WO2015045434A1

WO2015045434A1 - Distortion measurement system for transparent film

Info

Publication number: WO2015045434A1
Application number: PCT/JP2014/052431
Authority: WO
Inventors: 研治田中
Original assignee: 研治田中
Priority date: 2013-09-24
Filing date: 2014-02-03
Publication date: 2015-04-02
Also published as: JP2015064204A; JP5649705B1

Abstract

A distortion measurement system provided with a plurality of light sources (1_-1-1_-n), a plurality of types of polarizing filters (2_-1-2_-n) alternatingly positioned in relation to the plurality of light sources (1_-1-1_-n), an image sensor (3) for capturing light which has passed through the polarizing filters (2_-1-2_-n) and a transparent film (200), an analysis device (4) for analyzing the distortion of the transparent film (200) on the basis of the transmitted optical image captured by the image sensor (3), and a light-emission control unit (5) for causing the plurality of light sources (1_-1-1_-n) to blink by sequentially switching between light sources on which the plurality of different types of polarizing filters are arranged, wherein sequentially switching between blinking light sources (1_-1-1_-n) makes it possible to quickly switch the angle of polarization in comparison to when rotating a polarizing plate, and to quickly measure the optical axis direction and the phase difference of transmitted light produced by a distortion section by using one general-purpose image sensor (3).

Description

Distortion measurement system for transparent film

The present invention relates to a distortion measurement system for a transparent film, and is particularly suitable for use in a system for measuring the phase difference and optical axis direction of transmitted light caused by distortion of a transparent film.

Generally, a transparent film made of plastic or the like may be distorted (uneven) due to local non-uniformity. In particular, the transparent film having a large area before cutting is likely to be partially distorted. Therefore, in the process of manufacturing the transparent film, an inspection is performed as to whether or not distortion has occurred. This inspection can be performed by irradiating the transparent film with light and analyzing the transmitted light.

That is, when the transparent film is distorted, refractive index unevenness is generated in the distorted portion. For this reason, when light is passed through the distorted portion, the light comes out behind or behind the normal portion. Therefore, the presence or absence of distortion can be inspected by receiving normal light transmitted through the normal part and abnormal light transmitted through the distorted part with an image sensor and measuring the time difference (phase difference). Further, by using polarized light of a plurality of angles as light passing through the transparent film, it is possible to detect the optical axis direction of polarized light that causes a phase difference, that is, the direction of distortion.

In a conventional strain measurement system, a phase difference is measured by rotating a polarizing plate installed in front of an inspection device and calculating data received by an image sensor several times (for example, Patent Document 1). reference). In the system described in Patent Document 1, light is emitted from a light source arranged on one side of the film surface of the laminated film, and a transmitted light image of the laminated film is obtained by an imaging unit arranged on the other side of the film surface. And detecting defects present in the laminated film based on the transmitted light image photographed by the imaging unit. In addition, an inspection polarizing filter is provided on the optical path between the laminated film and the imaging unit, and the inspection polarizing filter is rotated to detect defects.

However, in this type of system, since it is necessary to rotate the polarizing plate (inspection polarizing filter), the strain cannot be measured at high speed. Therefore, measurement cannot be performed when the transparent film to be measured is moving while the polarizing plate is rotating. Thereby, it is necessary to stop and measure the transparent film to be measured that has been conveyed from the previous process, and there is a problem that the inspection time becomes long.

On the other hand, a system is also provided in which three types of polarizing plates with different principal axis directions are provided, and three types of polarized light transmitted through the respective polarizing plates are received by three image sensors. According to this type of system, it is possible to measure distortion even when the transparent film to be measured is moving. However, there is a problem that the apparatus is increased in size and cost.

To solve these problems, as shown in FIG. 6, by using an image sensor (hereinafter referred to as a polarization image sensor) 102 in which a rotating polarizing plate array having various angles in a fine region is used, the polarizing plate rotates. There is provided a system that requires no operation and can measure the phase difference of transmitted light caused by a distorted portion of the transparent film 200 at a high speed with one polarization image sensor 102.

