JP2016065907A - Head-up display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a head-up display device that can suppress decrease in use efficiency of light or decrease in luminance uniformity of a displayed image.SOLUTION: A head-up display device 100 projects display light L emitted from a display unit 3 comprising a backlight unit 1 and a liquid crystal display element 2 onto a viewing region of an observer by projection means so as to allow the observer to visually recognize an image represented by the display light L. The backlight unit 1 includes: a light source 10 that emits light I to illuminate the liquid crystal display element 2; a lens array 40 that divides the light I exiting from the light source 10 to produce a plurality of images of the light source 10; and condensing means 51, 52 that condenses the light I exiting from images of the light source 10 to be mapped to the display region of the liquid crystal display element 2. The condensing means 51, 52 is configured to have different focal lengths between in a vertical direction and in a lateral direction so as to correct a difference in the focal length of the projection means between in the vertical direction and in the lateral direction.SELECTED DRAWING: Figure 3

Description

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

  As a display for displaying a predetermined image, a display having a configuration in which a liquid crystal display element is transmitted and illuminated with a backlight is known. Patent Document 1 discloses a display device called a so-called head-up display (HUD) device that includes a display device having such a configuration. The HUD device projects display light from the display onto the windshield of the vehicle, thereby allowing a user (mainly a driver) to visually recognize a predetermined image as a display image (virtual image).

  In the display device according to Patent Document 1, a condensing illumination optical system is used for the backlight, and a condenser lens (parallel light generating means) is provided on the optical path from the light source for the backlight to the liquid crystal display element. By arranging a lens array and a field lens (also referred to as a focus lens, condensing means), a backlight unit is configured behind the liquid crystal display element. In the HUD device according to Patent Document 1, a light beam emitted from a divided image of a light source generated by a lens array is refracted by a field lens and enters a liquid crystal display element at a predetermined angle. The principal ray incident on the liquid crystal display element is emitted as display light from the liquid crystal display element at an angle substantially equal to the incident angle, and passes through a projection optical system mainly composed of a concave mirror and a windshield, so that the user's viewpoint area (eye box) Concentrate in the vicinity.

JP 2012-203176 A

  The HUD device according to Patent Document 1 is based on the premise that the image magnification of the HUD device, that is, the focal length of the projection optical system is equal in the vertical and horizontal directions of the display image, and the curved shape of the field lens is on the optical axis. On the other hand, it is rotationally symmetric. However, the HUD device mounted on the vehicle mainly corrects the distortion of the display image generated on the windshield, is housed in a limited mounting space, and has a design constraint such as arranging a member for preventing stray light. Depending on the vehicle type, the focal length of the projection optical system may differ between the vertical direction and the horizontal direction. In that case, the concentration of the display light in the viewpoint region may deteriorate, and the light use efficiency may decrease, or the luminance uniformity of the display image viewed from a predetermined viewpoint may decrease.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a HUD device capable of suppressing a decrease in light utilization efficiency and a decrease in luminance uniformity of a display image.

In order to achieve the above object, a head-up display device according to the present invention projects display light emitted from a display device including a backlight unit and a display element onto a viewpoint area of an observer via a projection unit. A head-up display device for visually recognizing an image represented by light,
The backlight unit is
A light source that emits light for illuminating the display element;
A lens array that divides light emitted from the light source to generate a plurality of images of the light source;
Condensing means for condensing the light emitted from the image of the light source so as to correspond to the display area of the display element,
The condensing unit is configured to have different focal lengths in the vertical direction and the horizontal direction so as to correct a difference in focal length between the vertical direction and the horizontal direction of the projection unit. .

  According to the present invention, it is possible to suppress a decrease in light utilization efficiency and a decrease in luminance uniformity of a display image.

It is a schematic diagram for demonstrating the mounting aspect of the HUD apparatus which concerns on one Embodiment of this invention. It is a schematic sectional drawing of the HUD apparatus which concerns on one Embodiment of this invention. FIG. 3 is an enlarged view of the vicinity of the display of the HUD device shown in FIG. 2. 1 is a schematic exploded perspective view of a backlight unit according to an embodiment of the present invention. It is a schematic diagram for demonstrating the function of the backlight unit which concerns on one Embodiment of this invention, (a) The cross-sectional view of embodiment and a comparative example, (b) The longitudinal cross-sectional view of a comparative example, (c) Implementation It is a longitudinal cross-sectional view of a form. It is a front view which shows the lens array which concerns on one Embodiment of this invention. It is a figure which shows the 2nd focus lens which concerns on one Embodiment of this invention. It is a transverse cross section of the mimetic diagram for explaining the function of the backlight unit concerning the conventional technology. It is a cross-sectional view showing a lens array according to an embodiment of the present invention. It is a cross-sectional view showing another example of a lens array according to an embodiment of the present invention.

  A head-up display (HUD) device according to an embodiment of the present invention will be described with reference to the drawings.

