JP5922520B2 - Straightness measuring device and straightness measuring method - Google Patents

Description

  The present invention relates to a straightness measuring device and a straightness measuring method. In particular, it is effective for evaluating the straightness of a linear pattern existing on the subject.

  In recent years, materials having a linear pattern that requires a straightness of about 1 μm per meter are used in various products. For example, a pattern film used for a three-dimensional (3D) display whose market has been expanded in recent years is known. In order to guarantee the quality of a material having such a straight line pattern with excellent straightness, it is necessary to inspect the deviation of the straight line pattern from the original straight line pattern.

  The patterned retardation material is manufactured so as to alternately arrange lines having different retardation characteristics. Various manufacturing methods have been proposed (US Pat. No. 5,327,285, JP 2001-059949 A, JP 10-161108 A, JP 10-160933 A, and JP 10 10 A. No. 153707). For example, in the method of exposing a specific area, the edge part of the pattern exposure light is made as sharp as possible, but the light energy continuously changes in the minute area of the edge, so that sufficient alignment control cannot be performed. There are several μm to several tens of μm. That is, there is a minute region that does not have either phase difference characteristic at the boundary of each pattern. Patterned phase difference materials require quality in the state of being bonded to the display panel depending on the application, so the minute boundary area must overlap the display cell display cell boundary (black matrix) line accurately. There is. Therefore, the straightness of the boundary area must be strictly managed for the patterned retardation material used for the display panel.

  Therefore, it is necessary to accurately measure the deviation of the linear pattern from the original linear pattern in the patterned retardation material to determine whether or not the quality can be ensured in a state where the patterned retardation material is bonded to the display panel. When it is determined that it cannot be used, this part is specified, and this part is not used, and a 3D liquid crystal display or the like is manufactured.

  At present, a technique that has been proposed to evaluate a deviation from an original linear pattern with a scale of about 1 μm per meter for a linear pattern of such a patterned retardation material has been proposed. Absent. In addition, as a technique for evaluating the straightness with high accuracy on the surface of a rigid object, for example, there is a straightness measuring device as in Patent Document 1. In Patent Document 1, two measurement results are obtained when a pattern body having a linear pattern is fixed at each of two positions, and the amount of change between the two positions is measured by taking the difference between them. An apparatus and method for measuring straightness by doing so are described.

  In Patent Document 2, an image signal is acquired while a reading unit that reads line by line is relatively moved with respect to the subject, and information related to the end position of the line pattern and information related to the width of the line pattern are calculated. A print evaluation apparatus is described in which the distance between the center position of a line pattern obtained from both pieces of information and the approximate straight line of the line pattern is calculated, and the linearity is evaluated based on the calculation result.

  In Patent Document 3, in a long X-ray diagnostic apparatus for a human body, a plurality of images are taken by shifting the X-ray detector to different positions while having an overlapping portion with respect to a subject, and the images are superimposed. An apparatus for creating a long image by correcting a pixel position after setting a joining position is described.

JP 2010-019742 A Japanese Patent Laid-Open No. 04-227578 JP 2011-2335010 A

  In the technique of Patent Document 1, it is possible to evaluate the straightness for the surface of a rigid body with high accuracy. However, for a straight line pattern of a patterned retardation material, the straight line The deviation of the pattern from the original linear pattern cannot be measured. Moreover, even if a linear pattern of the patterned retardation material can be imaged over a wide area by combining a polarizing plate or the like, the deviation cannot be evaluated on a scale of about 1 μm per meter.

  Further, with the technology of Patent Document 2, there is no problem with the accuracy and the evaluation target area for evaluating the image quality of the image output device, but it is not possible to obtain an evaluation accuracy higher than the position error of the moving device. In particular, when the subject is long, the movement distance becomes long and accuracy deterioration cannot be avoided, and the straightness cannot be evaluated on a scale of about 1 μm per meter.

  Further, in the technique of Patent Document 3, since the original subject is a human body and does not have a predetermined pattern, it is different from an image composed of a linear pattern. For an image configured with a linear pattern, the technique for setting the joint position of the image described in Patent Document 3 is insufficient. In addition, the image is divided into small areas, the coordinates are converted so that the correlation value of both images is the highest in the small area, and the pixel position is corrected in the overlapping area. Therefore, a long time is required for image composition, or an expensive high-speed processing apparatus is required.

  The present invention provides an inexpensive straightness measuring apparatus and straightness measuring method capable of evaluating a deviation from an original linear pattern on a scale of about 1 μm per meter for a linear pattern of a patterned retardation material. The purpose is to provide.

