Tri-color LED groups spaced for optimal color mixing

A light source apparatus includes a plurality of light source groups, wherein each light source group has: a plurality of first light sources configured to emit light of a first color; a plurality of second light sources configured to emit light of a second color; and a plurality of third light sources configured to emit light of a third color, and a distance between the plurality of second light sources of the same light source group and a distance between the plurality of third light sources of the same light source group are each shorter than a minimum value of a distance between the plurality of first light sources of the same light source group.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national phase application of International Application No. PCT/JP2015/005201 filed on Oct. 14, 2015, the entire disclosure of which is hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to a light source apparatus and an image display apparatus.

BACKGROUND ART

Cold-cathode fluorescent lamps (CCFL) have been traditionally used as light sources for backlight apparatuses of liquid crystal display apparatuses, but the number of backlight apparatuses using light-emitting diodes (LEDs) as light sources has recently also increased. Since an LED is a spot light source, when LEDs are used as the light sources of a backlight apparatus, the occurrence of brightness unevenness and color unevenness of the light emitted from the backlight apparatus needs to be suppressed by devising the arrangement of LEDs, a light diffusion structure, and a light reflection structure. In particular, in a backlight apparatus using LEDs of a plurality of colors, such as red color, green color, and blue color, brightness unevenness and color unevenness in the form of a stripe or grid pattern occur easier than in the backlight apparatuses using white-color LEDs. Therefore, the arrangement of LEDs, light diffusion structure, and light reflection structure need to be devised.

For example, Patent Literatures 1 to 3 disclose techniques for reducing color unevenness in a backlight apparatus (light source apparatus) using LEDs of three colors: red, green, and blue. Thus, Patent Literatures 1 to 3 disclose light source apparatuses having a plurality of light-emitting clusters.

In the light source apparatus disclosed in Patent Literature 1, light-emitting clusters of a plurality of types are used. In the light-emitting clusters disclosed in Patent Literature 1, the three LEDs have triangular arrangements, and the arrangements of red LEDs differ among the light-emitting clusters of a plurality of types. In the light source apparatus disclosed in Patent Literature 1, the types of the light-emitting clusters which are to be arranged are changed according to the arrangement positions of the light-emitting clusters.

In the light source apparatus disclosed in Patent Literature 2, light-emitting clusters are used which have a plurality of light-emitting elements that differ in color (emission color; the color of light emitted from a light-emitting element) from each other. With respect to at least one color, the light-emitting cluster disclosed in Patent Literature 2 has a plurality of light-emitting elements of this color. Further, in the light-emitting cluster disclosed in Patent Literature 2, the light-emitting elements are arranged such that the central positions of the light-emitting element of each color substantially match.

In the light source apparatus disclosed in Patent Literature 3, light-emitting clusters are used that have N spot light sources that differ in color. Further, in the light source apparatus disclosed in Patent Literature 3, each light-emitting cluster is arranged by being rotated clockwise or counterclockwise through a predetermined angle with respect to a light-emitting cluster adjacent to this light-emitting cluster.

Further, a technique is known by which the emission brightness of LEDs is individually changed by using the fact that LEDs are spot light sources, thereby changing partially the luminance of the backlight apparatus and increasing the contrast of the displayed image. Such control of emission brightness is typically called local dimming control. The local dimming control involves the processing of analyzing a brightness value of an image signal with respect to each of a plurality of divided regions constituting the screen region, and controlling the emission brightness of the corresponding light source on the basis of the analysis results of the brightness value. As a result, the contrast of the displayed image is increased. Further, by using light sources of a plurality of colors as the light sources corresponding to the divided regions, it is possible to change not only the mission brightness of the backlight apparatus but also the emission color for each divided region. More specifically, by changing the emission brightness ratio of light sources of a plurality of colors, it is possible to change the emission color of the backlight apparatus. By controlling the emission color of the backlight apparatus for each divided region, it is possible to expand the color gamut of the displayed image.

For example, Patent Literature 4 discloses the technique for reducing color unevenness in a light source apparatus that can be controlled by local dimming. More specifically, Patent Literature 4 discloses the technique for reducing color unevenness generated at the outer edges of light-emitting clusters. With the technique disclosed in Patent Literature 4, each of a plurality of light source units (light-emitting clusters) corresponding to a plurality of divided regions is constituted by a plurality of red LEDs, a plurality of green LEDs, and a plurality of blue LEDs. The LEDs are arranged such that the following condition is fulfilled for each light source unit.

Condition: the centroid of the brightness profile based on a plurality of red LEDs, the centroid of the brightness profile based on a plurality of green LEDs, and the centroid of the brightness profile based on a plurality of blue LEDs substantially match the centroid of the light source unit.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

The color unevenness occurring in a light source apparatus having a plurality of light-emitting clusters each having LEDs of a plurality of colors will be explained below.

Considered initially is the case in which LEDs of the same color are arranged close to each other between the light-emitting clusters adjacent to each other. In this case, color unevenness in the form of stripe or grid pattern occurs when all of the light-emitting clusters are lit up.

The case in which local dimming control is performed is considered below. In this case, color unevenness occurs between the light-emitting clusters because the emission brightness differs among the light-emitting clusters. More specifically, where the emission brightness differs among the light-emitting clusters, the difference in the emission brightness of a specific color among the light-emitting clusters is perceived as color unevenness.

