JP2010044004A - Apparatus, method and program for detecting transmitted light, and method of manufacturing sheet material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To precisely determine a transmission factor of light transmitted through a detected measurement object, by removing effects of fluctuations in light intensity and unevenness in brightness of a light source while using a simple configuration. <P>SOLUTION: An apparatus is provided which includes: a surface light source 3 for emitting light to an area ranging from one end to the other end of a sheet material 9, along the width direction of the sheet material 9; a detection-use image capturing unit 1 which is disposed on a position enabling the emitted light from the surface light source 3 to be received through the sheet material 9, and detects the light transmitted through the sheet material 9; and a correction-use image capturing unit 2 which is disposed on a position enabling the emitted light from the surface light source 3 to be detected without using any path through the sheet material 9, and measures the light intensity of an emission plane 4 of the surface light source 3. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a transmitted light detection device, a transmitted light detection method, a transmitted light detection program, and a sheet material manufacturing method.

  2. Description of the Related Art Conventionally, when manufacturing various products in the form of sheets typified by paper and resin film, it is known to inspect the quality using transmitted light.

For example, in Patent Document 1, light is applied from the back surface of a sheet-like product placed on a light projecting device, and the surface is imaged with a CCD (charge coupled device) camera, and binarized with an appropriate threshold value. Surface unevenness is inspected by comparing images showing shading.
Further, in Patent Document 2, by combining and illuminating a halogen lamp and a rod-shaped light source, it is possible to reliably detect scratches existing on the front surface or the back surface of the sheet without being affected by the scattering direction of light transmitted through the sheet. It is said.
JP-A-6-147867 JP 2001-165864 A

However, in the apparatus as described above, the absolute transmittance of the measurement target cannot be measured, and the transmitted light is compared for each part of the measurement target. They are only inspecting for scratches.
In addition, simply detecting the light that has passed through the measurement object and measuring the amount of light, the amount of light emitted to the measurement object due to fluctuations in the light amount of the light source and uneven brightness, that is, the amount of light before passing through the measurement object Is not uniquely determined. For this reason, the amount of transmitted light changes depending on the timing of detecting the transmitted light and the part to be measured. Thus, if attention is paid only to the transmitted light, it is impossible to measure the absolute transmittance of the measurement object, and it is also difficult to measure the relative transmittance with high accuracy.

  The present invention has been made in view of the above-described circumstances, and with a simple configuration, it is possible to remove the influence of the light amount variation and luminance unevenness of the light source and to measure the transmittance of light transmitted through the measurement object with high accuracy. An object of the present invention is to provide a transmitted light detection device, a transmitted light detection method, a transmitted light detection program, and a sheet material manufacturing method using these.

  The transmitted light detection apparatus according to the present invention includes a surface light source unit that irradiates light at least in a range from one edge of the measurement object to the other edge along the width direction of the sheet-like measurement object. A detection imaging unit that detects light transmitted through the measurement object, and is installed at a position where the emitted light from the surface light source unit can be received via the measurement object; and the surface light source without passing through the measurement object And a correction imaging unit that measures the amount of light on the exit surface of the surface light source unit.

  In addition, the transmitted light detection method according to the present invention provides a light output from the surface light source unit at least in a range from one edge of the measurement object to the other edge along the width direction of the sheet-like measurement object. The detection imaging unit installed at a position that radiates light and receives the light emitted from the surface light source unit through the measurement object detects light that passes through the measurement object and passes through the measurement object. The surface light source measured by the correction imaging unit by measuring the light quantity of the emission surface of the surface light source unit by a correction imaging unit installed at a position for receiving the emission light from the surface light source unit In this method, the transmitted light amount detected by the detection imaging unit is corrected based on the light amount of the exit surface of the unit, and the transmittance of the light transmitted through the measurement object is obtained.

  Further, the transmitted light detection program according to the present invention allows a computer to detect light transmitted through a sheet-like measurement object, from at least one edge of the measurement object to the other along the width direction of the measurement object. The step of irradiating light from the surface light source unit to the range up to the edge of the surface, and the imaging unit for detection installed at a position where the emitted light from the surface light source unit can be received through the measurement object, A step of detecting light transmitted through the measurement object, and a light amount of the emission surface of the surface light source unit by a correction imaging unit installed at a position where the emission light from the surface light source unit can be received without passing through the measurement object As a program for executing the step of measuring.

  In addition, the sheet material manufacturing method according to the present invention includes at least a range from the surface light source unit to a range from one edge of the sheet material to the other edge along the width direction of the manufactured sheet material. Irradiate the emitted light, and detect the light transmitted through the sheet material by a detection imaging unit installed at a position where the emitted light from the surface light source unit is received through the sheet material, and the sheet material The surface measured by the correction imaging unit by measuring the light amount of the emission surface of the surface light source unit by a correction imaging unit installed at a position to receive the emission light from the surface light source unit without intervention Based on the amount of light on the exit surface of the light source unit, the amount of transmitted light detected by the detection imaging unit is corrected to determine the transmittance of light that passes through the measurement object, and is compared with a preset standard transmittance. Has an inspection process to inspect the sheet material There as a method.