In order to achieve the above object, the straightness measuring apparatus of the present invention has a film-like or sheet-like shape in which a plurality of stripe-shaped first and second phase difference regions having different phase difference characteristics are alternately arranged. A straightness measuring device that measures the straightness of a linear pattern arranged at a predetermined interval on a subject that is a patterned phase difference material having an imaging range so that the imaging range has an overlapping region in the direction of the linear pattern An imaging device that captures a plurality of images of a subject and a plurality of images that are connected in an in-plane direction perpendicular to the direction of the straight line pattern so that overlapping regions are accurately overlapped and overlapped an image processing unit for measuring the straightness of the straight line pattern in the image, the light from the light emitting surface and the illumination device for irradiating the one surface of the subject, and the vicinity of the light emitting surface of the illumination apparatus, imaging The first and second transmission axes are provided in the vicinity of the imaging surface of the device so as to be substantially parallel to the light emitting surface or the imaging surface, respectively, so that the luminance in the phase difference region and the luminance in the boundary region of the image can be distinguished. And a first polarizing plate and a second polarizing plate .

  The shift is preferably within a range corresponding to a predetermined interval. Further, the imaging device is a plurality of area sensor cameras that are provided adjacent to each other and capture a plurality of images substantially simultaneously, or a plurality of images while moving relative to the subject in the direction of a linear pattern. It is desirable to image.

In order to achieve the above object, the straightness measurement method of the present invention has a film-like or sheet-like shape in which a plurality of stripe-like first and second retardation regions having different phase difference characteristics are alternately arranged. A straightness measurement method for measuring the straightness of a linear pattern arranged at a predetermined interval on a subject that is a patterned phase difference material having an imaging range so that the imaging range has an overlapping region in the direction of the linear pattern A plurality of images of a subject are captured, and the plurality of images are connected in an in-plane direction perpendicular to the direction of the straight line pattern so that overlapping regions are accurately overlapped. measuring the straightness of the linear pattern, is irradiated with light from the light emitting surface of the illumination device toward the one surface of the subject, and the vicinity of the light emitting surface of the illumination device, the imaging of the imaging device for imaging a plurality of images First and second polarizing plates are provided in the vicinity so as to be substantially parallel to the light emitting surface or the imaging surface, respectively, so that the luminance in the phase difference region and the luminance in the boundary region of the image can be distinguished from each other. The first and second transmission axes of each plate are set .

  The shift is preferably within a range corresponding to a predetermined interval. In addition, a plurality of images are captured by a plurality of area sensor cameras provided adjacent to each other, or a plurality of images are captured while moving relative to the subject in the direction of the linear pattern. It is desirable to image.

  The present invention measures the straightness of a linear pattern of a subject using a plurality of images obtained by imaging the same subject with high accuracy, and the plurality of images are connected by an accurate method. The straightness of a long-distance linear pattern can be measured with a scale based on imaging accuracy. In addition, even if meandering occurs during continuous conveyance of a web-like object or when moving the imaging device, straight lines of long distances are straight on a scale based on imaging accuracy without being affected by the meandering. The degree can be measured.

It is a perspective view of the straightness measuring device concerning a 1st embodiment of the present invention. It is sectional drawing in (II) of FIG. It is the figure which showed the patterned phase difference material used as the test object of the straightness measuring apparatus which concerns on this invention. It is sectional drawing in (IV) of FIG. 3, and explanatory drawing regarding the polarization axis of patterned phase difference material. It is the figure which showed the example of the image obtained by imaging the patterned phase difference material used as the test object of the straightness measuring apparatus which concerns on this invention. It is explanatory drawing regarding the image process part in the straightness measuring device which concerns on this invention. It is explanatory drawing about the imaging region in the case of imaging a patterned phase difference material with the straightness measuring apparatus which concerns on this invention. It is explanatory drawing regarding each captured image when a patterned phase difference material is imaged with the straightness measuring device according to the present invention. It is the outline of the flowchart at the time of measuring using the straightness measuring device concerning the present invention. FIG. 10 is a detailed flowchart related to overlapping area processing in the flowchart of FIG. 9. FIG. It is explanatory drawing about the similarity calculation process in an overlap area | region process. It is explanatory drawing about the similarity calculation process in an overlap area | region process. It is explanatory drawing about an image connection process. FIG. 10 is a detailed flowchart regarding an approximate line determination process in the flowchart of FIG. 9. FIG. It is a perspective view of the straightness measuring device concerning a 2nd embodiment of the present invention. It is sectional drawing in (XVI) of FIG. It is a perspective view of the straightness measuring apparatus which concerns on the 3rd Embodiment of this invention. It is sectional drawing in (XVIII) of FIG.

