JP7128448B2 - head-up display device - Google Patents

Description

The present invention relates to a head-up display device incorporating a Fresnel element and displaying a virtual image.

There is a demand to install a head-up display as a safe driving support system in industrial machinery such as forklifts and heavy machinery. In the existing system, the LCD is installed near the control panel where the operator's field of vision is not obstructed, and the information displayed on the LCD is checked. There is a problem that a large amount of line-of-sight movement and focal point movement are required, increasing the physical burden on the worker. By using a head-up display, workers can check information without having to move their line of sight or focus much during normal work, which reduces the physical burden on workers and allows necessary information to be displayed in real time. It is also possible to confirm.

A head-up display allows an operator to see a virtual image created by a display screen that functions as a concave mirror and a drawing device that displays information. An attempt to widen the FOV (viewing angle) of the virtual image increases the size and curvature of the display screen, increasing the presence of the display screen. In addition, in industrial machinery, from the viewpoint of worker safety (collision avoidance) and workability (ensure visibility), the space where display screens and drawing devices can be placed is limited. By using the screen, the safety and workability of the operator can be ensured, and the head-up display device can reduce the presence of the display screen. However, since the display screen has a Fresnel structure inside, when it is assumed that light from a high-intensity light source such as the sun is incident from various positions during outdoor use, there is a risk that the light from the light source will be reflected on the display screen. be.

As a head-up display, for example, it includes a light source unit that emits light that forms a display image, and an optical element that is arranged in the same direction as the tilt direction of the windshield, and the light that forms the display image is reflected by the optical element. Thus, it is known that the displayed image can be visually recognized as a virtual image (Patent Document 1). The optical element has a Fresnel structure half mirror in a flat plate, and the half mirror reflects the light from the light source. However, in the head-up display of Patent Document 1, the angle between the functional surface and the non-functional surface of the Fresnel structure of the optical element is 90° or less, and light from a high-brightness light source is prevented from entering from various positions. If assumed, the problem remains that the light from the high-intensity light source is reflected on the display screen.

WO2014/041689

SUMMARY OF THE INVENTION It is an object of the present invention to provide a head-up display device that reduces reflection of light from a high-brightness light source on a display screen.

A head-up display device for achieving the above object comprises a drawing device and a display screen for reflecting light from the drawing device, wherein the display screen has a Fresnel structure inside which has a functional surface and a non-functional surface. The functional surface and the non-functional surface are coated with a half-mirror coat, and the reference shape of the functional surface of the Fresnel structure is a curved surface. The following conditional expression is satisfied, where a is the angle formed by the functional surface and the non-functional surface is b.
180°-3・a<b<180°-0.5・a (1)
Here, the curved surface, which is the reference shape of the functional surface of the Fresnel structure portion, includes, for example, a part of a free curved surface or an axisymmetric aspherical surface.

According to the above head-up display, when the value b of conditional expression (1) exceeds the upper limit, the area of the functional surface becomes too small, resulting in reduction in brightness and resolution of the virtual image. On the other hand, when the value b of conditional expression (1) is smaller than the lower limit, it is not possible to limit the range in which the high-brightness light source is reflected on the display screen. By satisfying the above range for the value b of conditional expression (1), it is possible to ensure the safety and workability of the operator even if the FOV of the virtual image is wide, and the range in which the light from the high-intensity light source is reflected on the display screen is reduced. It can be confined to a specific position and reduce ghosting that occurs on the surface of the display screen.

According to a specific aspect of the present invention, in the above head-up display device, the shape serving as a reference for the functional surface of the Fresnel structure is a free curved surface. In this case, a high-magnification optical system is possible, and the FOV of the virtual image can be widened while maintaining high optical characteristics (resolution and image distortion when the position of the eye is shifted).

In another aspect of the invention, the display screen has a transmittance of 70% or greater. In this case, while the virtual image is displayed on the display screen, the external image can be sufficiently viewed, and the stability of the work can be maintained.

In still another aspect of the present invention, the Fresnel structure satisfies the following conditional expressions.
5°≦a≦25° (2)
By making the value a of conditional expression (2) equal to or higher than the lower limit, it is possible to avoid ghosts (virtual images due to surface reflection of the screen) occurring on the surface of the display screen. The optical characteristics of the virtual image can be improved by doing the following.

In still another aspect of the present invention, the Fresnel structure portion has an R-shaped portion at the corner, the width of the R-shaped portion is A, and the radius of curvature of the R-shaped portion is B, the following conditional expression: meet.
A≦10 μm (3)
5 μm≦B≦20 μm (4)
By satisfying the ranges of conditional expressions (3) and (4), it is possible to reduce the ghost caused by light from a high-intensity light source such as the sun entering the corners of the Fresnel structure during outdoor use.