  According to the present invention, it is possible to simultaneously measure the amount of light in a predetermined region on the exit surface of the surface light source unit serving as the light source and detect light that has exited from the region on the same exit surface and transmitted through the measurement target. it can. Thereby, it is possible to remove the influence of the light amount variation of the surface light source unit and the luminance unevenness of the emission surface, and to measure the transmittance of the light transmitted through the measurement object with high accuracy. In addition, the transmitted light detected through the arbitrary part of the measurement target is associated with which region on the exit surface of the surface light source unit is emitted, and the amount of light in the region on the exit surface is determined. By measuring, it is also possible to measure the local transmittance for an arbitrary region to be measured.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

[Transmission light detector]
First, an embodiment of a transmitted light detection apparatus according to the present invention will be described.
Here, FIG. 1 is a perspective view showing an outline of the transmitted light detection apparatus in the present embodiment. 2 is a side view of the transmitted light detection device shown in FIG. 1, and FIG. 3 is a plan view of the transmitted light detection device shown in FIG.

  The transmitted light detection apparatus shown in these drawings has a long sheet-like sheet material 9 as a measurement object. And the sheet | seat material 9 shown with the broken line in a figure is conveyed by the conveyance rollers 5 and 6 so that the longitudinal direction and conveyance direction may correspond. Thereby, the light which permeate | transmits the sheet | seat material 9 can be detected continuously.

  1, 2, and 3 also show three-dimensional orthogonal coordinates, in which the longitudinal direction of the sheet material 9 is the y-axis, and the width direction of the sheet material 9 orthogonal to this is the x-axis. . The direction perpendicular to the main surface of the sheet material 9 (the surface including the upper surface 9a or the lower surface 9b of the sheet material 9), that is, the normal direction of the main surface of the sheet material 9 is defined as the z-axis. In the following description, directions are indicated as appropriate using the three-dimensional orthogonal coordinates shown in the figure.

  In the illustrated example, on the lower surface 9 b side of the sheet material 9, at least a range from one edge of the sheet material 9 to the other edge along the width direction (x-axis direction) of the sheet material 9 ( Hereinafter, the surface light source unit 3 that irradiates light in the range (referred to as “the full width of the sheet material 9”) is provided. The surface light source unit 3 is not particularly limited as long as it irradiates the entire width of the sheet material 9, but the emission surface 4 preferably has a size exceeding the entire width of the sheet material 9. The reason for this will be described later.

  In addition, the imaging unit for detection 1 is installed on the upper surface 9 a side of the sheet material 9, that is, at a position where the emitted light from the surface light source unit 3 can be received via the sheet material 9. Thereby, the imaging part 1 for a detection can image the sheet material 9, and can detect the light which permeate | transmitted the sheet material 9. FIG.

  By the way, as described above, it is impossible to measure the absolute transmittance of the sheet material 9 simply by detecting the light transmitted through the sheet material 9 and measuring the amount of light. Further, due to the influence of the light amount fluctuation of the surface light source unit 3 and the luminance unevenness of the output surface 4, the light amount of the output surface 4 of the surface light source unit 3 serving as the light source, that is, the amount of light irradiated on the lower surface 9b side of the sheet material 9 It is not uniquely determined. For this reason, since the amount of transmitted light changes depending on the timing of detecting the transmitted light and the measurement site of the sheet material 9, it is difficult to measure the transmittance of the light transmitted through the sheet material 9 with high accuracy. .

  Therefore, in the present embodiment, as in the example shown in the figure, on the same side as the surface light source unit 3 is installed, at a position where the emitted light from the surface light source unit 3 can be received without the sheet material 9 being interposed, A correction imaging unit 2 is provided. The correction imaging unit 2 images the emission surface 4 of the surface light source unit 3 and thereby measures the light amount (light amount distribution) of the emission surface 4 of the surface light source unit 3.

  By doing in this way, in this embodiment, measurement of the light quantity of the predetermined area | region on the output surface 4 of the surface light source part 3 used as a light source, and it radiate | emits from the predetermined area | region on the same output surface 4. Detection of light transmitted through the sheet material 9 can be performed simultaneously. Therefore, by correcting the amount of light transmitted through an arbitrary part of the sheet material 9 based on the amount of light in the corresponding region of the exit surface 4 of the surface light source unit 3, the variation in the amount of light of the surface light source unit 3 and the exit surface 4 can be removed. Thereby, the absolute transmittance of the light transmitted through the sheet material 9 or the relative transmittance with high accuracy can be obtained.

  In addition, the transmitted light detected by transmitting through any part of the sheet material 9 is correlated with which region on the exit surface 4 is measured, and the amount of light in the region on the exit surface 4 is measured. By doing so, the local transmittance can be obtained for any part of the sheet material 9. As described above, the local transmittance can be continuously measured over the entire surface of the sheet material 9 by continuously detecting the transmitted light while conveying the sheet material 9.

  The surface light source unit 3 functions as a light source for both the detection imaging unit 1 and the correction imaging unit 2. Therefore, light can be supplied to the detection imaging unit 1 and the correction imaging unit 2 by a single light source without using a complicated optical system, and the transmittance of light transmitted through the sheet material 9 with a simple structure. Can be measured with high accuracy. Furthermore, since only one light source is required, when a plurality of light sources are used, it is necessary to consider individual differences for each light source, and the light passes through the sheet material 9 without such complexity. The light transmittance can be easily measured.

  In this embodiment, in order to obtain the transmittance of light that passes through the sheet material 9 with higher accuracy, the relative relationship between the detection imaging unit 1 and the correction imaging unit 2 with respect to the surface light source unit 3 is as equal as possible. It is preferable to do so.

