JP2001004552A - Method and apparatus for inspecting defect of object surface - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a detect ratio, shorten a processing time and reduce costs by radiating an illumination light having a width in a vertical scanning direction to an object surface, converting an obtained analog image signal to a digital signal, and extracting only image data corresponding to a defect part. SOLUTION: A work 2 is set to be in contact with a pair of rotary rollers 3 set on an inspecting jig, and then the work is rotated by the rollers 3. A luminous flux 4 radiated from a slit of a transmission light 1 set nearly parallel to a rotation axis of the work 2 is regularly reflected or scattered by a surface of the work 2 and taken into a line sensor camera 5. That is, density information on the surface of the work 2 is inputted synchronously with the rollers 3 for every one scanning to an A/D converter 7 in an image-processing apparatus via a signal cable 6. Only a part corresponding to a defect part is extracted from original image data, so that a density irregularity of particularly a low contrast surface of a cylindrical object with minute pits and projections can be highly accurately detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for inspecting an object surface for detecting low-contrast defects scattered on a cylindrical object such as a photosensitive drum of a copying machine.

[0002]

2. Description of the Related Art As disclosed in, for example, Japanese Patent Application Laid-Open No. 5-18727, low-contrast defects scattered on a cylindrical object such as a photosensitive drum of a conventional copying machine are converted into a photoelectric conversion element such as a line sensor. There is known a device for detecting the temperature. In this case, since the illumination conditions are insufficient due to the characteristics of the test object, the aperture of the objective optical system must be taken in a substantially open state.

[0003] For this reason, defect detection is easily performed because of the large influence of shading caused by the illumination system and the optical system and the remarkable fluctuation of the signal level caused by the surface deflection caused by the rotation of the cylindrical object. I couldn't do that. Therefore, the same area is captured multiple times and averaged to increase the S / N ratio of the video signal, the accuracy of the mechanism for rotating the cylindrical object is increased to suppress the surface vibration, and the vibration is detected by a contact-type sensor. Correction or detection of a defective part.

[0004]

However, in the above-mentioned prior art, when detecting a defect on a cylindrical object, the same region is taken in a plurality of times, added and averaged, or the accuracy of the rotating mechanism is increased. Alternatively, shading correction is performed by defining a reference work. For this reason, not only a lot of time is spent on the detection processing time and adjustment, but also the apparatus has to be complicated. When the apparatus becomes complicated, there are problems such as an increase in the apparatus cost and a decrease in the detection rate of the defective portion.

SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide a method and an apparatus for inspecting a defect on the surface of an object which have a high defect detection capability, shorten the detection processing time and reduce the apparatus cost.

[0006]

A defect inspection method for an object surface according to the present invention is a method for inspecting a defect on an object surface by scanning the surface of a cylindrical object to inspect for defects existing on the surface. Irradiating illumination light having a width in the sub-scanning direction, and converting an image signal obtained by a photoelectric conversion unit from an illuminated area on the surface of the object from an analog signal to a digital signal. The method includes a step of storing image data of a digital signal corresponding to a scan line corresponding to a width of the minimum defect in the sub-scanning direction, and a step of detecting only image data corresponding to a defective portion.

In the defect inspection method for an object surface according to the present invention, in the defect detecting step, the digital signal data of the original image is added in an arbitrary direction to at least the width of the minimum defect to be detected in the sub-scanning direction. Processing, and the calculated projection data is subjected to differential calculation processing.
Further, in the defect inspection method for an object surface according to the present invention, the digital signal data of the original image is added and processed in the sub-scanning direction and the main scanning direction.

The object surface defect inspection apparatus according to the present invention is an object surface defect inspection apparatus which scans a cylindrical object surface to inspect a defect existing on the surface. Means for irradiating illumination light having a width in the scanning direction; means for converting an image signal obtained from the illuminated area on the object surface by the photoelectric conversion means from an analog signal to a digital signal; It has means for storing image data of a digital signal corresponding to a scanning line corresponding to the width in the scanning direction, and defect detecting means for extracting only image data corresponding to a defective portion.