  As shown in FIGS. 1 and 2, the straightness measuring apparatus 2 according to the first embodiment of the present invention includes a plurality of stripe-shaped first and second phase difference regions alternately arranged with different phase difference characteristics. It is a straightness measuring apparatus that accurately measures the straightness of a linear pattern of a subject 3 that is a patterned retardation material having an arrayed film shape or sheet shape. In the present embodiment, the patterned retardation material is selected for the subject 3. However, the present invention is not limited to this, and any material having a linear pattern may be used.

  Further, the straightness measuring device 2 is provided with an illuminating device 4 that irradiates the subject 3 with light, and is provided substantially in parallel to the subject 3 on the opposite side of the illuminating device 4 with respect to the subject 3. And an area sensor camera 6 that detects light irradiated from the light source and converts it into a photoelectric signal to form an image. A plurality of area sensor cameras 6 are provided in the direction of the linear pattern of the subject, and the two imaging fields of view in the area sensor cameras 6 provided adjacent to each other are overlapping regions 3-1, 3-2, 3-3, 3 respectively. -4. In this embodiment, an example in which five area sensor cameras 6 are provided is shown, but the present invention is not limited to this, and two or more area sensor cameras may be provided. Further, the straightness measuring apparatus 2 may have a moving mechanism that relatively moves the subject 3 and the imaging field of view of the area sensor camera 6.

  Further, the straightness measuring device 2 is provided between the subject 3 and the illumination device 4 so as to be rotatable substantially parallel to the subject 3, and includes a first polarizing plate 7 having a first transmission axis, the subject 3, and the like. A second polarizing plate 8 provided with a second transmission axis is provided between the area sensor camera 6 and the subject sensor 3 so as to be rotatable in parallel with the subject 3. It is desirable that the first polarizing plate 7 and the second polarizing plate 8 are provided so as to cover the entire imaging visual field of the plurality of area sensor cameras 6. Further, the straightness measuring apparatus 2 includes a first rotation control unit (not shown) that rotates the first polarizing plate 7 to control the direction of the first transmission axis, and a second transmission axis that rotates the second polarizing plate 8. And a second rotation control unit (not shown) for controlling the direction of the rotation.

  Further, the straightness measuring apparatus 2 is imaged by the camera control unit 11 that controls the plurality of area sensor cameras 6 to image the subject 3 in the imaging field of view substantially simultaneously and the plurality of area sensor cameras 6. And an image processing unit 12 that processes a plurality of images.

  As shown in FIG. 2, the illumination device 4 includes a plurality of LEDs 4A and a diffusion plate 4B arranged in a plane. For this reason, the illuminating device 4 can radiate | emit uniform light in a surface from a light emission surface.

  Each area sensor camera 6 includes an optical system 6A, an aperture 6B, and an area sensor 6C. Since the area sensor camera 6 must have a certain overlapping area with the adjacent area sensor camera 6, it is desirable that the imaging field of view has a certain spread. Since this spread determines the straightness measurement region, the larger the spread of the imaging field of view, the better from the viewpoint of the straightness measurement region. Further, since this spread determines the number of area sensor cameras 6 installed per unit measurement distance, it is desirable that the spread of the imaging field of view is larger from the viewpoint of cost. On the other hand, since the accuracy of the area sensor camera 6 determines the measurement accuracy of the straightness, it is preferable that the accuracy of the area sensor camera 6 is higher from the viewpoint of the accuracy of the straightness. Since these two elements are contradictory, the specifications of the area sensor camera 6 and the number thereof are determined according to the specifications of the required measurement area, cost, and accuracy.

  As shown in FIG. 3 and FIG. 4 (A), the patterned retardation material selected as the subject 3 includes a stripe-shaped first retardation region 3B and a second retardation region 3C on the substrate 3A. Are alternately arranged and arranged. Hereinafter, the present invention will be described assuming that the subject 3 is a web-like film, that is, the subject 3 is a patterned phase difference film. However, the subject 3 is not a web-like film, a plastic plate, a glass plate, or the like. It can be anything else. In this case, the moving mechanism may move the subject or may move the plurality of area sensor cameras 6 simultaneously. When the subject 3 is a web-like film, the moving mechanism moves, for example, a web-like film supply roller, its take-up roller, and its transport roller 10 so that the subject 3 moves stably in one direction. Have.

