JP2008241607A - Apparatus and method for detecting optical unevenness - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable a measurement of a full surface photographing to be carried out easily and precisely in a short time in an unevenness photographing of a cross-nicol configuration, wherein a phase difference film is sandwiched by two polarizers. <P>SOLUTION: An optical unevenness detecting apparatus 100 for detecting an optical unevenness of the phase difference film is provided with: a stage 25 for integrally holding and setting the phase difference film and the polarizers at a desired tilt angle; an illuminating means 27 for illuminating one side of the phase difference film; a photographing means 29 for photographing a transmission light screen of the illumination light from the illuminating means 27 through the polarizer on the other side of the phase difference film; and an unevenness detecting means 31 for detecting a brightness uneven component based on brightness information of a photographed image obtained by the photographing means 29. The photographing means 29 telephotographs from a position which is spaced from the phase difference film such that the angle variation along the photographing direction in a prescribed inspection area of the phase difference film is equal to or less than two degrees. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical unevenness detection device and an optical unevenness detection method for detecting optical unevenness, and is particularly suitable for use in an inspection target in which a retardation film is sandwiched between a pair of polarizing plates in a crossed Nicols state.

  For example, some liquid crystal panels have a retardation film sandwiched between a pair of polarizing plates in a crossed Nicols state. In this type of liquid crystal panel, the retardation film material itself has local non-uniformity and may cause unevenness. Therefore, an image display inspection is performed to inspect whether a display defect has occurred in the manufacturing process. . This image display inspection is performed by picking up an image of the liquid crystal panel with an image pickup means (CCD camera or the like), or by observing the observer from a different position.

FIG. 10 is an explanatory diagram showing luminance unevenness observation from only the central portion of the liquid crystal panel (a), and an example of unevenness seen thereby (b).
For example, as shown in FIG. 10A, the uneven imaging evaluation in the image display inspection is performed by fixed-point imaging with an imaging point 3 at a predetermined observation distance from the liquid crystal panel 1, and a panel screen (panel mounting or polarizing crossed Nicols). In the central part of the embodiment, the prospective angle is 0 degree, and the imaging is performed under the condition that the prospective angle increases as it approaches the end from the central part.

  In general, the observation distance is set to a distance about three times the height H of the panel to be inspected, and the imaging field of view range is about 60 mm square due to optical restrictions. Then, when the panel is displayed in black, uneven imaging evaluation has been performed by observing a high-luminance region (light-emitting region) generated around the panel. In the case of visual observation, it was assumed that there was unevenness in detection of a luminance difference of about 0.1 cd.

JP 2006-242821 A

However, since the conventional uneven imaging evaluation was performed in an imaging field of view of about 60 mm square, for example, for a non-uniform stripe, there was a problem that the field of view was too narrow to accurately determine the presence or absence of unevenness. FIG. 11 is an explanatory view showing the fixed point observation performed conventionally (a) and the actual observation of the observer moving in (b).
Actually, in addition to the fixed point observation shown in FIG. 11A, as shown in FIG. 11B, when the observer 1 moves the head sideways and observes, it is perpendicular or oblique to any position on the panel. Observe from the same direction. However, since the appearance of unevenness differs depending on the angle for each material to be inspected, it is necessary to acquire and evaluate images at a plurality of angles and distances. In addition, in the conventional uneven imaging evaluation, there is a case where imaging is performed after trial and error to determine the angle at which the degree of unevenness is worst while judging the degree of unevenness with the eyes, and there is a problem of poor work efficiency. . Furthermore, in order to evaluate the unevenness of a single material, it has been found that it is necessary to evaluate the evaluation in which the prospective angle is a fixed angle with respect to an arbitrary position of the inspection target.
FIG. 12 shows a graph showing the correlation between the expected angle and the luminance of the polarizing plate crossed Nicol and the VA panel with viewing angle adjusting film. In particular, when the sample form is not a mounting panel but is observed in a crossed Nicols form of two polarizing plates, as shown in FIG. 12, the luminance change due to the position of the captured image is large in correlation with the prospective angle. Since the image has a luminance gradient, it has been a factor that makes it difficult to detect unevenness.
FIG. 13 shows a schematic diagram of a conventional optical unevenness detection method using a telecentric lens. In the method of surface scanning an imaging means such as a CCD camera, an optical system 5 using a telecentric lens 4 is used for imaging from a parallel direction. However, if the area that can be captured in one shot is as narrow as about 20 mm in width and width W, and the TV panel that is the subject is 60 inches or more, there is a problem that about 1000 shots are required and a huge amount of time is required. It was.
The present invention has been made in view of the above situation. In particular, in uneven imaging in a crossed Nicol configuration in which a retardation film is sandwiched between two polarizing plates, it is easy to measure the entire surface, in a short time, and with high accuracy. It is an object to provide an optical unevenness detection device and an optical unevenness detection method.