Further, in the defect inspection apparatus for an object surface according to the present invention, the defect detecting means is provided for detecting at least the minimum defect width to be detected in the sub-scanning direction of the original image data obtained from the image data storing means. It is characterized by comprising a projection data operation block for adding in the sub-scanning direction and the main scanning direction, and a differential operation block for differentiating the projection data calculated by the projection data operation block.

Further, in the storage medium of the present invention, the steps constituting the defect inspection method are stored so as to be readable from a computer.

According to the present invention, there is provided an apparatus for detecting minute unevenness and low-contrast density unevenness on a surface of a cylindrical object, wherein the object surface is illuminated in a slit shape in the same direction as the longitudinal direction. And an imaging means for photoelectrically converting the illuminated area on the surface as an image signal. In particular, the defect detecting means for extracting only the image data portion corresponding to the defective portion is provided in the sub-scanning direction with respect to at least the width of the minimum defect to be detected in the sub-scanning direction of the original image data obtained from the image data storage means. And a projection data calculation block for adding the data in the main scanning direction, and a differential calculation block for differentiating the projection data calculated by the projection data calculation block, whereby a defective portion can be detected without overlooking it.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a method and an apparatus for inspecting defects on an object surface according to the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of the embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a transmission light as illumination means, 1a an illumination slit of the transmission light 1, 2 a cylindrical work to be inspected, 3 a rotating roller for rotating the work 2 in a circumferential direction, and 4 a transmission light 1 Is an optical path of slit light reflected from the work 2 and 5 is a CCD line sensor camera for converting the slit-like reflected light into an image signal, and 6 is a signal cable for transmitting the image signal to image processing means.

Reference numeral 7 denotes an A for converting an image signal into a digital signal.
/ D converter, 8 is an image memory for holding data of at least the sub-scanning line width of the minimum defect size of the image signal to be detected, and 9 and 10 store pixel data of an arbitrary area of M × N pixels in the sub-scanning direction. A sub-scanning and main-scanning operation block for performing addition operation in the main scanning direction; 11 and 12 are a sub-scanning and main-scanning differential operation block for differentiating projection data obtained from each of the projection operation blocks 9 and 10; CPU board that controls the flow of data and processes arithmetic operations at high speed, 14 is a data bus, and 15 is an A / D
This is an image processing device including a converter 7 and a data bus 14.

Next, a specific embodiment of the present invention in the above configuration will be described with reference to FIGS. FIG. 1 is a diagram showing the overall configuration of the present invention, FIG. 2 is a diagram showing a flowchart of the process, FIG. 3 is a diagram showing image data of a typical defective portion, and FIG. Figure showing
5 and 6 are diagrams showing a processing flow of defect enhancement by projection operation and differential operation processing, and FIG. 7 is a diagram showing an example of projection operation and differential operation processing.

First, the work 2 is set so as to be in contact with a pair of rotating rollers 3 attached to the inspection jig, and then rotated by the rotating rollers 3 (steps S1 to S1).
3). The light beam 4 emitted from the slit of the transmission light 1 installed substantially parallel to the rotation axis of the work 2 is specularly reflected or scattered on the surface of the work 2 and taken into the line sensor camera 5. In other words, the density information on the surface of the work 2 is synchronized with the rotating roller 3 for each scanning line, and is converted into an image signal by the line sensor camera 5 (2048 pixels) via the signal cable 6 in the image processing apparatus. /
It is input to the D converter 7.

The A / D converter 7 converts the analog image signal to 8
Is converted into a digital image signal of 1 bit, and is sequentially saved in the image memory 8 for each scanning line (steps S4 to S4).
6). As a result, an image as shown in FIG. 3 is stored in the image memory 8 as 8-bit digital data. In FIG. 3, portions a and b surrounded by circles are called a white defect and a black defect, respectively.

