Visual inspection method and visual inspection device

Abstract

To provide an inspection method capable of conducting inspection of surface irregularities and visual inspection of surface dirt and the like, simultaneously.SOLUTION: Provided is a visual inspection method that includes: irradiating an inspection workpiece with white diffusion light composed of RGB components and single-color slit light selected from the RGB components simultaneously overlapping mutual irradiation ranges thereof with respect to an inspection surface; creating, by imaging means, a superimposition image in which an area light reflection video and a slit light reflection video of the inspection workpiece are superimposed one on another; RGB-decomposition-processing the superimposition image to create a slit-light component extracted image where the same component as the slit light is extracted and a slit-light excluded component extracted image; binary processing the slit-light component extracted image to create a slit-light enhanced image; and inspecting the workpiece for irregularities by a light cut method on the basis of the slit-light enhanced image. This inspection method further includes: correcting luminance of the slit-light component extracted image to create a slit-light component corrected image; RGB-combination processing the slit-light excluded component extracted image and the slit-light component corrected image to create a slit-light signal image; and inspecting the inspection workpiece for unevenness on the basis of a slit-light erased image.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to an appearance inspection method and an appearance inspection device for inspecting an inspection workpiece for appearance defects, and more particularly to an appearance inspection method and an appearance inspection device for simultaneously inspecting an inspection workpiece for surface contamination and irregularity defects. [Background technology]

[0002] There are visual inspection devices that inspect the surface of an inspection workpiece, which is the product being inspected, for defects in appearance such as scratches, irregularities, stains, and color unevenness. Surface irregularities are measured using a light-sectioning method in which a slit light is projected onto the surface of the inspection workpiece, the reflected light is captured by an imaging device, and the irregularities of the inspection workpiece are measured from the degree of curvature of the lines in the captured image (Patent Document 1). Surface stains and color unevenness are also measured using a method in which an area light, typically diffused lighting, is projected onto the surface of the inspection workpiece, and changes in brightness due to surface stains are detected as a two-dimensional image (Patent Documents 2 and 3).

[0003] A method for inspecting the unevenness and dirt on the surface of an inspection workpiece with a simple configuration has been disclosed (Patent Document 4), in which the unevenness and dirt on the surface of the inspection workpiece are imaged by controlling the on / off switching of the area light source and the slit light source of an illumination means having an area light source and a slit light source whose irradiation ranges on the inspection surface overlap each other. This is because the slit light image gets in the way of the inspection when inspecting for defects in appearance such as color unevenness. However, because the area light source and slit light source need to be switched on and off, it is necessary to take two images, one to inspect the surface for irregularities and one to inspect for surface contamination, which means that this method cannot be used to inspect fast-moving objects or to inspect the entire area using vertical and horizontal grid lines. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-8501 A [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-256245 [Patent Document 3] Japanese Patent Application Laid-Open No. 2013-160745 [Patent Document 4] Japanese Patent Application Laid-Open No. 2013-242256 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention provides an inspection method that can simultaneously inspect surface irregularities using the light-section method with slit light and visual inspection of surface contamination, etc. using area light without switching the illumination light by irradiating slit light and area light simultaneously. [Means for solving the problem]

[0006] The problems of the present invention can be solved by the following aspects (1) to (4). Specifically,

