VEHICLE DISPLAY DEVICE

A vehicle display device includes one light source, a display device that emits display light by light incident from the light source, a first lens causing the light incident from the light source to be polarized toward the display device, and a second lens arranged between the first lens and the display device and distributing the light polarized through the first lens toward the display device. An emitting surface of the first lens is formed of one convex curved surface corresponding to the one light source. An emitting surface of the second lens is formed in a convex shape to be curved toward the display device side, and includes a plurality of curved microlens surfaces.

CROSS-REFERENCE TO RELATED APPLICATION(S)

The present application claims priority to and incorporates by reference the entire contents of Japanese Patent Application No. 2021-065140 filed in Japan on Apr. 7, 2021 and Japanese Patent Application No. 2022-008367 filed in Japan on Jan. 24, 2022.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a vehicle display device.

2. Description of the Related Art

Some vehicles are equipped with a vehicle display device that displays a virtual image of information provided to a driver in the vehicle interior. This vehicle display device is a so-called head-up display device including a plurality of light emitting elements mounted on a substrate and arranged at intervals, and a display device that emits a display image as display light, which is projected on a projected member such as a windshield or a combiner (for example, Japanese Patent Application Laid-open No. 2018-120807).

Regarding the vehicle display device in the related art, since the entire display area of the display device is irradiated with light from a light source, a polarizing lens is disposed according to the size of the display area. Although the polarizing lens is functionally formed to include an emitting surface of the polarizing lens, which is formed in a convex shape to be curved, the polarizing lens includes a plurality of convex portions (mountain portions) formed according to the light emitting elements, and also includes a concave portion (valley portion) formed between a plurality of mountain portions, that is, at a boundary between the mountain portions.

Regarding the vehicle display device in the related art, there is a case in which light emitted from the light source and incident onto the polarizing lens is reflected at the valley portion, so that loss of the light transmitting through the polarizing lens occurs. Therefore, the amount of light that transmits through the valley portion decreases as compared with the amount of light that transmits through the mountain portion of the polarizing lens, and the brightness is changed. Thus, there is room for improvement in terms of the visibility of a virtual image for the driver.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above problem, and an object of the present invention is to provide a vehicle display device capable of improving the visibility of a virtual image displayed on a front field of a driver.

In order to achieve the above mentioned object, a vehicle display device according to one aspect of the present invention includes one light source; a display device that emits, as display light, a display image projected on a projected member provided on a vehicle by light incident from the light source; a first lens arranged on an optical path between the light source and the display device, and causing the light incident from the light source to be polarized toward the display device; and a second lens arranged between the first lens and the display device on the optical path, and distributing the light polarized through the first lens toward the display device, wherein the first lens includes an emitting surface that emits light toward the display device, the emitting surface of the first lens is formed of one convex curved surface corresponding to the one light source, the second lens includes: an incident surface onto which the light polarized through the first lens is incident; and an emitting surface which is formed in a convex shape to be curved toward the display device side and through which the light incident on and transmitting through the incident surface is emitted, and the emitting surface of the second lens includes a plurality of curved microlens surfaces arranged.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, an embodiment of a vehicle display device according to the present invention will be described in detail with reference to the drawings. The present invention is not limited to the present embodiment. The components in the embodiment described below include components that can be easily assumed by those skilled in the art, or components that are substantially the same. Various omissions, replacements, or changes of the components in the embodiment described below can be made without departing from the gist of the invention.

Embodiment

As illustrated inFIG. 1, a vehicle display device1is, for example, a head-up display device mounted on a vehicle100such as an automobile. In the vehicle100, the vehicle display device1is arranged inside an instrument panel102, and projects a display image on a windshield103that is a projected member. The windshield103has semi-transmissive properties of reflecting part of incident light and transmitting the remaining part. Therefore, the windshield103reflects display light L emitted from the vehicle display device1toward an eye point EP of a driver D as a display image while transmitting a foreground of the vehicle100. The driver D recognizes the display image reflected by the windshield103as a virtual image S. The virtual image S is recognized forward of the windshield103with respect to the driver D. As illustrated inFIG. 2, the vehicle display device1of the present embodiment includes a housing2, two reflecting mirrors3, a backlight unit5, and a controller7.