  The HUD device 100 according to the present embodiment is provided so as to be embedded in the dashboard of the vehicle C as shown in FIG. As shown in FIG. 2, the HUD device 100 includes a display unit 3 including a backlight unit 1 and a liquid crystal display element 2 (display element), a plane mirror 4, a concave mirror 5, a housing 6, and a protective member 7. .

  The HUD device 100 projects the display light L emitted from the display device 3 onto the windshield S (front glass) of the vehicle C, so that the image represented by the display light L is a virtual image V (display image). To the driver). The display light L emitted from the display 3 is obtained by transmitting and illuminating the liquid crystal display element 2 with the light from the backlight unit 1 and represents a predetermined image.

  As shown in FIG. 3, the backlight unit 1 includes a light source 10, parallel light generation means 20, illuminance equalization means 30, a lens array 40, a first focus lens 51, and a second focus lens 52. And a reflection part 60, a diffusion plate 70, a case body 80, and a cover member 90.

  The parallel light generation unit 20, the illuminance equalization unit 30, the lens array 40, the first focus lens 51, the second focus lens 52, the reflection unit 60, and the diffusion plate 70 are on the optical path of the light emitted from the light source 10. Has been placed. From the light source 10 toward the liquid crystal display element 2, the parallel light generating means 20, the illuminance uniformizing means 30, the lens array 40, the first focus lens 51, the reflection unit 60, the second focus lens 52, and the diffusion plate They are arranged in the order of 70. The light source 10, the parallel light generation unit 20, the lens array 40, the first focus lens 51, and the second focus lens 52 constitute an illumination optical system of the HUD device 100. The backlight unit 1 is composed of a concave mirror 5 and a windshield S for displaying light L transmitted through the liquid crystal display element 2 while irradiating light emitted from the light source 10 evenly to the display area A of the liquid crystal display element 2. The front surface of the liquid crystal display element 2 (the surface facing upward in FIG. 2 and FIG. 3) so as to be guided into the eye box EB (viewpoint region) of the user U via the projection means (projection optical system) of the HUD device 100 ) To control the angle of the display light L emitted from (see FIG. 5).

  The light source 10 emits light that transmits through the liquid crystal display element 2 (hereinafter also referred to as illumination light I). The light source 10 includes, for example, two LEDs (Light Emitting Diodes). In addition, the light source 10 may be comprised from 1 or 3 or more LED. The light source 10 is mounted on a circuit board 11 (see FIG. 4) fixed to the case body 80. The circuit board 11 is formed by forming a circuit pattern on a base material made of aluminum, resin, or the like, and is conductively connected to a control unit (not shown) described later by a known method. The light source 10 is thermally connected to a heat radiating member (not shown). The heat radiating member is a fin-type structure made of, for example, a metal material such as aluminum, and emits heat generated by the light source 10 to the outside.

  The parallel light generation means 20 receives the illumination light I from the light source 10 and emits it as parallel light. Here, the parallel light is light that travels substantially parallel (including exactly parallel) to the optical axis AX (see FIG. 3) of the light source 10. The parallel light generating means 20 is composed of, for example, a condenser lens. The condenser lens is a convex lens made of an engineering resin material, and one lens corresponds to one light source 10. When using the several light source 10, the form of the collective lens by which multiple convex lens parts are arrange | positioned is taken. When it is desired to keep the distance between the lens curved surfaces apex (lens thickness) below a predetermined thickness for the convenience of manufacturing, the parallel light generation unit 20 maintains or increases the amount of the illumination light I while maintaining the parallel light generation unit 20. Depending on the use, it may be configured with two or more lenses, for example, when it is desired to further increase the parallelism of the light emitted from 20. Further, since the parallel light generating means 20 is disposed in the vicinity of the light source 10, it is preferable to use an optical resin material having excellent heat resistance in consideration of the influence of heat generated from the light source 10. Furthermore, other known optical elements such as a collimating lens may be employed as the parallel light generating means 20.

  The illuminance uniformizing means 30 is for making the illumination light I made parallel light by the parallel light generating means 20 incident and uniforming the illuminance distribution of the light on the exit side. The illuminance uniforming means 30 is composed of, for example, a light box. This light box is a rectangular tube-shaped member surrounding the optical axis AX, and the inner surface (the surface on the optical axis AX side) is a mirror surface. The illuminance equalizing means 30 may be another known light box provided with a light diffusing plate, a light reflecting plate, or the like.

