Display device

Abstract

This display device (DSP) comprises: a liquid crystal panel (PNL) provided with a display area (DA) for displaying an image; and an illumination device (IL) configured to illuminate the liquid crystal panel (PNL). The illumination device (IL) comprises: a light guide plate (LG) that overlaps the liquid crystal panel (PNL); a first light source unit (LS1) configured to emit first illumination light; a second light source unit (LS2) configured to emit second illumination light; a first optical element (OE1) that is located between the first light source unit (LS1) and the second light source unit (LS2), that has a first end face opposing the first light source unit (LS1) and a first emission face opposing the light guide plate, and that is configured to guide the first illumination light to the light guide plate (LG); and a second optical element (OE2) that is located between the first light source unit (LS1) and the second light source unit (LS2), that overlaps the first optical element (OE1), that has a second end face opposing the second light source unit (LS2) and a second emission face opposing the light guide plate (LG), and that is configured to guide the second illumination light to the light guide plate (LG).

Description

Display device

[0001] An embodiment of the present invention relates to a display device.

[0002] For example, a liquid crystal display device including an illumination device utilizing laser light has been proposed. This illumination device includes a light guide body having a mirror array. The light guide body is configured to propagate laser light while totally reflecting it, and to reflect a part of the laser light at the mirror array. In such a display device, improvement of display quality is demanded.

[0003] International Publication No. 2008 / 078543

[0004] An embodiment aims to provide a display device capable of improving display quality as one of its objects.

[0005] In general, according to one embodiment, a display device includes a liquid crystal panel having a display region for displaying an image, and an illumination device configured to illuminate the liquid crystal panel, and the illumination device includes a light guide plate overlapping the liquid crystal panel, a first light source unit configured to emit first illumination light, a second light source unit configured to emit second illumination light, a first optical element located between the first light source unit and the second light source unit, having a first end face facing the first light source unit and a first emission face facing the light guide plate, and configured to guide the first illumination light to the light guide plate, and a second optical element located between the first light source unit and the second light source unit, overlapping the first optical element, having a second end face facing the second light source unit and a second emission face facing the light guide plate, and configured to guide the second illumination light to the light guide plate.

[0006] According to another embodiment, the display device comprises a first liquid crystal panel having a display area for displaying an image, a second liquid crystal panel having a display area for displaying an image, and an illumination device configured to illuminate the first liquid crystal panel and the second liquid crystal panel, wherein the illumination device comprises a first light guide plate overlapping the first liquid crystal panel, a second light guide plate overlapping the second liquid crystal panel, a first light source unit configured to emit first illumination light, a second light source unit configured to emit second illumination light, and a unit located between the first light source unit and the second light source unit and opposite the first light source unit. The device comprises: a first optical element having a first end face facing the first light guide plate and a first emitting surface facing the first light guide plate and the second light guide plate, and configured to guide the first illumination light to the first light guide plate and the second light guide plate; and a second optical element located between the first light source unit and the second light source unit, overlapping the first optical element, having a second end face facing the second light source unit, and a second emitting surface facing the first light guide plate and the second light guide plate, and configured to guide the second illumination light to the first light guide plate and the second light guide plate.

[0007] According to another embodiment, the display device comprises a liquid crystal panel having a display area for displaying an image, and an illumination device configured to illuminate the liquid crystal panel, wherein the illumination device comprises a light guide plate overlapping the liquid crystal panel, a first light source unit configured to emit a first illumination light, a second light source unit configured to emit a second illumination light, and an optical element having a first end face facing the first and second light sources, and a first emission surface facing the light guide plate, and configured to guide the first illumination light and the second illumination light to the light guide plate.

[0008] Figure 1 is a diagram illustrating one example configuration of a display device DSP. Figure 2 is a cross-sectional view showing one example configuration of a display device DSP along line A-B in Figure 1. Figure 3 is a plan view showing the light source units LS1 and LS2 shown in Figure 1. Figure 4 is a diagram illustrating the positional relationship between the composite elements DM1 and DM2 and the optical elements OE1 and OE2. Figure 5A is a diagram illustrating how illumination light is generated in the illumination device IL shown in Figure 1. Figure 5B is a diagram illustrating how illumination light is generated in the illumination device IL shown in Figure 1. Figure 6 is a diagram illustrating another example configuration of a display device DSP. Figure 7A is a diagram illustrating how illumination light is generated in the illumination device IL shown in Figure 6. Figure 7B is a diagram illustrating how illumination light is generated in the illumination device IL shown in Figure 6. Figure 8 is a diagram illustrating another example configuration of a display device DSP. Figure 9 is a plan view showing the light source units LS1 and LS2 shown in Figure 8. Figure 10 is a diagram illustrating how illumination light is generated in the illumination device IL shown in Figure 8. Figure 11 is a plan view showing another example of the configuration of the light source unit LS.

[0009] The embodiments will be described below with reference to the drawings. The disclosure is merely an example, and any modifications that a person skilled in the art could easily conceive of while maintaining the spirit of the disclosure are naturally included within the scope of this disclosure. In addition, the drawings may schematically represent the width, thickness, shape, etc. of each part compared to the actual embodiment in order to make the explanation clearer, but these are merely examples and do not limit the interpretation of this disclosure. Furthermore, in this specification and in each drawing, the same reference numerals are used for components that perform the same or similar functions as those described above with respect to previously shown drawings, and redundant detailed explanations may be omitted as appropriate.

