WO2019171450A1

WO2019171450A1 - Image display device

Info

Publication number: WO2019171450A1
Application number: PCT/JP2018/008469
Authority: WO
Inventors: 与希有田
Original assignee: 株式会社島津製作所
Priority date: 2018-03-06
Filing date: 2018-03-06
Publication date: 2019-09-12
Also published as: JPWO2019171450A1

Abstract

According to the present invention, image light that has been generated by a light source part and a display element passes through a collimator optical system and is introduced into a light guide (10). The image light is reflected by an incidence-side reflection surface (101) that is inside a substrate (100) of the light guide (10), is totally reflected between a narrowly spaced first surface and second surface, and arrives at a plurality of emission-side reflection surfaces (102a–102e) that constitute a beam splitter. A portion of the image light that has been reflected by the incidence-side reflection surface (101) strikes a third surface and a fourth surface (100e, 100f), but the third surface and the fourth surface (100e, 100f) are both non-reflecting surfaces. As a result, almost no light that has been reflected by the third surface and the fourth surface (100e, 100f) reaches the emission-side reflection surfaces (102a–102e). Image light that has been reflected by the plurality of emission-side reflection surfaces (102a–102e) forms a virtual image in front of an eye E of an observer, and there is no overlap by a right-left-inverted ghost from light reflected at the third surface and the fourth surface (100e, 100f), which makes it possible to achieve high visibility.

Description

Image display device

The present invention relates to an image display device that displays image information as a virtual image in front of a user's eyes, and more particularly to an image display device that uses a light guide that expands a light beam (exit pupil). The image display device according to the present invention is suitable for an image display device such as a helmet-mounted display, a head-up display, or a glasses-type display (so-called smart glass).

In automobiles and trains, a head that forms a display image with a virtual image in front of the driver's eyes by projecting an image displayed on a display element such as a liquid crystal display (LCD) onto a windshield or combiner and reflecting the image on the driver's side Up display is used. Also, in aircraft, a helmet-mounted display that projects images onto a combiner provided in a helmet worn by the pilot on the head and forms a display image as a virtual image in front of the pilot is used by a similar mechanism. . Recently, eyeglass-type or head-mounted head-mounted displays called smart glasses have begun to spread.

Such image display devices are known in various types as an optical system for displaying a virtual image in front of the observer's eyes, and one of them is a method using a light guide (light guide plate). As described in

Patent Documents

1 and 2,

Non-Patent Documents

1 and 2, and the like, a light beam having a small cross-sectional area including image information formed by an image forming unit and a collimating optical system is formed in a substantially rectangular flat plate shape. It is introduced into a certain light guide, and the light beam is enlarged and displayed by the light guide. In the following description, an image display device using such a light guide is simply referred to as an image display device.

4 and 5 are schematic views showing an optical path configuration in an example of a conventional image display device. FIG. 4 is a diagram of a state where an observer observing the displayed image is viewed from the side, and FIG. It is the figure of the state which looked at the light guide 20 in 4 from the front. For convenience of explanation, x, y, and z axes orthogonal to each other are defined as shown in the figure.

The image display device 2 includes a light source unit 21, a display element 22, a collimating optical system 23, and a light guide 20. Here, the display element 22 is a transmissive liquid crystal display element, and the light source unit 21 is a backlight light source for a so-called transmissive liquid crystal display element. The light emitted from the light source unit 21 illuminates the display element 22 from the back side, and light including information formed on the display surface of the display element 22 as information (hereinafter referred to as “image light”) is emitted from the display element 22. Is done. The collimating optical system 23 introduces the image light emitted from each point (pixel) on the display surface of the display element 22 into the light guide 20 as a substantially parallel light beam. Accordingly, the light introduced from the collimating optical system 23 into the light guide 20 includes information on different parts of the image formed on the display surface of the display element 22 and enters the light guide 20 at different angles. Is a set of