As shown in the front view of FIG. 6 (showing the liquid crystal display element 2 side), the lens array 40 is a lens assembly in which a plurality of minute lenses 41 are arranged vertically and horizontally, and is called a so-called fly-eye lens. is there. The lens 41 is, for example, a so-called biconvex lens in which both the light source 10 side and the liquid crystal display element 2 side have the same convex shape. Each optical axis of the lens 41 is parallel to the optical axis of the parallel light generating means 20.
Illumination light I that has been substantially collimated by the parallel light generating means 20 and whose illuminance is substantially uniformized by the illuminance uniformizing means 30 is incident on the lens array 40. Since the lens array 40 generates multiple images (intermediate images) as many as the number of lenses 41 constituting the lens array 40, an enlarged image of the single light source 10 generated by the parallel light generation unit 20 (illumination light emitted from the light source 10). I) is divided by the number of lenses 41 of the lens array 40 to form a multiple image. Accordingly, the liquid crystal display element 2 can be illuminated with a uniform light intensity distribution even with a small number of light sources 10.
The region where the lens 41 of the lens array 40 is arranged has a rectangular shape according to the display region A of the liquid crystal display element 2, and is centered with respect to the longitudinal direction of the rectangular shape (the horizontal direction in FIG. 6). When divided into three regions: a central portion 40A, a left peripheral portion 40B located on the left side of the central portion 40A, and a right peripheral portion 40C located on the right side of the central portion 40A, the left and right peripheral portions 40B , 40C, the lenses 41 are formed such that the pitch array of the lenses 41 (the distance between the apexes of the two adjacent lenses 41) is different from the array pitch of the lenses 41 in the central portion 40A. Specifically, each lens 41 is formed such that the array pitch of the lenses 41 in the left and right peripheral portions 40B and 40C is larger than the array pitch of the lenses 41 in the central portion 40A. As described above, the operation in which the array pitch of the peripheral lenses 41 is different from the array pitch of the central lens 41 will be described in detail later.

  The first focus lens 51 and the second focus lens 52 are, for example, convex lenses made of an optical resin material, and the illumination light I emitted from the multiple images of the light source 10 generated by the lens array 40 is converted into a liquid crystal display element. It functions as a condensing means for condensing light so as to correspond to the display area A of 2 (see FIG. 5). Specifically, the first focus lens 51 and the second focus lens 52 cooperate with each other on the back surface corresponding to the displayable range (display area A) of the image displayed on the front surface of the liquid crystal display element 2. The illumination light I from the lens array 40 is irradiated over the entire surface. As a result, the illumination light I representing the multiple image generated by the lens array 40 can be efficiently applied to a necessary range on the back surface of the liquid crystal display element 2. At this time, by optimizing the focal length and the optical arrangement of the first and second focus lenses 51 and 52 with respect to the multiple image, the angle of the illumination light I applied to the back surface of the liquid crystal display element 2 is set to a predetermined value. Get close to. Thereby, the light distribution angle of the display light L emitted from the front surface of the liquid crystal display element 2 can be controlled, and the irradiation efficiency of the display light L to the eye box EB can be improved.

  The condensing means constituted by the first and second focus lenses 51 and 52 corrects the difference in focal length between the vertical direction and the horizontal direction of the projection means constituted by the concave mirror 5 and the windshield S. As described above, the focal length is different between the vertical direction and the horizontal direction. Specifically, at least one of the first focus lens 51 and the second focus lens 52 is configured as a toroidal lens. In other words, at least one of the four surfaces of both the first focus lens 51 and the second focus lens 52 is an aspherical surface having different aspherical curvatures in the orthogonal vertical direction and the horizontal direction. Configure as. In this embodiment, as shown in FIG. 7, both surfaces of the second focus lens 52 are toroidal surfaces, and the vertical (vertical) focal length and the horizontal (horizontal) focal length are different from each other. I did it. 7A is a front view of the second focus lens 52 (showing the liquid crystal display element 2 side), and FIG. 7B is a longitudinal sectional view of the second focus lens 52. FIG. (C) is a cross-sectional view of the second focus lens 52. Thus, the effect | action by varying the focal distance in the vertical direction and the horizontal direction of the said condensing means is explained in full detail later. In addition, as a method of making the focal lengths of the light collecting means different in the vertical direction and the horizontal direction, at least one curved surface may be a free curved surface in the optical member constituting the light collecting means.

The reflection unit 60 is disposed between the first focus lens 51 and the second focus lens 52. The reflection part 60 is comprised from the plane mirror which vapor-deposited metals, such as aluminum, to the base material which consists of resin, glass etc., and formed the reflective surface 61, for example. The reflection unit 60 is disposed such that the reflection surface 61 is inclined with respect to the optical axis AX of the light source 10. The illumination light I from the first focus lens 51 is reflected by the reflecting surface 61 and enters the second focus lens 52.
In this embodiment, as shown in FIG. 3, the reflection unit 60 is arranged so that the optical path of the illumination light I from the reflection unit 60 to the liquid crystal display element 2 is substantially orthogonal to the optical axis AX of the light source 10. ing. In this way, the reflection unit 60 changes the optical path of the illumination light I.

  The diffusing plate 70 is made of, for example, a synthetic resin material having at least one surface subjected to uneven processing, and has translucency. The illumination light I from the second focus lens 52 is diffused by passing through the diffusion plate 70 and reaches the back surface of the liquid crystal display element 2. In this way, by providing the diffusion plate 70, uneven illumination of the liquid crystal display element 2 is reduced.

