JPH08304291A - Method and system for inspecting defect in electrophotographic photosensitive body - Google Patents

Abstract

PURPOSE: To obtain method and system for inspecting both dark and light defects in an electrophotographic photosensitive body surely and simultaneously even for different types of photosensitive bodies. CONSTITUTION: The system for inspecting the defect in an electrophotographic photosensitive body comprises a light source 4 for irradiating the surface of a cylindrical photosensitive body 1 with light in the axial direction thereof, a CCD camera 2 for receiving the light reflected on the surface of photosensitive body 1 and detecting the intensity thereof, a section 3 for processing the output signal therefrom, and means for driving the photosensitive body 1 to turn about the axis thereof. The system further comprises an optical sensor element 5 for monitoring the light reflected on the normal part of photosensitive body, and an automatic dimmer 6 for receiving the output therefrom and controlling the quantity of light of the light source 4. The defect is inspected under a condition where the quantity of light of the light source 4 is controlled by the automatic dimmer 6 on an output from the optical sensor element 5 such that the reflected light from the normal part of photosensitive body has the central output gradation level of the CCD camera 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a defect inspection machine and a defect inspection method for an electrophotographic organic photoconductor used in a copying machine or a printer for electrophotographic application products.

[0002]

2. Description of the Related Art In recent years, organic photoconductors have rapidly become popular as electrophotographic photoconductors. Such an organic photoreceptor is usually manufactured by forming a photosensitive layer made of an organic material on the outer peripheral surface of a conductive cylindrical support by a coating method. Furthermore, if necessary, an undercoat layer may be provided between the support and the photosensitive layer, or a protective layer may be provided on the surface of the photosensitive layer.

In such a photoreceptor, there are physical defects such as scratches and stains, chemical defects such as oxides on the surface of the support, a photosensitive layer formed on the support, or a lower layer. If defects such as scratches, coating unevenness, and mixture of foreign matters are present in the coating layer and the protective layer, the image processing function of the photoconductor is deteriorated, and defects occur in the obtained image. For this,
In the final step of the photoconductor manufacturing line, the presence or absence of defects as described above is inspected by visual inspection.

As such a defect inspection, a visual inspection has been conventionally performed by an inspector. However, since the visual inspection is a sensory inspection, variation in inspection level, erroneous judgment, oversight, etc. may occur to some extent. Inevitably, for that reason, it was necessary to prevent the defective products from being mixed with the good products by tightening the inspection level and taking sufficient time for the inspection, which was a risky and costly inspection. .

As a countermeasure against this, development of an automatic inspection machine is in progress. As one of them, paying attention to the fact that the intensity of the reflected light is different between the normal part and the defective part of the photoconductor when the light is irradiated to the photoconductor outer surface and the reflected light is observed. A method is known in which light is irradiated in a band shape along an axial direction, the reflected light is received by a line sensor, the light intensity is detected, and the output is processed to detect a defect. By rotating the photosensitive member once in the axial direction, the entire peripheral surface of the photosensitive member is scanned, and the entire surface of the photosensitive member can be easily inspected. A fluorescent lamp is preferably used as the light source because the photoconductor has a cylindrical shape and is relatively elongated, and a CCD camera is used as the sensor because the difference in shade of light reflected from the photoconductor corresponds to a defect. The line sensor of is preferably used.

The image defect appears as a dark (dark) portion or a light (bright) portion in the image as compared with the density of a normal portion. When a photoconductor is irradiated with light, a photoconductor defect that appears as a dark portion on the image (hereinafter referred to as a dark defect)
Has less light reflection than the normal part, and the output (luminance level) of the CCD camera is low. Further, a photoconductor defect (hereinafter referred to as a light defect) that appears as a portion having a low density on the image
The amount of reflected light is larger than that in the normal part, and the output of the CCD camera is higher. Therefore, the defect of the photoconductor can be detected by swinging the output of the CCD camera higher or lower than the output of the normal surface of the photoconductor.

FIG. 2 shows an example of a defect detection signal obtained by processing the output of the CCD camera. In FIG. 2, the horizontal axis is the time axis, and the vertical axis is the signal obtained by processing the output of the CCD camera when receiving the reflected light from the surface of the normal portion of the photoconductor as the reference value 0. CC from each part of the surface
4 shows fluctuations (amplitude) in the ± direction of a signal obtained by processing the output of the D camera. In the figure, the peak points a and b of the waveform swung in the-direction correspond to dark (dark) defects, and the peak points c and d of the waveform swung to the + direction correspond to thin (bright) defects. Indicates a defect having a clearer shade difference than the normal portion, and b and d represent defects having a smaller shade difference than the normal portion. As described above, since the defect is detected by the variation in the ± direction with respect to the reference value 0, the reference value 0 is the center value of the gradation of the brightness level of the CCD camera in order to detect both the dark and light defects with high sensitivity. Must match. Further, according to the actual measurement, some signal fluctuations are observed even in a normal area where there is no defect on the surface of the photoconductor, and therefore, in reality, the judgment level (a threshold value in the ± direction with respect to the reference value 0) is shown. (Indicated by a broken line) is set, and if it swings more than that level, it is judged as a defect.