In yet another aspect of the invention, the display screen is flat. Here, the flat plate is not limited to having a flat surface, and may have a curved surface. In this case, it becomes easier to bring the display screen closer to a flat windshield, and the display screen itself can be made inconspicuous.

In yet another aspect of the invention, the display screen is fixed to the windshield of the vehicle. In this case, the windshield functions as a support for the display screen, and the number of light shields arranged around the display screen can be reduced.

(A) is a side view showing a state in which the head-up display device of the first embodiment is mounted on a moving body, and (B) is a front view of the moving body. It is a conceptual side view explaining the structural example of a head-up display apparatus. (A) is a front view of a first Fresnel element as a display screen, (B) is an enlarged cross-sectional view of the first Fresnel element in (A) taken along line AA', and (C). and (D) are modifications of the cross-sectional structure of the Fresnel element shown in (B). (A) is a front view of a second Fresnel element as a display screen, and (B) is an enlarged cross-sectional view of the second Fresnel element in (A) taken along line A-A'. (A) is a side projection view of the virtual image projection optical system of Example 1, and (B) is a side projection view for explaining formation of a virtual image by the virtual image projection optical system of Example 1. FIG. FIG. 2 is a diagram for explaining an optical path in which a ray from the outside reaches an eyebox via a display screen in the virtual image projection optical system of Example 1; FIG. 10 is a diagram for explaining an optical path in which light rays from the outside world reach the eyebox via the display screen in the virtual image projection optical system of Comparative Example 1; FIG. 10 is a diagram for explaining optical paths in which light rays from the outside reach the eyebox via the display screen in the virtual image projection optical system of Comparative Example 2; (A) is a side projection view of the virtual image projection optical system of Example 2, and (B) is an xz plane projection view of the virtual image projection optical system of Example 2; (A) is a side projection view for explaining formation of a virtual image by the virtual image projection optical system of Example 2, and (B) is an xz plane projection view for explaining formation of a virtual image by the virtual image projection optical system of Example 2; is. FIG. 10 is a diagram illustrating an optical path in which a ray from the outside reaches an eyebox via a display screen in the virtual image projection optical system of Example 2; It is a conceptual diagram explaining the display screen of the head-up display apparatus of 2nd Embodiment.

[First Embodiment]
A first embodiment of a head-up display device according to the present invention will be described below with reference to the drawings.

1(A) and 1(B) are a side view and a front view of a moving body on which the head-up display device of this embodiment is mounted. A head-up display (HUD: Head-Up Display) device 100 is mounted on a forklift, which is the moving body 2, and includes a first virtual image projection optical system 10A and a second virtual image projection optical system 10B. The first virtual image projection optical system 10A includes a first drawing unit 11 and a first display screen 21, and the second virtual image projection optical system 10B includes a second drawing unit 12 and a second display screen 22. FIG. The first and second virtual image projection optical systems 10A and 10B transmit image information displayed on drawing devices (described later) in the drawing units 11 and 12 to the driver (observer) DR via the display screens 21 and 22. A virtual image is displayed. Although the head-up display device 100 shown in FIG. 1 has two virtual image projection optical systems, they may be used alone.

The movable body 2 has a windshield 8 supported by the frame 2f while being sandwiched between the frames 2f on the front side, and has a roof portion 2t on the top. An operation unit 2d including a steering wheel and the like is arranged inside the lower portion of the windshield 8 to enable the driver DR to steer the moving body 2. As shown in FIG. The moving body 2 has a tiltable mast 3a and a fork 3b that is supported by the mast 3a and moves up and down as a forklift.

The first drawing unit 11 of the first virtual image projection optical system 10A is installed between the windshield 8 and the operation unit 2d and fixed to the operation unit 2d side, and is used to display images including driving-related information, danger signals, and the like. The display light HK1 corresponding to is emitted toward the first display screen 21 having translucency. A first display screen 21 is fixed directly to the windshield 8 . As a result, the windshield 8 functions as a support for the first display screen 21, and the number of light shields arranged around the first display screen 21 can be reduced. The first display screen 21 is also called a combiner and is a semi-transmissive plate-like Fresnel element or Fresnel mirror. This makes it easier to bring the first display screen 21 closer to the flat windshield 8 and makes the first display screen 21 itself inconspicuous. Note that the flat plate is not limited to having a flat surface, and may have a curved surface. The first display screen 21 or its active area has a rectangular outline and is oblong. That is, the first display screen 21 or its effective area has a larger size in the horizontal VX direction than in the vertical VY direction. The display light HK1 reflected at a predetermined angle of reflection by the first display screen 21 is guided to the eyes PU of the driver DR sitting in the driver's seat 6 .

