GB2248932A

GB2248932A - Method for processing compacted data

Info

Publication number: GB2248932A
Application number: GB9119775A
Authority: GB
Inventors: Stanley P Turcheck; Randy K Baird; James P Martin
Original assignee: FMC Corp
Current assignee: FMC Corp
Priority date: 1990-09-17
Filing date: 1991-09-16
Publication date: 1992-04-22
Anticipated expiration: 2011-09-16
Also published as: GB9119778D0; GB2248685A; GB2248686B; GB2248934B; GB2248931A; GB2248931B; GB9119775D0; GB9119774D0; GB9119777D0; GB2248685B; GB2248933A; GB2248934A; GB2248933B; GB2248686A; GB2248932B; GB9119780D0; GB9119776D0

Abstract

A first set of digital data (data 1, Fig. 3) is converted into compact form (data 1, Fig. 4) by recording a set of points at which the signal level changes. A second set of digital data (data 2, Fig. 3) is likewise convened into compact form by recording the points of signal level change (data 2, Fig. 3). A logic function (e.g. the logical OR function) is then used to compare the first set of compact data with the second set of compact data, to obtain a third data set (data 3). Data 1 and Data 2 may be image data relating to a test object and a standard object with which the test object is to be compared, the values of Data 3 being used to determine whether or not the test object is acceptable. <IMAGE>

Description

22 4 3-132 1 METHOD FOR PROCESSING COMPACTED DATA Details of a parts

inspection system in which the present invention can be used are disclosed in our co-pending patent application entitled "HIGH- RESOLUTION VISION SYSTEM FOR PART INSPECTION" and filed on even date herewith.

BACKGROUND OF THE INVENTION

The present invention relates to a method for processing compacted data, and more particularly, to a inethod f or comparing a f irst set of digital data in compact form with a second set of digital data in compact form in order to process extremely large amounts of data.

objects such as mechanical parts are commonly inspected for defects and for variations from standard size and shapes, for example, before being placed into machinery. When a mechanical visual inspection is used a standard part may be inspected and the specification of this standard part placed in some type of storage. The vision system then inspects a plurality of similar mechanical parts and compares each of the inspected parts with specifications of the standard parts. In order to provide an accurate and complete inspection a very large number of bits of information about each of the inspected parts must be compared with a very large number of bits of information about the standard part. Such a process is slow and expensive.

2 SUMMARY OF THE INVENTION

The invention discloses a method for comparing a f irst set of digital data with a second set of digital data said method comprising the steps of: recording a first set of signal points at which said first set of digital data changes signal levels to obtain a first set of compacted data; recording a second set of signal points at which said second set of digital data changes signal level to obtain a second set of compacted data; and using a logic comparison function to obtain a third set of compacted digital data from said first and said second sets of compacted data.

As applied to the inspection of objects, the first set of data may be representative of the image of an object under inspection, with the second set of data representative of the image of a standard object. The third set of compacted data may then be examined to determine if it is within acceptable limits. The logic function used to obtain the third set of compacted data can be one of a variety of functions, such as OR Logic, AND logic and Exclusive OR logic.

These and further features of the invention will be apparent from the following description made by way of example and with reference to the drawings, in which:-

3 Figure 1 is an illustration of a parts inspection apparatus which uses a method of comparing sets of compacted digital data of the present invention.

Figure 2 is a block diagram of circuitry for using compacted digital date to inspect parts.

Figure 3 illustrates the combining of a pair of sets of uncompacted data using an OR function.

Figure 4 illustrates the combining of a pair of sets of compacted data using an OR function.

Figure 5 is a graphic representation of the sets of data shown in Figure 3.

Figure 6 is a flow chart of a method of processing the compacted data of Figure 4.

Figure 7 illustrates the combining of a pair of sets of data using an AND function.

Figure 8 illustrates the combining of a pair of sets of compacted data using an AND function.

Figure 9 illustrates the combining of a pair of sets of data using an Exclusive OR function.

Figure 10 illustrates the combining of a pair of sets of compact data using an Exclusive OR function.

DESCRIPTION OF THE PREFERRED EMBODIMENT

A vision inspection apparatus 9 in which the present invention can be used is disclosed in Figure 1. A feeder lo singulates a plurality of parts 11 which are moved past a 4 light source 12 and a geometric parts sensor 16. Parts sensor 16 senses the geometry of each part and provides signals to a vision controller and interface 17. A position sensor 18 senses the position of each part 11 as it approaches a part diverter 22. Diverter 22 can be used to reorient parts or to move parts into an output trough 23.

