Image display apparatus

Abstract

To provide an image display device capable of suppressing luminance unevenness of display.SOLUTION: The image display device 1 includes a display unit 2 that emits display light L, and an optical unit 3 that reflects the display light L and projects the display light L on a display member 103, the display unit 2 includes a metal circuit board 4 on which light-emitting elements 41 are mounted, a display unit 5 that receives light emitted by the light-emitting elements 41 and emits the display light L, and a control unit 7 that controls light emission luminance of the light-emitting elements 41, and the light-emitting elements 41 are arranged in a plurality on the metal circuit board 4, the control unit 7 is configured to be able to adjust the light emission luminance of the light emitting elements 41 individually for each column of the array.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to an image display device. [Background technology]

[0002] Conventionally, as an image display device, there has been known an image display device that includes a display unit (display), a plurality of light sources that illuminate the display unit, and a circuit board on which the plurality of light sources are mounted, as described in Patent Document 1. In this image display device, a backlight is formed by arranging a plurality of light sources in each direction that intersects the surface of the circuit board, and light is directed onto a display unit such as a liquid crystal display to generate display light. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-165624 Summary of the Invention [Problem to be solved by the invention]

[0004] The image display device described in Patent Document 1 has room for improvement in that it is prone to uneven display brightness. For example, even if the same current is passed through multiple light sources, the brightness may be uneven across the display range of the display unit, with the brightness being higher in the central area.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an image display device that can suppress unevenness in display brightness. [Means for solving the problem]

[0006] That is, the image display device of the present invention comprises a display unit that emits display light and an optical section that reflects the display light and projects it onto a display member, the display unit having a circuit board on which light-emitting elements are mounted, a display section that receives light emitted by the light-emitting elements and emits the display light, and a control section that controls the light emission brightness of the light-emitting elements, the light-emitting elements being arranged in multiple rows on the circuit board, and the control section being configured to be able to adjust the light emission brightness of the light-emitting elements individually for each column of the arrangement. [Effects of the Invention]

[0007] According to the image display device of the present invention, uneven brightness of the display can be suppressed. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing a schematic configuration of an image display device according to an embodiment. [Figure 2] FIG. 2 is a perspective view of a display unit of the image display device according to the embodiment. [Figure 3] FIG. 3 is an exploded perspective view of a display unit of the image display device according to the embodiment. [Figure 4] FIG. 4 is a perspective view showing an outline of a metal circuit board of the image display device according to the embodiment. [Figure 5] FIG. 5 is an explanatory diagram of the arrangement of light-emitting elements in the image display device according to the embodiment. [Figure 6] FIG. 6 is an explanatory diagram of current values ​​of light-emitting elements of the image display device according to the embodiment. [Figure 7] FIG. 7 is an explanatory diagram of the display luminance of the display unit of the image display device according to the embodiment. [Figure 8] FIG. 8 is an explanatory diagram of a display state of the display unit of the image display device according to the embodiment. [Figure 9] FIG. 9 is an explanatory diagram of current values ​​of light-emitting elements in an image display device of a comparative example. [Figure 10] FIG. 10 is an explanatory diagram of the display brightness of the display unit in the image display device of the comparative example. [Figure 11] FIG. 11 is an explanatory diagram of a display state of a display unit in an image display device of a comparative example. [Figure 12] FIG. 12 is an explanatory diagram of current values ​​of light-emitting elements in an image display device of a comparative example. [Figure 13] FIG. 13 is an explanatory diagram of the display luminance of the display unit in the image display device of the comparative example. [Figure 14] FIG. 14 is an explanatory diagram of a display state of a display unit in an image display device of a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to these embodiments. Furthermore, the components in the following embodiments include those that are easily replaceable by those skilled in the art, or those that are substantially the same.

