JP2022129523A - Image projector - Google Patents

Abstract

To provide an image projection device that can project a plurality of images to different positions distant differently from a point of view and can reduce the size and the weight.SOLUTION: The image projector includes: a first image irradiation unit (40) for applying a first light; a first light entering unit (22) to which the first light enters; an optical waveguide unit (21) for guiding a part of the first light as waveguide light while total-reflecting the light; a light guide plate unit (20) having a first light emission unit for emitting a part of the waveguide light in the direction of the point of view; and a diffraction grating unit (10) provided in the first light entering unit (22). The first light emission unit has a beam splitter (23) in the light waveguide unit (21) and a retroreflection unit (24) in an edge of the light waveguide unit (21).SELECTED DRAWING: Figure 2

Description

The present invention relates to an image projection device, and more particularly to an image projection device using a diffraction grating.

2. Description of the Related Art Conventionally, as a device for displaying various types of information in a vehicle, a dashboard that displays icons by lighting has been used. In addition, as the amount of information to be displayed increases, it has 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, it is not preferable for the driver to view the information displayed on the instrument panel by moving the line of sight downward during driving. Therefore, a head-up display (hereinafter referred to as HUD: Head Up Display) has been proposed that projects an image onto the windshield so that the driver can read information when looking ahead of the vehicle (for example, Patent Document 1). ). Such a HUD requires an optical device for projecting an image over a wide area of the windshield, and it is desired to reduce the size and weight of the optical device.

On the other hand, as an image display device that projects light using a small optical device, there is known a wearable HUD that allows light to enter from one end of a light guide plate and extract light from the other end in the viewing direction ( For example, see Patent Document 2). A wearable HUD projects an image onto the viewer's retina by directly irradiating the viewer's eye with light emitted from a light source. Such a wearable HUD uses a diffraction grating or a half mirror to irradiate the viewer with light from the light source. Wearable HUDs project images from the user's point of view when worn on the head, so they can be used in highly immersive virtual reality (VR) and augmented reality (AR). Used.

JP 2019-119262 A JP 2020-144190 A

However, in a conventional wearable HUD, images are projected in the direction of the viewpoint from the light guide plate using a diffraction grating or a half mirror, so all images are displayed on a plane at the same distance from the viewpoint. Therefore, it has been difficult to display and superimpose a plurality of images at different distances from viewpoints. In addition, in order to project multiple images at different distances from the viewpoint, it is necessary to design and arrange the image projection unit and optical system members corresponding to the projection positions individually, which increases the number of parts. There is a problem that it becomes difficult to reduce the size and weight of the device.

SUMMARY OF THE INVENTION Accordingly, the present invention has been devised in view of the conventional problems described above, and provides an image projection apparatus capable of projecting a plurality of images at positions at different distances from the viewpoint, and furthermore capable of achieving reductions in size and weight. intended to

In order to solve the above problems, the image projection device of the present invention includes: a first image irradiation section that irradiates a first light; a first light incidence section that receives the first light; a light guide plate portion that guides as guided light while totally reflecting a portion; a light guide plate portion that has a first light emitting portion that emits part of the guided light in a direction of a viewpoint; and the first light emitting section includes a beam splitter provided in the optical waveguide section and a retroreflective section provided at an end of the optical waveguide section.

In such an image projection apparatus of the present invention, the beam splitter splits the first light to project an image on the screen, and the first light is retroreflected by the retroreflector at the end of the optical waveguide, and the beam splitter can form an aerial image by projecting it in the direction of the viewpoint. As a result, it is possible to project a plurality of images at positions with different distances from the viewpoint, and to further reduce the size and weight.

In one aspect of the present invention, the light guide plate portion includes a second light emitting portion that transmits one of the lights split by the diffraction grating portion and emits the light in an external screen direction different from the viewpoint direction. .

Moreover, in one aspect of the present invention, the viewpoint direction and the external screen direction are substantially parallel.

In one aspect of the present invention, an optical shutter section that switches between transmission and blocking of light is provided in the first light emission section or the second light emission section.

Further, in one aspect of the present invention, a wavelength converting section that converts the wavelength of the first light is provided in the first light emitting section or the second light emitting section.

In one aspect of the present invention, the retroreflective portion is formed by a mixture of specular reflection areas that specularly reflect light and retroreflective areas that retroreflect light.

In one aspect of the present invention, a partial reflection section that reflects part of the waveguided light and transmits the rest is provided between the beam splitter and the retroreflection section.

Further, in one aspect of the present invention, a second image irradiation unit that irradiates the diffraction grating with a second light is provided, and the incident angles of the first light and the second light with respect to the diffraction grating are different. , the optical waveguide portion guides a portion of the second light as guided light while totally reflecting the portion of the second light.

In one aspect of the present invention, a selective reflection section that reflects the wavelength of the first light and transmits the wavelength of the second light is provided between the beam splitter and the retroreflection section.

In one aspect of the present invention, an optical filter that selectively blocks the wavelength of the first light or the wavelength of the second light is provided in the second light emitting section.

Moreover, in one aspect of the present invention, the optical waveguide section has a curved shape.

Moreover, in one aspect of the present invention, the first image irradiation section includes a liquid crystal display element or a digital mirror device, and temporally changes the content of the first image included in the first light.

In one aspect of the present invention, two light guide plate portions are provided, and one diffraction grating portion is provided in common to each of the first light incident portions of the light guide plate portions.

Further, in one aspect of the present invention, the diffraction grating section includes a flat plate-shaped portion forming a light incident surface, and an uneven portion formed integrally with the flat plate-shaped portion. formed.

In one aspect of the invention, the diffraction grating section has a holographic grating that diffracts light in at least two directions.

According to the present invention, it is possible to provide an image projection device that projects a plurality of images at positions at different distances from the viewpoint and that can be made smaller and lighter.