[0010] Furthermore, the drawings will include mutually orthogonal X, Y, and Z axes as needed to facilitate understanding. The direction along the X-axis will be referred to as the first direction X, the direction along the Y-axis as the second direction Y, and the direction along the Z-axis as the third direction Z. Viewing various elements parallel to the third direction Z is called a plan view. In addition, terms referring to the positional relationship between two or more constituent elements, such as above, above, between, and opposite, include not only cases where the two or more constituent elements of an object are in direct contact, but also cases where they are separated from each other by gaps or other constituent elements.

[0011] The display device according to this embodiment is a liquid crystal display device, which can be applied, for example, to a display device for a head-mounted display. A head-mounted display is worn on the user's head and is used to provide the user with, for example, virtual reality or augmented reality.

[0012] Figure 1 is a diagram illustrating one example configuration of a display device DSP.

[0013] The display device DSP comprises an illumination device IL and a liquid crystal panel PNL. The liquid crystal panel PNL is formed in a flat plate shape and, in a plan view, is formed in a rectangular shape having a pair of sides along a first direction X and a pair of sides along a second direction Y. Note that the planar shape of the liquid crystal panel PNL is not limited to the illustrated example. The third direction Z corresponds to the thickness direction of the display device DSP. The illumination device IL is configured to overlap the liquid crystal panel PNL in the third direction Z and to illuminate the liquid crystal panel PNL.

[0014] The lighting device IL comprises multiple light source units LS1 and LS2, multiple optical elements OE1 and OE2, a light guide plate LG, and multiple optical sheets OS.

[0015] The light source units LS1 and LS2 are arranged to face each other in the first direction X. Each of the light source units LS1 and LS2 is configured to emit illumination light, as will be described in detail later.

[0016] Optical elements OE1 and OE2 are located between light source units LS1 and LS2 in a first direction X, and overlap in a third direction Z. Each of optical elements OE1 and OE2 is formed in a rod shape extending in the first direction X. One end face of optical element OE1 faces the light source unit LS1. One end face of optical element OE2 faces the light source unit LS2. Optical element OE1 has an output surface facing the light guide plate LG and is configured to guide illumination light emitted from light source unit LS1 to the light guide plate LG. Optical element OE2 also has an output surface facing the light guide plate LG and is configured to guide illumination light emitted from light source unit LS2 to the light guide plate LG.

[0017] The light guide plate LG overlaps the liquid crystal panel PNL in the third direction Z. The light guide plate LG is formed in a flat shape and, in a plan view, is formed in a rectangular shape having a pair of sides along the first direction X and a pair of sides along the second direction Y. Note that the planar shape of the light guide plate LG is not limited to the illustrated example. One side of the light guide plate LG faces optical elements OE1 and OE2 in the second direction Y.

[0018] Multiple optical sheets OS are arranged between the light guide plate LG and the liquid crystal panel PNL. The optical sheets OS include, for example, prism sheets and diffusion sheets.

[0019] The liquid crystal panel PNL has a display area DA for displaying an image. The display area DA comprises a plurality of pixels PX arranged in a matrix in a first direction X and a second direction Y.

[0020] As shown in the enlarged view in the figure, each pixel PX comprises a switching element SW, a pixel electrode PE, and a common electrode CE. The switching element SW is composed of, for example, a thin-film transistor (TFT) and is electrically connected to the scan line G and the signal line S.

[0021] In one example, the scan line G extends in a first direction X and is electrically connected to a switching element SW at each of the multiple pixels PX arranged in the first direction X. The signal line S extends in a second direction Y, intersects with the scan line G, and is electrically connected to a switching element SW at each of the multiple pixels PX arranged in the second direction Y. Alternatively, the scan line G may extend in the second direction Y, and the signal line S may extend in the first direction X.

[0022] The pixel electrodes PE are electrically connected to the switching element SW. Each pixel electrode PE faces a common electrode CE, and the liquid crystal layer LC is driven by the electric field generated between the pixel electrode PE and the common electrode CE. Capacitance CS is formed, for example, between an electrode at the same potential as the common electrode CE and an electrode at the same potential as the pixel electrode PE.

[0023] Figure 2 is a cross-sectional view showing an example configuration of a display device DSP along line A-B in Figure 1. The liquid crystal panel PNL comprises a first substrate SUB1, a second substrate SUB2, a liquid crystal layer LC, a polarizing plate PL1, and a polarizing plate PL2. The liquid crystal layer LC is sealed between the first substrate SUB1 and the second substrate SUB2. The polarizing plate PL1 is bonded to the first substrate SUB1. The polarizing plate PL2 is bonded to the second substrate SUB2.

[0024] In the lighting device IL, the light guide plate LG has an upper surface TS facing the liquid crystal panel PNL, and a lower surface BS opposite to the upper surface TS. The upper surface TS is parallel to the X-Y plane defined by a first direction X and a second direction Y. The lower surface BS has a plurality of prisms PS arranged at intervals in the second direction Y. Each prism PS has a triangular cross-section and extends in the first direction X. On the lower surface BS, a flat portion is formed between adjacent prisms PS.

[0025] Optical element OE1 has an exit surface SS1 facing the side surface SSL of the light guide plate LG in the second direction Y. Optical element OE2 has an exit surface SS2 facing the side surface SSL of the light guide plate LG in the second direction Y. The side surface SSL, the exit surface SS1, and the exit surface SS2 are each parallel to the X-Z plane defined, for example, by the first direction X and the third direction Z.

[0026] The sum of the first thickness T1 of optical element OE1 and the second thickness T2 of optical element OE2 is equal to or less than the third thickness TLG of the light guide plate LG (T1 + T2 ≤ TLG). The first thickness T1, the second thickness T2, and the third thickness TLG are lengths along the third direction Z. The third thickness TLG is the length along the third direction Z from the flat portion on the lower surface BS to the upper surface TS.