The second drawing unit 12 of the second virtual image projection optical system 10B is installed in a depression on the boundary between the windshield 8 and the roof portion 2t and fixed to the roof portion 2t, and includes driving-related information, danger signals, and the like. The display light HK2 corresponding to the image is emitted toward the second display screen 22 having semi-transmissivity. The second display screen 22 is fixed to the windshield 8 using the support member 14 or the like. The second display screen 22, also called a combiner, is a semi-transparent plate-like Fresnel element or Fresnel mirror. The second display screen 22 or its active area has a rectangular outline and is oblong. That is, the second display screen 22 or its effective area has a larger size in the horizontal VX direction than in the vertical VY direction. The display light HK2 reflected at a predetermined angle of reflection by the second display screen 22 is guided to the pupils PU of the driver DR sitting in the driver's seat 6 .

As shown in FIG. 2, the display light HK1 reflected by the first display screen 21 of the first virtual image projection optical system 10A is guided to the eyebox EB corresponding to the pupil PU of the driver DR and its peripheral position. On the other hand, the driver DR can observe the external light transmitted through the first display screen 21, that is, the real image of the front scenery, the automobile, or the like. As a result, the driver DR sees a display image including driving-related information, danger signals, etc. formed by reflection of the display light HK1 on the first display screen 21, superimposed on the image of the outside world behind the first display screen 21. (Virtual image) IM1 can be observed. The first display screen 21 is arranged so as to be inclined clockwise when viewed from the horizontal direction on the -VX side with respect to the VX-VY plane, which is a vertical plane extending in the horizontal direction. That is, the first display screen 21 is inclined inwardly with respect to the vertical VZ direction so that the upper end side of the first display screen 21 approaches the eyebox EB. The first display screen 21 is arranged at a different position in the vertical VY direction with respect to the first drawing unit 11, but is arranged at almost the same position in the horizontal VX direction. The first display screen 21 has an overall positive power and functions like a concave mirror.

The display light HK2 reflected by the second display screen 22 of the second virtual image projection optical system 10B is guided to the eye box EB corresponding to the pupil PU of the driver DR and its peripheral position. On the other hand, the driver DR can observe the external light or the external image transmitted through the second display screen 22 . As a result, the driver DR sees a display image (virtual image) including driving-related information and the like formed by reflection of the display light HK2 on the second display screen 22, superimposed on the image of the outside world behind the second display screen 22. IM2 can be observed. The second display screen 22 is arranged to extend in a direction substantially parallel to the VX-VY plane, which is a vertical plane extending in the lateral direction. However, the second display screen 22 is arranged at different positions with respect to the second drawing unit 12 not only in the vertical VY direction but also in the horizontal VX direction. The secondary display screen 22 has an overall positive power and functions like a concave mirror.

In the above, the second display screen 22 is directly fixed to the windshield 8 at the upper end TE of the second display screen 22 and indirectly fixed to the windshield 8 via the support member 14 at the lower end BE. Here, since the second display screen 22 is arranged so as to extend in a direction substantially parallel to the VX-VY plane, which is a vertical plane extending in the vertical direction, the upper end portion TE of the second display screen 22 is not conspicuous. state. That is, the upper end portion TE of the second display screen 22 has a certain width, and when viewed from a direction inclined upward by a predetermined amount from a direction perpendicular thereto, it has a certain angular width and is conspicuous. becomes. However, if the second display screen 22 is arranged to extend in a direction substantially parallel to the VX-VY plane, which is a vertical plane, the upper end portion TE of the second display screen 22 has a constant width. However, it is relatively inconspicuous.

The first drawing unit 11 includes a drawing device 11a, an illumination section 11b, and a display driving circuit 11c. The drawing device 11a is a liquid crystal display (LCD) having a two-dimensional display surface 11s. The display light HK1 from the image formed on the display surface 11 s travels straight and enters the first display screen 21 . Here, the rendering device 11a, that is, the display surface 11s, has a larger size in the horizontal VX direction than in the vertical VY direction. The illumination unit 11b shown in FIG. 2 has an LED or other light source that emits light for illuminating the drawing device 11a from behind. The display drive circuit 11c causes the drawing device 11a to perform a display operation. In addition, since the display light HK1 from the drawing device 11a is efficiently incident on the first display screen 21, the angular distribution of the illumination light emitted from the illumination unit 11b can be adjusted, or the display light can be displayed on the exit surface of the drawing device 11a. An optical element can be arranged to adjust the angular distribution of the light HK1 on a pixel-by-pixel basis or as a whole. An example using an LCD as the drawing device 11a has been described above, but other types of display elements such as self-luminous display elements such as organic EL, reflective display elements such as DMD and LCOS, and projection lenses can be used. and a diffuser plate can be used. Also, as the drawing device 11a, a scanning image element using an optical system combining a MEMS and a diffusion plate may be used instead of the reflection type element as described above.