The above object of the present invention is achieved by the following configuration.
(1) An optical unevenness detection device for detecting optical unevenness of a retardation film,
A pair of polarizing plates arranged in a crossed Nicols state across the retardation film to be inspected;
A stage for integrally holding the retardation film and the polarizing plate and setting a desired inclination angle;
Illumination means for illuminating from one side of the retardation film;
Imaging means for imaging a transmitted light screen of illumination light from the illumination means via the polarizing plate from the other side of the retardation film,
Unevenness detection means for detecting a brightness unevenness component from brightness information of a captured image obtained from the imaging means,
An optical non-uniformity detection device that performs telephoto imaging from a position spaced from the retardation film so that the imaging means has an angle variation in an imaging direction within a predetermined inspection region of the retardation film within 2 degrees.

  According to this optical unevenness detection device, when photographing each region of the inspection object in the same photographing direction at the time of close-up photographing, it has been necessary to scan the imaging means with respect to the inspection object. Without scanning, the entire object to be inspected can be imaged at substantially the same angle while suppressing the angle difference with respect to the imaging direction. Thereby, even if it is a case where a to-be-inspected object is inclined, an imaging focus can be adjusted. Therefore, unevenness measurement can be efficiently performed not only from a plurality of fixed points but also from all positions parallel to the inspection target.

(2) The optical unevenness detecting device according to (1),
The said imaging means is an optical nonuniformity detection apparatus in which the imaging area for one time of the said retardation film contains an area | region of at least 20 cm square.

  According to this optical unevenness detection apparatus, compared with an imaging area of about 2 cm using a telecentric lens used for conventional parallel photography, imaging information by substantially parallel photography can be obtained with a large imaging area. By reducing the number of imaging operations, the processing time can be greatly shortened.

(3) The optical unevenness detecting device according to (1) or (2),
Control means for driving the stage to incline the retardation film in a representative imaging direction composed of a plurality of specific directions, and for imaging in each representative imaging direction by the imaging means;
Storage means for storing the plurality of captured images;
The unevenness detecting means interpolates a luminance value with respect to an inclination direction intermediate between the representative imaging directions from the luminance value of the captured image in each representative imaging direction, and the luminance information is obtained from the luminance information obtained by the interpolation processing. An optical unevenness detection device that detects unevenness components.

  According to this optical unevenness detection device, the unevenness detecting means obtains the brightness value for the intermediate tilt direction from the brightness value of each representative image capturing direction obtained by image capturing in each representative image capturing direction, and actually captures the image. An overall image substantially equivalent to the obtained image is obtained. That is, by performing the image composition processing, a luminance image is generated at an arbitrary prospective angle, and unevenness detection can be performed efficiently.

(4) The optical unevenness detection device according to any one of (1) to (3),
An inclination angle that is an angle between the normal direction of the retardation film and the observation direction, and an azimuth angle in the retardation film plane when the observation direction is vertically projected on the retardation film surface. And an optical non-uniformity detection device having a rotation mechanism for changing.

  According to this optical unevenness detection device, the entire retardation film is imaged at substantially the same angle by telephoto imaging, and the tilt angle and azimuth angle are changed by driving the rotation mechanism, thereby imaging. Observation at any tilt angle and azimuth angle is possible for any position of the retardation film without scanning the means.