[0027] Figure 3 is a plan view showing the light source units LS1 and LS2 shown in Figure 1.

[0028] The light source unit LS1 comprises a plurality of laser diodes LD11, LD12, and LD13, and a composite element DM1.

[0029] Laser diode LD11 is configured to emit a first color light with a first dominant wavelength λ1. Laser diode LD12 is configured to emit a second color light with a second dominant wavelength λ2, which is different from the first dominant wavelength λ1. Laser diode LD13 is configured to emit a third color light with a third dominant wavelength λ3, which is different from the first dominant wavelength λ1 and the second dominant wavelength λ2.

[0030] The composite element DM1 has, for example, a cubic shape and comprises a first face S11, a second face S12, a third face S13, a fourth face S14, a first reflective surface RS11, and a second reflective surface RS12. The first face S11 and the third face S13 are parallel to each other and also parallel to the X-Z plane and face each other in the second direction Y. The second face S12 and the fourth face S14 are parallel to each other and also parallel to the Y-Z plane and face each other in the first direction X.

[0031] The first surface S11 faces the laser diode LD11, the second surface S12 faces the laser diode LD12, the third surface S13 faces the laser diode LD13, and the fourth surface S14 faces the optical element OE1 and can be the emission surface.

[0032] The first reflective surface RS11 and the second reflective surface RS12 are formed from different dielectric multilayer films. For example, the first reflective surface RS11 is formed to transmit second-color light and reflect first-color light. The second reflective surface RS12 is formed to transmit second-color light and reflect third-color light.

[0033] In such a combining element DM1, the first color light emitted from the laser diode LD11 is reflected by the first reflective surface RS11 and emitted from the fourth surface S14. The second color light emitted from the laser diode LD12 passes through the first reflective surface RS11 and the second reflective surface RS12 and is emitted from the fourth surface S14. The third color light emitted from the laser diode LD13 is reflected by the second reflective surface RS12 and emitted from the fourth surface S14. In other words, the combining element DM1 is configured to combine the first color light, the second color light, and the third color light.

[0034] The light source unit LS2 comprises multiple laser diodes LD21, LD22, and LD23, and a composite element DM2.

[0035] Laser diode LD21 is the same element as laser diode LD11 and is configured to emit first color light at the first dominant wavelength λ1. Laser diode LD22 is the same element as laser diode LD12 and is configured to emit second color light at the second dominant wavelength λ2. Laser diode LD23 is the same element as laser diode LD13 and is configured to emit third color light at the third dominant wavelength λ3.

[0036] The composite element DM2 is the same element as the composite element DM1, has a cubic shape, and comprises a first face S21, a second face S22, a third face S23, a fourth face S24, a first reflective surface RS21, and a second reflective surface RS22. The first face S21 and the third face S23 are parallel to each other and also parallel to the X-Z plane, and face each other in the second direction Y. The second face S22 and the fourth face S24 are parallel to each other and also parallel to the Y-Z plane, and face each other in the first direction X.

[0037] The first surface S21 faces the laser diode LD21, the second surface S22 faces the laser diode LD22, the third surface S23 faces the laser diode LD23, and the fourth surface S24 faces the optical element OE2 and can be the emission surface.

[0038] The first reflective surface RS21 is formed from the same dielectric multilayer film as the first reflective surface RS11 and is configured to transmit second-color light and reflect first-color light. The second reflective surface RS22 is formed from the same dielectric multilayer film as the second reflective surface RS12 and is configured to transmit second-color light and reflect third-color light.

[0039] In such a composite element DM2, the first color light emitted from the laser diode LD21 is reflected by the first reflective surface RS21 and emitted from the fourth surface S24. The second color light emitted from the laser diode LD22 passes through the first reflective surface RS21 and the second reflective surface RS22 and is emitted from the fourth surface S24. The third color light emitted from the laser diode LD23 is reflected by the second reflective surface RS22 and emitted from the fourth surface S24. In other words, the composite element DM2 is configured to combine the first color light, the second color light, and the third color light.

[0040] These composite elements, DM1 and DM2, are sometimes referred to as dichroic mirrors or dichroic prisms.

[0041] When the laser diodes LD11, LD12, and LD13 in the light source unit LS1 are lit simultaneously, the illumination light LI1 emitted from the light source unit LS1 includes a first color light with a first dominant wavelength λ1, a second color light with a second dominant wavelength λ2, and a third color light with a third dominant wavelength λ3.

[0042] When the laser diodes LD21, LD22, and LD23 in the light source unit LS2 are lit simultaneously, the illumination light LI2 emitted from the light source unit LS2 includes a first color light with a first dominant wavelength λ1, a second color light with a second dominant wavelength λ2, and a third color light with a third dominant wavelength λ3.

[0043] In one example, the first dominant wavelength λ1 is in the wavelength range of 400 nm to 500 nm, and the first color light is blue light. The second dominant wavelength λ2 is in the wavelength range of 500 nm to 600 nm, and the second color light is green light. The third dominant wavelength λ3 is in the wavelength range of 600 nm to 700 nm, and the third color light is red light. Both the illumination light LI1 and the illumination light LI2 are white light.

[0044] Note that the respective wavelength ranges of the first dominant wavelength λ1, the second dominant wavelength λ2, and the third dominant wavelength λ3 are not limited to the above examples. For example, the first color light may be red light, the second color light may be blue light, and the third color light may be green light.

