WO2014119407A1

WO2014119407A1 - Head-up display device

Info

Publication number: WO2014119407A1
Application number: PCT/JP2014/050931
Authority: WO
Inventors: 俊関谷
Original assignee: 日本精機株式会社
Priority date: 2013-01-31
Filing date: 2014-01-20
Publication date: 2014-08-07
Also published as: JP2014149405A

Abstract

An objective of the present invention is to alleviate a decline in visibility from an entry of outside light, and to project a display image with desirable visibility. A head-up display device comprises: a DMD which emits a display light (L') which configures a display image; and a transmissible screen (18) which has a photoreceptor face which receives the display light (L') and an emission face which emits the received display light (L') as diffused light, and which has a diffusion characteristic which makes the distribution of the light intensity of diffused light (L) approximately uniform. The transmissible screen (18) is positioned with the normal of the transmissible screen (18) inclined at a given angle (α) to an optical axis (AX) of the display light (L'), and outside light which reaches the emission face along the optical axis (AX) of the display light (L') is reflected in a different direction from the direction along the optical axis (AX) of the display light (L').

Description

Head-up display device

The present invention relates to a head-up display device.

Head-up display (HUD) that displays information in front of the windshield so that the vehicle driver can read vehicle information (speed, mileage, etc.) with little movement while driving An apparatus has been proposed (for example, Patent Document 1 below). This HUD device is provided in a dashboard of a vehicle or the like, and projects a display image on a windshield, thereby allowing the driver to visually recognize the display image as a virtual image.

As the above-described vehicle HUD device, a HUD device using a two-dimensional spatial modulation device such as DMD (Digital Micromirror Device) has been proposed. For example, Patent Document 2 below discloses a HUD apparatus including a display device such as liquid crystal or DMD, a projection optical system, and a screen. In the HUD device described in Patent Document 2, an image generated on a display device is imaged on a screen using a projection lens system.

Also, a HUD device having a semiconductor laser as a light source for projecting a display image has been proposed. For example, Patent Document 3 below discloses a HUD device including a semiconductor laser, a scanning system, and a screen. In the HUD device described in Patent Document 3, a display image is generated by scanning a laser beam emitted from a semiconductor laser toward a screen by a scanning system.

Japanese Patent Laid-Open No. 5-193400 JP 2004-126226 A Japanese Patent Laid-Open No. 7-270711

In the HUD device described above, external light such as sunlight may enter from the outside of the windshield. In this case, the incident external light is reflected by the screen, and the reflected external light may be superimposed on the display light to cause a washout that reduces the visibility of the display image.

The present invention has been made in view of the above circumstances, and provides a head-up display device capable of suppressing a decrease in visibility due to incidence of external light and projecting a display image with good visibility. Objective.

In order to achieve the above object, a head-up display device according to the present invention includes:
Display light emitting means for emitting display light constituting a display image;
A transmission screen having a light receiving surface for receiving the display light and an output surface for emitting the received display light as diffused light, and having a diffusion characteristic that makes the light intensity distribution of the diffused light substantially uniform;
With
The transmissive screen is arranged by tilting the normal line of the transmissive screen at a certain angle with respect to the optical axis of the display light, and external light reaching the emission surface along the optical axis of the display light. Reflecting in a direction different from the direction along the optical axis of the display light,
It is characterized by that.

According to the present invention, it is possible to suppress a decrease in visibility due to the incidence of external light and project a display image with good visibility.

It is a conceptual diagram which shows how the display apparatus which concerns on one Embodiment of this invention is mounted in the vehicle, and how a virtual image is formed. It is a schematic block diagram of the HUD apparatus which concerns on one Embodiment of this invention. It is a schematic block diagram of the display apparatus with which the HUD apparatus of FIG. 2 is provided. (A) is a side view which shows the transmission characteristic of a general transmissive screen, (b) is a side view which shows the reflective characteristic of this transmissive screen. (A) is a figure which shows the light intensity distribution of a transmissive screen when a diffusion angle is large, (b) is a figure which shows the light intensity distribution of a transmissive screen when a diffusion angle is small. It is a side view which shows the transmission / reflection characteristic at the time of the inclination arrangement | positioning of a transmissive screen. It is a side view of the 1st micro lens array concerning one embodiment of the present invention. (A) is an enlarged plan view of a first microlens array according to an embodiment of the present invention, and (b) is an enlarged plan view of a second microlens array according to an embodiment of the present invention. is there. It is a figure which shows the light intensity distribution of the transmissive screen which concerns on this embodiment. It is a figure which shows the relationship between the inclination angle of a transmissive screen, and the intensity | strength of incident external light. It is a side view of the micro lens array which concerns on the modification of this invention. (A) is a side view of the microlens array which concerns on the modification of this invention, (b) is an enlarged plan view of the microlens array. It is a figure which shows the relationship between the inclination angle of a transmissive screen, and the intensity | strength of incident external light. It is a side view of the micro lens array which concerns on the other modification of this invention. It is a side view of the micro lens array which concerns on the other modification of this invention. It is a side view of the micro lens array which concerns on the other modification of this invention.

