly configured object, and a window through which the identified portions of the properly configured object can be optically scanned.

3. The automatic optical inspection apparatus, as recited in claim 2, wherein the recognizing means comprise

first imaging and video signal-generating means having a selected field of view for obtaining a full video image from the properly configured object within the field of view, and for converting the video image into equivalent electrical image signals;

means responsive to the image signals for extracting the portions of the image signals which originate from targets; and

processing means for analyzing the target image signals and deriving reference data and inspection instructions for each identified portion of the properly configured object.

4. The automatic optical inspection apparatus, as recited in claim 3, wherein the data processing means include

second imaging a video signal-generating means, having a field of view for obtaining a full video image of a subsequent object to be inspected within the field of view, and for converting the video image into equivalent electrical image signals;

means responsive to the image signals from the second imaging means and inspection instructions for selecting the portions of the image signals which originate from those portions of the subsequent object that correspond to the identified portion of the properly configured object; and

means for comparing the selected image signals to the reference data and in accordance with the inspection instructions to derive an accept-or-reject decision.

5. The automatic optical inspection apparatus, as recited in claim 4 wherein the processing means comprise a first host processor which supplies reference extraction signals to the extracting means and further wherein the extracting means extract the target image signals from the image signals in accordance with reference extraction signals, the first host processor thereafter analyzing the target image signals and, based upon the analysis, thereafter deriving reference parameters for use in subsequent object inspection, the reference parameters including a specific inspection control and processing sequence and a set of reference data.

6. The automatic optical inspection apparatus, as recited in claim 5, wherein the means for extracting target image signals comprise a first slave processor responsive to the reference extraction signals from the first host processor, the first slave processor providing control signals to the first imaging and video signal-generating means and analyzing the image signals received from the first imaging and video signal-generating means in accordance with the reference extraction signals.

7. The automatic optical inspection apparatus as recited in claim 6, wherein the inspection instructions include an inspection control and processing sequence and

further wherein the comparing means comprise comparator means for comparing the selected image signals against the reference data;

and wherein the first slave processor are further responsive to the inspection control and processing sequence to supply the reference data and control signals to the comparator means; and

the first host processor are further coupled to the comparator means for receiving the results of the comparison and for evaluating the results in accordance with the inspection control and processing sequence to obtain the accept-or-reject decision.

8. The automatic optical inspection apparatus, as recited in claim 6, wherein the reference parameters include an inspection control and processing sequence and a set of reference data, and further wherein the means for comparing the selected image signals to the reference parameters include

comparator means for comparing the selected image signals against designated reference data;

second slave processor means responsive to the inspection control and processing sequence for supplying the reference data and control signals to the comparator means; and

second host processor means for receiving the results of the comparison and for evaluating the results in accordance with the reference parameters to obtain an accept-or-reject decision.

9. The automatic optical inspection apparatus, as recited in claim 8, wherein the means for selecting the image signal portions include

analog processing means responsive to the equivalent electrical image signals for buffering and gain control of the image signals;

and

conversion means responsive to the processed image signal for converting the image signal into a digital image signal, the conversion means having variable operating speed, resolution, full scale, and zero offset capabilities of the conversion means being enabled by the second slave processor whenever the portions of the subsequent objects being scanned correspond to the specified portions of the properly configured object.

10. The automatic optical inspection apparatus as recited in claim 3, wherein the first imaging and video signal generating means further obtain a full video image from a subsequent object to be inspected within the field of view and convert the video image into equivalent electrical image signals, wherein the first imaging and video signal generating means include

lens means for focusing an optical image;

and

optical sensor means responsive to the focused optical image for converting the optical image into an equivalent electrical image signal; and

further wherein the data processing means comprise

means responsive to the image signals and inspection instructions for selecting portions of the image signals which originate from those portions of the subsequent object that correspond to the identified portion of the properly configured object; and

means for comparing the selected image signals to the reference data to derive an accept-or-reject decision.

11. The automatic optical inspection apparatus, as recited in claim 10, wherein the optical sensor means comprise an array of optical sensors.

12. The automatic optical inspection apparatus, as recited in claim 11, wherein the array of optical sensors has a plurality of rows and columns, and further including means for strobing the illumination of the object under inspection so that a full optical image of the object under inspection can be instantaneously obtained.

13. The automatic optical inspection apparatus, as recited in claim 11, wherein the array of optical sensors is arranged in a single vertical column so that a sequence of columnar image signals are produced as the object under inspection is scanned, the total sequence of columnar image signals providing a full image signal of the object under inspection.

