JP2000111491A - Appearance inspection apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize an appearance inspection apparatus by which, when at least any one out of the end face, the outside-diameter face and the inside- diameter face of a cylindrical workpiece (a work) is inspected, a well visible continuous arc-shaped flaw can be detected without lowering an acceptance rate. SOLUTION: A part or the whole range (a) of a binarized image which expresses an imaged face to be inspected is scanned in the radial direction (b). Thereby, the existence of a defect in scanning lines is judged. The number of times in which the scanning lines with the detected defect appear is counted. The quality of a work is judged on the basis of the counted number of times. When a chamfered flaw, rust, a casting surface residue or the like exists on a cylindrical workpiece, the workpiece is scanned in the radial direction. When an arc-shaped scratch flaw or a concentric circle-shaped flaw, along the circumferential direction, which is generated in a working operation exists, the workpiece is scanned in the circumferential direction. Thereby, the flaw can be detected surely.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a visual inspection device, and more particularly to a visual inspection device capable of detecting a surface defect of an object to be inspected and judging front and back.

[0002]

2. Description of the Related Art Cylindrical workpiece (hereinafter referred to as "work")
There is known an appearance inspection device for inspecting the appearance of upper and lower end surfaces and side surfaces. This appearance inspection apparatus captures an inspection surface with a camera, converts the image surface into an image signal, binarizes the image signal, and outputs the image signal as a monochrome pixel signal.

[0003] Inspection and determination of a work is performed by a known determination procedure, for example, by extracting a primary feature amount of the black and white pixel signal.

[0004]

(1) As shown in FIGS. 1 (a) and 1 (b), there is a case where a processing flaw is continuously formed in a circumferential direction on an inspection surface of a work. Since such a flaw is very thin and thin, stable detection is difficult with the conventional method for the following reasons. If the threshold value for binarizing such flaws is increased and black pixels are sought to be clearly formed, rough surfaces of non-defective products, deposits such as oil and grease are similarly converted to black pixels, and non-defective products also have defects. Since the judgment is made, the pass rate decreases.

[0005] Further, if the depth of flaws and the unevenness of illumination overlap, it becomes more and more difficult to form uniform and clear black pixels, and only binary images that are discontinuous and cut off can be obtained. Therefore, the present invention solves the above-mentioned problem, and realizes a visual inspection device capable of detecting continuous circumferential scratches often seen on a cylindrical workpiece without lowering a pass rate. Aim.

(2) Since the front and back of the work are different and both sides are often inspected, if the work is not aligned on either side, it will lead to erroneous determination. Therefore, in order to perform a visual inspection by image processing, it is necessary to recognize the front and back by the image processing device itself without using an expensive alignment device for aligning the front and back end surfaces of the work.

However, for example, in the case of a ball bearing,
Considering the situation where the front end face is made of a sealing material (metal, rubber, etc.) and the back end face is unsealed or translucent and the ball is visible, it takes a long time to make a determination by conventional image processing (pattern matching). Not only (tens of ms
ec), and if oil or the like adheres to the surface, accurate judgment cannot be made.

SUMMARY OF THE INVENTION Accordingly, the present invention provides an appearance inspection apparatus capable of determining the front and back of a work and determining the shortage of components by simpler image processing when inspecting a work in which only one end surface is sealed. With the goal.

[0009]

The appearance inspection apparatus of the present invention inspects at least one of an end face, an outer diameter face, and an inner diameter face of a cylindrical workpiece. By scanning a part or the whole of the binarized image representing the inspection surface in the radial direction or the circumferential direction, the presence or absence of a defect in the scanning line is determined, and the number of times the scanning line in which the defect is detected appears continuously. Is counted, and the quality of the cylindrical workpiece is determined based on the counted number (claims 1 and 2).

According to the above arrangement, the presence or absence of a defect in the radial or circumferential scanning line is determined, and the pass / fail determination is made based on the number of times the scanning line in which the defect is detected appears continuously. In particular, chamfer scratches and rust on cylindrical workpieces,
If there are black scales, etc., scan in the radial direction, and if there are arcuate scratches and concentric scratches along the circumferential direction that occur during processing, scan in the circumferential direction, A flaw can be reliably detected.

Further, as compared with the measurement of the primary characteristic amount, the processing is to capture only the features along the line, so that the processing time is about one tenth of those (several msec). The visual inspection device of the present invention inspects an end face of a bearing, scans a part or the whole of an imaged inspection surface in a radial direction, and obtains pixel density along a scanning line. The value corresponding to the brightest density is obtained, and the presence or absence of the front and back of the bearing or the presence or absence of a component is determined based on the value (claims 3 and 4).