(5) An optical unevenness detection method for detecting optical unevenness of a retardation film,
The retardation film to be inspected is sandwiched between a pair of polarizing plates arranged in a crossed Nicol state, and set to a desired inclination angle,
Illuminating from one side of the retardation film, the transmitted light screen of the illumination light from the other side of the retardation film via the polarizing plate, the predetermined inspection region of the retardation film Telephoto imaging with the angle fluctuation in the imaging direction within the inspection area within 2 degrees,
An optical unevenness detection method for detecting a luminance fluctuation component from luminance information of a captured image obtained.

  According to this optical unevenness detection method, the entire object to be inspected can be photographed at substantially the same angle, and unevenness measurement from all positions parallel to the object to be inspected can be performed efficiently. As a result, it is possible to easily measure the entire surface imaging in a short time, and the measurement error associated with the scanning of the imaging means does not occur, so that the unevenness detection accuracy is increased.

(6) The optical unevenness detection method according to (5),
An optical unevenness detection method in which the retardation film is imaged from a plurality of different directions, and a luminance variation component is detected from each captured image in each imaging direction.

  According to this optical unevenness detection method, the entire retardation film is photographed at substantially the same angle by telephoto imaging, and in addition, imaging from a plurality of different directions, that is, the retardation film with respect to a fixed imaging means Due to the imaging with the displacement, it is possible to detect a luminance fluctuation component at an arbitrary inclination angle and azimuth angle for any position of the retardation film without scanning the imaging means.

(7) The optical unevenness detection method according to (5) or (6),
An optical unevenness detection method for imaging at least a 20 cm square region of the retardation film by one imaging.

  According to this optical unevenness detection method, compared with an imaging area of about 2 cm using a telecentric lens that has been used for conventional parallel photography, imaging information by substantially parallel photography can be obtained with a large imaging area. By reducing the number of imaging operations, the processing time can be greatly shortened.

(8) The optical unevenness detection method according to (5) to (6) or (7),
Inclining the retardation film in a representative imaging direction consisting of a plurality of specific directions, and imaging,
An optical for detecting the luminance unevenness component from the luminance information obtained from the luminance information obtained by the interpolation processing from the luminance value of the captured image in each representative imaging direction to obtain a luminance value with respect to an intermediate inclination direction of each representative imaging direction. Unevenness detection method.

  According to this optical unevenness detection method, the unevenness detection means interpolates the brightness value for the intermediate tilt direction from the brightness value of the captured image in each representative imaging direction obtained by imaging in each representative imaging direction, and the unknown The luminance unevenness component at the tilt angle can be estimated without depending on actual imaging.

(9) The optical unevenness detection method according to (8),
The transmission light screen of the illumination light observed at an arbitrary position facing the retardation film is synthesized from the luminance information obtained by the interpolation process, and the luminance information of the composite image of the transmission light screen An optical unevenness detecting method for detecting the luminance unevenness component from

  According to this optical unevenness detection method, an image that is actually captured is obtained by performing an image composition process based on a brightness unevenness component at an unknown inclination angle obtained by interpolating a brightness value with respect to an intermediate inclination direction. The luminance unevenness component can be efficiently detected in a short time from the substantially equivalent whole image.

  According to the optical unevenness detection apparatus according to the present invention, the stage for setting the inspection target to a desired inclination angle, the imaging unit for imaging the transmitted light screen of the illumination light from the illumination unit, and the luminance from the luminance information of the captured image A non-uniformity detection unit that detects a non-uniformity component, and the imaging unit performs telephoto imaging at a distance from the inspection target so that the angle variation in the imaging direction within a predetermined inspection region of the inspection target is within 2 degrees. Therefore, when each region of the inspection object is imaged in the same imaging direction as in the case of the conventional close-up imaging, the imaging means need not be scanned with respect to the inspection object without scanning the imaging means. The entire object to be inspected can be imaged at substantially the same angle while suppressing the angle difference with respect to the image capturing direction, and the imaging focus can be stably adjusted even when the object to be inspected is tilted. Accordingly, not only a plurality of fixed points, but also unevenness measurement from all observation directions of the object to be inspected can be performed easily and in a short time. In addition, since no measurement error due to scanning of the image pickup means occurs, the unevenness detection accuracy can be improved. In particular, in uneven imaging in a crossed Nicol configuration in which a retardation film is sandwiched between two polarizing plates, a significant effect can be obtained because the luminance changes greatly depending on the direction of light.