The light guide 20 includes a transparent substrate 200 having a flat cubic shape having a first surface 200a and a second surface 200b parallel to the yz plane, and a third surface 200c and a fourth surface 200d parallel to the xy plane. Prepare. Inside the substrate 200, one incident-side reflecting surface 201 and a plurality (three in this example) of exit-side reflecting surfaces 202a to 202c are formed. The incident-side reflection surface 201 is perpendicular to the third surface and the fourth surface, and is inclined with respect to the first surface 200a and the second surface 200b. Similarly, the plurality of exit-side reflecting surfaces 202a to 202e are perpendicular to the third surface and the fourth surface, are inclined with respect to the first surface 200a and the second surface 200b, and are parallel to each other. The incident-side reflecting surface 201 is a reflecting surface such as a mirror, and the exit-side reflecting surfaces 202a to 202c are partial reflecting surfaces having a predetermined reflectance (that is, transmittance), that is, a beam splitter or a half mirror.

As described above, the image light introduced from the collimating optical system 23 into the light guide 20 is reflected by the incident-side reflection surface 201 and then totally reflected one or more times by the second surface 200b and the first surface 200a. 200 propagates inside 200 and reaches the exit-side reflection surface 202a. The exit-side reflecting surface 202a reflects part of the arrived image light and transmits the rest. The transmitted image light reaches the next exit-side reflecting surface 202b, a part of the light is reflected, and the rest is transmitted. The same applies to the exit-side reflecting surfaces 202c to 202e. Therefore, the image light propagating through the inside of the substrate 200 of the light guide 20 is reflected by each of the plurality of exit-side reflecting surfaces 202a to 202c, passes through the first surface 200a of the substrate 200, and exits to the outside. The image light reflected by the exit-side reflecting surfaces 202a to 202e is incident on the observer's eye E at a predetermined angle.

As described above, the image light including information on different parts of the image formed on the surface of the display element 22 is incident on the light guide 20 at different angles as a parallel light flux and is reflected by the incident-side reflection surface 201. In the process in which the light beam propagates through the substrate 200 while being totally reflected by the first surface 200a and the second surface 200b, is partially reflected by the plurality of exit-side reflecting surfaces 202a to 202e, and is emitted from the substrate 200. The luminous flux, ie the exit pupil, is enlarged. In this way, in the image display device 2, the image formed on the display surface of the display element 22 is displayed as a virtual image in front of the observer's eyes. Further, since the substrate 200 of the light guide 20 is transparent and the exit-side reflecting surfaces 202a to 202e are partially reflecting surfaces, the observer can also visually recognize the scenery in front through the light guide 20.

The see-through type image display device using such a light guide has a feature of being compact and lightweight. However, the conventional image display apparatus has the following problems.
That is, among the image light introduced from the collimating optical system 23 to the light guide 20, the light beam derived from the light emitted from the vicinity of the center of the display surface of the display element 22 is shown by a two-dot chain line in FIG. Further, after being reflected by the incident-side reflecting surface 101, it propagates along the y-axis in the yz plane. On the other hand, in the image light introduced from the collimating optical system 23 to the light guide 20, the light beam derived from the light emitted from the position close to the left and right end (z-axis direction) on the display surface of the display element 22 is As indicated by the alternate long and short dash line in FIG. 5, after being reflected by the incident-side reflecting surface 101, it propagates within the yz plane with a predetermined angle with respect to the y axis (that is, obliquely upward). In the light guide 20, the distance between the third surface 200c and the fourth surface 200d is larger than the distance between the first surface 200a and the second surface 200b. Therefore, the image light propagating at a predetermined angle with respect to the y-axis in the yz plane is unlikely to reach the third surface 200c or the fourth surface 200d, but the third surface 200c on the incident-side reflective surface 201. And part of the image light reflected at a position relatively close to the fourth surface 200d hits the third surface 200c or the fourth surface 200d and is reflected. Thus, the image light reflected by the third surface 200c and the fourth surface 200d and the image light not reflected by the third surface 200c are reflected by the exit-side reflection surfaces 202a to 202e, respectively, and reach the observer's eye E.

FIG. 5 schematically shows images obtained at three positions I, II, and III on the light guide 20 at the top of the light guide 20.

