JP2014119255A - Device for inspecting optical film and method for inspecting optical film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and device for inspecting an optical film, which is capable of surely detecting a defect of a single optical film.SOLUTION: The device for inspecting an optical film includes: a light source which emits light; an imaging unit including at least one camera which images light from the light source; two light-transmissive plate members which are arranged between the light source and the imaging unit so as to hold an optical film being an inspection object therebetween and transmit the light from the light source; and a driving mechanism which changes a relative positional relation between the imaging unit and two light-transmissive plate members in a direction parallel with surfaces of the two light-transmissive plate members. The imaging unit captures two kinds of images of a rough image captured via a lens having a depth of field equal to or more than the thickness of the optical film and a fine image captured via a lens having a depth of field equal to or more than half the thickness of the optical film.

Description

  The present invention relates to an optical film inspection apparatus and inspection method for inspecting defects in thin optical films such as polarizing plates used in liquid crystal panels.

  The polarizing plate, which is a component part of the liquid crystal panel, is usually supplied in a state where protective films are bonded to the front and back surfaces. Main defects in the polarizing plate alone include foreign matters, bubbles, and scratches. These exist not only in the boundary between the polarizing plate and the adhesive layer of the protective film, but also in the polarizing plate itself. In addition, the polarizing plate may have a multilayer structure, and defects may exist at the boundary between layers. If there is a defect such as a foreign substance or a bubble in the polarizing plate, when the liquid crystal is turned on, it becomes a bright spot and is treated as a lighting failure.

  Such a defect inspection is usually performed as a lighting test in the state of the liquid crystal panel with the polarizing plate attached in the manufacturing process of the liquid crystal panel. However, in order to drive the liquid crystal panel, a driver for applying an electric charge is required. When a defect is detected, it takes time and effort to remove the driver for repair. For this reason, there has been proposed a method for inspecting defects in a state where the liquid crystal panel is bonded and the liquid crystal panel is not driven (see, for example, Patent Document 1).

JP 2011-163846 A

However, the method described in Patent Document 1 for inspection with a liquid crystal panel with a polarizing plate attached has the following problems.
・ In the case of a single polarizing plate, defective products continue to be manufactured until the process of attaching the liquid crystal panel, resulting in loss.
-When a defect is detected, the troublesome work of peeling off the polarizing plate for repair occurs.
-A liquid crystal panel with polarizing plates attached on both sides is illuminated with illumination from below, and a transmission image is taken with the upper camera, but a specific work conveying method is not disclosed. If a general method is used, it is conceivable to hold the non-display area (periphery) of the liquid crystal panel. However, in the case of the polarizing plate unit inspection, since there is almost no non-display area, it is not possible to hold the non-display area. Have difficulty. Therefore, a part of the display area must be gripped, and the gripped part cannot be inspected. For this reason, the gripped portion must be separately inspected by moving the workpiece, and the inspection time becomes long.
・ Because the polarizing plate is as thin as 1 mm or less, the warpage increases as the size increases. If the warp is large, the lens may deviate from the depth of field (out of focus), and an appropriate image cannot be captured. Although it is assumed that a backup pin or the like is used, the portion around the pin cannot be irradiated with light, and this portion must be separately inspected.
-When a defective part is detected, it cannot be distinguished whether the upper or lower polarizing plate is defective. Moreover, the adhered foreign matter on the surface of the polarizing plate also becomes defective.

  The present invention has been made to solve the above problems, and an optical film inspection method capable of reliably detecting defects in a thin optical film alone such as a polarizing plate up to a position in the thickness direction of the optical film. And it aims at providing an inspection device.

  An optical film inspection apparatus according to the present invention includes a light source that emits light, an imaging unit that includes at least one camera that captures light from the light source, and an optical that is an inspection target between the light source and the imaging unit. Two light-transmitting plate members that transmit light from a light source arranged so as to sandwich the film, an imaging unit, and two light-transmitting plate members are provided on the surfaces of the two light-transmitting plate members. In an optical film inspection apparatus including a drive mechanism that changes a relative positional relationship in parallel directions, an imaging unit is a coarse image captured through a lens having a depth of field that is equal to or greater than the thickness of the optical film. And two types of images, that is, a fine image captured through a lens having a depth of field of half or less of the thickness of the optical film.

