Luminance unevenness correction system and luminance unevenness correction method

A luminance-unevenness correction system includes the following: an inspection backlight; an imaging device that generates imaged panel data by imaging a liquid-crystal display panel being illuminated with the inspection backlight; and a correction device that generates correction data and transmits the correction data to the liquid-crystal display panel. The correction data is used for correcting the luminance unevenness of the liquid-crystal display panel. The imaging device can generate backlight luminance-distribution data indicating the luminance distribution of the inspection backlight, by imaging the inspection backlight remaining on. The correction device extracts panel luminance-distribution data from the imaged panel data and the backlight luminance-distribution data, and generates the correction data in accordance with the panel luminance-distribution data extracted. The panel luminance-distribution data indicates luminance unevenness specific to the liquid-crystal display panel.

BACKGROUND

The present disclosure relates to a luminance-unevenness correction system that corrects the luminance unevenness of a liquid-crystal display panel, and to a method of such luminance-unevenness correction.

2. Description of the Related Art

A liquid-crystal display panel has been recently used widely for display units of various electronic apparatuses. Luminance unevenness (display unevenness) that occurs in an image displayed on the liquid-crystal display panel considerably affects display quality and hence needs to be corrected properly.

Luminance unevenness is conventionally corrected by taking an image displayed on the liquid-crystal display panel with a camera, and generating correction data in accordance with the taken image. The correction data is written into a storage device of the liquid-crystal display panel, and the correction data read from the storage device is used to correct image data. Such a method of luminance-unevenness correction is disclosed in Patent Literature 1 (JP-H7-261719) for instance.

SUMMARY

Some liquid-crystal display panels are distributed in combination with a backlight (referred to as a “module”), and others are distributed without a backlight (referred to as an “open cell”).

For correcting the luminance unevenness of an open-cell liquid-crystal display panel, the liquid-crystal display panel needs to be illuminated using an inspection backlight (jig backlight), because an open cell includes no backlight. The inspection backlight thus preferably has no luminance unevenness as much as possible, that is, luminance is preferably uniform as much as possible throughout its emission surface.

It is unfortunately difficult actually to prepare an inspection backlight without luminance unevenness. Luminance unevenness in an inspection backlight is caused by the luminance difference between light sources (such as cold-cathode tubes or LEDs) and a region located between the light sources, or by partial luminance reduction resulting from long-term use. In a direct-lit backlight, luminance uniformity can be improved by increasing the density of arrangement of the light sources, but this method increases facility costs. Luminance unevenness is also caused by replacement of some of the light sources due to light source exhaustion and other things. Replacing all the light sources of the backlight with new ones at the time of light source exhaustion and other things prevents luminance unevenness as a matter of course, but this method increases facility costs as well.

When the inspection backlight has luminance unevenness, luminance unevenness specific to the liquid-crystal display panel as well as luminance unevenness specific to the inspection backlight is reflected on an image taken by an imaging device. Correction data, generated from the taken image, hence has a value with which not only the luminance unevenness specific to the liquid-crystal display panel, but also the luminance unevenness specific to the inspection backlight is corrected. Referring to liquid-crystal display panels shipped as open cells, a final product is typically designed by a user in many cases, and hence it is difficult to obtain a backlight that is to be incorporated into the final product, or to know the specifications of the backlight. A backlight for the final product has luminance unevenness different from the luminance unevenness of the inspection backlight or has little luminance unevenness; hence, correcting luminance unevenness by the use of such correction data as described above (correction data for correcting both the luminance unevenness of the liquid-crystal display panel and the luminance unevenness of the inspection backlight) possibly leads to an excessive correction in the actual final product.

To solve the above problem, it is an object of preferred embodiments of the present invention to provide a luminance-unevenness correction system and a method of luminance-unevenness correction that can suitably correct the luminance unevenness of a liquid-crystal display panel that is distributed as an open cell.

The Specification discloses a luminance-unevenness correction system and a method of luminance-unevenness correction described in the following items.

A luminance-unevenness correction system that corrects luminance unevenness of a liquid-crystal display panel, the luminance-unevenness correction system including:

an inspection backlight;

an imaging device configured to generate imaged panel data by imaging the liquid-crystal display panel being illuminated by the inspection backlight; and

a correction device configured to generate correction data and then transmit the correction data to the liquid-crystal display panel, the correction data being used for correcting the luminance unevenness of the liquid-crystal display panel,

wherein the imaging device is capable of generating backlight luminance-distribution data indicating a luminance distribution of the inspection backlight, by imaging the inspection backlight remaining on, and

the correction device extracts panel luminance-distribution data from the imaged panel data and the backlight luminance-distribution data, and generates the correction data in accordance with the panel luminance-distribution data extracted, the panel luminance-distribution data indicating luminance unevenness specific to the liquid-crystal display panel.

The luminance-unevenness correction system according to Item 1, wherein the correction device identifies a first region and a second region in the imaged panel data in accordance with the backlight luminance-distribution data, and the correction device does not generate the correction data for the first region and generates the correction data for the second region, the first region having luminance unevenness specific to the inspection backlight, the second region having no luminance unevenness specific to the inspection backlight.

