JP4694923B2 - Imaging method and imaging apparatus - Google Patents

Description

  The present invention relates to an image pickup method and an image pickup apparatus for picking up an image of a roller surface when, for example, a roller surface inspection of a sheet manufacturing apparatus is performed.

  Conventionally, when a sheet is continuously produced by extrusion coating, extrusion coating (EC), wet lamination, dry lamination, hot melt lamination, etc., as disclosed in Patent Document 1, a defect on the sheet is imaged by a CCD camera. And inspected.

  That is, the surface of the sheet is detected as a detection image by an image detection unit including a CCD camera, a light source, etc., a plurality of feature amounts of the detection image are extracted by a feature amount extraction unit, and the feature amount of the detection image is detected by a discrimination processing unit It is determined which defect type corresponds to the defect type definition area.

JP 2004-109069 A

  However, defects such as foreign matter and dirt on the sheet are relatively easy to detect because the difference in contrast is large compared to the non-defective part, but poor lamination such as wrinkles and irregularities is detected because the difference in contrast with the good part is small. There is a problem that it is difficult. Since such laminating defects such as wrinkles are caused mainly by foreign matter adhering to the surface of the roller, the present inventor images the surface of the rotating roller of the sheet manufacturing apparatus, and the occurrence of laminating defects is detected from the image. The idea was to detect, and the occurrence of defects was detected based on the image of the roller surface.

  However, while the sheet was manufactured while inspecting the surface of the roller, the image captured by the camera became unclear and the inspection became inaccurate.

  As a result of diligent research, the present inventor has found that the surface of the roller becomes unclear because the roller surface wears out as the sheet is continuously manufactured, so that the direction of reflection of the light source light deviates from the camera and is necessary for imaging. I came up with the idea that it was not possible to get enough light.

  The present invention has been made on the basis of such knowledge. The surface of the roller (3) is irradiated with light, and the reflected light from the surface of the roller (3) is received by the camera (8). In the imaging method for capturing an image of the surface of the roller, the displacement due to the abrasion of the surface of the roller (3) is detected, and the correction amount of the position of the camera (8) is calculated and output based on the detected displacement data. The position of the camera (8) is corrected by the output, and the light source (7) for irradiating the surface of the roller (3) and the reflected light from the surface of the roller (3) are received and the roller In the imaging device including the camera (8) that captures an image of the surface of (3), from the displacement detection sensor (18) that detects displacement due to wear of the surface of the roller (3), and the displacement detection sensor (18) The position of the camera (8) based on the displacement data of And a position adjustment mechanism (26, 29) for adjusting the position of the camera (8) by the output from the control unit (20). .

  According to the present invention, even if the surface of the roller (3) is worn due to the manufacture of the sheet (9), the displacement due to the wear of the surface of the roller (3) is detected by the displacement detection sensor (18), and the control unit (20) calculates and outputs the correction amount of the position of the camera (8) based on the displacement data from the displacement detection sensor (18), and adjusts the position of the camera (8) by the position correction mechanism (26, 29). Therefore, the camera (8) can always capture a clear image of the surface of the roller (3) with a sufficient amount of light. Thereby, the quality of the sheet | seat (9) manufactured, for example can be determined correctly.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

<Embodiment 1>
As shown in FIG. 1, a laminator 1 includes a metal cooling roller 2, a rubber nip roller 3 disposed in pressure contact with the cooling roller 2, a backup roller 4 that supports the nip roller 3, and not shown. A die head 5 for extruding the molten resin extruded from the extruder into a thin film, and a guide roller 6 for feeding a sheet laminated by the cooling roller 2 and the nip roller 3 are provided.

  The laminator 1 feeds an original fabric 9a such as a film or aluminum foil to the cooling roller 2 side, while feeding an original fabric 9b such as paper or film to the nip roller 3 side. A resin 9c (see FIG. 2) extruded from the die head 5 in a thin film shape with the nip roller 3 is used as a binder to form a continuous sheet 9. The continuous sheet is taken up by a take-up roller (not shown) through a guide roller 6.