The second drawing unit 12 includes a drawing device 12a, an illumination section 12b, and a display driving circuit 12c. The drawing device 12a is a liquid crystal display (LCD) having a two-dimensional display surface 12s. The display light HK2 from the image formed on the display surface 12s travels straight and enters the second display screen 22. As shown in FIG. Here, the rendering device 12a, ie, the display surface 12s, has a larger size in the horizontal VX direction than in the vertical VY direction. The illumination unit 12b shown in FIG. 2 has a light source such as an LED that emits light for illuminating the drawing device 12a from behind. The display drive circuit 12c causes the drawing device 12a to perform a display operation. In addition, since the display light HK2 from the drawing device 12a is efficiently incident on the second display screen 22, the angular distribution of the illumination light emitted from the illumination unit 12b can be adjusted, or the display light can be displayed on the exit surface of the drawing device 12a. An optical element can be arranged to adjust the angular distribution of the light HK2 on a pixel-by-pixel basis or as a whole. As the drawing device 12a, as in the first drawing unit 11, an optical system combining a self-luminous display element or a reflective display element with a projection lens and a diffusion plate can be used. Also, as the drawing device 12a, a scanning image element using an optical system in which a MEMS and a diffusion plate are combined may be used.

As shown in FIGS. 3A and 3B, the first display screen 21 is a Fresnel element (Fresnel mirror) 50 . The Fresnel element 50 has a Fresnel structure portion 51 in which arc-shaped jagged protrusions are repeatedly formed in one direction at a substantially predetermined pitch P1. The Fresnel structure 51 has an off-axis or eccentric pattern. Specifically, the illustrated Fresnel structure portion 51 is arranged so that the normal lines of the individual arcs forming the ring zone as a whole are directed substantially downward. The Fresnel structure portion 51 has an arcuate optical surface 51a and a flat stepped surface 51b. The optical surface 51a corresponds to a functional surface, and the step surface 51b corresponds to a non-functional surface. A functional surface is, for example, a surface to which a predetermined function representing a curved surface is given, and other surfaces are non-functional surfaces. The optical surface 51a is formed based on a concave free-form curved surface that serves as a reference. That is, the height of the free-form surface from the optical origin is referred to and divided into a plurality of band-like regions, which are distributed to a plurality of optical surfaces 51a. By using a free-form surface as the reference shape of the optical surface 51a, a high-magnification optical system becomes possible, and the FOV of the virtual image can be obtained while maintaining high optical characteristics (resolution and image distortion when the position of the eyes is shifted). can be widened. For the Fresnel structure 51, for example, the height of the Fresnel structure 51 is set to be the same to determine the pitch P1 of the Fresnel structure 51 according to the free curved surface, or the pitch P1 of the Fresnel structure 51 is set to be the same to determine the pitch P1 of the Fresnel structure 51. can determine the height of Further, the height of the Fresnel structure portion 51 (the length of the step surface 51b in the thickness direction of the first display screen 21) is preferably 100 μm or less.

As shown in FIGS. 4A and 4B, the second display screen 22 is a Fresnel element (Fresnel mirror) 150 . The Fresnel element 150 has a Fresnel structure portion 151 in which arc-shaped jagged projections are repeatedly formed in one direction at a substantially predetermined pitch P2. The Fresnel structure 151 has an off-axis or eccentric pattern. Specifically, the illustrated Fresnel structure portion 151 is arranged so that the normal lines of the individual arcs forming the ring zone as a whole are oriented in the upper right direction. The Fresnel structure portion 151 has an arcuate optical surface 51a and a flat stepped surface 51b. As with the first display screen 21, the optical surface 51a corresponds to the functional surface, and the stepped surface 51b corresponds to the non-functional surface. The pitch P2 of the Fresnel structure portion 151 can be changed depending on the location, for example, but can also be constant regardless of the location. Further, the height of the Fresnel structure portion 151 (the length of the step surface 51b in the thickness direction of the second display screen 22) is preferably 100 μm or less.

