Head-up display device

Abstract

The invention provides a head-up display device. One embodiment of the present invention is an HUD device that irradiates display light onto a windshield of a manned moving body and introduces the light reflected by the windshield into the eyes of an observer to form a virtual image in front of the eyes of the observer, the HUD device being provided with: an image emission unit (image formation unit, introduction optical system) that includes a display unit that forms an image; the image emitting part forms parallel light beams with different angles on each part of the image and emits the parallel light beams as display light; a light guide that emits a light beam of the display light emitted from the image emission unit so that the light beam is expanded while maintaining the parallelism of the light beam; and a correction lens disposed on an optical path between the light guide and the windshield, the correction lens having a curved surface shape that deflects the transmission direction of the light in accordance with the curved surface shape of the reflective surface of the windshield, such that the display light, in which the parallel light beam bundle has been expanded by the light guide, becomes parallel after being reflected by the windshield.

Description

Technical Field

[0001] The present invention relates to a head-up display (hereinafter sometimes referred to as "HUD") device. Background Art

[0002] HUD is a device used by an observer such as an operator of a manned mobile vehicle such as an aircraft or a car to visually confirm various information such as instrument information while looking at the outside scene in front.

[0003] Non-Patent Document 1 describes a HUD that causes a plurality of reflectors and a windshield to reflect display light having information of an image displayed on a small display inside a HUD casing to guide the display light to the eyes of an observer.

[0004] As the amount of information that is expected to be displayed by such a HUD increases, the display by the HUD is required to be larger. On the other hand, as the size of the optical system increases with the larger screen, there is a problem that the HUD housing cannot be accommodated in the configuration space inside the machine or the vehicle body. As one of the solutions, a method of using a flat optical component that can expand the light beam, i.e., a light guide, is proposed, as described in non-patent document 1.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: International Publication No. 2021 / 157044

[0008] Non-patent literature

[0009] Non-patent document 1: Tanaka and Arita, "Contribution to Miniaturization of HUD (Hud) Technology" 》, Shimadzu Review, Shimadzu Manufacturing Co., Ltd., Vol.79, No.3 / 4(2022), issued on March 20, 2023 Summary of the invention

[0010] Problem that the invention aims to solve

[0011] There are several types of light guides, but basically, the display light is guided to the inside of a flat substrate, the display light is reflected between the two surfaces of the substrate and propagates inside the substrate, and a part of the display light is taken out of the substrate by optical effects such as refraction, reflection, and diffraction. In the aircraft HUD described in Non-Patent Document 1, the display light whose light beam is expanded by the light guide arranged substantially horizontally reaches the eyes of the observer after being reflected by the combiner, which is arranged in front of the observer and tilted so that the upper part thereof tilts toward the front side (observer side).

[0012] With such an aircraft HUD, a virtual image generated by display light can be well formed in front of the eyes of the observer. On the other hand, in the automotive HUD, from the viewpoints of large screen and cost reduction, the following structure is desired: instead of using a dedicated combiner, the display light is reflected by the windshield of the car equipped with the HUD to guide the display light to the eyes of the observer. However, when such an automotive HUD adopts a virtual image optical system including a light guide member adopted in the above-mentioned aircraft HUD, there is a problem that the virtual image formed in front of the observer is greatly distorted or the position where the virtual image is observed is greatly offset according to the position of the observer's viewpoint, thereby reducing visibility.

[0013] The present invention is made to solve such problems, and its main object is to provide a head-up display device that can reduce distortion or positional shift of HUD display caused by differences in the positions of the observer's viewpoints, thereby providing the observer with a good display image.

