JPH08304292A - Surface inspection method for electrophotographic photosensitive drum - Google Patents

Abstract

(57) [Summary] [Purpose] A method for detecting defects on the surface of a photoconductor drum for electrophotography, which can improve the inspection accuracy of the drum surface without using a clean room or performing pre-treatment such as static electricity removal. I will provide a. [Structure] While rotating the electrophotographic photosensitive member, which is the subject, once in the circumferential direction, apply light from a light source to the surface, and perform two operations to read the reflected light from the electrophotographic photosensitive member surface with a CCD camera. During each operation, the image information from the CCD camera is stored as a map for one rotation of the surface of the photosensitive drum,
By comparing the image information of the first time and the image information of the second time, it is possible to distinguish the defect on the surface of the photoconductor drum from the adhered matter such as dust and dust. Surface inspection method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for inspecting a defective portion on the surface of a photoconductor drum for electrophotography by using an image processing method, and more particularly to a secondary processing inspection method attached to a line sensor and an area sensor. For electrophotography, which is capable of distinguishing between original defects on the surface of the electrophotographic photosensitive drum, such as scratches on the drum surface, and electrical signals such as dust and dust floating in the air and noise. The present invention relates to a method for detecting defects on the surface of a photosensitive drum.

[0002]

2. Description of the Related Art As a conventional method for inspecting the surface of a photoconductor drum for electrophotography, light is applied to the surface of the photoconductor drum, the reflected light is read by a CCD camera, and a defective portion and a non-defective portion are separated by a certain threshold value. A method of making a distinction is known.

[0003]

However, in the conventional image processing method, it is possible to discriminate between dust, dust, lubricant adhering to the drum surface, noise carried on the image, and a defect which should be discriminated. Difficult to do.
Therefore, in the conventional method for detecting defects on the surface of a photoconductor drum for electrophotography, an electrostatic eliminator is used at a stage before image processing in order to perform accurate detection by eliminating the influence of foreign matter such as dust. Measures are taken such as removing dust and dust adhering to the object to be detected, and preparing a clean room to reduce floating dust. Further, in order to prevent noise mixed in the detection signal, a noise killer is also attached to the power supply.

It is a general method to improve the detection accuracy by taking measures in the stage before the detection as described above.

However, floating dust or the like may be reattached on the verge of detection, and even if there is a problem of noise, the source of generation is over multiple branches such as a robot.
Eradication is extremely difficult. Furthermore, in the case of a clean room, there is a problem that the equipment cost is high.

An object of the present invention is to solve the above-mentioned problems of the conventional method for detecting defects on the surface of a photoconductor drum for electrophotography, without using a clean room or performing pretreatment such as static electricity removal. Another object of the present invention is to provide a method for detecting defects on the surface of an electrophotographic photosensitive drum, which can improve the inspection accuracy of the drum surface.

[0007]

According to the present invention, there is provided a surface inspection method for detecting defects on the surface of an electrophotographic photosensitive drum, wherein the electrophotographic photosensitive drum which is an object is circumferentially The light from the light source is applied to the surface of the electrophotographic photosensitive drum while rotating it once, and the reflected light from the surface of the electrophotographic photosensitive drum is C
The signal is read by the CD line sensor camera, the output signal from the CCD line sensor camera is stored as a map of image information for one round of the surface of the electrophotographic photosensitive drum, and then the electrophotographic photosensitive drum is circled. Similarly, the image information for one rotation is stored as a map by rotating once again in the direction, and the image information of the first time is compared with the image information of the second time, whereby a defect on the surface of the electrophotographic photosensitive drum is obtained. There is provided a method for inspecting the surface of a photoconductor drum for electrophotography, which is characterized in that it is distinguished from attached matter such as dust and dust.

That is, in the present invention, in order to discriminate dust, noise, drum lubricant and scratches, and manufacturing defects, image processing is performed twice consecutively so that the first and second
If there is no phase difference from the first time, it is determined as a defect.
At this time, in order to distinguish between the floating dust and the defect, 1
If spraying with air is performed between the second measurement and the second measurement, a phase shift will occur, so it can be judged to be more effective.

More specifically, in the electrophotographic photosensitive drum inspecting method of the present invention, the drum surface is rotated by a drum rotation motor in a circumferential direction on a jig to which the electrophotographic photosensitive drum is fixed. Select an optical axis that is likely to cause the characteristics of (3), irradiate the drum with light from the light source, and set the CCD camera at the specular reflection position or a position slightly displaced from the specular reflection with respect to the optical axis. Actually, the CCD camera position is determined by the detection item.

After completing this preparation, the first measurement is performed. The image signal captured by the CCD camera is A /
After D conversion, the drum is stored (mapped) as a flat plane.

Next, after applying an external effect such as aeration, the second measurement is carried out under the same conditions as the first measurement.

At the time when the inspection is performed twice, the maps obtained in the first measurement and the maps obtained in the second measurement are overlapped and the difference between them is compared. The actual comparison work is performed by a software program prepared in advance.

