WO2014041690A1

WO2014041690A1 - Optical element and head-up display

Info

Publication number: WO2014041690A1
Application number: PCT/JP2012/073691
Authority: WO
Inventors: 柳澤　琢麿; 今井　哲也; 育也菊池
Original assignee: パイオニア株式会社
Priority date: 2012-09-14
Filing date: 2012-09-14
Publication date: 2014-03-20
Also published as: JPWO2014041690A1

Abstract

Provided is an optical element that reflects light composing a displayed image so as to cause the displayed image to be recognized visually. The optical element includes: a diffusion section that has light permeability and has a function for diffusing the light composing a displayed image; and a light condensing section that has light permeability and has a function for condensing the light composing the displayed image. The diffusion section or the light condensing section further has a function for reflecting the light composing the displayed image. The above-described optical element, which has both the diffusing function and the light condensing function with respect to the light composing the displayed image, makes it possible to ensure both the brightness of the displayed image and the size (viewing angle) of the displayed image appropriately.

Description

Optical element and head-up display

The present invention relates to a technical field in which a display image is visually recognized simultaneously with a forward view.

Conventionally, display devices such as a head-up display for visually recognizing an image as a virtual image are known. Usually, in a head-up display, a relatively small screen (real image) such as a small liquid crystal display is magnified by a magnifying optical system such as a convex lens or a concave mirror. This is because it is difficult to install a large display in the car. If a large display can be directly installed, a magnifying optical system such as a convex lens or a concave mirror is not necessary. However, when the magnifying optical system is not used, the image to be visually recognized is not a virtual image but a real image.

Also, normally, a head-up display uses a half mirror called a combiner (synthesizer) in order to make the information displayed on the display visible in a state of being superimposed on the front view. This is because a normal display is not transparent, and if the display is installed directly in front of the driver, the front view is blocked. If there is a transparent display, there is no need to use a half mirror.

In other words, if there is a large, transparent (semi-transparent) display that can be installed in the vehicle, the display can be installed in front of the driver (near the windshield) without using a magnifying optical system or a half mirror. It becomes possible to build up-displays. For example, in Patent Document 1, a reflection type diffusion plate having transparency by forming a reflection diffusion surface in a substrate (hereinafter referred to as “transparent diffusion plate” as appropriate) is used together with a projector. A method for constructing such a head-up display has been proposed.

In addition, Patent Documents 2 and 3 propose techniques related to the present invention. Patent Document 2 proposes a reflection type screen using a Fresnel lens, and Patent Document 3 proposes a thin combiner using a Fresnel lens.

JP 2010-539525 A JP 2009-169006 A JP 2000-249965 A

However, when a transparent diffusion plate as proposed in Patent Document 1 described above is used in a head-up display, the brightness of the display image and the size (viewing angle) of the display image tend to be in a dreed off relationship. That is, if the display image is configured to be bright, the size of the display image tends to be small, and if the display image is configured to be large, the display image tends to be dark.

Examples of the problem to be solved by the present invention include the above. An object of the present invention is to provide an optical element and a head-up display capable of appropriately ensuring both the brightness of a display image and the size (viewing angle) of the display image.

According to the first aspect of the present invention, an optical element that visually recognizes the display image by reflecting the light that constitutes the display image, has optical transparency, and diffuses the light that constitutes the display image. A diffusing unit having a function and a condensing unit having light transmission and a function of condensing light constituting the display image, wherein the diffusing unit or the condensing unit is the display image It further has the function to reflect the light which constitutes.

The invention according to claim 13 is an optical element for visually recognizing the display image by reflecting light constituting the display image, and the optical element includes a reflective microlens array having transparency. The microlens array is composed of an eccentric lens in which the optical axis of the microlens shifts outward as the distance from the center of the optical element increases.

According to a fifteenth aspect of the present invention, a head-up display includes an optical element according to any one of the first to fourteenth aspects, and a light source unit that emits light constituting the display image toward the optical element. It is characterized by providing.

It is the figure which showed roughly the head up display which concerns on a comparative example. The figure for demonstrating the problem of a comparative example is shown. The figure for demonstrating the optical element which concerns on 1st Example is shown. The figure for demonstrating the optical element which concerns on the 1st modification of 1st Example is shown. The figure for demonstrating the optical element which concerns on the 2nd modification of 1st Example is shown. The figure for demonstrating the optical element which concerns on 2nd Example is shown. The figure for demonstrating the suitable arrangement position of the reflective surface between microlens arrays is shown. The figure for demonstrating the optical element which concerns on the modification of 2nd Example is shown. The figure for demonstrating the optical element which concerns on 3rd Example is shown.

One aspect of the present invention is an optical element that visually recognizes a display image by reflecting the light that constitutes the display image, and has a function of diffusing the light that constitutes the display image while having light transparency. A diffusing unit having a light transmitting property, and a condensing unit having a function of condensing light constituting the display image, and the diffusing unit or the condensing unit displays the display image. It further has a function of reflecting the constituent light.