The luminance-unevenness correction system according to Item 1, wherein

the correction device identifies a first region and a second region in the imaged panel data in accordance with the backlight luminance-distribution data, the first region having luminance unevenness specific to the inspection backlight, the second region having no luminance unevenness specific to the inspection backlight,

a region of the panel luminance-distribution data having luminance unevenness specific to the liquid-crystal display panel includes an overlap portion overlapping the first region, and a non-overlap portion not overlapping the first region, and

the correction device calculates a luminance difference at a boundary between the overlap portion and the non-overlap portion, and adds or subtracts a value corresponding to the luminance difference to or from a luminance value of the overlap portion, followed by generating the correction data.

The luminance-unevenness correction system according to Item 1, wherein

the correction device identifies a first region and a second region in the imaged panel data in accordance with the backlight luminance-distribution data, the first region having luminance unevenness specific to the inspection backlight, the second region having no luminance unevenness specific to the inspection backlight,

a region of the panel luminance-distribution data having luminance unevenness specific to the liquid-crystal display panel includes an overlap portion overlapping the first region, and a non-overlap portion not overlapping the first region, and

the correction device generates the correction data, followed by calculating a correction value difference at a boundary between the overlap portion and the non-overlap portion, and adding or subtracting a value corresponding to the correction value difference to or from a correction value of the overlap portion.

The luminance-unevenness correction system according to any of Items 1 to 4, wherein the correction device extracts the panel luminance-distribution data by subtracting, from the imaged panel data, a luminance value of the backlight luminance-distribution data multiplied by a predetermined factor, or by subtracting the backlight luminance-distribution data from a luminance value of the imaged panel data multiplied by a predetermined factor.

The luminance-unevenness correction system according to any one of Items 1 to 5, wherein the correction device is capable of detecting an amount of shift between origin point coordinates of the backlight luminance-distribution data and origin point coordinates of the imaged panel data.

The luminance-unevenness correction system according to Item 6, wherein the correction device detects the amount of shift, by identifying a location that is regarded as a location identical between the backlight luminance-distribution data and the imaged panel data in accordance with a luminance value and a shape of a region having luminance unevenness in the backlight luminance-distribution data, and in accordance with a luminance value and a shape of a region having luminance unevenness in the imaged panel data.

The luminance-unevenness correction system according to Item 6, further including

a spot-light radiation device capable of radiating at least one spot light,

wherein the correction device detects the amount of shift in accordance with the backlight luminance-distribution data generated with a particular part of an emission surface of the inspection backlight irradiated with the at least one spot light, and in accordance with the imaged panel data generated with a particular part of a display surface of the liquid-crystal display panel irradiated with the at least one spot light.

The luminance-unevenness correction system according to Item 6, wherein

the inspection backlight has a housing including a frame part located around an emission surface, and one or more emission units disposed in the frame part of the housing, and each being capable of emitting spot light, and

the correction device detects the amount of shift in accordance with the backlight luminance-distribution data generated with the one or more emission units emitting spot light, and in accordance with the imaged panel data generated with the one or more emission units emitting spot light.

A method of luminance-unevenness correction for correcting luminance unevenness of a liquid-crystal display panel, the method including:

step (A) of generating backlight luminance-distribution data indicating a luminance distribution of an inspection backlight, by imaging the inspection backlight remaining on;

step (B) of generating imaged panel data by imaging the liquid-crystal display panel being illuminated by the inspection backlight;

step (C) of extracting panel luminance-distribution data indicating luminance unevenness specific to the liquid-crystal display panel, from the imaged panel data and the backlight luminance-distribution data; and

step (D) of generating correction data in accordance with the panel luminance-distribution data and then transmitting the correction data to the liquid-crystal display panel, the correction data being used for correcting the luminance unevenness of the liquid-crystal display panel.

The method of luminance-unevenness correction according to Item 10, wherein

a set of steps (A), (B), (C) and (D) is executed for each of liquid-crystal display panels that are targets of correction, and

the method further comprises step (E) of, after step (A) for second and subsequent times is executed, comparing the backlight luminance-distribution data generated anew and the backlight luminance-distribution data generated last time or before.

The method of luminance-unevenness correction according to Item 10 or 11, wherein

a set of steps (A), (B), (C) and (D) is executed for each of liquid-crystal display panels that are targets of correction, and

the method further comprises step (F) of, after step (B) for second and subsequent times is executed, comparing the imaged panel data generated anew and the imaged panel data generated last time or before.

The method of luminance-unevenness correction according to any one of Items 10 to 12, further including step (G) of, after step (A) is executed, comparing a luminance value of an emission surface in the backlight luminance-distribution data generated and a luminance value established in advance for a production model.

The preferred embodiments of the present invention can provide a luminance-unevenness correction system and a method of luminance-unevenness correction that can suitably correct luminance unevenness in a liquid-crystal display panel that is distributed as an open cell.

DETAILED DESCRIPTION OF THE INVENTION

Preferred embodiments of the present invention will be described with reference to the drawings. The preferred embodiments of the present invention are not limited to the following illustrative configurations.

First Preferred Embodiment

A luminance-unevenness correction system (hereinafter, referred merely to as a “correction system”)100and a method of luminance-unevenness correction in this preferred embodiment will be described with reference toFIG.1.FIG.1is a schematic diagram of the correction system100.

The correction system100is a system that corrects the luminance unevenness of the liquid-crystal display panel1. The correction system100can make corrections sequentially to a plurality of liquid-crystal display panels1.

