JPH10332598A - Automatic visual inspection apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an automatic visual inspection apparatus by which the defect part in the appearance on the surface of an object can be detected properly and easily. SOLUTION: An apparatus is constituted so as to be provided with a light source 2 which shines light at the surface of an object 1 to be inspected, with a line sensor 3 by which the surface of the object 1 to be inspected is scanned, by which reflected light from the irradiated light is received from the surface and which detects the intensity of the reflected light and with an image processor 4 which processes the output of the line sensor 3 and which detects the defect part in the appearance of the object 1 to be inspected. The maximum output voltage of the line sensor 3 is designated as (a), the maximum input voltage in the image processing A/D conversion part of the image processor 4 is designated as (b), the light and shade resolution of the image processor 4 is designated as (c), and the maximum voltage fluctuation width in the output voltage of the line sensor 3 is designated as (d). Then, (a)=(b), and the threshold value of the judgment of the defect part is at ±1/2 d/(a/c)}.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an object to be inspected,
For example, the present invention relates to an automatic appearance inspection apparatus that detects an appearance defect of an electrophotographic photosensitive member used for a copying machine or a printer that is an electrophotographic application product.

[0002]

2. Description of the Related Art In recent years, organic photoconductors have been widely used as electrophotographic photoconductors used as image forming members in copying machines and printers which are electrophotographic products. Such an organic photoreceptor is usually manufactured by forming a photosensitive layer mainly composed of an organic material on the outer peripheral surface of a conductive cylindrical support by a coating method. Further, if necessary, an undercoat layer is provided between the support and the photosensitive layer by a coating method, and a protective layer is provided on the surface of the photosensitive layer.

In such a photoreceptor, a physical defect such as a scratch or a chemical defect such as an oxide exists on the surface of the support, a photosensitive layer formed on the support, or an undercoat. If the layer or the protective layer has a defect such as a scratch, uneven coating, or a mixture of foreign matter, the image processing function as a photoconductor is impaired, and a defect occurs in an obtained image. Therefore, it is necessary to eliminate the photoconductor having such a defect.

When the surface of a photoreceptor having such a defect is irradiated with light of a constant intensity and the reflected light is observed, the intensity of the reflected light from the defective portion is determined according to the type of the defect. Stronger or weaker than. Focusing on this, in the final step of photoconductor production, an outer appearance inspection of irradiating the outer peripheral surface of the photoconductor and observing reflected light has been performed, and a photoconductor having a defect has been selected and removed. .

Conventionally, a visual inspection by an inspector has been adopted as the above-mentioned appearance inspection. However, since the visual inspection is a sensory inspection, a change in the inspection level, erroneous determination, oversight, and the like occur to some extent. Inevitably, the inspection level must be strict or the inspection must take a lot of time to prevent defective products from being overlooked. This is a high-risk and high-cost inspection. .
In addition, the inspection method was so concerned that the degree of eye fatigue of the inspector was large and the health was concerned.

[0006] As a countermeasure, the development of an automatic appearance inspection apparatus has been advanced. One effective automatic inspection method is to irradiate the photoreceptor surface with light, receive the reflected light with a sensor that scans the photoreceptor surface, detect the reflected light intensity, and process the output with an image processor. A method for detecting an appearance defect is known. As a sensor for scanning the surface of the photoconductor, a CCD line sensor is preferably used.

The image defect appears as a portion having a higher density (dark defect), a portion having a lower density (bright defect), or uneven density, as compared with the image density of a normal portion on the image. When the photoconductor is irradiated with light, abnormalities on the surface of the photoconductor corresponding to high-density image defects have less light reflection compared to the normal parts.
The output of the line sensor becomes lower, and the abnormal portion of the photoreceptor surface corresponding to the image defect with low density has more light reflection than the normal portion, and the output of the CCD line sensor becomes higher. Therefore,
The output of the CCD line sensor is processed by the image processor, and the output swings higher or lower than the output of the normal part, whereby an abnormal part can be detected.

The automatic appearance inspection apparatus as described above is
The present invention is not limited to the visual inspection of the photoreceptor, but can be effectively applied to the visual inspection of the surface of a similar object.