[0010] [Embodiment] This embodiment relates to an image display device. In the following description, of a first direction, a second direction, and a third direction that intersect with one another, the first direction is referred to as the "front-rear direction X," the second direction is referred to as the "vehicle width direction Y," and the third direction is referred to as the "height direction Z." Here, the front-rear direction X, the vehicle width direction Y, and the height direction Z are perpendicular to one another. The front-rear direction X corresponds to the front-rear direction of a vehicle on which the image display device is mounted. The vehicle width direction Y corresponds to the vehicle width direction of a vehicle on which the image display device is mounted. The vehicle width direction Y and the height direction Z correspond to intersecting directions that intersect with the front-rear direction X. Unless otherwise specified, each direction used in the following description represents a direction when each part is mounted on a vehicle. Note that orthogonal here includes nearly perpendicular.

[0011] As shown in FIG. 1, the image display device 1 is a device installed in a vehicle 100 and displays an image, and is, for example, a head-up display device that projects display light L onto a display member 103 of the vehicle 100 to display a virtual image S. The image display device 1 projects the display light L onto the display member 103 in the vehicle 100, causing the driver of the vehicle 100 to recognize a virtual image S in front of the eye point EP. The display member 103 is, for example, a windshield. The image display device 1 is disposed below the display member 103, and is installed, for example, in an instrument panel provided on the dashboard. The eye point EP is assumed in advance to be the driver's viewpoint.

[0012] The image display device 1 includes a display unit 2, an optical unit 3, and a control unit 7. The display unit 2 and the optical unit 3 are housed in or installed in a housing 11, and emit display light L from an opening 12 toward a display member 103. The control unit 7 is installed, for example, outside the housing 11, and is electrically connected to the display unit 2.

[0013] The optical unit 3 is an optical system unit that reflects the display light L and guides it toward the display member 103, and is configured, for example, by a mirror 31. The mirror 31 reflects the display light L emitted from the display unit 2 and projects the display light L onto the display member 103 through the opening 12. The mirror 31 has, for example, a concave reflective surface, which can enlarge an image. The shape of the reflective surface may be, for example, a free-form surface, which can correct distortion and aberration of the image. While FIG. 1 shows a case where the optical unit 3 is configured by one mirror 31, the optical unit 3 may be configured by multiple mirrors and reflect the display light L multiple times.

[0014] As shown in FIGS. 2 and 3 , the display unit 2 generates and outputs display light L and includes a metal circuit board 4, a display unit 5, and wiring members 6. For example, the display unit 2 is configured by attaching a cover 21 to the metal circuit board 4, and sequentially arranging a condenser lens 22, a light distribution lens 23, a case 24, a frame member 25, a sheet member 26, a sheet member 27, and the display unit 5 between the metal circuit board 4 and the cover 21. In the drawings, the depth direction of the display unit 2 is referred to as the "unit longitudinal direction D1," the width direction is referred to as the "unit width direction D2," and the height direction is referred to as the "unit height direction D3." The unit longitudinal direction D1, the unit width direction D2, and the unit height direction D3 are perpendicular to one another. The unit longitudinal direction D1 is typically a direction along the emission direction of the display light L or a direction along the thickness direction of the metal circuit board 4, and when installed in the vehicle 100, it is a direction that obliquely intersects the longitudinal direction X shown in FIG. 1 . The unit width direction D2 is typically a direction along the vehicle width direction Y shown in FIG.

[0015] The metal circuit board 4 is a circuit board on which the light-emitting elements 41 are mounted and is a component constituting a backlight. For example, the metal circuit board 4 has a plate-shaped metal member 42, and the light-emitting elements 41 are mounted on the metal member 42 via an insulating layer. The metal member 42 is stacked in the thickness direction of the metal circuit board 4 and is formed to be the same size as the main surface 40 of the metal circuit board 4. Here, "same size" includes "approximately the same size." The metal member 42 is, for example, a plate material primarily made of aluminum. Examples of aluminum-based plate materials include aluminum plate materials and aluminum alloy plate materials. In the image display device 1 according to this embodiment, by using the metal circuit board 4 as the circuit board on which the light-emitting elements 41 are mounted, heat generated by the light-emitting elements 41 can be diffused through the metal member 42, thereby preventing the light-emitting elements 41 from becoming overheated. Furthermore, the image display device 1 according to this embodiment can improve heat dissipation by using the metal circuit board 4, eliminating the need for heat dissipation fins and the like, thereby enabling the device to be more compact.