The above-described optical element is used for visually recognizing the display image by reflecting light constituting the display image. The diffusing unit has a function of diffusing the light constituting the display image while having a light transmissive property, and the light collecting unit has a function of condensing the light constituting the display image while having a light transmissive property. Have The diffusing unit or the condensing unit further has a function of reflecting light constituting the display image. According to the above optical element, since both the diffusion function and the condensing function for the light constituting the display image are provided, both the brightness of the display image and the size (viewing angle) of the display image are appropriately ensured. It becomes possible.

In one aspect of the optical element, the condensing unit is a convex lens having a Fresnel structure, and the diffusing unit receives light that constitutes the display image through the convex lens and diffuses the light. The lens further includes a concave lens having a Fresnel structure that reflects toward the convex lens, and the diffusion portion is sandwiched between the convex lens and the convex lens.

According to the above aspect, the light constituting the display image is transmitted through the convex lens having the Fresnel structure twice before and after the reflection by the diffusing portion. Therefore, it is possible to appropriately collect the light constituting the display image. In addition, according to the optical element described above, by using a Fresnel-structured concave lens together with a Fresnel-structured convex lens, light incident from the opposite direction to the light constituting the display image (hereinafter referred to as “transmitted light” as appropriate). It is possible to cancel the lens effect on the optical element, and it is possible to suppress distortions such as a forward field of view in the optical element.

In the above optical element, preferably, the convex lens and the concave lens have the same lens pitch, refractive index, and absolute value of focal length. Thereby, the mutual lens effect with respect to transmitted light can be canceled effectively.

Preferably, in the above optical element, the space between the diffusing portion and the convex lens is filled with a predetermined medium having a refractive index different from that of the convex lens, and the space between the diffusing portion and the concave lens is between The concave lens is filled with a predetermined medium having a different refractive index. Thereby, a diffusion part, a convex lens, and a concave lens can be constituted in one, securing the lens effect of a convex lens and a concave lens.

In another aspect of the optical element, the condensing part is a surface having a convex lens shape having a Fresnel structure, formed on one of two opposing surfaces constituting the optical element. The diffusion unit is formed inside the optical element, diffuses light constituting the display image incident through the light collecting unit and reflects the light toward the light collecting unit, and the optical element A surface having a Fresnel-shaped concave lens shape is further formed on the other of the two opposing surfaces constituting the lens.

In the above aspect, the optical element has a condensing part and a diffusing part integrally formed. Also with this optical element, the light constituting the display image is transmitted twice through the surface having the convex lens shape of the Fresnel structure before and after reflection by the diffusing portion. Therefore, it is possible to appropriately collect the light constituting the display image. In addition, according to the optical element described above, by using the surface having the Fresnel structure convex lens shape and the surface having the Fresnel structure concave lens shape, the lens effect on the transmitted light can be canceled, and the front field of view of the optical element, etc. It becomes possible to suppress the distortion.

In the above optical element, preferably, the convex lens shape and the concave lens shape are equal in absolute value of the lens pitch and focal length. Thereby, the mutual lens effect with respect to transmitted light can be canceled effectively.

In another aspect of the above optical element, the diffusing section includes a first diffusing section and a second diffusing section, and the condensing section is a concave mirror having a Fresnel structure formed inside the optical element. A reflecting surface having a shape, wherein the first diffusing portion is formed on one of two opposing surfaces constituting the optical element, diffuses light constituting the display image, and The second diffusing portion is formed on the other surface of the two opposing surfaces constituting the optical element.

In the above aspect, the optical element has a condensing part and a diffusing part (a first diffusing part and a second diffusing part) integrally formed. According to this optical element, the light constituting the display image travels toward the reflecting surface having a concave mirror shape having a Fresnel structure while diffusing by the first diffusing portion, and when reflected by the reflecting surface, the light again passes through the first diffusing portion. Transmitted and emitted. That is, the light constituting the display image is diffused by being transmitted twice through the first diffusion unit before and after reflection by the reflecting surface. At this time, the reflecting surface functions as a concave mirror, so that the light constituting the display image can be appropriately condensed. Further, according to the optical element described above, by using the second diffusing part together with the first diffusing part, it is possible to cancel the lens effect on the transmitted light, and it is possible to suppress distortion such as a field of view in front of the optical element. It becomes.

In another aspect of the optical element, the diffusing unit includes a first diffusing unit and a second diffusing unit, and the condensing unit includes a reflecting surface having a concave mirror shape having a Fresnel structure. The first diffusing unit is disposed to face one surface of the condensing unit and diffuses light constituting the display image, and the second diffusing unit is disposed on the other surface of the condensing unit. Opposed to each other.