Therefore, in the illustrated example, the surface light source unit 3 is installed with the emission surface 4 inclined. More specifically, the emission surface 4 of the surface light source unit 3 includes the normal line of the main surface of the sheet material 9 and is orthogonal or substantially orthogonal to a surface (yz surface) orthogonal to the width direction. The surface light source unit 3 is installed so that the normal line m of the exit surface 4 of the surface light source unit 3 is inclined with respect to the normal line of the main surface of the sheet material 9 parallel to the z axis.
By doing in this way, the emitted light from the surface light source unit 3 can reach both the detection imaging unit 1 and the correction imaging unit 2 in a balanced manner.

Here, the angle θ formed by the normal line of the main surface of the sheet material 9 parallel to the z-axis and the normal line m of the emission surface 4 of the surface light source unit 3 can be set as follows.
That is, the outgoing light from the surface light source unit 3 reaches both the detection imaging unit 1 and the correction imaging unit 2 in a well-balanced manner, and there is a problem in measuring the transmittance of light transmitted through the sheet material 9. It can be set in consideration of the installation space of the apparatus within the range. However, from the viewpoint of equalizing the emitted light from the surface light source unit 3 toward the detection imaging unit 1 and the correction imaging unit 2, the angle θ is preferably set to about 45 °.

  Further, if the surface light source unit 3 is installed with the emission surface 4 tilted, dust or dust is less likely to adhere to the output surface 4, and the frequency of stopping the device for maintenance of the surface light source unit 3 is reduced. Long-term stable operation is possible.

For example, the surface light source unit 3 houses a light source 15 such as a fluorescent tube or a light-emitting diode in a box-shaped housing 16 whose one surface is open as shown in the figure, and covers the opening of the housing 16. Thus, the two scattering plates 13 and 14 can be arranged in parallel. In such a surface light source unit 3, the light emitted from the light source 15 is emitted to the outside after sequentially passing through the scattering plates 13 and 14. Therefore, by appropriately adjusting the distance between the scattering plates 13 and 14 and the distance between the light source 15 and the scattering plate 13, the luminance peak due to the light source 15 is not observed on the emission surface 4. The uniformity of the brightness on 4 can be improved. The improvement in the uniformity of the luminance on the emission surface 4 contributes to the improvement of the accuracy in measuring the transmittance of light transmitted through the sheet material 9.
In the illustrated example, the outer surface of the scattering plate 14 is the emission surface 4.

  However, even with such a structure, it is difficult to make the luminance on the exit surface 4 completely uniform. When a portion overlapping the light source 15 is observed from the normal direction of the emission surface 4, the luminance of this portion tends to be higher than the luminance of other portions. Such a difference in luminance is one of the causes of luminance unevenness on the emission surface 4. It is preferable to incline the exit surface 4 in order to prevent the detection imaging unit 1 and the correction imaging unit 2 from imaging from the normal direction in which such a luminance difference is observed.

Further, in the illustrated example, the detection imaging unit 1, the correction imaging unit 2, and the surface light source unit 3 are relative positions of the detection imaging unit 1 and the correction imaging unit 2 with respect to the surface light source unit 3. These installation positions are determined so that the relationship is the same.
That is, the imaging unit 1 for detection is installed so that the imaging direction i is perpendicular or almost perpendicular to the main surface of the sheet material 9. At the same time, the correction imaging unit 2 is installed so that the imaging direction j is parallel or substantially parallel to the main surface of the sheet material 9. The distance L1 along the imaging direction i from the detection imaging unit 1 to the emission surface 4 of the surface light source unit 3 and the imaging direction j from the correction imaging unit 2 to the emission surface 4 of the surface light source unit 3 The installation positions of the detection imaging unit 1, the correction imaging unit 2, and the surface light source unit 3 are determined so that the distance L2 is the same or substantially the same.

In addition, the detection imaging unit 1 and the correction imaging unit 2 can be installed so that the same region on the emission surface 4 of the surface light source unit 3 is included in each field of view.
In the present embodiment, the visual field of the detection imaging unit 1 and the visual field of the correction imaging unit 2 are set to a region 10 on the emission surface 4 as shown in FIGS. 1 and 3. Thereby, the imaging part 1 for a detection and the imaging part 2 for correction | amendment are made to include the same location on the output surface 4 of the surface light source part 3 in a visual field. However, the visual field of the detection imaging unit 1 and the visual field of the correction imaging unit 2 may not completely match.

In the illustrated example, the emission surface 4 of the surface light source unit 3 is set to a size exceeding the entire width of the sheet material 9. At the same time, the region 10 corresponding to the field of view of both the detection imaging unit 1 and the correction imaging unit 2 is set larger than the entire width of the sheet material 9 so that the entire width of the sheet material 9 can be captured at a time. ing.
Therefore, the detection imaging unit 1 captures the exit surface 4 in the region 10 on the exit surface 4 that exceeds the entire width of the sheet material 9.

Thus, by installing the detection imaging unit 1 and the correction imaging unit 2 so as to include in the field of view the region exceeding the entire width of the sheet material 9 on the emission surface 4 of the surface light source unit 3, the higher The transmittance of light that passes through the sheet material 9 can be accurately measured.
That is, if the relative relationship between the detection imaging unit 1 and the correction imaging unit 2 with respect to the surface light source unit 3 is the same, the detection imaging unit is in a region exceeding the full width of the sheet material 9 on the emission surface 4. 1 and the amount of light equivalent to those of the correction imaging unit 2 should be measured. On the other hand, if there is a difference in the amount of light measured by both, there is also a difference in the relative relationship between the detection imaging unit 1 and the correction imaging unit 2 with respect to the surface light source unit 3. In this case, this may be taken into account when correcting the transmitted light amount detected by the detection imaging unit 1 based on the light amount of the emission surface 4 of the surface light source unit 3 measured by the correction imaging unit 2. Thereby, the transmittance | permeability of the light which permeate | transmits the sheet | seat material 9 can be calculated | required with higher precision.
In addition, when installing the light quantity adjustment member 7 mentioned later between the imaging part 2 for correction | amendment and the surface light source part 3, about the said area | region, about the light quantity measured by the imaging part 2 for correction | amendment, a light quantity adjustment member In consideration of the decrease in the light amount due to 7, the light amount measured by the detection imaging unit 1 may be compared.