However, the abovementioned technique disclosed in Patent Literature 1 serves to reduce color unevenness generated at the top, bottom, and corners of the screen when all of the light-emitting clusters emit light with the same emission brightness, and color unevenness occurring during the local dimming control is not taken into consideration in this technique. Therefore, color unevenness occurring during the local dimming control cannot be reduced by using the technique disclosed in Patent Literature 1.

With the technique disclosed in Patent Literature 2, color unevenness occurring during the local dimming control is also not taken into consideration. Therefore, color unevenness occurring during the local dimming control cannot be reduced by using the technique disclosed in Patent Literature 2. Further, with the technique disclosed in Patent Literature 2, LEDs of the same color can be disposed close to each other between the light-emitting clusters which are adjacent to each other, and color unevenness in the form of a stripe pattern or grid pattern can occur.

With the technique disclosed in Patent Literature 3, color unevenness occurring during the local dimming control is also not taken into consideration. Therefore, color unevenness occurring during the local dimming control cannot be reduced by using the technique disclosed in Patent Literature 3. Further, the technique disclosed in Patent Literature 3 serves to reduce color unevenness in the case in which a light-emitting cluster has only one light source of a specific color with respect to each of a plurality of colors. However, when light of white color is obtained by using red LEDs, green LEDs, and blue LEDs, a plurality of green LEDs is used to increase the luminous quantity of the green LEDs. Further, with the technique disclosed in Patent Literature 3, the case in which a light-emitting cluster has a plurality of light sources as a light source of a single color is not taken into consideration.

The technique disclosed in Patent Literature 4 serves to reduce color unevenness occurring because the combination ability (color mixing ability) of light from LEDs of each color in the central portion differs from that at the outer edge, rather than color unevenness occurring during the local dimming control. Therefore, color unevenness occurring during the local dimming control cannot be reduced by using the technique disclosed in Patent Literature 4.

The present invention provides a technique that can more reliably reduce color unevenness of light emitted from a light source apparatus.

Solution to Problem

A light source apparatus according to the present invention includes a plurality of light source groups,

wherein each light source group has:

a plurality of first light sources configured to emit light of a first color;

a plurality of second light sources configured to emit light of a second color with a spectral peak wavelength longer than that of the first color; and

a plurality of third light sources configured to emit light of a third color with a spectral peak wavelength shorter than that of the first color, and

a distance between the plurality of second light sources of the same light source group and a distance between the plurality of third light sources of the same light source group are each shorter than a minimum value of a distance between the plurality of first light sources of the same light source group.

An image display apparatus according to the present invention includes:

a light source apparatus having a plurality of light source groups; and

a display unit configured to display an image on a screen by modulating light emitted from the light source apparatus,

wherein each light source group has:

a plurality of first light sources configured to emit light of a first color;

a plurality of second light sources configured to emit light of a second color with a spectral peak wavelength longer than that of the first color; and

a plurality of third light sources configured to emit light of a third color with a spectral peak wavelength shorter than that of the first color, and

a distance between the plurality of second light sources of the same light source group and a distance between the plurality of third light sources of the same light source group are each shorter than a minimum value of a distance between the plurality of first light sources of the same light source group.

Advantageous Effects of Invention

In accordance with the present invention, color unevenness of light emitted from a light source apparatus can be reduced more reliably.

DESCRIPTION OF EMBODIMENTS

The light source apparatus according to Embodiment 1 of the present invention will be explained below. The light source apparatus according to the present embodiment is a light source apparatus for which local dimming control can be performed. The light source apparatus according to the present embodiment can be used, for example, as a backlight apparatus for a liquid crystal display.

The light source apparatus according to the present embodiment is not limited to the backlight apparatus. The light source apparatus according to the present embodiment can be used in any image display apparatus in which an image is displayed by modulating light emitted from the light source apparatus. For example, the light source apparatus according to the present embodiment can be also used in a display of a MEMS shutter system which uses a MEMS (Micro Electro Mechanical System) shutter instead of a liquid crystal element. The light source apparatus according to the present embodiment can be also used in image display apparatuses such as advertisement and sign apparatuses, and sign display apparatuses. The light source apparatus according to the present embodiment can be also used as an illumination apparatus for street lighting, indoor lighting, microscope illumination, and the like.

(Configuration of the Light Source Device)

The general configuration of the light source apparatus according to the present embodiment will be explained below.

FIG. 1illustrates an example of the configuration of a light source apparatus100according to the present embodiment. InFIG. 1, an X direction is a horizontal direction of the light source apparatus100, a Y direction is a vertical direction of the light source apparatus100, and a Z direction is a height direction of the light source apparatus100.

As depicted inFIG. 1, the light source apparatus100has a plurality of light-emitting clusters13arranged as a matrix. In the example depicted inFIG. 1, the light source apparatus100has nine light-emitting clusters13arranged in three rows and three columns. The light source apparatus100also has a diffusion plate and a substrate which are not depicted inFIG. 1.

In the example depicted inFIG. 1, a distance L1is larger than a distance L2. The distance L1is a distance in the horizontal direction between a central position (P1) of the light-emitting cluster13and a central position of the light-emitting cluster13which is adjacent to the aforementioned light-emitting cluster13in the horizontal direction. The distance L2is a distance in the vertical direction between the central position of the light-emitting cluster13and the central position of the light-emitting cluster13which is adjacent to the aforementioned light-emitting cluster13in the vertical direction. Therefore, in the example depicted inFIG. 1, the light emission region (region from which light is emitted) of the light source apparatus100has a rectangular shape.

The plurality of light-emitting clusters13may be separated from each other, or may be not separated from each other.