The correction system100includes an inspection backlight10, an imaging device20, and a correction device30, as illustrated inFIG.1. The correction system100in the illustrated example further includes a signal source40and a panel control circuit50.

The liquid-crystal display panel1, a target of correction, is an open-cell panel. The liquid-crystal display panel1is configured such that its image display is controlled by the panel control circuit50from outside. The liquid-crystal display panel1has a storage device2. The storage device2is a non-volatile storage device, such as flash memory, for instance.

The inspection backlight10is an illumination device that illuminates the display region of the liquid-crystal display panel1. The configuration of the inspection backlight10is non-limiting; the inspection backlight10may be a direct-lit type or an edge-lit type. The light source of the inspection backlight10is non-limiting; for instance, the light source may be a cold-cathode tube (fluorescent tube) or a light-emitting diode (LED).

The imaging device (camera)20generates imaged panel data by imaging the liquid-crystal display panel1being illuminated by the inspection backlight10. The imaged panel data indicates the luminance distribution of the liquid-crystal display panel1being illuminated by the inspection backlight10. The imaging device20has an imaging element and an optical system. Examples of the imaging element include a CCD image sensor and a CMOS image sensor. Examples of the optical system include, but not limited to, a zoom lens and a focus lens. The operation of the imaging device20is controlled by the correction device30. The imaged panel data generated is output to the correction device30.

The signal source40is a signal generation circuit that generates an image signal corresponding to an image displayed by the liquid-crystal display panel1. The signal source40outputs the generated image signal to the panel control circuit50. The operation of the signal source40is controlled by the correction device30.

The correction device30controls the operation of the imaging device20and signal source40. The correction device30also generates correction data, which is used for correcting the luminance unevenness of the liquid-crystal display panel1, and then transmits the correction data to the liquid-crystal display panel1. The correction data contains a correction value that is to be added to the gradation value of each pixel. The correction data transmitted to the liquid-crystal display panel1is written into the storage device2of the liquid-crystal display panel1. The correction device30is a personal computer for instance.

The panel control circuit50is a dedicated circuit for controlling the image display of the liquid-crystal display panel1from outside. The panel control circuit50is connected between the signal source40and the liquid-crystal display panel1of a target of correction, and based on the image signal from the signal source40, the panel control circuit50controls the image display of the liquid-crystal display panel1.

In the correction system100in this preferred embodiment, the imaging device20can generate backlight luminance-distribution data, which indicates the luminance distribution of the inspection backlight10, by imaging the inspection backlight10remaining on. The imaging device20is controlled to generate the backlight luminance-distribution data as well as the imaged panel data in this way.

The correction device30extracts panel luminance-distribution data, which indicates luminance unevenness specific to the liquid-crystal display panel1, from the imaged panel data and backlight luminance-distribution data. To be specific, the panel luminance-distribution data is extracted by performing a predetermined data process including a subtraction process on the imaged panel data and backlight luminance-distribution data. The correction device30generates correction data in accordance with the extracted panel luminance-distribution data.

The correction device30in this preferred embodiment generates the correction data in accordance with the panel luminance-distribution data, indicating the luminance unevenness specific to the liquid-crystal display panel1, as described above, thereby enabling correction making without the influence of the luminance unevenness specific to the inspection backlight10.

The operation (also referred to as a method of luminance-unevenness correction) of the correction system100in this preferred embodiment and an effect of the correction system100will be described anew in comparison with a correction system (method of correction) in a comparative example.FIG.2illustrates, on the left side, the luminance unevenness specific to the inspection backlight10, by way of example and illustrates, on the right side, the luminance unevenness specific to the liquid-crystal display panel1, by way of example. The inspection backlight10shown on the left side ofFIG.2has a housing11including a frame part, which is located around an emission surface10a. In the example shown on the left side ofFIG.2, a slightly dark region in strip form extends in the up-and-down direction on the left side of the emission surface10a. In the example shown on the right side ofFIG.2, an elliptic dark region exists on the slightly lower right side of a display surface1aof the liquid-crystal display panel1. The following describes, as an example, an instance where the inspection backlight10and the liquid-crystal display panel1have the luminance unevenness shown inFIG.2.

FIG.3illustrates how the luminance unevenness of the liquid-crystal display panel1is corrected using a correction system900in a comparative example. Like the correction system100shown inFIG.1, the correction system900in the comparative example includes the inspection backlight10, the imaging device20, a correction device930, the signal source40, and the panel control circuit50. In the correction system900in the comparative example however, the imaging device20generates imaged panel data, but does not generate backlight luminance-distribution data. The correction device930thus does not extract panel luminance-distribution data.

In the correction system900in the comparative example, the imaging device20firstly images the liquid-crystal display panel1being illuminated by the inspection backlight10, as illustrated on the left side ofFIG.3. This generates imaged panel data, as illustrated at the top on the right side ofFIG.3. The imaged panel data has the luminance unevenness specific to the inspection backlight10in addition to luminance unevenness specific to the liquid-crystal display panel1. The correction device930next generates correction data in accordance with the imaged panel data, as illustrated at the second stage from the top on the right side ofFIG.3. Not only the luminance unevenness specific to the liquid-crystal display panel1, but also the luminance unevenness specific to the inspection backlight10is reflected on the correction data. The correction data is then written into the storage device2of the liquid-crystal display panel1, and a correction is thereafter made based on the correction data. The luminance unevenness seems to have been improved in a post-correction display (display under illumination by the inspection backlight10), as illustrated at the third stage on the right side ofFIG.3. Once the liquid-crystal display panel1is actually incorporated in a module however, the luminance unevenness specific to the inspection backlight10undergoes an excessive correction, and thus the luminance unevenness seems to have not been improved, as illustrated at the bottom on the right side ofFIG.3, because the module's backlight has luminance unevenness different from that of the inspection backlight10or little has luminance unevenness.