According to this configuration, for example, when an image of a sealed end face of a bearing in which only one end face is sealed is taken, the density of the image is relatively dark, and the end face on which the rolling element on the opposite side is seen is taken. In this case, since the image density is partially bright due to the gloss of the rolling elements, it is possible to determine the front and back of the bearing, the number of the rolling elements, and the presence or absence of the retainer.

Further, even in the case where foreign matter such as oil or grease adheres, the present invention, which makes a determination based on the brightest density, can make a highly reliable determination. Furthermore, compared to performing the determination by the conventional image processing (pattern matching), the processing takes only the features along the line, so that the processing time is short. About 1/10 of them (several mse
c).

[0014]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. First, the configuration of the appearance inspection device will be described. As shown in FIG. 2, the visual inspection apparatus includes an image processing unit 1, a monitor 2, an illumination unit 3, a diffusion plate 3a, a camera 4, and a holder 5 for holding a work W. Here, the workpiece W may be any workpiece as long as it is a cylindrical workpiece, but in the embodiment of the present invention, a ball bearing is assumed.

The work 5 with the inspection surface facing upward is placed on the holder 5. The illumination unit 3 is configured by arranging a large number of illumination light sources such as LEDs in an annular shape, and is installed above the center axis of the holder 5. The diffusion plate 3a is formed by forming a diffuser such as ground glass into a hollow disk shape. The camera 4 is installed above the center axis of the holder 5 and the lens 42 and the CC
And a D camera 41. The focus of the camera 4 is always set on the inspection surface (end surface A, outer diameter surface C, inner diameter surface D, etc.).

The image processing section 1 takes in an image signal of the camera 4, converts it into an image signal, and performs image processing described later. The monitor 2 is a display device such as a CRT for displaying the image. FIG. 3 shows an image displayed on the monitor 2 of the visual inspection apparatus. In FIG. 3, the end face A of the work W is shown on the screen of the monitor 2.

FIG. 4 shows the configuration of an appearance inspection apparatus for inspecting the outer diameter surface C of the work W. In this case, the work W
A reflector 6 having a conical mirror surface is arranged so as to surround the work W. When the outer diameter surface C of the work W is inspected by the appearance inspection apparatus having this configuration, a donut-shaped image similar to FIG. FIG.
2 shows the configuration of the appearance inspection device for inspecting the inner diameter surface D of the work W. In this case, the illumination unit 3 is installed below the center axis of the holder 5, and the light hitting the inner diameter surface D of the work W is observed by the camera 4. Also when the inner diameter surface D of the work W is inspected by the appearance inspection apparatus having this configuration, a hollow donut-shaped image appears as in FIG.

Hereinafter, an image processing method related to the present invention will be described. (1) Detection of Scratches First, binarization is performed using a predetermined threshold based on an image signal acquired by the image processing unit 1. And
As shown in FIG. 6, the generation range a of the scratch on the inspection surface is specified. The occurrence range a is empirically determined as a range in which the frequency of occurrence of flaws is high. In FIG. 6, it is a part shown concentrically. Of course, the generation range a may be set for the entire inspection surface.

Next, the selected generation range a is scanned along the radial direction (see FIG. 6B). The interval between these scans is not limited, but is selected, for example, every 1 °.
It is determined whether or not a flaw is detected in each of the scans when these scans are performed in the entire circumference. The judgment method is
For example, the determination is performed based on whether or not a black pixel appears continuously a predetermined number of times (for example, twice). The determination result is as shown in Table 1.

[0020]

[Table 1] Then, the number of continuous detections c in the circumferential direction (the case where c = 5 is shown in Table 1) is obtained, and the presence or absence of a flaw is determined based on whether the number is greater than a predetermined number. Alternatively, it is also possible to determine the presence or absence of a flaw by determining the total number of detections and determining whether the number is greater than a predetermined number. It should be noted that, based on the total number of scratched scanning lines,
Surface roughness can also be examined.

Although not shown, scanning is performed a plurality of times while changing the radius along the circumferential direction, and when these scannings are performed in the entire range a, it is determined whether or not a flaw is detected in each scanning. It is also possible to determine the presence or absence of a flaw by determining the number of continuous detections of circumferential flaws and determining whether the number is greater than a predetermined number. This makes it possible to detect even small flaws. The surface roughness can also be checked based on the total number of scans with flaws.

(2) Detection of the front and back of the work end face In this measurement, the purpose is to detect the front and back of the work end face, the number of balls, and the presence / absence of the cage. Therefore, the inspection mode is limited to the work end face inspection shown in FIG. Therefore, the inspection of the outer surface of the work and the inspection of the inner surface shown in FIGS. 4 and 5 are excluded. This detection is performed based on a density image signal captured by the camera 4 (a binary image is not used).

