JP2016180922A - Head-up display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the luminance of a display image and improve the uniformity of the luminance without increasing the manufacturing cost and the size of the device.SOLUTION: A head-up display device 10 includes: a liquid crystal display panel 15 to display video; a projection optical system 2 that projects the video displayed in the liquid crystal display panel 15; a plurality of LED light sources 11 to output the illumination light to illuminate the liquid crystal display panel 15; a collimator lens 12 that converts the illumination light from the LED light sources 11 into parallel light; a dispersion element (dispersion sheet) 13 that disperses the illumination light from the collimator lens 12; and a field lens 14 that makes the illumination light from the dispersion element 13 incident into the liquid crystal display panel 15. The field lens 14 makes an optical axis 1a of the illumination light to enter the liquid crystal display panel 15 coincide with an optical axis 2a of the incident light that enters the projection optical system 2. An emission surface 13a of the dispersion element 13 is disposed at the position conjugating with the surface of an eye-box 3.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a head-up display device using a liquid crystal display panel.

  In recent years, an in-vehicle head-up display device using a liquid crystal display panel has been developed. The head-up display device displays information such as vehicle speed or car navigation information as a virtual image superimposed on the foreground of the vehicle in the direction of the driver's line of sight. Therefore, the driver who is gazing in front of the vehicle can visually recognize the information with a small amount of line-of-sight movement. A range (area) in which the driver can visually recognize information is referred to as an eye box.

  In general, since the head-up display device needs to be stored in a narrow space in the vehicle, it is required to reduce the size of the entire device.

  The head-up display device needs to ensure visibility even when the scenery outside the vehicle is bright, such as in fine weather. In addition, it is necessary for the driver to visually recognize important information (such as the vehicle speed) related to vehicle travel regardless of the position of the driver's eyes. Therefore, it is required to increase the brightness of the display image, improve the uniformity of the brightness distribution, and improve the uniformity of the illuminance distribution of the image light reaching the eye box.

  In order to increase the brightness of the display pixels, it is necessary to suppress the amount of light that protrudes from the eye box out of light (image light) emitted from the liquid crystal display panel. In addition, it is necessary to make the optical axis of incident light incident on a projection optical system that projects image light coincide with the optical axis of illumination light that illuminates the liquid crystal display panel.

  In order to make the luminance distribution of the display image uniform, it is necessary to illuminate the transmissive liquid crystal display panel from the back side (opposite the driver) with an LED light source. At this time, in order to make the illuminance distribution in the surface of the liquid crystal display panel uniform and obtain a desired luminance, it is common to use a plurality of LED light sources. However, when a plurality of LED light sources are used, an area where the illumination light emitted from adjacent LED light sources overlaps and an area where the illumination light overlaps little occurs on the display surface of the liquid crystal display panel. May decrease and uneven brightness may occur.

  In order to suppress uneven brightness, Patent Document 1 illuminates a liquid crystal display panel using an illumination optical system having a plurality of LED light sources, a collimator lens, a biconvex lens array, and a pair of field lenses. A configuration is disclosed. The pair of field lenses make the incident surface of the lens array and the display surface of the liquid crystal display panel conjugate to each other, thereby uniformly illuminating the liquid crystal display panel and suppressing luminance unevenness.

JP 2012-203176 A (see paragraphs 0028-0030 and FIG. 3)

  However, in the above technique, an expensive biconvex lens array is used, so that the manufacturing cost increases, and a pair of field lenses is used, so that the number of optical elements increases. Further, in the above technique, since the uniformity of the luminance distribution and the light use efficiency greatly depend on the parallelism (collimating property) of the incident light to the lens array, high dimensional accuracy and positioning accuracy of the optical component are required.

  Further, due to the nature of the lens array, the effect of increasing the uniformity of illumination light on the liquid crystal display panel increases as the number of lens elements included in the lens array increases, and the effect decreases as the number of lens elements decreases. The number of lens elements in the lens array is uniquely determined by the distance (that is, optical magnification) between the liquid crystal display panel and the exit surface of the lens array, and the longer the distance, the larger the number of lens elements. Therefore, in order to improve the uniformity of illumination light (that is, increase the number of lens elements), it is necessary to increase the distance between the liquid crystal display panel and the exit surface of the lens array, resulting in an increase in the size of the illumination optical system. .