FIG.4andFIG.5schematically illustrate how the luminance unevenness of the liquid-crystal display panel1is corrected using the correction system100in this preferred embodiment.FIG.6andFIG.7are flowcharts each showing a method of correcting luminance unevenness using the correction system100.

In the correction system100in this preferred embodiment, the imaging device20firstly images the inspection backlight10remaining on (this process step is Step s1), as shown on the left side ofFIG.4, thus generating backlight luminance-distribution data (this process step is Step s2), as illustrated on the right side ofFIG.4. The backlight luminance-distribution data has luminance unevenness specific to the inspection backlight10. The liquid-crystal display panel1is then set in front of the inspection backlight10(this process step is Step s3). The imaging device20next images the liquid-crystal display panel1being illuminated by the inspection backlight10(this process step is Step s4), as illustrated at the upper stage on the left side ofFIG.5, thus generating imaged panel data (this process step is Step s5), as illustrated at the top on the right side ofFIG.5. The imaged panel data has the luminance unevenness specific to the inspection backlight10in addition to luminance unevenness specific to the liquid-crystal display panel1.

The correction device30next performs a subtraction process on the imaged panel data and backlight luminance-distribution data (this process step is Step s6), as illustrated at the second stage from the top on the right side ofFIG.5, thus extracting panel luminance-distribution data (this process step is Step s7). In the present disclosure, the subtraction process is a process of subtracting the luminance values of the corresponding pixels between the imaged panel data and the backlight luminance-distribution data. Specifically, the luminance unevenness specific to the inspection backlight is removed from the imaged panel data by subtracting the luminance value of the backlight luminance-distribution data from the luminance value of the imaged panel data (a predetermined coefficient may be multiplied by the luminance value when subtracting the luminance value.). The panel luminance-distribution data is obtained by the above process. The panel luminance-distribution data indicates the luminance unevenness specific to the liquid-crystal display panel1. The correction device30next generates correction data in accordance with the panel luminance-distribution data (this process step is Step s8), as illustrated at the third stage from the top on the right side ofFIG.5. Although the luminance unevenness specific to the liquid-crystal display panel1is reflected on the correction data, the luminance unevenness specific to the inspection backlight10is not reflected on the correction data.

The correction data is then written into the storage device2of the liquid-crystal display panel1(this process step is Step s9), and thereafter, the liquid-crystal display panel1is removed from the front of the inspection backlight10(this process step is Step s10). The next is determining whether all of plural the liquid-crystal display panels1to be processed have been through with all the process steps (this process step is Step s11). If YES, the luminance-unevenness correction is ended. If NO, the liquid-crystal display panel1that is a next target undergoes Steps s3through s11again.

The liquid-crystal display panel1after reset undergoes a correction based on the correction data. In a post-correction display (display under illumination by the inspection backlight10), although the luminance unevenness specific to the liquid-crystal display panel1has been improved, the luminance unevenness specific to the inspection backlight10has not been improved, and hence, the luminance unevenness as a whole seems to have not been improved, as illustrated at the bottom on the right side ofFIG.5. Once the liquid-crystal display panel1is actually incorporated in a module however, the luminance unevenness as a whole seems to have been improved, as illustrated at the lower stage on the left side ofFIG.5, because an excessive correction (this results from a correction made to the luminance unevenness specific to the inspection backlight10) is not made.

The correction system100in this preferred embodiment can correct the luminance unevenness of each liquid-crystal display panel1without the influence of the luminance unevenness specific to the inspection backlight10.

The correction device30in this preferred embodiment generates the correction data for a region having no luminance unevenness specific to the inspection backlight10, but the correction device30does not generate the correction data for a region having luminance unevenness specific to the inspection backlight10. To be specific, based on the backlight luminance-distribution data, the correction device30identifies (see the top on the right side ofFIG.5), in the imaged panel data, a region R1having luminance unevenness specific to the inspection backlight10(hereinafter, referred to as a “first region”), and a region R2having no luminance unevenness specific to the inspection backlight10(hereinafter, referred to as a “second region”), and the correction device30does not generate the correction data for the first region R1and generates the correction data for the second region R2.

The first region R1can be identified in the following manner specifically.

For instance, a region that is defined by a boundary line obtained by connecting points of change in luminance value (pixels with the luminance value difference between each of the pixels and its adjacent pixel being equal to or greater than a predetermined value) together, can be identified as the first region R1. Alternatively, a region in which the luminance difference between the luminance value in each position and a reference luminance value, which is the luminance in the middle of the emission surface10aof the inspection backlight10, exceeds an established threshold, may be identified as the first region R1. Alternatively, a region in which the luminance difference between the mean value of the luminance of the emission surface10aand the luminance value in each position exceeds a threshold, may be identified as the first region R1. Alternatively, a region in which the luminance difference between the maximum value of the luminance of the emission surface10aand the luminance value in each position exceeds a threshold, may be identified as the first region R1; alternatively, a region in which the luminance difference between the mode value of the luminance of the emission surface10aand the luminance value in each position exceeds a threshold, may be identified as the first region R1.

