JP3287526B2 - Surface inspection method for photoconductor drum for electrophotography - Google Patents

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 the presence or absence of a defective portion on the surface of an electrophotographic photosensitive drum using an image processing technique, and more particularly to a secondary processing inspection method attached to a line sensor or an area sensor. , For electrophotography capable of distinguishing the original defects of the electrophotographic photosensitive drum surface such as scratches on the drum surface from electric signals such as dust, floating matters such as dust, and noise existing in the air The present invention relates to a method for detecting a defect on a photosensitive drum surface.

[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. There is known a method of making a determination based on the above.

[0003]

However, in the conventional image processing method, it is necessary to discriminate dust, dust, lubricant adhering to the drum surface, noise coming on the image, and a defect which should be discriminated. Is difficult to do.
Therefore, in the conventional method for detecting a defect on the surface of a photoreceptor drum for electrophotography, in order to eliminate an influence of attached matter such as dust and perform accurate detection, an electrostatic removal device is used in a stage before image processing. Measures are taken to remove dust and dirt adhering to an object to be detected and to prepare a clean room in order to reduce floating dirt and the like. Also, in order to prevent noise from being mixed into the detection signal, a noise killer is attached to the power supply.

As described above, it is a general method to increase the detection accuracy by taking measures before the detection.

However, floating dust and the like may reattach immediately before detection, and even if there is a problem of noise, since the source of the dust extends over many branches such as a robot,
It is extremely difficult to eradicate. Furthermore, in the case of a clean room, there is a problem that equipment costs increase.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the conventional method for detecting a defect on the surface of an electrophotographic photosensitive drum, without using a pre-process such as using a clean room or removing static electricity. Another object of the present invention is to provide a method for detecting a defect on the surface of a photosensitive drum for electrophotography, 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 a defect on the surface of a photosensitive drum for electrophotography, the method comprising the steps of: The light from the light source is applied to the surface of the electrophotographic photosensitive drum while making one rotation, and the reflected light from the surface of the electrophotographic photosensitive drum is changed to C.
The output signal from the CCD line sensor camera is read by a CD line sensor camera, and image information for one round of the surface of the electrophotographic photosensitive drum is stored as a map. The image information for one round is similarly stored as a map by rotating once again in the direction, and a frame is formed on the defect detected from the first image information.
The defect detected from the second image information is set in the frame
When entering, the defect of the electrophotographic photosensitive drum surface
Discriminated, dust when not enter, and deposits such as dust determination
A method for inspecting the surface of an electrophotographic photosensitive drum is provided.

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

More specifically, in the method for inspecting an electrophotographic photosensitive drum according to the present invention, a jig to which the electrophotographic photosensitive drum is fixed is rotated in a circumferential direction by a drum rotating motor while the drum surface is rotated. The optical axis where the above characteristic is apt to occur is selected, light is applied to the drum from the light source, and the CCD camera is set at a regular reflection position or a position slightly shifted from the regular reflection with respect to the optical axis. Actually, the position of the CCD camera is determined by the detection item.

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

Next, after an external effect such as aeration is applied, a second measurement is performed under the same conditions as the first measurement.

At the time when the two inspections are performed, the first map and the map 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 adding the play (error) in the thrust direction due to the jig to which the drum is fixed and the rotational unevenness in the circumferential direction by the motor for rotating the drum, the frames in the X and Y directions are assembled. If the same voltage signal is present, it is determined that they are the same.

When the drum is inspected by the above-described method, it is necessary to clarify the discrimination between the surface defect of the drum itself and a defect which may occur around the drum and which can be erroneously detected, such as dust, dust and noise. 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 using a photosensitive drum (30 mm in diameter) for electrophotography used in a cartridge for a laser printer (LBP-LX) manufactured by Canon.

As one sample, a knife is used to apply a length of 1 mm and a width of 0.1 mm to the surface of the photosensitive drum for electrophotography.
Created with scratches. This is designated as Sample A. Separately, a length of 1 mm
A piece with lint having a width of 0.1 mm (φ0.1 mm) was prepared. This is designated as Sample B.

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

In FIG. 1, reference numeral 1 denotes a CCD camera, 2
Denotes a light source, and 3 denotes an electrophotographic photosensitive drum to be inspected. Although not shown, the photosensitive drum is fixed to a jig and is rotated by a driving force of a motor. Light from the light source 2 is applied to the surface of the photosensitive drum 3, and the reflected light is captured by 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 as a light receiver. The output of the CCD camera is compared with a threshold straight line in a binarization 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, the measurement was performed on sample A by operating it under 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 Lux.
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 =
23.55 mm / sec.

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

Under these conditions, when detecting with a CCD line sensor, a vertical and horizontal resolution of 60 μm is required, so a camera speed of 23.55 mm / 60 μm = 392.5 lines / sec or more is required. It is.

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

By selecting such a CCD camera, this C
When a CD camera is installed, the distance between the CCD camera and the photosensitive drum varies depending 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, if 7 μm per pixel is selected with 1 × 4.096 bit (5000 pixels), the detection area of the photosensitive drum is 240 mm, so that 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) The distance is calculated.