In the above aspect, the optical element has a condensing part and a diffusing part (a first diffusing part and a second diffusing part) configured separately. Also with this optical element, the light that constitutes the display image can be appropriately condensed because the reflecting surface having the concave mirror shape of the Fresnel structure functions as a concave mirror. Further, by using the second diffusing unit together with the first diffusing unit, it is possible to cancel the lens effect on the transmitted light, and it is possible to suppress distortion such as a field of view in front of the optical element.

Preferably, in the above optical element, a gap between the first diffusing unit and the condensing unit is filled with a predetermined medium having a refractive index different from the refractive index of the first diffusing unit, The space between the two diffusing parts and the light collecting part is filled with a predetermined medium having a refractive index different from the refractive index of the second diffusing part. Thereby, the 1st diffusion part, the condensing part, and the 2nd diffusion part can be constituted in one, securing the lens effect of the 1st diffusion part, and the 2nd diffusion part.

In the above optical element, preferably, the first diffusing portion and the second diffusing portion are configured by a microlens array having the same shape, and a focal length of one microlens included in the microlens array. They are separated by a distance of twice. Thereby, the mutual lens effect with respect to transmitted light can be canceled effectively.

In a preferred example, a region deviating from the center of the free-form surface that is the basis of the Fresnel structure is applied as the Fresnel structure. Thereby, the position of the eye box can be appropriately changed in the vertical direction and / or the horizontal direction.

In a preferred example, the diffusing unit is constituted by a microlens array.

In another aspect of the present invention, an optical element that visually recognizes a display image by reflecting light constituting the display image, the optical element including a reflective microlens array having transparency. The microlens array is composed of an eccentric lens in which the optical axis of the microlens shifts outward as the distance from the center of the optical element increases.

Also with the above-described optical element, it is possible to appropriately realize both the diffusion function and the light collecting function, and it is possible to appropriately ensure both the brightness of the display image and the size (viewing angle) of the display image.

The above optical element is preferably configured in a flexible sheet shape and attached to the windshield of the moving body. According to such an optical element, it is possible to reduce the feeling of pressure or discomfort given to the driver or the like.

In another aspect of the present invention, a head-up display includes an optical element according to any one of claims 1 to 14, and a light source unit that emits light constituting the display image toward the optical element. Is provided. For example, a liquid crystal display or a projector can be used as the light source unit.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

<Basic concept>
First, before describing the contents of the present embodiment, the basic concept of the present embodiment will be described with reference to FIG. 1 and FIG.

FIG. 1 is a diagram schematically showing a head-up display according to Patent Document 1 described above (hereinafter referred to as “head-up display according to a comparative example”). As shown in FIG. 1, the head-up display according to the comparative example is used by being installed in the passenger compartment, and is mainly installed in front of the driver (near the windshield) and has transparency. The projector includes a reflective diffusion plate (transparent diffusion plate) 100 and a projector 200 that emits light constituting a display image. The head-up display emits light constituting the display image from the projector 200 and reflects the light emitted from the projector 200 by the transparent diffusion plate 100, thereby allowing the driver to visually recognize the display image.

1 is a cross-sectional image of the transparent diffusion plate 100 cut along a plane along the light traveling direction. The transparent diffusing plate 100 is formed by forming a reflective diffusing surface by attaching a semitransparent reflective film 100b to the convex surface of a microlens array 100a serving as a substrate, and covering the cover layer 100c with substantially the same refractive index as the substrate. According to such a transparent diffusing plate 100, light incident on the transparent diffusing plate 100 from the projector 200 is diffused and reflected, and light incident on the transparent diffusing plate 100 from the opposite side of the projector 200 is transmitted while traveling straight.

Next, with reference to FIG. 2, problems of the transparent diffusion plate 100 according to the comparative example will be described. FIG. 2A shows a case where a microlens array 100 a 1 having a relatively long curvature radius is applied to the transparent diffusion plate 100. In this case, since the diffusion angle by the microlens array 100a1 is small, the display image is bright, but the size (viewing angle) of the display image tends to be small. On the other hand, FIG. 2B shows a case where a microlens array 100 a 2 having a relatively short radius of curvature is applied to the transparent diffusion plate 100. In this case, since the diffusion angle by the microlens array 100a1 is large, the size (viewing angle) of the display image is large, but the display image tends to be dark. Thus, in the transparent diffusing plate 100 according to the comparative example, the brightness of the display image and the size (viewing angle) of the display image tend to be in a drad-off relationship.

Therefore, in this embodiment, in order to appropriately ensure both the brightness of the display image and the size (viewing angle) of the display image, the reflective optical element having transparency has both a diffusion function and a light collection function. The optical element to be applied is applied to a head-up display. Hereinafter, the configuration of a specific embodiment will be described.