The configuration, operation, and effect of the HUD device according to an embodiment of the present invention will be specifically described below.

As shown in FIG. 1, the HUD device 1 according to the present embodiment is provided in a dashboard of the vehicle 2 and emits display light L (see FIG. 2) representing a generated display image to the windshield 3 (an example of a transparent plate). ) To cause the driver to visually recognize the virtual image V of the display image representing the vehicle information. The driver visually recognizes the display image as the virtual image V in Eyebox 4 which is a range (viewing area) where the display image can be visually recognized as the virtual image V. Eyebox 4 is an area defined as a range in which the virtual image V can be properly visually recognized. Note that the virtual image V in FIG. 1 is schematically shown in order to facilitate sensory understanding. The same applies to the display light L in FIG.

As shown in FIG. 2, the HUD device 1 shown in FIG. 1 includes a display device 10, a reflector 20, a housing 30, and a control unit (not shown).

The display device 10 is a device that emits display light L by combining laser beams of three primary colors of R, G, and B, and displays a display image by a field sequential color (Field 方式 Sequential Color) method. As shown in FIG. 3, the display device 10 includes a laser diode (Laser Diode; LD) 11 serving as a light source unit (illuminating means), a mirror unit 12, a reflection mirror 13, a prism (optical element) 14, A reflective display element (DMD: Digital Mirror Device) 15, an optical sensor (detection element) 16, a projection lens 17, and a transmissive screen 18 are provided. The DMD 15 corresponds to a specific example of “display light emitting means” of the present invention.

LD 11 includes a surface light source LD 11 r that emits red laser light R, a surface light source LD 11 g that emits green laser light G, and a surface light source LD 11 b that emits blue laser light B. In the LD 11, the LD 11r, LD 11g, and LD 11b are individually turned on, and sequentially emit blue, red, and green laser beams.

The mirror unit 12 includes a dichroic mirror 12a, a dichroic mirror 12b, and a dichroic mirror 12c. The dichroic mirror 12a, the dichroic mirror 12b, and the dichroic mirror 12c are arranged in parallel to each other.

The dichroic mirror 12a is positioned on the traveling direction side of the blue laser light B emitted from the LD 11b, and is disposed at a predetermined angle with respect to the traveling direction of the blue laser light B. As a result, the dichroic mirror 12a receives the blue laser light B emitted from the LD 11b, and emits a part thereof as reflected light L1 toward the dichroic mirror 12b.

The dichroic mirror 12b is located on the traveling direction side of the laser light emitted from the dichroic mirror 12a and the LD 11r, and is disposed at a predetermined angle with respect to the traveling direction of each laser light. Thereby, the laser beam L1 is transmitted, the red laser beam R emitted from the LD 11r is received, and a part thereof is reflected toward the dichroic mirror 12c. In this way, the dichroic mirror 12b combines the laser light L1 and the red laser light R, and emits the combined laser light L2 toward the dichroic mirror 12c.

The dichroic mirror 12c is located on the traveling direction side of the laser light emitted from the dichroic mirror 12b and the LD 11g, and is disposed at a predetermined angle with respect to the traveling direction of each laser light. Accordingly, the laser beam L2 is transmitted, the green laser beam G emitted from the LD 11g is received, and a part thereof is reflected toward the reflection mirror 13. In this way, the dichroic mirror 12c combines the laser beam L2 and the green laser beam G, and emits the combined laser beam L3 toward the reflection mirror 13.

As described above, the LD 11 and the mirror unit 12 emit laser light for color display of a display image to be described later by combining and emitting the laser beams R, G, and B. In the present embodiment, the LD is used as the light source unit of the display device 10, but the present invention is not limited to this. For example, you may use LED as a light source part.

The reflection mirror 13 is composed of a plane mirror, and reflects the laser beam L3 emitted from the mirror unit 12 toward the prism 14.

The prism 14 is an optical system having a triangular prism shape, and is disposed between the reflection mirror 13, the DMD 15, and the optical sensor 16. When the prism 14 receives the laser light L3 emitted from the reflection mirror 13 by the inclined surface 14a, the prism 14 transmits part of the laser light L3 to the DMD 15 and reflects the other part to the optical sensor 16. The prism 14 reflects the display light L ′ emitted from the DMD 15 and emits it toward the projection lens 17. In the present embodiment, the antireflection film is not provided on the inclined surface 14a of the prism 14, but the present invention is not limited to this.