In addition, when the transmittance of the sheet material 9 is low, excessive light emitted from the region exceeding the entire width of the sheet material 9 to the detection imaging unit 1 in the region 10 on the emission surface 4 is the sheet material 9. It may be a hindrance when accurately measuring the transmittance of light passing through the light.
In order to suppress a decrease in accuracy in this case, an area exceeding the entire width of the sheet material 9 in the area 10 on the emission surface 4 is directed from the area toward the detection imaging unit, for example, as shown in FIG. The surface light source unit 3 provided with the dimming members 26a and 26b for dimming the emitted light may be used.

  FIG. 7 is a perspective view showing another example of the surface light source unit used in the present embodiment, and FIGS. 7A and 7B are views with different viewpoints. Among these, FIG. 7A shows a state in which the installed surface light source unit is viewed from the z-axis direction side, similarly to FIG. In FIG. 7A, the light amount adjusting member 7 and the sheet material 9 are indicated by broken lines. 7A and 7B, the dimming plates 26a and 26b are hatched.

Further, the detection imaging unit 1 and the correction imaging unit 2 may be line sensor cameras each including an imaging element 11 and an optical system 12. In this case, the imaging directions i and j of the detection imaging unit 1 and the correction imaging unit 2 are the optical axis directions of the optical systems included in each.
The detection imaging unit 1 and the correction imaging unit 2 are line sensor cameras having the same specifications, so that the transmittance can be measured with higher accuracy. In order to enable more accurate measurement of the transmittance, it is preferable that the scanning cycle of the run sensor camera is synchronized between the detection imaging unit 1 and the correction imaging unit 2.

Although not particularly illustrated, the image sensor 11 can be a line sensor having a plurality of light receiving elements arranged in a line. The detection image pickup unit 1 is arranged so that the direction of the row of the plurality of light receiving elements constituting the image pickup element 11 is parallel to the width direction (x-axis direction) of the sheet material 9. Thereby, the imaging part 1 for a detection can image at least the full width of the sheet material 9 along the width direction (x-axis direction) of the sheet material 9.
The correction imaging unit 2 is also arranged so that the direction of the row of the plurality of light receiving elements is parallel to the width direction (x-axis direction) of the sheet material 9. Thereby, the visual field of the correction imaging unit 2 and the visual field of the detection imaging unit 1 can be matched.
The number of light receiving elements constituting the image sensor 11 is not limited. The number of light receiving elements is set according to the required resolution.

  The optical system 12 forms an image of a subject on the light receiving surfaces of a plurality of light receiving elements constituting the image sensor 11. In FIG. 1 and FIG. 2, the optical system 12 is configured by one lens element, but is not limited thereto. The optical system 12 may be composed of a plurality of lens elements.

  The distance L1 from the detection imaging unit 1 to the emission surface 4 of the surface light source unit 3 and the distance L2 from the correction imaging unit 2 to the emission surface 4 of the surface light source unit 3 are the most object side of each optical system 12. The distance from the point to the exit surface 4 along the optical axis of the optical system 12 can be obtained.

  Further, in order to adjust the aperture of the optical system 12 between the detection imaging unit 1 and the correction imaging unit 2, the amount of light incident on the detection imaging unit 1 and the amount of light incident on the correction imaging unit 2. It is preferable that and become comparable. For this purpose, a light quantity adjusting member 7 can be installed between the correction imaging unit 2 and the surface light source unit 3 as shown in FIGS.

  As the light amount adjusting member 7, when the light emitted from the surface light source unit 3 passes through the sheet material 9, the light amount is reduced to the correction imaging unit 2 as much as the amount of light decreases. A member capable of reducing the emitted light can be used.

  Moreover, when installing the light quantity adjustment member 7, the position is not specifically limited. However, the distance N2 from the emission surface 4 of the surface light source unit 3 to the light amount adjusting member 7 is set so that the imaging conditions of the detection imaging unit 1 and the correction imaging unit 2 are as equal as possible. It is preferable that the distance N1 from the emission surface 4 to the sheet material 9 is the same or substantially the same. At this time, the distance N2 is a distance along the imaging direction j of the correction imaging unit 2, and the distance N1 is a distance along the imaging direction i of the detection imaging unit 1.

  Furthermore, in the present embodiment, a second light amount adjusting member 8 indicated by a broken line in the drawing can be installed as necessary. The second light quantity adjustment member 8 may be installed in place of the light quantity adjustment member 7 or may be installed together with the light quantity adjustment member 7. The detection imaging unit 1 and the correction imaging unit 2 are not particularly limited as long as they do not contradict the purpose of making the imaging conditions as equal as possible.