The number of the light-emitting clusters13is not limited to nine. The number of the light-emitting clusters13may be greater or less than nine. For example, a plurality of light-emitting clusters13may be four light-emitting clusters13arranged in two rows and two columns, sixteen light-emitting clusters13arranged in four rows and four columns, and ten light-emitting clusters13arranged in two rows and five columns. Further, the plurality of light-emitting clusters13may not be arranged as a matrix. For example, the plurality of light-emitting clusters13may be arranged in a zigzag configuration.

The magnitude relationship between the distance L1and the distance L2is not limited to the abovementioned relationship. For example, the distance L1may be equal to the distance L2, or the distance L1may be less than the distance L2.

Each light-emitting cluster13is a light source group having a plurality of first light sources, a plurality of second light sources, and a plurality of third light sources. The first light source emits light of a first color. The second light source emits light of a second color with a spectral peak wavelength (main wavelength) longer than that of the first color. The third light source emits light of a third color with a spectral peak wavelength shorter than that of the first color. In the example depicted inFIG. 1, a green LED10(G light source) is used as the first light source, a red LED11(R light source) is used as the second light source, and a blue LED12(B light source) is used as the third light source. Further, in the example depicted inFIG. 1, each light-emitting cluster13has four green LEDs10, two red LEDs11, and two blue LEDs12. The green LED10is an LED emitting light of green color as the light of the first color. The red LED11is an LED emitting light of red color as the light of the second color. The blue LED12is an LED emitting light of blue color as the light of the third color. The spectrum of the light emitted by the green LED10has a peak (maximum value) in a wavelength range from 490 nm to 559 nm. In other words, the main wavelength range of the light emitted by the green LED10is from 490 nm to 559 nm. The main wavelength range of the light emitted by the red LED11is from 611 nm to 700 nm. The main wavelength range of the light emitted by the blue LED12is from 430 nm to less than 490 nm.

The first color, second color, and third color are not limited to the above-described colors (green, red, and blue). The main wavelength range of each light is not limited to the above-described ranges (the range from 490 nm to 559 nm, the range from 611 nm to 700 nm, and the range from 430 nm to less than 490 nm).

Further, the number of LEDs in each light-emitting cluster13is nor particularly limited. For example, the number of green LEDs10in the same light-emitting cluster13may be greater or less than four. The number of red LEDs11in the same light-emitting cluster13may be greater or less than two. The number of blue LEDs12in the same light-emitting cluster13may be greater or less than two.

The light source is not limited to the light-emitting diode (LED). For example, the light source may be a laser diode or an organic EL element.

In the present embodiment, when the local dimming control is performed, the emission brightness of each light-emitting cluster13is individually controlled. Further, in the present embodiment, when the local dimming control is performed, the emission brightness of each of a plurality of LEDs in the same light-emitting cluster13is controlled such that light of a predetermined color is emitted from the corresponding light-emitting cluster13. When the predetermined color is white color, for example, the emission brightness of each LED is controlled such that the (emission brightness of the green LED10):(emission brightness of the red LED11):(emission brightness of the blue LED12) ratio is 7:3:1.

In the present embodiment, by using LEDs of a plurality of colors, it is possible to expand the color gamut of the light of the predetermined color with respect to that when a single-color LEDs are used. More specifically, the chromaticity point of the light of the predetermined color can be changed by finely adjusting the ratio of the emission brightness of the green LEDs10, emission brightness of the red LEDs11, and the emission brightness of the blue LEDs12.

The predetermined color may be other than white color.

Where the light source apparatus100is for an image display apparatus, the plurality of light-emitting clusters13is provided correspondingly to the plurality of divided regions constituting the screen region. For example, the light-emitting clusters13are provided such as to emit light on the corresponding divided regions (divided regions corresponding to the light-emitting clusters13) on the rear surface of the display panel (display portion). More specifically, the light-emitting clusters13are provided such that central position P1of the light-emitting clusters13substantially matches the central position of the corresponding divided region. In the present embodiment, “substantially matches” is inclusive of “perfectly matches”.

Explained hereinbelow is an example in which a plurality of divided regions arranged as a matrix is obtained. Where the aspect ratio of the screen is 16 (horizontal direction):9 (vertical direction), the screen is divided by a multiple of 16 in the horizontal direction and by a multiple of 9 in the vertical direction, thereby producing square divided regions. The number of the divided regions is determined on the basis, for example, of the contrast required for the image display apparatus.

Regions different from the divided regions (regions of at least part of the screen) may be defined as corresponding regions corresponding to light-emitting clusters. The corresponding regions may be superimposed on other corresponding regions. A plurality of regions that are not in contact with each other may be defined as a plurality of corresponding regions. One corresponding region may be associated with two or more light-emitting clusters. The above-described divided regions can be also referred to as “corresponding regions”.

A plurality of corresponding regions is not necessarily arranged as a matrix. For example, a plurality of corresponding regions may be arranged in a zigzag manner.

The size of the light-emitting cluster13may or may not be equal to the size of the corresponding region. The size of the light-emitting cluster13may be greater or less than the size of the corresponding region.

The shape of the corresponding region may be other than square. For example, the corresponding region may have a quadrangular shape other than square shape (rectangle, parallelogram, trapezoid, etc.), a round shape, a triangular shape, or a pentagonal shape.

A reflective wall with a high light reflectivity may be provided at the outer edge (end portion) of the light source apparatus100in order to improve brightness and ability of mixing colors of (ability to combine (mix colors of) light emitted by the green LEDs10, red LEDs11, and blue LEDs12) at the outer edge. Where the light source apparatus100is for an image display apparatus, the reflective wall may be provided such as to surround the display region (screen region) of the image display apparatus or a region including the display region (region larger than the display region).