[0014] Solutions for solving problems

[0015] In one embodiment of the head-up display device according to the present invention, display light is irradiated onto a windshield of a passenger-carrying vehicle, and light reflected by the windshield is guided into the eyes of an observer to form a virtual image in front of the observer. The head-up display device comprises:

[0016] An image emitting unit including a display unit for forming an image, wherein the image emitting unit forms parallel light beams with different angles at various locations on the image and emits the parallel light beams as display light;

[0017] A light guide member that emits the light beam of the display light emitted from the image emission portion in a manner that the light beam maintains its parallelism and expands; and

[0018] A correction lens is arranged on the optical path between the light guide and the windshield, and has a curved surface shape that deflects the transmission direction of light in accordance with the curved surface shape of the reflecting surface of the windshield, so that the display light whose parallel light beam is expanded by the light guide becomes parallel after being reflected by the windshield.

[0019] Effects of the Invention

[0020] Generally, in a light guide that expands a light beam, display light including image information at a certain point on an image formed by a display unit is propagated in a state of maintaining parallelism inside the substrate of the light guide, and the parallelism of the light beam is also maintained when it is emitted from the substrate to the outside. On the other hand, for example, a car windshield generally has a relatively complex curved surface shape, and a light beam incident parallel to its reflection surface is no longer parallel after reflection and its advancing direction is scattered. This is the main reason why the HUD display is greatly distorted or shifted when the viewpoint of the observer moves.

[0021] In contrast, in the above-mentioned aspect of the head-up display device according to the present invention, the correction lens makes it possible for the light beams of each field of view to have a higher degree of parallelism and a substantially uniform degree of expansion after being reflected by the windshield, regardless of the shape of the reflection surface of the windshield. Therefore, according to the above-mentioned aspect of the head-up display device according to the present invention, even if the position of the viewpoint of the observer moves, it is possible to prevent the HUD display from being distorted or shifted, thereby providing a HUD display with good visibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic structural diagram of an optical system in a HUD system as one embodiment of the present invention.

[0023] Figure 2 This is a diagram showing an example of a schematic structure and an optical path of a light guide used in the HUD system of the present embodiment.

[0024] Figure 3 This is a diagram showing an example of an optical path when an image is projected onto a planar combiner and a windshield without using a correction lens.

[0025] Figure 4 1 is a diagram showing an example of an optical path in the HUD system according to the present embodiment.

[0026] Figure 5 It is a top plan view showing the positional relationship between a windshield and an observer in the HUD system of the present embodiment. DETAILED DESCRIPTION

[0027] A HUD system as one embodiment of the present invention will be described with reference to the accompanying drawings.

[0028] Figure 1 This is a schematic structural diagram of the optical system in the HUD system of this embodiment. Figure 2 It is shown Figure 1 A diagram showing a schematic structure of a light guide and an example of a light path.

[0029] The HUD system 1 of this embodiment is typically a system that forms a virtual image including various instrument information necessary for driving in a manner superimposed on the outside scene in front of the eyes of the observer 3 who is driving the car. There is a windshield 2 equivalent to the front windshield of the car in front of the observer 3, and the HUD system 1 is arranged below the windshield 2. The windshield 2 is a component required to form the virtual image, but the windshield 2 itself is not included in the HUD system 1 of this embodiment.

[0030] like Figure 1 As shown, the HUD system 1 includes an image forming unit 11 , an introduction optical system 12 , a light guide 13 , and a correction lens 14 in a housing 10 .

[0031] The image forming unit 11 forms a two-dimensional image (still image or moving image) as an object to be displayed, and includes, for example, a light source unit and a display element. The display element is, for example, a transmissive liquid crystal display element, and the light source unit is a backlight light source for the transmissive liquid crystal display element. However, the structure of the image forming unit 11 is not limited to this.

[0032] For example, as a display element, a reflective liquid crystal display element, an organic EL display, a micro LED display, or a DMD (digital micromirror device), a MEMS mirror, a projector, etc. can also be used. When a reflective liquid crystal display element or a DMD is used as a display element, a device that illuminates the liquid crystal display element or the DMD from the front surface side is used as a light source. In addition, when a self-luminous display element such as an organic EL display or a micro LED display is used as a display element, a light source is built into the display element. In addition, when a MEMS mirror with a scanning angle is used as a display element, a laser light source that irradiates a thin-diameter laser beam toward the MEMS mirror is used as a light source.