  Since the optical film inspection apparatus according to the present invention is configured as described above, it can perform defect inspection over the entire area of the optical film as an inspection object without being affected by warpage, and can also detect defect position information (planar surface). And the thickness direction) can be obtained. Furthermore, from the information on the thickness direction of the defect, foreign matter and scratches on the protective film can be made unquestioned, and the inspection performance is improved.

It is a cross-sectional schematic diagram which shows schematic structure of the inspection apparatus of the optical film by Embodiment 1 of this invention. It is a cross-sectional schematic diagram which shows schematic structure in the preparation state of the test | inspection of the optical film test | inspection apparatus by Embodiment 1 of this invention. It is a flowchart for demonstrating the operation | movement of the rough image imaging of the inspection apparatus of the optical film by Embodiment 1 of this invention. It is a flowchart for demonstrating the operation | movement of the fine image imaging of the inspection apparatus of the optical film by Embodiment 1 of this invention. It is a cross-sectional schematic diagram for demonstrating operation | movement of the inspection apparatus of the optical film by Embodiment 1 of this invention. It is a partially expanded sectional view for demonstrating operation | movement of the inspection apparatus of the optical film by Embodiment 1 of this invention. It is another partial expanded sectional view for demonstrating operation | movement of the inspection apparatus of the optical film by Embodiment 1 of this invention. It is a cross-sectional schematic diagram which shows schematic structure of the inspection apparatus of the optical film by Embodiment 2 of this invention. It is a flowchart for demonstrating the operation | movement of the fine image imaging of the inspection apparatus of the optical film by Embodiment 2 of this invention.

Embodiment 1 FIG.
FIG. 1 is a schematic cross-sectional view showing a schematic configuration of an optical film inspection apparatus according to Embodiment 1 of the present invention. Hereinafter, a polarizing plate used for a liquid crystal panel will be described as an example of the optical film to be inspected. The optical film inspection apparatus according to Embodiment 1 of the present invention as a whole transmits the illumination light from the light source 2 to the polarizing plate 1 to be inspected, and the two CCD cameras 3 and 4 constituting the imaging unit 30. Thus, the image of the polarizing plate 1 is taken. The polarizing plate 1 is sandwiched and held between a light source side light transmissive plate member 50 that transmits light from the light source 2 and a camera side light transmissive plate member 51. The light source side light transmissive plate member 50 and the camera side light transmissive plate member 51 are, for example, transparent glass plates. The light source side light transmissive plate member 50 and the camera side light transmissive plate member 51 are supported on an inspection stage 7 having a uniaxial actuator as a drive mechanism. The inspection stage 7 can be moved in the Y direction which is a direction perpendicular to the paper surface while holding the polarizing plate 1. The light source side light transmissive plate member 50 is supported by an air cylinder 6 attached to the inspection stage 7. The air cylinder 6 as a drive mechanism is for moving the light source side light transmissive plate member 50 in the Z direction which is the vertical direction.

  The imaging unit 30 is installed on an imaging unit drive stage 8 including an X-axis actuator 80 and a Z-axis actuator 81 as drive mechanisms so as to be movable in the X-axis and Z-axis directions. On the other hand, an air cylinder 9 is attached to the light source 2 so that the light source 2 can move in the X direction, and the light source 2 is moved to come under the imaging unit 30. The light source 2 is preferably an LED light source that emits a near-infrared wavelength (880 nm) collimated so that the emitted light approaches a parallel light beam. By using illumination light as collimated light, a sharp transmitted image can be obtained as an image captured by the camera. In the near-infrared region, there is almost no polarizing action of the polarizing plate (= light attenuation due to the polarizing action is small), so that the contrast between the non-defective part (background) and the defective part is increased, and the detection sensitivity can be increased. Therefore, a light source that emits light of near-infrared wavelength is desirable as the light source.