(Arrangement of Light Sources)

The arrangement of light sources according to the present embodiment will be explained hereinbelow.

Initially, the arrangement of green LEDs10, which are the first light sources, will be explained.

In the example depicted inFIG. 1, the four green LEDs10of the same light-emitting cluster13are arranged on the outside of other LEDs (red LEDs11and blue LEDs12), when viewed from the central position P1of the light-emitting cluster. Further, in the example depicted inFIG. 1, the four green LEDs10of the same light-emitting cluster13are arranged to be substantially point symmetrical with respect to the central position P1of the light-emitting cluster13. Furthermore, in the example depicted inFIG. 1, the four green LEDs10of the same light-emitting cluster13are arranged to form a matrix of two rows and two columns. The row direction of the matrix substantially matches the horizontal direction, and the column direction of the matrix substantially matches the vertical direction. Further, in the example depicted inFIG. 1, the green LEDs10are arranged such that the minimum value of the distance between the four green LEDs10of the same light-emitting cluster13(the minimum value of the distance in the horizontal direction and the minimum value of the distance in the vertical direction) is L3.

Therefore, in the example depicted inFIG. 1, the light-emitting region (the region in which light is emitted) of each light-emitting cluster13has a square shape.

Where light of white color is to be obtained as the light emitted from the light-emitting cluster, the green LEDs10are light sources emitting light of a brightness higher than that of the light emitted by the red LEDs11or blue LEDs12. By arranging the four green LEDs10emitting light of a high brightness such as to obtain a substantially point symmetrical configuration with respect to the central position P1of the light-emitting cluster13, it is possible to obtain a brightness distribution with the highest brightness in the central position P1as the brightness distribution of the light emitted from the light-emitting cluster13.

Further, in the example depicted inFIG. 1, the distance L3is shorter than a minimum value L6of the distance between the green LEDs10of the light-emitting cluster13and the green LEDs10of the light-emitting cluster13adjacent to the aforementioned light-emitting cluster13. Thus, in the example depicted inFIG. 1, the green LEDs10are arranged such that the following Conditional Expression 1 is fulfilled.
Distance L3<distance L6  (Conditional Expression 1).

As a result of fulfilling the Conditional Expression 1, it is possible to increase the ability of mixing colors of the light emitted by a plurality of LEDs of the light-emitting cluster13. As a consequence, the color unevenness (color unevenness in the form of a stripe pattern or grid pattern) of the light emitted by the light source apparatus100can be reduced.

In other words, as a result of making the distance L6longer than the distance L3, it is possible to reduce the number of light-emitting clusters and reduce the total number of LEDs. Therefore, the cost of the light source apparatus or display apparatus can be reduced. Since the color unevenness of the light emitted from the light-emitting cluster13can be reduced, even though the distance L6is thus longer than the distance L3, the color unevenness between the plurality of mutually adjacent light-emitting clusters13is also small.

The distance between LEDs may be defined in any way. For example, the distance between the central position of an LED and the central position of an adjacent LED may be used as the distance between the LEDs. The distance between the edge of an LED and the edge of an adjacent LED may be used as the distance between the LEDs. The two edges are, for example, two edges positioned on the same side, or two mutually opposing edges.

The shape of the corresponding region may be other than square. For example, the corresponding region may have a quadrangular shape other than square shape (rectangle, parallelogram, trapezoid, etc.), a round shape, a triangular shape, or a pentagonal shape.

Explained hereinbelow are the arrangement of the red LEDs11, which are the second light sources, and the arrangement of the blue LEDs12, which are the third light source.

As follows from the CIE1976UCS chromaticity diagram, in human color vision, the difference in tinge or brightness is perceived easier in the red or blue color than in the green color. Therefore, when the red LEDs11or the blue LEDs12are arranged at the outer edge of the light-emitting cluster13, the color of the light emitted by the light-emitting cluster13becomes uneven. More specifically, in the central portion of the light-emitting cluster13, the colors of the light emitted by the green LEDs10, red LEDs11, and blue LEDs12are mixed sufficiently, and therefore light of a white color can be obtained as the light emitted by the light-emitting cluster13. Meanwhile, at the outer edge of the light-emitting cluster13, the color mixing is insufficient, and the light of reddish color or bluish color is obtained as the light emitted by the light-emitting cluster13. As a result, color unevenness occurs. Such color unevenness becomes more prominent when the emission brightness differs among the light-emitting clusters13, such as during the local dimming control.

In the present embodiment, the arrangement of the red LEDs11and the blue LEDs12is devised to also reduce such color unevenness.

In the example depicted inFIG. 1, the two red LEDs11of the same light-emitting cluster13are arranged to be substantially point symmetrical with respect to the central position P1of the light-emitting cluster13. The two blue LEDs12of the same light-emitting cluster13are also arranged to be substantially point symmetrical with respect to the central position P1of the light-emitting cluster13. Further, in the example depicted inFIG. 1, a distance L4between the two red LEDs11of the same light-emitting cluster13is shorter than the distance L3, and a distance L5between the two blue LEDs12of the same light-emitting cluster13is also shorter than the distance L3. Thus, in the example depicted inFIG. 1, the red LEDs11and the blue LEDs12are arranged such that the following Conditional Expressions 2 and 3 are fulfilled.
Distance L4<distance L3  (Conditional Expression 2).
Distance L5<distance L3  (Conditional Expression 3).

