Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1992-12-03
1994-02-01
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
382 48, G01N 2188
Patent
active
052834433
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to inspecting garments for holes.
DISCUSSION OF THE BACKGROUND
Knitted garments, such as socks, are inspected during their production to reject any with faults. A principal fault in knitting is a hole, which may result from one of a number of reasons. Socks are best inspected at the boarding stage, where they are pulled on to a foot-shaped board for a setting treatment. Inspection is very labor-intensive, accounting for many more man-hours than the actual production of the socks, and is therefore a major cost area.
SUMMARY OF THE INVENTION
Moreover, inspectors become fatigued and can miss faults, so that imperfect socks--and other garments--can reach the customer.
The present invention provides an automatic procedure for inspecting garments, especially knitted garments such as socks, for any holes therein, which can be carried out quickly, using low-capital-cost equipment, during the normal manufacturing procedure and without requiring any additional handling operation.
The invention comprises a method for inspecting garments for holes comprising front-lighting the garment against a contrasting background and forming a pixel image thereof, isolating garment pixels from background pixels by automatically selecting an optimum binarization threshold grey level, binarizing the image at that level, determining the garment boundary, testing for inconsistency of grey level within the garment boundary on the binarized image along rows and columns of pixels within the garment boundary and noting inconsistent pixels, and identifying as holes only pixels which have been noted as inconsistent in both horizontal and vertical tests.
The threshold grey level may be selected on the basis of data from a part of the image, for example a single row or column of pixels.
The threshold grey level may be selected by thresholding the image (or the part of the image) at all possible grey levels to yield a histogram in which the number of segmented pixels is plotted against the threshold grey level, which histogram has two peak values, corresponding to object and background, and taking the optimum binarization threshold grey level to be that level at which the histogram has a minimum value between the peaks.
The garment boundary in the binarized image may be determined by tracing the boundary with an eight-directional Freeman chain code robot.
The determined garment boundary length may be compared to a predetermined minimum length to eliminate spurious measurements of noise clusters in the background.
The grey level consistency test may be carried out on a fresh, binarized image produced using a low pass filter operation on the original pixel image, that filtered image being binarized using the selected threshold grey level.
Any inconsistent pixel group discovered by the consistency test within the garment boundary may be indicated on a displayed image by a superimposed marker.
The pixel image may be made by a video camera or CCD device.
The garment may be a knitted garment such as a sock and may be carried out on the boarded garment.
A method for inspecting garments according to the invention will now be described with reference to the accompanying drawings, in which:
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an illustration of an inspection arrangement;
FIG. 2 is a flowchart;
FIG. 3 is a primary pixel image of a sock;
FIG. 4 is a histogram produced from the image of FIG. 3;
FIG. 5 is a segmented image;
FIG. 6 is a diagrammatic representation of a Freeman chaincode boundary tracing operation;
FIG. 7 is an image undergoing a horizontal consistency test;
FIG. 8 is an image undergoing a vertical consistency test; and
FIG. 9 is an image with superimposed hole markers.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The drawings illustrate a method, carried out here on a knitted sock, for inspecting garments for holes.
FIG. 1 illustrates the equipment used in the method. The sock 11, placed on a board 12 for the conventional boarding operation, is front-lit by lamps 13 and view
REFERENCES:
patent: 4124300 (1978-11-01), Mead et al.
patent: 4327375 (1982-04-01), LeClerc
patent: 4330712 (1982-05-01), Yoshida
patent: 4455086 (1984-06-01), West et al.
patent: 4810895 (1989-03-01), Kafri et al.
patent: 4900153 (1990-02-01), Weber et al.
patent: 4952062 (1990-08-01), Bean, III et al.
Computers in Industry vol. 7, No. 2, Apr. 86, Amsterdam, NL, M. A. Sid-Ahmed: `Specific Applications of image processing to surface flaw detection`, see abstract, see p. 135, right column, line 3-p. 136 left column, line 11, see p. 137, left column, line 13-line 27, see p. 137, right column, section, 5.1, see FIGS. 5, 8.
Transactions of the Institute of Measurement and Control. vol. 10, No. 5, Dec. 1988, Dorking GB pp. 265-272; G. A. W. West: `Image processing and understanding for automatic inspection` see p. 267, left column, line 9--line 19 see p. 267, right column, paragraph 4-p. 268, left column, line 42 see FIGS. 1-3.
NEC Research and Development No. 77, Apr. 1985, Tokyo JP pp. 93-102; S. Aratoh: `Development of automatic digitizing system for PWB` see p. 99, line 9-line 17; FIG. 12D.
Abbasszadeh Siavash
Norton-Wayne Leonard
De Montfort University
Le Que T.
Nelms David C.
LandOfFree
Method for inspecting garments for holes having a contrasting ba does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for inspecting garments for holes having a contrasting ba, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for inspecting garments for holes having a contrasting ba will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-581418