<First embodiment>
First, the optical element 110 according to the first example will be described with reference to FIG. The optical element 110 according to the first example constitutes a head-up display by being applied instead of the transparent diffusion plate 100 described above (the same applies to various optical elements described later).

3 is a cross-sectional image view of the optical element 110 according to the first embodiment, cut along a plane along the light traveling direction. As shown in the cross-sectional image diagram, the optical element 110 according to the first example mainly includes a transparent diffusion plate 111, a Fresnel convex lens 112, and a Fresnel concave lens 113. The optical element 110 is configured by sandwiching a transparent diffusion plate 111 between a Fresnel convex lens 112 and a Fresnel concave lens 113, and is arranged so that the Fresnel convex lens 112 side faces the projector 200.

The transparent diffusion plate 111 has a microlens array 111a formed therein. Specifically, the transparent diffusion plate 111 forms a reflection diffusion surface by attaching a semi-transparent reflection film to the convex surface of the microlens array 111a as a substrate in the same manner as the transparent diffusion plate 100 described above. Created by covering the same refractive index cover layer. With such a configuration, the transparent diffuser plate 111 exhibits a function as a reflective diffuser plate having transparency.

The Fresnel convex lens 112 is a convex lens having a Fresnel structure (in other words, a Fresnel lens configured to function as a convex lens), and is a lens in which a normal convex lens is divided into concentric regions to reduce the thickness. Specifically, the Fresnel convex lens 112 has a surface 112 a having a convex lens shape with a Fresnel structure on the surface facing the transparent diffusion plate 111.

The Fresnel concave lens 113 is a concave lens having a Fresnel structure (in other words, a Fresnel lens configured to function as a concave lens), and is a lens in which a normal concave lens is divided into concentric regions to reduce the thickness. Specifically, the Fresnel concave lens 113 has a surface 113 a having a Fresnel-shaped concave lens shape on the surface facing the transparent diffusion plate 111.

In addition, the Fresnel convex lens 112 and the Fresnel concave lens 113 have a pitch related to the Fresnel structure (a pitch to be divided into concentric circular regions), a refractive index, and a focal length (a free curved surface (for example, a paraboloid) that is the basis of the Fresnel structure). The distance with respect to the focal point) is equal. The refractive index of the transparent diffusion plate 111 may be the same as that of the Fresnel convex lens 112 and the Fresnel concave lens 113, or may be different.

Here, the light emitted from the projector 200 enters the transparent diffusion plate 111 via the Fresnel convex lens 112, and is diffused and reflected by the transparent diffusion plate 111. Then, the light diffused and reflected by the transparent diffusion plate 111 enters the Fresnel convex lens 112 again. As described above, the light emitted from the projector 200 passes through the Fresnel convex lens 112 twice before and after the reflection by the transparent diffusion plate 111. Therefore, as indicated by arrows A11 and A12 in FIG. 3, the light from the projector 200 can be collected near the head of the driver.

That is, according to the optical element 110 according to the first embodiment, the light from the projector 200 can be diffused by the transparent diffusion plate 111 and the light from the projector 200 can be condensed by the Fresnel convex lens 112. Therefore, according to the optical element 110 according to the first embodiment, both the diffusion function and the light collecting function can be appropriately realized, and both the brightness of the display image and the size (viewing angle) of the display image are appropriately set. It can be secured. In other words, the optical element 110 according to the first embodiment has a light collecting function while being a (semi) transparent screen, so that the light use efficiency can be improved.

On the other hand, light incident on the optical element 110 from the side opposite to the projector 200 (that is, light incident from the front of the vehicle) passes through the Fresnel concave lens 113, the transparent diffuser plate 111, and the Fresnel convex lens 112 in this order. In this case, since the Fresnel convex lens 112 and the Fresnel concave lens 113 have the same pitch, refractive index, and absolute value of the focal length as described above, as shown by arrows A13 and A14 in FIG. Each other's lens effect on is canceled. Therefore, according to the optical element 110 according to the first example, it is possible to ensure transparency while appropriately suppressing the distortion of the front field of view.

As described above, in the first embodiment, the transparent diffusion plate 111 corresponds to an example of the “diffusion part” in the present invention, and the Fresnel convex lens 112 corresponds to an example of the “condensing part” in the present invention.

It should be noted that the thinner the transparent diffusion plate 111, the higher the transparency with respect to the transmitted light from the oblique direction.

In addition, the gap between the transparent diffuser plate 111 and the Fresnel convex lens 112 and the gap between the transparent diffuser plate 111 and the Fresnel concave lens 113 may be an air layer, but may be filled with a transparent resin or the like in order to integrally form them. good. However, as a material for filling the gap, a material having a refractive index different from that of the Fresnel convex lens 112 and the Fresnel concave lens 113 may be used so that the lens effects of the Fresnel convex lens 112 and the Fresnel concave lens 113 are not lost.