[0045] When a field sequential color system is applied, at the timing when the laser diodes LD11 and LD21 are lit simultaneously, both the illumination light LI1 and the illumination light LI2 are the first color light; at the timing when the laser diodes LD12 and LD22 are lit simultaneously, both the illumination light LI1 and the illumination light LI2 are the second color light; and at the timing when the laser diodes LD13 and LD23 are lit simultaneously, both the illumination light LI1 and the illumination light LI2 are the third color light.

[0046] Figure 4 is a diagram for explaining the positional relationship between the combining elements DM1, DM2 and the optical elements OE1, OE2.

[0047] The optical element OE1 has an end face ES1 facing the fourth surface S14 of the combining element DM1 in the first direction X. The optical element OE2 has an end face ES2 facing the fourth surface S24 of the combining element DM2 in the first direction X. Each of the end face ES1 and the end face ES2 is, for example, parallel to the Y-Z plane.

[0048] The end face of the optical element OE1 on the side opposite to the end face ES1 does not face the light source unit LS2 or the combining element DM2. Therefore, the illumination light LI1 emitted from the light source unit LS1 enters the optical element OE1, and the illumination light LI2 emitted from the light source unit LS2 does not enter the optical element OE1.

[0049] The end face of the optical element OE2 opposite to the end face ES2 does not face the light source LS1 or the composite element DM1. Therefore, illumination light LI2 emitted from the light source LS2 is incident on the optical element OE2, but illumination light LI1 emitted from the light source LS1 is not incident on it.

[0050] Figure 5A is a diagram illustrating how illumination light is generated in the lighting device IL shown in Figure 1.

[0051] When the laser diodes LD11, LD12, and LD13 in the light source unit LS1 are lit, the illumination light LI1 synthesized by the combining element DM1 travels along the first direction X and is incident on the optical element OE1. The illumination light LI1 propagating inside the optical element OE1 is reflected towards the light guide plate LG at multiple locations inside the optical element OE1. At this time, the brightness of the reflected light at each location of the optical element OE1 is approximately equal. As a result, the illumination light LI1 is substantially expanded in the first direction X in a plan view and propagates inside the light guide plate LG along the second direction Y.

[0052] Figure 5B is a diagram illustrating how illumination light is generated in the lighting device IL shown in Figure 1.

[0053] When the laser diodes LD21, LD22, and LD23 in the light source unit LS2 are lit, the illumination light LI2 synthesized by the combining element DM2 travels along the first direction X and is incident on the optical element OE2. However, the direction of propagation of the illumination light LI2 is opposite to the direction of propagation of the illumination light LI1 shown in Figure 5A. The illumination light LI2 propagating inside the optical element OE2 is reflected towards the light guide plate LG at multiple locations inside the optical element OE2. At this time, the brightness of the reflected light at each location in the optical element OE2 is approximately equal. As a result, the illumination light LI2 is substantially extended in the first direction X in a plan view and propagates inside the light guide plate LG along the second direction Y.

[0054] Inside the light guide plate LG, illumination light LI1 and illumination light LI2 mix together.

[0055] In particular, the first color light emitted from laser diode LD11 and laser diode LD21, respectively, have the same first dominant wavelength λ1 and mix with each other. This makes it possible to reduce the speckle noise of the laser light emitted from each of the laser diodes LD11 and LD21.

[0056] Similarly, the second-color light emitted from laser diode LD12 and laser diode LD22, respectively, have the same second dominant wavelength λ2 and mix with each other. This reduces the speckle noise of the laser light emitted from each of the laser diodes LD12 and LD22.

[0057] Similarly, the third-color light emitted from laser diode LD13 and laser diode LD23, respectively, have the same first dominant wavelength λ3 and mix with each other. This reduces the speckle noise of the laser light emitted from each of the laser diodes LD13 and LD23.

[0058] Therefore, the brightness can be made uniform within the surface of the light guide plate LG. This reduces brightness unevenness in the illumination light used to illuminate the liquid crystal panel PNL, and improves the display quality of the image displayed in the display area DA.

[0059] Furthermore, in the above-described lighting device IL, the light source units LS1 and LS2 are positioned opposite each other, with optical elements OE1 and OE2 in between. In other words, the light source units LS1 and LS2, which could potentially become heat sources, can be distributed.

[0060] Furthermore, because optical elements OE1 and OE2 overlap in the third direction Z, the frame width in the second direction Y can be reduced compared to the case where optical elements OE1 and OE2 are arranged side by side in the second direction Y.

[0061] Next, other configuration examples of the display device DSP will be described. In the following configuration examples, the same reference numerals will be used for components identical to those in the above configuration examples, and redundant explanations may be omitted as appropriate.

[0062] Figure 6 is a diagram illustrating another example of the configuration of the display device DSP.

[0063] The display device DSP comprises an illumination device IL, a liquid crystal panel PNL1, and a liquid crystal panel PNL2. Liquid crystal panels PNL1 and PNL2 are spaced apart in a first direction X. For example, when liquid crystal panels PNL1 and PNL2 are mounted on a head-mounted display, liquid crystal panel PNL1 is located in front of one of the user's eyes, and liquid crystal panel PNL2 is located in front of the user's other eye. The user's nose is located between liquid crystal panels PNL1 and PNL2.

[0064] The illumination device IL is configured to overlap liquid crystal panels PNL1 and PNL2 in the third direction Z and to illuminate each of the liquid crystal panels PNL1 and PNL2. The illumination device IL comprises a plurality of light source units LS1 and LS2, a plurality of optical elements OE1 and OE2, a plurality of light guide plates LG1 and LG2, and a plurality of optical sheets OS1 and OS2.