[0033] The introduction optical system 12 is composed of one or more reflecting mirrors or lenses, and is a collimating optical system that converts display light emitted in an expanded manner from each point (pixel) on the display surface of the display element included in the image forming unit 11 into a beam of light that is approximately parallel and has a different angle for each point.

[0034] The light guide 13 is an optical component that expands a beam of light incident in approximately parallel direction and emits it as a beam of light in approximately parallel direction. Various types and forms of devices are known for the light guide 13 having such a function. As an example, there is a light guide described in FIG. 7 of non-patent document 1, in which a mirror is formed on the incident side inside a flat transparent substrate and a large number of beam splitter surfaces are formed on the emission side. In the light guide of this structure, a beam of light incident on the substrate from the outside is reflected by the mirror on the incident side to become a total reflection condition, and total reflection is repeatedly caused at a pair of opposing surfaces of the substrate while propagating inside the substrate. When the propagated beam of light reaches the beam splitter surface, a portion of the beam of light is reflected and emitted from the substrate, and the remaining beam of light is further propagated through the beam splitter surface inside the substrate. By repeatedly reflecting a portion of the beam of light and transmitting the remaining beam of light at a plurality of beam splitter surfaces, the incident beam of light is expanded and emitted from the light guide.

[0035] In the HUD system of this embodiment, the light guide 13 is not the light guide of the above structure, but is Figure 2 The light guide member 13 is a light guide member of the type described in Patent Document 1 as shown in the figure. That is, the light guide member 13 comprises: a transparent first substrate 131, which is in the form of a flat plate and has a reflective surface 1311 formed inside thereof and inclined at a predetermined angle relative to one surface of the flat plate; and a transparent second substrate 132, one surface of which is a flat surface 1322 and the other surface of which is a concave-convex surface 1321 having a triangular wave-shaped cross section. The flat surface 1313 of one side of the first substrate 131 and the flat surface 1322 of the second substrate 132 are bonded together in such a manner that a planar beam splitter 133 formed by an optical coating or the like is sandwiched therebetween. The angle of the reflective surface 1311 is determined so that the light beam reflected by the reflective surface 1311 satisfies the total reflection condition at the interface between the first substrate 131 and the outside (air).

[0036] like Figure 2 As shown in FIG. 1 , the light beam introduced from the introduction optical system 12 to the first substrate 131 is reflected once at the reflection surface 1311. Thereafter, the light beam repeatedly undergoes total reflection at the opposing flat surfaces 1313 and 1312 of the first substrate 131 while propagating inside the substrate 131. Then, when the light beam reaches the beam splitter 133, a portion of the light beam passes through the beam splitter 133 and is emitted to the outside from the concave-convex surface 1321. The remaining light beam is reflected by the beam splitter 133, passes through the inside of the first substrate 131, and is reflected by the flat surface 1312, and then reaches the beam splitter 133 again. By repeating this process, the light beam is extended and emitted from the light guide 13 in an oblique direction.

[0037] Of course, the light guide 13 can be appropriately deformed as described in Patent Document 1, and light guides other than those described here, for example, a light guide having a structure in which a light beam is extracted from a substrate using a hologram, can be used.

[0038] The correction lens 14 is an optical member formed by combining one lens or a plurality of lenses. Details will be described later. The correction lens 14 can deflect the direction of a light beam incident on an incident surface of the lens at each point on the incident surface.

[0039] The optical path for image display in the HUD system 1 of the present embodiment will be described.