  The case body 80 is formed in a box shape from resin or the like, and accommodates the light source 10, the parallel light generation unit 20, the illuminance uniformization unit 30, the lens array 40, the first focus lens 51, and the reflection unit 60. . As shown in FIG. 4, the case body 80 has an upper opening 81 and a side opening 82. The upper opening 81 opens toward the liquid crystal display element 2 side. The side opening 82 opens toward the light source 10 side. The upper opening 81 and the side opening 82 communicate with each other. The circuit board 11 is provided so as to close the side opening 82. The circuit board 11 is fixed to the case body 80 by fixing means (not shown) such as screws. Thereby, the light source 10 is disposed so as to emit light toward the inside of the case body 80. A second focus lens 52 is provided so as to cover an end of the upper opening 81 opposite to the light source 10. A cover member 90 is provided so as to close the upper opening 81.

  As shown in FIG. 4, the cover member 90 is formed in a plate shape from resin or the like and covers the upper opening 81 of the case body 80. The cover member 90 is fixed to the case body 80 by fixing means such as screws 90b. The cover member 90 has an opening 91 through which the second focus lens 52 can be seen. The opening 91 has a shape corresponding to the lens surface shape of the second focus lens 52.

The case body 80 and the cover member 90 constitute a casing of the backlight unit 1.
As described above, since the optical parts such as the illuminance uniforming means 30, the first focus lens 51, and the reflection unit 60 are installed in one case body 80, the assembly of the backlight unit 1 is also possible. It has become easy. In addition, since the cover member 90 covers a portion other than the necessary portion (that is, other than the opening 91 through which the second focus lens 52 can be seen), the illumination light I leaks unnecessarily to the outside of the backlight unit 1. Can be prevented.

  The liquid crystal display element 2 is configured, for example, by providing polarizing plates on the front and back of a TFT (Thin Film Transistor) type liquid crystal panel. The liquid crystal panel constituting the liquid crystal display element 2 may be a passive drive type. Various types of liquid crystal panels such as a TN (Twisted Nematic) type, a VA (Vertical Alignment) type, an STN (Super Twisted Nematic) type, and a ferroelectric type are applicable.

The liquid crystal display element 2 displays a predetermined image on the display area A by switching each pixel constituting the display area A to a transmissive state or a non-transmissive state under the control of a control unit (not shown). indicate. The display area A has a rectangular shape extending in the horizontal direction. For example, the control unit acquires various types of vehicle information transmitted from an ECU (Electronic Control Unit) of the vehicle C through a communication line, and causes the liquid crystal display element 2 to display an image indicating vehicle speed, fuel consumption, and the like. At the same time, the control unit causes the light source 10 to emit light. Thereby, the liquid crystal display element 2 is transmitted and illuminated by the illumination light I generated by the backlight unit 1, and the display light L representing the display image is emitted from the liquid crystal display element 2.
In this way, the display light L is emitted from the display device 3 constituted by the backlight unit 1 and the liquid crystal display element 2.

  Returning to FIG. 2, the plane mirror 4 is formed by depositing a metal such as aluminum on a base material made of resin, glass or the like to form a reflection surface. The plane mirror 4 reflects the display light L emitted from the display 3 toward the concave mirror 5.

The concave mirror 5 is formed by depositing a metal such as aluminum on a substrate made of resin, glass or the like to form a reflective surface. The reflecting surface of the concave mirror 5 is concave. The display light L from the display 3 is magnified by the concave mirror 5 and incident on the windshield S, reflected by the windshield S, and projected onto the eye box EB of the user U. Thereby, the virtual image V visually recognized by the user U becomes the magnitude | size to which the image currently displayed on the indicator 3 was expanded.
In this way, the display light L emitted from the display device 3 is projected onto the eye box EB of the user U through the projection means constituted by the concave mirror 5 and the windshield S so that the virtual image V is visually recognized.

  The housing 6 is formed in a box shape from resin or the like, and accommodates the plane mirror 4 and the concave mirror 5 therein. The plane mirror 4 and the concave mirror 5 are fixed inside the housing 6 by a known method.

As shown in FIG. 2, the housing 6 has an upper opening 6a and a lower opening 6b. The upper opening 6a opens toward the windshield S and functions as an exit through which the display light L passes outside the HUD device 100. The lower opening 6b is located on the opposite side of the housing 6 from the upper opening 6a, and the liquid crystal display element 2 is disposed at the lower end thereof (the end in the downward direction in FIG. 2). In this way, the lower opening 6 b is formed so that the display surface of the liquid crystal display element 2 can be viewed toward the inside of the housing 6.
As described above, the housing 6 is formed so as to surround the optical path of the display light L from the liquid crystal display element 2 to the upper opening 6a that functions as an emission port.