[0007] (Embodiment 1) A visual inspection method using a visual inspection device comprising an imaging means for imaging the inspection surface of an inspection workpiece, an illumination means consisting of area illumination and slit illumination whose illumination ranges on the inspection surface overlap, and an image processing means for processing an image based on a video signal acquired by the imaging means, the method comprising the steps of simultaneously irradiating the inspection workpiece with white diffused light composed of RGB components from the area illumination and monochromatic slit light selected from RGB components from the slit illumination, acquiring a video signal in which the area light reflected video signal and the slit light reflected video signal of the inspection workpiece are superimposed by the imaging means to create a superimposed image, and performing RGB decomposition processing on the superimposed image to create a slit image. the slit-light-excluded component extracted image and the slit-light-excluded component extracted image, which extract the same components as those of the slit illumination; the binarization of the slit-light-extracted image to create a slit-light-enhanced image; the inspection of the unevenness of the inspection workpiece by a light-section method based on the slit-light-enhanced image; the luminance correction of the slit-light-extracted image to create a slit-light-corrected image; the RGB synthesis of the slit-light-excluded component extracted image and the slit-light-corrected image to create a slit-light-eliminated image; and the inspection of the inspection workpiece for unevenness based on the slit-light-eliminated image.

[0008] (Aspect 2) The visual inspection method according to (Aspect 1), wherein the illumination means is a projection device that projects a slit pattern, and is an illumination means that combines area illumination and slit illumination.

[0009] (Aspect 3) An appearance inspection device comprising: an imaging means for imaging the inspection surface of an inspection work; an illumination means consisting of area illumination and slit illumination whose illumination ranges on the inspection surface overlap; and an image processing means for processing an image based on a video signal acquired by the imaging means, wherein the image processing means is a processing device having an execution program that acquires, by the imaging means, a video signal in which the area light reflection video signal and the slit light reflection video signal of the inspection work are superimposed to create a superimposed image; performs RGB decomposition processing on the superimposed image to create a slit light component extracted image in which the same components as those in the slit illumination are extracted, and a slit light excluded component extracted image; performs binarization processing on the slit light component extracted image to create a slit light enhanced image; inspects the inspection work for unevenness using a light section method based on the slit light enhanced image; performs luminance correction on the slit light component extracted image to create a slit light component corrected image; performs RGB composition processing on the slit light excluded component extracted image and the slit light component corrected image to create a slit light eliminated image; and inspects the inspection work for unevenness based on the slit light eliminated image.

[0010] (Aspect 4) The visual inspection device according to (Aspect 3) is characterized in that the illumination means is a projection device that projects a slit pattern, and is an illumination means that combines area illumination and slit illumination. [Effects of the Invention]

[0011] According to the present invention, inspection of surface irregularities by the light-section method using slit light and appearance inspection of surface contamination, etc. using area light can be performed simultaneously without switching the illumination light, so that appearance inspection of a strip-shaped object transported by a transport means can be performed continuously without switching the illumination means. By using a projection device as the illumination means, it is possible to project various slit patterns such as line patterns and grid patterns at high speed, shortening the measurement time and enabling the inspection of a variety of inspection objects. [Brief explanation of the drawings]

[0012] [Figure 1]1 is a diagram showing the overall configuration of an inspection device used in a first embodiment of the present invention. [Figure 2] FIG. 4 is a diagram showing the main configuration of an imaging unit of an inspection device used in a second embodiment of the present invention. [Figure 3] FIG. 10 is a diagram showing the main configuration of an imaging unit of an inspection device used in a third embodiment of the present invention. [Figure 4] 10 illustrates an example of a slit pattern produced by a projection device according to an embodiment of the present invention. [Figure 5] FIG. 1 is a flowchart showing the steps of the appearance inspection method of the present invention. [Figure 6] 1A to 1C are explanatory diagrams showing images processed by the appearance inspection method of the present invention in accordance with an inspection procedure. [Figure 7] 10A and 10B are explanatory diagrams showing a processed image and slit light component luminance of the present invention; [Figure 8] FIG. 10 is a schematic diagram illustrating a binarized "slit-beam enhanced image" used for determining unevenness in the present invention. [Figure 9] FIG. 1 is a schematic diagram illustrating a binarized "slit-light-erased image" used for determining stains according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] An embodiment of the present invention will be described with reference to Figures 1 to 7. However, Figures 1 to 7 are merely examples of the embodiment, and the present invention is not limited to these.