[0040] The display light as information of the image formed on the display surface of the display element included in the image forming unit 11 is emitted from the display surface. The display light emitted in various directions from a point on the display surface is collimated in the introduction optical system 12. In addition, the light emitted from different points on the display surface is collimated in different directions in the introduction optical system 12. Therefore, the display light introduced from the introduction optical system 12 to the light guide 13 is a collection of parallel light beams that respectively contain information of different parts of the image formed on the display surface of the image forming unit 11 and are incident on the light guide 13 at different angles. The light guide 13 emits the parallel incident light beams in a manner that maintains their parallelism and expands.

[0041] exist Figure 2 FIG. 1 shows the optical path of the display light emitted from a certain point on the display surface. However, the light beams emitted from different points on the display surface are extended from the light guide 13 and are directed in the same direction as the light beams emitted from the light guide 13. Figure 2 The light beams shown are parallel beams in different directions. In HUD, in order to display a virtual image generated by display light in a manner superimposed on an external scene, it is important to allow the light beam to reach the observer's eyes while maintaining its parallelism.

[0042] Figure 3 (A) is a diagram schematically showing the optical path of a light beam reaching the eye 4 of the observer 3 in the case where the correction lens 14 is not provided but the combiner 5 has a flat reflective surface. As shown in the figure, the parallel beam emitted from the light guide 13 hits the combiner 5 and is reflected while maintaining its parallelism and goes to the eye 4 of the observer 3. In this case, the focus of the virtual image is theoretically at infinity.

[0043] In contrast, Figure 1 As shown in FIG. 1 , at least a portion of the longitudinal cross-sectional shape of the windshield 2 is curved. This shape varies depending on the type of vehicle, etc., and the cross-sectional shape may be quite complex. Figure 5As shown in the top plan view in FIG. 1 , in a general automobile, the cross-sectional shape of the windshield 2 is also a symmetrical curved shape centered on the axis S, and the observer (driver) 3 sits at a position offset from the axis S. Therefore, the cross-sectional shape of the windshield 2 located in front of the observer 3 is a non-axisymmetric curved surface. As described above, the shape of the surface that reflects the display light emitted from the HUD system 1 on the windshield 2 is quite complex.

[0044] Figure 3 (B) schematically shows an example of the optical path of the light beam reaching the eye 4 of the observer 3 when the correction lens 14 is not provided and the reflecting surface is the above-mentioned windshield 2. As shown in the figure, the reflecting surface of the windshield 2 is a curved surface, and its curvature is not constant. Therefore, even if a parallel beam arrives from the HUD system 1, the reflected light will not become a parallel beam and the advancing direction of the reflected light will be scattered. The advancing direction and the degree of scattering also vary depending on the position on the reflecting surface. Therefore, when the virtual image observed by the observer 3 is distorted and the position of the eye 4 of the observer 3 is offset in the height direction, the position of the virtual image moves up and down.

[0045] In the HUD system 1 of the present embodiment, the correction lens 14 has the following function: to bend, i.e., deflect, the directions of the light beams toward the windshield 2 so that the light beams incident in parallel to the incident surface of the correction lens 14 become parallel after passing through the correction lens 14 and being reflected by the windshield 2. Figure 4 1 is a schematic diagram showing an example of the optical path of a light beam reaching the eye 4 of the observer 3 in the HUD system 1 of the present embodiment. Figure 3 The same is true for the case where the light beams heading towards the eye 4 of the observer 3 are Figure 3 The situation of (A) is the same.

[0046] In order to deflect the light beam in this way, at least one of the incident surface and the emitting surface of the correction lens 14 has a free-form surface shape corresponding to the shape of the reflection surface of the windshield 2. That is, one of the surfaces is a free-form surface shape, and the other surface can adopt various shapes such as a plane, a spherical surface, a toric surface, a cylindrical surface, etc. The shape of the surface as a free-form surface shape is designed corresponding to the shape of the reflection surface of the windshield 2.