  As shown in FIG. 2, the backlight unit 1 is attached to the housing 6 from the outside of the housing 6 and from the lower opening 6b side. For example, the backlight unit 1 is attached to the casing 6 by fixing the case body 80 to the casing 6 with fixing means such as screws 8. At this time, the backlight unit 1 is attached so that the opening 91 (see FIG. 4) of the cover member 90 covering the case body 80 communicates with the lower opening 6b (see FIG. 2) of the housing 6. .

  The protective member 7 is made of resin or the like, and is fixed to the casing 6 by a predetermined method so as to cover the backlight unit 1 attached to the casing 6 from the lower side (the lower side in the drawing of FIG. 2). . The protective member 7 provided in this way protects the backlight unit 1 from dust, vibration, and the like.

To briefly describe a mechanism that enables the HUD device 100 to visually recognize a predetermined image as a virtual image V for the user U, the following (1) and (2) are obtained.
(1) The display light L is emitted when the display 3 displays an image. The display light L from the display 3 is reflected by the plane mirror 4 and the concave mirror 5 and travels toward the windshield S. In this way, the HUD device 100 emits the display light L toward the windshield S.
(2) When the display light L from the HUD device 100 is reflected by the windshield S, a virtual image V of the display image is formed in front of the windshield S when viewed from the user U.

  Next, the light condensing means (first and second focus lenses 51 and 52) so as to correct the difference in focal length between the vertical direction and the horizontal direction of the projection means (concave mirror 5 and windshield S). The operation of configuring the light condensing means so that the focal lengths in the vertical and horizontal directions are different will be described with reference to FIG. Hereinafter, the focal lengths of the projection means in the vertical direction and the horizontal direction are the same, that is, all the curved surfaces of the first and second focus lenses 51 and 52 constituting the light condensing means are axially symmetric curved surfaces. A case will be described as a comparative example. FIG. 5A is a schematic cross-sectional view for explaining the function of the backlight unit 1 (illumination optical system) in this embodiment and a comparative example, and FIG. 5B is a back view in the comparative example. It is a longitudinal cross-sectional view of the schematic diagram for demonstrating the function of the light unit 1, FIG.5 (c) is a longitudinal cross-sectional view of the schematic diagram for demonstrating the function of the backlight unit 1 in this embodiment. In FIGS. 5A to 5C, the first and second focus lenses 51 and 52 are shown as one convex lens, and the concave mirror 5 and the windshield S are shown as one convex lens for easy viewing of the drawing. It was. Further, in order to facilitate understanding of the function of the backlight 1, the horizontal sectional view of FIG. 5A and the vertical sectional views of FIG. 5B and FIG. 5C, regardless of the actual shape of each part, The length of each part in the horizontal direction (vertical direction on the paper surface in FIG. 5A) and the length in the vertical direction (vertical direction on the paper surface in FIGS. 5B and 5C) are shown to be equal (actually). Each part except the light source 10 has a shape extending in the lateral direction).

  As described above, in the HUD device 100 mounted on the vehicle C, the focal length of the projection unit may be different between the vertical direction and the horizontal direction depending on the vehicle type due to various design restrictions. In that case, unless any countermeasure is taken, the light collection degree of the display light L in the eye box EB deteriorates in the vertical direction or the horizontal direction. Specifically, for example, when designing the focal length of the condensing unit according to the lateral direction of the projection unit, as shown in FIG. 5A, the display light L with respect to the lateral direction of the eye box EB. Since the image is formed at an arbitrary point on the eye box EB, the degree of image formation of the display light L, that is, the degree of condensing is high. However, as shown in FIG. Since the light L forms an image at a position outside the eye box EB, the light collection degree of the display light L is deteriorated. When the light collection degree of the display light L is deteriorated, the display light L guided outside the eye box EB is increased, and the light use efficiency is lowered. Further, the virtual image V viewed from an arbitrary viewpoint has a luminance variation, and the luminance uniformity. May decrease. FIG. 5B shows a case where the vertical focal length of the projection means is longer than the horizontal focal length.

  On the other hand, in this embodiment, the focal length of the condensing means is made different between the vertical direction and the horizontal direction so as to correct the difference in focal length between the vertical direction and the horizontal direction of the projection means. In this way, as shown in FIG. 5 (a), in the lateral direction of the eye box EB, while maintaining the same high light concentration as in the prior art, the longitudinal direction of the eye box EB as shown in FIG. 5 (c). However, by changing the focal length of the condensing means, the focal length of the entire HUD device 100 is matched in the horizontal direction and the vertical direction so that the display light L forms an image at an arbitrary point on the eye box EB. Thus, the concentration of the display light L can be kept high. Note that FIG. 5C shows that the vertical focal length of the second focus lens 52 of the light converging means depends on the situation where the vertical focal length of the projection means is longer than the horizontal focal length. The case where it is configured to be shorter than the focal length in the horizontal direction (the curvature of the curved surface in the vertical direction is changed) is shown. Although the image enlargement ratio of the virtual image V differs between the vertical direction and the horizontal direction due to the difference in focal length between the vertical direction and the horizontal direction of the projection unit, the size of the image displayed on the liquid crystal display element 2 is different. The difference in image magnification can be corrected by making the difference in the vertical direction and the horizontal direction.