The timing for imaging the inspection backlight10can be selected from, but not limited to, (1) every time, (2) at the time of work start and at the time of model change, (3) at the time of periodic checkups, and (4) at the time of component (such as a light source) replacement. The inspection backlight10, which can undergo imaging during replacement of the liquid-crystal display panel1, can undergo imaging without affecting processing time.

Second Preferred Embodiment

In this preferred embodiment, correction data is generated not only for a region (second region) having no luminance unevenness specific to the inspection backlight10, but also for a region (first region) having luminance unevenness specific to the inspection backlight10. This preferred embodiment describes, as an example, an instance where the inspection backlight10and the liquid-crystal display panel1have the luminance unevenness shown inFIG.8. In the example shown on the left side ofFIG.8, a slightly dark region in strip form extends in the up-and-down direction on the left side of the emission surface10aof the inspection backlight10. In the example shown on the right side ofFIG.8, an elliptic dark region exists on the lower left side of the display surface1aof the liquid-crystal display panel1.

FIG.9AtoFIG.9Eschematically illustrate how the luminance unevenness of the liquid-crystal display panel1is corrected in an aspect of this preferred embodiment.

Like that in the first embodiment, the imaging device20firstly images the inspection backlight10remaining on, thus generating backlight luminance-distribution data. The backlight luminance-distribution data has luminance unevenness specific to the inspection backlight10.

The imaging device20next images the liquid-crystal display panel1being illuminated by the inspection backlight10, as illustrated inFIG.9A. This generates imaged panel data, as illustrated inFIG.9B. The imaged panel data has the luminance unevenness specific to the inspection backlight10in addition to luminance unevenness specific to the liquid-crystal display panel1. Based on the backlight luminance-distribution data, the correction device30can identify, in the imaged panel data, the first region R1, which has luminance unevenness specific to the inspection backlight10, and the second region R2, which has no luminance unevenness specific to the inspection backlight10. In the example shown inFIG.9B, a region having luminance unevenness specific to the liquid-crystal display panel1includes an overlap portion A overlapping the first region R1, and a non-overlap portion not overlapping the first region R1. The overlap portion A is darker than the non-overlap portion B in the example illustrated herein.

The correction device30next extracts panel luminance-distribution data from the imaged panel data and backlight luminance-distribution data, as illustrated on the left side ofFIG.9C. The panel luminance-distribution data indicates the luminance unevenness specific to the liquid-crystal display panel1. To be specific, the panel luminance-distribution data is extracted by performing a predetermined data process including a subtraction process on the imaged panel data and backlight luminance-distribution data.

The surface luminance of the inspection backlight10is typically about 10 to 20 times greater than the surface luminance of the liquid-crystal display panel1; hence, the subtraction process is preferably performed after luminance value interpolation is performed. To be specific, the correction device30preferably extracts the panel luminance-distribution data by subtracting, from the imaged panel data, a luminance value of the backlight luminance-distribution data multiplied by a predetermined factor, or by subtracting the backlight luminance-distribution data from a luminance value of the imaged panel data multiplied by a predetermined factor. Each predetermined factor is calculated based, for instance, on the transmittancy of the liquid-crystal display panel1, and the gradation (gradation of a test image) of the display surface1aat the time of luminance-unevenness correction.

Since this process uses a predetermined factor, it is conceivable that the luminance at the boundary between the overlap portion A and non-overlap portion B does not match in the panel luminance-distribution data. The correction device30herein calculates a luminance difference at the boundary between the overlap portion A and non-overlap portion B and adds, to the luminance value of the overlap portion A, a value corresponding to the luminance difference (this process is hereinafter referred to as a “luminance difference process”), as illustrated on the right side ofFIG.9C. This can reduce the luminance difference between the overlap portion A and non-overlap portion B.

The correction device30next generates correction data in accordance with the panel luminance-distribution data, as illustrated inFIG.9D. Although the luminance unevenness specific to the liquid-crystal display panel1is reflected on the correction data, the luminance unevenness specific to the inspection backlight10is not reflected on the correction data.

The correction data is then written into the storage device2of the liquid-crystal display panel1, and a correction is thereafter made based on the correction data. In a post-correction display, although the luminance unevenness specific to the liquid-crystal display panel1has been improved, the luminance unevenness specific to the inspection backlight10has not been improved, and hence, the luminance unevenness as a whole seems to have not been improved, as illustrated on the left side ofFIG.9E. Once the liquid-crystal display panel1is actually incorporated in a module however, the luminance unevenness as a whole seems to have been improved, as illustrated on the right side ofFIG.9E, because an excessive correction (this results from a correction made to the luminance unevenness specific to the inspection backlight10) is not made.

This preferred embodiment enables an accurate correction to be made for also a region having luminance unevenness specific to the inspection backlight10.

Although the foregoing has described an instance where the overlap portion A is darker than the non-overlap portion B, the overlap portion A is brighter than the non-overlap portion B in some cases. In these cases, the luminance difference between the overlap portion A and non-overlap portion B can be reduced by subtracting, from the luminance value of the overlap portion A, a value corresponding to the luminance difference at the boundary between the overlap portion A and non-overlap portion B.