2 is a schematic cross-sectional view showing the structure of a diffraction grating section 10 according to the first embodiment; FIG. 1 is a schematic diagram showing the structure of an image projection device according to a first embodiment; FIG. FIG. 2 is a schematic cross-sectional view showing an enlarged first light emitting portion of the image projection device according to the first embodiment; A camera is installed at the position of the viewpoint 60, and the image EX projected on the external screen 30 and the aerial image A1 formed in the air are photographed. FIG. , and FIG. 4(b) is a view in which the camera is focused on the imaging position of the aerial image A1. FIG. 11 is a schematic cross-sectional view showing an enlarged first light emitting portion of the image projection device according to the second embodiment; 6A is a photograph of an image EX and an image V1 projected on the external screen 30 and an aerial image A1 formed in the air by a camera installed at the position of the viewpoint 60. FIG. , and FIG. 6B shows the camera focused on the imaging position of the aerial image A1. FIG. 11 is a schematic diagram showing the structure of an image projection device according to a third embodiment; FIG. 11 is a schematic cross-sectional view showing an enlarged first light emitting portion of an image projection device according to a third embodiment; 9A is a photograph of an image EX and an image V1 projected onto an external screen 30 and aerial images A1 and A2 formed in the air by installing a camera at the position of the viewpoint 60, and FIG. 9A is the aerial image A1. The camera is focused on the imaging position of the aerial image A2, FIG. 9(b) is the camera focused on the imaging position of the aerial image A2, and FIG. . Fig. 10(a) is a photograph focused from the viewpoint 60, and Figs. 10(b) and 10(c) are three-dimensional brightness profiles at imaging positions. , FIG. 10(d) is the luminance profile in the x direction and FIG. 10(e) is the luminance profile in the y direction. FIG. 11 is a schematic diagram showing the structure of an image projection device according to a fourth embodiment; FIG. 11 is a schematic diagram showing the structure of an image projection device according to a modification of the fourth embodiment; FIG. 11 is a schematic diagram showing the structure of an image projection device according to a fifth embodiment; FIG. 12 is a schematic diagram showing the structure of an image projection device according to a modification of the fifth embodiment; FIG. 11 is a schematic diagram showing a structural example of a retroreflective portion 24 in a sixth embodiment;

(First embodiment)
BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The same or equivalent constituent elements, members, and processes shown in each drawing are denoted by the same reference numerals, and duplication of description will be omitted as appropriate. FIG. 1 is a schematic cross-sectional view showing the structure of the diffraction grating section 10 in this embodiment. As shown in FIG. 1 , the diffraction grating section 10 includes a plate-like portion 11 , convex portions 12 and concave portions 13 . Here, the convex portions 12 and the concave portions 13 are portions of the diffraction grating portion 10 that form periodic repetitions of the refractive index in the in-plane direction, and correspond to the uneven portions in the present invention. The plate-like portion 11 and the convex portion 12 are integrally formed of the same material. 1 schematically shows the structure of the diffraction grating section 10, and the dimensions and angles in the drawing do not represent the actual dimensions of the diffraction grating section 10. FIG.

In the example shown in FIG. 1, the convex portions 12 and the concave portions of the diffraction grating portion 10 are each formed to extend in a stripe shape in the depth direction of the paper surface. The convex portion 12 is formed to be inclined by a predetermined angle φ with respect to the main surface of the flat plate portion 11, and constitutes a slant grating. Moreover, the convex portion 12 and the concave portion 13 are covered with a covering portion made of a material having a different refractive index from that of the flat plate portion 11 . The material constituting the diffraction grating section 10 is not limited, but as an example, a dielectric material having a refractive index of about 2.5 and having TiO ₂ as a main component can be mentioned as a material constituting the plate-shaped section 11 and the convex section 12. Glass or polymer containing SiO ₂ as a main component can be used as the covering portion that covers the convex portion 12 and the concave portion 13 .

The concave-convex portion of the diffraction grating section 10 can be formed by a known method, such as photolithography technology, nanoimprint technology, EBL (Electron Beam Lithography) technology, or the like. Further, by holding the covering portion in a tilted state and using a reactive ion etching (RIE) method or the like, the convex portion 12 and the concave portion 13 can be formed by tilting at an angle φ. At this time, the inclination angle φ of the protrusions 12 and the recesses 13 is the angle formed between the main surface of the diffraction grating section 10 and the line connecting the center of the upper end and the lower end of the protrusions 12 . Although FIG. 1 shows a slant grating in which the convex portions 12 and the concave portions 13 are inclined as the uneven portion of the diffraction grating portion 10, it may be a pillar grating perpendicular to the main surface.

Next, optical paths in the diffraction grating section 10 will be described with reference to FIG. Although FIG. 1 schematically shows the progress of light in the diffraction grating section 10 using arrows, it does not reflect the exact incident position, travel path, and exit position of the light. A laser beam is irradiated toward the diffraction grating section 10 from a light source section (not shown). Here, the laser light is coherent light with the same phase, and is irradiated as collimated light by a collimating lens or the like. Incident light emitted from the light source portion enters the flat portion 11 at a predetermined inclination angle from the interface of the diffraction grating portion 10 .

Here, the polarization direction of the incident light is parallel to the stripes of the projections 12 . FIG. 1 shows an example in which the inclination angle of incident light and the inclination direction φ of the convex portions 12 and the concave portions 13 in the diffraction grating section 10 are the same direction, but they may be opposite directions. A portion of the light incident on the diffraction grating portion 10 travels outward as diffracted light at a predetermined angle due to the periodic refractive index difference between the convex portions 12 and the concave portions 13, and a portion of the light propagates through the plate-like portion as propagating light. 11 as leak propagation light. Leakage light propagating in the flat plate portion 11 is reflected at the interface with the air, reaches the uneven portion again, and is diffracted by the convex portions 12 and the concave portions 13 .

In the example shown in FIG. 1, of the light diffracted by the diffraction grating section 10, the 0th order light T1 is transmitted through the covering section and irradiated to the outside. In addition, the first-order light (−1st-order light T2) diffracted in the direction in which the convex portion 12 is inclined also passes through the covering portion and is irradiated to the outside. This is because the 0th-order light T1 and the -1st-order light T2 are diffracted at an angle nearly perpendicular to the main surface of the diffraction grating section 10, and therefore do not satisfy the conditions for total reflection at the interface between the covering section and the air layer. is.

The first-order light (+1st-order light I1) diffracted in the direction opposite to the inclination of the convex portion 12 is totally reflected by the interface between the covering portion and the air layer and propagates through the covering portion. Similarly, the secondary light (-2nd order light I2) diffracted in the direction in which the convex portion 12 is inclined is also totally reflected by the interface between the covering portion and the air layer and propagates through the covering portion. The conditions for total reflection at the interface between the covering portion and the air layer are determined by the refractive index of the material forming the covering portion. The +1st-order light I1 and the −2nd-order light I2 that have propagated through total reflection within the covering portion are irradiated to the outside from the ends of the covering portion. At this time, the 0th-order light T1, −1st-order light T2, +1st-order light I1, and −2nd-order light I2 are light beams diffracted by the convex portion 12 and the concave portion 13, and therefore travel while the light diameter is slightly expanded. .

FIG. 2 is a schematic diagram showing the structure of the image projection device according to this embodiment. As shown in FIG. 2, the image projection apparatus includes a diffraction grating section 10, a light guide plate section 20, an external screen 30, and image irradiation sections 40 and 50. As shown in FIG. A viewer wearing the image projection device views the direction of the light guide plate 20 and the external screen 30 from the position of the viewpoint 60 . As shown in FIG. 1, the diffraction grating section 10 is an optical element including a flat plate portion 11, convex portions 12, concave portions 13, and a covering portion, and is formed separately from the light guide plate portion 20. FIG. The light guide plate portion 20 is a plate-like member made of a translucent material, and includes an optical waveguide portion 21 , a light incidence portion 22 , a beam splitter 23 and a retroreflection portion 24 .