Next, in order to extract a white defect, area data of 10 pixels in the main scanning direction × 10 pixels in the sub-scanning direction is transferred from the image memory 8 and projected arithmetic processing is performed according to the following procedure. (Step S7) and differential operation processing (Step S8) are performed.

FIG. 4 shows pixel data near a white defect. First, a defect 100 _W1 of the paper longitudinal direction, that is the sub-scanning direction pale streaky. Here, an addition process is performed by the sub-scanning projection operation block 9 and the main-scanning projection operation block 10 for each of the sub-scanning direction and the main scanning direction.

In this case, as shown in FIG.
When the projection operation is started in step 1, image data is loaded from the image memory 8 (step S12). Here, an addition process is performed for each of the sub-scanning direction and the main scanning direction (step S13), and the added data is saved (step S14).

As shown in FIG. 4, the result of the addition processing for the defect 100 _W1 is clearly higher than the addition values of the other columns.

On the other hand, FIG. 4 shows a light streak-like defect 100 _W2 in the horizontal direction of the paper, ie, in the main scanning direction. This defect 1
Also for _00W2 , an addition process is performed by the sub-scanning projection operation block 9 and the main-scanning projection operation block 10 for each of the sub-scanning direction and the main scanning direction according to the flowchart of FIG.

FIG. 4 shows the result of addition processing for defect 100 _W2 .
As shown in (1), the value is clearly higher than the sum of the other rows.

Further, the added values in the sub-scanning direction and the main scanning direction calculated as described above, that is, the projection data of the defect 100 _W1 and the defect 100 _W2 are subjected to the sub-scanning and main-scan differential operation blocks 11 and 12 in each direction. Differentiate.

In this case, as shown in FIG.
When the differentiation operation is started at step 1, the projection data is loaded from the memory (step S22). Here, differentiation processing is performed for each of the sub-scanning direction and the main scanning direction (step S2).
3) The differential data is saved (step S2)
4).

FIG. 4 shows the result of the differential processing for the defect 100 _W1 and the defect 100 _W2 by this differential processing.

FIG. 7 shows pixel data near a black defect. In the figure, shows a paper machine direction i.e. defects in the sub-scanning direction black streak 100 _B1 and paper lateral or main scanning direction black streak-like defects 100 _B2. Also in the case of a black defect, projection operation processing and differential operation processing are performed on the defect 100 _B1 and the defect 100 _{B2 in the same} manner as the white defect, and the addition processing result and the differential processing result shown in FIG. 7 are obtained.

As described above, a low-contrast light streak-like defect or a black defect can be extracted (FIG. 2, steps S9 and S10).

Next, the white defect and the black defect are binarized by a predetermined threshold, and the image is superimposed on the same area of the image memory (step S11). Next, the integrated defect image is binarized with an arbitrary threshold, and a labeling process is not performed. A pixel value size, a fillet diameter, or the like is used to determine whether or not the defect is a defect.
A series of processing ends (steps S12, S13).

The present invention realizes the functions of the above-described embodiments in an apparatus connected to the various devices or a computer in a system so as to operate various devices so as to realize the functions of the above-described embodiments. The present invention also includes programs implemented by supplying the program code of the software described above and operating the various devices according to programs stored in a computer (CPU or MPU) of the system or apparatus.

In this case, the program code of the software itself realizes the function of the above-described embodiment, and the program code itself and means for supplying the program code to the computer,
For example, a storage medium storing such a program code constitutes the present invention. As a storage medium for storing the program code, for example, a floppy disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a magnetic tape, a nonvolatile memory card, a ROM, and the like can be used.

When the computer executes the supplied program code, not only the functions of the above-described embodiment are realized, but also the OS (Operating System) or other operating system running on the computer. Even when the functions of the above-described embodiments are realized in cooperation with application software or the like, the program codes are included in the embodiments of the present invention.