In order to equalize the imaging conditions of the detection imaging unit 1 and the correction imaging unit 2, it is also effective to make the focal lengths of both the same.
For example, when the focal length of the optical system 12 of the imaging unit 1 for detection is set so that the focal point is on the upper surface 9a of the sheet material 9, the distance N2 from the emission surface 4 of the surface light source unit 3 is the surface light source unit. The light quantity adjusting member 7 is installed so as to be the same as or substantially the same as the distance N1 from the third exit surface 4 to the sheet material 9. At the same time, the focal length of the optical system 12 of the correction imaging unit 2 is set so that the surface of the light amount adjusting member 7 on the correction imaging unit 2 side is focused. However, such a mode is preferable when the pinhole inspection is performed simultaneously. When only the transmittance measurement of the sheet material 9 is performed, the focus of the optical system 12 of the detection imaging unit 1 is slightly shifted from the upper surface 9a of the sheet material 9, and the optical system of the correction imaging unit 2 is adjusted accordingly. It is often preferable to shift the 12 focus. This is because, when detecting transmitted light, it is possible to suppress variations in measured values by using an image in a defocused state.

Further, the transmitted light detection device in the present embodiment corrects the transmitted light amount detected by the detection imaging unit 1 based on the light amount of the emission surface 4 of the surface light source unit 3 measured by the correction imaging unit 2. A control unit is provided for executing a process for obtaining the transmittance of light transmitted through the sheet material 9.
Here, FIG. 4 is a block diagram showing a control system of the apparatus shown in FIGS. FIG. 5 is an explanatory diagram showing the concept of processing executed by the control unit shown in FIG.

  The control unit 17 includes a detection control unit 18, a correction control unit 19, a calculation unit 20, and an interface circuit (I / F) 21. With this configuration, the control unit 17 causes the detection imaging unit 1 and the correction imaging unit 2 to perform imaging, and corrects the signal output from the detection imaging unit 1 based on the signal output from the correction imaging unit 2. To do.

  The detection control unit 18 processes the image data output by the drive circuit 18a that drives the image sensor (line sensor) 11 (see FIG. 1) of the detection image capturing unit 1 and the image sensor 11 of the detection image capturing unit 1. And a processing circuit 18b. Similarly, the correction control unit 19 processes the image data output by the drive circuit 19a that drives the image sensor 11 (see FIG. 1) of the correction image capturing unit 2 and the image sensor 11 of the correction image capturing unit 2. And a circuit 19b.

  The drive circuits 18 a and 19 a generate various drive pulses for driving the image sensor 11 and output the generated drive pulses to the corresponding image sensor 1. In the present embodiment, the detection imaging unit 1 and the correction imaging unit 2 are set so that their scanning cycles are synchronized. Therefore, the drive circuit 18a outputs a synchronization signal (clock signal) CL to the drive circuit 19a. The drive circuit 19a generates various drive pulses based on the synchronization signal CL.

The processing circuits 18b and 19b perform noise removal processing, A / D (analog-digital) conversion processing, and the like on the imaging data output from the imaging device 11 to which the processing circuits 18b and 19b correspond, respectively, and calculate the processed data. Output to.
As described above, since the image sensor 11 is a line sensor, imaging data is output for each line. The imaging data is constituted by signal charges accumulated by a plurality of light receiving elements.

Data output from the processing circuit 18b (detection data) and data output from the processing circuit 19b (correction data) are as shown in the two graphs shown in the center of FIG. The vertical axis of these two graphs indicates the output level of each data. The output level corresponds to the amount of light incident on each light receiving element.
However, the output levels of the detection data and the correction data fluctuate gently because the luminance on the exit surface 4 (see FIGS. 1 to 3) of the surface light source unit 3 is not completely uniform. For this reason, the detection data and the correction data are curves.

  Also, the horizontal axes of the two graphs shown in the center of FIG. 5 indicate the positions on the light receiving surface of the image sensor 11. However, as described above, the image sensor 11 is arranged so that the row of the light receiving elements is parallel to the x-axis direction. Therefore, the horizontal axes of the two graphs correspond to positions along the x-axis direction of the region 10 on the emission surface 4.

  By the way, the detection imaging unit 1 can capture the entire width of the sheet material 9 at a time, but the imaging range is larger than the entire width of the sheet material 9 in the x-axis direction (see FIGS. 1 and 3). A part of the exit surface 4 is directly imaged. For this reason, as shown in FIG. 5, the output level of the detection data exceeds the full width of the sheet material 9, and greatly increases when the exit surface 4 is directly imaged. In the detection data in FIG. 5, data obtained by imaging within the full width of the sheet material 9 is represented by “W1”, and data obtained by directly imaging the exit surface 4 are “W2” and “W3”. ".

On the other hand, since the correction imaging unit 2 performs imaging on the entire area of the emission surface 4 via the light amount adjusting member 7 (see FIG. 1), the output level of the correction data is abruptly increased like the detection data. Will not fluctuate.
In the correction data in FIG. 5, “W1 ′” is data in which the position of the horizontal axis coincides with the data W1 of the detection data. Similarly, “W2 ′” and “W3 ′” are data in which the positions of the horizontal axes coincide with the detection data W2 and W3, respectively.

  When the processing circuits 18b and 19b of the detection control unit 18 and the correction control unit 19 output the data shown in FIG. 5, the calculation unit 20 performs calculation using both. Specifically, first, the arithmetic unit 20 removes the data W2 and W3 from the detection data and extracts only the data W1. Further, the arithmetic unit 20 similarly removes the data W2 ′ and W3 ′ from the correction data and takes out only the data W1 ′. Subsequently, the arithmetic unit 20 compares the data W1 and the data W1 ′, and subtracts the other from one of the positions where the horizontal axes match to calculate the data D (see FIG. 5).

