DEFECT INSPECTION METHOD AND APPARATUS THEREFOR

• US 20170356856A1
• Filed: 06/05/2017
• Published: 12/14/2017
• Est. Priority Date: 06/09/2016
• Status: Active Grant

• Current Assignee: Honda Motor Co., Ltd. (Honda Motor Company)
• Original Assignee: Honda Motor Co., Ltd. (Honda Motor Company)
• Inventors: Matsumoto, Junichi
• Granted Patent: US 9,970,887 B2
• Time in Patent Office: Days
• CPC Class Codes: G01B 11/30 for measuring roughness or irregularity of surfaces
• CPC Class Codes: G01N 2021/8829 Shadow projection or structured background, e.g. for deflectometry
• CPC Class Codes: G01N 2021/8887 based on image processing techniques
• CPC Class Codes: G01N 21/8806 Specially adapted optical and illumination features
• CPC Class Codes: G01N 21/8851 Scan or image signal processing specially adapted therefor, e.g. for scan signal adjustment, for detecting different kinds of defects, for compensating for structures, markings, edges G01N21/8806 and G01N21/93 - G01N21/95692 take precedence; optical measurement of dimensions G01B11/00; optical scanning G02B26/10; image transformation G06T3/00; computerised image enhancement G06T5/00; image processing per se for flaw detection G06T7/0002
• CPC Class Codes: G01N 21/9515 Objects of complex shape, e.g. examined with use of a surface follower device measuring contours and curvatures G01B11/24
• CPC Class Codes: G01N 21/956 Inspecting patterns on the surface of objects contactless testing of electronic circuits G01R31/308; testing currency G07D; manufacturing processes per se of semiconductor devices implementing a measuring step H01L22/10
• CPC Class Codes: G02B 26/02 for controlling the intensity of light G02B26/004 takes precedence
• CPC Class Codes: G06T 2207/30156 Vehicle coating
• CPC Class Codes: G06T 5/50 using two or more images, e.g. averaging or subtraction
• CPC Class Codes: G06T 7/0004 Industrial image inspection
• CPC Class Codes: G06T 7/001 using an image reference approach

Abstract

Slit light is irradiated onto an object to be photographed (for example, an automobile body) in order to obtain a source image. Next, either one of a maximum value filtering process or a minimum value filtering process is performed on the source image to thereby obtain a first filter-processed image. Furthermore, after obtaining a second filter-processed image by carrying out a remaining one of the minimum value filtering process or the maximum value filtering process with respect to the first filter-processed image, a difference is determined between the second filter-processed image and the source image, and a difference image is obtained. Thereafter, a binarization process is implemented with respect to the difference image.

Claims

1. A defect inspection method of inspecting whether or not a defect exists on an object to be photographed, by irradiating striped illumination with respect to the object to be photographed, and based on an image obtained from the object to be photographed, comprising the steps of:

irradiating striped illumination on the object to be photographed from a striped illumination irradiating unit;

photographing, by an image capturing unit, the object to be photographed which is irradiated with the striped illumination, and obtaining a source image;

obtaining a first filter-processed image by a first filtering process that carries out either one of a maximum value filtering process or a minimum value filtering process with respect to the source image;

obtaining a second filter-processed image by a second filtering process that carries out a remaining one of the minimum value filtering process or the maximum value filtering process with respect to the first filter-processed image;

obtaining a difference image in which a difference from the source image is determined using the second filter-processed image as a background image; and

performing a binarization process with respect to the difference image, and obtaining a binarized image for determining whether or not a defect exists within an imaging range.

2. The defect inspection method according to claim 1, wherein, after having performed the first filtering process a plurality of times, the second filtering process is performed the same number of times as the first filtering process.

3. The defect inspection method according to claim 2, wherein the first filtering process and the second filtering process are performed individually two times or more.

4. A defect inspection apparatus adapted to inspect whether or not a defect exists on an object to be photographed, by irradiating striped illumination with respect to the object to be photographed, and based on an image obtained from the object to be photographed, comprising:

a striped illumination irradiating unit adapted to irradiate the object to be photographed with striped illumination;

an image capturing unit adapted to photograph the object to be photographed which is irradiated with the striped illumination;

an image analysis processing unit adapted to carry out an image analysis process with respect to a source image obtained by the image capturing unit; and

a displacement device adapted to displace the striped illumination irradiating unit and the image capturing unit;

wherein the image analysis processing unit performs a first filtering process to obtain a first filter-processed image by carrying out either one of a maximum value filtering process or a minimum value filtering process with respect to the source image, a second filtering process to obtain a second filter-processed image by carrying out a remaining one of the minimum value filtering process or the maximum value filtering process with respect to the first filter-processed image, a differentiating process to obtain a difference image in which a difference from the source image is determined using the second filter-processed image as a background image, and a binarization process with respect to the difference image.

5. The defect inspection apparatus according to claim 4, wherein the image analysis processing unit, after having performed the first filtering process a plurality of times, performs the second filtering process the same number of times as the first filtering process.

6. The defect inspection apparatus according to claim 5, wherein the image analysis processing unit performs the first filtering process and the second filtering process individually two times or more.