JP2008070273A - Apparatus and method for detecting surface defect - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To identify surface defects such as very small irregularities and protrusions and defects involving surface concentration changes of objects to be inspected by a simple constitution. <P>SOLUTION: Two illuminating means 2a and 2b irradiate approximately parallel line beams having different optical characteristics to a surface of an object to be inspected 4, and two imaging means 3a and 3b distinguishably receive reflected light having different optical characteristics of the illuminating means 2a and 2b. The amount of displacement between actual imaging locations of the imaging means 3a and 3b and assumed imaging locations, imaging conditions previously set for detecting defects, is computed on the basis of luminosity changes in signals from the imaging means 3a and 3b to shorten reading intervals when the imaging means 3a images lines in the surface of the object to be inspected 4 projected by the illuminating means 2a and 2b and inexpensively implement corrections of locational displacements of the imaging means 3a and 3b by a simple constitution. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a surface defect detection apparatus and a surface defect detection method for detecting a surface defect such as minute irregularities and protrusions of a measurement object and a defect accompanied by a change in surface concentration.

  Conventionally, it has been common to irradiate the surface of an object to be measured with light projected from a uniform illumination means and detect or inspect scratches, irregularities, dirt, etc. on the surface of an object from an image obtained from the reflected light distribution. Is the method that has been done. In particular, in the case of a flat object such as roll paper or a sheet or a cylindrical object, as shown in Patent Document 1, Patent Document 2, or Patent Document 3, a line sensor is used as an image sensor, and relative objects are relative to each other. A general method is to obtain a surface image by sub-scanning by movement or rotation.

  The line-shaped light is irradiated to the inspection object, the inspection object is rotated, the line-shaped light reflected by the inspection object is detected by the line sensor, and the defect processing is performed by image processing obtained by the line sensor. In the method to be performed, when the image is acquired at a position closer to the specularly reflected light, the change in the amount of light due to the surface shape becomes more intense, and the detection sensitivity for minute irregularities becomes higher. However, since the relative positional relationship between the reflected light and the line sensor changes due to distortion of the shape of the object to be inspected, uneven rotation, or vibration, the conventional surface defect detection apparatus cannot detect the position with high sensitivity.

In order to solve such a problem, the surface defect inspection apparatus disclosed in Patent Document 3 irradiates light on the surface of an object to be inspected from a position direction by a line-type illumination unit, and reflects or diffuses the light with a line sensor. In addition to detecting the reflection distribution reflected by the surface of the inspection object, the area sensor detects the relative position of the line sensor, the observation surface of the inspection object, and the line illumination means based on the information detected by the area sensor. Adjustment is made so that the line sensor is always at a fixed position with respect to the position of the reflected light.
Japanese Patent No. 3341963 Japanese Patent No. 3585225 JP 2004-279367 A

  As shown in Patent Document 3, in the method of detecting the reflected light distribution by the area sensor, in order to increase the tracking accuracy, it is necessary to increase the definition of the image and increase the imaging frame rate. However, an area sensor with a high resolution and a high frame rate is expensive, and the amount of image processing becomes enormous, which increases the price of the system.

  In addition, it is necessary to adjust or calibrate the relative positional relationship between a plurality of sensors, which causes a decrease in detection accuracy and an increase in maintenance man-hours due to a relative position shift.

  Furthermore, it is possible to detect a signal change with high sensitivity even for a minute shape change by arranging a sensor at a place where the light quantity change rate is high. In other words, there is a problem that it is impossible to discriminate whether it is a part or a minute density unevenness. Such distinction between protrusions and density unevenness is very important for checking a manufacturing process of a product when a defect occurs and sending out a stable product, and thus detection and distinction are highly desired.

  The present invention eliminates such problems, reduces the cost with a simple configuration, suppresses variations in detection performance due to changes in the relative position of multiple sensors, etc., and reduces unevenness, protrusions, etc. of the object to be measured. It is an object of the present invention to provide a surface defect detection apparatus and a surface defect detection method for identifying and detecting surface defects and defects with surface density changes.

  The surface defect detection apparatus of this invention irradiates light from the illumination means onto the surface of the inspection object that moves relative to the imaging means, sequentially captures the reflected light into the imaging means, and inputs the inspection object surface image. The apparatus includes a plurality of illumination means, a plurality of imaging means, and a defect detection processing unit, and the plurality of illumination means have different optical characteristics that are separable from each other and with respect to a main scanning direction of the imaging means. And the plurality of imaging means are constituted by line sensors that distinguish and receive reflected light having different optical characteristics of the plurality of illumination means, and the defect detection processing unit includes the plurality of imaging means. An imaging position that calculates a deviation amount between an actual imaging position of the plurality of imaging means and an assumed imaging position that is a preset imaging condition for detecting a defect from a change in brightness of a signal from the imaging means And is amount calculation means, and having an imaging position correction control means for controlling so that the deviation amount becomes the assumption imaging positions of the plurality of imaging means which is calculated by the imaging position deviation amount calculating means.