The detection data that is affected by the luminance variation on the emission surface 4 is corrected by the correction data that is affected by the same luminance variation, and data D is obtained by this correction. Therefore, in the data D, the influence of the luminance variation on the emission surface 4 is removed. For this reason, the transmittance obtained from the Dake D is highly accurate.
In calculating the data D, if necessary, the transmittance obtained from the data D can be made more accurate by taking into account the difference between the data W2 and the data W2 ′ and the difference between the data W3 and the data W3 ′. As described above, it can be high.

  Then, after the calculation of the data D, for example, when the specific transmittance of the entire surface of the sheet material 9 is obtained, the calculation unit 20 obtains the data D by applying the data D to a relational expression or map prepared in advance. The transmittance is calculated according to the sampling number. Thereafter, the calculation unit 20 outputs data (output signal) specifying the calculated transmittance to the outside via the interface circuit (I / F) 21. Examples of the external output destination include a display device and another control device that manages the manufacturing process of the sheet material 9. Moreover, the relational expression and map for calculating the transmittance can be obtained by conducting an experiment in advance.

For example, when only the determination of whether or not the transmittance of the sheet material 9 is within the set range (that is, whether or not the thickness of the sheet material 9 is constant) is calculated, It is determined whether the level of D exceeds the set value. In this case, the arithmetic unit 20 outputs data (output signal) specifying the determination result to the outside via the interface circuit (I / F) 21.
In the present embodiment, a clock signal for instructing the timing of processing by the arithmetic unit 20 is input from the outside via the interface circuit 21.

  By the way, in this embodiment, the case where the whole width | variety of the sheet | seat material 9 is not uniform, or it needs to respond | correspond to the sheet | seat material 9 from which width | variety differs is assumed. In such a case, the calculation unit 20 may set the length of the data W1 according to the sheet material 9 having the smallest width. Moreover, the calculating part 20 may detect the fluctuation | variation point of the level of the data for a detection, and may set the length of the data W1 based on a detection result.

  As shown in FIG. 4, in the present embodiment, the control unit 17 also includes a light source driving unit 22 that drives the surface light source unit 3. The light source driving unit 22 adjusts the amount of power that the power supply device 24 supplies to the surface light source unit 3 based on a signal from the temperature sensor 23 attached to the surface light source unit 3. Although not particularly illustrated, the power supply device 24 also supplies power to the detection imaging unit 1, the correction imaging unit 2, and the control unit 17.

  Thus, the transmitted light detection apparatus in this embodiment can measure the transmittance of the entire surface of the sheet material 9, and can perform various determinations based on the transmittance. Therefore, if the apparatus according to the present embodiment is used, it is possible to determine the thickness of the sheet material 9, determine the presence / absence of pinholes, determine the presence / absence of surface unevenness, determine the presence / absence of scratches, and the like. .

  In the present embodiment, the transmittance of the sheet material 9 to be measured is not particularly limited. The sheet material 9 may be, for example, a permeable sheet material having a transmittance of nearly 100%, or may be a semi-permeable sheet material having a transmittance of about 50%. Further, the material for forming the sheet material 9 is not particularly limited. Examples of the material for forming the sheet material 9 include paper, resin, metal foil, felt, and the like. Furthermore, the structure of the sheet material 9 may be a single layer structure or a multilayer structure.

  In addition, the transmitted light detection apparatus in the present embodiment can detect transmitted light even for a sheet material having a non-uniform surface. Examples of such a sheet material include a sheet material on which a pattern is drawn by varying the thickness from the surroundings (by changing the transmittance), specifically, a watermarked paper. Moreover, the sheet | seat material used as the element | base of the electromagnetic wave absorption sheet | seat and radio wave diffraction sheet | seat (diffraction grating sheet | seat) which respond to a specific frequency is also mentioned. In addition, the sheet | seat material which comprises a radio wave lens is also mentioned.

  Here, an example of a sheet material on which a pattern is drawn by the transmittance variation will be described. FIG. 6 is a perspective view showing an example of a sheet material to be measured in the embodiment of the present invention. Unlike the sheet material 9 (see FIGS. 1 to 3), the sheet material 25 shown in FIG. 6 includes a watermark pattern 25a on the main surface. The watermark pattern 25a is formed so that its transmittance is different from that of the other portion 25b.

  Since the transmitted light detection apparatus in the present embodiment can locally measure the transmittance over the entire surface of the sheet material to be measured, when such a sheet material 25 is the measurement target, the shape of the pattern 25a is It can be determined whether it is as designed.

[Measurement method of transmitted light]
Next, an embodiment of the transmitted light measurement method according to the present invention will be described.
FIG. 8 is a flowchart showing the steps of the transmitted light measurement method in the present embodiment.
In addition, the transmitted light measurement method in this embodiment can be implemented using the transmitted light detection apparatus as described above with reference to FIGS.

  As shown in FIG. 8, in the transmitted light measurement method in the present embodiment, first, the conveyance of the sheet material 9 is started by the conveyance rollers 5 and 6. At the same time, the light source 15 of the surface light source unit 3 is turned on to irradiate at least the entire width of the sheet material 9 (step S1). In the present embodiment, step S <b> 1 is performed according to an instruction from the control unit 17. By step S1, the sheet material 9 is illuminated by the surface light source unit 3 from the lower surface 9b side while being conveyed. Further, the conveyance and irradiation in step S1 are continued until the processing is completed.

  Next, the detection imaging unit 1 images the illuminated portion of the upper surface 9b of the sheet material 9, and detects light transmitted through the sheet material 9 (step S2). Then, the correction imaging unit 2 images the emission surface 4 of the surface light source unit 3 and measures the light amount of the emission surface 4 of the surface light source unit 3 (step S3). In this embodiment, step S2 and step S3 are performed simultaneously. Steps S2 and S3 are also performed according to instructions from the control unit 17.

