JPH11185040A - Defect inspection device and method for cylindrical object and storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device for detecting a defect on a cylindrical object with high defect detection ability at a low cost. SOLUTION: This device is provided with a pattern light projection means 1 for projecting a regular pattern onto the surface of a cylindrical object 2 to be inspected, an image data generation means 5 for picking up an image of the regular pattern projected onto the surface of the cylindrical object 2 and for generating image data, a shading correction means 9 for removing a shading signal level in the image data and a means 10 for converting the shading corrected image data into binary image data and evaluating the regularity of the projection pattern in the image data converted into the binary image data. A defect is accurately detected without scanning the same area for plural times and without performing averaging or addition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a defect inspection apparatus and method for a cylindrical object, and a storage medium, and more particularly to a method for detecting a low-contrast defect having a smooth uneven surface on a cylindrical object such as a photosensitive drum of a copying machine. It is suitable to be used for

[0002]

2. Description of the Related Art Conventionally, smooth and low-contrast defects scattered on a cylindrical object such as a photosensitive drum of a copying machine have been detected using a photoelectric conversion element such as a line sensor. There was such a problem.

That is, since the illumination conditions are insufficient due to the characteristics of the object to be inspected, the aperture of the objective optical system has to be almost fully opened to take in the light. There was a problem of being big.
Further, when the defect is gentle, there is a problem that it is difficult to generate a shadow image with a good S / N ratio by illuminating with a simple illumination method.

In order to reduce such a problem, the same area is conventionally inspected a plurality of times to acquire a plurality of inspection values.
The obtained plurality of inspection values are averaged or added to improve the S / N ratio of the video signal.

[0005] Further, by fixing the object to be inspected with high accuracy, the deflection of the surface is reduced, and the cylindrical surface is illuminated almost from the tangential direction, thereby increasing the accuracy of the mechanism for rotating the cylindrical object. Defects are detected or shading correction is performed by defining a reference work.

[0006]

As described above, if the same area is inspected a plurality of times, and the inspection values are fetched and averaged or added, there is a problem that much time is required for the detection processing time. . In addition, it is necessary to spend a lot of time to fix the test object with high accuracy,
Conventionally, there has been a problem that it takes a long time for defect inspection.

Furthermore, the structure of the defect inspection apparatus becomes complicated in order to increase the accuracy of the mechanism for fixing the inspection object or to perform shading correction by defining a reference work, thereby increasing the cost of manufacturing the apparatus. There was a problem that was up.

An object of the present invention is to solve the above-mentioned problem. It is an object of the present invention to provide a defect inspection apparatus capable of shortening the processing time of defect detection and having a significantly improved defect detection capability. The purpose is to simplify.

[0009]

According to the present invention, there is provided a defect inspection apparatus for a cylindrical object, which illuminates a surface of a cylindrical object to be inspected in a strip shape along a longitudinal direction, and further includes an illuminated area. In the defect inspection apparatus for a cylindrical object to detect the defect present on the cylindrical object to be inspected based on the image signal by imaging the image, a regular pattern is formed on the surface of the cylindrical object to be inspected. A pattern light projecting means for projecting a regular pattern projected on the surface of the inspected cylindrical object to generate image data, and a shading signal level in the image data. Shading correction means for removing, conversion means for converting the image data after the shading correction into binary image data, and conversion into the binary image data It is characterized in that it has an evaluation means for evaluating the regularity of the projection pattern in the image data.

Another feature of the apparatus for inspecting a defect of a cylindrical object according to the present invention is that an illuminating apparatus for illuminating a circumferential surface on the inspected cylindrical object in a strip shape in the same direction as the longitudinal direction;
Imaging means for imaging an illuminated area on the circumferential surface to generate an image signal, and detecting a defect existing on the circumferential surface on the inspected cylindrical object based on the image signal In, pattern projection means for projecting a regular pattern on the inspected cylindrical object, imaging means for imaging the pattern projected on the inspected cylindrical object, and an image signal obtained from the imaging means A / D conversion means for converting an analog signal into a digital signal, image data storage means for storing image data composed of digital signals for a plurality of A / D converted scanning lines, and storage in the image data storage means Shading correction means for removing a shading signal level in the processed image data, and converting the image data after the shading correction into binary image data Conversion means for converting is characterized by having an evaluation unit for evaluating the regularity of the projection pattern in the image data converted into the binary image data.