  The present invention has been made to solve the above-described problems, and achieves higher brightness of display images and improved brightness uniformity without increasing manufacturing costs and increasing the size of the apparatus. With the goal.

  In order to solve the above-described problems, a head-up display device according to the present invention includes a liquid crystal display panel that displays an image, a projection optical system that projects an image displayed on the liquid crystal display panel, and an illumination device for illuminating the liquid crystal display panel. A plurality of LED light sources that emit illumination light, a collimator lens that converts illumination light from the plurality of LED light sources into parallel light, a diffusion element that diffuses illumination light from the collimator lens, and liquid crystal that emits illumination light from the diffusion element A field lens that is incident on the display panel and has a field lens that matches the optical axis of illumination light incident on the liquid crystal display panel with the optical axis of incident light incident on the projection optical system. The exit surface of the diffusing element is disposed at a position conjugate with the surface of the eye box.

  According to the present invention, it is possible to increase the luminance of a display image and improve the luminance uniformity without increasing the manufacturing cost and enlarging the apparatus.

It is a figure which shows the structure of the head-up display system containing the head-up display apparatus of Embodiment 1 of this invention. FIG. 3 is a schematic diagram illustrating a usage example of the head-up display device according to the first embodiment. FIG. 6 is a schematic diagram for explaining the action of a field lens in the head-up display device according to the first embodiment. It is a figure which shows the arrangement | positioning in the YZ plane of the component of the head-up display apparatus of Embodiment 1, and a chief ray. 6 is a schematic diagram for explaining a light emission state from a liquid crystal display panel in the head-up display device of Embodiment 1. FIG. It is a figure which shows arrangement | positioning in the XZ plane of the component of the head-up display apparatus of Embodiment 1, and a chief ray. It is a figure which shows the arrangement | positioning in the YZ plane of the component of the head-up display apparatus of Embodiment 1, and a side beam. It is a figure which shows the structure of the head-up display system containing the head-up display apparatus of the modification of Embodiment 1. FIG. It is a figure which shows the structure of the head up display system containing the head up display apparatus of Embodiment 2 of this invention.

Embodiment 1 FIG.
<Configuration of head-up display device>
FIG. 1 is a diagram showing a configuration of a head-up display system including a head-up display device 10 according to the first embodiment of the present invention. The head-up display system shown in FIG. 1 is mounted on a vehicle such as an automobile, for example. The head-up display system includes an illumination optical system 1, a liquid crystal display panel 15, a projection optical system 2, and an eye box 3. Among these, the head-up display device 10 is configured by the illumination optical system 1, the liquid crystal display panel 15, and the projection optical system 2.

  FIG. 2 is a schematic diagram for explaining an example of use of the head-up display device 10 according to the first embodiment. The illumination optical system 1 and the liquid crystal display panel 15 are arranged on a dashboard of a vehicle 8 such as an automobile. The projection optical system 2 is disposed at a position where it can be viewed from the driver 6, for example, in front of a windshield (front window) 81 of the vehicle 8. The arrangement of the illumination optical system 1 and the projection optical system 2 is not limited to the example described above.

  The driver 6 can visually recognize the image (virtual image) 7 displayed on the liquid crystal display panel 15 so as to overlap the foreground of the windshield 81 by the virtual image display action of the projection optical system 2. That is, the driver 6 who has visually recognized the foreground can visually recognize the video 7 with a small viewpoint movement. The eye box 3 is set at the position of the eye 61 of the driver 6 as an area where the driver 6 (viewer) can visually recognize information. The position of the eye box 3 is set to the position of the eye 61 of the driver 6 in the vehicle 8.