The DMD 15 is a display element in which a plurality of minute mirror surfaces that can be individually controlled are arranged in a plane. The DMD 15 receives the laser light L3 with a plurality of mirror surfaces, and reflects the laser light L3 received with a mirror surface in a reflective state among them. Each minute mirror surface corresponds to one pixel of the display image. When the laser beam L3 representing one pixel is incident on the DMD 15, the laser beam L3 is reflected only on the mirror surface corresponding to the pixel. By continuously performing this process for all the pixels in the display image, display light L ′ constituting the display image is generated. The state of each mirror surface is controlled by the control unit.
Further, the DMD 15 emits the generated display light L ′ toward the prism 14. In the present embodiment, DMD is used as the reflective display element of the display device 10, but the present invention is not limited to this. For example, LCOS may be used as the reflective display element.

The optical sensor 16 is a light receiving element composed of, for example, a photodiode or a phototransistor. The optical sensor 16 detects the light intensity of the laser light L3 reflected by the inclined surface 14a of the prism 14, and supplies the detected light intensity data to the control unit. The light intensity is, for example, the brightness of laser light L3 or display light L described later.

The control unit is composed of, for example, a microcomputer and controls the display device 10. For example, the control unit controls the timing at which the LD 11 emits the laser beams R, G, and B and adjusts the light amount thereof, and controls the state of each mirror surface of the DMD 15 to generate a desired display image.

The projection lens 17 projects the display light L ′ generated by the DMD 15 onto the transmission screen 18. The projection lens 17 is formed so as to optimize the incident angle of the display light L ′ to the transmissive screen 18 in accordance with the characteristics of the optical system (the reflector 20 and the windshield 3) after the transmissive screen 18. Has been placed. The projection lens 17 may be composed of a single lens or a combination of a plurality of lenses.

The transmission screen 18 is projected with the display light L ′ (display image represented by the display light L ′) generated by the DMD 15. At this time, the transmissive screen 18 diffuses the display light L ′ and emits the diffused light (display light L) toward the reflector 20. Specific features, functions, and arrangement methods of the transmissive screen 18 will be described later. For ease of explanation, the display light L ′ is assumed to be light for one pixel incident on the center of the transmissive screen 18, and the optical axis AX is the optical axis of light for this one pixel. Further, the diffused light (display light L) is light obtained by diffusing the light for one pixel incident on the center of the transmissive screen 18.

In the display device 10 configured as described above, the DMD 15 generates the display light L ′ based on the laser beams R, G, and B emitted from the LD 11, and the transmissive screen 18 receives the display light L ′ and displays the display image. (Display image is projected) and display light L (diffused light) is emitted toward the reflector 20. The display device 10 may be a combination of a laser light source and a MEMS (Micro Electro Mechanical System) scanner.

Returning to FIG. 2, in the reflector 20, the display light L emitted from the display device 10 (transmission type screen 18) is connected to a desired position as a virtual image V (see FIG. 1) at a desired size. As described above, the optical system is provided between the optical path of the display device 10 (transmission screen 18) and the windshield 3. The reflector 20 includes a magnifying mirror 21, a holding member 22, and a stepping motor 23.

The magnifying mirror 21 is a concave mirror or the like, and reflects the display light L emitted from the display device 10 by the concave reflecting surface 21a to emit reflected light (display light L) toward the windshield 3. As a result, the size of the virtual image V to be connected becomes a size obtained by enlarging the display image (display light L). The magnification of the display image by the magnifying mirror 21 is determined by the focal length (curvature radius) of the magnifying mirror 21 and the distance between the transmission screen 18 and the magnifying mirror 21. Although the optical path space can be reduced when the focal length of the magnifying mirror 21 is short, the magnifying power by the magnifying mirror 21 depends on the size of the display image, the size of the image to be formed as the virtual image V, the image distortion of the virtual image V, and HUD. The optimum value is determined in consideration of the allowable volume (optical path space) of the apparatus 1 and the like. *

The magnifying mirror 21 is made of, for example, a resin member such as polycarbonate, and has a reflecting surface 21a on the surface of which a metal such as aluminum is deposited. The magnifying mirror 21 is bonded to the holding member 22 with an adhesive member such as a double-sided adhesive tape. The holding member 22 is made of, for example, a resin member such as ABS, and includes a gear portion 24 and a shaft portion 25. The shaft portion 25 of the holding member 22 is pivotally supported by the housing 30.

A gear 26 is attached to the rotation shaft of the stepping motor 23, and the gear 26 is meshed with the gear portion 24 of the holding member 22. The magnifying mirror 21 is supported in a rotatable state together with the holding member 22, and the magnifying mirror 21 can be rotated by the stepping motor 23 to adjust the projection direction of the display light L. An observer (viewpoint in FIG. 1) operates the pushbutton switch (not shown) to change the angle of the magnifying mirror 21 so that the display light L is reflected to the position of the eye (that is, the virtual image V can be visually recognized). adjust.

The housing 30 has an opening of a predetermined size on the upper side, is formed in a box shape from a hard resin or the like, and the display device 10 and the reflector 20 disposed at predetermined positions inside the housing 30. Storing. A window 31 is attached to the opening of the housing 30. A light shielding wall 32 is disposed on the inner wall of the housing 30.