Numbers

1, 2, and 3 in the image indicate positions on the image formed on the display surface of the display element 22, respectively, 2 is the center of the image, and 1 and 3 are near the left and right edges of the image, respectively. Indicates the position. In addition, [1], [2], and [3] in FIG. 5 indicate the traveling directions of the luminous fluxes of image light emitted from 1, 2, and 3 on the image formed on the display surface of the display element 22, respectively. Show. For example, the image light obtained at the position II on the light guide 20 is reflected by the light beam [2] emitted from the vicinity of the center of the display surface of the display element 22 which is reflected by the position ii on the incident-side reflection surface 201 and incident. The light beam [1] emitted from the end of the display surface of the display element 22 that is reflected at the position i on the side reflection surface 201 and the display element 22 that is reflected at the position iii on the incident side reflection surface 201 and arrives. Luminous flux [3] emitted from the end of the display surface.

On the other hand, for example, the image light obtained at the position I on the light guide 20 is reflected by the position i on the incident-side reflection surface 201, and the light flux [2] emitted from the vicinity of the center of the display surface of the display element 22 arrives. The light beam [3] emitted from the end of the display surface of the display element 22 that has been reflected and arrived at the position ii on the incident side reflection surface 201 and the fourth surface 200d reflected at the position i on the incident side reflection surface 201 And the light beam [3] emitted from the end portion of the display surface of the display element 22 that is reflected and arrives. The image light that is reflected and arrives at the fourth surface 200d is reflected only once, and therefore includes image information in which the left and right are reversed (specularly reflected). Therefore, the image light reflected once is superimposed as an image obtained by horizontally inverting the original image. Similarly, the image obtained at the position III on the light guide 20 is also an overlapping of the images that are emitted from the position [iii] and reflected by the third surface 200c and reversed left and right.

A ghost that is not a simple ghost as described above but that causes the image to be reversed horizontally particularly reduces the visibility of the image. An image displayed by an image display device used by a vehicle driver or an aircraft operator often includes important character information to be notified during driving or maneuvering. May greatly reduce the visibility of characters.
In the above example, the light guide 20 is arranged so as to extend in the vertical direction (y-axis direction), so that a horizontally inverted ghost is generated, but the light guide is extended in the horizontal direction (z-axis direction). In the arranged image display device, a ghost of upside down is generated.

Japanese Patent No. 5447714 Japanese Patent No. 5299391

The present invention has been made to solve the above-described problems, and the object of the present invention is to reduce the occurrence of a ghost that is flipped left and right or up and down, which leads to a significant decrease in visibility. An image display device is provided.

An image display device according to the present invention, which has been made to solve the above problems,
a) an image forming unit that emits image light including, as information, an image formed on the screen of the display element;
b) an incident optical system that collimates the image light from the image forming unit and enters the light guide, which will be described later,
c) a transparent substrate having first and second surfaces facing each other in parallel and a third surface and a fourth surface facing each other with a separation distance longer than the separation distance between the first surface and the second surface; An incident portion that guides the image light incident through the incident optical system to the inside of the substrate so as to be totally reflected by the first surface and the second surface, and is guided from the incident portion to the inside of the substrate. A light guide having an emission unit that emits image light propagated through the substrate while being totally reflected by the first surface and the second surface to the outside of the substrate at a predetermined position while expanding the light flux; ,
And a part of at least one of the third surface and the fourth surface of the light guide is a non-reflective surface.

Here, specifically, “a part of at least one of the third surface and the fourth surface” is at least a part of a portion where the image light guided to the inside of the substrate by the incident part can reach.

In the present invention, the non-reflective surface may be any surface as long as it has an effect of eliminating or reducing the degree of reflection at the interface between the substrate and its external environment (typically, the outside atmosphere). It may be.

For example, as one aspect of the present invention, the non-reflective surface may be a light shielding surface. Specifically, for example, such a light shielding surface can be formed by applying an antireflection agent to the surface of the substrate. As another aspect of the present invention, the non-reflective surface may be a light scattering surface. Specifically, for example, such a light scattering surface can be a surface subjected to a process for forming fine irregularities on the surface of the substrate, for example, a polishing process.