  After execution of step S2, the detection imaging unit 1 outputs imaging data to the processing circuit 18b. Moreover, after execution of step S3, the correction imaging unit 2 outputs the imaging data to the processing circuit 19b. Then, the processing circuit 18b generates detection data (see FIG. 5) and outputs it to the arithmetic unit 20. Similarly, the processing circuit 19b generates correction data (see FIG. 5) and outputs it to the arithmetic unit 20.

  Subsequently, the calculation unit 20 performs a calculation using the detection data and the correction data (step S4). Specifically, the arithmetic unit 20 extracts data W1 from the detection data, and further extracts data W1 ′ from the correction data. Then, the computing unit 20 calculates the data D by subtracting the data W1 from the data W1 ′. Further, the calculation unit 20 calculates the transmittance based on the calculated data D. In this way, the transmitted light amount detected by the detection image pickup unit 1 is corrected based on the light amount of the exit surface 4 of the surface light source unit 3 measured by the correction image pickup unit 1 and transmitted through the sheet material 9. Obtain the light transmittance.

  Next, the calculating part 20 outputs the data which specify the transmittance to the outside (step S5). By executing step S5, the transmittance of the sheet material 9 is displayed on the display device. Thereafter, the control unit 17 determines whether or not the user of the apparatus has instructed the end of the inspection (step S6).

  If the user has not instructed the end of the inspection, the control unit 17 executes steps S2 to S5 again. On the other hand, when the user instructs the end of the inspection, the control unit 17 ends the process.

  Thus, the transmittance of the entire surface of the sheet material 9 can be measured by executing the transmitted light detection method in the present embodiment. Furthermore, various inspections can be performed based on the measured transmittance.

[Production method of sheet material]
Next, an embodiment of a method for manufacturing a sheet material according to the present invention will be described.
The manufacturing method of the sheet material in the present embodiment is, for example, the transmitted light detection method described above with respect to the manufactured sheet material 9 through manufacturing processes such as a film forming process, a stretching process, a laminating process, and a surface treatment process. By carrying out, an inspection process is performed in which the transmittance of light transmitted through the sheet material 9 is obtained, and the quality of the sheet material 9 is inspected by comparing with a preset standard transmittance of light transmitted through the sheet material 9. It can be a method.

  By setting it as such a method, the transmittance | permeability of the light which permeate | transmits the manufactured sheet | seat material 9 can be calculated | required with high precision, and it becomes possible to test | inspect the quality accurately.

  Although the present invention has been described with reference to the preferred embodiment, it is needless to say that the present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the present invention. .

  For example, in the above-described embodiment, the surface light source unit 3 has been described as an example of a so-called direct-light type surface light source device, but the surface light source unit 3 is not limited thereto. For example, a side light type surface light source device including a light guide plate and a light source installed at a position facing a side surface of the light guide plate may be used.

  In the above-described embodiment, one line sensor camera is used as each of the detection imaging unit 1 and the correction imaging unit 2, but the present invention is not limited to this. The detection imaging unit 1 and the correction imaging unit 2 may each include a plurality of cameras. In this case, it is preferable that the plurality of cameras constituting each of the imaging units 1 and 2 are arranged along the width direction (x-axis direction) of the sheet material (measurement target) 9. Thereby, the resolution (resolution) in the direction is improved. In this case, the detection data and the correction data shown in FIG. 5 are obtained by combining the image data of these cameras. Furthermore, the imaging unit for detection 1 and the imaging unit for correction 2 can be other imaging units such as an area sensor camera, if necessary.

  As described above, the present invention can be widely used as a technique for measuring the transmittance of light irradiated from a light source to a measurement object with high accuracy by removing the influence of fluctuations in light amount and luminance unevenness of the light source. it can.

It is a perspective view showing the outline of the embodiment of the transmitted light detection device concerning the present invention. It is a side view of the apparatus shown in FIG. It is a top view of the apparatus shown in FIG. It is a block diagram which shows the control system of embodiment of the transmitted light detection apparatus which concerns on this invention. It is explanatory drawing which shows the concept of the process performed by the control system shown in FIG. It is a perspective view which shows an example of the sheet material used as a measuring object in this invention. It is explanatory drawing which shows the other example of a surface light source part. It is a flowchart which shows the process in embodiment of the transmitted light detection method which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Detection imaging part 2 Correction | amendment imaging part 3 Surface light source part 4 Output surface 5 Conveyance roller 6 Conveyance roller 7 Light quantity adjustment member 9 Sheet material 9a Upper surface of sheet material 9b Lower surface of sheet material 10 Area | region 26a corresponded to the visual field of an imaging unit Dimming plate 26b Dimming plate

Claims (18)