なお、ｄは、前記照明光学系の中心点と前記投射手段の中心点との間の距離である。
まず、アイボックスＥＢの位置及び虚像Ｖの像拡大率、さらに虚像Ｖの歪みや搭載性などの設計上の制約を考慮して、前記投射手段の縦方向及び横方向の焦点距離ｆｂが定められる。次に、前記照明光学系の縦方向及び横方向の焦点距離ｆａの一方を計算や任意の値の設定などにより算出し、上記の数式１に基づいてＨＵＤ装置１００全体の縦方向及び横方向の焦点距離ｆ（ａ+ｂ）の一方を算出する。さらに、ＨＵＤ装置１００全体の縦方向及び横方向の焦点距離ｆ（ａ+ｂ）の他方が、先に算出した一方と等しい値となるように、数式１に基づいて前記照明光学系の縦方向及び横方向の焦点距離ｆａの他方を算出する。さらに、照明シミュレーションによって、算出した前記照明光学系の縦方向及び横方向の焦点距離ｆａを調整する。このようにして得られた前記照明光学系の縦方向及び横方向の焦点距離ｆａに基づいて、前記集光手段（この実施形態では第２のフォーカスレンズ５２）の縦方向及び横方向の焦点距離を設計する。このようにして、前記投射手段の縦方向と横方向とでの焦点距離を補正するように、前記集光手段の焦点距離を縦方向と横方向とで異ならせることができる。 Hereinafter, a specific method for designing the focal length of the light collecting means will be described.
The focal length of the illumination optical system (light source 10, parallel light generation means 20, lens array 40, first and second focus lenses 51, 52) of the HUD device 100 is set to fa, and the projection means (concave mirror) of the HUD device 100 is used. 5. When the focal length of the windshield S) is fb, and the focal length of the entire HUD device 100 including the illumination optical system and the projection means is f (a + b), the focal length f ( a + b) can be expressed by Equation 1 below.

D is the distance between the center point of the illumination optical system and the center point of the projection means.
First, in consideration of design constraints such as the position of the eye box EB and the image magnification ratio of the virtual image V, and the distortion and mountability of the virtual image V, the vertical and horizontal focal lengths fb of the projection unit are determined. . Next, one of the longitudinal focal length fa and the lateral focal length fa of the illumination optical system is calculated, set by setting an arbitrary value, and the like, and the vertical and lateral directions of the entire HUD device 100 are calculated based on the above formula 1. One of the focal lengths f (a + b) is calculated. Further, the vertical direction of the illumination optical system based on Formula 1 is set so that the other of the focal lengths f (a + b) in the vertical direction and the horizontal direction of the entire HUD device 100 is equal to the previously calculated one. And the other of the lateral focal lengths fa. Further, the calculated longitudinal focal length fa of the illumination optical system is adjusted by illumination simulation. Based on the focal length fa in the vertical and horizontal directions of the illumination optical system obtained in this way, the focal lengths in the vertical and horizontal directions of the condensing means (in this embodiment, the second focus lens 52). To design. In this way, the focal length of the light collecting means can be made different between the vertical direction and the horizontal direction so as to correct the focal length of the projection means in the vertical direction and the horizontal direction.

Next, the operation of changing the array pitch of the lenses 41 between the left and right peripheral portions 40B and 40C and the central portion 40A of the lens array 40 will be described with reference to FIGS. FIG. 8 is a schematic cross-sectional view for explaining the function of the lens array 40, and FIG. 9 is a diagram showing the lenses 41 of the lens array 40.
As described above, the lens array 40 is an aggregate of minute lenses 41, and when the illumination light I substantially collimated by the parallel light generation unit 20 enters the lens array 40, the incident side ( The light source 10 side) is refracted by the curved surface and condensed near the exit side (liquid crystal display element 2 side) curved surface to form a multiple image. At this time, if no measures are taken, the light distribution angle of each lens 41 is the same regardless of the position of the lens 41, and the optical axis is caused by the aberration of the first and second focus lenses 51 and 52 as shown in FIG. The irradiation range of the illumination light I directed from the multiple images toward the liquid crystal display element 2 becomes narrower as the distance from AX increases. In FIG. 8, the illumination light I emitted from the image of the light source 10 formed by the lens 41 overlapping the optical axis AX is displayed on the display area A of the liquid crystal display element 2 via the first and second focus lenses 51 and 52. Although illuminated as a whole, the illumination light I emitted from the image of the light source 10 collected by the lens 41 separated from the optical axis AX in the left-right direction of the lens array 40 (vertical direction in the drawing in FIG. 8) is the first. Even through the second focus lenses 51 and 52, a part (edge part) of the display area A of the liquid crystal display element 2 is not irradiated, and illumination unevenness occurs. The HUD device 100 has high directivity because the member to which the display light L is finally projected is the windshield S with low light diffusibility, and uneven illumination on the liquid crystal display element 2 causes the luminance of the display image (virtual image V). Easily reflected in unevenness.