In the present invention, the image light that has been collimated through the incident optical system and introduced into the light guide substrate is totally reflected by the light guide incident portion between the first surface and the second surface of the substrate. Guided into the substrate. The image light propagates through the inside of the substrate and reaches the emission part while being totally reflected between the first surface and the second surface, which are narrower than the separation distance between the third surface and the fourth surface. . Then, image light is extracted from the substrate to the outside by the emitting unit, and a virtual image is formed in front of the observer's eyes. On the other hand, part of the image light guided into the substrate by the incident portion hits the third surface and the fourth surface while facing the first surface and the second surface, respectively, but at least the portion where the image light hits on these surfaces is not Since it is a reflective surface, the image light that hits it will not be reflected. For this reason, the image light emitted to the outside of the substrate in the emitting portion, that is, the image light contributing to the formation of the virtual image does not include the reflected light on the third surface and the fourth surface. Thereby, for example, a phenomenon that a ghost in which the image as described above is reversed left and right or up and down is generated can be reduced.

According to the image display device of the present invention, it is possible to reduce the superimposition of a ghost that is reversed left and right or up and down on a regular image and improve the visibility of a virtual image displayed by a light guide. .

It is a schematic block diagram of the optical system in the image display apparatus which is one Example of this invention, and is the sectional view of the state which looked at the observer observing the image displayed from the side. It is a schematic block diagram of the optical system in the image display apparatus of a present Example, and is the top view of the state which looked at the light guide 10 in FIG. 1 from the front. The top view of the state which looked at the light guide 10 in the image display apparatus of a present Example from the downward direction. It is a schematic block diagram of the optical system in the conventional image display apparatus, and is sectional drawing of the state which looked at the observer observing the image displayed from the side. It is a schematic block diagram of the optical system in the conventional image display apparatus, and the top view of the state which looked at the light guide 20 in FIG. 4 from the front.

An image display apparatus according to an embodiment of the present invention will be described with reference to the accompanying drawings.
FIG. 1 and FIG. 2 are schematic configuration diagrams of an optical system in the image display apparatus according to the present embodiment. Like FIG. 4 and FIG. 5, FIG. 1 shows an observer observing the displayed image from the side. FIG. 2 is a plan view of the light guide 10 in FIG. 1 as viewed from the front. FIG. 3 is a plan view of the light guide 10 in FIG. 1 as viewed from below.

The image display apparatus 1 according to the present embodiment includes a light source unit 11, a display element 12, a collimating optical system 13, and a light guide 10 as in the conventional image display apparatus 2 shown in FIGS. The light source unit 11, the display element 12, and the collimating optical system 13 can be the same as the light source unit 21, the display element 22, and the collimating optical system 23 in the conventional image display apparatus 2, but are not limited thereto. For example, as the display element 12, a reflective liquid crystal display element, an organic EL display, a DMD (digital macro mirror device), a MEMS mirror, or the like can be used instead of the transmissive liquid crystal display element.

When a reflective liquid crystal display element or DMD is used as the display element 12, the light source unit 11 illuminates the liquid crystal display element or DMD from the front side. When a self-luminous display element such as an organic EL display is used as the display element 12, it can be considered that the light source unit 11 is built in the display element 12. When a MEMS mirror whose angle is scanned is used as the display element 12, a laser light source that irradiates a thin laser beam toward the MEMS mirror may be used as the light source unit 11.