  In FIG. 1, the normal direction of the display surface of the liquid crystal display panel 15 is the Z direction. Regarding the Z direction, the direction from the liquid crystal display panel 15 toward the projection optical system 2 is the + Z direction, and the opposite direction is the -Z direction. The horizontal direction in the display surface of the liquid crystal display panel 15 is defined as the X direction, and the direction perpendicular to the X direction is defined as the Y direction. In the other drawings, the X direction, the Y direction, and the Z direction indicate the same directions as in FIG. In FIG. 1, the direction of the display surface of the liquid crystal display panel 15 is indicated by a one-dot chain line.

  With reference to FIG. 1, each component of the head-up display apparatus 10 is demonstrated. The illumination optical system 1 includes an LED (light emitting diode) light source 11, a collimator lens 12, a diffusion sheet 13, and a field lens 14.

  The LED light source 11 is a light source of the head-up display device 10. Here, a plurality of (for example, three) LED light sources 11 are arranged in the X direction (see FIG. 6 described later). For example, three LED light sources 11 are arranged in the X direction and one in the Y direction (that is, in one row and three columns). However, the number and arrangement of the LED light sources 11 are not limited to this example, and are necessary for obtaining a desired luminance on the aspect ratio of the effective area of the liquid crystal display panel 15 and the display surface of the liquid crystal display panel 15. It depends on the total amount of light.

  The direction of the outgoing optical axis 11a of the LED light source 11 (that is, the normal passing through the center of the outgoing surface of the LED light source 11) is the Z direction. The collimator lens 12, the diffusion sheet 13, and the field lens 14 are arranged in the direction of the emission optical axis 11 a of the LED light source 11.

  The collimator lens 12 is disposed on the emission side of the LED light source 11. The collimator lens 12 converts divergent light (illumination light) emitted from the LED light source 11 into parallel light and emits it. “Parallel light” refers to light traveling in parallel, but is not limited to strict parallel light, and includes light that can be regarded as substantially parallel light.

  The number of collimator lenses 12 is the same as that of the LED light source 11 (for example, three). The collimator lens 12 is installed so that the optical axis of the collimator lens 12 coincides with the outgoing optical axis 11 a of the LED light source 11.

  In order to reduce the manufacturing cost, it is desirable that a plurality of collimator lenses 12 are integrally formed, but the invention is not limited to this. For example, a plurality of individually formed collimator lenses 12 may be integrally held.

  The diffusion sheet 13 (diffusion element) is disposed on the emission side of the collimator lens 12. Light (illumination light) emitted from the collimator lens 12 enters the diffusion sheet 13. The diffusion sheet 13 diffuses the incident illumination light and emits it from the emission surface 13a at an angle that matches the size of the eye box 3. The diffusion sheet 13 is made of, for example, acrylic resin, but is not limited to this, and may be, for example, polycarbonate resin or glass.

  Here, one diffusion sheet 13 is used, but the number of diffusion sheets 13 is not limited to one. For example, the number of diffusion sheets 13 can be increased or decreased in accordance with desired diffusion characteristics, such as using a plurality of diffusion sheets 13 with less diffusion. The diffusion sheet 13 is not limited to a sheet shape, and may be a plate shape, for example.

  Various configurations can be adopted as the configuration in which the diffusion sheet 13 diffuses light. For example, light may be diffused by making the surface of the diffusion sheet 13 (the exit surface 13 a) rough, or light diffusion particles may be blended inside the diffusion sheet 13. Alternatively, a hologram may be formed on the surface of the diffusion sheet 13 like a holographic diffusion sheet, or an optical shape such as a microlens may be provided.

  The field lens 14 is disposed on the emission side of the diffusion sheet 13. Light having a desired diffusion characteristic (illumination light) emitted from the diffusion sheet 13 is incident on the field lens 14. The field lens 14 does not contribute to the image forming action of forming the image formed on the liquid crystal display panel 15 as a virtual image, but makes the diffusion sheet 13 and the eye box 3 conjugate (that is, image forming relationship). A light beam that functions and is directed to the outside of the object to be illuminated (the liquid crystal display panel 15) is refracted inward to enter the liquid crystal display panel 15.

