JP7373984B2 - image display device - Google Patents

Description

The present invention relates to an image display device, and particularly to an image display device that superimposes and forms a plurality of images in the depth direction of space.

2. Description of the Related Art Conventionally, an instrument panel that displays illuminated icons has been used as a device for displaying various information in a vehicle. Additionally, as the amount of information to be displayed increases, it has also been proposed to embed an image display device in the instrument panel or to configure the entire instrument panel with an image display device.

However, since the instrument panel is located below the windshield of the vehicle, in order for the driver to visually check the information displayed on the instrument panel, the driver must move his line of sight downward while driving, which is not preferable. Therefore, a head-up display (hereinafter referred to as HUD) that projects an image onto the windshield so that the driver can read information when visually checking the front of the vehicle has also been proposed (for example, Patent Document 1 ). Such a HUD requires an optical device to project an image onto a wide area of the windshield, and it is desired that the optical device be made smaller and lighter.

On the other hand, as an image display device that projects light using a small optical device, a head-mounted HUD shaped like glasses is known (see, for example, Patent Document 2). A head-mounted HUD projects an image onto the viewer's retina by directly irradiating the viewer's eyes with light emitted from a light source.

Japanese Patent Application Publication No. 2018-118669 Special table 2018-528446 publication

However, conventional head-mounted HUDs use light-emitting diodes or organic EL elements as light sources to project images, and also use liquid crystal display devices to display images, so images formed in space (aerial images) are used. It was difficult to improve the amount of light. In particular, when an aerial image is superimposed against a background of real space, it is difficult to ensure the visibility of the image even in an environment illuminated by sunlight during the day.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide an image display device that can improve visibility by increasing the amount of light of an image formed in the depth direction. shall be.

In order to solve the above problems, an image display device of the present invention includes a light source unit that irradiates laser light, a part of the light irradiated by the light source unit is reflected in a first direction, and the remaining light is reflected in a second direction. a first beam splitter that transmits light in the first direction; a first imaging optical unit that forms an image in space of the light that has traveled in the first direction; and a second beam splitter that forms an image in space of the light that has traveled in the second direction. It is characterized in that it includes an imaging optical section , and one of the first imaging optical section and the second imaging optical section includes a head-mounted display .

In such an image display device of the present invention, the laser beam irradiated by the light source is split by the first beam splitter and imaged by the first imaging optical part and the second imaging optical part. It becomes possible to improve the visibility by increasing the amount of light of the image to be formed.

Further, in one aspect of the present invention, the other of the first imaging optical section and the second imaging optical section reflects a part of the light from the first beam splitter, and transmits the remaining light. The apparatus includes a two-beam splitter, a first retroreflector that retroreflects the light reflected by the second beam splitter, and a dichroic mirror that reflects the light reflected by the first retroreflector.

Further, in one aspect of the present invention, a second retroreflector is provided that retroreflects the light that has passed through the second beam splitter.

Further, in one aspect of the present invention, a first half mirror that splits the light emitted by the light source unit, and a first half mirror that reflects the light transmitted through the first half mirror toward the first surface of the first beam splitter are provided. The beam splitter includes a mirror and a second mirror that reflects the light reflected by the first half mirror toward the second surface of the first beam splitter.

According to the present invention, it is possible to provide an image display device that can improve visibility by increasing the amount of light of an image formed in the depth direction.

FIG. 1 is a schematic diagram showing the configuration of an image display device 100 according to a first embodiment. FIG. 6 is a schematic diagram illustrating the formation and visual recognition of a third image H using the first imaging optical section of the image display device 100. FIG. FIG. 2 is a schematic diagram illustrating formation and visual recognition of a first image A1 and a second image A2 using a second imaging optical section of the image display device 100. FIG. 2 is a photograph showing formation of an aerial image using the image display device 100. FIG. 2 is a schematic diagram showing the configuration of an image display device 110 according to a second embodiment. 2 is a photograph showing formation of an aerial image using the image display device 110.

(First embodiment)
Embodiments of the present invention will be described in detail below with reference to the drawings. Identical or equivalent constituent elements, members, and processes shown in each drawing are denoted by the same reference numerals, and redundant explanations will be omitted as appropriate. FIG. 1 is a schematic diagram showing the configuration of an image display device 100 according to this embodiment. As shown in FIG. 1, the image display device 100 includes a light source unit CW, lenses L1, L2, half mirrors HM1, HM2, mirrors M1, M2, M3, an aperture AP, a prism Pr, a beam splitter BS1, It includes a BS2, retroreflective parts RR1 and RR2, a dichroic mirror DM, and a head mounted display HMD.