The window portion 31 is formed in a curved shape from a translucent resin such as acrylic in accordance with the shape of the opening portion of the housing 30, and is attached to the opening portion of the housing 30 by welding or the like. The window 31 transmits the display light L reflected by the magnifying mirror 21.

The light shielding wall 32 is a flat plate-shaped shielding member, and is disposed so as to hang obliquely from the upper part of the housing 30. The light shielding wall 32 prevents a phenomenon (washout) in which external light such as sunlight enters the display device 10 and the virtual image V becomes difficult to see.

As described above, in the HUD device 1, the display image generated by the display device 10 is reflected and enlarged by the reflector 20, and then projected onto the windshield 3 so that the driver of the vehicle can visually recognize the virtual image V. . In other words, the driver views the image projected on the transmission screen 18 through the windshield 3 and the reflector 20 as a virtual image V. Further, in the HUD device 1, since the transmission screen 18 has a characteristic configuration, a reduction in visibility due to external light such as sunlight incident from the outside of the windshield 3 is suppressed. Hereinafter, a specific configuration and the like of the transmission screen 18 will be described in detail.

(Transmission type screen 18)
The transmissive screen 18 of the present embodiment has a configuration that reduces the influence of incident external light incident from the outside of the windshield 3 and sufficiently secures the light intensity of the display light L. That is, the transmissive screen 18 is characterized by its mounting method and the configuration of the light receiving surface and the light emitting surface. First, after explaining the attachment method of the transmission type screen 18, the structure of a light-receiving surface and an output surface is demonstrated.

First, a general transmissive screen mounting method in the HUD device will be described with reference to FIG. FIG. 4A is a schematic diagram showing a state in which display light corresponding to one representative pixel emitted from the transmissive screen is diffused by the transmissive screen and irradiated with the Eyebox. Although illustration is omitted, display light corresponding to each pixel forms an image on a transmission screen and diffuses so as to irradiate the entire Eyebox. Although omitted in the drawing, the display light is reflected and enlarged by the magnifying mirror and guided to the windshield.

As shown in FIG. 4A, the conventional transmissive screen is arranged such that its light receiving surface is perpendicular to the optical axis of the display light. Since the display light transmitted through the transmission screen is diffused at a predetermined diffusion angle θ, it is enlarged. The enlarged display light reaches the Eyebox, which is a range in which the driver can visually recognize the display image as a virtual image via the enlargement mirror and the windshield.

The diffusion angle is an angle formed by the display light diffused by the transmissive screen, and indicates a rate at which the display light is expanded when the display light is transmitted through the transmissive screen. This diffusion angle is determined by the configuration of the transmissive screen and the characteristics of the incident display light. The configuration of the transmissive screen is, for example, a lens pitch of a microlens array, a radius of curvature of the microlens, and the like described later.

The intensity distribution of display light (diffused light) diffused by a conventional transmission screen is a Gaussian distribution shown in FIG. That is, the light intensity becomes maximum near the center of the irradiation range, and the light intensity decreases at the end of the irradiation range. Further, the intensity distribution of the display light (diffused light) changes depending on the diffusion angle. For example, when display light with different diffusion angles (θ1> θ2) is irradiated, the display light with the diffusion angle θ1 has a wider irradiation range, and the maximum value of the light intensity becomes smaller (see FIG. 5A). On the other hand, the irradiation range of the display light having the diffusion angle θ2 is narrowed and the maximum value of the light intensity is increased (see FIG. 5B). The amount of light in the entire irradiation range is the same for the diffusion angle θ1 and for the diffusion angle θ2.

Therefore, when illuminating the whole area of the Eyebox with diffused light, that is, when increasing the display uniformity (uniformity of light intensity in the irradiation range), it is necessary to increase the diffusion angle as shown in FIG. There is. However, as the diffusion angle is increased, the base of the Gaussian distribution is widened, and the amount of light that protrudes outside the Eyebox range (indicated by the shaded area in the figure) increases, resulting in a large loss of light and a decrease in the brightness of the display image. To do. On the other hand, as shown in FIG. 5B, when the diffusion angle is decreased, the amount of light that protrudes out of the range of the Eyebox (the hatched portion in the figure) decreases and the light utilization efficiency (luminance) increases, but the Eyebox Since the amount of light decreases at the end of the display, the display uniformity decreases. That is, the diffusion angle needs to be an angle that achieves both light utilization efficiency and display uniformity. Optical characteristics such as light utilization efficiency and display uniformity that change according to the diffusion angle are called diffusion characteristics.

Therefore, in this embodiment, the light intensity that cannot sufficiently irradiate Eyebox is 50% or less of the peak intensity of the display light, and the half angle of the diffusion angle at that time is θ. Also, let φ be the half angle of the diffusion angle when the display light diffuses on the transmission screen and reaches the outermost part of the Eyebox. As described above, θ> φ is established between the diffusion angle θ and the diffusion angle φ.