Like the light guide 20 in the conventional image display device 2, the light guide 10 includes a first surface 100a and a second surface 100b parallel to the yz plane, a third surface 100e and a second surface 100e parallel to the xy plane. A substrate 100 having a flat cubic shape having four surfaces 100f is provided. The substrate 100 is a transparent body such as polycarbonate resin or quartz glass. Inside the substrate 100, there is one incident-side reflecting surface 101 corresponding to the incident portion in the present invention, and a plurality of (in this example, five) exit-side reflecting surfaces 102a to 102e corresponding to the emitting portion in the present invention. Is formed. The incident-side reflection surface 101 is perpendicular to the third surface 100e and the fourth surface 100f, and is inclined (non-parallel) to the first surface 100a and the second surface 100b. Similarly, the plurality of exit-side reflecting surfaces 102a to 102e are perpendicular to the third surface 100e and the fourth surface 100f, are inclined with respect to the first surface 100a and the second surface 100b, and are parallel to each other. . The incident side reflection surface 101 is a total reflection surface, and the emission side reflection surfaces 102a to 102c are partial reflection surfaces having a predetermined reflectance.

The light guide 10 is different from the light guide 20 in the conventional image display apparatus 2 in that the third surface 100e and the fourth surface 100f are considerably larger than the distance between the first surface 100a and the second surface 100b. Are both non-reflective surfaces. Here, in order to make the third surface 100e and the fourth surface 100f non-reflective surfaces, a coating layer in which an antireflection coating is applied to the surface of the substrate 100 (interface with the outside world) with a predetermined thickness is formed. However, the method of using a non-reflective surface is not limited to this. For example, the surface of the substrate 100 may be polished to form fine irregularities, and light reaching the surface may be scattered. Here, the “non-reflective surface” may be a surface that has a reflectivity reduced to such an extent that it can be regarded that there is substantially no reflection even if it has no complete non-reflectivity.

In the image display device 1 of the present embodiment, the image light emitted from the display screen of the display element 12 upon receiving the illumination light from the light source unit 11 is made substantially parallel light by the collimating optical system 13 and passes through the second surface 100b. It is introduced into the light guide 10. Similar to the conventional image display device, the image light introduced from the collimating optical system 13 to the light guide 10 includes information on different parts of the two-dimensional image formed on the display surface of the display element 12. , A set of parallel light beams incident on the light guide 10 at different angles.

The image light is reflected by the incident-side reflecting surface 101 and then propagates through the substrate 100 while being totally reflected one or more times by the second surface 100b and the first surface 100a, and is the lowest reflecting side reflecting surface. 102a is reached. At this time, in the image light introduced into the light guide 10, a light beam derived from light emitted from the vicinity of the center of the display surface of the display element 12 is reflected by the incident-side reflection surface 101 and then the yz plane. Propagates along the y-axis. On the other hand, in the image light introduced into the light guide 10, the light beam derived from the light emitted from the position close to the end in the left-right direction (z-axis direction) on the display surface of the display element 12 is reflected on the incident-side reflection surface. After being reflected at 101, it propagates in the yz plane with a predetermined angle with respect to the y-axis (that is, obliquely upward). Therefore, a part of such image light hits the third surface 100e or the fourth surface 100f, but these surfaces are non-reflective surfaces. Therefore, the image light reaching the third surface 100e and the fourth surface 100f disappears without being reflected (strictly, they are absorbed or scattered). Therefore, image light that has hit the third surface 100e or the fourth surface 100f even once does not reach the subsequent exit-side reflecting surfaces 102a to 100e.

The exit-side reflecting surface 102a reflects a part of the reached light beam and transmits the rest. The transmitted light reaches the next exit-side reflecting surface 102b, a part of the light beam is reflected, and the rest is transmitted. The same applies to the exit-side reflecting surfaces 102c to 102e. Therefore, the light beams that have propagated inside the substrate 100 of the light guide 10 are respectively reflected by the plurality of exit-side reflecting surfaces 102a to 102e, pass through the first surface 100a of the substrate 100, and exit to the outside. As described above, since the reflected light from the third surface 100e and the fourth surface 100f of the substrate 100 hardly reaches the exit-side reflection surfaces 102a to 102e, it is reflected by the exit-side reflection surfaces 102a to 102e and passes through the first surface 100a. The image light emitted to the outside of the light guide 10 contains almost no reflected light from the third surface 100e and the fourth surface 100f.