Alternatively, the correction data after generation may undergo a process to reduce the luminance difference between the overlap region A and non-overlap region B, instead of the foregoing luminance difference process in the panel luminance-distribution data. To be specific, the correction device30may generate the correction data, followed by calculating a correction value difference at the boundary between the overlap portion A and non-overlap portion B and adding (when the overlap portion A is darker than the non-overlap portion B) or subtracting (when the overlap portion A is brighter than the non-overlap portion B) a value corresponding to the correction value difference to or from a correction value of the overlap portion A.

Instead of luminance value interpolation, the luminance of the backlight luminance-distribution data may be regulated by any of means (1) to (4) listed below.

(1) Use an ND filter when imaging the inspection backlight10.

(2) Perform imaging while keeping the luminance of the inspection backlight10low.

(3) Regulate exposure time in imaging the inspection backlight10.

(4) Perform imaging with the liquid-crystal display panel1having substantially no luminance unevenness placed in front of the inspection backlight10.

Third Preferred Embodiment

Possible ways of setting the liquid-crystal display panel1in front of the inspection15backlight10include automatic supply by the use of a panel transport facility, and an operator's manual operation. The inspection backlight10and the imaging device20are fastened at their respective predetermined positions, and hence no positional shift in origin point coordinates occurs in imaging the inspection backlight10. It is conceivable however that the origin point coordinates possibly shift every time the liquid-crystal display panel1undergoes imaging, depending on the operation accuracy of the panel transport facility or the operation accuracy of the operator.

FIG.10illustrates the position of an origin point O1in the inspection backlight10, and the position of an origin point O2in the liquid-crystal display panel1. In the example shown on the left side ofFIG.10, the origin point O1in the inspection backlight10is at the upper-left corner of the emission surface10a. In the example shown on the right side ofFIG.10, the origin point O2in the liquid-crystal display panel1is at the upper-left corner of the display surface1adefined by a black matrix1b.

No shift occurs between the origin point coordinates of backlight luminance-distribution data and the origin point coordinates of imaged panel data, as illustrated on the right side ofFIG.11, when the liquid-crystal display panel1is set without deviation, as illustrated on the left side ofFIG.11, that is, when there is no positional shift between the origin point O1in the inspection backlight10and the origin point O2in the liquid-crystal display panel1. These data pieces may hence undergo processing as they are.

In contrast to this, a shift occurs between the origin point coordinates of the backlight luminance-distribution data and the origin point coordinates of the imaged panel data (herein, an instance is provided where a side-to-side shift occurs with a shift amount a), as illustrated on the right side ofFIG.12, when the liquid-crystal display panel1is mispositioned, as illustrated on the left side ofFIG.12, that is, when there is a positional shift between the origin point O1in the inspection backlight10and the origin point O2in the liquid-crystal display panel1. These data pieces cannot hence undergo processing properly as they are.

The correction device30in this preferred embodiment can detect the amount of shift between the origin point coordinates of the backlight luminance-distribution data and the origin point coordinates of the imaged panel data. To be specific, the amount of shift can be detected by any of three aspects listed below.

First Aspect

The correction device30in this aspect detects the amount of shift, by identifying a location that is regarded as a location identical between the backlight luminance-distribution data and imaged panel data in accordance with the luminance value and shape of a region having luminance unevenness in the backlight luminance-distribution data, and in accordance with the luminance value and shape of a region having luminance unevenness in the imaged panel data.

The inspection backlight10and the imaging device20are fastened at their predetermined positions, as earlier described, and thus the position of the origin point coordinates of the backlight luminance-distribution data is the same every time without change. Accordingly, the amount of shift between the origin point coordinates of the backlight luminance-distribution data and the origin point coordinates of the imaged panel data can be detected, by identifying a location that is regarded as a location identical between the backlight luminance-distribution data and imaged panel data in accordance with the luminance value and shape of a region having luminance unevenness in the backlight luminance-distribution data, and in accordance with the luminance value and shape of a region having luminance unevenness in the imaged panel data.

Second Aspect

The correction system100in this aspect further includes a spot-light radiation device that can radiate at least one spot light. The spot-light radiation device includes four laser pointers60for instance, as illustrated inFIG.13AandFIG.13B.

In this aspect, the inspection backlight10undergoes imaging with a particular part of the emission surface10aof the inspection backlight10irradiated with at least one spot light. To be specific, the imaging is performed with the emission surface10a, near its four corners, irradiated with spot light, as illustrated inFIG.13A. The inspection backlight10then undergoes imaging with the emission surface10anot irradiated with spot light.

The liquid-crystal display panel1is subsequently set, and thereafter the liquid-crystal display panel1undergoes imaging with a particular part of the display surface1aof the liquid-crystal display panel1irradiated with at least one spot light. To be specific, the imaging is performed with the display surface1a, near its four corners, irradiated with spot light, as illustrated inFIG.13B. The liquid-crystal display panel1then undergoes imaging with the display surface1anot irradiated with spot light. Herein, the position of the spot-light radiation device and the direction of spot light are the same between the imagining of the inspection backlight10under spot light irradiation and the imaging of the liquid-crystal display panel1under spot light irradiation.