As a result of arranging the two red LEDs11and the two blue LEDs12to be substantially point symmetrical with respect to the central position P1and fulfilling the Conditional Expressions 2 and 3, it is possible to increase further the ability of mixing colors of the light emitted by a plurality of LEDs of the light-emitting cluster13. As a consequence, even when a variation in emission color or emission brightness occurs among the LEDs of the same color, this variation is unlikely to be perceived. Eventually, the aforementioned color unevenness which becomes prominent during the local dimming control can be reduced.

Since the distances L4and L5between the red LEDs and the blue LEDs, for which the difference in tinge or brightness is perceived easier than in the green color in human color vision, are made shorter than the distance L3between the green LEDs, the effect of the production variation among the red and blue LEDs can be reduced.

Further, in the present embodiment, the two red LEDs11of the same light-emitting cluster13are arranged side by side in one of the row direction (the horizontal direction) and the column direction (the vertical direction). The two blue LEDs12of the same light-emitting cluster13are arranged side by side in the other of the row direction and the column direction. In the example depicted inFIG. 1, the two red LEDs11of the same light-emitting cluster13are arranged side by side in the column direction, and the two blue LEDs12of the same light-emitting cluster13are arranged side by side in the row direction.

The distance L4may or may not be equal to the distance L5. The distance L4may be longer or shorter than the distance L5.

As mentioned hereinabove, in accordance with the present embodiment, the plurality of light sources of the same light-emitting cluster is arranged such that the following three conditions 1 to 3 are fulfilled.

Condition 1: the plurality of first light sources, the plurality of second light sources, and the plurality of third light sources of the same light-emitting cluster are each arranged to be substantially point symmetrical with respect to the central position of the light-emitting cluster.

Condition 2: the minimum value of the distance between the plurality of first light sources of the same light-emitting cluster is shorter than the minimum value of the distance between the first light source of the same light-emitting cluster and the first light source of the light-emitting cluster adjacent to the aforementioned light-emitting cluster.

Condition 3: the distance between the plurality of second light sources of the same light-emitting cluster and the distance between the plurality of third light sources of the same light-emitting cluster are each shorter than the distance between the plurality of first light sources of the same light-emitting cluster.

As a result, the color unevenness of the light emitted by the light source apparatus can be reduced more reliably. More specifically, both the color unevenness in the form of a stripe pattern or grid pattern and the color unevenness which is prominently demonstrated during the local dimming control can be reduced.

The arrangement of the light sources is not particularly limited, provided the conditions 1 to 3 are fulfilled. For example, the row direction and column direction of the matrix formed by the four green LEDs of the same light-emitting cluster may be different from the horizontal direction and vertical direction of the light source apparatus. The two red LEDs of the same light-emitting cluster may be arranged side by side in the row direction of the matrix, and the two blue LEDs of the same light-emitting cluster may be arranged side by side in the column direction of the matrix. The two red LEDs of the same light-emitting cluster may be arranged side by side in a direction different from the above-described row direction, column direction, horizontal direction, and vertical direction. The same is also true with respect to the two blue LEDs of the same light-emitting cluster.

The light source apparatus according to Embodiment 2 of the present invention will be explained hereinbelow.

In the present embodiment, the configuration, number, arrangement, and the like, of light-emitting clusters of the light source apparatus are the same as in Embodiment 1, and the explanation thereof is herein omitted.

FIG. 2is a side view illustrating an example of the configuration of a light source apparatus200according to the present embodiment.

As depicted inFIG. 2, the light source apparatus200has a plurality of light-emitting clusters13, a diffusion plate14, and a substrate15. In the example depicted inFIG. 2, the plurality of light-emitting clusters13is provided on the substrate15. The substrate15is a plate-shaped member with a high light reflectivity. Therefore, the substrate15can be also called a “reflective plate”. The diffusion plate14is a diffusion member that diffuses the light emitted by the plurality of light-emitting cluster13.

A plate-shaped member with a low light reflectivity may be also used as the substrate15. However, by using a plate-shaped member with a high light reflectivity as the substrate15, it is possible to improve the ability of mixing colors of the light emitted from a plurality of LEDs of the light-emitting cluster13.

The diffusion member is not limited to the plate-like shape.

The diffusion plate14is provided at a position opposite the plurality of light-emitting clusters13. In the example depicted inFIG. 2, a distance H between the central position of the diffusion plate14and the central position of the light-emitting cluster13(LED) is shorter than the distance L1and larger than the distance L6. The distance H is the distance in the light emission direction of the light-emitting cluster13. Further, the distance H is also shorter than the distance L2(this is not depicted inFIG. 2). Thus, in the example depicted inFIG. 2, the diffusion plate14is arranged such that the following Conditional Expression 4 is fulfilled.
Distance L6<distance H<distance L1 and distance L2  (Conditional Expression 4)

By fulfilling the Conditional Expression 4, it is possible to reduce brightness unevenness of the light emitted from the light source apparatus200. More specifically, by fulfilling the requirement of “distance H<distance L1and distance L2” of the Conditional Expression 4, it is possible to reduce brightness unevenness of the light emitted from the light source apparatus200.

The distance H may be shorter than the distance L6.