  Each of the two cameras 3 and 4 has a lens attached thereto, but the optical magnification and the depth of field are different. One camera includes a lens having a depth of field that is equal to or greater than the thickness of the inspection object, and the other camera includes a lens having a depth of field that is less than or equal to one-half the thickness of the inspection object. The camera 3 having a depth of field that is equal to or greater than the thickness of the inspection object is referred to as a rough camera, and the camera 4 having a depth of field that is equal to or less than one half of the thickness of the inspection object is referred to as a fine camera. Generally, the coarse camera lens magnification is smaller than the fine camera lens magnification.

  In addition, a defect inspection control analysis device 20 that controls various drive mechanisms such as an actuator and processes and analyzes captured images is provided.

  The operation of the optical film inspection apparatus according to the first embodiment will be described below with reference to the operation flowcharts shown in FIGS. FIG. 3 is a flow chart of the coarse image capturing step showing the process of specifying the XY position of the defect based on the image captured by the coarse camera 3. In the coarse image capturing step, first, as shown in FIG. 2, the polarizing plate 1 is set on the light source side light transmissive plate member 50 (step ST1 in FIG. 3). The setting method may be manual or delivery by robot. The polarizing plate 1 may be set in a state where a protective film that is still supplied from the manufacturer is attached. After the setting, the air cylinder 6 moves the light source side light transmissive plate member 50 in the direction of the arrow shown in the vicinity of the air cylinder 6 in FIG. 2 according to a signal from the inspection target holding control unit 24 of the defect inspection control analysis apparatus 20, that is, The polarizing plate 1 is sandwiched between the light source side light transmissive plate member 50 and the camera side light transmissive plate member 51. A state where the polarizing plate 1 is sandwiched between the light source side light transmissive plate member 50 and the camera side light transmissive plate member 51 is shown in FIG. After sandwiching the polarizing plate 1, the inspection stage 7 moves to a preset position for each inspection object (ST 3), picks up the image of the polarizing plate 1 to be inspected with the coarse camera 3 and captures the image (ST 4). The presence or absence of a defect is determined by the image processing unit 21 of the defect inspection control analysis apparatus 20 (ST5). Here, an image captured by the coarse camera 3 is referred to as a coarse image. Due to the transmitted illumination, in the obtained image, the non-defective part is bright and the defect is dark. Whether it is a defect or not is determined based on the size and area of the dark part. If a defect exists, the defect position (X, Y) is stored in the defect position storage unit 22 of the defect inspection control analyzer 20 (ST6). While the inspection of the entire area of the polarizing plate 1 is not completed (ST7 NO), the inspection stage 7 is moved in synchronization with the Y direction and the coarse camera 3 is moved in synchronization with the X direction (ST8). Until the process is completed, the coarse image is captured by the coarse camera 3 (ST4), the defect determination (ST5), and the defect position storage (ST6) are repeated. Steps ST4 to ST6 are called defect position specifying steps.

  When the imaging of the entire area of the polarizing plate 1 and the defect position specification are completed (YES in ST7), the process proceeds to the operation flow of the fine image imaging step shown in FIG. 4 for specifying the position of the defect in the Z direction. If a defect exists (ST9 YES), the inspection position control unit 23 of the defect inspection control analysis apparatus 20 issues a command based on the information on the defect position stored in the defect position storage unit 22, and the precision camera 4 The inspection stage 7 and the imaging unit drive stage 8 are controlled so that a defect comes below (ST10). Step ST10 is referred to as a fine image capturing preparation step. At that time, as shown in FIG. 5, the air cylinder 9 is controlled by a command from the light source position control unit 25 of the defect inspection control analysis apparatus 20, and the light source 2 is moved so as to be under the precision camera 4.