The correction device30thereafter detects the amount of shift between the origin point coordinates of the backlight luminance-distribution data and the origin point coordinates of the imaged panel data, by calculating the amount of coordinate shift between the part irradiated with spot light in the backlight luminance-distribution data and the part irradiated with spot light in the imaged panel data in accordance with the backlight luminance-distribution data generated under spot light irradiation, and in accordance with the imaged panel data generated under spot light irradiation.

Where the emission surface10aand the display surface1aundergo spot light irradiation are not limited to the examples shown inFIG.13AandFIG.13B. Furthermore, the number of spot lights is not limited to four, which is illustrated inFIG.13AandFIG.13Bby way of example; three or less spot lights or five or more spot lights may be radiated. A plurality of spot lights do not necessarily have to be radiated; one spot light may be radiated. Here, let the horizontal direction of the display surface of the liquid-crystal display panel1be defined as an X-direction, let the vertical direction of the display surface of the liquid-crystal display panel1be defined as a Y-direction, and let a rotation direction within the display surface be defined as a θ-direction. For a plurality of spot lights, the amount of shift can be detected for each of the X-direction, Y-direction and θ-direction. No shift occurs in one of the X-direction and Y-direction as well as in the θ-direction when one (extending in the X-direction or Y-direction) of the sides of the liquid-crystal display panel1can be fastened by a positioning mechanism or other things; hence, the amount of shift in the remaining direction (the other one of the X-direction and Y-direction) can be detected even when there is one spot light.

Third Aspect

The inspection backlight10in this aspect has one or more emission units12disposed in the frame part of the housing11, as illustrated inFIG.14AandFIG.14B. The one or more emission units12can each emit spot light. In the examples shown inFIG.14AandFIG.14B, four emission units12arm disposed near the four corners of the emission surface10a.

In this aspect, the inspection backlight10firstly undergoes imaging with the one or more emission units12emitting spot light, as illustrated inFIG.14A. The inspection backlight10then undergoes imaging with the one or more emission units12not emitting spot light.

The liquid-crystal display panel1is subsequently set, and thereafter the liquid-crystal display panel1undergoes imaging with the one or more emission units12emitting spot light, as illustrated inFIG.14B. The liquid-crystal display panel1then undergoes imaging with the one or more emission units12not emitting spot light.

The correction device30then detects the amount of shift between the origin point coordinates of the backlight luminance-distribution data and the origin point coordinates of the imaged panel data in accordance with the backlight luminance-distribution data generated with the emission units12emitting spot light, and in accordance with the imaged panel data generated with the emission units12emitting spot light.

As such, this preferred embodiment enables correction data to be generated by reflecting a shift between the origin point coordinates of the backlight luminance-distribution data and the origin point coordinates of the imaged panel data, even if the liquid-crystal display panel1is mispositioned. For instance, a subtraction process between the imaged panel data and backlight luminance-distribution data can be performed with the position of the origin point O1in the inspection backlight10and the position of the origin point O2in the liquid-crystal display panel1coinciding. This can prevent quality degradation in luminance-unevenness correction resulting from mispositioning of the liquid-crystal display panel1.

Like the number of spot lights, the number of emission units12is not limit to four illustrated inFIG.14AandFIG.14Bby ways of example; three or less emission units12or five or more emission units12may be provided. A plurality of emission units12do not necessarily have to be provided; one emission unit12may be provided.

Fourth Preferred Embodiment

A method of luminance-unevenness correction in this preferred embodiment will be described. In the method of luminance-unevenness correction in this preferred embodiment, the correction system100can undergo maintenance using backlight luminance-distribution data, as described later on. That is, the method of luminance-unevenness correction in this preferred embodiment can be regarded as a method of performing maintenance on the correction system100.

FIG.15is a flowchart showing the method of luminance-unevenness correction in this preferred embodiment.

The inspection backlight10remaining on firstly undergoes imaging (this process step is Step s1), thus generating backlight luminance-distribution data (this process step is Step s2). The liquid-crystal display panel1is then set in front of the inspection backlight10(this process step is Step s3). The liquid-crystal display panel1being illuminated by the inspection backlight10undergoes imaging (this process step is Step s4), thus generating imaged panel data (this process step is Step s5).

The next is performing a subtraction process between the imaged panel data and backlight luminance-distribution data (this process step is Step s6), thus extracting panel luminance-distribution data (this process step is Step s7). The next is generating correction data in accordance with the panel luminance-distribution data (this process step is Step s8), followed by transmitting the correction data to the liquid-crystal display panel1to write the correction data into the storage device2(this process step is Step s9).

The liquid-crystal display panel1is then removed from the front of the inspection backlight10(this process step is Step s10). The next is determining whether the liquid-crystal display panel1has been through with all the process steps (this process step is Step s11). If YES, the luminance-unevenness correction is ended. If NO, the liquid-crystal display panel1that is a next target undergoes Steps s1through s11again.

A process step (Steps s1and s2) in which the imaging device20images the inspection backlight10to generate backlight luminance-distribution data is thus executed a plurality of times. After Steps s1and s2for the second and subsequent times are executed, the next is comparing (this process step is Step s12), for an abnormality, the backlight luminance-distribution data generated anew and the backlight luminance-distribution data generated last time or before (that is, the backlight luminance-distribution data obtained already). If no abnormality is found, the process proceeds to the next step (Step s3). If an abnormality is found, an alarm is issued (this process step is Step s13).