A surface light source unit that irradiates light in a range from at least one edge of the measurement object to the other edge along the width direction of the sheet-shaped measurement object;
An imaging unit for detection that is installed at a position where light emitted from the surface light source unit can be received via the measurement target, and detects light that passes through the measurement target;
Transmitted light detection, comprising: a correction imaging unit that is installed at a position where light emitted from the surface light source unit can be received without passing through the measurement target, and that measures the amount of light on the output surface of the surface light source unit apparatus. The exit surface of the surface light source unit includes a normal line of the main surface of the measurement object and is orthogonal to or substantially orthogonal to a surface orthogonal to the width direction of the measurement object,
The transmitted light detection apparatus according to claim 1, wherein the surface light source unit is installed such that a normal line of the emission surface of the surface light source unit is inclined with respect to a normal line of the main surface of the measurement target. The detection imaging unit is installed so that the imaging direction is perpendicular or substantially perpendicular to the main surface of the measurement target,
While installing the correction imaging unit so that the imaging direction is parallel or substantially parallel to the main surface of the measurement target,
The distance along the imaging direction of the detection imaging unit from the detection imaging unit to the emission surface of the surface light source unit, and the correction imaging unit from the correction imaging unit to the emission surface of the surface light source unit. The transmitted light detection apparatus according to claim 1, wherein the surface light source unit is installed so that a distance along the imaging direction is the same or substantially the same.   Claims wherein the detection imaging unit and the correction imaging unit are installed so that the same area on the emission surface of the surface light source unit is included in the respective fields of view of the detection imaging unit and the correction imaging unit. Item 4. The transmitted light detection device according to any one of Items 1 to 3.   The transmitted light detection apparatus according to claim 1, wherein the detection imaging unit and the correction imaging unit are line sensor cameras having the same specifications.   The transmitted light detection apparatus according to claim 5, wherein a scanning cycle of the line sensor camera is synchronized between the detection imaging unit and the correction imaging unit.   The transmitted light detection apparatus according to any one of claims 1 to 6, wherein a light amount adjustment member is installed between the correction imaging unit and the surface light source unit.   The light amount adjusting member is installed such that a distance from an emission surface of the surface light source unit to the light amount adjustment member is the same or substantially the same as a distance from the emission surface of the surface light source unit to the measurement target. 8. The transmitted light detection apparatus according to 7. The emission surface of the surface light source unit has a size exceeding the range from one edge along the width direction of the measurement object to the other edge,
The detection imaging unit and the detection unit so as to include a region exceeding the range from one edge along the width direction of the measurement target on the emission surface of the surface light source unit to the other edge. The transmitted light detection apparatus according to claim 1, wherein a correction imaging unit is installed.   Light emitted toward the detection imaging unit from a region exceeding the range from one edge along the width direction of the measurement object to the other edge of the emission surface of the surface light source unit The transmitted light detection device according to claim 9, wherein a light reducing member for reducing light is installed.   The light which permeate | transmits the said measuring object is continuously detected, conveying the said long measuring object so that the longitudinal direction and the conveyance direction may correspond. Transmitted light detection device.   Based on the light amount of the exit surface of the surface light source unit measured by the correction imaging unit, the transmitted light amount detected by the detection imaging unit is corrected to obtain the transmittance of light transmitted through the measurement target. The transmitted light detection apparatus according to any one of claims 1 to 11, further comprising a control unit. Along the width direction of the measurement object in the form of a sheet, irradiate the emitted light from the surface light source unit to a range from at least one edge of the measurement object to the other edge,
While detecting the light transmitted through the measurement object by the detection imaging unit installed at a position for receiving the light emitted from the surface light source unit through the measurement object,
By measuring the light amount of the exit surface of the surface light source unit by the correction imaging unit installed at a position for receiving the emitted light from the surface light source unit without passing through the measurement object,
Based on the light amount of the exit surface of the surface light source unit measured by the correction imaging unit, the transmitted light amount detected by the detection imaging unit is corrected to obtain the transmittance of light transmitted through the measurement target. And a transmitted light detection method.   The exit surface of the surface light source unit includes a normal line of the main surface of the measurement object and is orthogonal to or substantially orthogonal to a surface orthogonal to the width direction of the measurement object, and the main surface of the measurement object The transmitted light detection method according to claim 13, wherein the measurement object is irradiated with emitted light from the surface light source unit installed so that a normal line of the emission surface of the surface light source unit is inclined with respect to a normal line. . In order to detect the light transmitted through the sheet-like object to be measured,
Irradiating light from a surface light source unit along a width direction of the measurement object, at least in a range from one edge of the measurement object to the other edge;
Detecting light transmitted through the measurement object by a detection imaging unit installed at a position where the emitted light from the surface light source unit can be received via the measurement object;
Transmitting light for causing the correction imaging unit installed at a position where the emitted light from the surface light source unit can be received without passing through the measurement object to measure the light amount of the emission surface of the surface light source unit Detection program.   Based on the light amount of the exit surface of the surface light source unit measured by the correction imaging unit, the transmitted light amount detected by the detection imaging unit is corrected to obtain the transmittance of light transmitted through the measurement target. The transmitted light detection program according to claim 15, wherein the step is executed. Along the width direction of the manufactured sheet material, irradiate the emitted light from the surface light source unit at least in the range from one edge of the sheet material to the other edge,
While detecting the light transmitted through the sheet material by the detection imaging unit installed at a position to receive the emitted light from the surface light source unit through the sheet material,
By measuring the light amount of the exit surface of the surface light source unit by the correction imaging unit installed at a position for receiving the emitted light from the surface light source unit without passing through the sheet material,
Based on the light amount of the exit surface of the surface light source unit measured by the correction imaging unit, the transmitted light amount detected by the detection imaging unit is corrected to obtain the transmittance of light transmitted through the sheet material. A method of manufacturing a sheet material, comprising: an inspection step of inspecting the sheet material by comparing with a preset standard transmittance.   The exit surface of the surface light source unit includes a normal line of the main surface of the measurement object and is orthogonal to or substantially orthogonal to a surface orthogonal to the width direction of the measurement object, and the main surface of the measurement object The sheet material according to claim 17, wherein the measurement object is irradiated with the emitted light from the surface light source unit installed so that a normal line of the emission surface of the surface light source unit is inclined with respect to the normal line. Method.

Images