  According to another surface defect detection apparatus of the present invention, the surface of the inspection object that moves relative to the imaging means is irradiated with light from the illumination means, the reflected light is sequentially taken into the imaging means, and the surface of the inspection object surface is input. A defect detection apparatus comprising a plurality of illumination means, a plurality of imaging means, and a defect detection processing means, wherein the plurality of illumination means have different optical characteristics that are separable from each other, and the inspection object and the plurality of Arranged by line-shaped light sources arranged on different sides of the plane formed by the optical axis of the image pickup means and substantially parallel to the main scanning direction of the image pickup means, the plurality of image pickup means are different optical elements of the plurality of illumination means. The defect detection processing means detects defects and the actual imaging positions of the plurality of imaging means from the low frequency components of the signals from the plurality of imaging means. For Imaging position deviation amount calculating means for calculating a deviation amount from an assumed imaging position that is a preset imaging condition, and deviation amounts of the plurality of imaging means calculated by the imaging position deviation amount calculating means as the assumed imaging position. An imaging position correction control unit that controls the surface, a surface tilt detection unit that detects a local tilt of the surface of the object to be inspected from a high-frequency component of a signal from the one or more imaging units, and the surface tilt detection unit. It has a defect detection means for detecting a surface defect and a density defect of the inspection object from a local inclination of the detected inspection object surface.

  The imaging position correction control means performs position control for correcting the positional deviation in the sub-scanning direction of the imaging means from the average value component of the deviation amount distributed in the entire main scanning direction calculated by the imaging position deviation amount calculation means, Angle control is performed to correct the deviation of the inclination between the imaging means and the inspection object from the inclination component of the deviation amount distributed in the entire main scanning direction.

  Further, the defect detection means detects the unevenness of the surface of the inspection object and its height from the local inclination of the surface of the inspection object detected by the surface inclination detection means.

  Further, the plurality of illumination units are provided on the same side or different sides with respect to a plane formed by the object to be inspected and the optical axis of the imaging unit.

  According to the surface defect detection method of the present invention, surface defect detection is performed by irradiating light from the illumination unit onto the surface of the object to be inspected that moves relative to the image capturing unit, sequentially inputting the reflected light into the image capturing unit, and inputting the object surface image. A method of irradiating a surface of an inspection object with a line beam having different optical characteristics that are separable from a plurality of illumination units and substantially parallel to a main scanning direction of the imaging unit. The reflected light having different optical characteristics of the plurality of illuminating means is received in a distinguishing manner, and preset in order to detect defects and the actual imaging positions of the plurality of imaging means from the change in brightness of signals from the plurality of imaging means. Calculating an amount of deviation from an assumed imaging position serving as an imaging condition, and controlling the calculated deviation amounts of the plurality of imaging means to be the assumed imaging position to detect a defect in the inspection object. Do

  According to another surface defect detection method of the present invention, the surface of the inspection object that moves relative to the imaging means is irradiated with light from the illumination means, the reflected light is sequentially taken into the imaging means, and the surface of the inspection object surface is input. A defect detection method, wherein a plurality of images are obtained by irradiating a surface of an inspection object with a line beam having different optical characteristics that are separable from each other from a plurality of illumination units and substantially parallel to the main scanning direction of the imaging unit. In order to detect reflected light of different optical characteristics of the plurality of illuminating means by means, and detect defects of the actual imaging positions of the plurality of imaging means from low frequency components of signals from the plurality of imaging means A deviation amount from an assumed imaging position that is a preset imaging condition is calculated, and the calculated deviation amounts of the plurality of imaging means are controlled to be the assumed imaging position, and a high-frequency component of a signal from the imaging means Luo detect a local tilt of the object to be inspected surface, and detecting surface defects and density defect of the object from the local slope of the detected object to be inspected surface.

  Position control is performed to correct the positional deviation in the sub-scanning direction of the imaging unit from the calculated average component of the deviation amount distributed in the entire main scanning direction, and the imaging is performed from the slope component of the deviation amount distributed in the entire main scanning direction. Angle control for correcting the inclination between the means and the inspection object is performed.

  Further, the unevenness and the height of the surface of the inspection object are detected from the detected local inclination of the surface of the inspection object.