  According to the optical unevenness detection method according to the present invention, the inspection target is set to a desired inclination angle, the inspection target is illuminated from one side, and the transmitted light screen of the illumination light from the other side is set to a predetermined level. Telescopic imaging is performed with respect to the inspection area with the angle variation in the imaging direction within 2 degrees, and the luminance variation component is detected from the luminance information of the obtained captured image. And unevenness measurement from all the observation directions of the inspection object can be efficiently performed. As a result, it is possible to measure the entire surface image easily and in a short time, and the measurement error associated with the scanning of the image pickup means does not occur, so that the unevenness detection accuracy can be improved.

DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of an optical unevenness detection apparatus and an optical unevenness detection method according to the present invention will be described in detail with reference to the drawings.
FIG. 1 is a block diagram showing a schematic configuration of an optical unevenness detection apparatus according to the present invention, and FIG. 2 is an exploded perspective view of a pair of polarizing plates arranged in a crossed Nicols state with a retardation film to be inspected interposed therebetween, FIG. 3 is an explanatory diagram illustrating an inclination angle and an azimuth angle with respect to the object to be inspected.
The optical unevenness detection apparatus 100 shown in FIG. 1 of the present embodiment can be suitably used when detecting optical unevenness of the retardation film 21 of FIG. 2 provided on the display surface of the optical panel 19. The retardation film 21 is sandwiched between a pair of polarizing plates 23a and 23b arranged in a crossed Nicol state. The retardation film 21 sandwiched between the polarizing plates 23 a and 23 b is the inspection object 20 and is provided on the display surface of the optical panel 19.

The optical panel 19 is irradiated with light from the back, and an image is displayed on the display surface.
The optical unevenness detection apparatus 100 includes a stage 25, an illumination unit 27, an imaging unit 29, an unevenness evaluation unit 31 that is an unevenness detection unit, a control unit 33 that is a control unit, and a storage unit 35 that is a storage unit. , Has as a main configuration.

  The stage 25 is provided with a rotation movement mechanism 39 as a rotation mechanism, and the rotation movement mechanism 39 integrally includes the retardation film 21 and the polarizing plates 23a and 23b (that is, an optical panel provided with the inspection target 20). 19) and can be set to a desired posture. That is, as shown in FIG. 3, the rotational movement mechanism 39 has an inclination angle θ that is an angle between the normal line N direction of the retardation film 21 and the observation direction P, and the observation direction is perpendicular to the surface of the retardation film 21. The azimuth angle φ in the surface of the retardation film 21 when projected can be changed.

  The rotational movement mechanism 39 has a function of moving the optical panel 19 in the horizontal direction and the vertical direction. The rotational movement mechanism 39 is driven and controlled by a stage driving unit 41 to which a control signal is input from the control unit 33.

  An illumination unit 27 is provided on the back surface of the optical panel 19, and the illumination unit 27 illuminates from one side (rear side) of the retardation film 21. The illumination unit 27 is controlled to be turned on by an illumination control signal output from the backlight control unit 37 by sending a control signal from the control unit 33 to the backlight control unit 37. This illumination light passes through the optical panel 19 and the inspection target 20 and is observed from the display surface on the surface side of the optical panel 19. For the illumination means 27, for example, a linear light source is used. Although it does not specifically limit as a linear light source, A cold cathode tube, a hot cathode tube, LED arranged in a line, the combination of LED and a light guide, etc. can be used.

  The imaging means 29 has a function that allows the distance from the optical panel 19 to be adjusted. As the imaging means 29, a CCD camera (for example, Prometric 1400 from Radiant Imaging) can be used. A telephoto optical system (telephoto lens) 29a is attached to the image pickup means 29, and the optical panel 19 is imaged telephoto. The telephoto optical system 29 a can set the field angle area of the CCD camera to a range narrower than the entire area of the inspection target 20 at a distance of 15 to 30 m from the optical panel 19.