FIG. 3illustrates an example of brightness distribution of the light emitted from the light source apparatus200(diffusion plate14). The brightness distribution depicted inFIG. 3is obtained when four light-emitting clusters13arranged around a point P2inFIG. 1arte caused to emit light. This brightness distribution relates to the case in which distance L1=distance L2=37 mm and distance L6=26 mm. InFIG. 3, the brightness distribution is depicted with respect to a total of four cases: the case in which the distance H is 29 mm, the case in which the distance H is 31 mm, the case in which the distance H is 33 mm, and the case in which the distance H is 40 mm. A distance from the point P2in the horizontal direction and vertical direction is plotted against the abscissa inFIG. 3, and the brightness normalized such that the brightness in the point P2is “1” is plotted against the ordinate inFIG. 3.

As depicted inFIG. 3, when the distance H is 29 mm, 31 mm, and 33 mm, the brightness unevenness is comparatively small. When the distance H is 40 mm, the brightness changes rapidly at a position which is set apart from the point P2. Thus, when the distance H is 40 mm, the brightness unevenness is large. Therefore, it is important to provide the distance H with an upper limit value, and by fulfilling the requirement of “distance H<distance L1and distance L2”, it is possible to reduce the brightness unevenness of light emitted from the light source apparatus200. Although the optimum lower limit value of the distance H changes depending on the properties of the diffusion plate14, the allowable brightness unevenness and the like, the distance L6can be used as the lower limit value of the distance H.

As described hereinabove, according to the present embodiment, the plurality of light sources of the same light-emitting cluster are arranged such that the conditions 1 to 3 described in Embodiment 1 are fulfilled. As a result, the effect same as that described in Embodiment 1 can be obtained. Further, in the present embodiment, the plurality of light-emitting clusters and the diffusion plate are arranged such that the requirement of “distance H<distance L1and distance L2” is fulfilled. As a result, the brightness unevenness can be also reduced.

The configuration of the light source apparatus according to the present embodiment can be also variously changed in the same manner as in Embodiment 1.

The light source apparatus according to Embodiment 3 of the present invention will be explained hereinbelow.

FIG. 4illustrates an example of the configuration of a light source apparatus300according to the present embodiment.

As depicted inFIG. 4, the light source apparatus300has nine light-emitting clusters (five light-emitting clusters33and four light-emitting clusters34). Each light-emitting cluster has four green LEDs30, two red LEDs31, and two blue LEDs32. The arrangement of the light-emitting clusters and the arrangement of the green LEDs30are the same as in Embodiment 1. The light source apparatus300further includes a diffusion plate and a substrate (not depicted inFIG. 4).

In the example depicted inFIG. 4, the positional relationship between the two red LEDs31and the two blue LEDs32of the same light-emitting cluster differs among the mutually adjacent light-emitting clusters. More specifically, the light-emitting clusters are arranged such that the light-emitting cluster33is adjacent to the light-emitting cluster34, rather than to another light-emitting cluster33. In the light-emitting cluster33, the two red LEDs31are arranged side by side in the vertical direction, and the two blue LEDs32are arranged side by side in the horizontal direction. In the light-emitting cluster34, the two red LEDs31are arranged side by side in the horizontal direction, and the two blue LEDs32are arranged side by side in the vertical direction. Therefore, in the example depicted inFIG. 4, the array directions of the two red LEDs31and the two blue LEDs32of the same light-emitting cluster are interchanged among the mutually adjacent light-emitting clusters.

With the above-described arrangement, the shortest distance between the red LED31and the blue LED32in the mutually adjacent light-emitting clusters can be reduced. Therefore, even when color unevenness in the form of a grid pattern or stripe pattern occurs, the color of the grid pattern or stripe pattern becomes a magenta color which is a mixture of red color and blue color. In the color vision of humans, the tinge and brightness of the magenta color is unlikely to be perceived compared with those of the red color or blue color. Therefore, with the above-described arrangement, color unevenness in the form of a grid pattern or stripe pattern can be difficult to recognize visually.

As described hereinabove, according to the present embodiment, the plurality of light sources of the same light-emitting cluster are arranged such that the conditions 1 to 3 described in Embodiment 1 are fulfilled. As a result, the effect same as that described in Embodiment 1 can be obtained. Further, in the present embodiment, the positional relationship of the plurality of second light sources and the plurality of third light sources of the same light-emitting cluster of the same light source group differ among the mutually adjacent clusters. As a result, the color unevenness in the form of a grid pattern or stripe pattern can be difficult to perceive (recognize visually).

The configuration of the light source apparatus according to the present embodiment can be also variously changed in the same manner as in Embodiment 1.

The light source apparatus according to Embodiment 4 of the present invention will be explained hereinbelow.

(Configuration of the Light Source Device)

The general configuration of the light source apparatus according to the present embodiment will be explained below.

FIG. 5illustrates an example of the configuration of a light source apparatus400according to the present embodiment.

As depicted inFIG. 5, the light source apparatus400has nine light-emitting clusters (five light-emitting clusters46and four light-emitting clusters47). The arrangement of the light-emitting clusters is the same as in Embodiment 1. The light source apparatus400further includes a diffusion plate and a substrate (not depicted inFIG. 5).

In the example depicted inFIG. 5, each light-emitting cluster has two first green LEDs40(light sources C), two second green LEDs41(light sources D), one first red LED42, one second red LED43, one first blue LED44, and one second blue LED45. InFIG. 5, the first green LED40is denoted by “G1”, the second green LED41is denoted by “G2”, the first red LED42is denoted by “R1”, the second red LED43is denoted by “R2”, the first blue LED44is denoted by “B1”, and the second blue LED45is denoted by “B2”.

The second green LED41emits light that differs in the main wavelength from the light emitted by the first green LED40. For example, the main wavelength of the light emitted by the second green LED41is set apart by about 6 nm to 16 nm from the main wavelength of the light emitted by the first green LED40.