  Further, when the surface of the object to be inspected is formed with a curved surface, the positions of the plurality of illumination means are varied according to the curvature.

  The present invention irradiates a surface of an object to be inspected with a substantially parallel line beam with different optical characteristics from a plurality of illumination means, distinguishes and receives reflected light of different optical characteristics of a plurality of illumination means by a plurality of imaging means, The amount of deviation between the actual imaging position of the plurality of imaging means and the assumed imaging position that is a preset imaging condition for detecting a defect is calculated from the change in brightness of the signal from the imaging means. The readout interval when the lines on the surface of the object projected by the illuminating means are imaged by a plurality of imaging means can be shortened, and the positional deviation of the imaging means can be corrected with a simple configuration and inexpensive because of one-dimensional data. Can be realized.

  In addition, even if the reflectance of each part to be inspected is different or within one part, it is possible to correct the position of the imaging means so that it is stably at the assumed imaging position, and to accurately detect defects on the surface of the inspected object. Can be detected.

  Further, the signals from the plurality of imaging means are separated into a low frequency component and a high frequency component, the positional deviation amount of the imaging means is calculated with the low frequency component, the position of the imaging means is controlled with the calculated positional deviation amount, and the high frequency component is calculated. By detecting the local inclination of the surface of the inspection object and detecting the defect of the inspection object, it is possible to accurately detect the defect of the surface of the inspection object with a simple configuration.

  Further, position control is performed to correct the positional deviation in the sub-scanning direction of the imaging unit from the average component of the deviation amount distributed in the entire main scanning direction, and the imaging unit and the target are detected from the inclination component of the deviation amount distributed in the entire main scanning direction. By performing angle control for correcting the deviation of the tilt of the inspection object, it is possible to accurately detect defects on the surface of the inspection object even when the entire inspection object is tilted due to rotational shake or the like.

  Further, by detecting the unevenness and the height of the surface of the inspection object from the local inclination of the surface of the inspection object, the unevenness defect on the surface of the inspection object can be detected with high accuracy.

  In addition, when the surface of the inspection object is formed with a curved surface, the surface of the inspection object surface with a curved surface can be accurately detected by changing the positions of the plurality of illumination means according to the curvature. Can be detected.

  FIG. 1 is a configuration diagram of an optical system of a surface defect detection apparatus according to the present invention. As shown in the figure, the surface defect detection device detects various defects on the surface of a cylindrical object such as a photosensitive member used in an electrophotographic image forming apparatus or an object surface spreading in a plane. The system 1 has a plurality of, for example, two illumination means 2a and 2b and two imaging means 3a and 3b. Each of the illumination means 2a and 2b is composed of a line light source, has different optical characteristics that can be separated from each other, and projects a line beam onto the surface of the inspection object 4 that rotates in a cylindrical shape, for example. The two imaging means 3a and 3b are composed of line sensors, and receive the reflected light of the line beam irradiated on the inspection object 4 by the illumination means 2a and illumination means 2b.

  The illumination means 2a and 2b are arranged substantially parallel to the main scanning direction of the imaging means 3a and 3b. As a method of making the optical characteristics of the illumination means 2a and 2b different, for example, filters that transmit wavelengths corresponding to light of different wavelengths, projection light and deflection filters with different deflection states, or time division and project timing And so on. As the simplest method, there is a method in which color line sensors are used for the image pickup means 3a and 3b, and the illumination means 2a and 2b are made to correspond to the colors of the image pickup means 3a and 3b, respectively. The imaging means 3a and 3b are mounted on an imaging means moving device 5 that moves in the X direction orthogonal to the main scanning direction and rotates around the optical axis of the imaging means 3a.

  The defect detection processing unit of the surface defect detection apparatus includes image processing units 6a and 6b and an imaging position control unit 7, as shown in the block diagram of FIG. The image processing unit 6a processes a signal from the imaging unit 3a. The image processing unit 6b processes a signal from the imaging unit 3b. The imaging position control unit 7 includes an imaging position deviation amount calculation unit 8 and an imaging position correction control unit 9. The imaging position deviation amount calculation unit 8 is an imaging condition that is an imaging condition of the surface of the inspection object 4 based on the signal of the imaging unit 3a input from the image processing unit 6a and the signal of the imaging unit 3b input from the image processing unit 6b. A positional deviation amount between the actual imaging positions of the means 3a and 3b and an assumed imaging position which is an imaging condition set in advance to detect a defect is calculated. The imaging position correction control unit 9 includes the imaging conditions set in order to detect defects in the actual imaging positions of the imaging units 3 a and 3 b based on the positional deviation amounts of the imaging units 3 a and 3 b calculated by the imaging position deviation amount calculation unit 8. The imaging means moving device 5 is controlled so that the assumed imaging position becomes.