The housing2is formed of, for example, a synthetic resin or the like, and fixed to a vehicle body (not illustrated). As illustrated inFIG. 2, the backlight unit5, the two reflecting mirrors3, and the controller7are housed in an internal space2bof the housing2and supported by the housing2. The housing2includes an opening2athrough which the outside of the housing2and the internal space2bcommunicate with each other. The opening2ais provided in the housing2at a position facing the windshield103, and is blocked with a transparent cover6. The transparent cover6transmits the display light L that is emitted from the backlight unit5and reflected by the two reflecting mirrors3. The display light L transmitted through the transparent cover6travels toward the windshield103.

As illustrated inFIG. 2, the two reflecting mirrors3are arranged on an optical path of the display light L from the backlight unit5to the windshield103, and reflect the display light L emitted from the backlight unit5toward the windshield103. The two reflecting mirrors3are composed of a plane mirror8and a concave mirror9.

The plane mirror8has a reflecting surface formed to be planar and is arranged at a position facing the backlight unit5. The plane mirror8totally reflects, on the reflecting surface, the display light L emitted from the backlight unit5toward the concave mirror9.

The concave mirror9has a reflecting surface formed to be a concave curved surface and is arranged at a position facing the plane mirror8. The concave mirror9totally reflects the display light L reflected by the plane mirror8toward the windshield103via the transparent cover6. The concave mirror9functions as, for example, a magnifying mirror. The concave mirror9reflects the display image to be enlarged so that the display image displayed by the display light L after being reflected by the concave mirror9is relatively enlarged as compared to the display image displayed by the display light L before being reflected by the concave mirror9.

The backlight unit5emits the display image projected on the windshield103as the display light L. The backlight unit5includes a cylindrical housing10, a display device11, a light source12, a light source substrate13, a first lens14, and a second lens15.

The cylindrical housing10is formed of, for example, synthetic resin or the like in a box shape, and supports each of the display device11and the second lens15along an optical axis direction. Both ends of the cylindrical housing10are open in the optical axis direction, one opening is blocked by the light source substrate13, and the other opening is blocked by the display device11.

The display device11emits the display image projected on the windshield103by the light incident from the light source12, as the display light L. The display device11is a so-called liquid crystal panel, and is formed of, for example, a light transmissive type or a light semi-transmissive type thin film transistor (TFT) liquid crystal display or the like. The display device11has a display area11aincluding a plurality of pixels. In the display area11a, the plurality of pixels are arranged in a matrix. The display device11displays a display image including numbers, characters, figures, and the like according to a control signal of the controller7, for example. The display area11ais an area where the display image is displayed. The display device11is arranged on the optical path of the light emitted from the light source12, and illuminated from the light source12side, so that a display surface opposite to the light source12in the optical axis direction emits light.

The light source12illuminates the display device11. The light source12is composed of, for example, one light emitting element mounted on the light source substrate13. The light emitting element is, for example, a light emitting diode (LED). In addition, the light source12includes that the light emitting elements are collectively mounted on the light source substrate13of the first lens14at a position where an optical axis of the first lens14passes through when viewed from the optical axis direction. In this case, as illustrated in, for example,FIGS. 3, 4A, and4B, one light source12is composed of three LEDs16that are collectively mounted on the light source substrate13at a position where the optical axis of the first lens14passes through. The three LEDs16are arranged in a row with respect to the light source substrate13in a direction orthogonal to a light source direction. For example, the light source12is turned on by a power source mounted on the vehicle100, for example, electric power obtained from a battery (not illustrated) or the like. The number of the LEDs16is not limited to three. The arrangement of the plurality of LEDs16is not limited to one row, and may be arranged in an annular shape or a polygonal shape as long as the arrangement can be recognized as one light source.