Another feature of the defect inspecting apparatus for a cylindrical object according to the present invention is that the pattern light projecting means comprises a plurality of light emitting devices and a plurality of uniform pitches provided on the light projecting side of the lighting device. It is characterized in that it is composed of a striped pattern mask composed of a transmitting part and a light shielding part.

Another feature of the defect inspection apparatus for a cylindrical object according to the present invention is that the shading correction means converts the image data obtained from the image data storage means into the projected light and shade pattern. It is characterized in that shading correction is performed by a minimum / maximum filter having a size larger than the width of the bright portion.

Another feature of the defect inspection apparatus for a cylindrical object according to the present invention is that the defect inspection apparatus is for inspecting a photosensitive drum of a copying machine.

The defect inspection method for a cylindrical object according to the present invention is characterized in that the surface of the inspected cylindrical object is illuminated in the form of a band along the longitudinal direction, and the illuminated illuminated area is imaged to form an image signal. Generating a regular pattern on the surface of the cylindrical object to be inspected, wherein the defect detection method detects a defect present on the cylindrical object to be inspected based on the generated image signal. Pattern light projection processing, image data generation processing for imaging regular patterns projected on the surface of the inspected cylindrical object to generate image data, and shading correction for removing shading signal levels in the image data Processing, a conversion process of converting the image data after the shading correction into binary image data, and an image converted into the binary image data It is characterized by performing the evaluation process for evaluating the regularity of the projection pattern at over data.

Another feature of the method for inspecting a defect of a cylindrical object according to the present invention is that the surface of the inspected cylindrical object is illuminated in a band along the longitudinal direction, and the illuminated area is imaged and imaged. A defect generating method for detecting a defect present on the inspected cylindrical object based on the generated image signal, wherein a pattern for projecting a regular pattern on the inspected cylindrical object is provided. A light projection process, an imaging process for imaging the pattern projected on the inspected cylindrical object, and an A / A for converting an image signal obtained by the imaging process from an analog signal to a digital signal.
D conversion processing, image data storage processing for storing image data composed of digital signals for a plurality of scanning lines subjected to the A / D conversion in storage means, and shading signal levels in the image data stored in the storage means. Shading correction processing for removal, conversion processing for converting the image data after the shading correction into binary image data, and evaluation of regularity of the light projection pattern in the image data converted to the binary image data It is characterized by performing an evaluation process.

Another feature of the defect inspection method for a cylindrical object according to the present invention is that the pattern light projecting process comprises the steps of: illuminating a plurality of light transmission devices provided on the light projecting side of the illuminating device; It is performed using a striped pattern mask including a portion and a light shielding portion.

In another feature of the defect inspection method for a cylindrical object according to the present invention, the shading correction processing includes the step of converting the image data obtained by the image data storage processing into the projected light and shaded pattern. It is characterized by using a minimum / maximum filter having a size wider than the width of the bright part.

A feature of the storage medium of the present invention is that a program for causing a computer to function as each of the above means is stored.

Another feature of the storage medium of the present invention is that a program for causing a computer to execute the procedure of the above-described defect inspection method for a cylindrical object is stored.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a defect inspection apparatus and method for a cylindrical object and a storage medium according to the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram illustrating a configuration of a defect inspection apparatus for a cylindrical object according to the present embodiment.

In FIG. 1, reference numeral 1 denotes a pattern light emitting means;
Reference symbol a denotes a light source that constitutes the pattern light emitting means 1. 1
Reference numeral b denotes a pattern mask which also constitutes the pattern projecting means 1, reference numeral 2 denotes a work which is a cylindrical object to be inspected, and reference numeral 3 denotes a rotating roller for rotating the work 2 in a circumferential direction.

Reference numeral 4 denotes an optical path of striped pattern light reflected from the work 2 irradiated by the pattern light emitting means 1. Reference numeral 5 denotes a line sensor camera for converting the slit-like reflected light into an image signal, which is constituted by a CCD. Reference numeral 6 denotes a signal cable for transmitting an image signal generated by the line sensor camera 5 to image processing means, 7 denotes an A / D converter for converting the image signal into a digital signal, and 8 denotes at least one of the image signals. This is a line buffer memory that holds data of a scanning line.

9 is a shading correction circuit, 10 is a defect detection processing circuit, and 11 is a CPU for controlling the entire system.
Board, 12 a data bus, 13 an A / D converter 7
To an image processing device including the CPU board 11.

Next, the operation of the cylindrical object defect inspection apparatus according to the present embodiment will be described in detail with reference to the drawings. FIG.
As shown in the flowchart of FIG.
In the above, the work 2 is set so as to come into contact with a pair of rotary rollers 3 attached to the inspection jig.