  As shown in the partially enlarged cross-sectional view of the inspection target portion in FIG. 6, the precision camera 4 is moved in the Z direction to a position (= just focus position 10) where the lower surface of the camera side light transmissive plate member 51 is in focus. Take an image. Further, while moving the precision camera 4 downward by a predetermined distance in the Z direction, images are taken at predetermined intervals (ST11). These images are called fine images. The predetermined interval at this time is a depth of field d of the precision camera as shown in FIG. Since the imaging is repeated for each depth of field d, the defect 12 existing on any one of the upper surface, the inside, and the lower surface of the polarizing plate 1 to be inspected can be imaged. The image processing unit 21 of the defect inspection control analysis apparatus 20 analyzes a plurality of fine images captured in the Z direction, and selects a fine image having the largest sum of the defect position vicinity differential values among the plurality of fine images. It is assumed that a just focus image is extracted (ST12), and a position where the fine image is captured is an existing position in the thickness direction of the defect, that is, a defect existing layer (ST13). Here, if the depth of field d of the precision camera is half or less of the thickness of the inspection object, at least three fine images of the upper surface, the inside, and the lower surface of the inspection object can be captured, The position in the thickness direction can be specified with a resolution corresponding to the depth of field of the camera that captures the fine image. The depth of field d of the precision camera is preferably equal to or less than the thickness of the thinnest layer when the layer structure of the optical film to be inspected such as the polarizing plate 1 to be inspected is known. Specifically, in the case of a polarizing plate used for a liquid crystal panel, the thickness is generally about 400 to 600 μm, and the depth of field of the precision camera may be about 30 μm.

In the present invention, the depth of field refers to a value defined by the following equation.
Depth of field d = forward depth of field df + backward depth of field dr
df = (permissible circle of confusion x F value x object distance ^ 2) / (focal length ^ 2 + permissible circle of confusion x F value x object distance)
dr = (permissible circle of confusion x F value x object distance ^ 2) / (focal length ^ 2-permissible circle of confusion x F value x object distance)

  When the defect existence layer is not obtained for all the defect positions stored in the defect position storage unit 22 (ST14 NO), the inspection camera 7 and the imaging unit drive stage 8 are controlled to move the precision camera 4 to the next defect position. (ST15) and repeat steps ST11 to ST15.

  When the defect existence layer is obtained for all the defect positions stored in the defect position storage unit 22 (ST14 YES), the obtained defect information such as the size, area, number, and existence position of the obtained defect information is comprehensively obtained. Therefore, it is determined whether the polarizing plate cannot be used for the liquid crystal panel (NG) or the polarizing plate that can be used for the liquid crystal panel (OK) (ST16). For example, when inspecting with the protective film attached to the polarizing plate 1 to be inspected, if it is determined that the defect is a defect on the protective film attached to the top and bottom of the polarizing plate, the defect is It can be determined that it is a foreign matter or scratch on the protective film, and the defect can be made unquestioned. The determination is performed, for example, in the image processing unit 21 having a determination logic. In this way, the results determined by comprehensively determining the polarizing plate 1 to be inspected are output as NG output (ST17) and OK output (ST18), and the light source side light transmissive plate member 50 is lowered (ST19). ), The polarizing plate 1 to be inspected is taken out (ST20).

  According to such an optical film inspection method and apparatus according to Embodiment 1 of the present invention, the stage and the camera are supported in a state where the inspection target is supported while being sandwiched between two light transmissive plate members. Since it moves, the light which irradiated the illumination object light from the light source over the whole test object can be imaged with an upper camera. Further, since the inspection target is sandwiched between the plate members, the warpage of the inspection target can be suppressed, and the inspection can be performed with the flatness maintained. Furthermore, by moving the precision camera in the optical axis direction to capture a plurality of precision images and extracting a focused image from the precision images, the position in the thickness direction of the defect is clarified. Can do. As described above, even if the object to be inspected is a polarizing plate with a protective film attached, foreign matter or scratches on the protective film attached to the top and bottom of the polarizing plate can be made unquestioned, and the inspection accuracy Will improve. Moreover, since a defective layer becomes clear, the effect that a feedback bag is applied to a polarizing plate manufacturing process is also acquired.