[0014] 1. Inspection equipment (1) Configuration of the inspection device 1 is a diagram showing the overall configuration of an inspection apparatus used in a first embodiment of the present invention. A visual inspection apparatus 100 used in the inspection method of the present invention is composed of an imaging unit 20 and a control unit 30. The imaging unit 20 includes an illumination means (22, 24) consisting of an area illuminator 22 that irradiates the inspection surface of the inspection work 10 with diffused illumination light 21 and a slit illuminator 24 that irradiates the inspection surface of the inspection work 10 with slit light 23, an imaging means 25 that converts reflected light from the inspection surface of the inspection work 10 into a video signal, and a control unit 30 that controls the illumination means (22, 24) and the imaging means 25. The control unit 30 includes an image acquisition unit 31 that acquires an inspection image from the imaging means 25, an image processing unit 32 that performs image processing on the inspection image based on the video signal acquired by the imaging means 25, a memory unit 33 that stores a processing program that executes the image processing and data required when the program is executed, an illumination control unit 34 that controls an illumination means consisting of diffuse illumination light 21 and slit light 23 that is irradiated onto the inspection work 10 or a projection device 26 that projects a slit pattern, and a judgment unit 35 that judges defects that have occurred in the inspection work 10 based on the image-processed image. The illumination range of the area illuminator 22 and the illumination range of the slit illuminator 24 overlap, and the imaging means 25 captures a reflected image of the illumination range.

[0015] 2 is a diagram showing the main configuration of the imaging unit 20 of an inspection device used in a second embodiment of the present invention. This differs from the first embodiment in that the illumination means is a projection device 26 that projects a slit pattern that combines an area illumination 21 and a slit illumination 23.

[0016] (2) Inspection work The workpiece 10 to be inspected by the inspection method of the present invention is preferably a strip-shaped object such as a steel plate, carpet, or film having an uneven pattern formed on its outer surface. The inspection method of the present invention can simultaneously inspect for surface unevenness using a light-section method using slit light and for appearance inspection of surface dirt, etc. using area light without switching the illumination light, so that the appearance inspection of the strip-shaped object being transported via the transport means can be performed continuously without switching the illumination means.

[0017] (3) Illumination means The illumination means used in the inspection method of the present invention is an area illumination, a slit illumination, or a projection device that combines area illumination and slit illumination.

[0018] (3-1) Area lighting The area light 22 used in the inspection method of the present invention is a light source that irradiates the inspection surface of the inspection workpiece 10 with diffused illumination light 21. A white light-emitting diode (LED) is preferably used as the light source. Examples of white LEDs include white LEDs that use phosphors, specifically, a combination of a blue LED with a phosphor that emits yellow light, and a combination of an ultraviolet or purple LED with three types of phosphors that emit blue, green, and red light. There are also white LEDs that do not use phosphors, specifically, blue (B), green (G), and red (R) LEDs that are arranged in a single package and emit light simultaneously to obtain white light. The area light 22 illuminates the inspection surface from diagonally above the imaging means 25. As shown in Fig. 3, it is preferable to arrange a plurality of area light sources 22 at symmetrical positions so that the inspection surface has the same luminance conditions.

[0019] (3-2) Slit illumination The slit illuminator 24 used in the inspection method of the present invention is a light source that irradiates the inspection surface of the workpiece 10 with a narrow slit of light 23 for height calculation using the light-section method. When a linear slit of light is irradiated at an angle θ with respect to the optical axis L of the imaging means 25, the slit light moves in accordance with the unevenness of the inspection surface. The relationship between the height (h) of the unevenness and the amount of movement (x) is h = x / tan θ, so with the light-section method, the unevenness (three-dimensional height data) of the workpiece 10 can be calculated by detecting the amount of movement of the slit light contained in the image captured by the imaging means 25. The light-section method (also known as the slit-beam projection method) is a method for obtaining a range image (3D image) by optically scanning an object. It is a type of active measurement method in which a specific reference beam is projected onto the object to capture the image. A range image is a collection of pixels that indicate the 3D positions of multiple parts of the object. In the slit-beam projection method, a slit beam with a linear strip-shaped cross section is used as the reference beam. At a certain point during scanning, a portion of the object is illuminated, and a curved bright line appears on the imaging surface according to the undulations of the illuminated portion. Therefore, by periodically sampling the brightness of each pixel on the imaging surface during scanning, a set of 3D data that identifies the object's shape can be obtained.