In the image display device 100 shown in FIG. 1, the viewer visually recognizes the first image A1, the second image A2, and the third image H projected by the light emitted from the light source part CW at different distances in the depth direction. . In FIG. 1, the depth direction is the direction in which the first image A1, second image A2, and third image H are lined up, the vertical direction is the vertical direction perpendicular to the depth direction, and the horizontal direction is the direction perpendicular to the depth direction. direction.

The light source unit CW is a device that emits laser light of a predetermined wavelength, and for example, a semiconductor laser device including a semiconductor laser element and a control circuit can be used. The laser light irradiated from the light source part CW is not limited as long as it has a wavelength in the visible light range, but it is preferably red, blue, or green. Moreover, the light emitted from the light source part CW may be monochromatic, or may be a mixture of a plurality of colors. Alternatively, red, blue, and green light may be emitted in a time-division manner. Further, the light emitted by the light source unit CW may be continuous light or pulsed light. Further, the light source section CW may include a collimator lens and other optical elements. The light emitted by the light source unit CW can be emitted as light including a predetermined image by using a liquid crystal display element or a DMD (Digital Mirror Device).

The lenses L1 and L2 are optical elements that are arranged in the path of the laser light emitted from the light source part CW and condense and expand the laser light. In the example shown in FIG. 1, the lens L1 is arranged between the light source section CW and the half mirror HM1, and the lens L2 is arranged between the mirror M3 and the prism Pr. Here, an example using two lenses L1 and L2 is shown, but as will be described later, in order to adjust the positions of the first image A1, second image A2, and third image H formed in the air, , other lenses may be added to any of the optical paths as necessary.

The half mirrors HM1 and HM2 are approximately flat optical elements that reflect part of the light incident on one surface and transmit the remaining part, and are arranged at an angle of 45 degrees with respect to the vertical direction and the depth direction. It is arranged so that Although the reflectance and transmittance of the half mirrors HM1 and HM2 are not limited, for example, one that reflects 50% and transmits 50% can be used. The mirrors M1, M2, and M3 are substantially flat optical elements that reflect light incident on the reflecting surface, and are arranged at an angle of 45 degrees with respect to the vertical direction and the depth direction.

The aperture AP is an optical element that transmits only light that has reached a limited area and limits the irradiation area of the light. In the example shown in FIG. 1, the aperture AP is arranged between the lens L2 and the prism Pr, and limits the diameter of the light transmitted through the lens L2 and focused, and makes it enter the light incidence surface of the prism Pr. . The prism Pr is an optical element for introducing light into the light guide of the head mounted display HMD.

In the example shown in FIG. 1, the laser beam irradiated from the light source part CW enters the half mirror HM1 through the lens L1, a part of which is transmitted and travels in the direction of the mirror M1, and the remaining part is reflected and is reflected by the mirror M2. proceed in the direction. The light incident on the mirror M1 is reflected by the reflecting surface and enters one surface of the beam splitter BS1. The light incident on the mirror M2 is reflected by the reflecting surface and enters the other surface of the beam splitter BS1.

The beam splitter BS1 is a member that transmits part of the incident light and reflects part of it, and can use a partial reflection plate on the surface of which a film for adjusting reflectance is formed. The beam splitter BS1 is arranged at an angle of 45 degrees with respect to the vertical direction and the depth direction. Further, the mirrors M1 and M2 are arranged at an angle of 45 degrees with respect to the optical axis of light incident on one surface and the other surface. Beam splitter BS1 corresponds to the first beam splitter in the present invention.

The head mounted display HMD is an image projection unit that forms the third image H in space. The specific configuration of the head-mounted display HMD is not limited, and known configurations such as one that uses a light guide plate and a diffraction grating, or one that scans a laser beam on the retina can be used. In the example shown in FIG. 1, the head mounted display HMD includes a flat light guide plate and a half mirror HM2 formed within the light guide plate, and the light incident from the prism Pr propagates inside the light guide plate. It is reflected by the half mirror HM2 in the direction of the viewer's viewpoint. As will be described later, since the third image H is formed in space by the light reflected by the half mirror HM2 of the head mounted display HMD, the mirror M3, the lens L2, the aperture AP, the prism Pr, The head mounted display HMD constitutes the first imaging optical section in the present invention.