On the other hand, as shown in FIG. 4B, in the above HUD device, when external light such as sunlight enters from the outside of the windshield, the incident external light irradiates the transmission screen through the windshield and the magnifying mirror. To do. The transmission screen has a transmittance of about 90%, and several% of the incident light is diffusely reflected by the transmission screen. This reflected external light reaches the viewing area of the driver of the vehicle through the magnifying mirror and the windshield in the same manner as the display light transmitted through the transmissive screen. For this reason, when the amount of incident extraneous light increases, the extraneous reflected light reflected by the transmissive screen cannot be ignored. This is because washout occurs in which reflected external light is superimposed on display light to reduce the visibility of the display image.

The reflected external light has a diffusion characteristic like the display light described above. That is, by increasing the diffusion angle, the display uniformity increases, but the light utilization efficiency decreases. In addition, by reducing the diffusion angle, the light utilization efficiency is increased while the display uniformity is decreased. In the present embodiment, the light intensity at which Eyebox cannot be sufficiently irradiated, that is, the light intensity that does not deteriorate the visibility is set to 50% or less of the peak intensity of the reflected light, and the half angle of the diffusion angle at that time Is θ ′.

Next, a method for attaching the transmission screen 18 in the HUD device 1 according to the present embodiment will be described with reference to FIG. FIG. 6 is a schematic diagram showing a state in which display light corresponding to one representative pixel emitted from the transmissive screen 18 is diffused by the transmissive screen 18 and irradiated with the Eyebox 4.
Although not shown, display light corresponding to each pixel forms an image on the transmissive screen 18 and diffuses so as to irradiate the entire Eyebox 4.
Further, the display light is emitted with an inclination corresponding to the inclination angle of the transmissive screen 18, but the emission angle is extremely small, so that the display light L after diffusion is before diffusion as shown in FIG. 6. The light is emitted along an optical axis substantially equal to the display light L ′. That is, it is considered that the optical axis of the display light is not changed by being diffused by the transmissive screen 18.
Although not shown in the figure, the display light is refracted and enlarged by the magnifying mirror and guided to the windshield.

As shown in FIG. 6, in the HUD device 1, the transmission screen 18 is arranged such that the normal line of the transmission screen 18 is tilted with respect to the optical axis AX of the display light L ′. That is, the light receiving surface of the transmissive screen 18 has an inclination angle α with respect to the direction orthogonal to the optical axis AX. As a result, the angle formed between the incident external light and the reflected external light is 2α. In this HUD device 1, the display light L emitted from the display device 10 is received by the light receiving surface of the transmissive screen 18, and then diffused from the light emitting surface to irradiate the Eyebox 4 (at this time, the display image is For example, the display light L ′ reaching the transmissive screen 18 may be generated in consideration of the extended portion so that the extended length is canceled. As described above, the transmissive screen 18 is disposed so as to be inclined with respect to the optical axis AX, but the display light L (diffused light) transmitted through the transmissive screen 18 is emitted along the optical axis AX. In the conventional transmission screen, as shown in FIG. 5, the light intensity in the irradiation range is greatly different between the center and the end, so that the light of the light actually irradiated on the Eyebox 4 when the transmission screen is tilted. The strength is significantly reduced. However, since the light receiving surface and the exit surface of the transmissive screen 18 are configured as described later, the display light irradiates the entire area of the irradiation box substantially uniformly, so that the area of the Eyebox 4 is efficiently irradiated. That is, a decrease in light intensity due to tilting can be reduced.

On the other hand, incident external light incident from the outside of the windshield 3 irradiates the transmission screen 18 through the magnifying mirror 21. A part of the incident light is reflected by the transmission screen 18. The reflected external light is emitted through the magnifying mirror 21 and the windshield 3 in the direction of the angle 2α with respect to the optical axis AX. At this time, since the transmissive screen 18 is configured as described later, the reflected external light diffuses at the diffusion angle θ ′. Therefore, by setting the inclination angle α of the transmissive screen 18 to the value calculated by the following formula (1), the irradiation range of the non-reflected light can be outside the range of Eyebox 4.

That is, by tilting the light receiving surface of the transmissive screen 18 at an inclination angle equal to or greater than α, washout that occurs when the reflected light is superimposed on the display light is suppressed, and the visibility of the display image (display light L) is improved. Can be secured.

Further, as a transmission type screen for the HUD device, a frost type diffusion plate such as ground glass or an opal type diffusion plate in which minute particles are dispersed is generally used. When such a transmission screen is used, normally, the diffuse intensity distribution of the transmitted light is Gaussian, the light intensity that illuminates the center of the Eyebox area is high, and the light intensity is at the end of the Eyebox area. Lower. Therefore, the conventional HUD device has a problem that the visibility of the display image is lowered due to the diffusion intensity of the transmitted light having a Gaussian distribution. Therefore, in the transmissive screen 18 of the present embodiment, such a problem is solved by configuring the light receiving surface and the irradiation surface as follows.