The distortion measurement system shown in FIG. 6 includes a light source 101 that illuminates from one side of the transparent film 200, a polarization image sensor 102 that images transmitted light from the light source 101 from the other side of the transparent film 200, and a polarization image sensor 102. And an analysis device 103 that performs distortion analysis based on the captured image obtained from the above.

However, in the distortion measurement system shown in FIG. 6, it is necessary to use a very specific polarization image sensor 102 in which a rotating polarizing plate array having various angles is incorporated in a minute area on a pixel, which increases the cost of the system. There was a problem of being.

JP 2007-212442 A

The present invention has been made to solve such a problem, and an object thereof is to provide an inexpensive system capable of measuring the distortion of a transparent film at high speed.

In order to solve the above-described problems, in the present invention, a plurality of light sources that illuminate from one side of the transparent film are provided, and a plurality of types of polarizing filters having different principal axis directions are alternately arranged with respect to the plurality of light sources. . The plurality of light sources are blinked by sequentially switching ones having different types of polarizing filters. At this time, the light transmitted through the polarizing filter and the transparent film is imaged by an image sensor, and the distortion of the transparent film is analyzed based on the transmitted light image obtained thereby.

According to the present invention configured as described above, since the angle of the polarized light transmitted through the transparent filter can be changed by sequentially switching the light source to be lit, the angle of the polarized light is faster than when the polarizing plate is rotated. The phase difference of transmitted light and the optical axis direction generated by the distorted portion of the transparent film can be measured at high speed with one image sensor. Further, since a general-purpose sensor can be used as the image sensor, it is not necessary to use an expensive polarization image sensor, and an increase in system cost can be suppressed.

It is a figure which shows the structural example of the distortion measurement system of the transparent film by this embodiment. It is a figure which shows an example of multiple types of polarizing filter by this embodiment. It is a figure which shows the example of a cross-section of one cell by this embodiment. It is a figure which shows the control state by the light emission control part of this embodiment. It is a figure which shows the other structural example of the distortion measurement system of the transparent film by this embodiment. It is a figure which shows the structural example of the conventional distortion measurement system.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram illustrating a configuration example of a transparent film distortion measurement system according to the present embodiment. In FIG. 1, it is assumed that a transparent film 200, which is a distortion measurement target, is conveyed at a constant speed from the front of the drawing to the back or vice versa.

As shown in FIG. 1, the distortion measurement system for a transparent film according to the present embodiment includes a plurality of light sources 1 _-1 to 1 _-n , a plurality of polarizing filters 2 _-1 to 2 _-n , an image sensor 3, and an analysis. A device 4 and a light emission control unit 5 are provided. Note that the analysis device 4 and the light emission control unit 5 are actually configured by a microcomputer including a CPU, a RAM, a ROM, and the like.

The plurality of light sources 1 _-1 to 1 _-n illuminate the transparent film 200 from one side of the transparent film 200 that is a distortion measurement target. In the present embodiment, the plurality of light sources 1 _-1 to 1 _-n are light emitting diodes (LEDs) having directivity. In addition, although LED is mentioned here as an example, as long as it is a light source which has directivity, you may use other than LED.

A plurality of types of polarizing filters 2 _-1 to 2 _-n having different principal axis directions (polarization angles) are used, and are alternately arranged with respect to the plurality of light sources 1 _-1 to 1 _-n . FIG. 2 is a diagram illustrating an example of a plurality of types of polarizing filters 2 _-1 to 2 _-n . In the example of FIG. 2, four types of polarizing filters 2 ₋₁ to 2 _−n are alternately arranged with respect to a plurality of light sources 1 ₋₁ to 1 _−n . In the present embodiment, the same type of polarizing filters are grouped into one group. Since there are four types of polarizing filters 2 _-1 to 2 _-n , there are four groups (Gr1 to Gr4).