Next, in step S2, the work 2 is rotated by the rotary roller 3. Next, in step S3, a regular pattern is projected on the surface of the work 2. This light projection is performed by irradiating the pattern light beam 4 from the pattern light projecting means 1 installed substantially parallel to the rotation axis of the work 2. The pattern light beam 4 thus projected is specularly reflected or scattered on the surface of the work 2, and is imaged by the line sensor camera 5.

FIG. 2 (a) shows an example of a pattern mask 1b in which transmissive portions and light-shielding portions constituting the pattern light projecting means 1 are alternately arranged. This is for projecting a light and shade striped pattern.

In the inspection as described above, if there is an irregularity defect on the surface of the work 2, as shown in FIG. 2B, the regular stripe pattern is disturbed. Sunahachi,
The density information on the surface of the work 2 is imaged for each scanning line by the line sensor camera 5 (for example, the number of pixels is 2048) in synchronization with the rotation roller 3 to generate an image signal (step S4). ).

An image signal generated by the line sensor camera 5 is input to an A / D converter 7 in an image processing device 13 via a signal cable 6. Then, the image signal input to the A / D converter 7 is converted into an 8-bit digital image signal (step S5), and the digitized image signal is saved in the image memory 8 (step S6).

Next, in step S7, the image data read out from the image memory 8 is subjected to shading correction, and the image data subjected to the shading correction is saved in the line memory 8 again. Next, the process proceeds to step S8, and a process of detecting a defective portion by the defect detection processing circuit 8 is performed.
Then, when the process of detecting a defective portion is completed, the defect inspection process is completed.

Next, the shading correction processing performed in step S7 will be described with reference to the flowchart of FIG. FIG. 3A shows image data of one scanning line. The horizontal axis corresponds to a pixel number, and the vertical axis indicates a digital signal output corresponding to each pixel. FIG. 3 (a)
As is clear from FIG. 7, the signal level of the pixels at both ends is lower than that of the center pixel. This phenomenon is a well-known shading phenomenon.

As shown in the flowchart of FIG. 7, when the shading correction processing is started, first, in the first step S21, the image data is loaded from the image memory 8 to the shading correction circuit 9, and the shading correction is performed. Is performed.

The above-described shading correction is achieved by executing a minimum / maximum value filter process described below. FIG. 4 shows a part of image data obtained by imaging and digitizing the pattern light beam 4 projected on the work 2 as shown in FIG. Such image data is loaded from the line buffer memory 8 to the shading correction circuit 9, and the minimum value of the difference between the image data of FIG. 4A and the image data of FIG. Are sequentially rewritten as shown in FIG. 4B (step S22). The above relationship is represented by the following equation (1).

A (x) = MIN [A (xi) −Bi] (i = 0, ± 1, ± 2) (Equation 1)

Here, A (x) denotes image data, Bi denotes a filter constant, and the value of i in the above (Equation 1) is represented by (−2, −1, 0, +1, +2) The value of [A (xi) -Bi] is calculated while changing as described above, and the minimum value is sequentially rewritten as a new value of the focused pixel.

Then, the process proceeds to a step S23, wherein a maximum spatial filtering process is performed. In this processing, the image data of FIG. 4B, which is the processing result of the minimum value filter, and FIG.
4C, the maximum value of the sum of the image data is sequentially rewritten as a new value to the pixel of interest as a new value. The above relationship is represented by the following equation (2).

C (x) = MAX [C (xi) −Bi] (i = 0, ± 1, ± 2) (2)

Here, C (x) represents image data, Bi represents a filter constant, and the value of i in the above (Equation 2) is represented by (−2, −1, 0, +1, +2). , The value of [c (xi) -Bi] is calculated, and the maximum value is sequentially rewritten as a new value of the pixel of interest.

Further, the size of the above-mentioned minimum / maximum value spatial filter must be equal to or larger than the interval between the above-mentioned striped patterns. That is, if the size of the filter is smaller than the interval between the striped patterns, an envelope portion such as a dotted line portion in FIG. 3A cannot be obtained, and therefore, data of the light amount distribution of illumination by shading can also be obtained. Absent.

Next, in step S24, the difference between the image data of FIG. 4A which is the original image data and the image data of FIG. 4C which is the result of the minimum / maximum value spatial filter processing is calculated. . The calculation result is as shown in FIG. It can be seen from the result of FIG. 4D that the shading phenomenon has been removed by the minimum / maximum value filter processing.