[0016] The main surface 40 of the metal circuit board 4 is the surface of the plate-shaped metal circuit board 4, and is a surface formed in a direction intersecting the thickness direction. The thickness direction is a direction along the unit front-rear direction D1. The light-emitting elements 41 are light sources that emit light to serve as backlight, and a plurality of light-emitting elements 41 are arranged on the main surface 40 of the metal circuit board 4. For example, LEDs (Light Emitting Diodes) are used as the light-emitting elements 41. For example, chip components are used and surface-mounted. The light-emitting elements 41 may be components that have lead wires and are insert-mounted, or may be light-emitting components other than LEDs.

[0017] The cover 21 is a box-shaped component with an opening on the surface facing the metal circuit board 4, and is attached to, for example, the main surface 40 of the metal circuit board 4 and fixed with screws 28. An exit window 211 is formed in the cover 21, allowing the display light L to be emitted. In addition, flange portions 212 are formed on both ends of the cover 21 in the unit width direction D2, allowing the cover 21 to be fixed to the housing 11 or a member attached to the housing 11.

[0018] The condensing lens 22 is a lens that condenses light emitted from the light-emitting elements 41 and is made of a light-transmitting member. The condensing lens 22 has a plurality of lens portions 221 corresponding to the plurality of light-emitting elements 41, and condenses light emitted from each light-emitting element 41 using the respective lens portions 221. Each lens portion 221 has a flat incident surface and a convexly curved exit surface, and is formed facing the light-emitting element 41. By providing a lens portion 221 for each of the plurality of light-emitting elements 41 in this manner, the light distribution angle or illumination angle of light emitted from the light-emitting element 41 can be set small, and the distance between the condensing lens 22 and the light distributing lens 23 can be shortened. Therefore, the image display device 1 according to this embodiment can configure a thin backlight unit including the light-emitting elements 41, the condensing lens 22, and the light distributing lens 23.

[0019] The light distributing lens 23 is a lens that adjusts the traveling direction of the light emitted from the condensing lens 22 to a predetermined direction, and is made of a light-transmitting member. The light distributing lens 23 is disposed opposite the condensing lens 22.

[0020] The case 24 is provided so as to cover the condensing lens 22 and the light distributing lens 23 between it and the metal circuit board 4. For example, the case 24 is attached integrally with the metal circuit board 4, the condensing lens 22, the light distributing lens 23, and the cover 21 by screws 28. In other words, the screws 28 are inserted sequentially through the metal circuit board 4, the condensing lens 22, the light distributing lens 23, and the case 24, and are screwed into the cover 21. An opening 241 is formed in the case 24, and the opening 241 is capable of guiding light emitted from the light distributing lens 23 along the unit front-rear direction D1.

[0021] Between the case 24 and the cover 21, there are provided a frame material 25, a sheet material 26, a sheet material 27, and a display unit 5. The sheet materials 26 and 27 are optical sheets, and for example, a diffusion sheet, a light-collecting sheet, or the like is used.

[0022] The display unit 5 is disposed opposite the light-emitting element 41 and is a device that receives light emitted from the light-emitting element 41 and emits display light L. For example, the display unit 5 emits display light L by transmitting light that has been optically processed and emitted from the light-emitting element 41. Specifically, a light-transmitting TFT liquid crystal (Thin Film Transistor Liquid Crystal Display) is used as the display unit 5.

[0023] A wiring member 6 is connected to the display unit 5. The wiring member 6 is a wiring material for controlling the display unit 5, and electrically connects the display unit 5 and the metal circuit board 4. The wiring member 6 is made of a planar circuit board, and for example, a flexible printed circuit board is used. The wiring member 6 extends from the connection position with the display unit 5 to the outside of the cover 21 along the unit front-rear direction D1 and is connected to the metal circuit board 4. In other words, the wiring member 6 is connected to a connector 43 mounted on the metal circuit board 4.