Next, the configuration of the transmission screen 18 will be described with reference to FIG. The transmission screen 18 has the following configuration to maintain the diffusion characteristics when the transmission screen 18 is tilted.

As shown in FIG. 7, the transmissive screen 18 is made of a translucent member, and a microlens array (MLA) 40 is formed on an incident surface on which display light is incident, and an emission surface from which the transmitted display light is emitted. A microlens array (MLA) 41 is formed in

As shown in FIG. 8A, in the in-plane direction of the MLA 40, for example, each of a plurality of microlenses (ML) 40a having a lens size of about 100 μm has a period at a pitch of dH in the horizontal direction and dV in the vertical direction. It is formed so that it may be arranged in order. In this embodiment, dH = dV, and the MLA 40 is formed such that square microlenses are periodically arranged in a lattice shape, and gaps and steps generated between adjacent MLs 40a are minimized. Here, the pitch is a distance between the lens centers of the ML 40a adjacent to each other, and this pitch is hereinafter referred to as “MLA 40 pitch”.

The MLA 41 has the same configuration as the MLA 40 as shown in FIG. That is, in the in-plane direction, for example, each of a plurality of micro lenses (ML) 41a having a lens size of about 100 μm is periodically arranged at a pitch of dH ′ in the horizontal direction and dV ′ in the vertical direction. Is. In this embodiment, dH ′ = dV ′, and the MLA 41 is formed such that square microlenses are periodically arranged in a lattice shape so that gaps and steps generated between adjacent MLs 41 a are minimized. Here, the pitch is the distance between the lens centers of the ML 41a adjacent to each other, and this pitch is hereinafter referred to as the “MLA 41 pitch”. The pitch of the MLA 41 is equal to the pitch of the MLA 40, and dH ′ = dH. In the present embodiment, the pitch of the MLA 40 and the pitch of the MLA 41 are arranged to be equal to each other. However, the present invention is not limited to this, and the MLA 40 and 41 are in accordance with the incident angle of the image projected on the transmissive screen 18. Can be determined.

Further, the ratio between the horizontal pitches dH and dH ′ and the vertical pitches dV and dV ′ determines the shape and aspect ratio of the transmitted light intensity distribution of the transmission screen 18. Therefore, it is desirable to determine the pitch according to the shape of Eyebox 4 to be illuminated.

MLA 40 and MLA 41 are arranged opposite to the positions shown in FIG. That is, the light receiving surface of the MLA 40 and the light emitting surface of the MLA 41 are arranged in parallel, and the vertex portion of the ML 40a disposed at the center of the MLA 40 and the vertex portion of the ML 41a disposed at the center of the MLA 41 are both light. It arrange | positions so that it may be located on the axis | shaft AX. Further, the vertex of the MLA 40 and the vertex of the MLA 41 are arranged with an interval of the focal length f of the ML 40a so that the light passing through the vertex of the ML 40a also passes through the vertex of the ML 40a. By disposing the

MLs

40a and 41a in this way, the transmission screen 18 has a diffusion characteristic that makes the light intensity distribution of the diffused light (display light L) substantially uniform. The substantially uniform light intensity distribution is an intensity distribution capable of irradiating within the irradiation range with a substantially uniform light intensity, and is, for example, a Top-Hat type light intensity distribution shown in FIG.

Since the transmissive screen 18 has the above-described configuration, the display light L ′ is diffused when passing through the transmissive screen 18, and the diffused display light L is efficiently irradiated within the range of Eyebox 4. On the other hand, the incident outside light incident from the outside of the windshield 3 is reflected by the exit surface of the transmission screen 18 having the inclination angle α, and the reflected outside light reaches outside the range of the Eyebox 4. For this reason, it is possible to suppress the reflected external light from leaking into Eyebox 4 and to suppress the deterioration of the visibility of the display image (display light L). In addition, by setting the inclination angle α to a predetermined angle obtained using the above formula (1), even if a part of the reflected external light leaks into the range of Eyebox 4, the visibility is improved. The influence of reflected external light is reduced to such an extent that it does not decrease.

Thus, according to the HUD device 1 according to the present embodiment, it is possible to reduce the influence of outside incident light while suppressing the light amount loss of the display light L constituting the display image. That is, since the MLA 40 is formed on the light receiving surface of the transmission screen 18 and the MLA 40 is formed on the light emitting surface thereof, the display light L can irradiate the entire area of the Eyebox 4 substantially uniformly. As a result, external light incident from the outside of the windshield 3 is similarly reflected within the range of Eyebox 4. However, since the transmissive screen 18 is tilted at an inclination angle α, only reflected external light is reflected on the Eyebox 4. Reflect outside the range. Accordingly, it is possible to suppress a decrease in the visibility of the display image.

