Machine vision process and apparatus for reading a plurality of separated figures

• US 4,866,629 A
• Filed: 11/09/1987
• Issued: 09/12/1989
• Est. Priority Date: 11/13/1987
• Status: Expired due to Term

• Current Assignee: Industrial Technology Research Institute
• Original Assignee: Industrial Technology Research Institute
• Inventors: Chung, Ching-Fu, Shyy, Yeu-Hwa, Chen, Inn-Ming, Yeh, Jenq-Chang, Hwang, Dar-Jong, Wu, Hsu-Lung
• Primary Examiner(s): MACDONALD, ALLEN R
• Application Number:
  US07/118,036
• Time in Patent Office: 673 Days
• Field of Search: 364/468, 364/488-491, 364/560, 364/564, 358/101, 382/8
• US Class Current: 700/95
• CPC Class Codes: G05B 19/4205 in which a drawing is traced or scanned and corresponding data recorded
• CPC Class Codes: G05B 2219/37553 Two cameras one for coarse scanning, other for fine scanning
• CPC Class Codes: G05B 2219/45035 Printed circuit boards, also holes to be drilled in a plate
• CPC Class Codes: G05B 2219/45129 Boring, drilling
• CPC Class Codes: G05B 2219/49113 Align elements like hole and drill, centering tool, probe, workpiece
• CPC Class Codes: G06T 2207/30141 Printed circuit board [PCB]
• CPC Class Codes: G06T 7/70 Determining position or orientation of objects or cameras camera calibration G06T7/80

Abstract

A machine vision process and apparatus for reading a plurality of separated figures, such as the hole-position diagram of a printed-circuit board; the apparatus comprises an X-Y table to be moved on a plane and to be positioned at a given position, two photographing devies such as camaras being mounted over the X-Y table, and an image processing unit. The X-Y table is used for placing a diagram or the like so as to facilitate a first camera to photograph a large area and to facilitate a second camera to photograph a small and detailed separated figure. The image signal obtained will be transmitted to the image processing unit to find out the center coordinates of every separated figure, and the size and shape of every separated figure classified so as to find out the control data of size, position and the moving path in the real production process.

Claims

1. A method for identifying and locating separated figures on a plane diagram which is to be operated upon, comprising the steps of:

photographing a large area of said plane diagram;

identifying with respect to a first coordinate system coordinates of the approximate center of each separated figure located within said large area;

determining a precision photographing path from one such figure to another on the basis of said coordinates of each separated figure;

photographing a small area of said plane diagram along said precision photographing path;

identifying with respect to said first coordinate system second coordinates of the precise center, size and shape of each separated figure within said small area;

classifying and arranging each separated figure in a second sequence on the basis of each corresponding size and shape of each separated figure; and

providing said second sequence as operation data for operation upon said plane diagram.

2. A method as recited in claim 1, wherein:

said step identifying said approximate center comprises the steps of;

determining said approximate center of each separated figure located within said large area, and

converting said approximate center of each separated figure to said coordinates with respect to said first coordinate system, said first coordinate system being defined with respect to said plane diagram; and

said step identifying said precise center comprises the steps of;

determining said precise center, size and shape of each separated figure within said small area, and

converting said precise center of said separated to said second coordinates with respect to said first coordinate system.

3. A method as recited in claim 2, wherein said approximate center determining step includes the steps of:

determining a binary threshold on the basis of a multi-level gray scale of an image of said large area, said binary threshold distinguishing said separated figures from a background of said plane diagram;

inspecting a plurality of grid points on said large area image in a regular sequence to determine the presence of a separated figure; and

scanning a plurality of grid points within said separated figure, said grid points being defined as bright points to prevent further inspection, said bright points indicating a nonseparated figure.

4. A method as recited in claim 3, wherein said precision photographing path determining step comprises the steps of:

dividing said plane diagram into a plurality of corresponding rows and columns to form districts, wherein at least two separate figures within a district are scanned within a predetermined time;

assigning a corresponding row, column and series value to each of said separated figures, said corresponding row and column values being assigned on the basis of a location of each of said separated figures within said districts; and

defining a direction-alternating permutation sequence, said sequence-defining step comprising the steps of;

first arranging said separated figures with respect to increasing column values,

assigning a first inspection direction within said first column, wherein said series values of said separated figures located within said first column are respectively arranged with respect to increase row values;

analyzing a next column,

second arranging said separated figures in another inspection direction if a separated figure is present within said column being analyzed, said second arranging step alternating between said first inspection direction and a second inspection direction, said second inspection direction respectively arranging said series values of said separated figures within said column being analyzed with respect to decreasing row values, and

repeating said previous two steps until all of said columns are analyzed.

5. A method as recited in claim 4, wherein said predetermined time is less than a time period necessary for precise calculation of a general separated figure.

6. A method as recited in claim 3, wherein said step converting said precise center to said second corresponding coordinate is equivalent to said step converting said approximate center to said coordinate with respect to said plane diagram.

7. A method as recited in claim 3, wherein said step classifying and arranging each separated figure in a second sequence is equivalent to said step determining said precision photographing path.

8. An apparatus for recognizing a plurality of separated figures on a plane diagram comprising:

an X-Y table for supporting said plane diagram, said X-Y table being capable of moving said plane diagram along a first and second axis;

photographic means, disposed above said plane diagram, for taking a first and second image of said plane diagram;

means for determining an approximate center of each separated figure located within said first image;

path determining means for determining a precision photographing path in response to the locations of each of said separated figures within said first image, said precision photographing path providing a sequence of each of said separated figures, said photographic means taking said second image as said X-Y table moves said plane diagram in response to said precision photographing path;

means for determining a corresponding size, shape and precise center of each separated figure in said second image;

processing means for arranging said separated figures in a second sequence on the basis of said corresponding size, shape and location of said precise center of each separated figure in said second image; and

output means for providing said second sequence to an external device.

9. An apparatus as recited in claim 8, wherein said photographic means comprises a first camera for taking said first image, and a second camera for taking said second image.

10. An apparatus as recited in claim 8, wherein said means for determining an approximate center converts said approximate center of each separated figure to a coordinate with respect to said plane diagram.