  With the surface defect detection apparatus configured as described above, the light that is projected from the illumination means 2a and 2b and reflected by the surface of the inspection object 4 is detected by the imaging means 3a and 3b, and the actual imaging of the imaging means 3a and 3b. The principle of detecting the positional deviation amount between the position and the assumed imaging position that is the imaging condition set for detecting the defect will be described.

  For example, when light is projected from one illumination unit 2a onto the inspection object 4 and reflected light is received by one imaging unit 3a, the setting reference position of the imaging unit 3a is the luminance distribution of the reflected light in FIG. As shown in FIG. 6, the distribution amount A of the reflected light from the surface of the inspection object 4 is defined by the deviation d from the highest luminance. When imaging is performed by providing the imaging means 3a at the reference position, if the rotational blur of the inspection object 4 occurs and the position of the bright line on the surface of the inspection object 4 is shifted, as shown in FIG. As a result, the distribution A of the reflected light from the inspection object 4 shifts, and the deviation amount d from the place with the highest luminance changes to the deviation amount d1 to change the detection sensitivity of the imaging means 3a. In Patent Document 3, the luminance distribution of the reflected light is detected and corrected by an area sensor.

  On the other hand, in the surface defect detection apparatus of the present invention, the optical system 1 is provided with two illumination means 2a and 2b and two imaging means 3a and 3b, and substantially parallel light is emitted from the illumination means 2a and 2b. 4 is projected onto the surface, reflected light by the projection light of the illumination means 2a is received by the imaging means 3a, and reflected light by the projection light of the illumination means 2b is received by the imaging means 3b. At this time, the setting reference positions of the imaging units 3a and 3b are based on the reflected light distribution A by the projection light of the illumination unit 2a and the projection light of the illumination unit 2b as shown in the luminance distribution of the reflected light in FIG. The reflected light distribution B is defined at an intermediate position where the luminance is highest. If the imaging means 3a and 3b are provided at the reference position, the amount of luminance observed by the imaging means 3a and 3b is the same. In this state, if the rotational shake of the inspection object 4 occurs and the position of each bright line on the surface of the inspection object 4 shifts, as shown in FIG. 4B, the distribution A of the reflected light due to the projection light of the illumination means 2a. The distribution B of the reflected light due to the projection light of the illumination unit 2b changes, for example, the luminance observation amount by the imaging unit 3a decreases, and the luminance observation amount by the imaging unit 3b increases. The image pickup means moving device 5 is controlled so that the luminance observation amounts by the image pickup means 3a and 3b are the same.

  The operation when the imaging position control unit 7 corrects the imaging positions of the imaging means 3a and 3b when the surface defect detection apparatus detects a defect of the inspection object 4 will be described with reference to the flowchart of FIG. To do.

  When rotating the inspection object 4 and projecting substantially parallel light from the illumination means 2a, 2b onto the surface of the inspection object 4 to detect defects in the inspection object 4, the two imaging means 3a, 3b The reflected light from the inspection object 4 is detected, and signals from the reflected light are output to the image processing units 6a and 6b, respectively (step S1). The image processing units 6 a and 6 b process the input signals, respectively, and output luminance signals to the imaging position deviation amount calculation unit 8 of the imaging position control unit 7. The imaging position deviation amount calculation unit 8 compares the two input luminance signals, and detects the actual imaging positions of the imaging means 3a and 3b that are imaging conditions of the surface of the inspection object 4 and the defect detection from the intensity of the two luminance signals. In order to perform this, a positional deviation amount with respect to an assumed imaging position, which is an imaging condition set in advance, is calculated and output to the imaging position correction control unit 9 (step S2). The imaging position correction control unit 9 causes the actual imaging positions of the imaging units 3a and 3b to become the assumed imaging positions that are the imaging conditions set for detecting a defect based on the input positional deviation amounts of the imaging units 3a and 3b. The position of the image pickup means 3a, 3b is corrected by controlling the image pickup means moving device 5 (step S3). Thus, after correcting the position of the imaging means 3a, 3b to be the assumed imaging position as the imaging condition, the defect detection process is executed (step S4).