[0020] Furthermore, the slit illumination 24 uses monochromatic light of any one of the RGB components. When the RGB components are resolved from an image based on an image in which the area light reflection image and the slit light reflection image from the inspection work captured by the imaging means 25 are superimposed, and the slit light component is extracted, the RGB component used as the slit light is emphasized, facilitating the binarization process of the image before the calculation of the unevenness (three-dimensional data) by the light section method. As the slit illumination 24 used in the inspection method of the present invention, a projection device that projects only various slit patterns such as line patterns, grid patterns, etc. can be suitably used, because the calculation of unevenness (three-dimensional data) using the light-section method can be applied in various directions.

[0021] (3-3) Projection device The projection device 26 used in the inspection method of the present invention is an illumination means that uses the area illumination 22 and slit illumination 24 as an integrated light source, and is, for example, a white LED projection device that forms one of RGB patterns. Various slit patterns, such as line and grid patterns, function as slit light, and patterns other than the slit pattern function as area light. The projection device is not particularly limited. Examples include DLP (Digital Light Processing) projectors and LCD projectors. The projection device is capable of projecting various slit patterns, such as line and grid patterns, at high speed, which shortens the measurement time and is suitable for visual inspection of transported inspection workpieces. Figure 4 shows examples of slit patterns produced by a projection device. (a) shows only a red (R) pattern, and functions as a slit light. (b) shows a red (R) pattern displayed on a white (W) background, and functions as a light that combines area lighting and slit lighting.

[0022] (4) Imaging means The imaging means 25 used in the inspection method of the present invention is provided behind the illumination means. The imaging means 25 is an imaging element using integrated circuits (ICs) that photoelectrically convert reflected light into a video signal. Specifically, it uses a number of photodiodes arranged on a planar silicon substrate, and integrated circuits such as charge-coupled devices (CCDs) or complementary metal oxide semiconductors (CMOSs) are used for transfer. It is an area camera that also includes an optical system that focuses an image of the inspection workpiece on the imaging surface of the solid-state imaging element, and a signal processing circuit that processes the output of the solid-state imaging element to obtain a brightness value for each pixel. A color camera is preferable because the image is decomposed into RGB components.

[0023] (5) Control unit The control unit 30 used in the inspection method of the present invention includes an image acquisition unit 31, an image processing unit 32, a storage unit 33, an illumination control unit 34, and a determination unit 35.

[0024] (5-1) Image acquisition unit The image acquisition unit 31 has a function of acquiring image information of an image (hereinafter referred to as a "superimposed image") based on an image obtained by the imaging means 25 in which the reflected image of the area light 21 and the reflected image of the slit light 23 from the inspection work 10 are superimposed, and storing the image information in the storage unit 33. The image acquisition unit 31 also has a function of controlling the operation of the imaging means 25, such as the timing of imaging, via a general-purpose communication interface such as RS232C or USB (Universal Serial Bus).

[0025] (5-2) Image processing unit The image processing unit 32 has a function of performing various image processing on the video signal (image information) from the imaging means 25. It is configured by an information processing device equipped with a CPU (Central Processing Unit), memory, a display, a storage device such as a hard disk, various interfaces for input and output, etc. It also has a program for executing the inspection method of the present invention, which will be described later, and the CPU executes the program to perform calculations and the like required for the inspection method.