The beam splitter BS2 is a member that transmits part of the incident light and reflects part of it, and can use a partial reflection plate on the surface of which a film for adjusting reflectance is formed. The beam splitter BS2 is arranged at an angle of 45 degrees with respect to the vertical direction and the depth direction. Further, it is also arranged at an angle of 45 degrees with respect to the optical axis of the light incident from the beam splitter BS1. Furthermore, the inclination directions of the beam splitter BS2 and the beam splitter BS1 are opposite to each other, and they are arranged to face each other so as to intersect at an angle of 90 degrees. Beam splitter BS2 corresponds to the second beam splitter in the present invention.

Here, an arbitrary balance can be selected for the light transmittance and reflectance of the beam splitters BS1 and BS2, but for example, the transmittance is set to 50% and the reflectance is set to 50%. Furthermore, although an example has been shown in which the inclination angles of the beam splitters BS1 and BS2 are 45 degrees orthogonal, any appropriate angle can be used depending on the relationship between the traveling direction of the laser beam and the imaging position of the image.

The retroreflectors RR1 and RR2 are optical members that reflect the incident light while maintaining condensation in the direction of incidence, and use a structure in which minute glass beads are spread on the surface side of the reflective film or a prism. Retroreflective portions of the structure can be used. The retroreflector RR1 is arranged below the beam splitter BS2, and its main surface is in the horizontal direction. The retroreflector RR2 is arranged in the depth direction along with the beam splitters BS1 and BS2, and its main surface is in the vertical direction.

The dichroic mirror DM is an optical member that reflects the wavelength of the laser light emitted by the light source CW and transmits light of other wavelengths. The dichroic mirror DM is arranged above the retroreflector RR1 and the beam splitter BS2, and is arranged at an angle of 45 degrees in the depth direction. As will be described later, since the first image A1 and the second image A2 are formed in space by the light reflected by the dichroic mirror DM, the beam splitter BS2, the retroreflectors RR1 and RR2, and the dichroic mirror DM constitutes the second imaging optical section in the present invention.

Although not shown in FIG. 1, an imaging lens may be disposed between the beam splitter BS2 and the dichroic mirror DM as part of the imaging optical system. The imaging lens is an optical member for focusing the light transmitted through the beam splitter BS2 on a predetermined position in space, and a plurality of lens groups may be used. Further, the first image A1, the second image A2, and the third image H formed in space by the laser light emitted by the light source unit CW may be still images or moving images, and the images projected by each are the same. may be different.

FIG. 2 is a schematic diagram illustrating the formation and visual recognition of the third image H using the first imaging optical section of the image display device 100. A portion of the light incident on one surface of the beam splitter BS1 passes through the beam splitter BS1 and reaches the mirror M3. Further, a part of the light incident on the other surface of the beam splitter BS1 is reflected by the beam splitter BS1 and reaches the mirror M3. The light reaching the mirror M3 is reflected by the reflecting surface and enters the prism Pr via the lens L2 and the aperture AP. The light incident on the prism Pr travels through the prism Pr and the light guide plate of the head mounted display HMD, reaches the half mirror HM2, and is reflected by the half mirror HM2 and enters the viewer's field of view.

Here, by appropriately designing the shape of the half mirror HM2, the light traveling from the half mirror HM2 in the viewer's viewing direction becomes an optical path that expands in the viewer's direction as shown by the broken line in FIG. . Therefore, the viewer visually recognizes the third image H at the spatial imaging position on the extension of the optical path. Further, since the head mounted display HMD and the half mirror HM2 are made of a translucent material, the background in the direction of the line of sight can also be visually recognized.

FIG. 3 is a schematic diagram illustrating the formation and visual recognition of the first image A1 and the second image A2 using the second imaging optical section of the image display device 100. A portion of the light incident on one surface of the beam splitter BS1 is reflected by the beam splitter BS1 and reaches the beam splitter BS2. Further, a part of the light incident on the other surface of the beam splitter BS1 passes through the beam splitter BS1 and reaches the beam splitter BS2.

A portion of the light that has reached the beam splitter BS2 is reflected and travels in the direction of the retroreflector RR1, is re-reflected by the retroreflector RR1, and enters the beam splitter BS2 again. The light that has entered the beam splitter BS2 again passes through the beam splitter BS2, is reflected by the dichroic mirror DM, and is formed into a first image A1 and a second image A2. The light formed as the first image A1 and the second image A2 passes through the head mounted display HMD and reaches the viewer's eyes. Therefore, the viewer visually recognizes the first image A1 and the second image A2 in the air in the depth direction.

The remaining part of the light that has reached the beam splitter BS2 is transmitted and proceeds in the direction of the retroreflector RR2, is re-reflected by the retroreflector RR2, and enters the beam splitter BS2 again. The light re-entering the beam splitter BS2 is reflected by the beam splitter BS2, and then reflected by the dichroic mirror DM to form a first image A1 and a second image A2.