  In this way, light substantially parallel from the illumination means 2a and 2b is projected onto the surface of the inspection object 4, and the reflected light from the inspection object 4 of the projection light from the illumination means 2a is detected by the imaging means 3a comprising a line sensor. The positional deviation of the image pickup means 3a, 3b is detected by the intensity of the luminance signal detected by the image pickup means 3a, 3b by detecting the reflected light from the inspection object 4 of the projection light from the illumination means 2b by the image pickup means 3b comprising a line sensor. When correcting the position of the image pickup means 3a, 3b by calculating the amount, the image pickup means 3a, 3b outputs line image data every time each line is picked up, so that the read interval compared to the area sensor having a long capture interval Is short. In addition, since it is one-dimensional data, it can be easily implemented in hardware and can be realized at low cost.

  Also, for example, in photoconductor drums used in copiers and laser printers, the reflectance varies depending on the individual parts due to variations in the coating amount of coating film members and changes in the process. Even if it is possible, it is difficult to detect between parts with constant sensitivity. In addition, some parts such as a fixing roller have different reflectances even within one part. Even in such a case, when projection light having different optical characteristics is projected from the illumination means 2a and 2b, the difference in reflectance affects both, and the intensity of the reflected light affected by the difference in reflectance is determined by the imaging means 3a, Since the detection is performed at 3b, the position of the image pickup means 3a and 3b can be corrected to be the stable image pickup position even if the reflectance differs among individual parts or within one part.

  The deviation of the reflected light distribution from the inspection object 4 also occurs due to the inclination of the surface of the inspection object 4. For example, as shown in the schematic diagram of FIG. 6, when projection light is projected from the illumination unit 2 onto the surface 4 a of the inspection object 4 and the brightness of the reflected light is detected by the imaging unit 3, the image is shown in FIG. Thus, as shown in FIGS. 6B and 6C, as compared with the normal case where the optical axis of the imaging means 3 is orthogonal to the surface 4a of the inspection object 4, the rotational shake of the inspection object 4 When the entire inspection object 4 is tilted due to the above or the like, the light incident on the imaging means 3 becomes brighter or darker depending on the tilted state. Further, even when there is a local inclination due to minute irregularities or protrusions on the surface of the inspection object 4, the light incident on the imaging means 3 becomes brighter or darker due to the shape change.

  As described above, when the reflected light from the inspection object 4 is detected by the imaging means 3a and 3b in a state where the entire inspection object 4 is inclined due to the rotational shake of the inspection object 4 and the like, the intensity varies as compared with the normal case. As a result, the defect cannot be detected with high accuracy. A description will be given of a second surface defect detection apparatus that detects defects by correcting the overall inclination of the inspection object 4.

  In the optical system 1 of the second surface defect detection apparatus, as shown in the block diagram of FIG. 7, the illumination unit 2b is arranged symmetrically with respect to the optical axis of the imaging units 3a and 3b with respect to the illumination unit 2a. . In this case, the reflected light reflected on the inspection object 4 by the illumination means 2a has a distribution as shown in FIG. 6, but the reflected light irradiated on the inspection object 4 by the illumination means 2b is shown in FIG. The distribution is different as shown in FIG. When the density change occurs, both the detected values increase or decrease, but when the shape changes, the increase / decrease direction is reversed.

  As shown in the block diagram of FIG. 9, the defect detection processing unit 10 of the second surface defect detection apparatus includes image processing units 6a and 6b, an imaging position control unit 7, a surface inclination detection unit 11, a defect detection unit 12, and An output unit 13 is included. The image processing unit 6a separates the low frequency component and the high frequency component by the spatial frequency obtained by processing the signal from the imaging unit 3a and performing Fourier transform, and outputs the low frequency component to the imaging position control unit 7, The high frequency component is output to the surface tilt detection unit 11. The image processing unit 6 b separates the low frequency component and the high frequency component based on the spatial frequency obtained by processing the signal from the imaging unit 3 b and performing Fourier transform, and outputs the low frequency component to the imaging position control unit 7. The imaging position control unit 7 includes an imaging position deviation amount calculation unit 8 and an imaging position correction control unit 9. The imaging position deviation amount calculation unit 8 is configured to detect the surface of the inspection object 4 based on the low frequency component of the signal of the imaging unit 3a input from the image processing unit 6a and the low frequency component of the signal of the imaging unit 3b input from the image processing unit 6b. The amount of positional deviation between the actual imaging position of the imaging means 3a and 3b, which is the imaging condition, and the assumed imaging position that is an imaging condition set in advance to detect a defect is calculated. The imaging position correction control unit 9 uses the average value component of the positional deviation amounts of the imaging units 3a and 3b calculated by the imaging positional deviation amount calculation unit 8 so as to correct the deviation in the sub-scanning direction. The position control is performed, and the angle control of the image pickup means moving device 5 is performed so as to cancel the deviation of the inclination of the image pickup means 3a, 3b and the inspection object 4 from the inclination component of the shift amount distributed in the entire main scanning direction. The surface tilt detection unit 11 detects the local tilt of the surface of the inspection object 4 based on the high frequency component of the signal of the imaging means 3a input from the image processing unit 6a. The defect detection unit 12 detects surface defects such as minute irregularities and protrusions on the surface of the inspection object 4 and density defects from the local inclination of the inspection object 4 detected by the surface inclination detection unit 11. The output unit 13 displays the surface defects detected by the defect detection unit 12 on the display device 14 and outputs them to an external storage device or the like.