Furthermore, the Fresnel convex lens 112 and the Fresnel concave lens 113 may have a Fresnel structure in which the center of the free-form surface (for example, the apex of the paraboloid) is not located at the center thereof. That is, a region off the center of the Fresnel pattern may be applied to the Fresnel convex lens 112 and the Fresnel concave lens 113. However, when the optical element 110 is observed from the front, it is desirable that the convex lens position and the concave lens position be aligned with the Fresnel convex lens 112 and the Fresnel concave lens 113. In this way, by applying a region deviating from the center of the Fresnel pattern, the position of the eye box EB can be appropriately changed in the vertical direction and / or the horizontal direction.

In addition, the Fresnel convex lens 112 and the Fresnel concave lens 113 may be configured by using a plurality of Fresnel lens shapes (in this case, an area outside the center of the Fresnel pattern may be applied). Thereby, a plurality of eyeboxes EB can be formed.

Next, modified examples (first modified example and second modified example) of the first embodiment will be described with reference to FIGS.

FIG. 4 shows an optical element 120 according to a first modification of the first embodiment. FIG. 4 is a cross-sectional image view of the optical element 120 according to the first modification, cut along a plane along the light traveling direction.

As shown in FIG. 4, in the optical element 120, surfaces 120b and 120c having a Fresnel structure are formed on two opposing surfaces (that is, both surfaces). Specifically, the optical element 120 has a surface 120b having a convex lens shape having a Fresnel structure (in other words, a surface shape of a Fresnel lens configured to function as a convex lens) on one of two opposing surfaces. Is formed. The optical element 120 has a surface 120c having a Fresnel-shaped concave lens shape (in other words, a surface shape of a Fresnel lens configured to function as a concave lens) on the other of the two opposing surfaces. ing. The optical element 120 is arranged so that the surface 120b faces the projector 200.

Also, the optical element 120 has a transparent diffusion portion 120a formed therein. The transparent diffusing unit 120a is configured by attaching a semitransparent reflective film to the convex surface of the microlens array. That is, the optical element 120 includes a surface 120b having a convex lens shape with a Fresnel structure and a surface 120c having a concave lens shape with a Fresnel structure on each surface of the substrate on which the transparent diffusion portion 120a is formed and the cover layer covering the substrate. It can be said that was formed.

It should be noted that the convex lens shape of the surface 120b and the concave lens shape of the surface 120c have the same absolute value of the lens pitch and focal length. Further, the substrate and the cover layer have substantially the same refractive index.

Even with the optical element 120 according to the first modification, the light emitted from the projector 200 is transmitted twice through the surface 120b having a Fresnel-shaped convex lens shape before and after the reflection by the transparent diffusion portion 120a. Light from 200 can be collected near the driver's head. Therefore, both the diffusion function and the light collecting function can be appropriately realized, and both the brightness of the display image and the size (viewing angle) of the display image can be appropriately ensured. In addition, according to the optical element 120 according to the first modification, the convex lens shape of the surface 120b and the concave lens shape of the surface 120c have the same absolute value of the pitch and the focal length, so the mutual lens effect on the transmitted light is canceled out. Transparency can be ensured while appropriately suppressing distortion of the front field of view.

Furthermore, according to the optical element 120 according to the first modification, the thickness can be reduced as compared with the optical element 110 according to the first embodiment. However, it can be said that the optical element 120 according to the first modified example is likely to be contaminated because the surface has irregularities. Therefore, the surface of the optical element 120 may be covered with a transparent resin or the like. However, the refractive index of the transparent resin is made different from that of the substrate and the cover layer so that the functions of the convex lens and the concave lens are not lost.

As described above, in the first modification of the first embodiment, the transparent diffusion portion 120a corresponds to an example of the “diffusion portion” in the present invention, and the surface 120b having the convex lens shape of the Fresnel structure is “ It corresponds to an example of a “condenser”.

In addition, you may apply the area | region which remove | deviated from the center of the Fresnel pattern to the surface 120b and the surface 120c. However, it is desirable that the convex lens position and the concave lens position are aligned when the optical element 120 is observed from the front. Further, the surface 120b and the surface 120c may be configured using a plurality of Fresnel lens shapes (in this case, a region off the center of the Fresnel pattern may be applied together).

FIG. 5 shows an optical element 130 according to a second modification of the first embodiment. On the upper side of FIG. 5, a cross-sectional image view of the optical element 130 according to the second modification example cut along a plane along the light traveling direction is shown.

Similar to the optical element 120 according to the first modification, the optical element 130 according to the second modification has a transparent diffusion portion 130a, a surface 130b having a Fresnel structure convex lens shape, and a surface 120c having a Fresnel structure concave lens shape. And have. The optical element 130 according to the second modification is obtained by configuring the optical element 120 according to the first modification in a flexible sheet shape, and the basic configuration is the same as the optical element 120 according to the first modification. . Therefore, description of the same configuration is omitted here, and only a different configuration is described.