The optical waveguide part 21 is a plate-shaped member made of a translucent material, and waveguides light from one end side to the other end side by repeating total reflection of light at the interface with the air. In addition, since the optical waveguide 21 transmits light from one surface side to the other surface side, it is possible to visually recognize the direction of the external screen 30 from the viewpoint 60 through the optical waveguide 21 . A light incident portion 22, which is a surface inclined with respect to the main surface, is formed on one end side of the optical waveguide portion 21, and the diffraction grating portion 10 is arranged thereon. On the other end side of the optical waveguide portion 21, an end face is formed and a retroreflective portion 24 is provided. In FIG. 1, the optical waveguide portion 21 has a flat plate shape, but it may have a curved surface shape as long as the light can be propagated by total internal reflection.

The light incident portion 22 is an inclined surface formed at one end of the optical waveguide portion 21, is arranged adjacent to the diffraction grating portion 10, and corresponds to the first light incident portion in the present invention. The light entrance section 22 may be provided with an antireflection film or a refractive index adjustment section in order to increase the optical coupling ratio with the diffraction grating section 10 .

The beam splitter 23 is an optical element that reflects part of the light incident from one surface and transmits the rest. In the example shown in FIG. is formed as A specific configuration of the beam splitter 23 is not limited, and a known structure and design method can be used.

The retroreflector 24 is an optical member that reflects incident light while maintaining convergence in the direction of incidence. A retroreflective portion can be used. When the light propagated through the optical waveguide portion 21 is incident on the retroreflecting portion 24, the light is reflected in the direction in which the light is incident. reflected as

As will be described later, the area between the area where the beam splitter 23 is provided and the end where the retroreflecting section 24 is provided in the optical waveguide section 21 is an area where the light propagating in the optical waveguide section 21 is irradiated to the outside. and constitutes the first light emitting portion in the present invention.

The external screen 30 is a portion for displaying an image by projecting light emitted from the light guide plate portion 20 as will be described later. The material constituting the external screen 30 is not limited, and a translucent material that transmits light may be used, or a white material that blocks and reflects light may be used. When a translucent material is used, images can be superimposed and projected using the external environment of the image projection apparatus as a background. In the example shown in FIG. 1, the external screen 30 and the arm portion are integrally formed, and the arm portion is fixed to the light guide plate portion 20, thereby maintaining the relative positional relationship between the external screen 30 and the light guide plate portion 20. As an example, the external screen 30 may be provided separately from the image projection device.

The image irradiation section 40 is a device that irradiates the diffraction grating section 10 with the first light for projecting the first image, and corresponds to the first image irradiation section in the present invention. Although the specific configuration of the image irradiation section 40 is not limited, in the example shown in FIG. The image irradiation unit 40 irradiates the diffraction grating unit 10 with light through mirrors 45 , 46 , 47 and a bandpass filter 48 . The light source unit 41 preferably uses a laser light source, and irradiates an image forming unit (not shown) with laser light emitted from the light source unit 41 to include the first image in the first light. The image forming section can be a known device such as a liquid crystal display element or a digital mirror device, and may be provided inside the image irradiation section 40 or may be arranged on the optical path to the diffraction grating section 10 . By equipping the image irradiation unit 40 with a liquid crystal display element or a digital mirror device, which is an image forming unit, it is possible to change the content of the first image included in the first light over time and project a moving image. .

The image irradiation section 50 is a device that irradiates the diffraction grating section 10 with the second light for projecting the second image, and corresponds to the second image irradiation section in the present invention. The image irradiation section 50 is provided separately from the image irradiation section 40 , and the incident angle of the second light with respect to the diffraction grating section 10 is different from the incident angle of the first light irradiated by the image irradiation section 40 . The specific configuration of the image irradiation unit 50 is not limited, and the same configuration as that of the image irradiation unit 40 can be used, but the wavelengths of the first light and the second light are different.

Next, image projection in the image projection apparatus of this embodiment will be described with reference to FIGS. 2 and 3. FIG. FIG. 3 is a schematic cross-sectional view showing an enlarged first light emitting portion of the image projection device according to the present embodiment. Solid-line arrows and dashed-line arrows shown in the figure schematically indicate paths of light.

The first light irradiated from the image irradiation section 40 is reflected by the mirrors 45 , 46 and 47 and reaches the diffraction grating section 10 via the bandpass filter 48 . In the diffraction grating section 10 , 0th-order light T 1 and +1st-order light I 1 are extracted as diffracted light according to the incident angle of the first light, and enter the light incident section 22 . The first light incident on the light incident portion 22 from the diffraction grating portion 10 is totally reflected in the optical waveguide portion 21 and propagates as guided light. Here, since the incident angle of the first light incident on the light incident portion 22 from the diffraction grating portion 10 to the light incident portion 22 is determined by the diffraction conditions, the 0th order light T1, −1st order light T2, and +1st order light I1 are obtained. and −2nd order light I2 satisfy the condition of total reflection on both surfaces of the optical waveguide 21, and the inclination angle of the light incident portion 22 is set in advance.

Part of the first light propagated as guided light while being totally reflected within the optical waveguide section 21 is reflected by one surface of the beam splitter 23 , and the rest passes through the beam splitter 23 . The guided light reflected by the beam splitter 23 is taken out in the direction of the external screen 30 as the irradiation light LE, and the image EX is projected onto the external screen 30 . Here, by designing the reflectance of one surface of the beam splitter 23 to be low, it is possible to suppress the intensity of the irradiation light LE and make the image EX invisible.

Further, the guided light that has passed through the beam splitter 23 is totally reflected again by the optical waveguide section 21, reaches the retroreflective section 24, and is retroreflected. The guided light retroreflected by the retroreflection portion 24 travels in the opposite direction in the optical waveguide portion 21, is totally reflected, reaches the beam splitter 23, is reflected, and is reflected as the imaging light L1 in the direction of the viewpoint 60. taken out. At this time, the guided light propagated through the optical waveguide section 21 has an enlarged light diameter, but the guided light reflected by the retroreflective section 24 travels with a reduced light diameter. In the examples shown in FIGS. 2 and 3, since the reflecting surface of the retroreflection portion 24 is concave, the light diameter reaches the beam splitter 23 while being further reduced.