  In the present specification, the definition of the direction of the transmission axis and the slow axis of the polarizing plate is the direction in which the direction is rotated clockwise with respect to the straight line 3D in the pattern boundary direction when viewed from the light receiving side. It will be defined depending on For example, as shown in FIG. 4B, the transmission axis As1 is regarded as the direction of + θ. Further, with respect to the slow axis As2, it is regarded as the direction of -θ.

  The subject 3 to be used for the use of the straightness measuring apparatus 2 according to the present invention includes, for example, a slow phase in the second phase difference region having a slow axis of + 45 ° in the first phase difference region which is an example of a patterned phase difference material. Examples thereof include a web-like film having an axis of −45 ° (a type 1 patterned retardation film having a slow axis of ± 45 °). In this case, the first transmission axis of the first polarizing plate 7 is set to + 45 ° and the second transmission axis of the second polarizing plate 8 is set to −45 °, or the first transmission axis of the first polarizing plate 7 is set. Is set to −45 ° and the second transmission axis of the second polarizing plate 8 is set to + 45 °.

  A case where the first transmission axis is set to + 45 ° and the second transmission axis is set to −45 ° will be described. The light emitted from the illumination device 4 becomes + 45 ° linearly polarized light after passing through the first polarizing plate 7. Even when the + 45 ° linearly polarized light passes through the first phase difference region having the slow axis of + 45 °, the entire waveform is only delayed by the phase of 90 degrees, and thus remains as + 45 ° linearly polarized light. In addition, + 45 ° linearly polarized light remains + 45 ° linearly polarized light because it does not affect the entire waveform even if it passes through the second phase difference region whose slow axis is −45 °. Does not change. That is, + 45 ° linearly polarized light is + 45 ° linearly polarized light, regardless of whether it is incident on or passes through the first or second retardation region of the patterned retardation material having a slow axis of ± 45 °. It is injected as it is. However, this + 45 ° linearly polarized light cannot pass through the second polarizing plate 8 having the second transmission axis of −45 °. Therefore, the area sensor camera 6 captures an image with both the first and second phase difference regions being in the extinction state. The same applies to the case where the first transmission axis is set to −45 ° and the second transmission axis is set to + 45 °.

  On the other hand, the boundary region between the first and second phase difference regions cannot control the phase difference (even though it has optical characteristics as a λ / 4 wavelength plate having a slow axis of ± 45 °) Therefore, the irradiation light can pass through the system of the first and second polarizing plates 7 and 8 arranged so as to sandwich the boundary region. As a result, the area sensor camera 6 images the boundary area between the first and second phase difference areas as a light transmission state. The same applies to the case where the first transmission axis is set to −45 ° and the second transmission axis is set to + 45 °.

  In this way, a system in which the subject 3 as the patterned retardation material is sandwiched between the first and second polarizing plates 7 and 8 is created, and the subject 3 is viewed with the intensity of the transmitted light. In such a case, an image as shown in FIG. 5 is seen. Since both the first phase difference region 3B and the second phase difference region 3C are imaged in the extinction state, a dark portion 3E is formed, and the boundary region between the first and second phase difference regions is imaged as a light transmission state. Therefore, the light part 3F is comprised. It should be noted that not only the patterned retardation material of the example described here but also other patterned retardation materials are similarly imaged in the extinction state in the two retardation regions, and the boundary region of It is known that imaging can be performed in a transmissive state. Further, the difference in luminance between the dark portion 3E and the light portion 3F is sufficient if the luminance between the dark portion 3E and the light portion 3F can be identified, but of course, the larger the difference, the better. Further, the present invention can be used to measure straightness not only for grayscale images but also for images having colors such as RGB.

  As illustrated in FIG. 6, the image processing unit 12 includes an overlapping region processing unit 14 that calculates a correction shift amount for accurately overlapping the linear patterns in an overlapping region of images captured by the area sensor camera 6. An image connection processing unit 15 that overlaps overlapping regions and connects adjacent images based on the calculation result of the correction shift amount, and a linear pattern determination processing unit 16 that determines a straight line pattern whose straightness should be measured in the connected images. The approximate line determination processing unit 17 that analyzes and determines each approximate line by analyzing the pixel data constituting the straight line related to each determined straight line pattern, and uses each determined approximate line And a straightness calculation unit 18 that calculates straightness of the straight line pattern. The image processing unit 12 preferably includes a linearity calculation unit 19 that calculates the linearity of the linear pattern.