  As described above, the inspection object may be in a state where protective films are attached to the upper and lower surfaces of the polarizing plate. Since the transmitted light is diffused by the protective film, the image is slightly blurred. However, since the contrast between the background (bright) and the defective part (dark) is high, there is no problem. In the above description, the polarizing plate is described as an example of the inspection target. However, the inspection target is not limited to the polarizing plate, and may be a single-layer optical film other than the polarizing plate or a multilayer optical film. Can be inspected.

Embodiment 2. FIG.
FIG. 8 is a schematic cross-sectional view showing a schematic configuration of an optical film inspection apparatus according to Embodiment 2 of the present invention. 8, the same reference numerals as those in FIG. 1 denote the same or corresponding parts. In the first embodiment, the imaging unit 30 is composed of two cameras, a coarse camera and a fine camera. However, in the second embodiment, as shown in FIG. 8, the imaging unit 30 is a camera 34 equipped with a zoom lens. It consists of only one camera. First, the optical magnification of the zoom lens of the camera 34 is set to be small so that the depth of field of the lens is equal to or greater than the thickness of the inspection target. The coarse image capturing step from step ST1 to ST8 in FIG. 3 until YES in step ST7 is executed by the camera of this setting, and the defect position is specified using the coarse image and stored in the defect position storage unit 22. Let

  Next, the fine image capturing step is executed according to the operation flow shown in FIG. 9, steps with the same reference numerals as those in FIG. 4 indicate steps for performing the same operations. First, the optical magnification of the zoom lens of the camera 34 is changed and set so that the depth of field of the lens is half or less of the thickness of the inspection object (ST101). Thereafter, the inspection position control unit 23 of the defect inspection control analysis apparatus 20 issues a command based on the information on the defect position stored in the defect position storage unit 22 so that the defect comes under the camera 34. 7 and the imaging unit drive stage 8 are controlled (ST102). At that time, the air cylinder 9 is controlled in accordance with a command from the light source position control unit 25 of the defect inspection control analyzer 20, and the light source 2 is also moved so as to come under the camera 34. Step ST101 and step ST102 may be reversed in order.

  Hereinafter, steps ST11 to ST20 are the same as those described in the first embodiment based on FIG. In this way, first, the zoom lens of the camera 34 is set to a state in which the optical magnification is small, and a rough image is captured to specify the XY two-dimensional position of the defect. Next, the zoom lens of the camera 34 is set to a state in which the optical magnification is large, a fine image of each defect position specified by the coarse image is captured, and the Z-direction position of the defect is specified, whereby the inspection object is a product. Whether it can be used can be determined.

  Although the case where the camera 34 includes a zoom lens has been described above, the camera 34 is a camera whose lens can be exchanged, and a lens whose depth of field is equal to or greater than the thickness of the inspection object is attached, and the rough image of FIG. Execute the step of specifying the XY two-dimensional position of the defect, and then change to a lens whose depth of field is less than half of the thickness of the inspection object, and specify the position of the defect in the Z direction by the fine image of FIG. You may perform the step to do.

  As described above, in the second embodiment, one camera is used. However, even in this configuration, as in the first embodiment, the focal point for each depth of field of the lens that moves in the optical axis direction and captures a fine image is obtained. The position of the defect in the thickness direction can be clarified by capturing a plurality of fine images by changing the distance and extracting the focused image. Moreover, even if the inspection target is a polarizing plate with a protective film attached, foreign matter or scratches on the protective film attached to the top and bottom of the polarizing plate can be made unquestioned, and the inspection accuracy is improved. There is an effect.

  In the first and second embodiments described above, the CCD camera may be a visible light type or a near infrared type as long as it is a camera sensitive to the wavelength of the light source. A line sensor may also be used. In the case of a line sensor, imaging is performed while moving the inspection object. Further, as the light source, an LED light source is preferable in consideration of lifetime and deterioration, but a light source other than an LED such as a halogen light source may be used. The light source side light transmissive plate member 50 and the camera side light transmissive plate member 51 are made of transparent glass, but may be a transparent resin such as acrylic. The inspection object 1 is moved by moving the two light transmissive plate members on the inspection stage 7, but the inspection object 1 is fixed, and the imaging unit 30 and the light source 2 are moved together in the XY two-dimensional direction. Also good. In short, it is only necessary to have a drive mechanism that changes the relative positional relationship between the imaging unit 30 and the inspection object 1, that is, two light transmissive plate members, in a direction parallel to the surface of the light transmissive plate member.