As shown in FIGS. 3(B) and 4(B), the Fresnel elements 50 and 150 are composed of two substrates 53 . The Fresnel structures 51 and 151 are provided on one surface of each base material 53 and face each other. The Fresnel element 50 has a half mirror 52 made of a half mirror coat layer as a Fresnel structure portion 51 . That is, in the Fresnel structure portion 51, the optical surface 51a (functional surface) and the stepped surface 51b (non-functional surface) are coated with a half-mirror coat. The base material 53 is made of resin or the like, and the half mirror 52 is made of metal or a dielectric multilayer film. A UV curable resin or the like is used as the resin material of the base material 53 . The half mirror 52 preferably has a reflectance of about 30% and a transmittance of about 70%, and more preferably has a reflectance of about 10% and a transmittance of about 90%. By setting the transmittance to 70% or more, the virtual image can be displayed through the first and second display screens 21 and 22, and the external image can be sufficiently viewed, thereby maintaining work stability. can do. As shown in FIG. 3C, the substrate 153 that does not have the half mirror 52 may be a plane plate. It is filled with a medium 54 having the same refractive index (the reflectance at the boundary is 0.1% or less for light with a wavelength of 530 nm), specifically a UV curable resin or the like. As a result, the half mirror 52 shown in FIG. 3C is sandwiched between a pair of base materials 53 and 153 having substantially the same refractive index. As a result, not only the virtual image can be visually recognized, but also the external light transmitted through the Fresnel elements 50 and 150, that is, the real image of the front scenery, the automobile, etc. can be visually recognized as a transmitted image without distortion. Also, the surfaces of the Fresnel elements 50 and 150 may be coated with an antireflection coating. The antireflection coat is formed of a dielectric multilayer film and may include a hard coat layer as a base.

Further, as shown in FIG. 3D, a PET sheet 55 may be provided on the surfaces of the Fresnel elements 50 and 150, and the surface of the PET sheet 55 may be coated with an antireflection coating. An acrylic sheet, a PC sheet, a COP sheet, or the like may be used instead of the PET sheet 55 .

The optical surface 51a, which is the functional surface of the Fresnel structure portions 51 and 151, is a free-form surface, and is contained within a flat plate surface having a predetermined thickness by the stepped surface 51b, which is a non-functional surface, except for the stepped surface 51b. In this case, it consists of a continuously extending curved surface, and becomes a part of the free curved surface concaved toward the eyebox EB as a whole.

As shown in FIGS. 3B and 4B, in the Fresnel structure portions 51 and 151, the inclination of the optical surface 51a (functional surface) with respect to the first and second display screen surfaces SA1 is a, and the optical surface 51a and the step surface 51b (non-functional surface), the following conditional expression is satisfied.
180°-3・a<b<180°-0.5・a (1)
Here, the inclination a of the optical surface 51a is the smaller angle of 90° or less with respect to the first and second display screen surfaces SA1.

If the value b of conditional expression (1) exceeds the upper limit, the area of the optical surface 51a (functional surface) becomes too small, resulting in reduced brightness and resolution of the virtual image. On the other hand, when the value b of conditional expression (1) is smaller than the lower limit, the range in which the high-brightness light source is reflected on the first and second display screens 21 and 22 cannot be limited, although the details will be described later.

Moreover, the Fresnel structure portions 51 and 151 satisfy the following conditional expressions.
5°≦a≦25° (2)
By setting the value a of conditional expression (2) to be equal to or greater than the lower limit value, ghosts (virtual images due to surface reflections of the first and second display screens 21 and 22) generated on the first and second display screen surfaces SA1 are avoided. By setting the value a of conditional expression (2) to be equal to or less than the upper limit, the optical characteristics of the virtual image can be improved.

As shown in FIG. 2, the display control device 18 outputs image signals and control signals to the first and second virtual image projection optical systems 10A and 10B, and individually operates the first and second virtual image projection optical systems 10A and 10B. By operating, the display images IM1 and IM2 are displayed behind the first and second display screens 21 and 22, respectively.

In the above description, the head-up display device 100 includes two display optical systems, that is, the first and second virtual image projection optical systems 10A and 10B. You can also include only

According to the head-up display (HUD) device 100 described above, the angle b formed by the optical surface 51a that is the functional surface of the Fresnel structure portion 51 and the stepped surface 51b that is the non-functional surface is within the range of the conditional expression (1). By satisfying, even if the FOV of the virtual image is wide, the safety and workability of the driver (operator) DR can be ensured, and the range in which the light from the high-brightness light source is reflected on the first display screen 21 is set to a specific position limits and reduces ghosting that occurs on the surface of the first display screen 21 .