The light source substrate13is formed in a rectangular shape when viewed from the light source direction. A plurality of the LEDs16that function as the light source12and a plurality of electronic components are mounted on a so-called mounting surface of the light source substrate13. On the other hand, for example, a heat sink (not illustrated) is fixed to a surface opposite to the mounting surface of the light source substrate13. The heat generated from the light source12is stored in the light source substrate13. The heat sink releases the heat stored in the light source substrate13to the outside of the backlight unit5.

The first lens14is arranged on the optical path between the light source12and the display device11, and causes the light incident from the light source12to be polarized toward the display device11. As illustrated inFIG. 3, the first lens14is arranged between the light source12and the second lens15on the optical path between the light source12and the display device11. The first lens14is formed of a high refractive index material such as glass or a transparent resin, for example, and functions to refract light traveling toward the outside inward and cause the light to be polarized toward the second lens15. As illustrated inFIG. 4B, the first lens14is formed in an elliptical shape when viewed from the optical axis direction. As illustrated inFIGS. 3 and 4A, the first lens14includes an incident surface14aonto which the light emitted from the light source12is incident and an emitting surface14bfrom which the light incident onto the incident surface14ais emitted toward the display device11.

The incident surface14aof the first lens14faces the light source12and is a flat surface. The emitting surface14bis an opposite surface to the incident surface14aand faces the second lens15.

The emitting surface14bof the first lens14is formed of one convex curved surface corresponding to one light source12. When viewed from a direction orthogonal to the optical axis direction, one mountain portion is formed on the emitting surface14binstead of forming one or more of valley portions that are formed on the emitting surface of the first lens40in the related art. As illustrated inFIGS. 4A and 4B, the emitting surface of the first lens40in the related art includes the plurality of mountain portions corresponding to the LEDs60that are a plurality of light sources, but the emitting surface14bof the first lens14includes one mountain portion corresponding to one light source12.

The second lens15is arranged between the first lens14and the display device11on the optical path between the light source12and the display device11, and distributes the light polarized through the first lens14toward the display device11. The second lens15is formed of a material such as glass or a transparent resin, for example, and refracts and condenses the light toward the display area11aof the display device11. The second lens15is fixed to the cylindrical housing10by screws or the like. As illustrated inFIG. 4B, the second lens15is formed in a rectangular shape when viewed from the optical axis direction. The second lens15includes an incident surface15aonto which the light that has been polarized through the first lens14is incident, and an emitting surface15bwhich is formed in a convex shape to be curved toward the display device11side and through which the light incident on and transmitting through the incident surface15ais emitted.

The incident surface15aof the second lens15faces the first lens14, and is a curved surface formed in a convex shape on the first lens14side.

The emitting surface15bof the second lens15has a plurality of curved microlens surfaces20as illustrated inFIGS. 5A and 5B. Each of the curved microlens surfaces20is a so-called curved microlens surface, for example, a fly-eye-shaped lens surface. A plurality of the plurality of curved microlens surfaces20are arranged, for example, in a grid pattern along the emitting surface15bin a convex shape to be curved. As illustrated inFIGS. 5A and 5B, the curved microlens surfaces20are arranged on the emitting surface15bin an X direction and in a Y direction orthogonal to the X direction. Each of the curved microlens surfaces20has, for example, a rectangular shape in front view. Each of the curved microlens surfaces20has a long side of a length x in the X direction and a short side of a length y (not the same as x) different from the length x in the Y direction. The curved microlens surfaces20have, for example, the same length x in the X direction and the same length y (not the same as x) in the Y direction.

As illustrated inFIG. 2, the controller7is connected to the backlight unit5and controls the backlight unit5. The controller7is composed of, for example, an IC chip or the like mounted on the substrate and is driven by electric power obtained from the battery mounted on the vehicle100.