[0026] (5-3) Storage section The storage unit 33 includes a ROM (Read Only Memory) and a RAM (Random Access Memory). The ROM stores various programs, such as an inspection method program, executed by the CPU, and data required when these programs are executed (e.g., images acquired by the imaging means 25). The various programs and data stored in the ROM are loaded into the RAM and executed.

[0027] (5-4) Lighting control unit The illumination control unit 34 has a function of generating a slit pattern to be projected onto the inspection workpiece 10 and storing it in the memory unit 33. It also has a function of transmitting the slit pattern data stored in the memory unit 33 to the projection device via a general-purpose display interface such as DVI (Digital Visual Interface). It also has a function of controlling operations such as turning on / off the light source of the projection device and adjusting the light intensity via a general-purpose communication interface such as RS232C or USB.

[0028] (5-5) Judgment section The judgment unit 35 judges the irregularity defects and stain (brightness unevenness) defects that have occurred in the inspection work 10 based on the judgment information stored in the memory unit 33 for the processed image, such as binarized by the image processing unit 32.

[0029] 2. Inspection method Fig. 5 is a flow chart showing the steps of the appearance inspection method of the present invention, and Fig. 6 is an explanatory diagram showing images processed by the appearance inspection method of the present invention in accordance with the inspection steps. The inspection method of the present invention will be described below with reference to Figs. 5 and 6.

[0030] (1) Acquisition of superimposed video signal Area light 21 is irradiated onto the inspection work 10 from area light 22 consisting of a white LED composed of RGB components, and slit light 23 is irradiated onto the inspection work 10 from slit light 24 consisting of monochromatic light selected from any of the RGB components, and these are simultaneously irradiated onto the irradiation range on the inspection work, and imaging means 25 acquires a video signal in which the area light 21 reflected video signal and the slit light 23 reflected video signal of the inspection work 10 are superimposed, and a "superimposed image" is created (S01). In the first embodiment, the area lighting 22 is a white (W) LED lighting that simultaneously emits three colors: red (R), green (G), and blue (B), and the slit lighting 24 is a projection device 26 that projects only red (R) stripes, while in the second embodiment, the projection device 26 is an integrated area lighting (W) and slit lighting (R) that projects red (R) stripes onto a white (W) background.

[0031] (2) RGB decomposition processing The "superimposed image" is subjected to RGB decomposition processing to create R pixels, G pixels, and B pixels. The pixel components that are the same as the slit illumination are extracted and made into the "slit light component extracted image," and the remaining components are made into the "slit light excluded component extracted image" (S02). For example, if the slit illumination is a red (R) stripe, the image with the R pixel component extracted becomes the "slit light component extracted image," and the image consisting of the remaining G and B pixels becomes the "slit light excluded component extracted image."

[0032] (3) Binarization The "slit beam component extracted image" is binarized using a predetermined threshold as a parameter to create a "slit beam enhanced image" (S03).

[0033] (4) Identifying uneven defects Based on the "slit-beam-enhanced image," unevenness (three-dimensional data) is calculated using the light-section method to determine unevenness defects (S04). Figure 8 is a schematic diagram illustrating a binarized "slit-beam-enhanced image" used for unevenness determination.

[0034] (5) Slit light component luminance correction A correction is performed (S05) to match the brightness of the slit light components (pixels) in the "slit light component extracted image" to the brightness of the slit light components (pixels) in the "slit light excluded component extracted image." This is preprocessing to cancel out the slit light components (pixels) and create a "slit light eliminated image." The "slit light component extracted image" has high brightness because it contains a slit lighting component in addition to an area lighting component, so this is done to match the brightness of the "slit light excluded component extracted image." Specifically, as shown in Figure 7, the brightness of the slit light component (pixel) in the "slit light component extracted image" created from the "superimposed image" by RGB decomposition processing is the sum of the slit light component (pixel) contained in the white light of the area lighting and the slit light component (pixel) of the slit lighting, and therefore is higher than the brightness of the slit light component (pixel) in the "slit light component removed image." For this reason, brightness correction is required before RGB composition processing. In FIG. 7, the brightness of the AA′ cross section is shown schematically.