〔Example〕
Specific examples of the head-up display device 100 according to the present invention will be described below. In the data of the examples shown below, Si (i=0, 1, 2, 3, . 0th surface). The first surface S1 following the 0th surface S0 corresponding to the virtual image surface is a virtual surface, and the third surface S3 corresponds to the pupil PU.

The arrangement of the surfaces Si forming the virtual image projection optical systems 10A and 10B is specified by surface vertex coordinates (x, y, z) and rotation angles (ADE, BDE, CDE). The surface vertex coordinates of each surface Si are local orthogonal coordinate system (X, Y, Z) are represented by coordinates (x, y, z) of the origin (unit: mm). Here, the global coordinate axis x is set parallel or substantially parallel to the VX axis shown in FIG. 2, the global coordinate axis y is set parallel or substantially parallel to the VY axis shown in FIG. , are set parallel or substantially parallel to the VZ axis shown in FIG. In addition, the inclination of each surface Si is ADE or rotation angle (α rotation) about the X axis, BDE or rotation angle (β rotation) about the Y axis, and CDE or rotation about the Z axis, with the vertex of the surface as the center. It is represented by an angle (γ rotation). The unit of the rotation angle is °. The positive direction of the rotation angle of shaft rotation or γ rotation. Also, the global Cartesian coordinate system (x, y, z) is an absolute coordinate system that matches the local Cartesian coordinate system (X, Y, Z) of the pupil PU or the pupil plane (S3). That is, the arrangement data of each plane Si is represented by a global coordinate system with the center of the pupil plane as the origin. Note that, on the pupil plane (S3), the direction from the combiner 20 toward the pupil PU is the +Z direction or +z direction, the upward direction with respect to the pupil PU is the +Y direction or +y direction, and the right direction with respect to the pupil PU is +X direction or +x direction.

ただし、
ｃ ：頂点曲率（ｃ＝１／Ｒ）
ｋ ：円錐定数
Ｃｊ：Ｘ^ｍＹ^ｎの係数
Ｒ ：Ｙ曲率半径 In each embodiment, the half mirror 52 in the first and second display screens 21 and 22 is a free-form surface. The height in the direction perpendicular to the axis is represented by X and Y, and is represented by the following "Equation 1".
[Number 1]

however,
c: vertex curvature (c=1/R)
k: Conic constant Cj: X ^m Y ⁿ coefficient R: Y radius of curvature

[Example 1]
The optical system of Example 1 will be described below. The optical system of Example 1 corresponds to the first virtual image projection optical system 10A. Basic specifications of the virtual image projection optical system of Example 1 are shown in Table 1 below.
[Table 1]

The data of the optical surfaces, etc. of Example 1 are shown in Table 2 below.
[Table 2]

Table 3 below shows the surface data of the half mirror portion of Example 1. The half mirror portion of Example 1 corresponds to the half mirror 52 of the first display screen 21 . "*" in the table represents a product, and "^" represents a power element (the same applies to subsequent examples).
[Table 3]

FIG. 5A shows a side projection view (yz plane projection view) of the first virtual image projection optical system of Example 1. FIG. FIG. 5B is a side projection view illustrating projection of a virtual image by the first virtual image projection optical system of Example 1. FIG.

6A and 6B are diagrams for explaining optical paths in which light rays from the outside reach the eyebox EB via the first display screen 21 in the first virtual image projection optical system of Example 1. FIG. The state of light rays shown in the lower part of FIG. 6 is obtained by tracing the light incident on the eyebox EB with respect to the light rays L0 and the light rays L1 that are transmitted or reflected by the first display screen 21 of the pattern illustrated in the upper part of FIG. (The same applies to other examples and comparative examples). In FIG. 6, the light ray L0 indicates the light ray closest to the horizontal direction among the ghost lights, and partially shares the optical path of the light ray L1. In this embodiment, the inclination a of the optical surface 51a (functional surface) with respect to the first display screen surface SA1 is 7°, and the angle b between the optical surface 51a and the stepped surface 51b (non-functional surface) is 162°. which satisfies the conditional expressions (1) and (2).

As shown in FIG. 6, a light ray L0 and a light ray L1 incident on the eyebox EB from the outside world (specifically, the area AR1 in front of the moving body 2) are reflected by the Fresnel structure provided on the first display screen 21. 51 to the range BR1 shown in FIG. As a result, the range in which the light from the high-brightness light source or the like is reflected on the first display screen 21 is limited, and as a result, the ghost caused by the high-brightness light source or the like is reduced.