The optical element 130 according to the second modification is attached to the windshield of the vehicle. Specifically, the optical element 130 is installed along the curvature of the windshield. As a result, it is possible to reduce the feeling of pressure or discomfort given to the driver or the like. In this case, the focal length of the surface 130b having the Fresnel-shaped convex lens shape is set so that the eye box EB is suitable for the vicinity of the driver's head in consideration of the light collecting effect caused by placing the optical element 130 along the windshield. What is necessary is just to set so that it may be located in. Further, when the windshield is tilted vertically or tilted to the left or right, the eyebox EB is placed near the driver's head by applying an area appropriately shifted from the center of the Fresnel pattern to the surface 130b. What is necessary is just to set so that it may be located appropriately.

Note that the configuration in which the optical element described in the second modification is formed into a sheet shape can be applied to the optical element 110 according to the first embodiment described above. It can also be applied to the optical element shown in FIG.

<Second embodiment>
Next, a second embodiment will be described with reference to FIG. In the upper side of FIG. 6, a cross-sectional image view of the optical element 140 according to the second example, cut along a plane along the light traveling direction, is shown.

As shown in the cross-sectional image diagram, the optical element 140 according to the second example has microlens

arrays

140a and 140c formed on two opposing surfaces (that is, both surfaces). The optical element 140 is arranged so that the surface on which the microlens array 140a is formed faces the projector 200.

Also, the optical element 140 has a reflecting surface 140b having a concave mirror shape with a Fresnel structure (in other words, a reflecting surface shape with a Fresnel structure configured to function as a concave mirror) formed therein. That is, in the optical element 140, the reflection surface 140b is formed between the microlens array 140a and the microlens array 140c. The reflective surface 140b is configured by attaching a translucent reflective film to a surface having a concave mirror shape with a Fresnel structure. The reflective surface 140b corresponds to a surface (concave surface) that is recessed toward the microlens array 140a.

Furthermore, the microlens array 140a and the microlens array 140c have the same shape. Specifically, in the microlens array 140a and the microlens array 140c, microlenses having the same shape are arranged at the same lens pitch. The microlens array 140a and the microlens array 140c are separated from each other by a distance twice as long as the focal length of the microlens (a value converted in terms of refractive index is used). That is, it is configured to be a beam expander system with a magnification of 1. Note that the reflecting surface 140b having the Fresnel structure does not need to be disposed at an intermediate position between the microlens array 140a and the microlens array 140c.

Here, the light emitted from the projector 200 is transmitted to the reflection surface 140b of the Fresnel structure while being collected by the microlens array 140a, and is transmitted again through the microlens array 140a while being diffused when reflected by the reflection surface 140b. Emitted. At this time, since the reflecting surface 140b having the Fresnel structure functions as a concave mirror, the light from the projector 200 can be collected near the head of the driver as indicated by arrows A21 and A22 in FIG. Therefore, both the diffusing function and the condensing function can be appropriately realized by the optical element 140 according to the second embodiment, and both the brightness of the display image and the size (viewing angle) of the display image are appropriately ensured. It becomes possible to do.

On the other hand, light incident on the optical element 140 from the front of the vehicle passes through the microlens array 140c, the reflective surface 140b, and the microlens array 140a in this order. In this case, the microlens array 140a and the microlens array 140c have the same shape and are separated from each other by a distance twice as long as the focal length of the microlens, and are indicated by arrows A23 and A24 in FIG. Thus, the mutual lens effect on the transmitted light is canceled. Therefore, the optical element 140 according to the second example can also ensure transparency while appropriately suppressing the distortion of the front field of view.

As described above, in the second embodiment, the microlens array 140a corresponds to an example of the “first diffusion portion” in the present invention, and the microlens array 140c corresponds to an example of the “second diffusion portion” in the present invention. Correspondingly, the reflecting surface 140b having a Fresnel-shaped concave mirror shape corresponds to an example of the “light collecting portion” in the present invention.

In addition, you may apply the area | region which remove | deviated from the center of the Fresnel pattern to the reflective surface 140b. Thereby, the position of the eye box EB can be appropriately changed in the vertical direction and / or the horizontal direction. Further, the reflecting surface 140b may be configured by using a plurality of Fresnel lens shapes (in this case, a region off the center of the Fresnel pattern may be applied together). Thereby, a plurality of eyeboxes EB can be formed.