[0065] The light source units LS1 and LS2 are arranged to face each other in the first direction X. The light source unit LS1 is configured to emit illumination light LI1 as described above. The light source unit LS2 is configured to emit illumination light LI2 as described above.

[0066] Optical elements OE1 and OE2 are located between light source units LS1 and LS2 in the first direction X, and overlap in the third direction Z. In optical element OE1, one end face ES1 faces the light source unit LS1, and the emission surface SS1 faces the light guide plates LG1 and LG2. In optical element OE2, one end face ES2 faces the light source unit LS2, and the emission surface SS2 faces the light guide plates LG1 and LG2.

[0067] Such optical element OE1 is configured to guide illumination light LI1 emitted from the light source unit LS1 to the light guide plates LG1 and LG2. Similarly, such optical element OE2 is configured to guide illumination light LI2 emitted from the light source unit LS2 to the light guide plates LG1 and LG2.

[0068] Each of the light guide plates LG1 and LG2 is configured in the same manner as the light guide plate LG described above, and has a third thickness TLG as shown in Figure 2. Light guide plate LG1 overlaps the liquid crystal panel PNL1 in the third direction Z. Light guide plate LG2 overlaps the liquid crystal panel PNL2 in the third direction Z. One side surface of light guide plate LG1 and one side surface of light guide plate LG2 face optical elements OE1 and OE2 in the second direction Y.

[0069] Multiple optical sheets OS1 are arranged between the light guide plate LG1 and the liquid crystal panel PNL1. Multiple optical sheets OS2 are arranged between the light guide plate LG2 and the liquid crystal panel PNL2. Optical sheets OS1 and OS2 include, for example, prism sheets and diffusion sheets.

[0070] Liquid crystal panel PNL1 has a display area DA1 for displaying images. Liquid crystal panel PNL2 has a display area DA2 for displaying images. Each of the display areas DA1 and DA2 has a plurality of pixels PX arranged in a matrix in the first direction X and the second direction Y, similar to the display area DA shown in Figure 1, but the details are omitted here.

[0071] In this configuration example, as explained with reference to Figure 2, the sum of the first thickness T1 of optical element OE1 and the second thickness T2 of optical element OE2 is equal to or smaller than the third thickness TLG of light guide plates LG1 and LG2 (T1 + T2 ≤ TLG).

[0072] Figure 7A is a diagram illustrating how illumination light is generated in the lighting device IL shown in Figure 6.

[0073] When the laser diodes LD11, LD12, and LD13 in the light source unit LS1 are lit, the illumination light LI1 synthesized by the combining element DM1 travels along the first direction X and is incident on the optical element OE1. The illumination light LI1 propagating inside the optical element OE1 is reflected at multiple points inside the optical element OE1 toward the light guide plates LG1 and LG2, and is substantially extended in the first direction X in a plan view. Such illumination light LI1 propagates along the second direction Y inside each of the light guide plates LG1 and LG2.

[0074] Figure 7B is a diagram illustrating how illumination light is generated in the lighting device IL shown in Figure 6.

[0075] When the laser diodes LD21, LD22, and LD23 in the light source unit LS2 are lit, the illumination light LI2 synthesized by the combining element DM2 propagates along the first direction X and enters the optical element OE2. The illumination light LI2 propagating inside the optical element OE2 is reflected at multiple points inside the optical element OE2 toward the light guide plates LG1 and LG2, and is substantially extended in the first direction X in a plan view. Such illumination light LI2 propagates along the second direction Y inside each of the light guide plates LG1 and LG2.

[0076] Inside each of the light guide plates LG1 and LG2, the illumination light LI1 and illumination light LI2 mix together. This allows for the reduction of speckle noise in the laser light, similar to the configuration example described above.

[0077] Therefore, the brightness can be made uniform within the surface of the light guide plate LG. This reduces brightness unevenness in the illumination light used to illuminate the liquid crystal panel PNL1, and improves the display quality of the image displayed in the display area DA1. Similarly, brightness unevenness in the illumination light used to illuminate the liquid crystal panel PNL2 is reduced, and improves the display quality of the image displayed in the display area DA2.

[0078] Furthermore, the light sources LS1 and LS2, and optical elements OE1 and OE2 of the illumination device IL are shared between the liquid crystal panel for the right eye and the liquid crystal panel for the left eye. Therefore, compared to the case where separate illumination devices are provided for each of the two liquid crystal panels, the number of parts can be reduced, and costs can be reduced.

[0079] Figure 8 is a diagram illustrating another example configuration of the display device DSP.

[0080] The display device DSP comprises an illumination device IL and a liquid crystal panel PNL. The illumination device IL is configured to overlap the liquid crystal panel PNL in the third direction Z and to illuminate the liquid crystal panel PNL.

[0081] The lighting device IL comprises multiple light source units LS1 and LS2, an optical element OE, a light guide plate LG, and multiple optical sheets OS.

[0082] The light source units LS1 and LS2 are aligned in the second direction Y. Light source unit LS1 is configured to emit illumination light LI1 as described above. Light source unit LS2 is configured to emit illumination light LI2 as described above.

[0083] The optical element OE has an end face ES and an output face SS. The end face ES faces the light source units LS1 and LS2 in a first direction X. The output face SS faces the light guide plate LG in a second direction Y. Such an optical element OE is configured to guide the illumination light LI1 emitted from the light source unit LS1 and the illumination light LI2 emitted from the light source unit LS2 to the light guide plate LG, respectively.