At this time, after the play (error) in the thrust direction due to the jig fixing the drum and the rotational unevenness in the circumferential direction due to the motor for rotating the drum are added, a frame in the X direction and the Y direction is assembled. If there is the same voltage signal at, it will be judged as the same place.

When the drum is inspected by the above-mentioned method, it is possible to clearly distinguish between the surface defect of the drum itself and the erroneously detectable defects such as dust, dust, and noise that may occur around the drum. It will be possible.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

Example 1 Two kinds of samples were prepared by using an electrophotographic photosensitive drum (diameter 30 mm) used in a cartridge for Canon laser printer (LBP-LX).

As one sample, a knife was used to form a 1 mm long and 0.1 mm wide surface of the photosensitive drum for electrophotography.
I made a scratched one. This is designated as Sample A. Separately, a length of 1 mm on the surface of the electrophotographic photosensitive drum,
A product with lint having a width of 0.1 mm (φ0.1 mm) was prepared. This is sample B.

Next, the surface inspection of Sample A and Sample B is performed using the apparatus shown in FIG.

In FIG. 1, reference numeral 1 is a CCD camera, 2
Is a light source, and 3 is an electrophotographic photosensitive drum to be inspected. Although not shown, the photosensitive drum is fixed to a jig and rotated by the driving force of a motor. The light from the light source 2 is applied to the surface of the photosensitive drum 3, and the reflected light is taken into the CCD camera 1.

The processing flow of the surface inspection is as shown in FIG. In FIG. 2, light from a fluorescent lamp (yellow) as a light source is applied to the surface of the photosensitive drum at an appropriate angle, and the reflected light is incident on a CCD camera which is a light receiver. The output of the CCD camera is compared with a threshold straight line in a binarizing circuit provided on the CPU board, and the comparison result is sent to the next double processing step as a flaw signal.

Using this apparatus, first, the sample A was measured according to the following procedure and conditions. First, the light source 2 has a light amount of 1500 Lux to 3500 Lux and a wavelength of 5
A yellow fluorescent lamp that cuts short wavelengths of 00 nm or less was used, and the distance from the drum 3 was 70 mm. The rotation speed of the drum 3 was set to 15 rpm, which is the same as the process speed of the laser printer. In this case, since the diameter of the drum 3 is 30 mm, the rotation distance per second is 15 rpm × 30 mm × π (3.14) / 60 sec =
It becomes 23.55 mm / sec.

Since the minimum value of a general drum defect is 60 μm, the minimum resolution required for this is set to 60 μm.

Under such conditions, when the CCD line sensor is used for detection, a vertical and horizontal resolution of 60 μm is required. Therefore, a camera speed of 23.55 mm / 60 μm = 392.5 lines / sec or more is required. Is.

If a 2.5 MHz CCD camera is selected, the camera cycle is 2.5 MHz / x = 392.5 lines / sec x = 2.5 × 10 ⁶ /392.5 x = 6369, and The resolution is 60 μm.

By selecting such a CCD camera, the C
When a CD camera is installed, the distance between the CCD camera and the photosensitive drum depends on the required resolution or the number of cameras, but here the required lateral resolution is 60 μm,
Since it is a line sensor with one camera, when 1 pixel 7 μm is selected with the number of pixels of 1 × 4.096 bit (5000 pixels), the detection area of the photoconductor drum is 240 mm, so 7 μm × 4096 bit = 28 .67 mm (line sensor length) 240 mm / 28.67 mm = 8.37 times 8.37 × 7 μm = 58.6 μm≈60 μm (horizontal) is calculated.

In this case, since the lens surfaces are line-symmetrical with respect to the intersection, the angles are the same and the distance can be calculated.

When the distance between the CCD element and the lens is 50 mm, a distance of 1: 50 = 240: 28.67 l = 240 × 50 / 28.67 = 418.6 mm is required. This completes the settings that ensure vertical and horizontal resolution.

Next, regarding the angle between the camera and the light source, it is basically desirable that the light from the light source enters the camera by regular reflection. However, it may be better to remove the camera position from the regular reflection depending on the type of defect of the subject. Here, the specular reflection position is selected, and the angle between the light source and the camera is 45 °.
Was set.

A method for actually detecting defects on the surface of the electrophotographic photosensitive drum for samples A and B using the apparatus set under such conditions will be described below.

First, a non-defective drum having no surface defects is prepared, light is applied to the non-defective drum, and the light density is measured by a CCD camera. The measured data is stored as a reference value (0 point). Next, the same measurement is performed at the first and second rotations, and the image processing information is overlapped for determination. Therefore, the drum rotation unevenness in the circumferential direction, the axial thrust play,
Adding the manufacturing accuracy of the drum itself, the circumferential direction is the X direction,
A frame is set in the axial direction and the Y direction. Canon LBP-
In the case of the Lx photoconductor drum, it was set to 1200 μm in the X direction and 1200 μm in the Y direction. Since the number of defects in the first rotation is 0, (X) 1200 μm × (Y) 1200 μm (X) -1200 μm × (Y) 1200 μm (X) -1200 μm × (Y) -1200 μm (X) 1200 μm × ( Y) Four frames of -1200 μm will be set for one defect.