[0008]

By the way, the photosensitive material and the sensitivity of the photosensitive member are selected according to the performance of the copying machine or the printer in which the photosensitive member is mounted, and the color and density of the surface of the photosensitive member are changed correspondingly. Come on. When the color or density on the surface of the photoconductor changes in this way, the intensity of the reflected light on the surface of the photoconductor changes, and the brightness level of the CCD camera when the reflected light is received changes. That is, when the color of the surface of the photoconductor is dark, the brightness level becomes low, and the brightness level of the normal portion shifts to a position lower than the central value of the gradation of the brightness level of the CCD camera. The reference value 0 in FIG. 2 described above becomes lower than the center value of the gradation, and therefore relatively thin defects are easy to detect, but dark defects are hard to detect. On the contrary, when the color of the surface of the photoconductor is light, the brightness level becomes high, and the brightness level of the normal part shifts to a position higher than the central value of the gradation of the brightness level of the CCD camera. The reference value 0 in FIG. 2 described above becomes higher than the central value of the gradation, and therefore relatively dark defects are easy to detect, but thin defects are hard to detect.

The present invention has been made in view of the above points, and even if the color or density of the surface changes depending on the type of the photoconductor, a defect inspection capable of detecting both dark and thin defects with equal sensitivity. An object of the present invention is to provide a machine and a method for accurately detecting a defect using the machine.

[0010]

In order to solve the above-mentioned problems, in the present invention, a light source for irradiating light in the cylindrical axis direction of the outer peripheral surface of a cylindrical photosensitive member and a reflected light by scanning the irradiation surface. A surface scanning sensor that receives light to detect in-plane light intensity, a signal processing unit that processes the output of the sensor to detect defects on the surface of the photoconductor, and rotationally drives the photoconductor around a cylindrical axis. A defect inspection machine for an electrophotographic photosensitive member having a means, and an optical sensor element for receiving the reflected light, and an automatic dimmer for dimming the light amount of the light source according to the output of the optical sensor element. To do.

Then, using such an inspection machine, the outer peripheral surface of the photoconductor is irradiated with light from a light source, the reflected light of the normal part of the photoconductor is monitored by an optical sensor element, and the output thereof is used for automatic light control. While controlling the amount of light from the light source by the device so that the reflected light from the normal part of the photoconductor becomes the center value of the gradation of the brightness level of the surface scanning sensor, while rotating the photoconductor, the light source is applied to the outer peripheral surface of the photoconductor. The surface of the photoconductor is scanned by the surface scanning sensor, the reflected light within the surface is received, and the output of the surface scanning sensor that detects the light intensity is processed by the signal processing unit for defect inspection. I will.

[0012]

The color and density of the surface of the photoconductor changes depending on the material constituting the photoconductor, and the intensity of the reflected light on the surface of the photoconductor changes correspondingly, but the intensity of the reflected light also changes depending on the light amount of the light source. That is, when the light amount of the light source that irradiates the outer peripheral surface of the photoconductor decreases, the brightness level of the reflected light of the normal photoconductor portion of the CCD camera decreases, and conversely when the light amount of the light source increases, the CCD camera of the reflected light of the normal photoconductor portion. Has a higher brightness level. Therefore, the amount of light reflected from the normal part of the photoconductor is monitored by an optical sensor element, and the output is received by an automatic dimmer to control the amount of light from the light source. Can be controlled so that it becomes the center value of the gradation, and it becomes possible to detect both dark and thin defects of the photoconductor with good sensitivity and accuracy.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing the construction of an embodiment of a defect inspection machine according to the present invention. FIG. 1 (a) is a side view and FIG.
(B) is a front view. Outer diameter 30 mm, length 300 mm
A CCD camera 2 as a surface scanning line sensor is arranged toward the outer peripheral surface of the cylindrical photosensitive member 1, and a signal processing unit 3 for processing an output signal thereof is connected and arranged. A rod-shaped fluorescent lamp as a light source 4 is arranged opposite to the camera within a range of 90 ° when viewed from the cylindrical axis of the photoconductor 1 so that its axis is parallel to the cylindrical axis of the photoconductor 1. Reference numeral 5 is an optical sensor element for monitoring the reflected light from the normal portion of the photoconductor, and the output of the optical sensor element 6 is used to adjust the light amount of the light source 4 by the automatic light controller 6. Reference numeral 7 denotes a drive motor that drives the photoconductor 1 to rotate about a cylindrical axis.

Two CCD cameras are arranged in the axial direction of the photoconductor so that the full length region of the photoconductor having a length of 300 mm can be detected. As a CCD camera, the output is at a brightness level of 256 gradations, and when a 2048-bit, resolution 78 μm, processing speed 2 MHz is used, the number of scanning lines per second is 1000 / sec, and the detection speed in the circumferential direction is 78 mm.
/ Sec, and the inspection time for one rotation of the photoreceptor having an outer diameter of 30 mm (peripheral length 94.2 mm) is 1.2 seconds. Therefore, the rotation speed of the photoconductor should be 50 rpm.