[0024] As shown in Fig. 4, the metal circuit board 4 is formed in the shape of a rectangular plate, and has light-emitting elements 41 mounted on a main surface 40. A plurality of the light-emitting elements 41 are arranged in each of two intersecting directions. For example, a plurality of the light-emitting elements 41 are arranged along the unit width direction D2 and the unit height direction D3. Specifically, five light-emitting elements 41 are arranged along the unit width direction D2, and three light-emitting elements 41 are arranged along the unit height direction D3, for a total of 15 light-emitting elements 41.

[0025] That is, as shown in FIG. 5, the light-emitting elements 41 are arranged in five rows, L11, L12, L13, L14, and L15, along the unit width direction D2, and in three rows, L21, L22, and L23, along the unit height direction D3. In the unit width direction D2, rows L11 and L15 are end rows, rows L12 and L14 are rows closer to the center than the end rows, and row L13 is a central row. Rows L21 and L23 are end rows, and row L22 is a central row. In addition, in the unit height direction D3, rows L21 and L23 are end rows, and row L22 is a central row. Note that the number and arrangement of the light-emitting elements 41 are not limited to those shown in FIG. 4.

[0026] The light emitting elements 41 are provided so that the light emission brightness can be controlled individually. That is, the control unit 7 controls the light emission brightness by adjusting the current that is passed through the light emitting elements 41 individually. For example, the control unit 7 can adjust the light emission brightness of the light emitting elements 41 individually for each column of the array. That is, the control unit 7 adjusts the light emission brightness of the light emitting elements 41 for each column, and can make the light emission brightness of the light emitting elements 41 in the same column the same brightness. Note that the light emitting elements 41 in the same column may also be adjusted to different light emission brightnesses. The light emitting elements 41 are connected to the control unit 7 via a light emission control connector 44. The light emission control connector 44 is mounted on the metal circuit board 4, and is connected to the light emitting elements 41 by wiring material (not shown). Note that in Figs. 4 and 5, the connector 43 and the light emission control connector 44 are shown in outline.

[0027] As shown in FIG. 6 , the light-emitting elements 41 are adjusted so that the current decreases from the ends of the array toward the center. That is, the control unit 7 adjusts the light-emitting luminance by decreasing the current value applied to the light-emitting elements 41 from the ends of the array toward the center. Specifically, in columns L11, L12, L13, L14, and L15 in the unit width direction D2, the current value applied to the light-emitting elements 41 is decreased from the ends of the array toward the center, thereby adjusting the light-emitting luminance. That is, the light-emitting elements 41 in column L12 receive a smaller current value from the light-emitting elements 41 in column L11, and the light-emitting elements 41 in column L13 receive a smaller current value from the light-emitting elements 41 in column L12. Furthermore, the light-emitting elements 41 in column L14 receive a smaller current value from the light-emitting elements 41 in column L15, and the light-emitting elements 41 in column L13 receive a smaller current value from the light-emitting elements 41 in column L12.

[0028] As shown in Fig. 7, the display brightness of the display unit 5 is high in the center corresponding to column 13 of the light-emitting elements 41 and decreases toward the ends. The display brightness of the display unit 5 corresponding to the ends of columns L11 and L15 of the light-emitting elements 41 is higher than the reference brightness B. For this reason, as shown in Fig. 8, although the display brightness is high in the center of the display range of the display unit 5, the display brightness at the ends also exceeds the reference brightness B, and brightness unevenness is suppressed.

[0029] As shown in FIG. 4, the metal circuit board 4 has an arrangement area 45 and a non-arrangement area 46. The non-arrangement area 46 is located at a higher position on the metal circuit board 4 than the arrangement area 45 in the vertical direction. In FIG. 4, the vertical direction is along the height direction Z, which is inclined with respect to the unit height direction D3. The metal circuit board 4 is located in a direction that intersects with the horizontal direction. That is, the metal circuit board 4 is located so that the normal direction of the main surface 40 intersects with the vertical direction. The normal direction of the main surface 40 is the unit front-rear direction D1, and the vertical direction is the height direction Z. The non-arrangement area 46 can be located at a higher position than the arrangement area 45 as long as the metal circuit board 4 is not located so that the normal direction of the main surface 40 is the vertical direction. In other words, when the metal circuit board 4 is arranged so that the main surface 40 is perpendicular to the vertical direction, the non-placement area 46 and the placement area 45 are at the same height in the vertical direction, but when the metal circuit board 4 is arranged so that the main surface 40 is not perpendicular to the vertical direction, the non-placement area 46 can be located at a higher position than the placement area 45.