  The laminator 1 is provided with an imaging device in order to detect the quality of the surface of the nip roller 3. That is, in the vicinity of the backup roller 4, a linear light source 7 such as an LED array that irradiates light on the surface of the nip roller 3 along the axial direction is disposed, and in the vicinity of the cooling roller 2, the surface of the nip roller 3. A monochrome line camera 8 that receives the reflected light at is arranged. When the surface of the nip roller 3 is irradiated with light from the light source 7 and the nip roller 3 rotates, the surface of the nip roller 3 is imaged by the line camera 8. Since the industrial line camera 8 generally does not have an autofocus function, an imaging point is determined manually.

  As shown in FIG. 2, when the foreign matter X adheres to the surface of the nip roller 3, defective lamination such as wrinkles and unevenness occurs in the sheet 9. Light is emitted from the light source 7 to the nip roller 3 which is a generation source of such a lamination failure, and the reflected light is incident on the line camera 8 to photograph the entire axial direction of the nip roller 3. Since the material of the nip roller 3 is rubber as described above, the reflectance is low.

  FIG. 3 shows a captured image of the foreign matter adhering to the surface of the nip roller 3 and luminance data of the image. The adhering foreign matter is mainly a black foreign matter such as a resin such as a thermoplastic resin, a carbide of the resin, or hair. Further, the surface of the nip roller 3 may be streaked due to printed matter or the like, but these stains do not cause product defects.

  As shown in FIG. 3, a foreign matter having a high reflectance such as resin or adhesive attached to the surface of the nip roller 3 is imaged white on the image. And when a foreign material is resin and the resin is detected, it detects by making a foreign material shine using regular reflection. Further, the black foreign matter adhering to the surface of the nip roller 3 is captured as a black image. When photographing a foreign matter having a high reflectance such as a resin or an adhesive, the influence of dirt on the surface of the nip roller 3 is reduced by reducing the regular reflection angle between the line camera 8 and the light source 7 as much as possible. Can be reduced. Actually, the angle is set to 10 to 40 degrees from the viewpoint of arrangement of the rollers, and in this embodiment, the angle is set to 30 degrees.

  Next, a control system of the imaging apparatus will be described.

  As illustrated in FIG. 4, the imaging device 10 includes an image input unit 11, a control device 12, a display unit 15, and an external output unit 16.

  As shown in FIG. 1, the image input unit 11 includes the light source 7 and the line camera 8. The image input unit 11 irradiates light from the light source 7 arranged linearly at a predetermined interval with respect to the axial direction of the nip roller 3. The reflected light is incident on the linear line camera 8 to capture the captured image in the entire axial direction of the nip roller 3.

  The control device 12 includes an image preprocessing unit 13 as luminance data extraction means and a determination processing unit 14 as determination means. The image preprocessing unit 13 performs preprocessing on the captured image captured by the image input unit 11. Specifically, the brightness rapidly changes from the captured image captured by the image input unit 11 by a high-pass filter. The portion to be extracted is extracted as luminance data.

  The determination processing unit 14 determines whether the luminance data extracted by the image preprocessing unit 13 is within a preset threshold value. The threshold value is set to a value at which the light and dark portion of the captured image changes abruptly to a predetermined value or more. The threshold value of the luminance data of the bright portion is set to the first binarization level shown in FIG. The threshold value is the second binarization level shown in FIG. Specifically, the threshold value is not set based on luminance data for dirt on the nip roller 3, but is used for luminance data for foreign matter that generates wrinkles, unevenness, etc. on the sheet when adhered to the nip roller 3 and being laminated. Set based on.

  In addition, when the brightness data of the bright part exceeds the first binarization level, the determination processing unit 14 determines that a foreign substance having a high reflectance is attached, and the brightness data of the dark part is the second brightness data. When the binarization level is exceeded, it is determined that black foreign matter is attached.

  The display unit 15 displays the determination result of the determination processing unit 14 on a monitor, and displays a foreign object image when it is determined as a foreign object.

  When the determination processing unit 14 determines that the external output unit 16 is a foreign object, the external output unit 16 emits an alarm sound by a buzzer or the like, and turns on a red lamp among red, blue, and yellow lamps.