[0009]

In the above-mentioned automatic appearance inspection apparatus, the line sensor photoelectrically converts the received reflected light, amplifies the converted electric signal by an amplifier circuit, and outputs the amplified electric signal. At that time, the noise component is also amplified. The output processed by the image processor using the output of such a line sensor as an input also includes a noise component. Therefore, if a defective portion is determined based on the output, an erroneous determination that a non-defective product is a defective product occurs. Therefore, it is necessary to set a "threshold" for the determination in order to eliminate the noise component and eliminate the erroneous determination. Since this threshold affects the accuracy of the inspection, it is important to determine it appropriately.

[0010] The present invention has been made in view of the above points, and has as its object to provide an automatic appearance inspection apparatus in which an appropriate threshold value can be easily determined.

[0011]

According to the present invention, there is provided a light source for irradiating light to a surface of an object to be inspected, and a light source for scanning the surface and receiving reflected light of the irradiated light from the surface. A line sensor for detecting the intensity of the line sensor, and an image processor for processing the output of the line sensor to detect a defective portion of the appearance, the maximum output voltage of the line sensor is a, When the maximum input voltage of the image processing A / D converter of the image processor is b, the light / dark resolution of the image processor is c, and the maximum voltage fluctuation width of the output voltage of the line sensor is d, a = b In addition, the problem is solved by an automatic appearance inspection apparatus that sets a threshold value for determining a defective portion to ± 1/2 · (d / (a / c)).

The maximum voltage fluctuation width d of the output voltage of the line sensor is the maximum voltage of the output voltage of the line sensor when light having an intensity of 80% of the light having the output of the line sensor as the maximum output voltage a is received. It is good to set the fluctuation range.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described by taking an electrophotographic photosensitive member as an example. However, the present invention is not limited to this, and the same applies to the appearance inspection of the surface of an object. Can be applied effectively. The shape of the inspection object is not limited to the cylindrical shape. FIG. 1 is a schematic diagram showing a configuration of an example of an automatic visual inspection apparatus according to the present invention.
1A is a side view, and FIG. 1B is a front view. A light source 2 (for example, a fluorescent lamp) for uniformly irradiating light to the outer peripheral surface of the cylindrical photoreceptor 1 in a band shape along the axial direction thereof is disposed,
A CCD line sensor 3 is arranged so as to focus on a position where the illuminance is highest on the irradiation surface of the light source 2 of the photoconductor 1. Reference numeral 4 denotes an image processor which receives the output of the CCD line sensor 3 and processes the signal, and reference numeral 5 denotes a drive motor for rotating the photoreceptor 1 about its cylindrical axis. With the apparatus having such a configuration, light is radiated from the light source 2 to the outer peripheral surface of the photoreceptor 1 in a band shape along the axial direction, and the reflected light is CCD.
The light intensity is received by the line sensor 3 and the output is processed by the image processor 4 to detect a defect. Photoconductor 1
Is rotated around the cylindrical axis by the driving motor 5, the entire outer peripheral surface of the photoconductor 1 is scanned by the CCD line sensor 3, and the entire surface of the photoconductor can be easily inspected.

FIG. 2 is a diagram showing an example of an output image of the image processor having the above configuration. In FIG. 2, the horizontal axis represents the time axis, and the vertical axis represents the gradation of the output of the image processor, which is obtained by processing the output of the CCD line sensor when receiving the reflected light from the normal portion of the photosensitive member surface. The reference value is used as a reference value, and the gradation value obtained by processing the output of the CCD line sensor when receiving the reflected light from each part of the photoconductor surface by the image processor is shown. Defects having a higher density than the normal portion on the image appear in the direction of the reference value (-), and defects having a lower density appear in the direction of the plus (+). Since the output slightly fluctuates according to the noise component of the output of the CCD line sensor, a threshold value for eliminating this is set, and if the output deviates more than that (a, b, c in the figure), it is detected as a defect.

In the apparatus having the structure as shown in FIG.
The maximum output voltage a of the line sensor 3 is adjusted so that the maximum input b of the image processing A / D converter of the image processor 4 becomes equal. Next, the maximum voltage fluctuation width (ie, noise component) d of the output voltage of the CCD line sensor 3 is determined.
What is necessary is just to measure the voltage fluctuation width of the output voltage of the CCD line sensor 3 when irradiating light with the intensity that maximizes the output voltage of the CCD line sensor 3. When the output voltage of the CCD line sensor 3 becomes maximum, The voltage fluctuation width cannot be measured. Therefore, the voltage fluctuation width of the output voltage when the light as intense as possible is irradiated within the measurable range of the output voltage fluctuation width is measured. Realistically, the output voltage of the CCD line sensor 3 has a maximum intensity 80a.
It is preferable to measure the voltage fluctuation of the output of the CCD line sensor 3 when continuously receiving the light having the intensity of about%, and determine the maximum value as the maximum voltage fluctuation width. Since the maximum output voltage of the CCD line sensor 3 and the maximum input voltage of the image processor are equal, the maximum voltage fluctuation width of the image processor is also d. Assuming that the light / dark resolution of the image processor 4 is c (gradation), the gradation width e corresponding to the maximum voltage fluctuation width d is d / (a /
c). By setting the threshold value of the output of the automatic visual inspection apparatus to ± e / 2, voltage fluctuation (noise component) of the CCD line sensor 3 can be removed, and defects can be accurately detected. Becomes