FIG. 5 shows image data on the line AA 'in FIG. By performing the above-described minimum / maximum value filter processing on the image data in which such a shading phenomenon has occurred, as shown in FIG. 3B, image data from which the influence of shading has been removed can be obtained.

Next, with reference to the flowchart of FIG. 8, a description will be given of the procedure of the process of detecting a defective portion performed in step S8 of the flowchart of FIG. When the defect detection processing circuit 10 starts the defect detection processing, first, in step S31, the image is binarized.

Next, in step S32, a contraction process for calculating a logical sum AND of the defective portion and the logical filter of FIG. 5D is performed. Next, in step S33, the logical product of the defective portion and the logical filter of FIG. 5D is obtained, as shown in FIG. 5B.

Subsequently, in step S34, FIG.
The exclusive OR of (a) and FIG. 5 (b) is obtained, and FIG.
A defective part is detected as shown in FIG. Next, in step S35, the data of the defect location obtained above is stored in the image memory 8.

The defect inspection apparatus for a cylindrical object according to the present embodiment performs the defect detection processing as described above, so that the same area is inspected a plurality of times without averaging or addition. Defect detection can be performed accurately, and the detection processing time can be significantly reduced.

Further, since the defect can be accurately detected without fixing the object to be inspected with high precision, the structure of the defect inspection apparatus can be simplified, and the cost for manufacturing the apparatus can be reduced. Can be. As a result, defect detection on a cylindrical object can be performed at low cost and with high performance.

(Other Embodiments of the Present Invention) The present invention is applied to a system composed of a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.), but is also applicable to an apparatus composed of one device. You may.

Further, in order to realize the functions of the above-described embodiments, a device connected to the above-mentioned various devices or a computer in a system is operated 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 implements the functions of the above-described embodiment, and the program code itself and means for supplying the program code to the computer are provided.
For example, a storage medium storing such a program code constitutes the present invention. As a storage medium for storing such a program code, for example, a floppy disk, hard disk, optical disk, magneto-optical disk, CD-ROM,
A magnetic tape, a nonvolatile memory card, a ROM, or 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. Needless to say, even when the functions of the above-described embodiments are realized in cooperation with application software or the like, such program codes are included in the embodiments of the present invention.

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

[0051]

As described above, according to the present invention,
While illuminating the surface of the inspected cylindrical object in a band along the longitudinal direction, an image signal is generated by imaging the illuminated area,
When detecting a defect present on the inspected cylindrical object based on the image signal, while projecting a regular pattern on the surface of the inspected cylindrical object, and on the surface of the inspected cylindrical object Image data is generated by capturing the projected regular pattern, the shading signal level in the image data is removed, and then the regularity of the projected pattern is evaluated. The defect detection can be accurately performed without averaging or adding, and the detection processing time can be greatly reduced.

Further, since the defect can be accurately detected without fixing the object to be inspected with high precision, the structure of the defect inspection apparatus can be simplified, and the cost for manufacturing the apparatus can be reduced. Can be. As a result, defect detection on a cylindrical object can be performed at low cost and with high performance.

[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 view showing a pattern mask as a pattern light projecting means and a light and shade stripe pattern projected on a defective portion of a work;

FIG. 3 is a diagram for explaining the removal of the influence of shading; the horizontal axis indicates a line sensor pixel number, and the vertical axis indicates a gray scale obtained by converting a line sensor signal into 8 bits.

FIG. 4 is a diagram illustrating the principle of a minimum / maximum value filter.

FIG. 5 is a diagram for explaining a shading correction process showing the principle of detecting a defective portion.

FIG. 6 is a flowchart showing an entire process.

FIG. 7 is a flowchart illustrating shading correction processing.

FIG. 8 is a flowchart of a process for detecting a defective portion.