[0084] The light guide plate LG overlaps the liquid crystal panel PNL in the third direction Z. One side of the light guide plate LG faces the optical element OE in the second direction Y.

[0085] Multiple optical sheets OS are arranged between the light guide plate LG and the liquid crystal panel PNL. The optical sheets OS include, for example, prism sheets and diffusion sheets.

[0086] The liquid crystal panel PNL has a display area DA for displaying images. Similar to the display area DA shown in Figure 1, the display area DA comprises a plurality of pixels PX arranged in a matrix in the first direction X and the second direction Y, but details are omitted here.

[0087] Figure 9 is a plan view showing the light source units LS1 and LS2 shown in Figure 8.

[0088] The light source unit LS1 comprises a plurality of laser diodes LD11, LD12, and LD13, and a composite element DM1. The laser diodes LD11, LD12, and LD13 are aligned in the first direction X.

[0089] Laser diode LD11 is configured to emit a first color light with a first dominant wavelength λ1. Laser diode LD12 is configured to emit a second color light with a second dominant wavelength λ2. Laser diode LD13 is configured to emit a third color light with a third dominant wavelength λ3.

[0090] The composite element DM1 has, for example, the shape of a rectangular parallelepiped and comprises a first face S11, a second face S12, a third face S13, a fourth face S14, a first reflective surface RS11, a second reflective surface RS12, and a third reflective surface RS13. The first face S11 and the third face S13 are parallel to each other and also parallel to the X-Z plane and face each other in the second direction Y. The second face S12 and the fourth face S14 are parallel to each other and also parallel to the Y-Z plane and face each other in the first direction X.

[0091] The first surface S11 faces the laser diode LD11, laser diode LD12, and laser diode LD13 in the second direction Y. The fourth surface S14 faces the end face ES of the optical element OE in the first direction X.

[0092] The first reflective surface RS11, the second reflective surface RS12, and the third reflective surface RS13 are formed from different dielectric multilayer films. For example, the first reflective surface RS11 is formed to transmit the second and third color light and reflect the first color light. The second reflective surface RS12 is formed to transmit the third color light and reflect the second color light. The third reflective surface RS13 is formed to reflect the third color light.

[0093] In such a composite element DM1, the first color light emitted from the laser diode LD11 is reflected by the first reflective surface RS11 and emitted from the fourth surface S14. The second color light emitted from the laser diode LD12 is reflected by the second reflective surface RS12, passes through the first reflective surface RS11, and is emitted from the fourth surface S14. The third color light emitted from the laser diode LD13 is reflected by the third reflective surface RS13, passes through the second reflective surface RS12 and the first reflective surface RS11 in sequence, and is emitted from the fourth surface S14. In other words, the composite element DM1 is configured to combine the first color light, the second color light, and the third color light.

[0094] The light source unit LS2 comprises a plurality of laser diodes LD21, LD22, and LD23, and a composite element DM2. The laser diodes LD21, LD22, and LD23 are aligned in the first direction X.

[0095] Laser diode LD21 is the same element as laser diode LD11 and is configured to emit first color light at the first dominant wavelength λ1. Laser diode LD22 is the same element as laser diode LD12 and is configured to emit second color light at the second dominant wavelength λ2. Laser diode LD23 is the same element as laser diode LD13 and is configured to emit third color light at the third dominant wavelength λ3.

[0096] The composite element DM2 is the same element as the composite element DM1, has a rectangular parallelepiped shape, and comprises a first face S21, a second face S22, a third face S23, a fourth face S24, a first reflective surface RS21, a second reflective surface RS22, and a third reflective surface RS23. The first face S21 and the third face S23 are parallel to each other and also parallel to the X-Z plane, and face each other in the second direction Y. The second face S22 and the fourth face S24 are parallel to each other and also parallel to the Y-Z plane, and face each other in the first direction X. In the illustrated example, the third face S23 of the composite element DM2 faces the third face S13 of the composite element DM1 in the second direction Y.

[0097] The first surface S21 faces the laser diodes LD21, LD22, and LD23 in the second direction Y. The fourth surface S24 faces the end face ES of the optical element OE in the first direction X.

[0098] The first reflective surface RS21 is formed from the same dielectric multilayer film as the first reflective surface RS11 and is configured to transmit the second and third color light and reflect the first color light. The second reflective surface RS22 is formed from the same dielectric multilayer film as the second reflective surface RS12 and is configured to transmit the third color light and reflect the second color light. The third reflective surface RS23 is formed from the same dielectric multilayer film as the third reflective surface RS13 and is configured to reflect the third color light.

[0099] In such a composite element DM2, the first color light emitted from the laser diode LD21 is reflected by the first reflective surface RS21 and emitted from the fourth surface S24. The second color light emitted from the laser diode LD22 is reflected by the second reflective surface RS22, passes through the first reflective surface RS21, and is emitted from the fourth surface S24. The third color light emitted from the laser diode LD23 is reflected by the third reflective surface RS23, passes through the second reflective surface RS22 and the first reflective surface RS21 in sequence, and is emitted from the fourth surface S24. In other words, the composite element DM2 is configured to combine the first color light, the second color light, and the third color light.

[0100] When the laser diodes LD11, LD12, and LD13 in the light source unit LS1 are lit simultaneously, the illumination light LI1 emitted from the light source unit LS1 includes a first color light with a first dominant wavelength λ1, a second color light with a second dominant wavelength λ2, and a third color light with a third dominant wavelength λ3.