  The approximate straight line determination processing unit 17 uses a pixel data to set a reference straight line setting processing unit 21 that sets a reference straight line by the least square method, and a displacement straight line setting process that sets a straight line displaced by a small amount from the reference straight line. Unit 22, a distance calculation unit 23 that calculates the distance between a reference straight line or a straight line displaced by a small amount and each pixel data, and a maximum distance that extracts a maximum value among the distances calculated for each line An extraction unit 24 and a reference straight line reset processing unit 25 that selects a straight line having the minimum distance among the straight lines and resets the straight line as a reference straight line.

  Next, the operation of the straightness measuring apparatus 2 according to the first embodiment of the present invention will be described. First, a system in which a subject 3 that is a patterned phase difference material emitted from the illumination device 4 is sandwiched between first and second polarizing plates 7 and 8 by five area sensor cameras 6 controlled by the camera control unit 11. Based on the light that has passed, five images are captured.

  For example, as shown in FIG. 7, the imaging areas 26A and 27A, the imaging areas 27A and 28A, the imaging areas 28A and 29A, and the imaging areas 29A and 30A are respectively overlapped areas 3-1, 3-2, 3-3. 3-4, the imaging regions 26A, 27A, 28A, 29A, and 30A in the subject 3 are imaged. As a result of the imaging, images 26B, 27B, 28B, 29B, and 30B as shown in FIG. 8 are obtained from the imaging areas 26A, 27A, 28A, 29A, and 30A, respectively.

  A method for processing the images 26B, 27B, 28B, 29B, and 30B will be described with reference to the flowchart shown in FIG. The flowchart shown in FIG. 9 includes an overlapping area process S1, an image connection process S2, a straight line pattern determination process S3, an approximate straight line determination process S4, and a straightness calculation process S5.

  The overlapping area process S1 is a process for calculating the correction shift amount of the image in the in-plane direction perpendicular to the linear pattern direction so that the linear patterns in the overlapping area accurately overlap each other, and the image connection process S2 is a correction process. This is a process of shifting one image with respect to the other image based on the shift amount calculation result, overlapping overlapping regions, and connecting adjacent images. The overlapping region processing S1 is performed by the overlapping region processing unit 14, and the image connection processing S2 is performed by the image connection processing unit 15.

  The straight line pattern determining process S3 is a process for determining a straight line pattern whose straightness is to be measured in the connected images, and the approximate straight line determining process S4 is a process for determining pixel data constituting straight lines related to the determined straight line patterns. The straightness calculation process S5 is a process for calculating the straightness of each straight line pattern using the determined approximate straight lines. The straight line pattern determination processing S3 is performed by the straight line pattern determination processing unit 16, the approximate straight line determination processing S4 is performed by the approximate straight line determination processing unit 17, and the straightness calculation processing S5 is performed by the straightness calculation unit 18.

  As shown in FIG. 10, the overlapping area process S1 includes an overlapping area calculation process S1-1 and a correction shift amount calculation process S1-2. By previously measuring an overlapping area between two adjacent area sensor cameras 6 and inputting the area to the overlapping area processing unit 14, the overlapping area calculation process S1-1 can be performed very smoothly. it can. For example, in the image 27B and the image 28B, if the overlap region 3-2 is measured in advance and input to the overlap region processing unit 14, the region corresponding to this region is very smoothly overlapped in the image 27B and the image 28B. Can be calculated. Other images can be processed similarly.

  As for the correction shift amount calculation process S1-2, an example between the image 27B and the image 28B will be described here. As shown in FIG. 8, in the image 27B, locations corresponding to the light portion 3F indicating the boundary region between the first and second phase difference regions are light portions 27-1, 27-2, 27-3, 27-. There are 4 locations. Further, in the image 28B, there are four locations corresponding to the light portion 3F indicating the boundary region between the first and second phase difference regions, light portions 28-1, 28-2, 28-3, and 28-4. To do.

  Of the light portions 27-1, 27-2, 27-3, 27-4 in the image 27, only the portions in the overlapping region 3-2 are regarded as the respective figures, and the light portions 28-1, Of the sections 28-2, 28-3, and 28-4, only the portions in the overlapping area 3-2 are regarded as the respective figures. And the relative position between the light parts 27-1, 27-2, 27-3, 27-4, the relative position between the light parts 28-1, 28-2, 28-3, 28-4, The figure shape similarity between the light portions 27-1, 27-2, 27-3, 27-4 and the light portions 28-1, 28-2, 28-3, 28-4 is calculated.