  That is, the imaging unit 29 captures the illumination light from the illumination unit 27 as a transmitted light screen from the other side of the retardation film 21 via the polarizing plates 23a and 23b, and within a predetermined inspection region of the retardation film 21. Telephoto imaging is performed from a position spaced from the phase difference film 21 so that the angle fluctuation in the imaging direction is within 2 degrees. The imaging means 29 can perform imaging in the inspection area with high accuracy by suppressing the angle difference in the imaging direction to 1 to 2 degrees. When the angle variation is larger than 2 degrees, the evaluation error increases and the unevenness detection accuracy decreases.

  As described above, in the optical unevenness detection apparatus 100, the entire retardation film 21 is photographed at substantially the same angle by telephoto imaging, and the tilt angle θ and the azimuth angle φ are changed by driving the rotational movement mechanism 39. As a result, it is possible to observe at any tilt angle θ and azimuth angle φ with respect to any position of the retardation film 21 without scanning the imaging means 29.

  More specifically, the imaging unit 29 is set so that the imaging area for one time of the retardation film 21 is an area including an imaging area of at least 20 cm square from the total area of the retardation film 21. Practically, it is preferable to perform evaluation with an A4 size (297 × 210 mm). By performing imaging at such an A4 size, imaging by approximately parallel imaging is performed compared to an imaging area of approximately 2 cm square using the telecentric lens 4 (see FIG. 13) that has been performed for conventional parallel imaging. Information can be obtained with a large imaging area, and the number of times of imaging can be reduced, thereby significantly reducing the processing time.

  The control unit 33 drives the stage 25 to incline the retardation film 21 in a representative imaging direction including a plurality of specific directions, and enables imaging control in each representative imaging direction by the imaging unit 29. For example, a personal computer can be used as the control unit 33. The storage unit 35 stores a plurality of pieces of captured image information captured by the imaging unit 29 and transferred to the control unit 33. As the storage unit 35, an internal memory or an external storage device of a personal computer can be used.

  The unevenness evaluation unit 31 interpolates and obtains a luminance value with respect to an intermediate tilt direction of each representative imaging direction from the luminance value of the captured image in each representative imaging direction. The unevenness evaluation unit 31 can detect a luminance unevenness component from the luminance information obtained by this interpolation processing. The unevenness evaluation unit 31 can be software stored in a personal computer. The unevenness evaluation unit 31 interpolates and obtains a luminance value for an intermediate inclination direction from the luminance value in each representative imaging direction, and obtains an overall image that is substantially equivalent to the actually captured image. That is, by performing the image synthesis process, a luminance image is generated at an arbitrary prospective angle (θ, φ), so that unevenness detection can be performed efficiently.

FIG. 4 is a schematic diagram of an object to be inspected that is tilted in the representative imaging direction by stage control, and FIG. 5 is a partially enlarged view of the object to be inspected that is imaged at different angles with different imaging directions.
The control unit 33 sends an image pickup control signal and a drive control signal to the image pickup unit 29 and the stage 25 to incline the optical panel 19 in the representative image pickup direction. For example, as shown in FIG. 4 (a), the optical panel 19 is not tilted, and imaging with an inclination angle θ ₀ with respect to the imaging direction is 0 degrees. As shown in FIG. ₁ is inclined, and imaging angle of the imaging direction an inclined angle theta _1, as shown in FIG. 4 (c), the optical panel 19 by alpha ₂ inclination, the angle between the imaging direction inclination angle theta ₂ Continuous imaging is performed.

When the optical panel 19 is telephoto picked up by the image pickup means 29, the optical panel 19 shown in FIG. 4A is not tilted, or as shown in FIGS. 4B and 4C, the optical panel 19 Even in the case of imaging with tilted 19, as shown in FIGS. 5A and 5B, the tilt angles θ ₀ and θ _a are aligned at any position of the inspected object 20 and imaging from the same direction becomes possible. .

  As described above, in the optical nonuniformity detection apparatus 100, it has been conventionally necessary to scan the imaging unit 29 with respect to the inspection target 20 when shooting each region of the inspection target 20 in the same shooting direction at the time of close-up shooting. On the other hand, the entire inspection object 20 can be imaged at substantially the same angle while suppressing the angle difference with respect to the imaging direction without scanning the imaging means 29. In addition, even when the inspection target 20 is tilted, the entire imaging region can be focused because the depth of field is deep. Therefore, not only a plurality of fixed points but also the position of an arbitrary inspection object 20 can be favorably imaged for unevenness measurement from an arbitrary direction.