As shown in FIG. 3, by using the retroreflector RR1 and the retroreflector RR2, the light retroreflected by the retroreflector RR2 is also reflected by the beam splitter BS2, reaches the dichroic mirror DM, and reaches the first dichroic mirror DM. The images are formed as an image A1 and a second image A2. Therefore, since the light transmitted through the beam splitter BS2 and the light reflected are used to form the first image A1 and the second image A2, a decrease in the amount of light is suppressed.

At this time, the light retroreflected by the retroreflector RR1 and the light retroreflected by the retroreflector RR2 are images with the same content split by the beam splitter BS2, and are superimposed on each other and reach the dichroic mirror DM. There is a need to. Therefore, when the optical characteristics of the retroreflective part RR1 and the retroreflective part RR2 are the same, it is preferable to make the distances of the beam splitter BS2 from the retroreflective part RR1 and the retroreflective part RR2 equal.

In FIG. 1, the path of the light reflected by the mirror M1 is shown by a dashed line, and the path of the light reflected by the mirror M2 is shown by a broken line. If the magnification of one of the lights is changed by inserting a separate lens into the path of these lights, the imaging positions of the first image A1 and the second image A2 will be different, as shown in FIGS. 1 and 2. can be set.

As described above, the viewer is aware that the light that forms the first image A1, the second image A2, and the third image H is incident on the viewing range of the same viewer, and the first distance is at a different position in the depth direction. , a first image A1, a second image A2, and a third image H can be visually recognized at a second distance and a third distance. At the same time, the viewer can view the background that passes through the dichroic mirror DM and the head-mounted display HMD and reaches the viewer's eyes. Therefore, the viewer visually recognizes an aerial image in which the first image A1, the second image A2, and the third image H are superimposed on the background.

FIG. 4 is a photograph showing the formation of an aerial image using the image display device 100. The photograph in FIG. 4 is taken from the viewer's viewpoint in FIG. 1 in the direction of the head-mounted display HMD and the dichroic mirror DM, and shows the viewer's viewing range as an image. The x-axis direction, y-axis direction, and z-axis direction in FIG. 4 indicate the horizontal direction, vertical direction, and depth direction in FIG. 1.

In the example shown in FIG. 4, a circular image is emitted from the light source CW, and a first image A1 is formed at a first distance in the depth direction from the viewer, and a second image A2 is formed at a second distance. Then, a third image H was formed at a third distance. The circle with a diameter of about 2 mm indicated by the triangular arrow A in the figure is the image of the second image A2, and the circle with a diameter of about 0.75 mm indicated by the triangular arrow B is the image of the first image A1. A circle with a diameter of 0.5 mm indicated by an arrow * is the image of the third image H. In the background in Figure 4, each part of the measuring device used in the experiment is visible, and even if the first image A1, second image A2, and third image H, which are aerial images, are superimposed on the background. It was confirmed that both the background and the aerial image could be clearly seen.

As shown in FIG. 4, in the image display device 100 of this embodiment, the laser light emitted by one light source part CW is split by the first beam splitter BS1, and the laser light is split between the first imaging optical part and the second imaging part. Since the image is formed in the optical section, it is possible to improve the amount of light of the image formed in the depth direction, thereby improving visibility.

(Second embodiment)
Next, a second embodiment of the present invention will be described using FIGS. 5 and 6. Description of contents that overlap with those of the first embodiment will be omitted. FIG. 5 is a schematic diagram showing the configuration of the image display device 110 according to this embodiment. The image display device 110 of this embodiment differs from the first embodiment in that a half mirror HM3 is arranged between the half mirror HM3 and the mirror M1, and a beam splitter BS3 is arranged between the mirror M2 and the beam splitter BS1. There is. As shown in FIG. 5, the image display device 110 includes a light source unit CW, lenses L1, L2, half mirrors HM1, HM2, HM3, mirrors M1, M2, M3, an aperture AP, a prism Pr, and a beam splitter. It includes BS1, BS2, BS3, retroreflective parts RR1, RR2, a dichroic mirror DM, and a head mounted display HMD.

As shown in FIG. 5, the laser beam irradiated from the light source part CW enters the half mirror HM1 through the lens L1, a part of which is transmitted and travels in the direction of the half mirror HM3, and the remaining part is reflected and is reflected by the mirror HM1. Proceed in the M2 direction. A part of the light incident on the half mirror HM3 is transmitted and travels in the direction of the mirror M1, and the rest is reflected and enters one surface of the beam splitter BS3. The light incident on the mirror M1 is reflected by the reflecting surface and enters one surface of the beam splitter BS1.