  The control system operates as follows.

  As shown in FIG. 5, first, in step S <b> 1, light is emitted from the light sources 7 arranged linearly with respect to the axial direction of the nip roller 3, and the reflected light is incident on the linear line camera 8. The captured image is captured in the entire axial direction.

  Next, in step S2, the image preprocessing unit 13 extracts a portion where the luminance of the nip roller 3 is rapidly changed as luminance data from the captured image captured by the image input unit 11 by a high-pass filter.

  Further, in step S3a, the determination processing unit 14 sets a threshold value of luminance data in advance. That is, in step S3a, a value at which the bright portion of the captured image changes abruptly to a predetermined value or more is set as a threshold value for the first binarization level. In step S3b, the determination processing unit 14 sets a value at which the dark portion of the captured image rapidly changes to a predetermined value or more as a second binarization level.

  In step S4a, it is determined whether or not the first binarization level has been exceeded. If the first binarization level has been exceeded (step S4a; Yes), a nip roller as shown in FIG. When it is determined that a foreign matter having a high reflectance is attached to the surface 3 and the first binarization level is not exceeded (step S4a; No), the process returns to the captured image capturing process in step S1. In step S4b, it is determined whether or not it is equal to or lower than the second binarization level. If it is equal to or lower than the second binarization level (step S4b; Yes), a nip roller as shown in FIG. 3, it is determined that black foreign matter is attached, and when the second binarization level is exceeded (step S <b> 4 b; No), the process returns to the captured image capturing process of step S <b> 1.

  Next, in step S <b> 5, the determination processing unit 14 detects a highly reflective foreign matter or black foreign matter attached to the nip roller 3.

  Further, in step S6, the control device 12 performs a labeling process in which a foreign matter having high reflectance and a black foreign matter are regarded as one block of foreign matter.

  In step S <b> 7, the control device 12 calculates the number of pixels of the foreign matter regarded as one block subjected to the labeling process. Here, when the calculated number of pixels is large, it is determined that the foreign matter attached to the nip roller 3 is large, and when the calculated number of pixels is small, it is determined that the foreign matter attached to the nip roller 3 is small.

  Next, in step S8, the control device 12 determines whether or not the foreign substance inspection process is finished, and when the inspection process is finished (step S8; Yes), the whole process is finished. If the inspection process does not end (step S8; No), the process returns to the captured image capturing process in step S1, and the inspection process is executed again.

  As described above, the surface of the nip roller 3 is worn out while the sheet is continuously produced by the laminator, so that the surface image of the nip roller 3 becomes unclear and the accuracy of the inspection is lowered. In order to prevent this, the imaging apparatus includes a camera position correction apparatus described below.

  As shown in FIGS. 1 and 7, the camera position correction device 17 is based on a displacement reading unit 19 having a displacement detection sensor 18 that detects displacement due to wear on the surface of the nip roller 3, and displacement data from the displacement reading unit 19. A control unit 20 that calculates and outputs a correction amount of the position of the line camera 8, a display unit 21 that displays the correction amount, and a position correction mechanism that corrects the position of the line camera 8 based on the output from the control unit 20. And an external output unit 22.

  The displacement detection sensor 18 is specifically a laser displacement sensor, and is disposed so as to face the surface of the nip roller 3 in the vicinity of the nip roller 3 as shown in FIG. The distance to the surface of the nip roller 3 is measured by the displacement detection sensor 18, and as a result, a decrease in diameter due to wear of the surface of the nip roller 3 is detected.

  The control unit 20 is specifically a computer, and calculates a radius of the nip roller 3 from the displacement read by the displacement detection sensor 18 and the line camera 8 based on the radius obtained by the calculation unit 23. And a position correction table 24 that calculates and outputs a position correction amount. The position correction table 24 stores in advance the appropriate position of the line camera 8 corresponding to various radii of the nip roller 3 as data.

  The display unit 21 is a monitor, for example, and is provided as necessary. The operator can know, for example, the degree of wear on the surface of the nip roller 3 by the display on the display unit 21.