[Comparative Example 1]
7A and 7B are diagrams for explaining optical paths in which light rays from the outside world reach the eyebox EB via the first display screen 121 in the virtual image projection optical system of Comparative Example 1. FIG. In this comparative example, the inclination a of the optical surface 51a (functional surface) with respect to the display screen surface SA1 is 7°, and the angle b between the optical surface 51a and the stepped surface 51b (non-functional surface) is 83°. , is out of the range of conditional expression (1).

As shown in FIG. 7, light rays L1, L2, L3, and L4 incident on the eyebox EB from the outside world (specifically, the area AR1 in front of the moving body 2 and the area AR2 behind the moving body 2) are Light is transmitted or reflected by the Fresnel structure portion 51 provided in the display screen 121 of Example 1, and light from a relatively wide area of the outside world (ranges BR3 and BR4 shown in FIG. 7) is reflected on the display screen 121. It causes a ghost caused by a bright light source or the like. In FIG. 7, the light ray L4 indicates the light ray closest to the horizontal direction among the ghost lights, and partially shares the optical path of the light ray L3.

[Comparative Example 2]
8A and 8B are diagrams for explaining optical paths in which light rays from the outside world reach the eyebox EB via the first display screen 221 in the virtual image projection optical system of Comparative Example 2. FIG. In this comparative example, the inclination a of the optical surface 51a (functional surface) with respect to the display screen surface SA1 is 7°, and the angle b between the optical surface 51a and the stepped surface 51b (non-functional surface) is 155°. , is out of the range of conditional expression (1).

As shown in FIG. 8, light rays L1, L2, L3, and L4 incident on the eyebox EB from the outside world (specifically, the area AR1 in front of the moving body 2 and the area AR2 behind the moving body 2) are Light transmitted or reflected by the Fresnel structure portion 51 provided in the display screen 221 of Example 2, and reflected on the display screen 221 from a relatively wide area (ranges BR3 and BR4 shown in FIG. 8) of the external world, is reflected on the display screen 221. It causes a ghost caused by a bright light source or the like. In FIG. 8, the light ray L4 indicates the light ray closest to the horizontal direction among the ghost lights, and partially shares the optical path of the light ray L3.

[Example 2]
The optical system of Example 2 will be described below. The optical system of Example 2 corresponds to the second virtual image projection optical system 10B. Basic specifications of the virtual image projection optical system of Example 2 are shown in Table 4 below.
[Table 4]

The data of the optical surfaces, etc. of Example 2 are shown in Table 5 below.
[Table 5]

Table 6 below shows the surface data of the half mirror portion of Example 2. The half mirror portion of Example 2 corresponds to the half mirror 52 of the second display screen 22 .
[Table 6]

9A shows a side projection view (yz plane projection view) of the virtual image projection optical system of Example 2, and FIG. 9B shows an xz plane projection view of the virtual image projection optical system of Example 2. .

FIG. 10(A) is a side projection view for explaining projection of a virtual image by the virtual image projection optical system of Example 2, corresponding to FIG. 9(A), and FIG. FIG. 9B is an xz-plane projection diagram for explaining projection of a virtual image by an optical system, and corresponds to FIG. 9B;

11A and 11B are diagrams for explaining optical paths in which light rays from the outside world reach the eyebox EB via the first display screen 22 in the second virtual image projection optical system of Example 2. FIG. In this embodiment, the inclination a of the optical surface 51a (functional surface) with respect to the second display screen surface SA1 is 20°, and the angle b between the optical surface 51a and the stepped surface 51b (non-functional surface) is 140°. which satisfies the conditional expressions (1) and (2).

As shown in FIG. 11, light rays L1 and L2 incident on the eyebox EB from the outside world (specifically, the area AR1 in front of the moving body 2 and the area AR2 behind the moving body 2) are projected onto the second display screen 22. are limited to ranges BR1 and BR2 shown in FIG. As a result, the range in which the light from the high-brightness light source or the like is reflected on the second display screen 22 is limited, and as a result, the ghost caused by the high-brightness light source or the like is reduced. In addition, since the second drawing unit 12 is arranged on the side of the area AR2, the light rays L2 entering the eyebox EB from the area AR2 are blocked by the second drawing unit 12, and the reflection of the external light is further reduced.

[Second embodiment]
A head-up display device according to the second embodiment will be described below. Note that the head-up display device of the second embodiment is a modification of the head-up display device of the first embodiment, and items that are not particularly described are the same as those of the first embodiment.