  The calculation results of the relative position and the similarity are shown in FIGS. 11 and 12, respectively. From these figures, in the overlapping region 3-2, the light part 27-1 and the light part 28-2, the light part 27-2 and the light part 28-3, the light part 27-3 and the light part 28-4, It can be seen that has a very strong similarity. From this result, it is necessary to correct the positional deviation on the image relative to the image position when the overlapping region is overlapped with the combination having the highest similarity and the initial image position before the overlapping, that is, on the image. The shift amount can be determined. A similar process is performed as the correction shift amount calculation process S1-2 for other adjacent images.

  In the image connection process S2, all adjacent images are connected based on the calculation result of the correction shift amount between all adjacent images. As a result, a connected image as shown in FIG. 13 is obtained.

  In place of the overlapping region processing S1 and the image linking processing S2, the captured images are overlapped by the overlapping region between the two adjacent area sensor cameras 6, and the images are within the subject plane perpendicular to the direction of the linear pattern. A similar connected image can be obtained by shifting in the direction.

  When performing these image connections, it is desirable that the correction shift amount is processed within a range corresponding to one pitch of the linear pattern of the subject at the maximum. This is because the installation position accuracy of the area sensor camera can be easily adjusted in advance within an error of one pitch of the subject, and therefore a predictable image shift is expected to be one pitch or less. In addition, since it is easy to set the angle difference between the cameras in advance by matching the angles on the images of the cameras, it is practically sufficient to correct only the direction perpendicular to the linear pattern direction as the correction shift. is there. By doing so, the calculation amount of correction shift amount can be greatly reduced, and high-speed and inexpensive evaluation becomes possible.

  Next, a linear pattern determination process S3 is performed on the connected image as shown in FIG. First, the light portions 33, 34, and 35 that are connected without interruption from the image 26B at one end to the image 30B at the other end are selected. The light portions 33, 34, and 35 are determined as straight patterns whose straightness should be calculated. In addition, the straight lines 33A, 33B, 34A, 34B, 35A, and 35B on both sides of the light portions 33, 34, and 35 are determined as straight lines related to the straight line pattern whose straightness should be calculated.

  Next, approximate line determination processing S4 is performed for each of the straight lines 33A, 33B, 34A, 34B, 35A, and 35B determined as straight lines related to the straight line pattern whose straightness is to be calculated. As shown in FIG. 14, the approximate straight line determination process S4 includes a reference straight line setting process S4-1, a reference straight line distance calculation process S4-2, a displacement straight line setting process S4-3, and a displacement straight line distance calculation process S4-4. And an optimal straight line selection process S4-5 and a reference straight line resetting process S4-6.

  The reference straight line setting process S4-1 is a process of setting a reference straight line F (1) by the least square method using pixel data constituting a straight line related to the determined one straight line pattern. In this embodiment, the reference straight line setting process S4-1 is performed using the least square method, but the present invention is not limited to this. The reference straight line F (1) is set by the reference straight line setting process S4-1 as shown in the following (formula 1). In addition, a and b in (Formula 1) are calculated | required by the formula shown to (Formula 2) and (Formula 3), respectively.

Next, a reference straight line distance calculation process S4-2 is performed. First, the distance between the reference straight line F (1) in the straight line and each pixel data (x _i , y _i ) constituting the straight line is calculated. This distance d _i is performed using (Equation 4) shown below. This process is performed by the distance calculation unit 23.

Next, the maximum value D (1) is extracted from the distance d _i (1) calculated by (Equation 4). This operation is performed using (Equation 5) shown below. This process is performed by the maximum distance extraction unit 24.

  Next, a displacement straight line setting process S4-3 is performed. For a and b, a small transformation shown in the following (Expression 6-1) and (Expression 6-2) is performed on a certain limited region. The straight lines based on (Equation 1) to which the micro-transformation is applied by performing the micro-transformation of (Equation 6-1) and (Equation 6-2) are respectively F (2), F (3),.・ ・ Place it. This process is performed by the displacement straight line setting processing unit 22.

Next, a displacement linear distance calculation process S4-4 is performed. These are the same processes performed for F (1) using (Equation 4) and (Equation 5) for F (2), F (3),. It is. Thereby, the distance d _i (2), the distance d _i (3),..., The maximum value D (2), the maximum value D (3),.

  Next, optimal straight line selection processing S4-5 is performed. In this process, the smallest one of D (1), D (2), D (3),... Is selected, and the corresponding straight line and its parameters are selected as the optimum straight line.