Next, an optical unevenness detection method using the optical unevenness detection apparatus 100 will be described.
FIG. 6 is a flowchart showing the basic procedure of the optical unevenness detection method according to the present invention.
Here, a case where a part of the inspection target 20 is evaluated will be described as an example. However, the present invention is not limited to this, and the entire surface of the inspection target 20 is evaluated, or the entire surface is divided into a plurality of representative regions (for example, four corners and the center). ) May be evaluated multiple times.

  First, the retardation film 21 as the inspection target 20 is sandwiched between a pair of polarizing plates 23a and 23b arranged in a crossed Nicol state and set on the stage 25 (S1). Then, a drive control signal sent out by the control unit 33 is sent to the stage 25 through the stage drive unit 41, and the inspection target 20 is set to a desired tilt angle θ and azimuth angle φ.

  Next, a control signal sent out by the control unit 33 is input to the illumination unit 27 via the backlight control unit 37, and illumination is performed from the back side of the retardation film 21, and polarization is performed from the display surface side of the retardation film 21. The transmitted light screen of the illumination light is telephoto picked up by the image pickup means 29 through the plates 23a and 23b (S2). At this time, telescopic imaging is performed with respect to a predetermined inspection area of the retardation film 21 with an angle variation in the imaging direction within the inspection area being within 2 degrees. In one imaging, an area of at least 20 cm square of the retardation film 21, more specifically, an A4 size area is imaged. This telephoto imaging is repeated in all directions with a preset tilt angle θ and azimuth angle φ (S3).

  Next, a luminance fluctuation component is detected from the luminance information of the obtained captured image. The brightness information of the captured image is stored in the storage unit 35. That is, the phase difference film 21 was imaged from a plurality of different directions of inclination angles θ (0 °, 30 °, 40 °, 50 °,...) And azimuth angles φ (0 °, 45 °, 90 °,...). The captured image data (for example, 256 gradations) is stored in each table as shown in FIG. For example, captured image data at an azimuth angle φ = 45 ° and an inclination angle θ = 30 ° is stored as shown in FIG.

  Then, the phase difference film 21 is imaged while being tilted in a specific imaging direction composed of a plurality of specific directions, and a luminance value with respect to an intermediate tilt direction of each representative imaging direction is interpolated from the captured image data of each representative imaging direction. Obtain (S4).

  Specifically, for each pixel of the captured image data with respect to the discrete tilt angle θ and azimuth angle φ, interpolation processing is performed using the brightness values of the captured image data with other tilt angles θ and azimuth angles φ, and any The image data of the inclination angle θ and the azimuth angle φ is analytically obtained. The interpolation process may be obtained by linear interpolation from the change in the tilt angle θ or the change in the azimuth angle φ for the pixels at the same position, but for the average luminance value of the specific pixel and the surrounding pixels. Then, the luminance change due to the change in the inclination angle θ and the azimuth angle φ may be obtained by linear interpolation. In addition to linear interpolation, interpolation processing may be performed by approximating an appropriate curve.

  Next, a transmitted light screen of illumination light observed at an arbitrary position facing the phase difference film 21 is created by synthesizing from luminance information obtained by interpolation processing. Based on the luminance information of the composite image on the transmitted light screen, the unevenness evaluation unit 31 detects a luminance unevenness component. That is, the unevenness is quantitatively evaluated using the luminance information for all the observation directions of the retardation film 21 (S5). As an evaluation method at this time, an observation position where the degree of unevenness is maximized is searched, and based on the degree of unevenness at the observation position, for example, Weber-Fechner's law, the luminance difference / background luminance is quantified. It can be obtained as an evaluation value.