Interface 17 (Figs. 1, 2) includes a CPU controller 24 having a microprocessor 28 and a plurality of input/output modules 29, 30. Parts sensor 16 includes a charged coupled device and a means (not shown) for producing digital signals from the output at the charge coupled device, which contain information concerning the size, shape and surface details of parts 11. A keyboard 28, a display device 29 and a plurality of output ports 33 - 35 are interconnected to controller 24 by a connector board 39.

An example of a small portion of a binary signal which could be developed by visual inspection apparatus 9 (Figs. 1, 2) when a standard part is inspected is shown as binary data 1 of Figure 5 and Figure 3. A portion of the binary data developed by a tested part is shown as binary data 2 (Figs. 3, 5). When data 1 and data 2 (Figs. 3, 5) are combined by an OR circuit or by a CPU having an OR function, the binary information of data 3 is the result. When the uncompacted binary data of data 1, data 2 and data 3 are used a very large number of calculations and comparisons are required to check a tested part against a standard part resulting in long part inspection times.

Inspect time can be greatly reduced by compacting the data as shown in Figure 4. The times at which signal levels change in data 1 and data 2 are listed in the left and center columns of Figure 4. As seen in Figures 3 and 5 the level of data 1 changes at times 3, 9, 12 and 14, and the level of data 2 changes at times 1, 8, 11, 15, 17 and 18. The data 1 and data 2 columns (Fig. 4) can be used by an OR function of a CPU to obtain the data 3 information in a manner shown in the flow chart of Figure 6.

The level of binary data 1, data 2 and data 3 are initially set to zero as shown in step 42 (Figs. 4, 6). CPU controller 24 then records the first upward transition of data 1 in step 43 and the first upward transition of data 2 in step 44. The earliest transition (lowest value A or B) is set as the first compacted data in step 45 (Fig. 6) and as recorded in data 3 column (Fig. 4). In step 46 the time period of C is checked against the total time and, if equal, processing stops. In step 47 the time of C is checked against the time of A and in the example of Figures 3 - 5, C is less than A, but not less than B in step 48. At this time (time 1) the level of the data 1 signal is zero (in step 49). The level is set to a one in step 50 in preparation f or the next check in level changes of data 1 and data 2 from high to low. Step 51 finds that more level changes are going to occur. Step 52 observes from Figure 4 that the next transition (downward) in data occurs at time 8. In step 53 the OR function does not change at time 8 because of the downward transition of data 2.

6 At time 9 step 54 sets data 3 as the OR function of data 1 and data 2 of Figure 4 and in step 55 this time (time 9) is stored as compacted data 3. A return to step 45 sets the CPU ready to check for upward changes in compacted data 1 and data 2.

When the complete set of compacted data of Figure 4 has been processed according to the flow chart of Figure 4, the result is compared to a standard to determine if a part being tested falls within acceptable test limits.

Although the best mode contemplated for carrying out the present invention has been herein shown and described, it will be apparent that modification and variation may be made without departing from what is regarded to be the subject matter of the invention as defined in the claims.

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Claims

CLAIMS:

1. A method for comparing a first set of digital data with a second set of digital data said method comprising the steps of: recording a first set of signal points at which said first set of digital data changes signal levels to obtain a first set of compacted data; recording a second set of signal points at which said second set of digital data changes signal level to obtain a second set of compacted data; and, using a logic comparison function to obtain a third set of compacted digital data from said first and said second sets of compacted data.

2. A method of comparing as defined in claim 1 wherein said logic comparison function is an OR function.

3. A method of comparison as defined in claim 1 wherein said logic comparison function is an AND function.

4. A method of comparison as defined in Claim 1 wherein said logic comparison function is an Exclusive OR function.

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5. A method of comparing as defined in any preceding claim including a further step of:

comparing said third set of compacted data with a standard set of compacted data to determine when said third set of compacted data is outside acceptable limits of variation.

6. A method of comparing as def ined in any preceding claim wherein said data sets are image data sets.

7. A method for comparing a f irst set of digital data in compacted form with a second set of digital data in compacted form substantially as described with reference to or as shown in the drawings.