  Next, a reference straight line resetting process S4-6 is performed. The reference straight line reset processing S4-6 is performed by the reference straight line reset processing unit 25. In the case where D (X) other than D (1) is selected in the optimal straight line selection process S4-5 (X is an integer of 2 or more), the straight line F corresponding to the selected D (X). (X) is replaced with a straight line F (1). Then, based on the newly replaced straight line F (1), the process of the reference straight line distance calculation process S4-2 to the optimal straight line selection process S4-5 is performed again. On the other hand, when the item selected in the optimum straight line selection process S4-5 is D (1), the straight line F (1) corresponding thereto is determined as the approximate straight line. In this way, the processes of the reference straight line distance calculation process S4-2 to the reference straight line resetting process S4-6 are repeated until an optimum approximate straight line is found.

  Finally, straightness calculation processing S5 is performed. Since the straightness is the value of D (1) when the approximate straight line determination processing S4 is finished, this value is displayed and the processing related to the series of straightness measuring devices 2 is finished. The process for calculating the straightness of the straight line by the approximate straight line determination process S4 and the straightness calculation process S5 is merely an example in the present embodiment, and instead of other known straightness calculation processes. A method can also be used.

  When the image processing unit 12 includes the linearity calculation unit 19, the straightness measurement device 2 performs straightness calculation in addition to straightness calculation or instead of straightness calculation. be able to. The straightness here is an index value indicating how much the relative position data is deviated from the true straight line, and the value is relative to the straight line (Equation 7) calculated by the least square method, for example. It is given by the mean square L of the distance to the position data coordinates, and is expressed by (Equation 10). Note that p and q according to (Expression 7) are expressed by (Expression 8) and (Expression 9), respectively.

  Next, a straightness measuring device 37 according to the second embodiment of the present invention will be described. As shown in FIGS. 15 and 16, the straightness measuring device 38 includes a backup roll 38 that supports the subject 3 and a plurality of area sensor cameras 6 that image the subject 3 around the backup roll 38. A plurality of area sensor cameras 6 are provided in the direction of the linear pattern of the subject, and are arranged so that their imaging surfaces are approximately within a cylindrical curved surface coaxial with the backup roll 38.

  Further, the two imaging fields of view in the area sensor camera 6 provided adjacent to each other include overlapping regions 3-5 and 3-6, respectively. In this embodiment, an example in which three area sensor cameras 6 are provided is shown, but the present invention is not limited to this, and two or more area sensor cameras may be provided. Further, the straightness measuring device 37 may have a moving mechanism that relatively moves the subject 3 and the imaging field of view of the area sensor camera 6, for example, a rotational drive mechanism using a backup roll.

  Note that image capturing and image processing are performed in the same manner as in the first embodiment, and thus detailed description thereof is omitted. Further, the effect obtained thereby is the same as that of the first embodiment.

  Next, a straightness measuring apparatus 40 according to the third embodiment of the present invention will be described. As shown in FIGS. 17 and 18, the straightness measuring device 40 includes one area sensor camera 6 instead of a plurality of area sensor cameras, and includes a camera support member 41 and a camera moving mechanism 42. Yes. Components similar to those of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. In the third embodiment, a plurality of cameras may be provided.

  The camera moving mechanism 42 is provided at both ends of the camera support member 41, and the area sensor camera 6 enables the subject 3 to move in the direction of the linear pattern. While moving the area sensor camera using the camera moving mechanism 42, the imaging field of view is selected so as to include the overlapping areas 3-1, 3-2, 3-3, and 3-4, respectively (see FIG. 18), images similar to the images 26B, 27B, 28B, 29B, and 30B described in the first embodiment can be obtained.

  Also in the third embodiment, the same image processing as in the first embodiment can be performed. As in the first embodiment, correction is performed only in the in-plane direction perpendicular to the linear pattern direction. However, the error in the position of the camera moving mechanism 42 is dominated by the error in the camera position. Since the error is sufficiently small, it is practically sufficient to correct only the above-mentioned direction as a correction shift. By doing so, as in the first embodiment, the calculation amount of the correction shift amount can be greatly reduced, and high-speed and inexpensive evaluation can be performed.

  As described above, the straightness measuring apparatus according to the present invention can evaluate the deviation from the original linear pattern on the scale of about 1 μm per 1 m for the linear pattern of the patterned phase difference material. . In addition, straightness can be evaluated on a similar scale. The present invention can easily measure the straightness in a process without cutting the strip-shaped patterned retardation material for the measurement of the straightness. Note that the present invention can be used with any material that has a linear pattern that can be imaged. In addition, any straightness measuring device and straightness measuring method performed by a combination of technical ideas described in this specification are considered to be within the scope of the present invention.