  Further, the field lens 14 emits light in an emission direction corresponding to each position in the surface of the liquid crystal display panel 15 in accordance with the design of the projection optical system 2, and thereby the optical axis of the incident light of the projection optical system 2. 2a and the optical axis 1a of the illumination light emitted from the illumination optical system 1 (that is, the illumination light that illuminates the liquid crystal display panel 15).

  FIG. 3 is a schematic diagram for explaining the role of the field lens 14. The optical axis 2a of the incident light of the projection optical system 2 is inclined with respect to the optical axis of the incident light of the field lens 14 (parallel to the outgoing optical axis 11a of the LED light source 11). Therefore, the field lens 14 is arranged, for example, eccentrically with respect to the optical axis of the incident light, so that the optical axis of the outgoing light of the field lens 14 coincides with the optical axis 2 a of the incident light of the projection optical system 2. The optical axis of the emitted light from the field lens 14 is the optical axis 1 a of the illumination light that the illumination optical system 1 illuminates the liquid crystal display panel 15.

  In FIG. 3, the tilt of the optical axis 1 a of the illumination light and the outgoing optical axis 11 a of the LED light source 11 is exaggerated for easy understanding of the role of the field lens 14. The field lens 14 has, for example, a biconvex shape, and the power of the incident surface is larger than the power of the output surface, but is not limited to such a shape.

  Returning to FIG. 1, the liquid crystal display panel 15 is an object to be illuminated illuminated by illumination light of the illumination optical system 1 (LED light source 11, collimator lens 12, diffusion sheet 13, and field lens 14). The liquid crystal display panel 15 is a transmissive type, and illumination light emitted from the field lens 14 enters and emits light (video light) according to an input signal. The liquid crystal display panel 15 has an effective area whose length in the X direction is longer (that is, horizontally long) than the length in the Y direction, and displays video information. The aspect ratio of the effective area is, for example, 16: 9, 4: 3, 2: 1, or the like.

  The projection optical system 2 displays the image light from the liquid crystal display panel 15 as a virtual image (image 7 in FIG. 2) on the eyes 61 of the driver 6 (FIG. 2). The optical axis 2a of the incident light of the projection optical system 2 coincides with the optical axis 1a of the illumination light that the illumination optical system 1 illuminates the liquid crystal display panel 15 as described above. Further, the optical axis 2 b of the emitted light from the projection optical system 2 is directed toward the center 31 of the eye box 3.

  The projection optical system 2 includes a combiner 21 for displaying a virtual image. Here, the combiner 21 is composed of one concave mirror. However, it is not limited to such a configuration, and a plurality of concave mirrors may be used, or a plane mirror may be used in combination. The combiner 21 is made of a resin such as acrylic or polycarbonate, for example. A surface treatment for increasing the reflectance of the image light from the liquid crystal display panel 15 may be performed on the surface of the combiner 21.

  The combiner 21 also has a function of transmitting light like a half mirror. The driver 6 can visually recognize the image displayed on the liquid crystal display panel 15 as if it is floating on the foreground of the windshield 81 (FIG. 2) by the virtual image display action and the light transmission action of the combiner 21.

<Arrangement of diffusion sheet>
Next, the arrangement of the diffusion sheet 13 in the illumination optical system 1 will be described. FIG. 4 is a diagram showing the arrangement and principal rays in the YZ plane of the components of the head-up display device 10 of the first embodiment. In this specification, the “principal ray” refers to a ray that passes through each point in the plane of the liquid crystal display panel 15 and is collected at the center 31 of the eye box 3. In FIG. 4, the principal ray emitted from the projection optical system 2 is denoted by reference numeral 41, and the principal ray in the illumination optical system 1 is denoted by reference numeral 51. The chief ray is important in considering the uniformity of the luminance distribution in the surface of the liquid crystal display panel 15.

  Although the principal ray 41 of the projection optical system 2 and the principal ray 51 in the illumination optical system 1 are shown perpendicular to the display surface (XY plane) of the liquid crystal display panel 15 in FIG. It inclines with respect to the display surface of the display panel 15 (refer FIG. 3).