[0047] In addition, if Figure 5As shown, the shape of the reflecting surface of the windshield 2 is usually a non-axisymmetric curved surface, and therefore, the above-mentioned free curved surface of the correction lens 14 is also a non-axisymmetric free curved surface. In addition, the reflecting surface of the windshield 2 (the surface facing the interior of the vehicle) is usually a concave shape, and therefore, the above-mentioned free curved surface of the correction lens 14 is a shape having a negative optical focal length, that is, a concave shape. As described above, the shape of the general windshield 2 varies depending on the model of the car, etc. Therefore, the curved surface shape of the incident surface and / or the exit surface of the correction lens 14 used can be changed to a different shape according to the model of the car equipped with the HUD system 1, etc. In other words, the components other than the correction lens 14 arranged in the housing 10 can be made universal, so that various models of cars can be handled by only replacing the correction lens 14.

[0048] The display light reflected by the windshield 2 reaches the eye 4 of the observer 3 as a parallel beam of light by the action of the correction lens 14. As a result, the image formed on the display surface of the image forming unit 11 is not distorted and does not depend on the movement of the viewpoint position, but is displayed as a good virtual image in front of the observer 3. In addition, the external scene light based on the forward visual field information such as the external scene in front of the observer 3 passes through the windshield 2 and reaches the eye 4 of the observer 3. As a result, the observer 3 can also visually confirm the forward visual field information.

[0049] In the HUD system 1 of the present embodiment, the correction lens 14 constitutes a part of the housing 10. That is, in the conventional HUD, in order to take out the display light from the inside of the housing to the outside, a part of the housing 10 is a transparent (or semi-transparent) cover, but in the HUD system 1, the correction lens 14 is installed instead of the cover. Therefore, the correction lens 14 prevents, for example, dust from entering the inside of the housing 10, and plays a function of protecting various components arranged inside.

[0050] The exit surface of the correction lens 14 exposed to the outside of the housing 10 reflects light coming from the outside. When the reflected light reaches the eye 4 of the observer 3, the observer 3 feels glaring, which reduces the visibility of the outside scene, etc. Therefore, it is preferable to define the shape of the exit surface of the correction lens 14 and the arrangement (orientation) of the correction lens 14 in such a way that the reflected light on the exit surface of the correction lens 14 with respect to the light incident from the outside of the vehicle through the windshield 2 into the vehicle is not directed toward the direction where the eye 4 of the observer 3 is located.

[0051] That is, in the HUD system 1 of the present embodiment, with regard to the shape of the incident surface and / or the exit surface of the correction lens 14 and the configuration of the correction lens 14, the most important thing is to make the display light emitted through the correction lens 14 become a parallel light beam after being reflected by the windshield 2, and preferably, the reflected light on the exit surface of the correction lens 14 with respect to the light incident from outside the vehicle through the windshield 2 into the vehicle is not directed in the direction where the eyes 4 of the observer 3 are located.

[0052] Furthermore, the above-described embodiment is based on the premise that the HUD system is mounted on a general automobile for use; however, the head-up display device of the present invention can of course also be used in various vehicles other than automobiles and various other mobile bodies driven or operated by humans.

[0053] In such cases, sometimes Observer 3 is not as Figure 5 As shown in the figure, it is not located at a position offset from the axis S, but is located on the axis S. In this case, the shape of the incident surface and / or the exit surface of the correction lens can of course be set as an axisymmetric free-form surface.

[0054] Furthermore, it is needless to say that the above-described embodiment is merely an example of the present invention, and even if changes, modifications, additions, etc. are appropriately made within the scope of the gist of the present invention, they are also included in the scope of the claims of the present application.

[0055] [Various ways]

[0056] It will be understood by those skilled in the art that the above-described exemplary embodiments are specific examples of the following aspects.

