Vision inspection system

• US 4,581,762 A
• Filed: 01/19/1984
• Issued: 04/08/1986
• Est. Priority Date: 01/19/1984
• Status: Expired due to Term

• Current Assignee: Acuity Brands, Inc.
• Original Assignee: Itran Corp. (Acuity Brands, Inc.)
• Inventors: Lapidus, Stanley N., Dziezanowski, Joseph J., Greenberg, Michael P., Friedel, Seymour A.
• Primary Examiner(s): Boudreau, Leo H.
• Assistant Examiner(s): Mancuso, Joseph
• Application Number:
  US06/572,570
• Time in Patent Office: 810 Days
• Field of Search: 382/22, 382/30, 382/41, 382/42, 382/34, 382/26, 382/48, 382/23, 382/8, 358/107, 356/394, 356/398, 364/518, 364/559
• US Class Current: 382/263
• CPC Class Codes: G06T 2207/30164 Workpiece; Machine component
• CPC Class Codes: G06T 7/001 using an image reference approach

Abstract

A vision inspection system operable with foreground illumination provides user identification of selected regions of a known object for later comparison to an unknown object. A gray scale pixel array of each selected region is processed for edges and this processed data array is stored as a template for each region. Gray scale illumination data from larger corresponding areas of the unknown object are processed for edges to form gradient maps. The first template is iteratively compared to the first gradient map. A correlation value greater than a threshold value causes the system to examine the second and possibly third gradient maps on the unknown object. Distance and angular relationships of the regions are used to both identify and orient the object under test. Once the unknown object is identified and its orientation determined, various visual attributes and measurements of the object can be determined through use of visual tools.

Claims

1. A vision inspection system for inspecting unknown objects in relationship to a known object and for performing various visual tests on the unknown object if it is recognized as corresponding to the known object, comprising:

A. vision sensing means for producing data representing the illumination values for viewed objects;

B. means for receiving data from the vision sensing means and for storing the image of objects under test;

C. means interconnected to the image storing means for viewing an imaged object;

D. means interfaced with the viewing means for selecting at least three regions of the known imaged object;

E. means interfaced with the image storing means for selecting regions on an unknown object, each region corresponding to one of the selected regions of the known object, each selected region on the unknown object having a size at least equal to the size of the corresponding region on the known object;

F. means interfaced with the image storing means for determining and storing gradient values based upon the rate of change of illumination values for each selected region of the known and unknown objects, said gradient values for each selected region of the known object called a template and for each selected region of the unknown object called a gradient map;

G. means interfaced with the gradient value determining means for determining the spatial and angular relationships between the templates;

H. means interfaced with the gradient value determining means and spatial and angular relationship determining means for overlaying the templates with the gradient maps and for determining the correlation value between each template and the corresponding gradient map, with the separation of said templates based upon the previously determined spatial and angular relationships of said templates;

I. means interfaced to the correlation value determining means for determining if each correlation value is greater than a predetermined value and if true, determining a composite correlation value of said correlation values;

J. means interfaced with the gradient value determining and storing means for moving the templates over each corresponding gradient map so that the correlation value means and composite correlation value means determine their respective correlation and composite correlation values throughout the entire area of each gradient map;

K. means interfaced with the composite correlation value determining means for determining the maximum composite correlation value, if any, and for determining the portions of each gradient map corresponding to this highest composite correlation value; and

L. input/output (I/O) means interfaced with the maximum correlation value determining means for controlling the disposition of the test object based upon the presence or absence of a maximum composite correlation value;

whereby the portions of each gradient map yielding the highest composite correlation value represent recognition of the object under test as corresponding to the known object.

2. A vision inspection system as defined in claim 1, wherein the means for determining gradient values uses a Sobel technique wherein for an array of illumination values denoted by ##STR9## the gradient is equal to

3. A vision inspection system as defined in claim 2, wherein the correlation value determined by the correlation means is defined by the equation:

space="preserve" listing-type="equation">Correlation=(Cross×

Cross)/(AutoPatch×

AutoTemp);

where Cross equals a number obtained by summing the results of multiplying each element in the template with the overlaid element in the gradient map and summing the products, where AutoPatch equals a number obtained by summing the results of multiplying each element in the overlaid portion of the gradient map times itself, and where AutoTemp equals a number obtained by summing the results of multiplying each element in the template with itself.