  As shown in FIG. 4, the principal ray 41 condensed at the center 31 of the eye box 3 is emitted from the center of the diffusion sheet 13 and passes through each point in the plane of the liquid crystal display panel 15 via the field lens 14. Light rays. Although the light rays that have passed through the field lens 14 are shown as parallel light in FIG. 4, they are actually emitted from the liquid crystal display panel 15 at an angle as indicated by reference numeral 43 in FIG.

  In the present embodiment, the YZ plane shown in FIG. 4 is set by setting the amount of eccentricity (see FIG. 3) and curvature of the field lens 14 and the optical characteristics of the projection optical system 2 (for example, the curvature of the concave mirror as the combiner 21). The diffusion sheet 13 is disposed at a position conjugate with the eye box 3. More specifically, the exit surface 13 a of the diffusion sheet 13 is disposed at a position conjugate with the surface of the eye box 3.

  The “conjugate position” includes not only a strictly conjugate position but also a position that can be regarded as a substantially conjugate position.

  In this way, by disposing the diffusion sheet 13 at a position conjugate with the eye box 3 in the YZ plane, each point in the plane of the liquid crystal display panel 15 is viewed by the driver 6 from the center 31 of the eye box 3. Is visually recognized with uniform brightness. That is, the in-plane luminance distribution of the liquid crystal display panel 15 can be made uniform.

  FIG. 6 is a diagram showing the arrangement and principal rays in the XZ plane of the components of the head-up display device 10 of the first embodiment. In the XZ plane shown in FIG. 6, a plurality of LED light sources 11 are arranged in the X direction. Therefore, even if a position conjugate with the eye box 3 is secured by setting the optical characteristics of the field lens 14 and the projection optical system 2 and the diffusion sheet 13 is arranged at that position, the light emitted from the plurality of LED light sources 11 It is difficult to capture all of the light, resulting in a decrease in light utilization efficiency. Therefore, in the present embodiment, the diffusion sheet 13 is disposed at a position conjugate with the eye box 3 on the YZ plane (FIG. 4).

  Next, the uniformity of the illuminance distribution in the surface of the eye box 3 will be described. FIG. 7 is a diagram showing the arrangement and side rays in the YZ plane of the components of the head-up display device 10 of the first embodiment. In this specification, the “side light beam” refers to a light beam that passes through the center of the liquid crystal display panel 15 and is incident on each point in the plane of the eye box 3. In FIG. 7, the side light emitted from the projection optical system 2 is indicated by reference numeral 42, and the side light in the illumination optical system 1 is indicated by reference numeral 52. The side rays are important in considering the luminance at the center of the liquid crystal display panel 15 viewed from each point in the plane of the eye box 3 (that is, the illuminance distribution in the plane of the eye box 3).

  Side rays 42 passing through the center of the liquid crystal display panel 15 and passing through each point in the plane of the eye box 3 are emitted from the center of the LED light source 11 and become parallel light by the collimator lens 12 as shown in FIG. 14, each light beam included in the light condensed at the center of the liquid crystal display panel 15. Since the LED light source 11 emits light with a uniform light amount within the range of the emission angle, it can be considered that the light amount distribution in the cross section of the parallel light emitted from the collimator lens 12 is uniform.

  As shown in FIG. 7, parallel light emitted from the collimator lens 12 (that is, parallel light with a uniform light amount distribution) enters the diffusion sheet 13, and a part of the light diffused by the diffusion sheet 13, for example, parallel light. Light close to light is condensed at each point, for example, at the center of the liquid crystal display panel 15, and each light ray included in this light reaches each point in the plane of the eye box 3. At this time, the light intensity distribution of the light transmitted through the diffusion sheet 13 with respect to the position on the diffusion sheet 13 and the angle of the diffusion light can be regarded as uniform. Therefore, the illuminance distribution in the surface of the eye box 3 (more specifically, the illuminance distribution of the image light reaching the eye box 3) is uniform. The uniformity of the illuminance distribution in the surface of the eye box 3 is mainly realized by the configuration of the diffusion sheet 13 and the field lens 14.