[0057] (Item 1) In one embodiment of the HUD device according to the present invention, display light is irradiated onto a windshield of a passenger-carrying mobile body, and light reflected by the windshield is guided to eyes of an observer to form a virtual image in front of the observer. The HUD device comprises:

[0058] An image emitting unit including a display unit for forming an image, the image emitting unit forming parallel light beams with different angles at various locations on the image and emitting the parallel light beams as display light;

[0059] A light guide member that emits the light beam of the display light emitted from the image emission portion in a manner that the light beam maintains its parallelism and expands; and

[0060] A correction lens is arranged on the optical path between the light guide and the windshield, and has a curved surface shape that deflects the transmission direction of light in accordance with the curved surface shape of the reflecting surface of the windshield, so that the display light whose parallel light beam is expanded by the light guide becomes parallel after being reflected by the windshield.

[0061] (Item 2) In the HUD device described in Item 1, at least one of the light incident surface and the light emitting surface of the correction lens can be a free-form surface.

[0062] In the HUD device described in the first and second items, due to the effect of the correction lens, the parallelism of the light beams in each field of view becomes higher and the expansion degree becomes substantially the same after being reflected by the windshield, regardless of the shape of the reflection surface of the windshield. Therefore, according to the HUD device described in the first and second items, even if the position of the viewpoint of the observer moves, the generation of distortion of the HUD display or the movement of the display position can be prevented, thereby providing a HUD display with good visibility.

[0063] (Item 3) The HUD device described in Item 2 may be a vehicle HUD device, wherein at least one surface of the correction lens is a non-axisymmetric free-form surface.

[0064] According to the HUD device described in the third item, the visibility of the virtual image displayed in front of the eyes of the driver of the car can be improved.

[0065] (Item 4) In the HUD device described in any one of Items 1 to 3, the correction lens can be configured at an angle or a curved surface shape so that reflected light of external scene light coming from the outside through the windshield does not reach the eyes of the observer.

[0066] According to the HUD device described in the fourth aspect, the degree of glare felt by the observer due to the reflected light of the correction lens can be reduced, thereby improving the visibility of the external scene and the virtual image displayed in a manner superimposed on the external scene.

[0067] (Item 5) In the HUD device described in any one of Items 1 to 3, the correction lens may also serve as a cover that is a part of a housing that houses the image emitting unit and the light guide.

[0068] According to the HUD device described in the fifth aspect, the number of optical components housed in the housing can be reduced, thereby making the size of the housing small.

[0069] Description of Reference Numerals

[0070] 1: HUD system; 10: Shell; 11: Image forming unit; 12: Introduction optical system; 13: Light guide; 131: First substrate; 1311: Reflection surface; 1312, 1313: Flat surface; 132: Second substrate; 1321: Concave-convex surface; 1322: Flat surface; 133: Beam splitter; 14: Correction lens; 2: Windshield; 3: Observer; 4: Eye.

Claims

1. A head-up display device that irradiates a windshield of a passenger-carrying mobile body with display light, guides the light reflected by the windshield into the eyes of an observer, and forms a virtual image in front of the observer, the head-up display device comprising: An image emitting unit including a display unit for forming an image, wherein the image emitting unit forms parallel light beams with different angles at various locations on the image and emits the parallel light beams as display light; a light guide member for emitting the light beam of the display light emitted from the image emitting portion while maintaining its parallelism and expanding; as well as A correction lens is arranged on the optical path between the light guide and the windshield, and has a curved surface shape that deflects the transmission direction of light in accordance with the curved surface shape of the reflecting surface of the windshield, so that the display light whose parallel light beam is expanded by the light guide becomes parallel after being reflected by the windshield.

2. The head-up display device according to claim 1, wherein: At least one of a light incident surface and a light emitting surface of the correction lens is a free-form surface.

3. The head-up display device according to claim 2, wherein: The head-up display device is a head-up display device for a vehicle, and at least one surface of the correction lens is a non-axisymmetric free-form surface shape.

4. The head-up display device according to claim 1, wherein: The correction lens is arranged at an angle or has a curved surface shape such that reflected light of external scene light coming from the outside through the windshield does not reach the eyes of the observer.

5. The head-up display device according to claim 1, wherein: The correction lens also serves as a cover which is a part of a housing in which the image emitting unit and the light guide are housed.

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