  It should be noted that the present invention can be combined with each other within the scope of the invention, or can be appropriately modified or omitted from each embodiment.

1: Polarizing plate (inspection target) 2: Light source 3: Coarse camera 4: Precision camera 7: Inspection stage (drive mechanism) 8: Imaging unit drive stage (drive mechanism) 9: Air cylinder (drive mechanism) ), 20: Defect inspection control analysis device, 21: Image processing unit, 22: Defect position storage unit, 23: Defect position control unit, 24: Defect target holding control unit, 25: Light source position control unit, 30: Imaging unit, 34: Camera equipped with zoom lens, d: Depth of field of precision camera

Claims (11)

A light source that emits light;
An imaging unit including at least one camera for imaging light from the light source;
Two light transmissive plate members that transmit light from the light source disposed so as to sandwich an optical film to be inspected between the light source and the imaging unit;
Inspection of an optical film provided with a drive mechanism that changes a relative positional relationship between the imaging unit and the two light transmissive plate members in a direction parallel to the surfaces of the two light transmissive plate members. In the device
The imaging unit includes a coarse image captured through a lens having a depth of field that is equal to or greater than the thickness of the optical film, and a lens having a depth of field that is less than or equal to one half of the thickness of the optical film. An inspection apparatus for an optical film, which picks up two types of images of a fine image picked up.   The imaging unit is composed of a coarse camera having a depth of field greater than or equal to the thickness of the optical film and a fine camera having a depth of field of less than or equal to one half of the thickness of the optical film. The optical film inspection apparatus according to claim 1.   The optical film inspection apparatus according to claim 1, wherein the imaging unit includes a single camera including a zoom lens. A defect position storage unit that identifies a two-dimensional position of the defect of the optical film in a direction parallel to the surfaces of the two light-transmitting plate members from the rough image, and stores the identified position as a defect position. When,
Image processing for picking up a plurality of fine images with different focal positions as the fine image at one defect position stored in the defect position storage unit and specifying the position of the defect in the thickness direction of the optical film And
The optical film inspection apparatus according to claim 1, comprising:   5. The optical device according to claim 4, wherein the plurality of fine images having different focal positions are a plurality of fine images picked up by changing a focal position for each depth of field of a lens that picks up the fine image. Film inspection device.   A drive mechanism for changing the positions of the imaging unit and the light source so that the relative positions of the imaging unit and the light source in the direction parallel to the surfaces of the two light-transmissive plate members do not change; The optical film inspection apparatus according to claim 1, wherein:   The optical film inspection apparatus according to claim 1, wherein the light source is an LED light source that emits collimated radiation so as to approach parallel light. An optical film inspection method using the optical film inspection apparatus according to claim 1, wherein the coarse image capturing step captures the coarse image;
A method for inspecting an optical film, comprising: a fine image capturing step that captures the fine image after the rough image capturing step. In the rough image capturing step, a two-dimensional position in a direction parallel to the surfaces of the two light-transmitting plate members of the optical film to be inspected is determined from the rough image captured in the rough image capturing step. Identifying and storing a defect location step as a defect location,
In the fine image capturing step, a relative positional relationship between the imaging unit and the two flat plates in a direction parallel to the surfaces of the two light transmissive plate members is determined in the defect position specifying step. 9. The method for inspecting an optical film according to claim 8, further comprising a fine image capturing preparation step for setting the fine image at the stored defect position to a positional relationship acquired in the fine image capturing step.   The optical film inspection method according to claim 9, wherein, in the fine image capturing step, a plurality of fine images having different focal positions are captured as the fine images.   The optical film inspection method according to claim 10, wherein, in the fine image capturing step, a plurality of fine images are picked up by changing a focal position for each depth of field of a lens that picks up the fine image.

Images