  On the other hand, in this embodiment, the lens pitch is different between the left and right peripheral portions 40B and 40C and the central portion 40A by changing the array pitch of the lenses 41 between the left and right peripheral portions 40B and 40C and the central portion 40A of the lens array 40. The light distribution angle of 41 was made different. Specifically, the array pitch of the lenses 41 in the left and right peripheral portions 40B and 40C is set so that the light distribution angle in the left and right peripheral portions 40B and 40C is larger than the light distribution angle in the central portion 40A. Each lens 41 was formed to be larger than the pitch. As the array pitch increases, the size of the curved surface increases, and as a result, the light distribution angle increases. FIG. 9A shows each lens 41 in the central portion 40A, and FIG. 9B shows each lens 41 in the left and right peripheral portions 40B and 40C. 9A and 9B are cross-sectional views. The array pitch W2 of the lenses 41 in the left and right direction (up and down direction in FIG. 9) of the lens array 40 corresponding to the longitudinal direction of the liquid crystal display element 2 in the left and right peripheral portions 40B and 40C is the left and right direction of the lens 41 in the central portion 40A. As a result of being formed larger than the array pitch W1 (W2> W1), the light distribution angle θ2 of the lens 41 in the left and right peripheral portions 40B and 40C becomes larger than the light distribution angle θ1 of the lens 41 in the central portion 40A. Therefore, also in the left and right peripheral portions 40B and 40C, it is possible to extend the irradiation range of the illumination light I emitted from the image of the light source 10 formed by the lens 41 and irradiate the entire display area A of the liquid crystal display element 2. Note that the lengths of the entire lens array 40 in the vertical direction and the horizontal direction are determined according to the light distribution angle of the display light L on the front surface of the liquid crystal display element 2. For example, when the focal lengths of the first and second focus lenses 51 and 52 are fixed, the light distribution angle of the display light L in the liquid crystal display element 2 increases as the entire length of the lens array 40 increases.

  As a method of making the light distribution angle of the lens 41 different between the left and right peripheral portions 40B and 40C and the central portion 40A of the lens array 40, the curved shape and / or thickness of the lens 41 is different in addition to the array pitch described above. The focal length of the lens 41 may be varied. In this case, specifically, as shown in FIG. 10, the focal length of the lens 41 in the left and right peripheral portions 40B and 40C is made shorter than the focal length of the lens 41 in the central portion 40A, so that in the left and right peripheral portions 40B and 40C. The light distribution angle θ2 (FIG. 10B) of the lens 41 can be made larger than the light distribution angle θ1 (FIG. 10A) of the lens 41 in the central portion 40A.

In the first aspect, the HUD device 100 described above emits the display light L emitted from the display 3 including the backlight unit 1 and the liquid crystal display element 2 through the projection means (concave mirror 5 and windshield S). A head-up display device 100 that projects onto a viewpoint region (eye box EB) of an observer (user U) and visually recognizes a virtual image V. The backlight unit 1 illuminates a liquid crystal display element 2 (illumination light I). ), A lens array 40 that divides the light emitted from the light source 10 to generate a plurality of images of the light source 10, and the light emitted from the image of the light source 10 into the display area A of the liquid crystal display element 2. Condensing means (first and second focus lenses 51 and 52) for condensing so as to correspond to the above, the condensing means is a focal point in the vertical direction and the horizontal direction of the projection means Focal length in the the vertical direction and the horizontal direction are configured differently so as to correct the difference in release.
With this configuration, the focal length of the entire HUD device 100 is matched in the horizontal direction and the vertical direction so that the display light L forms an image at an arbitrary point on the eye box EB, and the concentration of the display light L Can be kept high. Therefore, it is possible to suppress a decrease in light utilization efficiency and a decrease in luminance uniformity of the virtual image V.

In the HUD device 100, the condensing means is composed of one or more focus lenses, and at least one surface of the focus lenses is a toroidal surface or a free-form surface.
According to this, the focal distance of the said condensing means can be easily varied by the vertical direction and a horizontal direction.

The HUD device 100 is mounted on a vehicle (vehicle C), and the projection means includes at least the windshield S of the vehicle.
According to this, even when a difference in focal length occurs between the vertical direction and the horizontal direction of the projection means due to the windshield S, the concentration of the display light L can be kept high, and the light utilization efficiency decreases. And a decrease in luminance uniformity of the virtual image V can be suppressed.