Further, after the supplied program code is stored in a memory provided in a function expansion board of a computer or a function expansion unit connected to the computer, the function expansion board or the function expansion unit is specified based on the instruction of the program code. The present invention also includes a case where a CPU or the like provided in or performs some or all of the actual processing, and the processing realizes the functions of the above-described embodiments.

[0034]

As described above, according to the present invention, only a portion corresponding to a defective portion is extracted from original image data in a defect inspection apparatus of this kind, and particularly, a fine unevenness on the surface of a cylindrical object is obtained. In addition, it is possible to detect high-contrast and low-contrast density unevenness with high accuracy. In addition, efficient detection can significantly reduce the detection processing time,
Further, since the apparatus configuration is relatively simple, there are advantages such as substantial cost reduction.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a cylindrical object inspection apparatus according to the present invention.

FIG. 2 is a flowchart showing a process of a process according to the present invention.

FIG. 3 is an image of a black defect and a white defect scattered on a typical cylindrical object plane.

FIG. 4 is a flowchart of a projection calculation process.

FIG. 5 is a diagram for explaining a process of a projection operation.

FIG. 6 is a flowchart of a differential operation process.

FIG. 7 is a diagram for explaining a process of a differential operation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transmission light 2 Illumination slit 3 Rotating roller 4 Optical path of slit light 5 Line sensor camera 6 Signal cable 7 A / D converter 8 Image memory 9 Subscanning direction projection operation block 10 Main scanning direction projection operation block 11 Subscanning direction differentiation processing Block 12 Differential processing block in main scanning direction 13 CPU board 14 Data bus 15 Image processing device a, b Defect location

 ──────────────────────────────────────────────────続 き Continuing on the front page F term (reference) 2F065 AA49 BB06 BB08 BB16 CC00 DD00 DD06 FF42 GG16 HH05 HH12 JJ02 JJ08 JJ25 LL28 MM04 PP13 QQ03 QQ07 QQ13 QQ21 QQ24 QQ27 QQ45 RR05 2G05 04 EA0508 5C054 AA01 AA05 CA04 CC03 EA01 FC05 HA01 HA05

Claims (6)

[Claims] 1. A defect inspection method for an object surface for inspecting a defect existing on the surface of a cylindrical object by scanning the surface of the object, wherein the object surface is irradiated with illumination light having a width in a sub-scanning direction. Converting an image signal obtained from the illuminated area on the object surface by the photoelectric conversion means from an analog signal to a digital signal, at least corresponding to a scan line corresponding to a width of the minimum defect to be detected in the sub-scanning direction. A defect inspection method for an object surface, comprising: a step of storing image data of a digital signal; and a defect detection step of extracting only image data corresponding to a defective portion. 2. In the defect detection step, the digital signal data of the original image is added at least to the width of the minimum defect to be detected in the sub-scanning direction in an arbitrary direction, and the calculated projection data is differentiated. The method according to claim 1, further comprising performing an arithmetic process. 3. The defect inspection method according to claim 2, wherein the digital signal data of the original image is added and processed in the sub-scanning direction and the main scanning direction. 4. A defect inspection apparatus for inspecting a defect on a surface of a cylindrical object by scanning the surface of the cylindrical object, and irradiating the object surface with illumination light having a width in a sub-scanning direction. Means for illuminating; means for converting an image signal obtained from the illuminated area on the object surface by the photoelectric conversion means from an analog signal to a digital signal; and A defect inspection apparatus for an object surface, comprising: means for storing image data of a corresponding digital signal; and defect detection means for extracting only image data corresponding to a defective portion. 5. A projecting means for adding in the sub-scanning direction and the main scanning direction at least the width of the minimum defect to be detected in the sub-scanning direction of the original image data obtained from the image data storage means. 5. The apparatus according to claim 4, comprising a data operation block and a differential operation block for differentiating the projection data calculated by the projection data operation block. 6. A storage medium in which the steps constituting the defect inspection method according to claim 1 are stored so as to be readable from a computer.