Next, in order to discriminate between a defect and a non-defective product,
It is necessary to set a threshold. 8 A / D conversion inputs
If it is a bit, set thresholds of (+) value and (−) value for 2 ⁸ = 256 gradations from X ⁿ = minute gradations. For example, in the case of Canon LBP-Lx photosensitive drum, +1
Set to 5 and -15 (three-valued).

According to the above setting, sample A
Was measured. As a result, the image processing information of the first rotation and
The image processing information of the rotated eye is within the frame of (X) | 1200 μm | × (Y) | 1200 μm | and is in agreement. Therefore, it was possible to detect that the surface defect was inherent in the photosensitive drum.

Next, the sample B was measured. In this case, since it was temporarily provided with floating dust, air was sucked between the first rotation and the second rotation to move the thread waste. As a result, at the first rotation, it is determined as a defect,
At the second rotation, since it was out of the frame of (X) | 1200 μm | × (Y) | 1200 μm |, defect detection did not overlap and it was possible to judge that it was a dust adhering matter floating in the air.

When it is possible to detect a surface defect as in sample A, the size of the defect is larger when the first and second rotations are compared (the number of dots is large). One) is adopted.

(Example 2) Surface inspection was performed on a finished cartridge for a laser printer (LBP-Lx) manufactured by Canon.

First, the following samples were prepared using the LBP-Lx cartridge. A dent is scratched with a punch on the surface of the electrophotographic photosensitive drum made into a cartridge. The scratch diameter is 0.5 mm.

Next, PVdF (polyvinyl fluoride) powder is attached to the surface of the electrophotographic photosensitive drum. PVdF
The powder is powder used as a lubricant of about 14 μm, and acts until the toner adheres to the surface of the photosensitive drum.
Therefore, in the cartridge manufacturing process, the PVdF powder is used by being attached to the blade or the surface of the photoconductor drum as an object to prevent the blade for collecting the toner from being turned over.

The above sample is referred to as sample C, and the means for distinguishing between powder and scratch will be described below.

First, with the configuration of FIG. 3, the sample C is detected. In FIG. 3, 1 is a CCD camera, 2 is a light source,
Reference numeral 3 is a photosensitive drum, and 4 is a cartridge. The cartridge 4 is fixed to the jig, and the photosensitive drum 3 is rotated by the driving force of the motor. In the case of image processing under such conditions, the rotating lubricant gets on the drum surface every time, and the carried lubricant is collected by the cleaner blade. Therefore, since a phase difference occurs there, it is possible to clearly determine that it is a lubricant by performing the measurement as in Example 1.

[0040]

As described above, according to the present invention, 2
By measuring the number of times, and mapping the data and overlapping to make a distinction, a clear distinction between a floating object such as dust and dust and a surface defect, a clear distinction between an electrical signal such as noise and a surface defect, Further, the lubricant adhering to the drum surface and the surface defect can be clearly discriminated, and the effect of improving the quality inspection accuracy can be obtained.

Also in terms of equipment, enormous investment in the inspection environment can be suppressed. For example, the need for clean rooms, static eliminators, and dust collection equipment is eliminated. In addition, the improved detection accuracy enables complete automation of the electrophotographic photosensitive drum manufacturing line, which was previously difficult to automate.
Cost reduction and personnel reduction can be realized.

[Brief description of drawings]

FIG. 1 is a schematic side view of an apparatus used for inspecting a surface of a photoconductor drum for electrophotography according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a processing flow of inspection according to the present invention.

FIG. 3 is a block diagram showing a process for performing a surface inspection of a cartridge-shaped electrophotographic photosensitive drum according to the present invention.

[Explanation of symbols] 1 CCD camera 2 Light source 3 Electrophotographic photosensitive drum 4 Cartridge

Claims (5)

[Claims] 1. A surface inspection method for detecting a defect on the surface of an electrophotographic photosensitive drum, which comprises rotating an electrophotographic photosensitive drum, which is an object to be examined, once in a circumferential direction from a light source on the surface. Of light, the reflected light from the surface of the electrophotographic photosensitive drum is read by a CCD camera,
The image information from the D camera is stored as a map for one rotation of the surface of the electrophotographic photosensitive drum, and then the electrophotographic photosensitive drum is rotated once again in the circumferential direction to perform one rotation in the same manner. By storing the image information as a map and comparing the first image information and the second image information,
A method for inspecting a surface of an electrophotographic photosensitive drum, characterized in that defects on the surface of the electrophotographic photosensitive drum are distinguished from adhered matters such as dust and dust. 2. The photosensitive drum is determined to be defective if the result of the comparison between the first image information and the second image information is above or below a predetermined threshold value. The method according to 1. 3. The amount of light emitted from the light source to the surface of the electrophotographic photosensitive drum is 1500 Lux to 350.
The method according to claim 1 or 2, wherein the light is 0 Lux and light having a short wavelength of 500 nm or less is cut. 4. The method according to claim 1, wherein air is blown onto the surface of the electrophotographic photosensitive drum after the first measurement. 5. The method according to claim 1, wherein the electrophotographic photoconductor is selected from organic semiconductors, amorphous silicon, selenium photoconductors, and CDS photoconductors.