Therefore, the imaging light L1 that is reflected by the beam splitter 23 and travels in the direction of the viewpoint 60 is focused at a predetermined position to form an aerial image A1 in the air. Here, when the retroreflection portion 24 is formed with a flat surface, the optical path length from the diffraction grating portion 10 to the retroreflection portion 24 is the same as the optical path length from the retroreflection portion 24 to the aerial image A1. After forming the aerial image A1, the imaging light L1 is incident on the viewpoint 60 while its light diameter is expanding. As a result, the viewer can view the aerial image A1 formed in the air and the image EX projected on the external screen 30 at the same time by viewing the optical waveguide 21 and the external screen 30 from the viewpoint 60. .

2 and 3 show that the other end of the optical waveguide portion 21 is formed in a convex shape and the retroreflective portion 24 is formed in a concave shape, but the other end is formed in a flat plate shape or a concave shape. The retroreflective portion 24 may be flat or convex. By appropriately designing the shape and curvature of the retroreflection portion 24, the reduction ratio of the diameter of light after being retroreflected by the retroreflection portion 24 can be adjusted, and the aerial image A1 is reflected by the beam splitter 23. The imaged position can be fine-tuned.

Further, the guided light propagating in the optical waveguide section 21 needs to be totally reflected at the interface with the air at least once before reaching the retroreflective section 24 from the beam splitter 23 . Depending on the optical design, it is preferable to select either an even number or an odd number of total reflections at the interface. By securing a distance between the beam splitter 23 and the retroreflector 24 to the extent that the light is totally reflected between them, when viewing the direction of the external screen 30 from the viewpoint 60 through the beam splitter 23, the center of the field of view can be seen. It is possible to prevent the retroreflective portion 24 from being positioned in the vicinity. In addition, since the retroreflective portion 24 does not transmit light and is visible, if the retroreflective portion 24 is positioned in the center of the field of vision, the visibility of the aerial image A1 is lowered, which is not preferable.

Among the first light beams diffracted and branched by the diffraction grating section 10, those that do not satisfy the condition of total reflection on both surfaces of the optical waveguide section 21 are emitted from the surface of the optical waveguide section 21 on the side of the external screen 30 to the outside. It is taken out as irradiation light LV. Here, the region of the optical waveguide section 21 from which the irradiation light LV is extracted corresponds to the second light emitting section in the present invention. The irradiation light LV extracted from the second light emitting portion reaches the external screen 30 and projects an image V1 (not shown).

In the example shown in FIG. 2, the viewpoint direction, which is the traveling direction of the imaging light L1, and the external screen direction, which is the traveling direction of the illumination light LV, are substantially parallel. Accordingly, even if the distance between the external screen 30 and the optical waveguide section 21 is changed, the projected position of the image V1 on the external screen 30 does not change. Therefore, when the viewer views the direction of the external screen 30 from the viewpoint 60, the position where the aerial image A1 is formed and the position where the image V1 is projected do not overlap, and the aerial image A1 and the image V1 are projected within the same visual field. It becomes possible to visually recognize V1 side by side. Here, an example in which the direction of the viewpoint and the direction of the external screen are parallel is shown, but they may be in a direction in which the two intersect at a predetermined angle. By appropriately setting the distance between the external screen 30 and the optical waveguide section 21, the projection position of the image V1 on the external screen 30 can be adjusted. Visual recognition at the viewpoint 60 becomes possible.

Part of the light diffracted by the diffraction grating 10 of the second light emitted from the image irradiation unit 50 also satisfies the condition of total reflection in the optical waveguide 21, so that the image EX is projected similarly to the first light. and aerial image A1 can be formed. Further, the second light diffracted by the diffraction grating section 10 that does not satisfy the condition of total reflection in the optical waveguide section 21 can be used to project the image V1. Alternatively, the second light diffracted by the diffraction grating section 10 may not satisfy the total reflection condition at the optical waveguide section 21, and only the image V1 may be projected onto the external screen 30 with the second light. . Further, even if the second light emitted from the image irradiation unit 50 is not made to enter the diffraction grating unit 10, but is made to enter from the surface of the optical waveguide unit 21 facing the viewpoint 60, and the image V1 is directly projected onto the external screen 30, good. In this case, the area through which the irradiation light LV for projecting the image V1 is transmitted corresponds to the second light emitting portion of the optical waveguide portion 21 .

FIG. 4 is a photograph of an image EX projected on the external screen 30 and an aerial image A1 formed in the air by installing a camera at the position of the viewpoint 60. FIG. , and FIG. 4B shows the camera focused on the imaging position of the aerial image A1. In FIGS. 4(a) and 4(b), the photograph on the left shows how it looks in a bright state with the room light turned on, and the photograph on the right shows how it looks in a dark state with the room light turned off. The image EX and the aerial image A1 are shown at positions indicated by white-lined ellipses in the photograph. As shown in FIG. 4A, the image EX is difficult to see in a bright environment and can be seen in a dark environment. Also, as shown in FIG. 4B, the aerial image A1 is visible in both bright and dark environments. In addition, the aerial image A1 and the image EX can be viewed closely in the same field of view, and the viewer can select an object to be viewed simply by adjusting the visual focal length.

As described above, in the image projection apparatus of the present embodiment, the first light is split by the beam splitter 23 to project the image EX on the external screen 30, and the retroreflection section 24 at the end of the optical waveguide section 21 projects the first light. The first light is retroreflected, and the beam splitter 23 reflects the first light in the direction of the viewpoint to form an aerial image A1. This makes it possible to project and visually recognize a plurality of images at positions at different distances from the viewpoint. In addition, since the diffraction grating section 10 is provided in the light incident section 22 of the light guide plate section 20, and the beam splitter 23 and the retroreflecting section 24 are provided to form the first light emitting section, complicated optical design and an increase in the number of parts are required. It is unnecessary, and it becomes possible to achieve miniaturization and weight reduction.

(Second embodiment)
Next, a second embodiment of the present invention will be described with reference to FIGS. 5 and 6. FIG. The description of the content that overlaps with the first embodiment is omitted. FIG. 5 is a schematic cross-sectional view showing an enlarged first light emitting portion of the image projection device according to the present embodiment. Solid-line arrows and dashed-line arrows shown in the figure schematically indicate paths of light. Also, the area hatched with oblique lines in the drawing indicates the area irradiated with the irradiation light LV. The image projection apparatus of this embodiment differs from that of the first embodiment only in the projection position of the image V1, and the rest of the configuration is the same as that of the first embodiment described with reference to FIG. In this embodiment, the second light emitted from the image irradiation unit 50 is used as the irradiation light LV, and the external screen direction, which is the traveling direction of the irradiation light LV, intersects the viewpoint direction, and the image EX and the image V1 are formed in the same area. is projected onto

As shown in FIG. 5, light propagating through total reflection inside the optical waveguide section 21 is split by the beam splitter 23 to project an image EX onto the external screen 30 as the illumination light LE. Further, the light transmitted through the beam splitter 23 is totally reflected again by the optical waveguide section 21 and reaches the retroreflection section 24. After being retroreflected, the light is reflected by the beam splitter 23 to form an aerial image A1 as the imaging light L1. image.