The second red LED43emits light that differs in the main wavelength from the light emitted by the first red LED42. For example, the main wavelength of the light emitted by the second red LED43is set apart by about 6 nm to 16 nm from the main wavelength of the light emitted by the first red LED42.

The second blue LED45emits light that differs in the main wavelength from the light emitted by the first blue LED44. For example, the main wavelength of the light emitted by the second blue LED45is set apart by about 6 nm to 16 nm from the main wavelength of the light emitted by the first blue LED44.

The numbers of the first green LEDs40, second green LEDs41, first red LEDs42, second red LEDs43, first blue LEDs44, and second blue LEDs45may be larger than the above-described numbers.

In the light-emitting clusters46, the first red LED42and the second red LED43are arranged side by side in the vertical direction, and the first blue LED44and the second blue LED45are arranged side by side in the horizontal direction. In the light-emitting clusters47, the first red LED42and the second red LED43are arranged side by side in the horizontal direction, and the first blue LED44and the second blue LED45are arranged side by side in the vertical direction. The light-emitting clusters are arranged such that the light-emitting cluster46is adjacent to the light-emitting cluster47, rather than to another light-emitting cluster46.

(Arrangement of the Light Sources)

The arrangement of the light sources according to the present embodiment is explained hereinbelow.

In the example depicted inFIG. 5, the first green LEDs40and the second green LEDs41of the same light-emitting cluster are arranged to be substantially point symmetrical with respect to the central position P1of the light-emitting cluster. Among the plurality of green LEDs of the same light-emitting cluster, the green LED which is the closest to the first green LED40of the light-emitting cluster adjacent to the aforementioned light-emitting cluster is the second green LED41. Among the plurality of green LEDs of the same light-emitting cluster, the green LED which is the closest to the second green LED41of the light-emitting cluster adjacent to the aforementioned light-emitting cluster is the first green LED40.

The red LEDs and the blue LEDs are arranged in the same manner as the green LEDs.

In the example depicted inFIG. 5, the first red LEDs42and the second red LEDs43of the same light-emitting cluster are arranged to be substantially point symmetrical with respect to the central position P1of the light-emitting cluster. Further, the first blue LEDs44and the second blue LEDs45of the same light-emitting cluster are arranged to be substantially point symmetrical with respect to the central position P1of the light-emitting cluster.

Among the plurality of light sources of the same light-emitting cluster, a plurality of light sources of the same color system for which the main wavelengths have been set apart are arranged to be point symmetrical with respect to the central position of the light-emitting cluster, thereby making it possible to improve the ability of mixing colors of the light emitted from the plurality of light sources of the same light-emitting cluster. As a result, color unevenness in the form of a grid pattern or stripe pattern can be reduced. Further, the color mixing ability can be also improved by arranging two light sources of the same color system for which the main wavelengths have been set apart as the two light sources of the same color system which are the closest to each other among the mutually adjacent light-emitting clusters. As a result, color unevenness in the form of a grid pattern or stripe pattern can be reduced.

As mentioned hereinabove, in accordance with the present embodiment, the plurality of light sources of the same light-emitting cluster is arranged such that the conditions 1 to 3 described in Embodiment 1 are fulfilled. As a result, the effect same as that described in Embodiment 1 can be obtained. Further, in accordance with the present embodiment, the second light sources and third light sources are arranged in the positional relationship described in Embodiment 3. As a result, the effect same as that described in Embodiment 3 can be obtained. Further, in accordance with the present embodiment, the plurality of light sources of the same light-emitting cluster is arranged such that the following conditions 4 and 5 are fulfilled.

Condition 4: among the plurality of light sources of the same light-emitting cluster, a plurality of light sources of the same color system for which the main wavelengths have been set apart is arranged to be point symmetrical with respect to the central position of the light-emitting cluster.

Condition 5: two light sources of the same color system for which the main wavelengths have been set apart are arranged as the two light sources of the same color system which are the closest to each other among the mutually adjacent light-emitting clusters.

As a result, color unevenness in the form of a stripe pattern or grid pattern can be reduced.

One of the aforementioned conditions 4 and 5 may not be fulfilled.

Further, in the present embodiment, an example is explained in which the arrangement of the first light sources fulfils the conditions 4 and 5 and the arrangement of the second light sources and third light sources fulfils the condition 4, but such an example is not limiting. For example, when the same light-emitting cluster has a plurality of first red LEDs and a plurality of second red LEDs, the arrangement of the red LEDs (second light sources) may fulfil the conditions 4 and 5. When the same light-emitting cluster has a plurality of first blue LEDs and a plurality of second blue LEDs, the arrangement of the blue LEDs (third light sources) may fulfil the conditions 4 and 5.

The configuration of the light source apparatus according to the present embodiment can be also variously changed in the same manner as in Embodiment 1.

An example of the configuration of an image display apparatus800according to Embodiment 5 of the present invention will be explained below with reference toFIGS. 6A, 6B, and 6C.FIG. 6Ais an exploded perspective view of the image display apparatus800.

The image display apparatus800has a liquid crystal panel801, a direct-under-type backlight unit802(light source apparatus) provided at the rear surface side of the liquid crystal panel801, and a frame body803holding the liquid crystal panel801from the display surface side.