Next, a virtual image displaying operation in the vehicle display device1will be described with reference toFIGS. 2 and 3. First, the light emitted from the light source12is incident onto the incident surface14aof the first lens14, transmits through the inside of the first lens14, and is emitted from the emitting surface14b. The light emitted from the emitting surface14bis refracted by the first lens14and polarized toward the incident surface15aof the second lens15. The light incident onto the incident surface15aof the second lens15transmits through the inside of the second lens15and is emitted from the emitting surface15b. The light emitted from the emitting surface15bis refracted by the second lens15, diffused by the curved microlens surfaces20that are formed on the emitting surface15b, and emitted toward the display area11aof the display device11. The display device11emits the display image displayed on the display area11aas the display light L by the light transmitted through the inside of the display device11.

The display light L emitted from the display device11of the backlight unit5travels toward the plane mirror8. The plane mirror8reflects, toward the concave mirror9, the display light L incident from the backlight unit5. The concave mirror9reflects, toward the windshield103, the display light L incident from the plane mirror8by the reflecting surface in a concave shape via the transparent cover6. Therefore, the display image corresponding to the display light L is projected on the windshield103, and the virtual image S is displayed forward of the eye point EP of the driver D.

In the vehicle display device1of the present embodiment, the emitting surface14bof the first lens14is formed of one convex curved surface corresponding to one light source12. Therefore, it is possible to arrange the light source12on the optical axis or the optical axis side of the first lens14while ensuring the irradiation of the light over the entire display area11aof the display device11. As a result, for example, in a case in which one light emitting element is used as one light source, the size of the light source substrate13can be reduced to about 50% of the size of the substrate in the related art. Furthermore, the sizes of the backlight unit5and the vehicle display device1can be reduced. In the related art, since the light sources are uniformly arranged on the light source substrate for one first lens to make the brightness uniform while expanding the display area, the light source is arranged outside the range referred to as one light source. Thus, the mountain portions are required to be provided on the emitting surface of the first lens. However, the present embodiment is not limited to one light emitting element for one light source, and for example, in a case in which the light emitting elements are used, since the light emitting elements are collectively mounted in the range referred to as one light source, the mountain portions are not required to be provided on the first lens similar to the case in which one light emitting element is used. In addition, since the valley portions are not provided, a change in the brightness of the virtual image S can be reduced and the visibility can be improved.

In the vehicle display device1, the second lens15includes the curved microlens surfaces20on the emitting surface15b. In the related art, in order to cause the display area11aof the display device11to be irradiated with the light of the light source12, the diffusion lens is arranged on the optical path to diffuse the light, but light loss may occur since the light is transmitted through the diffusion lens. Therefore, the curved microlens surfaces20are formed on the emitting surface15bof the second lens15, so that the diffusion lens is not required, and a decrease in brightness caused by transmitting the light through the diffusion lens can be suppressed. As a result, the visibility can be improved by at least 10% or more. Since the diffusion lens in the related art is an additional component, the assembly of the additional component can be cut down, and an assembling property of the device can be improved.

As illustrated inFIG. 6A, the vehicle display device1is formed such that the emitting surface15bof the second lens15is formed in a convex shape to be curved toward the display device11side and the incident surface15aof the second lens15is formed in a convex shape to be curved toward the light source12side. On the other hand, in the diffusion lens50in the related art, illustrated inFIG. 6B, both the incident surface and the emitting surface are formed to be curved in a concave shape. Therefore, areas of both end surfaces15cin the direction orthogonal to the optical axis direction of the second lens15can be reduced as compared with both end surfaces50aof the diffusion lens50in the related art. As a result, reflected light La reflected at both end surfaces15cof the second lens15can be reduced, the reflected light La traveling toward the windshield103through a normal optical path formed between the two light-blocking walls30can be suppressed, and the visibility of the virtual image S can be improved. By forming an inclination15dof each of the end surfaces15cof the second lens15so as to incline from the outside toward the inside, the reflected light La reflected by the end surfaces15cis applied to the light-blocking walls30to block the light, and the light passing through other than the normal optical path is reduced to improve the visibility of the virtual image S.