Here, unevenness with respect to an arbitrary fixed observation direction can be evaluated by analytically obtaining luminance information with respect to an arbitrary observation direction as described above.
Further, when the inclination angle of the optical panel 19 shown in FIG. 9A is 0 degree (a direction in which the true front faces the normal direction), or an arbitrary angle θ _{p as} shown in FIG. 9B. Even in this case, since luminance information is analytically obtained for each of the tilt angles θ ₀ , θ _L1 , θ _L2 , θ _R1 , and θ _R2 representing the observation direction of the optical panel 19, by combining them, An observation image as if it were at the observation position can be synthesized. Therefore, if the synthesized observation image is used, it is possible to evaluate unevenness at an arbitrary observation position.

  In order to facilitate the detection of unevenness, the contrast is enhanced by image processing. At that time, when the contrast is enhanced in the conventional method, the unevenness in the center is enhanced, but the region with a large prospective angle becomes a white-crushed image and the unevenness becomes invisible. As a result, unevenness is emphasized, and detection of unevenness becomes easier. In this way, after the unevenness is quantitatively evaluated for the observation image data in all directions, the level of unevenness of the single retardation film that is the inspection target 20 is output, and the detection of the optical unevenness is finished.

  In this optical unevenness detection method, the entire inspection object 20 can be imaged at substantially the same angle, and the discrete representative imaging directions can be obtained without actually measuring luminance information in all directions in which the inspection object 20 is observed. By obtaining analytically from the results measured from the above, unevenness measurement can be easily performed in a short time. In addition, since no measurement error due to the scanning of the imaging means 29 occurs, the unevenness detection accuracy is also increased.

  Further, by performing telephoto imaging with a deep subject depth, the entire retardation film 21 can be photographed in a stable and in-focus state, and there is no need to finely adjust and set the imaging means 29. In addition, compared with the imaging area of about 2 cm using a telecentric lens that has been used for conventional parallel imaging, imaging information by substantially parallel imaging can be obtained with a large imaging area. For this reason, it is possible to shorten the processing time by reducing the number of times of imaging.

Therefore, according to the optical unevenness detection device 100, when each region of the inspection target 20 is imaged in the same imaging direction as in conventional close-up imaging, it is necessary to scan the imaging unit 29 with respect to the inspection target 20. Compared to the case, the entire inspection object 20 can be imaged at substantially the same angle while suppressing the angle difference with respect to the imaging direction without scanning the imaging means 29, and the inspection object 20 is tilted. Also, the imaging focus can be reliably adjusted. With such a configuration, for example, a luminance difference of 0.1 cd / m ² can be detected with high accuracy.

  In particular, in the uneven imaging in the crossed Nicol configuration in which the retardation film 21 is sandwiched between two polarizing plates, the luminance greatly changes depending on the direction of light. Obtainable.

  In the above-described embodiment, the case where the object to be inspected is provided on the optical panel 19 has been described as an example. However, the optical unevenness detection device and the optical unevenness detection method according to the present invention are also liquid crystal panels (described above). The present invention can also be applied to a case where a liquid crystal cell is interposed between the polarizing plates 23a and 23b of the optical panel 19), or when measuring luminance unevenness of a large display installed outdoors. Effects can be obtained.

It is a block diagram showing the schematic structure of the optical nonuniformity detection apparatus which concerns on this invention. It is a disassembled perspective view of a pair of polarizing plate arrange | positioned in the crossed Nicols state on both sides of the phase difference film which is a test object. It is explanatory drawing which illustrated the inclination angle and azimuth with respect to to-be-inspected object. It is a schematic diagram of the inspection object imaged by tilting in the representative imaging direction by stage control. It is a partial enlarged view of a test object to be imaged at different angles with different imaging directions. It is a flowchart showing the basic procedure of the optical nonuniformity detection method which concerns on this invention. It is explanatory drawing which shows a part of data of the imaging location for every inclination | tilt angle and azimuth. It is explanatory drawing which shows a part of brightness | luminance information of the captured image in the representative point in azimuth | direction angle 45 degrees and inclination-angle 30 degrees. It is explanatory drawing which shows the observation direction when the inclination angle of an optical panel is set to 0 degree | times (a), and when it makes arbitrary angle (theta) _p (b). It is explanatory drawing which represented the brightness nonuniformity observation only from the conventional center part to (a), and the example of the nonuniformity visible by it is represented to (b). It is explanatory drawing which represented the fixed observation observed conventionally (a) and the actual observation to which an observer moves to (b). It is a graph showing the correlation with the angle of view and the brightness | luminance of polarizing plate cross Nicol and a VA panel with a viewing angle adjustment film. It is a schematic diagram of the conventional optical nonuniformity detection method using a telecentric lens.