The backlight unit802is a box-shaped member that is substantially closed by a backlight case802athat is open at the liquid crystal panel801side and an optical sheet group802bhaving light transmission, diffusion, or collection ability. A light source substrate802chaving a plurality of LEDs is arranged inside the backlight unit802(at the surface of the backlight case802afacing the optical sheet group802b). Further, a reflective sheet802eprovided with a through orifice802f, such that the LEDs of the light source substrate802care exposed, is arranged on the light source substrate802c(optical sheet group802bside of the light source substrate802c). Because of the above-described configuration, the backlight unit802functions as a surface light source that emits light of uniform brightness and chromaticity within the light emission surface (the surface on the side where the optical sheet group802bis provided).

FIG. 6Bis an enlarged view of the portion denoted by the reference symbol C inFIG. 6A. More specifically,FIG. 6Billustrates the arrangement of the light-emitting members (light-emitting diodes (LEDs)) and the through orifice802fof the reflective sheet802ewhich promotes reflective diffusion of light from the LEDs.

In the backlight unit802, the plurality of LEDs emitting light of mutually different peak wavelengths, namely, LEDs806R, LEDs806G, and LEDs806B, are used as a single light-emitting cluster (light source group) for increasing color reproducibility of the light emitted by the backlight unit802. In the example depicted inFIG. 6B, one light-emitting cluster is constituted by a total of eight LEDs, namely, two LEDs806R, four LEDs806G, and two LEDs806B. In this case, the LEDs806R,806G, and806B are such that a circumscribing quadrangle thereof in the plane parallel to the light emission surface of the light source apparatus (plane parallel to the light source substrate802c) is a rectangle. InFIG. 6B, the LEDs (LEDs806R,806G, and806B) are represented by rectangles, which are the circumscribing quadrangles thereof, for the sake of simplicity. The LED806R is an LED emitting red light, the LED806G is an LED emitting green light, and the LED806B is an LED emitting blue light.

Further, the plurality of LEDs included in one light-emitting cluster is arranged such that the distance between the LEDs (distance between light emission centers) is small in order to improve uniformity of brightness and chromaticity in the light emission surface of the light emitted by the backlight unit802.

In the example depicted inFIG. 6B, the LEDs are arranged in the following manner in the plane parallel to the light emission surface of the light source apparatus.

Thus, the LEDs are arranged such that the long sides of each of the four LEDs806G are parallel to the long sides of the liquid crystal panel801, and the long sides of the two LEDs806R and two LEDs806B are parallel to the short sides of the liquid crystal panel801.

By arranging the eight LEDs in such a concentrated manner, it is possible to reduce the size of the through orifice802fof the reflective sheet. Therefore, the reflective surface area (effective surface area) of the reflective sheet can be increased, the light from the LEDs can be used efficiently, and the emission brightness can be increased.

Further, as explained in Embodiment 2, the arrangement of the LEDs806R and LEDs806B of the light-emitting cluster adjacent to the light-emitting cluster depicted inFIG. 6Bmay be interchanged with the arrangement of the LEDs806R and LEDs806B of the light-emitting cluster depicted inFIG. 6B(this configuration is not depicted in the figure).

FIG. 6Cillustrates a structural example of each LED. In each LED, a circumscribing quadrangle903in the plane perpendicular to the light emission direction (the plane parallel to the light emission surface of the light source apparatus, that is, the plane parallel to the light source substrate802c) is a rectangle (substantially rectangle). For example, as depicted inFIG. 6C, in an LED having a light-emitting portion901of a substantially square shape in the plane perpendicular to the light emission direction and an electrode902provided at two ends in one direction perpendicular to the light emission direction (one direction parallel to the light emission surface of the light source apparatus, that is, one direction parallel to the light source substrate802C), the circumscribing quadrangle903in the plane perpendicular to the light emission direction is a rectangle. In the example depicted inFIG. 6C, the circumscribing quadrangle903is a rectangle in which the left and right sides are short sides and the top and bottom sides are long sides. When such an LED is used, the through orifice802fis provided so as to expose the whole LED, rather than only the light-emitting portion of the LED.

The configuration of the light source apparatus according to the present embodiment can be also variously changed in the same manner as in Embodiment 1.

The present invention is also inclusive of a configuration obtained by combining, to the extent possible, the features set forth in the above-described Embodiments 1 to 4. For example, the present invention is also inclusive of a light source apparatus in which, for example, both the arrangement of the diffusion member described in Embodiment 2 and the arrangement of the light sources described in Embodiment 3 are realized. The present invention is also inclusive of a light source apparatus in which both the arrangement of the light sources described in Embodiment 1 and the conditions 4 and 5 described in Embodiment 4 are realized, and a light source apparatus in which both the arrangement of the diffusion member described in Embodiment 2 and the conditions 4 and 5 described in Embodiment 4 are realized. The present invention is also inclusive of a light source apparatus in which both the arrangement of the light sources described in Embodiment 1 and the configuration of the backlight unit described in Embodiment 5 are realized, and a light source apparatus in which both the arrangement of the diffusion member described in Embodiment 2 and the configuration of the backlight unit described in Embodiment 5 are realized. Further, the present invention is also inclusive of a light source apparatus in which both the arrangement of the light sources described in Embodiment 3 and the configuration of the backlight unit described in Embodiment 5 are realized, and a light source apparatus in which both the conditions 4 and 5 described in Embodiment 4 and the configuration of the backlight unit described in Embodiment 5 are realized.

This application claims the benefit of Japanese Patent Application No. 2014-213766, filed on Oct. 20, 2014, and Japanese Patent Application No. 2015-143073, filed on Jul. 17, 2015, which are hereby incorporated by reference herein in their entirety.

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