In the present embodiment, as shown in FIG. 3, one light source 1 _-i (i = 1 to n) and one polarization filter 2 _-i constitute one cell 10, and a plurality of cells 10 are arranged. They are arranged in a straight line. FIG. 3 is a diagram illustrating an example of a cross-sectional structure of one cell 10. Although the plurality of cells 10 are linearly arranged one-dimensionally here, they may be two-dimensionally arranged in a matrix.

The image sensor 3 is arranged on the other side of the transparent film 200 and images light output from the light sources 1 _-1 to 1 _-n and transmitted through the polarizing filters 2 _-1 to 2 _-n and the transparent film 200. In the present embodiment, the image sensor 3 is a general-purpose line sensor.

The use of a line sensor as the image sensor 3 corresponds to the one-dimensional arrangement of a plurality of cells 10 in a straight line. When the plurality of cells 10 are two-dimensionally arranged in a matrix, the image sensor 3 is configured by an area sensor. Alternatively, the image sensor 3 may be configured by arranging a plurality of line sensors in a direction perpendicular to the line direction.

The analysis device 4 measures the distortion of the transparent film 200 by analyzing the phase difference and optical axis direction of the transmitted light caused by the distortion of the transparent film 200 based on the transmitted light image captured by the image sensor 3. As described above, since directional LEDs are used as the light sources 1 _-1 to 1 _-n in the present embodiment, the portion of the transmitted light image picked up by the image sensor 3 is lit at the maximum luminance value. There will be as many LEDs as there are. Therefore, the analysis device 4 analyzes the phase difference and the optical axis direction using the luminance information that is maximum in the transmitted light image captured by the image sensor 3.

The analysis of distortion by the analysis device 4 can be performed as follows, for example. That is, when the light sources 1 _-1 to 1 _-n are sequentially turned on, the analyzer 4 transmits normal light that has passed through the normal portion of the transparent film 200 and abnormal light that has passed through the distorted portion if there is distortion. The presence or absence of distortion is detected by measuring the phase difference. Further, it is possible to detect the position of distortion from the imaging position of abnormal light whose phase difference has been detected, and to detect the direction of distortion from the optical axis direction of polarized light when the phase difference is detected.

The light emission control unit 5 controls the plurality of light sources 1 ₋₁ to 1 _{−n so} that the light sources 1 ₋₁ to 1 _−n that are arranged with different types of polarizing filters 2 ₋₁ to 2 _−n are sequentially switched and blinked. Specifically, the light emission control unit 5 sets a plurality of light sources 1 ₋₁ to 1 _−n as one group of light sources 1 ₋₁ to 1 _−n arranged with the same type of polarizing filter, and the light sources 1 ₋₁ to 1 _{−n for} each group. Switch sequentially to blink.

FIG. 4 is a diagram illustrating a control state by the light emission control unit 5. That is, in the light emission control unit 5, first, as shown in FIG. 4A, the first type of polarizing filter 2- _j (j = 1 + 4k, k = 0, 1, 2, 3,...) Is arranged. The light sources 1- _j are set as the first group Gr1 and are turned on all at once. At this time, light transmitted through the transparent film 200 is imaged by the image sensor 3. The light emission control unit 5 immediately turns off the light source 1 _-j of the first group Gr1 after imaging by the image sensor 3.

Next, as shown in FIG. 4B, the light emission control unit 5 replaces the light sources 1- _{(j + 1)} in which the second type of polarization filters 2- _{(j + 1)} are arranged with each other in the second group. These are turned on simultaneously as Gr2. At this time, light transmitted through the transparent film 200 is imaged by the image sensor 3. The light emission control unit 5 immediately turns off the light source 1- _{(j + 1)} of the second group Gr2 after imaging by the image sensor 3.