Further, the traveling direction of the irradiation light LV projected onto the external screen 30 from the second light emitting portion is a direction that intersects with the viewing direction, which is the traveling direction of the imaging light L1. In the example shown in FIG. 5, the second light emitted from the image irradiation unit 50 does not enter the diffraction grating unit 10 and is directly irradiated as the irradiation light LV onto the external screen 30 via the optical waveguide unit 21. An image V1 is projected onto the external screen 30 .

FIG. 6 is a photograph of an image EX and an image V1 projected on the external screen 30 and an aerial image A1 formed in the air by installing a camera at the position of the viewpoint 60. FIG. The camera is focused on the screen 30, and FIG. 6B is the image obtained by focusing the camera on the imaging position of the aerial image A1. The image EX and the aerial image A1 are captured at the positions indicated by white-lined ellipses in the photograph, and the image V1 is captured in a larger range than the image EX. As shown in FIG. 6A, the image EX is superimposed on the image V1 and displayed, and both can be visually recognized at the same time. Also, the viewer can select an object to visually recognize only by adjusting the focal length of vision.

In this embodiment, since the image V1 is projected over a wide range of the external screen 30 using the second light as the irradiation light LV, it is possible to perform image projection in which the image V1 is superimposed on the aerial image A1 as a background image. In addition, by projecting the image EX onto the external screen 30, the projection positions of the image V1, which is the background image, and the image EX have the same distance from the viewpoint 60, so that the viewer can view two different images V1 and A1 at the same time. The image EX can be visually recognized.

(Third embodiment)
Next, a third embodiment of the present invention will be described with reference to FIGS. 7 to 10. FIG. The description of the content that overlaps with the first embodiment is omitted. In the present embodiment, a partial reflection portion is provided between the beam splitter 23 and the retroreflection portion 24, which constitute the first light emission portion, to reflect part of the guided light with a predetermined reflectance and transmit the rest. is different from the first embodiment. FIG. 7 is a schematic diagram showing the structure of the image projection device according to this embodiment.

As shown in FIG. 7, the image projection device includes a diffraction grating section 10, a light guide plate section 20, an external screen 30, and image irradiation sections 40 and 50. As shown in FIG. A viewer wearing the image projection device views the direction of the light guide plate 20 and the external screen 30 from the position of the viewpoint 60 . As shown in FIG. 1, the diffraction grating section 10 is an optical element including a flat plate portion 11, convex portions 12, concave portions 13, and a covering portion, and is formed separately from the light guide plate portion 20. FIG. The light guide plate portion 20 is a plate-like member made of a translucent material, and includes an optical waveguide portion 21 , a light incident portion 22 , a beam splitter 23 , a retroreflection portion 24 , and a partial reflection portion 25 . I have.

The partial reflection section 25 is an optical element that reflects part of the light with a predetermined reflectance and transmits the rest of the light, and is provided on the optical path between the beam splitter 23 and the retroreflection section 24 . In the example shown in FIG. 7, a partial reflection portion 25 is formed between the end portion of the optical waveguide portion 21 and the retroreflection portion 24 . 7 shows an example in which the end portion of the optical waveguide portion 21, the retroreflecting portion 24, and the partial reflecting portion 25 are formed in a flat shape. and a convex mirror. Alternatively, a combination of three-dimensional parabolic concave-convex shapes may be used.

FIG. 8 is a schematic cross-sectional view showing an enlarged first light emitting portion of the image projection device according to this embodiment. Solid-line arrows and dashed-line arrows shown in the figure schematically indicate paths of light. Also, the area hatched with oblique lines in the drawing indicates the area irradiated with the irradiation light LV. As in the first embodiment, the first light emitted from the image irradiation section 40 or the second light emitted from the image irradiation section 50 enters the optical waveguide section 21 from the light incident section 22 and is guided as guided light. The light is guided while being totally reflected by the wave portion 21 . The guided light reflected by the beam splitter 23 is taken out as irradiation light LE to the external screen 30 and projects an image EX on the external screen 30 .

The guided light that has passed through the beam splitter 23 is reflected by the partial reflection portion 25 and the retroreflection portion 24, then enters the beam splitter 23 again, is reflected, and is taken out in the direction of the viewpoint 60 as imaging lights L1 and L2. At this time, since the light reflected by the partial reflection portion 25 is specular reflection, the guided light propagated while expanding the light diameter in the optical waveguide portion 21 is reflected by the beam splitter 23 and reaches the viewpoint 60. It progresses while the light diameter expands. As a result, at the viewpoint 60, the aerial image A2 appears to be formed in the space between the optical waveguide section 21 and the external screen 30. FIG.

Further, the light transmitted through the partial reflection portion 25 is incident on the retroreflection portion 24, where the guided light is retroreflected and reflected by the beam splitter 23 until it reaches the viewpoint 60 while the light diameter is reduced. proceed. As a result, at the viewpoint 60, the aerial image A1 is visually recognized as if it were formed in the space between the optical waveguide section 21 and the viewpoint 60. FIG. Further, the traveling direction of the irradiation light LV projected onto the external screen 30 from the second light emitting portion is a direction that intersects with the viewing direction, which is the traveling direction of the imaging lights L1 and L2. projected on top.

FIG. 9 is a photograph of an image EX and an image V1 projected on the external screen 30, and aerial images A1 and A2 formed in the air by installing a camera at the position of the viewpoint 60, and FIG. 9(a). 9B focuses the camera on the imaging position of the aerial image A1, FIG. 9B focuses the camera on the imaging position of the aerial image A2, and FIG. It is a thing. Aerial images A1 and A2 and image EX are shown at positions indicated by white-lined ellipses in the photograph, and image V1 is shown in a larger range than image EX.

As shown in FIG. 9A, by focusing on the viewpoint 60 side of the optical waveguide 21, the aerial image A1 can be clearly captured. Further, as shown in FIG. 9B, by focusing between the optical waveguide section 21 and the external screen 30, the aerial image A2 can be clearly captured. Also, as shown in FIG. 9C, when the external screen 30 is focused, the image EX and the image V1 can be clearly captured. In addition, the aerial images A1 and A2, the image EX and the image V1 can be closely viewed in the same field of view, and the viewer can select an object to be viewed simply by adjusting the visual focal length.