[0030] The arrangement region 45 is a region on the main surface 40 of the metal circuit board 4 where the light emitting element 41 is arranged. The non-arrangement region 46 is a region on the main surface 40 of the metal circuit board 4 other than the arrangement region 45. For example, the arrangement region 45 is a region on the main surface 40 of the metal circuit board 4 below an upper end position 47 of the light emitting element 41 that is arranged at the top in the unit height direction D3. The non-arrangement region 46 is a region on the main surface 40 of the metal circuit board 4 above the upper end position 47. In other words, the light emitting element 41 is mounted on the metal circuit board 4 with its position biased downward. For example, the non-arrangement region 46 is set to be larger than the arrangement region 45.

[0031] The metal circuit board 4 is mounted with a connector 43 connected to the wiring member 6, together with the light-emitting element 41. The connector 43 is not a heat-generating component, and therefore it is conceivable to mount it on, for example, a circuit board that does not have the metal member 42. However, in the image display device 1 according to this embodiment, by mounting the connector 43 on the metal circuit board 4, the metal circuit board 4 can be made large. The connector 43 is placed, for example, in a non-placement area 46 of the metal circuit board 4.

[0032] The connector 43 is mounted on the metal circuit board 4 at a position higher in the vertical direction than the light emitting element 41. For example, the connector 43 is provided in the non-placement area 46 of the metal circuit board 4, and is mounted at a position higher than the light emitting element 41 provided in the placement area 45. Therefore, the heat H emitted from the light emitting element 41 is efficiently transferred to the connector 43 side.

[0033] Next, the operation of the image display device 1 according to this embodiment will be described.

[0034] 2, the operation of the image display device 1 is as follows: first, a control signal is input to the display unit 5 through the wiring member 6, and the display unit 5 generates an image in accordance with the control signal. Also, in Fig. 3, an activation signal is input to the light-emitting element 41, causing the light-emitting element 41 to emit light. The light emitted from the light-emitting element 41 is optically processed by the condenser lens 22, the light distribution lens 23, the sheet material 26, and the sheet material 27, and then enters the display unit 5.

[0035] At this time, as shown in Fig. 6, the light emission of the light-emitting elements 41 is adjusted individually for each column of the array. For example, the current value of the current passed through the light-emitting elements 41 is decreased from the ends of the array toward the center. For example, the current value passed through the light-emitting elements 41 in columns L12 and L14 is decreased compared to the light-emitting elements 41 in columns L11 and L15, and the current value passed through the light-emitting elements 41 in column L13 is decreased compared to the light-emitting elements 41 in columns L12 and L14. As a result, the light emission luminance of the light-emitting elements 41 in column L13 at the center is decreased. As shown in Figs. 7 and 8, the light emission luminance at the center of the display range of the display unit 5 is prevented from becoming too high, thereby suppressing brightness unevenness.

[0036] For example, it is assumed that the same current value I1 is applied to all light-emitting elements 41 as shown in FIG. 9. In this case, as shown in FIG. 10, the emission luminance of the display unit 5 corresponding to the light-emitting elements 41 in columns L11 and L15 at the ends of the array will be significantly lower than the emission luminance of the display unit 5 corresponding to the light-emitting elements 41 in column L13 at the center of the array. Therefore, the emission luminance of the display unit 5 corresponding to the light-emitting elements 41 in columns L11 and L15 at the ends of the array may be lower than the reference luminance B. The reference luminance B is a preset luminance value that serves as an index of the display luminance of the display unit 5. For example, the display unit 5 performs appropriate display when the display luminance is equal to or higher than the reference luminance B.