A process step (Steps s4and s5) in which the imaging device20images the liquid-crystal display panel1to generate imaged panel data is executed a plurality of times as well. After Steps s4and s5for the second and subsequent times are executed, the next is comparing (this process step is Step s14), for an abnormality, the imaged panel data generated anew and the imaged panel data generated last time or before (that is, the imaged panel data obtained already). If no abnormality is found, the process proceeds to the next step (Step s6). If an abnormality is found, an alarm is issued (this process step is Step s15).

FIG.16is a more detailed flowchart showing the method of luminance-unevenness correction in this preferred embodiment.

In the example shown inFIG.16, in the step (Step s12) of comparing the backlight luminance-distribution data generated anew and the backlight luminance-distribution data obtained already, the first process step (Step s12a) is determining whether the origin point position of the emission surface10ais the same between both data pieces or is shifted between both data pieces by a value equal to or smaller than a predetermined threshold. If the amount of positional shift in the origin point of the emission surface10aexceeds the threshold (if an abnormality is found), an alarm is issued (this process step is Step s13).

If the origin point position of the emission surface10ais the same, or the amount of positional shift is equal to or smaller than the threshold (if no abnormality is found), the next is determining whether the shape of the luminance unevenness of the emission surface10ais the same between both data pieces (this process step is Step s12b). If the shape of the luminance unevenness is different (if an abnormality is found), an alarm is issued (this process step is Step s13).

If the shape of the luminance unevenness is the same (if no abnormality is found), the next is determining whether the luminance value of the emission surface10ais the same between both data pieces or is different between both data pieces by a value equal to or smaller than a predetermined threshold (this process step is Step s12c). If the amount of difference in the luminance value of the emission surface10aexceeds the threshold (if an abnormality is found), an alarm is issued (this process step is Step s13).

If the luminance value of the emission surface10ais the same or the amount of difference is equal to or smaller than the threshold (if no abnormality is found), the next is comparing the luminance value of the emission surface10ain the backlight luminance-distribution data generated anew and a luminance value established in advance for a production model (this process step is Step s12′). To be specific, Step s12a′ is determining whether the luminance value established for the production model and the luminance value of the emission surface10aare the same or are different by a value equal to or smaller a predetermined threshold. If the amount of difference between the luminance value established for the production model and the luminance value of the emission surface10aexceeds the threshold (if an abnormality is found), an alarm is issued (this process step is Step s13). If the luminance value established for the production model and the luminance value of the emission surface10aare the same or are different by a value equal to or smaller than the threshold (if no abnormality is found), the process proceeds to the next step (Step s3).

The “luminance value of the emission surface10a” in Step s12cand Step s12′ may be, for instance, the luminance value in the middle of the emission surface10a, or the mean value of the luminance of the emission surface10a. Alternatively, the “luminance value of the emission surface10a” may be the maximum value of the luminance of the emission surface10a, or the mode value of the luminance of the emission surface10a.

In the example shown inFIG.16, the step (Step s14) of comparing the imaged panel data generated anew and the imaged panel data obtained already includes, specifically, determining whether the origin point position of the liquid-crystal display panel1is the same between both data pieces or is shifted between both data pieces by a value equal to or smaller than a predetermined threshold (this process step is Step s14a). If the amount of positional shift in the origin point of the liquid-crystal display panel1exceeds the threshold (if an abnormality is found), an alarm is issued (this process step is Step s15). If the origin point position of the liquid-crystal display panel1is the same, or the amount of positional shift is equal to or smaller than the threshold (if no abnormality is found), the process proceeds to the next step (Step s6).

The foregoing method of correction enables such maintenance as listed in (1) to (5) for instance.

(1) The inspection backlight10and the imaging device20are in their fixed positions; hence, the position of the origin point of the emission surface10aand the position of a reference point of the emission surface10ado not change. Consequently, a change in luminance value at these points enables early detection of a facility backlash and other things. This maintenance can be implemented by, for instance, the foregoing determination in Step s12a.

(2) The repetition accuracy of a mechanism for setting the liquid-crystal display panel1and the amount of shift can be monitored. This maintenance can be implemented by, for instance, the foregoing determination in Step s14a.

(3) A change in the shape of the luminance unevenness of the emission surface10aof the inspection backlight10or a change in the luminance value of the emission surface10aenables monitoring of changes in the light volume of the light source. This maintenance can be implemented by, for instance, the foregoing determinations in Steps s12band s12c.

(4) Physical dirt, a physical flaw and other things on the surface of the inspection backlight10can be detected. This maintenance can be implemented by, for instance, the foregoing determinations in Steps s12band s12c.

(5) A failure of a necessary change in the luminance value of the inspection backlight10and other things can be prevented. Such a change is necessary as a result of a model change or other things. This maintenance can be implemented by, for instance, the foregoing determination in Step s12a′.

As described above, the method of luminance-unevenness correction in this preferred embodiment enables an abnormality in the inspection backlight10to be detected early.

The preferred embodiments of the present invention can provide a luminance-unevenness correction system and a method of luminance-unevenness correction that can suitably correct luminance unevenness in a liquid-crystal display panel that is distributed as an open cell. The luminance-unevenness correction system and the method of luminance-unevenness correction according to the preferred embodiments of the present invention can be widely used for luminance-unevenness correction in various liquid-crystal display panels.