Next, as shown in FIG. 4C, the light emission control unit 5 replaces the light sources 1- _{(j + 2)} in which the third type of polarizing filters 2- _{(j + 2)} are arranged with each other in the third group. These are turned on simultaneously as Gr3. At this time, light transmitted through the transparent film 200 is imaged by the image sensor 3. The light emission control unit 5 immediately turns off the light source 1- _{(j + 2)} of the third group Gr3 after imaging by the image sensor 3.

Next, as shown in FIG. 4 (d), the light emission control unit 5 converts the light sources 1- _{(j + 3)} in which the fourth type of polarizing filter 2- _{(j + 3)} is arranged into the fourth group. These are turned on simultaneously as Gr4. At this time, light transmitted through the transparent film 200 is imaged by the image sensor 3. The light emission control unit 5 immediately turns off the light source 1- _{(j + 3)} of the fourth group Gr4 after imaging by the image sensor 3.

The transmitted light image picked up by the image sensor 3 when the plurality of light sources 1 _{-j on} which the first type polarizing filter 2 _-j is arranged is turned on is opposed to the first type polarizing filter 2 _-j . The luminance value becomes maximum at the pixel located at the position where In this case, the analysis device 4 uses the luminance information of the pixel position where the value is maximized by the light transmitted through the first type of polarizing filter 2 _-j , and the phase difference and the optical axis caused by the distortion of the transparent film 200. Analyze direction.

Similarly, the transmitted light image captured by the image sensor 3 when the plurality of light sources 1- _{(j + 1) on} which the second type of polarizing filter 2- _{(j + 1)} is arranged is turned on. The luminance value becomes maximum at the pixel located at the position facing the two types of polarizing filters 2- _{(j + 1)} . In this case, the analysis device 4 uses the luminance information of the pixel position where the value is maximized by the light transmitted through the second type of polarizing filter 2- _{(j + 1)} , and the level generated by the distortion of the transparent film 200. Analyze phase difference and optical axis orientation.

The transmitted light image captured by the image sensor 3 when the plurality of light sources 1- _{(j + 2) on} which the third type polarization filter 2- _{(j + 2)} is disposed is turned on. The luminance value becomes maximum at the pixel located at a position facing the polarizing filter 2- _{(j + 2)} of the type. In this case, the analysis device 4 uses the luminance information of the pixel position where the value is maximized by the light transmitted through the third type of polarizing filter 2- _{(j + 2)} , and the level generated by the distortion of the transparent film 200. Analyze phase difference and optical axis orientation.

Furthermore, the transmitted light image captured by the image sensor 3 when the plurality of light sources 1- _{(j + 3) in} which the fourth type of polarizing filter 2- _{(j + 3)} is arranged is turned on. The luminance value becomes maximum at the pixel located at the position facing the polarizing filter 2- _{(j + 3)} . In this case, the analysis device 4 uses the luminance information at the pixel position where the value is maximized by the light transmitted through the fourth type of polarizing filter 2- _{(j + 3)} , and the level caused by the distortion of the transparent film 200. Analyze phase difference and optical axis orientation.

As described above in detail, in the present embodiment, a plurality of light sources 1 _-1 ~ 1 _-n for illuminating from one side of the transparent film 200, with respect to the plurality of light sources 1 _-1 ~ 1 _-n, respectively Plural types of polarizing filters 2 _-1 to 2 _-n having different main axis directions are alternately arranged. Then, the plurality of light sources 1 _-1 to 1 _-n are blinked so as to sequentially switch ones having different types of polarizing filters. At this time, the light transmitted through the polarizing filters 2 _-1 to 2- _n and the transparent film 200 is imaged by the image sensor 3, and the phase difference and optical axis direction of the transmitted light are analyzed based on the transmitted light image obtained thereby. The distortion of the transparent film 200 is measured.

According to the present embodiment configured as described above, the polarization angle transmitted through the transparent filter 200 can be changed by sequentially switching the light sources 1 _-1 to 1 _-n to be turned on. The polarization angle can be switched at a higher speed than in the above, and the phase difference and optical axis direction of the transmitted light generated by the distorted portion of the transparent film 200 can be measured at a high speed by one image sensor 3. Further, since a general-purpose sensor can be used as the image sensor 3, it is not necessary to use an expensive polarization image sensor, and an increase in system cost can be suppressed.