Further, in the second aspect, the HUD device 100 allows the observer to display the display light L emitted from the display 3 including the backlight unit 1 and the liquid crystal display element 2 through the projection means (concave mirror 5 and windshield S). A head-up display device 100 that projects on a viewpoint area (eye box EB) of (user U) and visually recognizes an image represented by the display light L, and the backlight unit 1 illuminates the liquid crystal display element 2 (illumination) A light source 10 that emits light I) and a plurality of lenses 41 are arranged, a lens array 40 that divides the light emitted from the light source 10 to generate a plurality of images of the light source 10, and the light source 10 that emits light. Light collecting means (first and second focus lenses 51 and 52) for collecting the light so as to correspond to the display area A of the liquid crystal display element 2, and the lens array 40 includes: Light distribution angle θ2 of the lens 41 is configured to be different from the angle of light distribution θ1 of the lens 41 in the center of the sides.
With this configuration, the illumination light I from the image of the light source 10 generated by the lens 41 is also emitted from the liquid crystal display element 2 around the lens array 40 regardless of the aberrations of the first and second focus lenses 51 and 52. The entire display area A can be irradiated, and uneven illumination in the display area A of the liquid crystal display element 2 can be suppressed.

The lens array 40 is configured such that the array pitch W2 of the peripheral lenses 41 is larger than the array pitch W1 of the central lens 41.
Thereby, the light distribution angle θ2 of the peripheral lens 41 can be easily made different from the light distribution angle θ1 of the central lens 41.

Further, the lens array 40 may be configured such that the focal length of the peripheral lens 41 is shorter than the focal length of the central lens 41.
Thereby, the light distribution angle θ2 of the peripheral lens 41 can be easily made different from the light distribution angle θ1 of the central lens 41.

In addition, the lens array 40 includes the lenses 41 arranged in a rectangular shape, and the light distribution angle θ2 of the lens 41 in the periphery is different from the light distribution angle θ1 of the lens 41 in the center with respect to the longitudinal direction of the rectangle. It is configured.
According to this, the illumination unevenness in the display area A of the liquid crystal display element 2 can be suppressed in the region where the distance from the optical axis AX is far and the illumination unevenness is more likely to occur. Even when the lens 41 is arranged in a rectangular shape in the lens array 40, if the overall size is large, the light distribution angle of the lens 41 in the periphery also in the rectangular short direction. May be different from the light distribution angle of the lens 41 at the center.

  In addition, this invention is not limited to said embodiment, A various deformation | transformation is possible.

  In the above, an example in which the condensing unit is configured by two focus lenses has been described, but the condensing unit may be configured by one or three or more focus lenses. Further, the light collecting means may include a concave mirror.

  In addition, as long as the illumination performance of the liquid crystal display element 2 is satisfied, in the backlight unit 1, optical components such as a lens and a reflector other than the reflection unit 60 can be appropriately added or deleted.

  Further, the HUD device 100 can be configured without using either the plane mirror 4 or the concave mirror 5 or can be configured without using any of them.

  Moreover, although the above description showed the example which makes the user U visually recognize the display image by reflecting the display light L with the windshield S of the vehicle C, it is not restricted to this. The HUD device 100 may include a dedicated combiner, and the display image may be visually recognized by reflecting the display light L with the combiner.

  In the above description, an example of a vehicle on which the HUD device 100 is mounted is the vehicle C, but is not limited thereto. The HUD device 100 may be mounted on another vehicle such as a motorcycle, a construction machine, an agricultural machine, a ship, an aircraft, or the like.

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 is suitable for a head-up display device.

DESCRIPTION OF SYMBOLS 100 HUD apparatus 1 Backlight unit 10 Light source 20 Parallel light production | generation means 30 Illuminance equalization means 40 Lens array 40A Center part 40B Left periphery part 40C Right periphery part 41 Lens 51 1st focus lens 52 2nd focus lens 60 Reflection part DESCRIPTION OF SYMBOLS 70 Diffuser 80 Case body 90 Cover member I Illumination light 2 Liquid crystal display element 3 Display 6 Case 6a Upper opening part (output port)
L Display light V Virtual image U User

Claims (3)

A head-up display device that projects display light emitted from a display device including a backlight unit and a display element onto a viewer's viewpoint area through a projection unit to visually recognize an image represented by the display light,
The backlight unit is
A light source that emits light for illuminating the display element;
A lens array that divides light emitted from the light source to generate a plurality of images of the light source;
Condensing means for condensing the light emitted from the image of the light source so as to correspond to the display area of the display element,
The condensing unit is configured to have different focal lengths in the vertical direction and the horizontal direction so as to correct a difference in focal length between the vertical direction and the horizontal direction of the projection unit. Head-up display device. The condensing means is composed of one or more focus lenses,
The head-up display device according to claim 1, wherein at least one surface of the focus lens is a toroidal surface or a free-form surface. Mounted on the vehicle,
The head-up display device according to claim 1, wherein the projection unit includes at least a windshield of the vehicle.

Images