Since a backlight unit202in the related art, illustrated inFIG. 7A, emits the reflected light La other than the display light L, part of the reflected light La is reflected by the transparent cover6to become stray light in a case in which a distance between the backlight unit202and the concave mirror9is shortened. The stray light is mixed with the display light L via the concave mirror9, so that the visibility of the virtual image S may deteriorate. By adopting the above configuration, the distance between the backlight unit202and the concave mirror9can be shortened by the reflected light La being reduced (FIG. 7B). As a result, the housing2can be made smaller than a housing201of a vehicle display device200in the related art.

In the above embodiment, it has been described that the curved microlens surface20is a fly-eye-shaped lens surface. In general, the fly-eye-shaped lens includes a spherical lens and a cylindrical lens, but the curved microlens surface20is not limited to a spherical surface, and may be an aspherical surface, for example.FIG. 8is a partial side view illustrating the aspherical surface applied to each of the curved microlens surfaces according to a modified example of the embodiment, andFIG. 9is a diagram illustrating illuminance distribution by the aspherical microlenses. A curved microlens surface20A according to a modified example of the embodiment is the aspherical surface that diffuses light substantially uniformly so as to suppress brightness unevenness (FIGS. 8 and 9). The shape of the aspherical surface is designed according to the geometrical arrangement and the shape of the optical system in the device. As long as the shape satisfies the above description, the shape of each of the curved microlens surfaces20A viewed from the direction orthogonal to the optical axis direction may be either a symmetrical shape or an asymmetrical shape. In addition, as long as the shape satisfies the above description, a lens height in a case in which each of the curved microlens surfaces20is the aspherical surface may be higher or may be lower than a lens height in a case in which each of the curved microlens surfaces20is the spherical surface. Furthermore, as long as it is possible to uniformly diffuse the light so that the brightness unevenness is suppressed over the entire second lens15, all of the curved microlens surfaces20A may be aspherical surfaces having the same shape or may be aspherical surfaces having a different shape from each other. Since the curved microlens surfaces20A are thus the aspherical surfaces, the light emitted from the emitting surface15bof the second lens15toward the display device11can be efficiently diffused, and local condensation of the light is suppressed, the brightness unevenness of the display image can be suppressed. As a result, in the vehicle display device1according to the modified example of the present embodiment, the visibility of the virtual image S displayed on a front field of the driver D can be improved.

In the above embodiment, the backlight unit5adopts a liquid crystal display system, but may adopt another system, for example, a laser system, a digital light processing (DLP) system, or a projector system.

In the above embodiment, the controller7may be connected to an electronic control unit (ECU) (not illustrated) mounted on the vehicle100, and may transmit and receive a signal to and from the ECU.

In addition, in the above embodiment, the vehicle display device1includes two reflecting mirrors3, but the present embodiment is not limited thereto. For example, as in a vehicle display device1A illustrated inFIG. 7B, one reflecting mirror3(concave mirror9) may be included. Alternatively, three or more reflecting mirrors3may be included. The plane mirror8may be a concave mirror, or may be, for example, a convex mirror, an aspherical mirror, a spherical mirror, a free curved mirror, and the like. The concave mirror9may be, for example, a convex mirror, an aspherical mirror, a spherical mirror, a free curved mirror, and the like. In addition, the concave mirror9has a function as the magnifying mirror, but the present embodiment is not limited thereto, and may have a function as a correcting mirror.

In the above embodiment, each of the vehicle display devices1and1A projects the display image on the windshield103of the vehicle100, but the present embodiment is not limited thereto, and each of the vehicle display devices1and1A may project the display image on, for example, a combiner or the like.

In the above embodiment, each of the vehicle display devices1and1A is applied to the vehicle100such as an automobile, but the present embodiment is not limited thereto, and may be applied to, for example, a ship or an aircraft other than the vehicle100.

The vehicle display device according to the present embodiment exerts an effect of enabling improvement in the visibility of a virtual image displayed on a front field of the driver.