In the above-described embodiment, the example in which the analyzing apparatus 4 detects the maximum luminance information in the transmitted light image captured by the image sensor 3 and analyzes the phase difference and the optical axis direction has been described. The invention is not limited to this. For example, it is specified in advance at which pixel position the luminance value is maximized when which light source 1 _-1 to 1 _-n is turned on, and the phase difference and the luminance information obtained at the specified pixel are used. The optical axis direction may be analyzed.

In the above embodiment, an example in which directional LEDs are used as the plurality of light sources 1 _-1 to 1 _-n has been described. However, as shown in FIG. 5, non-directional light sources may be used. In this case, the polarizing filters 2 _-1 to 2 _-n only need to have one of different types, and the number of light sources 1 _-1 to 1 _{-n is} the same as the number of polarizing filters 2 _-1 to 2 _-n. That's fine. In addition, the analysis device 4 does not analyze using only the luminance information that is the maximum, but analyzes the phase difference and the optical axis direction using the luminance information of all the pixel positions.

Such a configuration has the advantage that the number of light sources 1 _-1 to 1 _-n and polarization filters 2 _-1 to 2 _-n to be used can be reduced. Further, when any light source 1 _-1 to 1 _-n emits light (that is, when light passes through any polarizing filter 2 _-1 to 2 _-n ), the transparent film 200 is spread over the entire area of the image sensor 3. This also has the merit that the distortion can be measured.

Moreover, in the said embodiment, when measuring the phase difference of the normal light which permeate | transmitted the normal part of the transparent film 200, and the abnormal light which permeate | transmitted the distortion part, it is normal when the light source which belongs to one group is turned on. Although it is not necessarily limited to measuring the phase difference between light and extraordinary light, the phase difference between normal light and extraordinary light may be measured within such limitation. In this way, since the phase difference can be measured by comparing the lights transmitted through the same type of polarizing filter, the measurement accuracy of the phase difference can be increased.

In addition, each of the above-described embodiments is merely an example of implementation in carrying out the present invention, and the technical scope of the present invention should not be construed in a limited manner. That is, the present invention can be implemented in various forms without departing from the gist or the main features thereof.

1 _-1 to 1 _-n light source 2 _-1 to 2 _-n polarizing filter 3 image sensor 4 analyzer 5 light emission controller

Claims

A plurality of light sources that illuminate from one side of the transparent film;
A plurality of types of polarizing filters that are alternately arranged with respect to the plurality of light sources and have different principal axis directions;
An image sensor that is disposed on the other side of the transparent film and that captures light output from the light source and transmitted through the polarizing filter and the transparent film;
Based on the transmitted light image picked up by the image sensor, an analyzer for analyzing the phase difference and optical axis direction of the transmitted light caused by the distortion of the transparent film;
A transparent film distortion measurement system comprising: a light emission control unit that controls the plurality of light sources so that a plurality of light sources having different types of polarizing filters are sequentially switched and blinked.
The light source is a directional light emitting diode,
The light emission control unit blinks the plurality of light sources by sequentially switching the light sources for each group, with the same type of polarizing filters arranged as one group.
2. The transparent film according to claim 1, wherein the analysis device analyzes the phase difference and the optical axis direction using luminance information that is maximum in a transmitted light image captured by the image sensor. Strain measurement system.
The analysis apparatus measures a phase difference between normal light transmitted through a normal portion of the transparent film and abnormal light transmitted through a distorted portion when light sources belonging to one group are turned on. Item 3. The distortion measurement system for a transparent film according to Item 2.
The light source is omnidirectional illumination,
The distortion of the transparent film according to claim 1, wherein the analysis device analyzes the phase difference and the optical axis direction using luminance information of the entire region of the transmitted light image captured by the image sensor. Measuring system.