Here, FIG. 10 shows a simulation result of the intensity distribution of the reflected external light reflected by the transmissive screen 18. In this simulation, the light intensity in the range of Eyebox 4 when the inclination angle α of the transmission screen 18 shown in FIG. 6 is changed is obtained.

Referring to FIG. 10, the brightness of the external light reflected light changes according to the tilt angle of the transmissive screen 18, and the brightness of the external light reflected light decreases as the tilt angle increases. In order not to reduce the visibility of the display light L, it is said that the brightness of the external light reflected light needs to be reduced to 50% or less of the normal light, and therefore the inclination angle of the transmissive screen 18 is set to 4 degrees or more. It has been found that it is preferable to set the inclination angle of the transmission screen 18 to 5 degrees or more. In addition, since the decrease in light intensity is steep compared to a modification example (an example in which microlenses are irregularly arranged), which will be described later, the range in which the inclination angle α can be obtained by periodically arranging microlenses. It was found that can be expanded.

As described above, according to the HUD device 1, it is possible to reduce the external light reflection and the internal reflection while suppressing the light amount loss of the display light L constituting the display image. it can.

(Modification)
In addition, this invention is not limited to the above embodiment, A various deformation | transformation is possible. A modification is shown below.

For example, in the above embodiment, in order to make the light intensity distribution of the diffused display light substantially uniform, the transmissive screen 18 and the MLA 41 are formed on the emission side, but the present invention is not limited to this. For example, as shown in FIG. 11, an aperture array 42 may be formed instead of the MLA 41. The aperture array 42 is formed by a photolithography technique or the like so that each of the plurality of openings 42a is periodically arranged at a pitch of dH ″ in the horizontal direction in the in-plane direction. Although not shown, the vertical array is formed so as to be periodically arranged at a predetermined pitch, and the aperture array 42 may be formed integrally with the MLA 40 or as a separate body. May be.

The opening 42a of the aperture array 42 is formed so as to be adjusted to about 1/5 to 1/10 of the lens size of the ML 40a. A region other than the opening 42a of the aperture array 42 is a light shielding portion 42b as illustrated. The light shielding part 42b is formed of a material that absorbs visible light, such as a black resist used in a liquid crystal panel, for example. That is, in the aperture array 42, the area other than the opening 42a on both surfaces is the surface of the light shielding part 42b. Therefore, most of the laser light that has reached the aperture array 42 other than the light that passes through the opening 42a is absorbed by the light shielding portion 42b.

Further, in order to make the light intensity distribution of the diffused display light substantially uniform, the transmission screen 18 is composed of the MLA 40 in which the ML 40a is periodically arranged. However, the present invention is not limited to this. As shown in FIG. 12, the transmissive screen 18 may be configured from a microlens array (MLA) 43 in which ML43a having different shapes are arranged at an irregular pitch. As a transmission screen having a random pitch and showing a substantially uniform intensity distribution, for example, Engineered DiffusersTM is available. It is designed with the arrangement and sag amount of the microlens calculated so as to obtain a desired diffusion angle and intensity distribution. The MLA 43 can be formed by scanning the photoresist applied on the substrate with a laser beam.
Here, FIG. 13 shows a simulation result of the intensity distribution of the intensity distribution of the reflected external light reflected by the transmission screen 18. In this simulation, the light intensity in the range of Eyebox 4 when the inclination angle α of the transmission screen 18 shown in FIG. 6 is changed is obtained. As shown in the drawing, the brightness of the external light reflected light changes according to the tilt angle of the transmission screen 18, and the brightness of the external light reflected light decreases as the tilt angle increases. Thus, it has been found that the MLA 43 in which ML 43a having different shapes are arranged at irregular pitches has the same effect as the MLA 40 in which the ML 40a is periodically arranged.