Example 1 Using the apparatus having the configuration shown in FIG. 1, an external appearance inspection of a cylindrical photosensitive member having an outer diameter of 30 mm and an effective length of 120 mm is performed. CCD
As the line sensor, a sensor having 2000 pixels (2,000 CCD elements) and a maximum output voltage a of 5 V is used. The maximum output voltage of this CCD line sensor is 5
When the maximum fluctuation voltage d when irradiating light having an intensity of 80% of the intensity which becomes V was measured with an oscilloscope, it was 390 m.
V. Further, as the image processor, the light and dark resolution c
Is 8 bits (256 gradations), and the maximum input voltage b is adjusted to be equal to the maximum output voltage 5V of the CCD line sensor. Therefore, the gradation width e of the maximum fluctuation voltage of the image processor is 390 mV / (5000 mV / 2
At 56), about 20 gradations are obtained.

With such an apparatus, while operating the CCD line sensor at 2 MHz, the photosensitive member is rotated once at a speed of 30 rpm to scan the entire outer peripheral surface of the photosensitive member, and the output is input to an image processor for processing. Then, the presence or absence of a defect is detected from the output image. For the photoreceptor having a good image and the photoreceptor having an image defect (dark defect (large), dark defect (small), bright defect (large), bright defect (small), density unevenness), the threshold value (± e /
2) was changed to ± 8, ± 10, ± 12 and inspected.

Table 1 shows the results. In Table 1, ×
The mark indicates that the device was determined to be defective, and the mark ○ indicates that the device was determined to be good.

[0019]

[Table 1]

As shown in Table 1, the pass / fail judgment threshold value is set to ± 10 which is 1/2 of the gradation width of the maximum fluctuation voltage of the image processor corresponding to the maximum voltage fluctuation width of the CCD line sensor.
And the erroneous determination is the least.

[0021]

According to the present invention, a light source for irradiating light to a surface of an object to be inspected, and a line sensor for scanning the surface and receiving reflected light of the irradiated light from the surface to detect reflected light intensity And an image processor for processing the output of the line sensor to detect a defect in the appearance of the object to be inspected, wherein the maximum output voltage of the line sensor is a, The maximum input voltage of the image processing A / D converter is set to b, the light / dark resolution of the image processor is set to c,
Assuming that the maximum voltage fluctuation width of the output voltage of the line sensor is d, a = b, and the threshold for determining a defective portion is ±
1/2 (d / (a / c)). By using such an apparatus, it is possible to easily and automatically detect the appearance defect of the inspection object with high accuracy.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a configuration of an example of an apparatus according to the present invention. FIG. 1 (a) is a side view, and FIG. 1 (b) is a front view.

FIG. 2 is a diagram showing an example of an output image of the device according to the present invention;

[Explanation of symbols]

 Reference Signs List 1 photoconductor 2 light source 3 CCD line sensor 4 image processor 5 drive motor

Claims (2)

[Claims] A light source for irradiating light to a surface of the inspection object;
A line sensor that scans the surface and receives reflected light of the irradiation light from the surface to detect reflected light intensity; and an image processor that processes an output of the line sensor to detect a defect in appearance. The maximum output voltage of the line sensor is a, the maximum input voltage of the image processing A / D converter of the image processor is b, the light / dark resolution of the image processor is c, When the maximum voltage fluctuation width of the output voltage is d, a = b, and
± 1/2 · (d / (a / c))
An automatic visual inspection device characterized by the following. 2. The maximum voltage fluctuation width d of the output voltage of the line sensor is set to the maximum output voltage a of the output voltage of the line sensor. 2. The automatic visual inspection device according to claim 1, wherein the maximum voltage fluctuation width is set.