14. An automatic optical inspection apparatus for inspecting an illuminated, sequentially-presented series of visually similar objects, wherein the objects are compared against a number of reference features from a reference object and a decision is made to accept or reject the current object under test, the apparatus comprising

optical pre-programming means positionable upon the reference object for optically designating the reference features on the reference object, and for optically indicating a number of reference feature parameters and providing inspection instructions;

imaging and video signal-generating means, having a specified field of view for obtaining a complete video image of an object within the field of view, and for converting the video image into an equivalent electrical image signal;

signal processing and gating means responsive to the image signal for processing the image signal and for recognizing portions of the image signal as designated by the optical pre-programming means including means for deriving reference feature specifications from the recognized image signal portions and the inspection instructions from the optical pre-programming means and the recognized image signal portions;

comparative evaluation means responsive to the reference feature specifications and the inspection instructions for comparing the selected portions of the image signal from the object under test against the reference feature specifications to provide an indication of the similarity between the selected image signal and the corresponding reference feature specifications; and

control means responsive to the inspection instructions for examining the indication of similarity provided by the comparative evaluation means to accept or reject the object under inspection.

15. The automatic optical inspection apparatus, as recited in claim 14, further including an image signal storage means for storing image signals from the signal processing and gating means in real time so that the image signals can be recalled for analysis at a future time.

16. The automatic optical inspection apparatus, as recited in claim 14, wherein the signal processing and gating means include

analog signal processing means for providing buffering and gain control of the electrical image signal;

variable analog to digital conversion means for converting the electrical image signal into an equivalent digital image signal, the conversion means being responsive to an operating speed signal, a resolution signal, a full scale value signal, and a zero value signal which are supplied by the intelligent processing and control means; and

signal selection means for selectively gating those portions of the equivalent digital image signal which correspond to the reference feature location on the reference object for further processing.

17. The automatic optical inspection apparatus, as recited in claim 14, wherein the processing and control means comprise

slave processing and control means for controlling the imaging and video signal-generating means, the signal processing and gating means and the comparative evaluation means, and for processing the indication of similarity obtained from the comparative evaluation means;

and

host processor means for providing instructions to the slave processing and control means to direct the processing of reference feature and parameter data and the processing of data from the object under test, and for receiving the processed indication of similarity data, and for making an accept or reject decision thereon.

18. The automatic optical inspection apparatus, as recited in claim 14, further including digital processing means for enhancing the quality of a gated digital image signal, the digital processing means receiving the gated digital image signal from the signal processing and gating means, and supplying the enhanced digital image signal to the comparative evaluation means.

19. The automatic optical inspection apparatus, as recited in claim 14, wherein the imaging means include

an imaging lens;

and

a plurality of optical to electronic sensors, wherein the imaging lens focuses the image one image on the sensors and the sensors convert the image into an equivalent electrical image signal; and

further wherein sensors are controlled by a timing signal which is supplied by the intelligent processing and control means.

20. The automatic optical inspection apparatus, as recited in claim 19, wherein the optical to electronic sensors comprise an array of optical sensors.

21. The automatic optical inspection apparatus, as recited in claim 19, wherein the optical to electronic sensors comprise a vertical column of optical sensors.

22. The automatic optical inspection apparatus, as recited in claim 14, wherein the optical pre-programming means includes a target which is capable of being affixed to the reference object, the target comprising a plurality of optically readable indicia for providing the reference feature parameters, and a window through which the reference feature can be optically scanned.

23. The automatic optical inspection apparatus, as recited in claim 22, wherein the target is rectangular in shape, and further wherein the optically readable indicia comprise

a plurality of spaced-apart teeth positioned along the outer edge of the target, the teeth having different widths and spacings which are arranged in a predetermined pattern, and

a combination of optical reflectance transitions upon the target surface.

24. The automatic optical inspection apparatus, as recited in claim 23, wherein the pattern of teeth on parallel edges of the target are identical.

25. The automatic optical inspection apparatus, as recited in claim 23, wherein the optical transitions upon the target surface include a tolerance band for providing reference feature tolerance information.

26. The automatic optical inspection apparatus, as recited in claim 23, wherein the optical transitions upon the target surface include a low reflectance area and a high reflectance area, the areas having a transition from low reflectance to high reflectance which lies along the width of the target, the transition being coincident with a hypothetical, horizontal bisector of the window;

and a plurality of fiduciary segments which are centered along a hypothetical, vertical bisector of the window, the fiduciary segments which lie in the high reflectance area having a low reflectance, and the fiduciary segments which lie in the low reflectance area having a high reflectance.