For example, in FIG. 2, the image light obtained at the position I on the light guide 10 is reflected by the position i on the incident-side reflection surface 101 and is emitted from the vicinity of the center of the display surface of the display element 12 [2 , And a light beam [3] emitted from the end of the display surface of the display element 12 that is reflected and arrived at the position ii on the incident-side reflection surface 101, unlike the conventional image display device, The light flux [3] emitted from the end of the display surface of the display element 12 that is reflected at the position i on the side reflection surface 101 and further reflected by the fourth surface 100f is not included. Therefore, an image whose left and right sides are reversed by reflection once is not superimposed. The same applies to the image light obtained at the position I on the light guide 10. For this reason, a ghost in which the left and right sides of the image are reversed is not superimposed on the virtual image seen from the observer's eye E. Thus, the image display apparatus 1 of the present embodiment can provide an observer with a highly visible image (virtual image).

The configuration of the light guide 10 in the image display apparatus of the above embodiment, specifically, the configuration of the incident portion and the emission portion in the present invention can be variously modified according to the configuration of the known light guide.
For example, as an incident part that guides image light into the substrate 100 of the light guide 10, as described in Non-Patent Document 1, for example, a part of the first surface 100 a of the substrate 100 of the light guide 10 is a first part. By making it non-parallel to the two surfaces 100b, it may be a reflective surface that reflects image light on the non-parallel surface (interface between the substrate 100 and the outside). Alternatively, a reflective volume hologram grating as described in Non-Patent Document 2 or Patent Document 2 may be used as the incident portion.
In addition, a reflective volume hologram grating may be used as an emitting unit that emits image light from the inside of the substrate 100 of the light guide 10 to the outside.
Further, the third surface 100e and the fourth surface 100f of the substrate 100 do not need to be parallel to each other. In addition, the third surface 100e and the fourth surface 100f do not need to be non-reflective surfaces as a whole. Regardless of the difference, the effects described above can be obtained.

Further, the present invention is not limited to the above-described embodiments and the above-described modifications, and any change, correction, or addition that is appropriately made within the scope of the present invention is naturally included in the scope of the claims of the present application.

DESCRIPTION OF SYMBOLS 1 ... Image display apparatus 10 ... Light guide 100 ... Board | substrate 100a ... 1st surface 100b ... 2nd surface 100e ... 3rd surface (non-reflective surface)
100f ... Fourth surface (non-reflective surface)
101: Incident-side reflecting surfaces 102a to 102e ... Emission-side reflecting surface 11 ... Light source unit 12 ... Display element 13 ... Collimating optical system

Claims

a) an image forming unit that emits image light including, as information, an image formed on the screen of the display element;
b) an incident optical system that collimates the image light from the image forming unit and enters the light guide, which will be described later,
c) a transparent substrate having first and second surfaces facing each other in parallel and a third surface and a fourth surface facing each other with a separation distance longer than the separation distance between the first surface and the second surface; An incident portion that guides the image light incident through the incident optical system to the inside of the substrate so as to be totally reflected by the first surface and the second surface, and is guided from the incident portion to the inside of the substrate. A light guide having an emission unit that emits image light propagated through the substrate while being totally reflected by the first surface and the second surface to the outside of the substrate at a predetermined position while expanding the light flux; ,
An image display device, wherein a part of at least one of the third surface and the fourth surface of the light guide is a non-reflecting surface.
The image display device according to claim 1,
The image display apparatus according to claim 1, wherein the non-reflective surface is a light shielding surface.
The image display device according to claim 2,
The image display device, wherein the light shielding surface is formed by applying an antireflection agent.
The image display device according to claim 1,
The non-reflective surface is a light scattering surface.
The image display device according to claim 4,
The image display device according to claim 1, wherein the light scattering surface is a surface subjected to processing for forming fine irregularities on the surface of the substrate.
The image display device according to any one of claims 1 to 5,
The incident portion is a reflecting surface formed inside the substrate and non-parallel to the first surface and the second surface,
The image display apparatus according to claim 1, wherein the emission unit is a plurality of partial reflection surfaces formed inside the substrate and not parallel to the first surface and the second surface.