  In FIG. 7, the light transmitted through the collimator lens 12 is illustrated as being slightly collected, but the present invention is not limited to such an example. The condensing state of the light transmitted through the collimator lens 12 takes into account the distance between the LED light source 11 and the liquid crystal display panel 15 determined according to the package size or the like of the head-up display device 10, and the collimator lens 12 and the field lens 14. It is adjusted by the curvature and refractive index (power).

<Effect of Embodiment>
As described above, according to the first embodiment of the present invention, since the exit surface 13a of the diffusion sheet 13 of the illumination optical system 1 is disposed at a position conjugate with the surface of the eye box 3, the liquid crystal viewed from the eye box 3 is displayed. The uniformity of the luminance distribution in the surface of the display panel 15 can be improved.

  In particular, a plurality of LED light sources 11 are arranged in a line, and the emission surface 13a of the diffusion sheet 13 is arranged at a position conjugate with the surface of the eyebox 3 on the surface (YZ surface) orthogonal to the arrangement direction (X direction). The uniformity of the luminance distribution in the surface of the liquid crystal display panel 15 can be improved while taking in the light from the plurality of LED light sources 11 and improving the light utilization efficiency.

  In addition, the amount of light protruding from the eye box 3 is suppressed by the field lens 14, and the optical axis 2a of the incident light of the projection optical system 2 and the optical axis 1a of the illumination light are made coincident with each other. It is possible to increase the brightness of the liquid crystal display panel 15 as viewed.

  Further, for example, there is no need to provide a biconvex lens array and a pair of field lenses as disclosed in Patent Document 1, so that the manufacturing cost is not increased, and the illumination optical system 1 is increased in size. There is nothing.

  Further, the parallel light emitted from the collimator lens 12 enters the diffusion sheet 13 and is diffused, and a part of the diffused light (for example, light close to the parallel light) is each point (for example, the center) of the liquid crystal display panel 15. ), And each light ray included in the light reaches each point in the plane of the eye box 3, so that the uniformity of the illuminance distribution in the plane of the eye box 3 can be improved.

Modified example.
FIG. 8 is a diagram showing a head-up display system including a head-up display device 10A according to a modification of the first embodiment. In this modification, two diffusion sheets 18 and 19 are provided in place of the diffusion sheet 13 of the first embodiment for the purpose of reducing luminance unevenness.

  The diffusion sheet 18 is a lenticular lens sheet that diffuses incident light in one direction, and is disposed on the output side of the collimator lens 12 here. The diffusion sheet 19 is a general diffusion sheet that diffuses incident light in the same direction. Here, the diffusion sheet 19 is disposed between the field lens 14 and the liquid crystal display panel 15.

  In this modification, the exit surface of the diffusion sheet 18 (lenticular lens sheet) is disposed at a position conjugate with the surface of the eyebox 3 in the YZ plane.

  According to this modification, in addition to the effects described in the first embodiment, by providing the diffusion sheets 18 and 19, luminance unevenness caused by arranging the plurality of LED light sources 11 in the X direction is arranged. Can be reduced. That is, the uniformity of the luminance distribution in the surface of the liquid crystal display panel 15 viewed from the eye box 3 can be further improved.

Embodiment 2. FIG.
FIG. 9 is a diagram showing a head-up display system including the head-up display device 10B according to the second embodiment of the present invention. The head-up display device 10B of the second embodiment is different from the projection optical system 2 of the head-up display device 10 of the first embodiment in the configuration of the projection optical system 2B. Although the projection optical system 2 of the first embodiment is configured by the combiner 21 (FIG. 1), the projection optical system 2B of the second embodiment is configured by the concave mirror 22 and the windshield 23.

  The windshield 23 is the windshield (front window) 81 of the vehicle 8 shown in FIG. For example, the windshield 23 is configured by bonding glass and resin. However, it is not limited to such materials.