4. A vision inspection system as defined in claim 3, wherein the means for determining a composite correlation value derives a number obtained by multiplying the correlation value of the first template-gradient map pair by the other correlation values for the remaining template-gradient map pairs.

5. A vision inspection system as defined in claim 4, wherein the means for moving the templates over each corresponding gradient map executes the following steps:

1. determining the correlation value (first correlation value) between the first template and the first gradient map, starting at a first location on the gradient map and moving the template across the first gradient map until a correlation value is determined which is greater than said predetermined value,

2. determining the correlation value (second correlation value) between the second template and the second gradient map having a distance from the location of the first template at its then current position equal to the spatial distance between the first and second templates as determined on the known object, and moving this second template over the second gradient map as defined by an arc equal to this spatial distance, the arc having a predetermined angular size, until a correlation value is cbtained greater than said predetermined value,

3. determining a correlation value (third correlation value) between the third template and the third gradient map spaced and angularly positioned from the first and second templates in their then current positions as said template is spaced and angularly positioned on the known object, and if the correlation value is greater than the predetermined value, then determining the composite correlation value by said composite correlation value means,

7. A vision inspection system as defined in claim 1, further comprising means for performing visual tests (representing visual tools) to a recognized test object based upon the placement and use of those visual tests on the known object.

9. A vision inspection system as defined in claim 7, wherein one of the visual tests is a caliper test comprising means to allow the user to place a caliper image across two positions of an imaged known object and further comprises means for measuring the distance between corresponding positions as defined by their locations on the known object and wherein the results of this test procedure are further used as information for the input/output means for controlling the disposition of the recognized object.

10. A vision inspection system as defined in claim 7, further comprising visual tool means for determining the number of gradient values having magnitudes greater than a predetermined value within an area selected by the user with respect to the known object, wherein a corresponding area is tested on the recognized test object and wherein the number of gradient values having magnitudes greater than said predetermined value are compared to the corresponding number of gradient values for the known object and wherein the results of this test procedure are further used as information for the input/output means for controlling the disposition of the recognized object.

11. A vision inspection system as defined in claim 7, further comprising visual tool means for reading a multi-segment line display wherein said means allows the user to visually position a perimeter series of line segments (called a "jig") about the location of a multi-segment line display on an imaged known object and further wherein perpendicularly placed lines ("feelers") bisect each imaged line segment which is to be tested for presence or non-presence and wherein said visual tool means further comprises means for determining the presence or non-presence of line segments as positioned by said "feelers" on the recognized test object whose overall position on the test object corresponds to the placement of the multi-segment display on the known object and further wherein the results of this test procedure provide information to the input/output means for controlling the disposition of the recognized test object.

12. A vision inspection system as defined in claim 1, wherein the vision sensing means comprises at least one camera which images objects via frontal illumination.

13. A vision inspection system as defined in claim 11, wherein the means for viewing an imaged object comprises a monitor and wherein the means for selecting at least three regions on the known imaged object comprises a light pen, manipulatable by the user on the monitor.

14. A vision inspection system as defined in claim 12, wherein the gradient value determining means comprises an array processor for determining gradient values for the selected regions on the known and unknown objects and for determining the correlation values between overlaid portions of the templates with corresponding portions of the gradient maps.

6. continuing the movement of the second template with respect to the second gradient map throughout the entire arc length and if any correlation value is greater than the predetermined value, determining the corresponding third correlation value between the third template and the third gradient map as angularly and spatially determined by the current positions of the first and second templates, andafter completion of step 4, returning to step 1 and continuing steps 1-5 until the first template has been positioned over each portion of the first gradient map.

8. A vision inspection system as defined in claim 6, wherein the input/output means further comprises means for further controlling the disposition of the test object based upon the results of the test procedures performed on the test object.