In this case, since the lens is symmetrical with the lens surface as an intersection, the angle is 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 1 = 240 × 50 / 28.67 = 418.6 mm is required. This completes the setting that ensures the vertical and horizontal resolution.

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

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

First, a non-defective drum having no surface defect is prepared, light is irradiated on 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 rotation and the second rotation, and the image processing information is overlapped to make a determination, so that the circumferential drum rotation unevenness, the axial thrust play,
Add the manufacturing accuracy of the drum itself and set the circumferential direction to the X direction,
A frame is set as the axial direction and the Y direction. Canon LBP-
In the case of the photosensitive drum for Lx, it was set to 1200 μm in the X direction and 1200 μm in the Y direction. This is because the defect at the first rotation is 0 point, so (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 are set for one defect.

Next, in order to determine a defect from a non-defective product,
It is necessary to set a threshold. A / D conversion input is 8
In the case of bits, threshold values for the (+) value and the (-) value are set for 2 ⁸ = 256 gradations from X ⁿ = division gradations. For example, in the case of a photosensitive drum for LBP-Lx manufactured by Canon, +1
Set to 5 and -15 (ternary conversion).

According to these settings, sample A
Was measured. As a result, the image processing information of the first rotation and 2
The image processing information of the rotation was in the frame of (X) | 1200 μm | × (Y) | 1200 μm | Therefore, it was possible to detect that the surface defect was an intrinsic defect of the photosensitive drum.

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

If a surface defect can be detected as in sample A, the size of the defect is determined by comparing the first rotation and the second rotation and determining the larger one (the number of dots is larger). One).

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

First, the following samples were prepared using an LBP-Lx cartridge. A punch is used to scratch the surface of the electrophotographic photosensitive drum made into a cartridge. The flaw diameter is φ0.5 mm.

Next, PVdF (polyvinyl vinyl fluoride) powder is adhered to the surface of the electrophotographic photosensitive drum. PVdF
The powder is a 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 to prevent the blade for collecting the toner from being turned up, by attaching the PVdF powder to the blade or to the surface of the photosensitive drum.

The means for discriminating between powder and scratches using the above sample as sample C will be described below.

First, the sample C is detected in the configuration shown in FIG. In FIG. 3, 1 is a CCD camera, 2 is a light source,
Reference numeral 3 denotes a photosensitive drum, and reference numeral 4 denotes a cartridge. The cartridge 4 is fixed to a jig, and rotates the photosensitive drum 3 by a driving force of a motor. In the case of the image processing under such conditions, the lubricant comes on the drum surface every rotation, and the lubricant on the drum is collected by the cleaner blade. Therefore, since a phase difference occurs there, if the measurement is performed as in the first embodiment, it can be clearly determined that the lubricant is used.

[0040]

As described above, according to the present invention, 2
Measurement, map the data, and superimpose the discrimination to clearly distinguish floating objects such as dust and dust from surface defects, clear distinction between electrical signals such as noise and surface defects, Furthermore, it is possible to clearly distinguish the lubricant adhering to the drum surface from the surface defect, and the effect of improving the quality inspection accuracy is obtained.

In terms of equipment, enormous investment in the inspection environment can be suppressed. For example, the necessity of a clean room, a static eliminator, and a dust collecting facility is eliminated. In addition, by improving the detection accuracy, the electrophotographic photosensitive drum manufacturing line, which had been difficult to automate, can be fully automated.
Cost reduction and personnel reduction can be realized.

[Brief description of the drawings]

FIG. 1 is a schematic side view of an apparatus used for an electrophotographic photosensitive drum surface inspection according to an embodiment of the present invention.

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

FIG. 3 is a block diagram showing a process of performing a surface inspection of the electrophotographic photosensitive drum formed into a cartridge in accordance with the present invention.

[Explanation of symbols]

 Reference Signs List 1 CCD camera 2 Light source 3 Photoconductor drum for electrophotography 4 Cartridge

Claims (5)

(57) [Claims] 1. A surface inspection method for detecting a defect on a surface of an electrophotographic photosensitive drum, wherein the surface of the electrophotographic photosensitive drum, which is an object, is rotated by one rotation in a circumferential direction from a light source. And 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 photosensitive drum for electrophotography is rotated once again in the circumferential direction, and the rotation is similarly performed for one rotation. The image information is stored as a map , a frame is set for a defect detected from the first image information, and when the defect detected from the second image information falls within the frame, the electrophotographic photosensitive drum is used. If it is judged as a surface defect and does not enter
A method for inspecting the surface of an electrophotographic photoreceptor drum, wherein the surface of the photoreceptor drum is distinguished from foreign matter such as dust or dust. 2. A photosensitive drum is determined to be defective if a result of a comparison between the first image information and the second image information deviates above or below a predetermined threshold value. 2. The method according to 1. 3. The light emitted from the light source to the surface of the electrophotographic photosensitive drum has a light amount of 1500 Lux to 350 Lux.
3. The method according to claim 1 or 2, wherein the light is a light having a short wavelength of 500 nm or less cut at 0 Lux. 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 photoreceptor is selected from an organic semiconductor, amorphous silicon, a selenium photoreceptor, and a CDS photoreceptor.