10A and 10B are diagrams showing the beam profiles of the aerial images A1 and A2. FIG. 10A is a photograph focused from the viewpoint 60, and FIGS. Three-dimensional luminance profiles are shown, FIG. 10(d) being the luminance profile in the x direction and FIG. 10(e) being the luminance profile in the y direction. FIGS. 10(a) and 10(b) show enlarged regions surrounded by white lines in FIGS. 9(a) and 9(b), respectively. FIGS. 10(c) to 10(e) show the measurement results of brightness at the imaging positions of the aerial images A1 and A2, respectively. "x direction" and "y direction" shown in FIG. 10 indicate the x-axis direction and the y-axis direction shown in FIG. 9(c).

As shown in FIGS. 10(a) to 10(c), the aerial image A1 is formed as an elliptical shape elongated in the x-axis direction, and the aerial image A2 is formed as an elliptical shape elongated in the y-axis direction. . Further, as shown in FIGS. 10D and 10E, the half-value width in the x-axis direction of the aerial image A1 was about 31 pixels, and the half-value width in the y-axis direction was about 10 pixels. The half-value width in the x-axis direction of the aerial image A2 was about 20 pixels, and the half-value width in the y-axis direction was about 25 pixels. Therefore, the aerial images A1 and A2 are formed into different shapes, and the shape visually recognized when the viewer changes the visual focal length changes between the aerial images A1 and A2.

As described above, in the image projection apparatus of the present embodiment, guided light specularly reflected by the partial reflection portion 25 at the end of the optical waveguide portion 21 forms an aerial image A2, and is retroreflected by the retroreflection portion 24 to form the aerial image A2. An aerial image A1 is formed by wave light. Also, the image EX and the image V1 are projected onto the external screen 30 . This makes it possible to project and visually recognize a plurality of images at positions at different distances from the viewpoint. In addition, since the diffraction grating section 10 is provided in the light entrance section 22 of the light guide plate section 20, and the beam splitter 23, the partial reflection section 25, and the retroreflection section 24 are provided to constitute the first light emission section, complicated optical design and There is no need to increase the number of parts, and it is possible to reduce the size and weight.

(Fourth embodiment)
Next, a fourth embodiment of the invention will be described with reference to FIG. The description of the content that overlaps with the first embodiment is omitted. FIG. 11 is a schematic diagram showing the structure of the image projection device according to this embodiment. In this embodiment, two light guide plate portions 20 are provided, and a common diffraction grating portion 10 is arranged to face the light incident portion 22 provided in each light guide plate portion 20 .

As shown in FIG. 11, the image projection device includes one diffraction grating section 10, two light guide plate sections 20, an external screen 30, and image irradiation sections 40 and 50. As shown in FIG. A viewer wearing the image projection device views the direction of the light guide plate 20 and the external screen 30 with both eyes from two viewpoints 60 . As shown in FIG. 1, the diffraction grating section 10 is an optical element including a flat plate portion 11, convex portions 12, concave portions 13, and a covering portion, and is formed separately from the light guide plate portion 20. FIG. The light guide plate portion 20 is a plate-like member made of a translucent material, and includes an optical waveguide portion 21, a light incident portion 22, a beam splitter 23, and a retroreflection portion 24, respectively.

The two light guide plate portions 20 are arranged so that the light incident portions 22 are adjacent to each other, and the common diffraction grating portion 10 is arranged across the two light incident portions 22 so as to face each other. Further, the first light is incident on the diffraction grating section 10 from one image irradiation section 40 , and the first light diffracted by the diffraction grating section 10 is transmitted from the light incident section 22 of each light guide plate section 20 into the optical waveguide section 21 . incident on Each of the two light guide plate portions 20 has a flat plate shape and is arranged in a V shape.

As shown in FIG. 1, in the diffraction grating section 10, the first light is diffracted by the concave and convex portions formed by the convex portions 12 and the concave portions 13, and the 0th order light T1 and the +1st order light I1 travel rightward in the drawing. , the -1st order light T2 and the -2nd order light I2 travel leftward in the figure. Therefore, the 0th-order light T1 and the +1st-order light I1 are incident on the optical waveguide section 21 arranged to face the right half of the diffraction grating section 10, and the optical waveguide section 21 arranged to face the left half of the diffraction grating section 10. The -1st order light T2 and the -2nd order light I2 are incident on the wave portion 21 .

In the example shown in FIG. 11, by designing the inclination angle of the light incident portion 22 and the shape of the optical waveguide portion 21 so that the +1st-order light I1 satisfies the total reflection condition of the optical waveguide portion 21 arranged on the right side, The +1st order light I1 is guided as guided light. Similarly, by designing the inclination angle of the light incident part 22 and the shape of the optical waveguide part 21 so that the -2nd order light I2 satisfies the total reflection condition of the optical waveguide part 21 arranged on the left side, the -2nd order light I2 is guided as guided light.

The first light (guided light) guided through the two light guide plate portions 20 is reflected by the beam splitter 23 and the retroreflecting portion 24 provided on the other end side, respectively, and is taken out in the direction of the viewpoint 60 to be aerial light. Image A1 is formed. Although not shown in FIG. 11, when the partial reflection portion 25 is provided between the retroreflection portion 24 and the beam splitter 23 as in the third embodiment, a An aerial image A2 can also be formed.

The image irradiation unit 50 can directly irradiate the external screen 30 with the irradiation light LV through the light guide plate unit 20 and project the image V1 over a wide area on the external screen 30 . FIG. 11 shows a state in which the irradiation light LV emitted from the image irradiation unit 50 is projected on the left half of the external screen 30, but by using an optical member such as a separate lens, the entire external screen 30 can be irradiated. It is also possible to illuminate the light LV and project the image V1 over the entire external screen 30 so as to cover the entire field of view.

As described above, in the image projection apparatus of the present embodiment, by providing the diffraction grating unit 10 common to the two light guide plate units 20, the formation of the aerial images A1 and A2 is visually recognized by both eyes of the viewer. be able to. Further, by projecting the image V1, which is a background image, onto the external screen 30 with the irradiation light LV emitted by the image irradiation unit 50, the aerial images A1 and A2 can be superimposed and projected on the image V1. Also, the image projection apparatus of this embodiment does not require complicated optical design or an increase in the number of parts, and can be reduced in size and weight.

(Modified example of the fourth embodiment)
Next, a modified example of the fourth embodiment of the invention will be described with reference to FIG. The description of the content that overlaps with the first embodiment is omitted. FIG. 12 is a schematic diagram showing the structure of an image projection device according to a modification of the fourth embodiment. This modified example differs from the fourth embodiment in that the light guide plate portion 20 has a curved shape.