Here, with reference to FIG. 7, a preferred arrangement position of the reflecting surface 140b between the microlens array 140a and the microlens array 140c will be described. FIG. 7A shows a case where the reflecting surface 140b is arranged on the microlens array 140c side, and FIG. 7B shows that the reflecting surface 140b is arranged approximately in the middle between the microlens array 140a and the microlens array 140c. FIG. 7C shows a case where the reflection surface 140b is arranged on the microlens array 140a side. As shown in FIG. 7A, when the reflecting surface 140b is arranged, it can be seen that diffusion starts before being reflected. On the other hand, when the reflective surface 140b is arranged as shown in FIG. 7C, it can be seen that the light is condensed immediately after reflection and diffused thereafter. As described above, when the reflecting surface 140b is disposed as shown in FIG. 7C, the degree of diffusion is reduced. Therefore, the reflecting surface 140b is disposed as shown in FIGS. 7A and 7B. Is desirable.

Next, a modification of the second embodiment will be described with reference to FIG. FIG. 8 shows a cross-sectional image diagram of an optical element 150 according to a modification of the second embodiment, cut along a plane along the traveling direction of the light 7.

As shown in FIG. 8, an optical element 150 according to a modification of the second embodiment includes

microlens array portions

151 and 153 and a Fresnel reflection surface portion 152. The optical element 150 is configured by sandwiching the Fresnel reflection surface portion 152 between the

microlens array portions

151 and 153, and is arranged so that the microlens array portion 151 side faces the projector 200.

In the

microlens array portions

151 and 153, the

microlens arrays

151a and 153a are formed on the surfaces facing the Fresnel reflection surface portion 152, respectively. That is, the

microlens array portions

151 and 153 are arranged so that the convex side faces the Fresnel reflection surface portion 152. In the

microlens arrays

151a and 153a, microlenses having the same shape are arranged at the same lens pitch, and the focal length of the microlens (a value converted by a refractive index is used) is twice. They are separated by a distance.

The reflection surface 152a having a Fresnel structure concave mirror shape (in other words, a Fresnel structure reflection surface shape configured to function as a concave mirror) is formed inside the Fresnel reflection surface portion 152. The reflection surface 152a is configured by attaching a translucent reflection film to a surface having a concave mirror shape with a Fresnel structure, and forms a Fresnel reflection surface portion 152 by being covered with a flat plate. The reflective surface 152a corresponds to a surface (concave surface) that is recessed toward the microlens array portion 151 side.

Also by the optical element 150 according to the modified example of the second embodiment, the light from the projector 200 can be collected in the vicinity of the driver's head because the reflecting surface 152a having the Fresnel structure functions as a concave mirror. . Therefore, both the diffusion function and the light collecting function can be appropriately realized, and both the brightness of the display image and the size (viewing angle) of the display image can be appropriately ensured. Further, according to the optical element 150 according to the modification of the second embodiment, the

microlens arrays

151a and 153a have the same shape and are separated by a distance twice as long as the focal length of the microlens. Since the mutual lens effect with respect to the transmitted light is canceled out, it is possible to ensure transparency while appropriately suppressing distortion of the front field of view.

As described above, in the modified example of the second embodiment, the microlens array unit 151 corresponds to an example of the “first diffusion unit” in the present invention, and the microlens array unit 153 includes the “second diffusion unit” in the present invention. The Fresnel reflection surface portion 152 corresponds to an example of a “light collecting portion” in the present invention.

Note that the gap between the microlens array portion 151 and the Fresnel reflection surface portion 152 and the gap between the microlens array portion 153 and the Fresnel reflection surface portion 152 may be an air layer, but a transparent resin or the like is used in order to integrally form them. It may be filled with. However, as a material for filling the gap, a material having a refractive index different from that of the

microlens array units

151 and 153 may be used so that the lens effect of the

microlens array units

151 and 153 is not lost.

Further, a region off the center of the Fresnel pattern may be applied to the reflecting surface 152a. Further, the reflection surface 152a may be configured using a plurality of Fresnel lens shapes (in this case, a region off the center of the Fresnel pattern may be applied together).

<Third embodiment>
Next, a third embodiment will be described with reference to FIG. On the upper side of FIG. 9, a cross-sectional image view of the optical element 160 according to the third example cut along a plane along the light traveling direction is shown.

As shown in the cross-sectional image diagram, the optical element 160 according to the third example has a microlens array 160a formed therein. The microlens array 160a has a translucent reflective film on the convex surface. The microlens array 160a is formed of an eccentric lens in which the intervals between the microlenses are equal, but the optical axis of each microlens shifts outward as the distance from the center of the optical element 160 increases. The closer the microlens array 160a is to the periphery, the greater the amount by which the optical axis of the microlens is shifted outward with respect to the thickness direction of the optical element 160. For example, in the microlens array 160a, the optical axis of each microlens is shifted so as to have the same inclination as the surface constituting the Fresnel lens.

According to the optical element 160 according to the third example, the light emitted from the projector 200 is diffused and reflected by the microlens array 160a. In the third example, since the optical axis of each microlens of the microlens array 160a is shifted toward the outer side, the diffusion of light to the outside by the microlens array 160a is suppressed. Therefore, as indicated by arrows A31 and A32 in FIG. 9, light from the projector 200 can be collected near the head of the driver. Therefore, both the diffusion function and the light collecting function can be appropriately realized by the optical element 160 according to the third embodiment, and both the brightness of the display image and the size (viewing angle) of the display image are appropriately ensured. It becomes possible to do.