Moreover, in the above embodiment, in order to make the light intensity distribution of the diffused display light substantially uniform, the MLAs 40 and 41 are integrally formed and each is formed as a convex lens. However, the present invention is not limited to this. For example, as shown in FIGS. 14 to 16, a configuration in which a convex lens and a concave lens are appropriately combined may be used.
For example, as shown in FIG. 14A, the MLA 40A and the MLA 41A may be integrally formed, and the MLA 40A may be formed as a convex lens on the light receiving surface side, and the MLA 41A may be formed as a convex lens on the output surface side.
As shown in FIG. 14B, the MLA 40B and the MLA 41B may be configured as separate bodies, the MLA 40B may be formed as a convex lens on the light receiving surface side, and the MLA 41B may be formed as a convex lens on the output surface side. The MLA 40B and the MLA 41B are fixed by the support member 44 with a predetermined interval.
As shown in FIG. 14C, the MLA 40C and the MLA 41C may be configured as separate bodies, and the MLA 40C may be formed as a convex lens on the emission surface side, and the MLA 41C may be formed as a convex lens on the emission surface side. The MLA 40C and the MLA 41C are fixed by the support member 44 through a predetermined interval.
Further, as shown in FIG. 15A, the MLA 40D and the MLA 41D may be integrally configured, and the MLA 40D may be formed as a convex lens on the light receiving surface side, and the MLA 41D may be formed as a concave lens on the output surface side.
Further, as shown in FIG. 15B, MLA 40E and MLA 41E may be configured as separate bodies, MLA 40E may be formed as a convex lens on the light receiving surface side, and MLA 41E may be formed as a convex lens on the light receiving surface side. The MLA 40E and the MLA 41E are fixed by the support member 44 with a predetermined interval.
Further, as shown in FIG. 15C, the MLA 40F and the MLA 41F may be configured as separate bodies, the MLA 40F may be formed as a convex lens on the emission surface side, and the MLA 41E may be formed as a convex lens on the light receiving surface side. The MLA 40F and the MLA 41F are fixed by the support member 44 through a predetermined interval.
Further, as shown in FIG. 16A, MLA 40G and MLA 41G may be configured as separate bodies, and MLA 40G may be formed as a convex lens on the light receiving surface side, and MLA 41G may be formed as a concave lens on the output surface side. The MLA 40G and the MLA 41G are fixed by the support member 44 through a predetermined interval.
Further, as shown in FIG. 16B, the MLA 40H and the MLA 41H may be configured as separate bodies, and the MLA 40H may be formed as a convex lens on the exit surface side, and the MLA 41H may be formed as a concave lens on the exit surface side. The MLA 40H and the MLA 41H are fixed by the support member 44 through a predetermined interval.
Thus, the versatility of the transmissive screen 18 can be enhanced by appropriately combining a convex lens and a concave lens.

Moreover, in the above embodiment, although the shape of ML40a which MLA40 has was demonstrated as a square, it is not restricted to this. The shape of the ML 40a may be a rectangle, a hexagon, or the like. In the case of a hexagon, the MLA 40 is formed by arranging each of a plurality of MLs 40a in a honeycomb shape at a predetermined pitch.

Further, in the above embodiment, three LDs are arranged, and these emit laser beams R, G, and B, respectively, but the number of LDs is not limited to this. By arranging four LDs, a display image (display light L) may be generated with four primary colors, or a monochrome display image (display light L) may be generated with one LD.

In the above embodiment, an example of a vehicle on which the HUD device is mounted is a vehicle, but is not limited thereto. The HUD device can be mounted on an automobile, a motorcycle, a construction machine, an agricultural machine, a ship, a snow bike, and the like.

Further, although the reflector 20 is composed of one mirror of the magnifying mirror 21, the shape and the number of mirrors constituting the reflector 20 are not limited to this, and are arbitrary according to the purpose.

In addition, this invention is not limited by the above embodiment and drawing. Changes (including deletion of constituent elements) can be added to the embodiments and the drawings as appropriate without departing from the scope of the present invention.

The present invention relates to a display that is mounted on a moving body such as a vehicle and displays various kinds of information. For example, the display is mounted on various moving bodies such as an automobile, a motorcycle, a construction machine, an agricultural machine, a ship, a snow bike, and a water bike. It is possible to project a display image on a windshield (windshield), which is suitable as a head-up display device that allows the driver to visually recognize the display image as a virtual image.

1 HUD device 2 Vehicle 3 Windshield 4 Eyebox
10 Display device 11 LD (11r, 11g, 11b... LD)
12 mirror part (12a, 12b, 12c ... dichroic mirror)
13 Reflecting mirror 14 Prism (optical element)
14a Inclined surface 15 DMD (reflection type display element)
16 Optical sensor (detection element)
17 projection lens 18 transmissive screen 20 reflector 21 magnifying mirror 21a reflecting surface 22 holding member 23 stepping motor 24 gear portion 25 shaft portion 26 gear 30 housing 31 window portion 32 light shielding walls 40, 40A to 40H, 41, 41A to 41H, 43 MLA (micro lens array)
40a, 41a, 43a ML (micro lens)
42 Aperture array 42a Opening 42b Shielding portion 44 Support member R Red laser beam G Green laser beam B Blue laser beam L, L 'Display beam L1, L2, L3 Laser beam AX Optical axis V Virtual image

Claims

Display light emitting means for emitting display light constituting a display image;
A transmission screen having a light receiving surface for receiving the display light and an output surface for emitting the received display light as diffused light, and having a diffusion characteristic that makes the light intensity distribution of the diffused light substantially uniform;
With
The transmissive screen is arranged by tilting the normal line of the transmissive screen at a certain angle with respect to the optical axis of the display light, and external light reaching the emission surface along the optical axis of the display light. Reflecting in a direction different from the direction along the optical axis of the display light,
A head-up display device.
The inclination angle formed between the normal line of the transmission screen and the optical axis is α,
Α is calculated by the following formula (1).

The head-up display device according to claim 1.