In the example shown in FIG. 12, by designing the inclination angle of the light incident portion 22 and the shape of the optical waveguide portion 21 so that the zero-order light T1 satisfies the total reflection condition of the optical waveguide portion 21 arranged on the right side, The zero-order light T1 is guided as guided light. Similarly, by designing the inclination angle of the light incident part 22 and the shape of the optical waveguide part 21 so that the -1st order light T2 satisfies the total reflection condition of the optical waveguide part 21 arranged on the left side, the -1st order light T2 is guided as guided light. In this modification, as in the fourth embodiment, the aerial images A1 and A2 formed in the air from two viewpoints 60 and the image V1 projected on the external screen 30 can be viewed.

In the example shown in FIG. 12, the two light guide plate portions 20 have a curved surface shape along the direction of the viewpoint 60, but the incident angle of the first light from the diffraction grating portion 10 to the light incident portion 22 is Since it is determined by the diffraction conditions, it is possible to design the light guide plate section 20 so as to repeat total reflection along the curved surface. In FIG. 12, the left and right light guide plate portions 20 are drawn in a line-symmetrical shape. 22 may be different on the left and right.

In this modified example, since the optical waveguide part 21 has a curved surface shape, the degree of freedom in designing the image projection device is improved, and it is possible to improve the design and the wearing comfort.

(Fifth embodiment)
Next, a fifth embodiment of the present invention will be described with reference to FIGS. 13 and 14. FIG. The description of the content that overlaps with the first embodiment is omitted. FIG. 13 is a schematic diagram showing the structure of the image projection device according to this embodiment. As shown in FIG. 13, the image projection device includes a diffraction grating section 10, a light guide plate section 20, an external screen 30, and image irradiation sections 40 and 50. As shown in FIG. A viewer wearing the image projection device views the direction of the light guide plate 20 and the external screen 30 from the position of the viewpoint 60 .

As shown in FIG. 1, the diffraction grating section 10 is an optical element including a flat plate portion 11, convex portions 12, concave portions 13, and a covering portion, and is formed separately from the light guide plate portion 20. FIG. The light guide plate portion 20 is a plate-shaped member made of a translucent material, and includes an optical waveguide portion 21 , a light incident portion 22 , a beam splitter 23 , a retroreflection portion 24 , and a partial reflection portion 25 . , with an optical filter 26 . A second light emitting portion from which the second light emitted from the image irradiating portion 50 is extracted is provided with an optical filter 61, an optical shutter portion 62, and a projection lens 63. As shown in FIG.

The optical filters 26 and 61 are optical members that transmit light in a predetermined wavelength range and block light in other wavelengths. In this embodiment, the optical filter 26 is a band-pass filter that blocks the wavelength of the second light and transmits the wavelength of the first light or an optical filter equivalent thereto, and the optical filter 61 blocks the wavelength of the first light and transmits the second light. A band-pass filter or an optical filter corresponding thereto is used. As an example, the first light emitted by the image irradiation unit 40 is red light, and the second light emitted by the image irradiation unit 50 is green light. Therefore, the optical filter 26 may use a long-pass filter and the optical filter 61 may use a short-pass filter.

The optical shutter section 62 is an optical member driven and controlled by a control section (not shown) to switch between transmission and blocking of light. A specific configuration of the optical shutter unit 62 is not limited, and a known liquid crystal shutter or the like can be used. The projection lens 63 is an optical member for enlarging the light diameter of the irradiation light LV extracted from the second light emitting portion and projecting it onto the external screen 30 . Although one lens is shown as the projection lens 63 in FIG. 13, the projection lens 63 may be configured by combining a plurality of lenses.

In the first light emitted from the image irradiation unit 40, part of the light diffracted by the diffraction grating unit 10 enters from the light incidence unit 22, is totally reflected in the optical waveguide unit 21, and is guided as guided light. be. The guided light of the first light reaches the beam splitter 23 while being totally reflected, and is partially reflected to project the image EX on the external screen 30 . Of the guided light of the first light, the light that has passed through the beam splitter 23 is totally reflected again and reaches the end of the optical waveguide section 21 .

The guided light of the first light that has reached the end of the optical waveguide section 21 is transmitted through the optical filter 26 and enters the partial reflection section 25 . to reach The guided light is retroreflected by the retroreflector 24 . The first light retroreflected by the retroreflector 24 forms an aerial image A1 in the air between the viewpoint 60 and the optical waveguide 21 as described in the first embodiment. Also, the light specularly reflected by the partial reflection portion 25 forms an aerial image A2 in the air between the optical waveguide portion 21 and the external screen 30 .

Light that does not satisfy the condition of total reflection in the optical waveguide section 21 in the first light is extracted from the second light emitting section toward the external screen 30 , and the second light emitting section is provided with an optical filter 61 . Therefore, the first light is blocked by the optical filter 61 and is not projected onto the external screen 30 .

Part of the light diffracted by the diffraction grating section 10 is incident on the second light emitted from the image irradiation section 50 through the light incidence section 22 and is totally reflected in the optical waveguide section 21 to be guided as guided light. be. At this time, the incident angle of the second light with respect to the diffraction grating section 10 is made different from the incident angle of the first light, and by selecting the incident angle that satisfies the appropriate diffraction conditions, the first light and the second light are guided. The angles of incidence on wave section 21 can be set to be the same. Further, if the incident positions of the first light and the second light to the diffraction grating section 10 are the same, the paths of the first light and the second light guided by total reflection in the optical waveguide section 21 should be the same. can be done.

The guided light of the second light also reaches the beam splitter 23 while being totally reflected, and is partially reflected to project the image EX on the external screen 30 . Of the guided light of the second light, the light that has passed through the beam splitter 23 is totally reflected again and reaches the end of the optical waveguide section 21 . The guided light of the second light that has reached the end of the optical waveguide portion 21 is blocked by the optical filter 26 and does not reach the partial reflection portion 25 and the retroreflection portion 24 . Therefore, the second light reflected back to the beam splitter 23 disappears, and the aerial images A1 and A2 are not formed by the second light.

Of the second light, the light that does not satisfy the condition of total reflection in the optical waveguide section 21 is extracted from the second light emitting section toward the external screen 30, and when the optical shutter section 62 is in the transmission state, the projection lens 63 is used. The external screen 30 is irradiated with the irradiation light LV through the projection screen 30, and the image V1 is projected. When the light shutter section 62 is in the blocking state, the irradiation light LV of the second light is blocked and the image V1 is not projected.

As described above, in the present embodiment, by providing the optical filter 26 between the beam splitter 23 and the retroreflector 24, it is possible to form the aerial images A1 and A2 only with the first light. Further, by providing the optical filter 61 in the second light emitting portion, it is possible to project the image V1 on the external screen 30 only with the second light. Therefore, the contents of the aerial images A1 and A2 formed by the first light emitted from the image irradiation section 40 and the contents of the image V1 projected by the second light emitted from the image irradiation section 50 can be made different. It is possible to realize various image projections.