[0101] When the laser diodes LD21, LD22, and LD23 in the light source unit LS2 are lit simultaneously, the illumination light LI2 emitted from the light source unit LS2 includes a first color light with a first dominant wavelength λ1, a second color light with a second dominant wavelength λ2, and a third color light with a third dominant wavelength λ3.

[0102] The wavelength ranges for the first major wavelength λ1, the second major wavelength λ2, and the third major wavelength λ3 are, for example, as described above.

[0103] The sum of the first width W1 of composite element DM1 and the second width W2 of composite element DM2 is equal to or less than the third width WOE of optical element OE (W1 + W2 ≤ WOE). Note that the first width W1, the second width W2, and the third width WOE are lengths along the second direction Y in a plan view.

[0104] Figure 10 is a diagram illustrating how illumination light is generated in the lighting device IL shown in Figure 8.

[0105] When the laser diodes LD11, LD12, and LD13 in the light source unit LS1 are lit, the illumination light LI1 synthesized by the combining element DM1 propagates along the first direction X and enters the optical element OE. The illumination light LI1 propagating inside the optical element OE is reflected at multiple points inside the optical element OE toward the light guide plate LG, and in a plan view, is substantially extended in the first direction X. Such illumination light LI1 propagates inside the light guide plate LG along the second direction Y.

[0106] When the laser diodes LD21, LD22, and LD23 in the light source unit LS2 are lit, the illumination light LI2 synthesized by the combining element DM2 propagates along the first direction X and enters the optical element OE. The illumination light LI2 propagating inside the optical element OE is reflected at multiple points inside the optical element OE toward the light guide plate LG and is substantially extended in the first direction X in a plan view. Such illumination light LI2 propagates inside the light guide plate LG along the second direction Y.

[0107] Inside the light guide plate LG, illumination light LI1 and illumination light LI2 mix together. This allows for the reduction of speckle noise in the laser light, similar to the configuration example described above.

[0108] The same effects can be obtained in this configuration example as in the above example.

[0109] Next, we will describe other examples of light source configurations applicable to the light source units LS1 and LS2 of the display device DSP shown in Figures 1, 6, and 8, respectively.

[0110] Figure 11 is a plan view showing another example of the configuration of the light source unit LS.

[0111] The light source unit LS comprises multiple laser diodes LD1, LD2, and LD3, and a composite element DM. The laser diodes LD1 and LD3 are aligned in the first direction X.

[0112] Laser diode LD1 corresponds to laser diodes LD11 and LD21 and is configured to emit first color light at a first dominant wavelength λ1. Laser diode LD2 corresponds to laser diodes LD12 and LD22 and is configured to emit second color light at a second dominant wavelength λ2. Laser diode LD3 corresponds to laser diodes LD13 and LD23 and is configured to emit third color light at a third dominant wavelength λ3.

[0113] The composite element DM has, for example, the shape of a rectangular parallelepiped and comprises a first face S1, a second face S2, a third face S3, a fourth face S4, a first reflective surface RS1, and a second reflective surface RS2. The first face S1 and the third face S3 are parallel to each other and also parallel to the X-Z plane and face each other in the second direction Y. The second face S12 and the fourth face S14 are parallel to each other and also parallel to the Y-Z plane and face each other in the first direction X.

[0114] The first surface S1 faces laser diode LD1 and laser diode LD3 in the second direction Y. The second surface S2 faces laser diode LD2 in the first direction X. The fourth surface S4 faces optical element OE in the first direction X.

[0115] The first reflective surface RS1 and the second reflective surface RS2 are formed from different dielectric multilayer films. For example, the first reflective surface RS1 is formed to transmit the second and third color light and reflect the first color light. The second reflective surface RS2 is formed to transmit the second color light and reflect the third color light.

[0116] In such a composite element DM, the first color light emitted from the laser diode LD1 is reflected by the first reflective surface RS1 and emitted from the fourth surface S4. The second color light emitted from the laser diode LD2 passes through the first reflective surface RS1 and the second reflective surface RS12 and is emitted from the fourth surface S14. The third color light emitted from the laser diode LD3 is reflected by the second reflective surface RS12, passes through the first reflective surface RS11 and is emitted from the fourth surface S14. In other words, the composite element DM1 is configured to combine the first color light, the second color light, and the third color light.

[0117] A light source unit with this configuration can be used as the light source unit LS1 described above, or as the light source unit LS2 described above.

[0118] For example, in the above embodiment, the light source unit LS1 corresponds to the first light source unit, the illumination light LI1 corresponds to the first illumination light, the light source unit LS2 corresponds to the second light source unit, and the illumination light LI2 corresponds to the second illumination light.

[0119] Optical element OE1 corresponds to the first optical element, end face ES1 corresponds to the first end face, and exit surface SS1 corresponds to the first exit surface. Optical element OE2 corresponds to the second optical element, end face ES2 corresponds to the second end face, and exit surface SS2 corresponds to the second exit surface.

[0120] Liquid crystal panel PNL1 corresponds to the first liquid crystal panel, and liquid crystal panel PNL2 corresponds to the second liquid crystal panel. Light guide plate LG1 corresponds to the first light guide plate, and light guide plate LG2 corresponds to the second light guide plate.

[0121] Laser diodes LD11 and LD21 correspond to the first laser diode, laser diodes LD12 and LD22 correspond to the second laser diode, and laser diodes LD13 and LD23 correspond to the third laser diode.

[0122] According to the embodiments described above, a display device capable of improving display quality can be provided.