  For example, the concave mirror 22 is formed by forming a reflective surface on the surface of a base material made of resin or the like by a coating treatment of aluminum or the like, but is not limited to such a material. The concave mirror 22 does not need to transmit light unlike the combiner 21 of the first embodiment, and thus has a property of totally reflecting light. The quantity and shape of the concave mirror 22 are not limited to the above. For example, in addition to the concave mirror, a convex mirror or a plane mirror may be used, or a plurality of mirrors may be used.

  The concave mirror 22 magnifies and projects the image light of the liquid crystal display panel 15 toward the windshield 23, and the driver 6 (FIG. 2) visually recognizes the image (virtual image) in front of the windshield 23. That is, the windshield 23 functions as a combiner that superimposes the foreground and the video. As a result, the driver can view the video with a small amount of viewpoint movement.

  The illumination optical system 1 and the liquid crystal display panel 15 are configured in the same manner as in the first embodiment. That is, the exit surface 13a of the diffusion sheet 13 of the illumination optical system 1 is disposed at a conjugate position with respect to the surface of the eye box 3 in the YZ plane.

  According to the second embodiment of the present invention, even in the configuration using the concave mirror 22 and the windshield 23 as the projection optical system 2, the same effect as in the first embodiment can be achieved.

  Note that the diffusion sheets 18 and 19 (FIG. 8) described in the modification of the first embodiment can be applied to the illumination optical system 1 of the second embodiment.

  The present invention can be used for a head-up display device of a vehicle such as an automobile. Moreover, it can be used not only for automobiles but also for fields such as airplanes.

DESCRIPTION OF SYMBOLS 1 Illumination optical system, 1a Optical axis of illumination light, 10, 10A, 10B Head-up display device, 11 LED light source, 12 Collimator lens, 13 Diffusing sheet (diffusing element), 14 Field lens, 15 Liquid crystal display panel, 18 Diffusing sheet (First diffusing element), 19 diffusing sheet (second diffusing element), 2, 2B projection optical system, 2a optical axis of incident light of the projection optical system, 2b optical axis of outgoing light of the projection optical system, 21 combiner , 22 concave mirror, 23 windshield, 3 eyebox, 41 principal ray, 42 side ray, 51 principal ray, 52 side ray, 6 driver, 61 driver's eye, 7 virtual image, 8 vehicle, 81 windshield.

Claims (8)

A liquid crystal display panel for displaying images;
A projection optical system for projecting an image displayed on the liquid crystal display panel;
A plurality of LED light sources for emitting illumination light for illuminating the liquid crystal display panel;
A collimator lens that converts illumination light from the plurality of LED light sources into parallel light;
A diffusing element that diffuses illumination light from the collimator lens;
A field lens that makes illumination light from the diffusing element incident on the liquid crystal display panel, and the optical axis of the illumination light incident on the liquid crystal display panel coincides with the optical axis of the incident light incident on the projection optical system A field lens to be
The head-up display device characterized in that the exit surface of the diffusing element is arranged at a position conjugate with the surface of the eyebox. The plurality of LED light sources are arranged in one direction,
2. The head-up display according to claim 1, wherein an emission surface of the diffusing element is disposed at a position conjugate with a surface of the eye box in a plane orthogonal to an arrangement direction of the plurality of LED light sources. apparatus.   The head-up display device according to claim 2, wherein an arrangement direction of the plurality of LED light sources is a horizontal direction or a vertical direction.   Illumination light converted into parallel light by the collimator lens is incident on the diffusing element and diffused, and part of the diffused light is condensed at each point of the liquid crystal display panel, and the condensed light is converted into the condensed light. 4. The head-up display device according to claim 1, wherein each light ray included reaches each point in the plane of the eye box. 5. The diffusion element is a first diffusion element,
5. The head-up display device according to claim 1, further comprising a second diffusing element between the field lens and the liquid crystal display panel. 6.   The head-up display device according to claim 1, wherein the projection optical system includes a combiner.   The head-up display device according to claim 6, wherein the combiner is made of resin. The head-up display device according to any one of claims 1 to 5, wherein the projection optical system includes a windshield and a concave mirror.

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