In this embodiment, as shown in FIG. 12A, the second Fresnel structure portion 151 of the second display screen 22 has rounded portions at the corners 51c. Note that the first Fresnel structure portion 51 of the first display screen 21 may also have corner portions. The second Fresnel structure portion 151 satisfies the following conditional expression, where A is the width of the R-shaped portion and B is the radius of curvature of the R-shaped portion.
A≦10 μm (3)
5 μm≦B≦20 μm (4)
Satisfying the ranges of conditional expressions (3) and (4) reduces the ghost that occurs when the light TK from a high-intensity light source such as the sun enters the corner 51c of the second Fresnel structure 151 during outdoor use. can do.

As shown in FIG. 12A, when the corner 51c of the second Fresnel structure portion 151 satisfies the conditional expressions (3) and (4), the radius of curvature B is small and the incident light enters the corner 51c whose range is narrow. The resulting light beams reach the driver DR in a greatly spread state. For the driver DR, the light from the corner 51c that satisfies the conditional expressions (3) and (4) is very weak, and almost no linear ghost can be recognized.

As shown in FIG. 12B, when the corner 51c of the second Fresnel structure portion 151 does not satisfy the conditional expressions (3) and (4), the corner 51c having a large curvature radius B and a wide range The incident luminous fluxes reach the driver DR while being spread over a relatively narrow range. For the driver DR, the light from the corner portion 51c that satisfies the conditional expressions (3) and (4) is relatively strong and visually recognized as a linear ghost.

Although the head-up display device as a specific embodiment has been described above, the head-up display device according to the present invention is not limited to the above. For example, the contours of the first and second display screens 21 and 22 are not limited to rectangular shapes, and can be of various shapes.

Further, in the above embodiment, the patterns of the Fresnel structures 51 and 151 can be appropriately changed according to the configurations of the first and second virtual image projection optical systems 10A and 10B.

Also, in the above embodiment, a plane mirror may be provided between the first drawing unit 11 and the first display screen 21 . A plane mirror may also be provided between the second drawing unit 12 and the second display screen 22 .

Further, in the above embodiment, the display screen may be attached to a predetermined position of the windshield 8 or may be embedded in the windshield 8 . Also, the display screen may be held by a jig, and the jig may be fixed to the forklift. Furthermore, the arrangement and tilting direction of the display screen can be changed as appropriate.

In the above embodiment, the reference shape of the optical surface 51a (functional surface) of the Fresnel structure 51 is a free curved surface, but it may be a curved surface including a part of an axially symmetrical aspherical surface.

Moreover, in the above-described embodiment, an example in which the head-up display device 100 is mounted on a forklift was given, but it may be mounted on another moving object such as a passenger car.

2... Moving body 8... Windshield 10A, 10B... Virtual image projection optical system 11, 12... Drawing unit 11a, 12a... Drawing device 18... Display control device 20... Combiner 21, 22, 121, 221 Display screen 50,150 Fresnel element 51,151 Fresnel structure portion 51a Optical surface 51b Stepped surface 51c Corner 52 Half mirror 53,153 Substrate 100 Head up Display device DR...Driver EB...Eye box HK1, HK2...Display light SA1...Display screen surface

Claims (6)

a drawing device;
a display screen that reflects light from the rendering device;
with
The display screen has inside a Fresnel structure portion having a plurality of sets of functional surfaces and non-functional surfaces, and the functional surface and the non-functional surface are coated with a half-mirror coat,
The functional surface of the Fresnel structure portion is a curved surface having a shape distributed by dividing a virtual curved surface given a predetermined function into a plurality of belt-like regions with reference to heights from the origin . ,
The Fresnel structure portion has the following conditional expression , where a is the inclination of the functional surface with respect to the surface of the display screen, and b is the angle between the functional surface and the non-functional surface.
180°-3・a<b<180°-0.5・a (1)
and
The Fresnel structure portion has an R-shaped portion at a corner,
When the width of the R-shaped portion is A and the curvature radius of the R-shaped portion is B, the following conditional expression
A≦10 μm (3)
5 μm≦B≦20 μm (4)
A head-up display device characterized by satisfying 2. The head-up display device according to claim 1, wherein the virtual curved surface that provides the functional surface of the Fresnel structure is a free curved surface. 3. The head-up display device according to claim 1, wherein the display screen has a transmittance of 70% or more. The head-up display device according to any one of claims 1 to 3, wherein the Fresnel structure satisfies the following conditional expression.
5°≦a≦25° (2) The head-up display device according to any one of claims 1 to 4 , wherein the display screen is a flat plate. The head-up display device according to any one of claims 1 to 5 , wherein the display screen is fixed to a windshield of a moving body.

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