[0123] While several embodiments of this disclosure have been described, these embodiments are presented as examples only and are not intended to limit the scope of the disclosure. These novel embodiments can be implemented in a variety of other forms, and various omissions, substitutions, and modifications are permitted without departing from the gist of the disclosure. These embodiments and their variations are included in the scope and gist of the disclosure, as well as in the disclosures described in the claims and their equivalents.

[0124] DSP... Display device PNL, PNL1, PNL2... Liquid crystal panel IL... Illumination device LG, LG1, LG2... Light guide plate LS, LS1, LS2... Light source unit LD11, LD12, LD13, LD21, LD22, LD23... Laser diode OE, OE1, OE2... Optical element DM, DM1, DM2... Composite element

Claims

1. A display device comprising: a liquid crystal panel having a display area for displaying an image; and an illumination device configured to illuminate the liquid crystal panel, wherein the illumination device comprises: a light guide plate overlapping the liquid crystal panel; a first light source unit configured to emit first illumination light; a second light source unit configured to emit second illumination light; a first optical element located between the first light source unit and the second light source unit, having a first end face facing the first light source unit and a first emission surface facing the light guide plate, and configured to guide the first illumination light to the light guide plate; and a second optical element located between the first light source unit and the second light source unit, overlapping the first optical element, having a second end face facing the second light source unit and a second emission surface facing the light guide plate, and configured to guide the second illumination light to the light guide plate.

2. The display device according to claim 1, wherein the sum of the first thickness of the first optical element and the second thickness of the second optical element is equal to or less than the third thickness of the light guide plate.

3. A first liquid crystal panel having a display area for displaying an image; a second liquid crystal panel having a display area for displaying an image; and an illumination device configured to illuminate the first liquid crystal panel and the second liquid crystal panel, wherein the illumination device comprises: a first light guide plate overlapping the first liquid crystal panel; a second light guide plate overlapping the second liquid crystal panel; a first light source unit configured to emit first illumination light; a second light source unit configured to emit second illumination light; and a first optical element located between the first light source unit and the second light source unit, having a first end face facing the first light source unit and a first emission surface facing the first light guide plate and the second light guide plate, and configured to guide the first illumination light to the first light guide plate and the second light guide plate. A display device comprising: a second optical element located between the first light source unit and the second light source unit, overlapping the first optical element, having a second end face facing the second light source unit, and a second emission surface facing the first light guide plate and the second light guide plate, and configured to guide the second illumination light to the first light guide plate and the second light guide plate.

4. The display device according to claim 3, wherein the sum of the first thickness of the first optical element and the second thickness of the second optical element is equal to or less than the third thickness of the first light guide plate and the second light guide plate, respectively.

5. The display device according to claim 1 or 3, wherein each of the first light source unit and the second light source unit comprises: a first laser diode configured to emit first color light of a first dominant wavelength; a second laser diode configured to emit second color light of a second dominant wavelength different from the first dominant wavelength; a third laser diode configured to emit third color light of a third dominant wavelength different from the first and second dominant wavelengths; and a combining element configured to combine the first color light, the second color light, and the third color light, wherein the combining element comprises: a first surface facing the first laser diode; a second surface facing the second laser diode; a third surface facing the first surface and facing the third laser diode; a fourth surface facing the second surface and serving as an emission surface; a first reflective surface that transmits the second color light and reflects the first color light; and a second reflective surface that transmits the second color light and reflects the third color light.

6. The display device according to claim 1 or 3, wherein the end face of the first optical element opposite to the first end face does not face the second light source, and the end face of the second optical element opposite to the second end face does not face the first light source.

7. A display device comprising: a liquid crystal panel having a display area for displaying an image; and an illumination device configured to illuminate the liquid crystal panel, wherein the illumination device comprises: a light guide plate overlapping the liquid crystal panel; a first light source unit configured to emit a first illumination light; a second light source unit configured to emit a second illumination light; and an optical element having a first end face facing the first light source unit and the second light source unit, and a first emission surface facing the light guide plate, and configured to guide the first illumination light and the second illumination light to the light guide plate.

8. The display device according to claim 7, wherein each of the first light source unit and the second light source unit comprises: a first laser diode configured to emit first color light of a first dominant wavelength; a second laser diode configured to emit second color light of a second dominant wavelength different from the first dominant wavelength; a third laser diode configured to emit third color light of a third dominant wavelength different from the first and second dominant wavelengths; and a combining element configured to combine the first color light, the second color light, and the third color light, wherein the sum of the first width of the combining element in the first light source unit and the second width of the combining element in the second light source unit is equal to or smaller than the third width of the optical element.

9. The display device according to claim 8, wherein the composite element comprises a first surface facing the first laser diode, the second laser diode, and the third laser diode, a second surface, a third surface facing the first surface, a fourth surface facing the second surface and serving as an emission surface, a first reflective surface that transmits the second and third color light and reflects the first color light, a second reflective surface that transmits the third color light and reflects the second color light, and a third reflective surface that reflects the third color light.

10. The display device according to any one of claims 1, 3, or 7, wherein each of the first light source unit and the second light source unit comprises: a first laser diode configured to emit first color light of a first dominant wavelength; a second laser diode configured to emit second color light of a second dominant wavelength different from the first dominant wavelength; a third laser diode configured to emit third color light of a third dominant wavelength different from the first and second dominant wavelengths; and a combining element configured to combine the first color light, the second color light, and the third color light, wherein the combining element comprises: a first surface facing the first laser diode and the third laser diode; a second surface facing the second laser diode; a third surface facing the first surface; a fourth surface facing the second surface and serving as an emission surface; a first reflective surface that transmits the second color light and reflects the first color light; and a second reflective surface that transmits the second color light and reflects the third color light.

Images