[Explanation of symbols]

 Reference Signs List 1 light source 2 pattern mask 3 rotating roller 4 optical path 5 line sensor camera 6 signal cable 7 A / D converter 8 image memory 9 shading correction circuit 10 defect detection processing circuit 11 CPU board 12 data path 13 image processing device

Continued on the front page (51) Int.Cl. ⁶ Identification code FI H04N 1/403 H04N 1/40 103A

Claims (11)

[Claims] 1. A surface of a cylindrical object to be inspected is illuminated in a band along a longitudinal direction, an image of the illuminated area is captured to generate an image signal, and the image signal is generated on the cylindrical object to be inspected based on the image signal. A defect inspection apparatus for a cylindrical object that detects an existing defect, comprising: a pattern light emitting unit that emits a regular pattern on the surface of the inspected cylindrical object; Image data generating means for capturing a regular pattern to generate image data; shading correction means for removing a shading signal level in the image data; and converting the image data after shading correction into binary image data. Conversion means for converting; and evaluation means for evaluating the regularity of the light projection pattern in the image data converted into the binary image data. Defect inspection apparatus of a cylindrical object, characterized. 2. An illumination device for illuminating a circumferential surface on a cylindrical object to be inspected in a strip shape in the same direction as a longitudinal direction, and an imager for imaging an area to be illuminated on the circumferential surface to generate an image signal. A defect inspection apparatus for detecting a defect present on a circumferential surface on the inspected cylindrical object based on the image signal; and a pattern projecting means for projecting a regular pattern on the inspected cylindrical object. Imaging means for imaging the pattern projected on the inspected cylindrical object; A / D conversion means for converting an image signal obtained by the imaging means from an analog signal to a digital signal; Image data storage means for storing image data consisting of digital signals for a plurality of scanning lines, and a shading signal level in the image data stored in the image data storage means. A shading correction unit, a conversion unit that converts the image data after the shading correction into binary image data, and evaluates a regularity of a light projection pattern in the image data converted into the binary image data. A defect inspection apparatus for a cylindrical object, comprising: an evaluation unit. 3. The pattern light projecting means is constituted by the illuminating device and a striped pattern mask provided on a light projecting side of the illuminating device and comprising a plurality of transmissive portions and a light shielding portion of equal pitch. The defect inspection apparatus for a cylindrical object according to claim 1 or 2, wherein 4. A shading correction means for shading correction of image data obtained from the image data storage means by a minimum / maximum filter having a size larger than a width of a bright portion of the projected light and shaded stripe pattern. The defect inspection apparatus for a cylindrical object according to any one of claims 1 to 3, wherein: 5. The defect inspection apparatus for a cylindrical object according to claim 1, wherein the defect inspection apparatus is for inspecting a photosensitive drum of a copying machine. . 6. A cylindrical object to be inspected is illuminated in a strip shape along a longitudinal direction, an image of the illuminated illumination area is captured to generate an image signal, and the inspected cylindrical object is generated based on the generated image signal. In a defect inspection method for a cylindrical object for detecting a defect present on an object, a pattern light projection process of projecting a regular pattern on the surface of the inspected cylindrical object; Image data generation processing for generating image data by capturing a lighted regular pattern; shading correction processing for removing a shading signal level in the image data; binarizing the image data after the shading correction A conversion process of converting the image data into image data; and an evaluation process of evaluating the regularity of the light projection pattern in the image data converted into the binary image data. Defect inspection method of a cylindrical object, which comprises carrying out. 7. A cylindrical object to be inspected is illuminated in the form of a band along the longitudinal direction, an image of the illuminated region is captured to generate an image signal, and the cylindrical object to be inspected is generated based on the generated image signal. In the defect inspection method for a cylindrical object that detects a defect present on the cylindrical object, a pattern projection process of projecting a regular pattern on the cylindrical object to be inspected, and the pattern projected on the cylindrical object to be inspected, An imaging process for imaging, an A / D conversion process for converting an image signal obtained by the imaging process from an analog signal to a digital signal, and an image data comprising the A / D converted digital signals for a plurality of scanning lines. Image data storage processing to be stored in the storage means; shading correction processing to remove a shading signal level in the image data stored in the storage means; A conversion process of converting the image data after the shading correction into binary image data; and an evaluation process of evaluating regularity of a light projection pattern in the image data converted into the binary image data. A defect inspection method for a cylindrical object characterized by the following. 8. The pattern light projecting process is performed using a striped pattern mask including an illuminating device and a plurality of equal-pitch transmissive portions and light-shielding portions provided on the projecting side of the illuminating device. The defect inspection method for a cylindrical object according to claim 6 or 7, wherein: 9. The shading correction processing is performed by using image data obtained by the image data storage processing using a minimum / maximum filter having a size larger than a width of a light portion of the projected light and shaded pattern. The defect inspection method for a cylindrical object according to any one of claims 6 to 8, wherein the defect is inspected. 10. A storage medium storing a program for causing a computer to function as each of the above-described means. 11. A storage medium storing a program for causing a computer to execute the procedure of the cylindrical object defect inspection method according to any one of claims 6 to 9.