27. The automatic optical inspection apparatus, as recited in claim 23, wherein the window has a rectangular shape.

28. The automatic optical inspection apparatus, as recited in claim 22, wherein the target is circular in shape and further wherein the optically readable indicia include

a plurality of radially-extending spaced-apart bars located on the surface of the target, the bars extending from the outer edge toward the center of the target a predetermined first distance;

and

a plurality of concentric, spaced-apart rings extending outward from the center of the target a predetermined second distance.

29. The automatic optical inspection apparatus, as recited in claim 28, wherein the window has a circular shape and is positioned at the center of the target.

30. An automatic optical inspection apparatus for inspecting an illuminated, sequentially-presented series of visually similar objects, wherein the objects are compared against a number of reference features from a reference object and a decision is made to accept or reject the current object under test, the apparatus comprising

optical pre-programming means positionable upon the reference object for optically designating the reference features on the reference object, and for optically indicating a number of reference feature parameters, wherein the reference feature parameters include a nominal location for each reference feature, a characterization of the optical nature of each feature, and information concerning the tolerance with which each feature is to be examined;

imaging and video signal-generating means, having a specified field of view for obtaining a complete video image of an object within the field of view, and for converting the video image into an equivalent electrical image signal;

signal processing and gating means responsive to the image signal for processing the image signal and for recognizing portions of the image signal as designated by the optical pre-programming means including means for deriving reference feature specifications from the recognized image signal portions;

comparative evaluation means responsive to the reference feature specifications for comparing the selected portions of the image signal from the object under test against the reference feature specifications to provide an indication of the similarity between the selected image signal and the corresponding reference feature specifications; and

control means for examining the indication of similarity provided by the comparative evaluation means to accept or reject the object under inspection.

31. A method of automatic optical inspection wherein a series of illuminated, visually similar objects are inspected and accepted or rejected, the method comprising the steps of

positioning optical specifying means on a properly configured object to identify portions thereof;

obtaining optical data from the properly configured object;

recognizing the presence of data from the optical specifying means in the optical data;

analyzing data from the identified portions of the properly configured object to derive reference parameters and inspection instructions for each selected portion;

comparing selected data from subsequent objects to the reference parameters in accordance with the inspection instructions, the selected data originating from those portions of each subsequent object which correspond to the specified, selected portions of the properly configured object; and

evaluating the comparison results to derive an accept-or-reject decision.

32. The method of automatic optical inspection, as recited in claim 31, wherein the step of positioning optical specifying means on a properly configured object includes the step of

placing a target over each object portion which is to be inspected, the target having optically readable indicia which identify the presence of the object portion and a window through which the object portion can be optically scanned.

33. The method of automatic optical inspection, as recited in claim 31, wherein the data analyzing step further includes the step of

designating a set of instructions based upon the analyzed data for control of data acquisition from the subsequent objects.

34. A method of automatic optical inspection, wherein a series of illuminated, sequentially presented, visually similar objects are compared against a reference object, and a decision is made to accept or reject the current object under inspection, the method comprising the steps of

positioning targets on the reference object to optically designate a number of reference features and corresponding reference feature specifications and locations on the reference object;

recognizing the presence of the targets and the designated features on the reference object;

converting the designated optical reference features and parameters into an equivalent electrical digital reference signal;

processing the digital reference signal in an intelligent processing and control means to obtain inspection instructions including location, tolerance and optically descriptive information about the reference features;

obtaining an equivalent electrical image signal from a complete video image of the object under inspection;

processing and gating the image signal so that the image signal is converted to digital form and so that the portions of the image signal which correspond to the locations of the reference features are selected for further processing;

comparing the selected digitized image signals to the corresponding digital reference signal so that an indication of similarity between the two signals is obtained; and

analyzing the indication of similarity in accordance with the reference feature parameters to obtain an accept or reject determination.

35. A method of automatic optical inspection, wherein a series of illuminated, visually similar objects are inspected, and accepted or rejected, the method comprising the steps of

selecting an object as a reference object against which all other objects are compared;

optically specifying particular features on the reference object for examination by placing a target over each reference feature, the target having a window through which the particular feature can be optically scanned, the target further having optically coded information;

scanning the reference object to obtain information from each target and the reference feature within each target window;

analyzing the target and reference feature information;

deriving a set of timing, control, and processing instructions and a set of reference data for use in evaluating the objects to be inspected from the target and reference feature information;

scanning the objects to be inspected according to the instruction set so that an equivalent electrical image signal of the video image of each object is obtained;

processing the electrical image signals according to the instruction set so that portions of the image signal are selected which originate from the locations on the inspected object corresponding to the locations on the reference object which were designated by each target window;

comparing the selected portions of the object image with the reference data set; and

evaluating the comparison results according to the instruction set to obtain an accept-or-reject decision.