[0037] In response to this, for example, it is conceivable to increase the current value of the current passed through the light-emitting elements 41 from I1 to I2 as shown in FIG. 12, so that the emission luminance of the display unit 5 corresponding to the light-emitting elements 41 in columns L11 and L15 at the ends of the array exceeds the reference luminance B. However, in this case, as shown in FIGS. 13 and 14, the emission luminance of the display unit 5 corresponding to the light-emitting elements 41 in column L13 at the center of the array increases, making it difficult to suppress luminance unevenness in the display range of the display unit 5. In addition, the heat generated by the light-emitting elements 41 also increases, raising concerns that the light-emitting elements 41 may become overheated. Furthermore, since the current passed through the light-emitting elements 41 increases, the power consumption of the device increases.

[0038] Therefore, the image display device 1 according to this embodiment makes it possible to individually adjust the light emission of the light-emitting elements 41 in each column of the array, and the current value of the current passed through the light-emitting elements 41 can be made lower from the ends of the array to the center. As a result, the image display device 1 according to this embodiment can prevent the display brightness in the center of the display range of the display unit 5 from becoming too high, thereby suppressing brightness unevenness. Furthermore, the image display device 1 according to this embodiment can prevent the heat generated by the light-emitting elements 41 from increasing, and prevent the light-emitting elements 41 from becoming overheated, while suppressing brightness unevenness in the display unit 5. Furthermore, the image display device 1 according to this embodiment can prevent power consumption from increasing.

[0039] 1, display light L is output from the display unit 5. The display light L is reflected by the optical unit 3, emitted from the opening 12, and projected onto the display member 103. The driver of the vehicle 100 can recognize the display light L projected onto the display member 103 as a virtual image S.

[0040] As described above, the image display device 1 according to this embodiment is provided with a control unit 7 that can adjust the light emission brightness of the light emitting elements 41 individually for each column of the array, thereby reducing power consumption while suppressing brightness unevenness in the display unit 5.

[0041] Furthermore, the image display device 1 according to this embodiment can prevent the display brightness of the display unit 5 from increasing too much in the central portion by decreasing the current value of the light-emitting element 41 toward the center of the array, thereby appropriately suppressing brightness unevenness in the display unit 5.

[0042] Furthermore, the image display device 1 according to this embodiment uses a metal circuit board 4 in which plate-shaped metal members 42 are stacked as a circuit board, thereby improving heat dissipation properties and enabling the device to be made smaller by omitting the installation of heat dissipation fins, etc.

[0043] Although the image display device according to the present embodiment has been described, the image display device according to the present invention is not limited to the above-described embodiment, and various modifications are possible within the scope of the claims. The image display device according to the present embodiment may be configured by appropriately combining the components of the embodiments and modified examples described above.

[0044] For example, in the above-described embodiment, in columns L11, L12, L13, L14, and L15 in the unit width direction D2, the value of the current passed through the light-emitting elements 41 decreases from the ends of the array toward the center, but in columns L21, L22, and L23 in the unit height direction D3, the value of the current passed through the light-emitting elements 41 may decrease from the ends of the array toward the center. Even with such an image display device, it is possible to obtain the same effects as in the above-described embodiment, suppress power consumption, and suppress brightness unevenness in the display unit 5. [Explanation of symbols]

[0045] 1: Image display device 2: Display unit 3:Optical department 4: Metal circuit board (circuit board) 5: Display section 7: Control unit 41: Light-emitting element 103: Display member L:Display light

Claims

1. a display unit that emits display light; an optical unit that reflects the display light and projects it onto a display member; the display unit includes a circuit board on which light-emitting elements are mounted, a display section that receives light emitted by the light-emitting elements and emits the display light, and a control section that controls the light emission brightness of the light-emitting elements; a plurality of the light-emitting elements are arranged on the circuit board; the control unit is capable of adjusting the light emission brightness of the light emitting elements individually for each column of the array. Image display device.

2. the control unit adjusts the light emission brightness by decreasing a current value applied to the light emitting elements from the ends of the array toward the center. The image display device according to claim 1 .

3. The circuit board is a metal circuit board formed by laminating plate-shaped metal members.

3. The image display device according to claim 1 or 2.

Images