[0035] (6) RGB composition processing The brightness-corrected "slit-beam component extracted image" and "slit-beam excluding component extracted image" are combined to create a "slit-beam eliminated image" consisting of R, G, and B pixels (S06).

[0036] (7) Binarization The "slit light component removed image" is binarized using a predetermined threshold as a parameter (S07). Fig. 9 is a schematic diagram illustrating the binarized "slit light removed image" used for determining stains.

[0037] (8) Dirt defect judgment Based on the binarized "slit light erased image", a stain (uneven brightness) defect is determined (S08). [Industrial Applicability]

[0038] The present invention provides a visual inspection method for simultaneously inspecting unevenness defects and dirt defects on an inspection workpiece. [Explanation of symbols]

[0039] 100 Visual inspection equipment 10 Inspection work 20 Imaging unit 21 Diffused Light 22 Area Lighting 23 Slit Light 24 Slit illumination 25 Imaging means 26 Projection device 30 Control Unit 31 Image acquisition unit 32 Image processing section 33 Storage section 34 Lighting control unit 35 Judgment section

Claims

1. An appearance inspection method using an appearance inspection device including an imaging means for imaging an inspection surface of an inspection workpiece, an illumination means consisting of area illumination and slit illumination whose irradiation ranges on the inspection surface overlap, and an image processing means for processing an image based on a video signal acquired by the imaging means, A step of simultaneously irradiating the inspection work with white diffuse light composed of RGB components from the area lighting and monochromatic slit light selected from either the RGB components from the slit lighting, and acquiring a video signal in which the area light reflection video signal and the slit light reflection video signal of the inspection work are superimposed by the imaging means to create a superimposed image; a step of subjecting the superimposed image to RGB decomposition processing to generate a slit light component extracted image in which the same component as the slit illumination is extracted, and a slit light excluded component extracted image; a step of binarizing the slit beam component extracted image to generate a slit beam enhanced image; A step of inspecting unevenness of an inspection workpiece by a light section method based on the slit light enhanced image; performing luminance correction on the slit beam component extracted image to generate a slit beam component corrected image; a step of performing RGB synthesis processing on the slit light excluded component extracted image and the slit light component corrected image to generate a slit light removed image; A step of inspecting unevenness of an inspection workpiece based on the slit light erased image; A visual inspection method comprising:

2. 2. The appearance inspection method according to claim 1, wherein the illumination means is a projection device which projects a slit pattern, and is an illumination means which combines area illumination and slit illumination.

3. An appearance inspection device comprising: an imaging means for imaging an inspection surface of an inspection workpiece; an illumination means consisting of area illumination and slit illumination whose illumination ranges on the inspection surface overlap; and an image processing means for processing an image based on a video signal acquired by the imaging means, The image processing means obtains an image signal in which the area light reflection image signal and the slit light reflection image signal of the inspection work are superimposed by the imaging means, and creates a superimposed image; The superimposed image is subjected to RGB decomposition processing to generate a slit light component extraction image in which the same component as the slit illumination is extracted, and a slit light excluded component extraction image; The slit light component extracted image is subjected to a binarization process to generate a slit light enhanced image; Inspecting the unevenness of the inspection workpiece by a light section method based on the slit light enhanced image; performing luminance correction on the slit light component extracted image to generate a slit light component corrected image; a slit-light-eliminated image is generated by subjecting the slit-light-excluded component extracted image and the slit-light component corrected image to RGB synthesis processing; A processing device including an execution program for inspecting unevenness of an inspection workpiece based on the slit light-eliminated image; 1. A visual inspection apparatus comprising:

4. 4. The visual inspection apparatus according to claim 3, wherein said illumination means is a projection device for projecting a slit pattern, and is an illumination means combining area illumination and slit illumination.

Images