  The operation when the defect of the inspection object 4 is detected while correcting the imaging position of the imaging means 3a, 3b with the second surface defect detection device will be described with reference to the flowchart of FIG.

  When detecting the defect of the inspection object 4 by projecting light from the illumination means 2a, 2b onto the surface of the inspection object 4 while rotating the inspection object 4, first, the two imaging means 3a, 3b are inspected. The reflected light from 4 is detected, and signals from the reflected light are output to the image processing units 6a and 6b, respectively (step S11). The image processing unit 6a separates the low frequency component into a low frequency component and a high frequency component based on the spatial frequency obtained by processing the signal from the imaging unit 3a and performing Fourier transform, and the low frequency component is captured by the imaging position control unit 7. It outputs to the quantity calculation part 8, and outputs a high frequency component to the surface inclination detection part 11. FIG. The image processing unit 6b separates the low frequency component and the high frequency component by the spatial frequency obtained by processing the signal from the imaging unit 3b and performing Fourier transform, and outputs the low frequency component to the imaging position deviation amount calculation unit 8. (Step S12). The high frequency component shown here is a component composed of a component on the high frequency side when the spatial distribution of the detected luminance in the main scanning direction is frequency-converted, and the signal C from the imaging means 3a shown in FIG. As shown in FIG. 11B, when the low frequency component D and the high frequency component E are separated, the low frequency component C corresponds to the entire change, and the high frequency component E corresponds to the local change.

  The imaging position deviation amount calculation unit 8 includes the imaging units 3a and 3b, which are imaging conditions for the surface of the inspection object 4, based on the low frequency components input from the imaging units 3a and 3b input from the image processing units 6a and 6b. A positional deviation amount between the actual imaging position and an assumed imaging position that is an imaging condition set in advance to detect a defect is calculated and output to the imaging position correction control unit 9 (step S13). The imaging position correction control unit 9 performs position control of the imaging means moving device 5 so as to correct the deviation in the sub-scanning direction from the input average value component of the deviation amount, and the deviation amount distributed in the entire main scanning direction. The angle control of the image pickup means moving device 5 is performed so as to cancel the deviation of the inclination of the image pickup means 3a, 3b and the inspection object 4 from the inclination component (step S14).

  When the imaging positions of the imaging units 3a and 3b are corrected, the reflected light from the inspection object 4 is detected by the imaging units 3a and 3b at the corrected imaging positions (step S15), and the signal from the imaging unit 3a is detected by the image processing unit 6a. Are separated into a low frequency component and a high frequency component, and the high frequency component is output to the surface tilt detection unit 11 (step S16). The surface inclination detection unit 11 detects the local inclination of the surface of the inspection object 4 from the input high frequency component and outputs it to the defect detection unit 12 (step S17). The defect detection unit 12 integrates the input local inclination signal of the inspection object 4 to detect surface defects and density defects such as minute irregularities and protrusions on the surface of the inspection object 4. The output unit 13 displays the defects detected by the defect detection unit 12 on the display device 14 and outputs them to an external storage device or the like (step S18).

  In this way, the relative position between the inspection object 4 and the imaging means 3a, 3b is corrected by the reflected light of the light projected from the illumination means 2a, 2b composed of line sensors onto the inspection object 4, and defects in the inspection object 4 are corrected. Since it detects, various defects of the inspection object 4 can be accurately detected with a simple configuration.

  In the above description, the case where the local inclination of the surface of the inspection object 4 is detected from the high frequency component of the signal imaged by the imaging means 3a has been described. However, the high frequency component of the signal imaged by the imaging means 3a and the imaging means 3b are used for imaging. The local inclination of the surface of the inspection object 4 may be detected using both the high frequency components of the signal. In this case, as shown in FIG. 12, the high-frequency component G of the signal imaged by the imaging unit 3b is opposite in phase to the high-frequency component F of the signal imaged by the imaging unit 3a. In this case, when the illumination means 2a, 2b or the imaging means 3a, 3b are tilted, the inclination H in the main scanning direction of the imaging means 3a and the inclination I in the main scanning direction of the imaging means 3b are as shown in FIG. It leans in reverse. Therefore, by correcting the inclination so that the inclination (first-order) component of the difference signal J between the two signals becomes zero, the imaging position can be controlled to be constant even with respect to the inclination change.