Explanation of symbols

DESCRIPTION OF SYMBOLS 19 Optical panel 20 Inspected object 21 Phase difference film 23a, 23b Polarizing plate 25 Stage 27 Illumination means 29 Imaging means 31 Unevenness evaluation part (unevenness detection means)
33 Control unit (control means)
35 storage unit (storage means)
39 Rotating and moving mechanism 100 Optical unevenness detection device φ Azimuth angle θ Inclination angle

Claims (9)

An optical unevenness detection device for detecting optical unevenness of a retardation film,
A pair of polarizing plates arranged in a crossed Nicols state across the retardation film to be inspected;
A stage for integrally holding the retardation film and the polarizing plate and setting a desired inclination angle;
Illumination means for illuminating from one side of the retardation film;
Imaging means for imaging a transmitted light screen of illumination light from the illumination means via the polarizing plate from the other side of the retardation film,
Unevenness detection means for detecting a brightness unevenness component from brightness information of a captured image obtained from the imaging means,
An optical non-uniformity detection device that performs telephoto imaging from a position spaced from the retardation film so that the imaging means has an angle variation in an imaging direction within a predetermined inspection region of the retardation film within 2 degrees. The optical unevenness detection device according to claim 1,
An optical unevenness detection apparatus, wherein the imaging means includes an area of at least 20 cm square for one imaging area of the retardation film. The optical unevenness detection device according to claim 1 or 2,
Control means for driving the stage to incline the retardation film in a representative imaging direction composed of a plurality of specific directions, and for imaging in each representative imaging direction by the imaging means;
Storage means for storing the plurality of captured images;
The unevenness detecting means interpolates a luminance value with respect to an inclination direction intermediate between the representative imaging directions from the luminance value of the captured image in each representative imaging direction, and the luminance information is obtained from the luminance information obtained by the interpolation processing. An optical unevenness detection device that detects unevenness components. The optical unevenness detection device according to any one of claims 1 to 3,
An inclination angle that is an angle between the normal direction of the retardation film and the observation direction, and an azimuth angle in the retardation film plane when the observation direction is vertically projected on the retardation film surface. And an optical non-uniformity detection device having a rotation mechanism for changing. An optical unevenness detection method for detecting optical unevenness of a retardation film,
The retardation film to be inspected is sandwiched between a pair of polarizing plates arranged in a crossed Nicol state, and set to a desired inclination angle,
Illuminating from one side of the retardation film, the transmitted light screen of the illumination light from the other side of the retardation film via the polarizing plate, the predetermined inspection region of the retardation film Telephoto imaging with the angle fluctuation in the imaging direction within the inspection area within 2 degrees,
An optical unevenness detection method for detecting a luminance fluctuation component from luminance information of a captured image obtained. An optical unevenness detection method according to claim 5,
An optical unevenness detection method in which the retardation film is imaged from a plurality of different directions, and a luminance variation component is detected from each captured image in each imaging direction. The optical unevenness detection method according to claim 5 or 6,
An optical unevenness detection method for imaging at least a 20 cm square region of the retardation film by one imaging. An optical unevenness detection method according to claim 5-6 or claim 7,
Inclining the retardation film in a representative imaging direction consisting of a plurality of specific directions, and imaging,
An optical for detecting the luminance unevenness component from the luminance information obtained from the luminance information obtained by the interpolation processing from the luminance value of the captured image in each representative imaging direction to obtain a luminance value with respect to an intermediate inclination direction of each representative imaging direction. Unevenness detection method. An optical unevenness detection method according to claim 8,
The transmission light screen of the illumination light observed at an arbitrary position facing the retardation film is synthesized from the luminance information obtained by the interpolation process, and the luminance information of the composite image of the transmission light screen An optical unevenness detecting method for detecting the luminance unevenness component from

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