Using a photoconductor having 20 image defects and 20 photo defects which are darker than the normal part in the image defect of the photoconductor, using the above defect inspection machine, the defect detection ability and the reflected light from the normal part of the photoconductor are detected. The relationship between the brightness level of the CCD camera and the gradation was examined. By changing the light intensity of the light source, the brightness level of the CCD camera of the reflected light from the normal portion of the photoconductor is set to 56,12.
The gradation was set to 8,200 and the number of detected dark defects and thin defects was checked in each case. Defect judgment level is ±
The value is set to 15 (if the brightness level of the normal portion changes to plus or minus 15 or more, it is detected as a defect). Table 1 shows the number of detected defects at each brightness level gradation.

[0016]

[Table 1]

As can be seen from Table 1, by setting the brightness level of the normal portion of the CCD camera to the central value 128 of the gradation 256, it is possible to detect dark defects and thin defects equally well. In the example of the defect inspection machine described above, the output of the optical sensor element that receives the reflected light from the normal portion of the photoconductor is used as the input information to the automatic dimmer that controls the light intensity of the light source, but the output of the CCD camera itself By processing the information and using this as input information to the automatic dimmer, the accuracy of defect detection can be further improved.

[0018]

According to the present invention, a light source for irradiating light on the outer peripheral surface of a cylindrical photosensitive member in the direction of the cylinder axis, and a reflected light is received by scanning the irradiation surface to detect the in-plane light intensity. Defect inspection machine for electrophotographic photoconductor having a surface scanning sensor, a signal processing unit for processing the output of the sensor to detect a defect on the photoconductor surface, and means for rotationally driving the photoconductor around a cylindrical axis. In addition, an optical sensor element for receiving the reflected light, and an electrophotographic photoconductor defect inspection machine having a structure provided with an automatic light adjuster for adjusting the light amount of the light source according to the output of the optical sensor element. Using this inspection machine, the outer surface of the photoconductor is irradiated with light from a light source, the reflected light of the normal part of the photoconductor is monitored by an optical sensor element, and the output is used to sensitize the light amount of the light source. The light reflected from the normal part of the body is detected by the surface scanning sensor. In the state where the center value of the gradation of the degree level is controlled, while rotating the photosensitive member, the peripheral surface of the photosensitive member is irradiated with light from the light source, and the surface scanning sensor scans the peripheral surface of the photosensitive member. By processing the output of the surface scanning sensor that receives the reflected light inside and detects the light intensity in the signal processing unit to perform a defect inspection, even if the color or density of the surface changes depending on the type of the photoconductor, Dark defects on the photoreceptor,
It becomes possible to detect thin defects with the same sensitivity and accuracy.

[Brief description of drawings]

1A and 1B are views showing a configuration of an embodiment of a defect inspection machine of the present invention, FIG. 1A is a side view, and FIG. 1B is a front view.

FIG. 2 is a waveform diagram of a dark defect and a thin defect of the photoconductor and defect detection signals corresponding to them in the present invention.

[Explanation of symbols]

 1 Photoreceptor 2 CCD Camera (Surface Scanning Line Sensor) 3 Signal Processor 4 Light Source 5 Optical Sensor Element 6 Automatic Dimmer 7 Drive Motor

Claims (2)

[Claims] 1. A light source for irradiating light on the outer peripheral surface of a cylindrical photoconductor in the direction of the cylinder axis, a surface scanning sensor for detecting reflected light by scanning the irradiation surface to detect the in-plane light intensity, and A defect inspection machine for an electrophotographic photosensitive member, comprising: a signal processing unit that processes an output of a sensor to detect a surface defect of the photosensitive member; and a unit that rotationally drives the photosensitive member around a cylindrical axis. An optical sensor element for receiving light,
A defect inspection machine for an electrophotographic photosensitive member, comprising an automatic light adjuster for adjusting the light amount of the light source according to the output of the optical sensor element. 2. The defect inspecting apparatus according to claim 1, wherein the outer peripheral surface of the photoconductor is irradiated with light from a light source, the reflected light from the normal portion of the photoconductor surface is monitored by an optical sensor element, and the output is automatically detected. While controlling the light quantity of the light source by the dimmer so that the reflected light from the surface of the normal portion of the photoconductor becomes the center value of the gradation of the brightness level of the surface scanning sensor, while rotating the photoconductor,
The signal processing unit processes the output of the surface scanning sensor, which irradiates the outer surface of the photosensitive member with light from a light source, scans the outer surface of the photosensitive member with a surface scanning sensor, receives the reflected light within the surface, and detects the light intensity. A method of inspecting a defect of an electrophotographic photosensitive member, which comprises performing a defect inspection.