  The position correction mechanism of the external output unit 22 includes an inclination angle correction unit of the line camera 8 and a line camera focus correction unit.

  As shown in FIG. 8, the tilt angle correction unit of the line camera 8 specifically includes a servo motor 26 for tilting the table 25 on which the line camera 8 is placed together with the table 25. The table 25 is supported on the frame 30 of the laminator 1 by an axis (not shown) parallel to the axis of the nip roller 3, and this axis is rotated together with the table 25 by a servo motor 26 to change the elevation angle of the line camera 8. It has become.

  The line camera focus correction unit includes a ball screw 27 that extends substantially parallel to the optical path of the reflected light and is screwed into the housing of the line camera 8. The ball screw 27 is rotatably supported by the table 25, and a servo motor 29 is connected to one end of the ball screw 27 through gears 28a and 28b as transmission devices. The housing of the servo motor 29 is held on the table 25. The ball screw 27 is rotated by the drive of the servo motor 29, and the line camera 8 moves on the optical path. It is also possible to connect the shaft of the servo motor 29 to the ball screw 27 via a coupling and omit the gears 28a and 28b.

  Desirably, the position correction mechanism is held together with the line camera 8 and the light source 7 on a frame 30 that holds the nip roller 3. Thereby, even when the nip roller 3 moves in the laminator 1, an appropriate camera position can be corrected.

  The camera position correcting device 17 operates as follows.

  As shown in FIG. 9, in step S11, the surface of the nip roller 3 rotating from the displacement detection sensor 18 is irradiated with laser light, and the reflected light is received from the displacement detection sensor 18 to the surface of the nip roller 3. Is continuously detected as a change in the diameter of the nip roller 3.

  In step 12, the calculation unit 23 of the control unit 20 calculates the radius of the nip roller 3 from the displacement read by the displacement detection sensor 18.

  In step 13, based on the radius of the nip roller 3 calculated by the calculation unit 23, the position correction table 24 calculates the tilt angle of the line camera 8 and the amount of focus correction and outputs it to the external output unit 22.

  In step 14, the tilt servomotor 26 and the focusing servomotor 29 in the position correction mechanism of the external output unit 22 are driven to tilt the line camera 8 or move it on the optical path. With this correction, the reflected light from the surface of the nip roller 3 reaches the line camera 8 with a sufficient amount of light, and a clear image is captured.

<Embodiment 2>
In the second embodiment, the position correction table 24 (see FIG. 7) in the first embodiment is omitted, and a predefined arithmetic expression is used instead.

  An example of this arithmetic expression will be described as follows.

ただし、ｒ₁、ｒ₂はレーザ変位センサで測定した値から算出可能である。 As shown in FIG. 11, if the radius of the nip roller is changed by Δr, Δr is given by the following equation (1).

However, r ₁ and r ₂ can be calculated from values measured by a laser displacement sensor.

同様に点Ｂを撮像している場合のラインカメラの仰角θ₂は、次式(3)で与えられる。

The elevation angle θ1 of the line camera when imaging point A is given by the following equation (2):

Similarly, the elevation angle θ ₂ of the line camera when the point B is imaged is given by the following equation (3).

Thereby, the angle correction amount Δθ is obtained from the following equation (4).

Assuming that the length of the line segment OA is z ₁ and the length of the line segment OB is z ₂ , the following equations (5) and (6) are obtained.

Therefore, the position correction amount Δz in the optical path direction of the line camera can be obtained from the following equation (7).

  According to this image pickup apparatus, as shown in FIG. 10, in step S15, the surface of the nip roller 3 rotating from the displacement detection sensor 18 is irradiated with laser light, and the reflected light is received to detect the displacement detection sensor. The distance from 18 to the surface of the nip roller 3 is continuously detected as a change in the diameter of the nip roller 3.

  In step 16, the calculation unit 23 of the control unit 20 calculates the radius of the nip roller 3 from the displacement read by the displacement detection sensor 18. Based on this radius, Δθ and Δz are obtained from the above calculation formula, and the correction amount of the tilt angle of the line camera 8 and the correction amount of focusing are output to the external output unit 22.