Further, in the optical element 160 according to the third example, as indicated by arrows A33 and A34 in FIG. 9, the lens effect is not particularly given to the light incident from the front of the vehicle. Transparency can be ensured while appropriately suppressing.

Furthermore, according to the optical element 160 according to the third example, since the Fresnel lens (including the surface of the Fresnel lens shape) as shown in the first example and the second example is not used, the manufacturing cost is reduced. It becomes possible.

<Modification>
Although the example using a microlens array as a diffusion part in the present invention has been described above, the present invention is not limited to this. Instead of the microlens array, a lenticular lens, a random scattering surface, or the like may be used as the diffusion unit in the present invention. In the optical element 160 shown in the third example, a lenticular lens may be used instead of the microlens array 160a.

The present invention can be used for a head-up display or a reflective screen.

110, 120, 130, 140, 150, 160 Optical element 111 Transparent diffuser plate 112 Fresnel convex lens 113 Fresnel concave lens 200 Projector EB Eye box

Claims

An optical element that visually recognizes the display image by reflecting light constituting the display image,
A diffusing unit having light transmission and a function of diffusing light constituting the display image;
A light condensing unit having a light transmissive property and a function of condensing light constituting the display image,
The diffusing unit or the condensing unit further has a function of reflecting light constituting the display image.
The condensing part is a convex lens having a Fresnel structure,
The diffuser is configured such that light constituting the display image is incident through the convex lens, diffuses the light, and reflects the light toward the convex lens.
The optical element according to claim 1, further comprising a concave lens having a Fresnel structure, wherein the diffusing portion is sandwiched between the convex lens and the convex lens.
3. The optical element according to claim 2, wherein the convex lens and the concave lens have the same lens pitch, refractive index, and absolute value of focal length.
The space between the diffusion part and the convex lens is filled with a predetermined medium having a refractive index different from that of the convex lens.
4. The optical element according to claim 2, wherein a space between the diffusing portion and the concave lens is filled with a predetermined medium having a refractive index different from that of the concave lens.
The condensing part is a surface having a convex lens shape with a Fresnel structure, formed on one of two opposing surfaces constituting the optical element,
The diffusing unit is formed inside the optical element, diffuses the light constituting the display image incident through the condensing unit and reflects it toward the condensing unit,
2. The optical element according to claim 1, wherein a surface having a Fresnel-shaped concave lens shape is further formed on the other of the two opposing surfaces constituting the optical element.
6. The optical element according to claim 5, wherein the convex lens shape and the concave lens shape have the same lens pitch and focal length absolute values.
The diffusion part has a first diffusion part and a second diffusion part,
The condensing part is a reflecting surface formed inside the optical element and having a concave mirror shape with a Fresnel structure,
The first diffusing portion is formed on one of two opposing surfaces constituting the optical element, and diffuses the light constituting the display image,
2. The optical element according to claim 1, wherein the second diffusing portion is formed on the other of the two opposing faces constituting the optical element.
The diffusion part has a first diffusion part and a second diffusion part,
The condensing part has a reflecting surface having a concave mirror shape with a Fresnel structure formed inside,
The first diffusion unit is disposed to face one surface of the light collecting unit, diffuses light constituting the display image,
The optical element according to claim 1, wherein the second diffusing unit is disposed to face the other surface of the light collecting unit.
The space between the first diffusion part and the light collecting part is filled with a predetermined medium having a refractive index different from the refractive index of the first diffusion part,
The optical system according to claim 8, wherein a space between the second diffusing unit and the condensing unit is filled with a predetermined medium having a refractive index different from a refractive index of the second diffusing unit. element.
The first diffusing unit and the second diffusing unit are configured by a microlens array having the same shape, and are separated by a distance twice the focal length of one microlens included in the microlens array. The optical element according to claim 7, wherein the optical element is an optical element.
The optical element according to any one of claims 2 to 10, wherein a region deviating from the center of a free-form surface that is the basis of the Fresnel structure is applied as the Fresnel structure.
The optical element according to any one of claims 1 to 11, wherein the diffusing unit is configured by a microlens array.
An optical element that visually recognizes the display image by reflecting light constituting the display image,
The optical element includes a reflective microlens array having transparency,
The optical element, wherein the microlens array is configured by an eccentric lens in which the optical axis of the microlens is shifted outward as the distance from the center of the optical element increases.
The optical element according to claim 1, wherein the optical element is configured in a flexible sheet shape and attached to a windshield of a moving body.
A head-up display comprising: the optical element according to any one of claims 1 to 14; and a light source unit that emits light constituting the display image toward the optical element.