2, 37, 40 Straightness measuring device 3 Subject 3-1, 3-2, 3-3, 3-4, 3-5, 3-6 Overlapping region 4 Illuminating device 6 Area sensor camera 7 First polarizing plate 8 Second polarizing plate 11 Camera control unit 12 Image processing unit 14 Overlapping region processing unit 15 Image connection processing unit 16 Linear pattern determination processing unit 17 Approximate straight line determination processing unit 18 Straightness calculation unit 19 Linearity calculation unit 21 Reference straight line setting processing unit 22 Displacement straight line setting processing unit 23 Distance calculation unit 24 Maximum distance extraction unit 25 Reference straight line resetting processing unit 26A, 27A, 28A, 29A, 30A Imaging regions 26B, 27B, 28B, 29B, 30B Images 27-1, 27-2 , 27-3, 27-4, 28-1, 28-2, 28-3, 28-4, 33, 34, 35 Light part 33A, 33B, 34A, 34B, 35A, 35B Straight line 38 bar Cockup roll 41 Camera support member 42 Camera moving mechanism S1 Overlapping area processing S1-1 Overlapping area calculation processing S1-2 Correction shift amount calculation processing S2 Image connection processing S3 Straight line pattern determination processing S4 Approximate straight line determination processing S4-1 Reference straight line setting processing S4 -2 Reference straight line distance calculation process S4-3 Displacement straight line setting process S4-4 Displacement straight line distance calculation process S4-5 Optimal straight line selection process S4-6 Reference straight line resetting process S5 Straightness calculation process

Claims (8)

At predetermined intervals on a subject, which is a patterned retardation material having a film-like or sheet-like shape in which a plurality of stripe-like first and second retardation regions having different retardation characteristics are alternately arranged. A straightness measuring device that measures the straightness of arranged linear patterns,
An imaging device that captures a plurality of images of the subject such that an imaging range has an overlapping region in the direction of the linear pattern;
The plurality of images are connected so that the overlapping regions are accurately overlapped by shifting in an in-plane direction perpendicular to the direction of the linear pattern, and the straightness of the linear pattern in the overlapped image is determined. An image processing unit to be measured;
An illumination device that irradiates light from the light emitting surface toward one surface of the subject;
Provided in the vicinity of the light emitting surface of the illuminating device and in the vicinity of the imaging surface of the imaging device, respectively, substantially in parallel with the light emitting surface or the imaging surface, and the luminance in at least one phase difference region and the luminance in the boundary region of the image. First and second polarizing plates having respective first and second transmission axes so that they can be identified;
A straightness measuring apparatus comprising:     2. The straightness measuring apparatus according to claim 1, wherein the shift is within a range corresponding to the predetermined interval.   The straightness measurement device according to claim 1, wherein the imaging device is a plurality of area sensor cameras that are provided adjacent to each other and that capture the plurality of images substantially simultaneously.   The straightness measurement device according to claim 1, wherein the imaging device captures the plurality of images while moving the image relative to the subject in a direction of the linear pattern. At predetermined intervals on a subject, which is a patterned retardation material having a film-like or sheet-like shape in which a plurality of stripe-like first and second retardation regions having different retardation characteristics are alternately arranged. A straightness measurement method for measuring the straightness of arranged linear patterns,
Taking a plurality of images for the subject so that the imaging range has an overlapping region in the direction of the linear pattern,
The plurality of images are connected so that the overlapping regions are accurately overlapped by shifting in an in-plane direction perpendicular to the direction of the linear pattern, and the straightness of the linear pattern in the overlapped image is determined. Measure and
Irradiate light from the light emitting surface of the illumination device toward one surface of the subject,
First and second polarizing plates are provided in the vicinity of the light emitting surface of the illumination device and in the vicinity of the imaging surface of the imaging device that captures the plurality of images, substantially parallel to the light emitting surface or the imaging surface, respectively.
Straightness measurement , wherein the first and second transmission axes of the first and second polarizing plates are set so that the luminance in at least one phase difference region of the image and the luminance in the boundary region can be distinguished. Method. 6. The straightness measurement method according to claim 5, wherein the shift is within a range corresponding to the predetermined interval. The straightness measurement method according to claim 5 or 6 , wherein the plurality of images are picked up by picking up images substantially simultaneously by a plurality of adjacent area sensor cameras. The straightness measurement method according to claim 5 or 6, wherein the plurality of images are captured while being moved relative to the subject in the direction of the linear pattern.

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