  In step 17, the tilt servo motor 26 and the focusing servo motor 29 in the position correction mechanism of the external output unit 22 are driven to tilt the line camera 8 or move it on the optical path. By this correction, the reflected light from the surface of the nip roller 3 reaches the line camera 8 with a sufficient amount of light, and a clear image of the surface of the nip roller 3 is captured.

  The present invention is not limited to the first and second embodiments. For example, in the first and second embodiments, the roller to be imaged is a rubber nip roller. It can also be applied to rollers made of resin, rubber, wood, plastic and paper. In the first and second embodiments, the example in which the imaging device according to the present invention is applied to a laminator that performs extrusion coating has been described, but the present invention is also applicable to other laminators other than extrusion coating, Further, the present invention is not limited to a laminator, and can be applied to various printing apparatuses and drawing apparatuses. Furthermore, although steps S11 to S14 in the first embodiment and steps S15 to S17 in the second embodiment are all open-loop control, semi-closed loop control and closed-loop control are performed by installing the sensor at a desired location. It is within the scope of the present invention to appropriately change to loop control. Furthermore, the arithmetic expression used in Embodiment 2 is only an example, and other arithmetic expressions can be used.

It is a schematic block diagram of the laminator to which Embodiment 1 is applied. FIG. 3 is an explanatory diagram illustrating a state in which foreign matter adheres to the nip roller in the first embodiment. FIG. 3 is an explanatory diagram illustrating a captured image of foreign matter attached to a nip roller and luminance data of the image in the first embodiment. 2 is a block diagram illustrating a control system of the imaging apparatus according to Embodiment 1. FIG. 3 is a flowchart illustrating an operation of the imaging apparatus according to the first embodiment. (A) is explanatory drawing which shows the determination result in the 1st binarization level, (B) is explanatory drawing which shows the determination result in the 2nd binarization level. 3 is a block diagram illustrating a control system of a correction device in the imaging apparatus according to Embodiment 1. FIG. It is the schematic which shows an example of the position correction mechanism for correct | amending a camera position. It is a flowchart which shows the correction | amendment operation | movement of a camera position. It is a flowchart which shows the other aspect of the correction | amendment operation | movement of a camera position. It is explanatory drawing which shows the calculation principle of the correction amount used with the flowchart of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 3 ... Nip roller 7 ... Light source 8 ... Line camera 18 ... Displacement detection sensor 20 ... Control part 26 ... Servo motor for inclination 29 ... Servo motor for focusing

Claims (8)

  In an imaging method of irradiating light on a roller surface and receiving reflected light from the roller surface with a camera to capture an image of the roller surface, displacement due to wear on the roller surface is detected, and the camera is based on the detected displacement data An imaging method, wherein a position correction amount is calculated and output, and the camera position is corrected by the output.   2. The imaging method according to claim 1, wherein a correction amount of the camera position is obtained from a position correction table based on the detected displacement data and output.   2. The imaging method according to claim 1, wherein a correction amount of the camera position is obtained from a predetermined arithmetic expression based on the detected displacement data and output.   A displacement detection sensor for detecting displacement due to wear of the roller surface in an imaging apparatus including a light source that irradiates light on the roller surface and a camera that receives reflected light from the roller surface and captures an image of the roller surface; An imaging apparatus comprising: a control unit that calculates and outputs a correction amount of a camera position based on displacement data from a displacement detection sensor; and a position correction mechanism that corrects the camera position based on an output from the control unit.   5. The imaging apparatus according to claim 4, wherein brightness data extracting means for extracting a change in brightness of an image captured by the camera as brightness data, whether the brightness data is within a preset threshold, and the threshold An image pickup apparatus comprising: a determination unit that determines that a foreign object is attached to the roller in the case of outside.   6. The imaging apparatus according to claim 4, wherein the position correction mechanism includes a camera tilt correction unit.   The imaging apparatus according to claim 6, wherein the position correction mechanism further includes a camera focus correction unit. The imaging apparatus according to any one of claims 4 to 7, the imaging apparatus being characterized in that the specular reflection angle of the light source and the camera in the range of 10 to 40 degrees.

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