  In the above description, the illumination means 2b is arranged symmetrically with respect to the optical axis of the imaging means 3a and 3b with respect to the illumination means 2a, and the low frequency components of the signals from the imaging means 3a and 3b are used for the imaging means 3a and 3b. The case where the position and the angle are corrected and the local inclination of the inspection object 4 is detected with the high frequency component to detect the defect of the inspection object 4 has been described. However, the illumination means 2a and 2b are replaced with the imaging means 3a and 3b. In the same way, the positions and angles of the image pickup means 3a and 3b are corrected, the local inclination of the inspection object 4 is detected, and the defect of the inspection object 4 is detected. Can be detected.

  Further, when detecting the defect of the cylindrical inspection object 4 by arranging the illumination means 2a, 2b substantially parallel to the main scanning direction of the imaging means 3a, 3b, as shown in FIG. The reflection direction differs between the case where the diameter of the inspection object 4 is small and the case where the diameter of the inspection object 4 is large as shown in FIG. 14B, and reflection by the projection light of the illumination means 2a and 2b. The amount of deviation of the light distribution also changes. Therefore, in order to achieve a predetermined sensitivity at the position where the detection brightness by the illumination means 2a, 2b is the same, the interval between the illumination means 2a, 2b is changed according to the diameter of the object 4 to be examined. Adjust to image input conditions. In this way, by changing the interval between the illumination means 2a and 2b in accordance with the diameter of the object 4 to be inspected, the detection brightness of the illumination means 2a and 2b can be adjusted to be the same at the optimum sensitivity position. .

It is a block diagram of the optical system of the surface defect detection apparatus of this invention. It is a block diagram which shows the structure of the imaging position control part of a surface defect detection apparatus. It is a schematic diagram which shows the luminance distribution of the reflected light by one illumination means. It is a schematic diagram which shows the luminance distribution of the reflected light by two illumination means. It is a flowchart which shows the control operation | movement which corrects the imaging position of an imaging means. It is a schematic diagram which shows the luminance distribution of reflected light when a to-be-inspected object inclines. It is a block diagram of the optical system of the 2nd surface defect detection apparatus. It is a schematic diagram which shows the luminance distribution of the other reflected light when a to-be-inspected object inclines. It is a block diagram which shows the structure of the defect detection process part of a surface defect detection apparatus. It is a flowchart which shows the defect detection operation | movement of a to-be-inspected object. It is a schematic diagram which shows the signal from an imaging means, its low frequency component, and a high frequency component. It is a schematic diagram which shows the high frequency component of the signal from two imaging means. It is a schematic diagram which shows the inclination of the luminance signal output from the image pickup means in a state where two illumination means or image pickup means are inclined. It is a schematic diagram which shows the reflected signal from the cylindrical to-be-inspected object from which a diameter differs.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1; Optical system, 2; Illuminating means, 3; Imaging means, 4;
6; Image processing unit, 7; Imaging position control unit, 8; Imaging position deviation amount calculation unit,
9; Imaging position correction control unit, 10; Defect detection processing unit, 11; Surface tilt detection unit,
12; Defect detection unit, 13; Output unit, 14; Display device.

Claims (11)