In the image of the work surface, as shown in FIG. 7, an image of a seal such as a synthetic resin appears between the inner diameter portion and the outer diameter portion. Also, in the binarized image on the back surface of the work, as shown in FIG. 8, an image of a shadow of a ball (rolling element) is shown together with an image of a bearing retainer. The image of the seal is relatively dark, and the image of the back surface is bright in the portion where the ball comes out. Therefore, as shown in FIG. 9, the determination region d sandwiched between concentric circles on the inspection surface is limited, and the limited determination region d is scanned in the radial direction (see e in FIG. 9). Thereby, the density data of the pixels on the scanning line is obtained. The interval between scans is not limited,
For example, every 1 °.

Based on the brightest data among the acquired density data of one sample of the work, the front and back of the work are determined by determining whether the data is higher or lower than a predetermined threshold value.
Further, when bright data appears in a lump, the number of balls is determined based on the number of lump. Further, the presence or absence of the retainer is determined by extracting the image density of the retainer with a predetermined threshold value.

[Brief description of the drawings]

FIG. 1A is a view showing a thin arc-shaped processing flaw on an inspection surface of a work, and FIG. 1B is a view showing a circumferential processing flaw on an inspection surface of the work.

FIG. 2 is a diagram illustrating a configuration of a visual inspection device of the present invention.

FIG. 3 is a diagram showing an image of an inspection surface displayed on a monitor 2.

FIG. 4 is a configuration diagram of an appearance inspection device when inspecting an outer diameter surface C of a work W;

FIG. 5 is a configuration diagram of a visual inspection device when inspecting an inner diameter surface D of a work W.

FIG. 6 is a view showing a range a in which an arc-shaped scratch and a circumferential scratch on the inspection surface are generated.
FIG. 3 is a diagram showing a radial scanning direction b.

FIG. 7 is a diagram showing an image of a work surface displayed on a monitor 2.

FIG. 8 is a diagram showing an image of the back surface of the work projected on the monitor 2.

FIG. 9 is a diagram showing an inspection surface determination area d and a radial scanning direction e.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image processing part 2 Monitor 3 Lighting part 3a Diffusion plate 4 Camera 5 Holder A End surface C Outer diameter surface D Inner diameter surface W Work

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Kazuaki Yamada 3-5-8, Minamisenba, Chuo-ku, Osaka-shi Koyo Seiko Co., Ltd. (72) Inventor Hitoshi Morikawa 2-34, Minamiuematsucho, Yao-shi, Osaka F-term (reference) in Machinery Co., Ltd. CA16 CB02 CB06 CB12 CB16 CC01 CE12 DA03 DB02 DB05 DB09 DC03 DC22

Claims (4)

[Claims] 1. An appearance inspection apparatus having means for imaging at least one of an end surface, an outer diameter surface, and an inner diameter surface of a cylindrical workpiece as an inspection surface, wherein a signal representing the imaged inspection surface is converted into a binary signal. Means for determining the presence or absence of a defect in a scanning line by scanning a part or the whole of a binarized image in a radial direction, and counting the number of times a scanning line in which a defect is detected appears continuously. A determining means for determining the quality of the cylindrical workpiece based on the count number. 2. An appearance inspection apparatus having means for imaging at least one of an end surface, an outer diameter surface, and an inner diameter surface of a cylindrical workpiece as an inspection surface, wherein a signal representing the imaged inspection surface is converted into a binary signal. Means for judging the presence or absence of a defect in a scanning line by scanning part or all of the binarized image in the circumferential direction; and counting the number of times the scanning line in which the defect is detected appears continuously. A determining means for determining the quality of the cylindrical workpiece based on the count number. 3. An appearance inspection apparatus having means for imaging an end surface as an inspection surface of a bearing having only one end surface sealed, wherein part or all of the imaged inspection surface is scanned in a radial direction, and scanning is performed. Means for acquiring the density of pixels along the line, and determination means for determining a value corresponding to the brightest density among the pixel densities of the scanned scanning line, and determining the front and back of the bearing based on the value. An appearance inspection apparatus characterized by having: 4. An appearance inspection apparatus having means for taking an image of an end surface as an inspection surface of a bearing having only one end surface sealed, wherein a part or all of the imaged inspection surface is scanned in a radial direction, and scanning is performed. Means for acquiring the density of the pixels along the line; and obtaining the value corresponding to the brightest density among the pixel densities of the scanned scanning line, and based on the value, the number of rolling elements of the bearing or the presence or absence of the cage. A visual inspection apparatus, comprising: a determination unit that determines the visual inspection.