The light incident on mirror M2 is reflected by the reflective surface, reaches the other surface of beam splitter BS3, passes through beam splitter BS3, and enters the other surface of beam splitter BS1. Light incident on one surface of beam splitter BS3 is also reflected by beam splitter BS3 and incident on the other surface of beam splitter BS1. The light incident on one surface and the other surface of the beam splitter BS1 is imaged as an aerial image by the first imaging optical section and the second imaging optical section as in the first embodiment.

In the image display device 110 of this embodiment, the laser light transmitted through the half mirror HM1 is further split by the half mirror HM3 and reaches the beam splitter BS2 via the beam splitter BS3, so that the laser light is reflected by the dichroic mirror DM. A fourth image A4 different from the first image A1 and the second image A2 is formed in space. Further, similarly to the first embodiment, an optical element such as a lens may be appropriately disposed between the half mirror HM3 and the beam splitter BS3 to adjust the imaging position of the fourth image A4.

As described above, the viewer is aware that the light that forms the first image A1, the second image A2, the third image H, and the fourth image A4 is incident on the same viewer's field of view and at different positions in the depth direction. The first image A1, the second image A2, the third image H, and the fourth image A4 can be visually recognized at the first distance, the second distance, the third distance, and the fourth distance. At the same time, the viewer can view the background that passes through the dichroic mirror DM and the head-mounted display HMD and reaches the viewer's eyes. Therefore, the viewer visually recognizes an aerial image in which the first image A1, second image A2, third image H, and fourth image A4 are superimposed on the background.

FIG. 6 is a photograph showing the formation of an aerial image using the image display device 110. The photograph in FIG. 6 is taken in the direction of the head-mounted display HMD and the dichroic mirror DM from the viewer's viewpoint in FIG. 5, and shows the viewing range of the viewer as an image.

In the example shown in FIG. 6, a circular image is emitted from the light source CW, and a first image A1 is formed at a first distance in the depth direction from the viewer, and a second image A2 is formed at a second distance. Then, a third image H was formed at a third distance, and a fourth image A4 was formed at a fourth distance. A circle with a diameter of about 1 mm indicated by a triangular arrow C in the figure is the image of the fourth image A4. In addition to the first image A1, second image A2, and third image H shown in FIG. 4, it was confirmed that the fourth image A4 was formed as an aerial image superimposed on the background and could be visually recognized.

In the example shown in FIGS. 5 and 6, only one set of half mirror HM3 and beam splitter BS3 is added to the laser beam path to form the fourth image A4, but many more half mirrors and beam splitters are added. The number of aerial images to be formed may be increased by arranging . Furthermore, the positions where the half mirror and beam splitter are arranged are not limited to those shown in FIG. 5 as long as they are on the path of the laser beam.

As described above, in the image display device 110 of this embodiment as well, the laser light emitted by one light source section CW is split by the first beam splitter BS1, and split between the first imaging optical section and the second imaging optical section. Since the image is formed, it is possible to improve the amount of light of the image formed in the depth direction, thereby improving visibility.

The present invention is not limited to the embodiments described above, and various modifications can be made within the scope of the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. are also included within the technical scope of the present invention.

100, 110...Image display device L1, L2...Lens RR1, RR2...Retroreflector HM1, HM2, HM3...Half mirror BS1, BS2, BS3...Beam splitter M1, M2, M3...Mirror A1...First image A2...First image 2nd image H...3rd image A4...4th image

Claims (4)

a light source unit that irradiates laser light;
a first beam splitter that reflects part of the light emitted by the light source in a first direction and transmits the remaining light in a second direction;
a first imaging optical section that images the light traveling in the first direction in space;
comprising a second imaging optical section that images the light traveling in the second direction in space ;
An image display device , wherein one of the first imaging optical section and the second imaging optical section includes a head-mounted display . The image display device according to claim 1 ,
The other of the first imaging optical section or the second imaging optical section,
a second beam splitter that reflects part of the light from the first beam splitter and transmits the remaining light;
a first retroreflector that retroreflects the light reflected by the second beam splitter;
An image display device comprising a dichroic mirror that reflects light reflected by the first retroreflection section. The image display device according to claim 2 ,
An image display device comprising: a second retroreflection section that retroreflects light transmitted through the second beam splitter. The image display device according to any one of claims 1 to 3 ,
a first half mirror that branches the light emitted by the light source;
a first mirror that reflects the light transmitted through the first half mirror toward a first surface of the first beam splitter;
An image display device comprising: a second mirror that reflects light reflected by the first half mirror toward a second surface of the first beam splitter.