A surface defect detection device that irradiates light from an illumination unit on the surface of an inspection object that moves relative to an imaging unit, sequentially captures the reflected light into the imaging unit, and inputs an inspection object surface image.
Having a plurality of illumination means, a plurality of imaging means and a defect detection processing unit;
The plurality of illuminating units are constituted by linear light sources having different optical characteristics that are separable from each other and substantially parallel to the main scanning direction of the imaging unit,
The plurality of imaging units are configured by line sensors that distinguish and receive reflected light of different optical characteristics of the plurality of illumination units,
The defect detection processing unit detects a deviation between an actual imaging position of the plurality of imaging units and an assumed imaging position serving as an imaging condition set in advance for detecting a defect, based on a change in brightness of signals from the plurality of imaging units. An imaging position deviation amount calculating means for calculating an amount; and an imaging position correction control means for controlling the deviation amounts of the plurality of imaging means calculated by the imaging position deviation amount calculating means to be the assumed imaging position. A surface defect detection device characterized by the above. A surface defect detection device that irradiates light from an illumination unit on the surface of an inspection object that moves relative to an imaging unit, sequentially captures the reflected light into the imaging unit, and inputs an inspection object surface image.
Having a plurality of illumination means, a plurality of imaging means and defect detection processing means,
The plurality of illuminating means are arranged on different sides having different optical characteristics that are separable from each other and on the plane formed by the optical axis of the object to be inspected and the plurality of imaging means, with respect to the main scanning direction of the imaging means. Consists of a substantially parallel line light source,
The plurality of imaging units are configured by line sensors that distinguish and receive reflected light of different optical characteristics of the plurality of illumination units,
The defect detection processing means includes an actual imaging position of the plurality of imaging means and an assumed imaging position serving as an imaging condition set in advance for detecting a defect from low frequency components of signals from the plurality of imaging means. An imaging position deviation amount calculating means for calculating a deviation amount; an imaging position correction control means for controlling the deviation amounts of the plurality of imaging means calculated by the imaging position deviation amount calculating means to be the assumed imaging position; A surface inclination detecting means for detecting a local inclination of the surface of the object to be inspected from a high-frequency component of a signal from one or a plurality of imaging means; a surface inclination detecting means detected from the local inclination of the surface of the inspecting object detected by the surface inclination detecting means; A surface defect detection apparatus comprising a defect detection means for detecting a surface defect and a density defect of an inspection object.   The imaging position correction control means performs position control for correcting the positional deviation in the sub-scanning direction of the imaging means from the average value component of the deviation amount distributed in the entire main scanning direction calculated by the imaging position deviation amount calculation means, The surface defect detection apparatus according to claim 2, wherein angle control is performed to correct an inclination between the imaging unit and the inspection object based on an inclination component of a deviation amount distributed in the entire main scanning direction.   The surface defect detection device according to claim 2 or 3, wherein the defect detection means detects the unevenness and the height of the surface of the inspection object from the local inclination of the surface of the inspection object detected by the surface inclination detection means.   5. The surface defect detection device according to claim 1, wherein the plurality of illumination units are provided on the same side with respect to a plane formed by an object to be inspected and an optical axis of the imaging unit.   The surface defect detection device according to claim 1, wherein the plurality of illumination units are provided on different sides with respect to a plane formed by an object to be inspected and an optical axis of the imaging unit. A surface defect detection method for irradiating light from an illuminating unit on a surface of an inspection object that moves relative to an imaging unit, sequentially capturing the reflected light into the imaging unit, and inputting an inspection target surface image,
Irradiate the surface of the object to be inspected with different optical characteristics separable from each other from a plurality of illumination means and substantially parallel to the main scanning direction of the imaging means,
A plurality of imaging means distinguishes and receives reflected light of different optical characteristics of the plurality of illumination means,
A deviation amount between an actual imaging position of the plurality of imaging units and an assumed imaging position that is a preset imaging condition for detecting a defect is calculated from a change in brightness of signals from the plurality of imaging units, and is calculated. A surface defect detection method, comprising: detecting a defect of an inspection object by controlling a shift amount of the plurality of imaging means to be the assumed imaging position. A surface defect detection method for irradiating light from an illuminating unit on a surface of an inspection object that moves relative to an imaging unit, sequentially capturing the reflected light into the imaging unit, and inputting an inspection target surface image,
Irradiate the surface of the object to be inspected with different optical characteristics separable from each other from a plurality of illumination means and substantially parallel to the main scanning direction of the imaging means,
A plurality of imaging means distinguishes and receives reflected light of different optical characteristics of the plurality of illumination means,
From the low-frequency components of the signals from the plurality of imaging means, calculate a deviation amount between the actual imaging positions of the plurality of imaging means and an assumed imaging position that is a preset imaging condition for detecting a defect. The amount of deviation of the plurality of imaging means is controlled to be the assumed imaging position, the local inclination of the surface of the inspection object is detected from the high frequency component of the signal from the imaging means, and the detected inspection object surface A surface defect detection method comprising detecting a surface defect and a density defect of an inspection object from a local inclination of the object.   Position control is performed to correct the positional deviation in the sub-scanning direction of the imaging unit from the calculated average component of the deviation amount distributed in the entire main scanning direction, and the imaging is performed from the slope component of the deviation amount distributed in the entire main scanning direction. 9. The surface defect detection method according to claim 8, wherein angle control is performed to correct the inclination between the means and the inspection object.   10. The surface defect detection method according to claim 8, wherein the surface irregularities and the height of the surface of the inspection object are detected from the detected local inclination of the surface of the inspection object.   11. The surface defect detection method according to any one of 8 to 10, wherein when the surface of the object to be inspected is formed with a curved surface, the positions of the plurality of illumination means are varied according to the curvature thereof.

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