In addition, the imaging efficiency of the aerial images A1 and A2 can be improved by including a lens optical unit with a variable focal length in the image irradiation unit 40 and adjusting the divergence angle of the first light incident on the diffraction grating unit 10. It can also be changed.

(Modified example of the fifth embodiment)
Next, a modified example of the fifth embodiment of the invention will be described with reference to FIG. The description of the content that overlaps with the first embodiment is omitted. FIG. 14 is a schematic diagram showing the structure of an image projection device according to a modification of the fifth embodiment. As shown in FIG. 14, the image projection device includes a diffraction grating section 10, a light guide plate section 20, an external screen 30, and image irradiation sections 40a, 40b and 50. As shown in FIG.

In this modification, the image irradiation unit 40a irradiates the first light of the first wavelength containing the first image, and the image irradiation unit 40b irradiates the second light of the second wavelength containing the second image. , the image irradiation unit 50 irradiates the third light of the third wavelength containing the third image. In one example, the first wavelength is red light, the second wavelength is blue light, and the third wavelength is green light. In this modification, a notch filter that blocks the third wavelength and transmits the first and second wavelengths is used as the optical filter 26, and a band filter that blocks the first and second wavelengths and transmits the third wavelength is used as the optical filter 61. Use a pass filter. In this modification, a dichroic mirror (selective reflection section) that reflects the first wavelength and transmits the second wavelength is used as the partial reflection section 25 .

The incident angles of the first light, the second light, and the third light irradiated onto the diffraction grating section 10 from the image irradiation sections 40a, 40b, and 50 are selected so as to satisfy appropriate diffraction conditions, and the diffraction grating section 10 The light incident on the optical waveguide portion 21 from the optical waveguide portion 21 is totally reflected along the same path and propagates through the optical waveguide portion 21 .

Part of the light diffracted by the diffraction grating section 10 enters from the light incident section 22 and is totally reflected inside the optical waveguide section 21 of the first light and the second light emitted from the image irradiating sections 40a and 40b. Waveguided as guided light. The guided light of the first light and the second light reaches the beam splitter 23 while being totally reflected, and is partially reflected to project the image EX on the external screen 30 . Of the guided light of the first light and the second light, the light that has passed through the beam splitter 23 is totally reflected again and reaches the end of the optical waveguide section 21 .

The guided light of the first light that has reached the end of the optical waveguide section 21 is transmitted through the optical filter 26, enters the partial reflection section 25, and is specularly reflected. The first light specularly reflected by the partial reflection portion 25 forms an aerial image A2 in the air between the optical waveguide portion 21 and the external screen 30 . The guided light of the second light that has reached the end of the optical waveguide section 21 passes through the optical filter 26 and the partial reflection section 25, enters the retroreflection section 24, and is retroreflected. The second light retroreflected by the retroreflector 24 forms an aerial image A1 in the air between the viewpoint 60 and the optical waveguide 21 as described in the first embodiment.

Of the first light and the second light, the light that does not satisfy the condition of total reflection in the optical waveguide section 21 is extracted from the second light emitting section toward the external screen 30, and the second light emitting section includes an optical filter 61. Therefore, the first light and the second light are blocked by the optical filter 61 and are not projected onto the external screen 30 .

Part of the light diffracted by the diffraction grating section 10 enters the light incident section 22 of the third light emitted from the image irradiation section 50, is totally reflected in the optical waveguide section 21, and is guided as guided light. be. The guided light of the third light also reaches the beam splitter 23 while being totally reflected, and is partially reflected to project the image EX on the external screen 30 . Of the guided light of the third light, the light that has passed through the beam splitter 23 is totally reflected again and reaches the end of the optical waveguide section 21 .

The guided light of the third light that has reached the end of the optical waveguide section 21 is blocked by the optical filter 26 and does not reach the partial reflection section 25 and the retroreflection section 24 . Therefore, there is no third light reflected back to the beam splitter 23, and the aerial images A1 and A2 are not formed by the third light.

Of the third light, the light that does not satisfy the condition of total reflection in the optical waveguide section 21 is extracted from the second light emitting section toward the external screen 30, and when the optical shutter section 62 is in the transmission state, the projection lens 63 The external screen 30 is irradiated with the irradiation light LV through the projection screen 30, and the image V1 is projected. When the light shutter section 62 is in the blocking state, the irradiation light LV of the second light is blocked and the image V1 is not projected.

As described above, in the present embodiment, by providing the optical filter 26 between the beam splitter 23 and the retroreflector 24, it is possible to form the aerial images A1 and A2 with the first light and the second light, respectively. can. Further, by providing the optical filter 61 in the second light emitting portion, it is possible to project the image V1 on the external screen 30 only with the third light. Therefore, the contents of the aerial images A1 and A2 formed by the first light and the second light emitted from the image irradiation section 40 and the contents of the image V1 projected by the third light emitted from the image irradiation section 50 By changing , various image projections can be realized.

(Sixth embodiment)
Next, a sixth embodiment of the invention will be described with reference to FIG. The description of the content that overlaps with the first embodiment is omitted. FIG. 15 is a schematic diagram showing a structural example of the retroreflective portion 24 in this embodiment. As shown in FIG. 15, the retroreflective portion 24 has microbeads selectively formed on the sheet portion 24a. 24c are mixed and formed.

The sheet portion 24a is a thin plate-like member having a reflective surface. It is preferable that the sheet portion 24a has flexibility. It can take the shape of a convex mirror as shown.

The retroreflective area 24b is an area in which microbeads are formed on the surface of the sheet portion 24a, and the light incident on the retroreflective area 24b is retroreflected in the incident direction by being reflected within the microbeads. No microbeads are formed in the specular reflection region 24c, and the reflecting surface of the sheet portion 24a is exposed. Therefore, light incident on the specular reflection region 24c is specularly reflected by the reflecting surface of the sheet portion 24a.

The retroreflective portion 24 of this embodiment is formed by forming a mask on the specular reflection region 24c of the sheet portion 24a using a photolithography technique, and depositing microbeads on the region where the mask is not formed to form the retroreflective region 24b. can be formed by a method of forming After depositing the microbeads, the mask layer is removed to expose the reflective surface of the sheet portion 24a in the specular reflection area 24c.

As shown in FIGS. 15(a) to 15(c), part of the light incident on the retroreflecting portion 24 while the light diameter is expanding is retroreflected as imaging light L1 by the retroreflecting region 24b. and the light diameter is reduced and reflected. In the regular reflection area 24c, the light is retroreflected as the imaging light L2, and the light diameter is enlarged and reflected. Here, as shown in FIGS. 15(a) to 15(c), depending on whether the retroreflector 24 is a flat plate, a concave mirror, or a convex mirror, the light diameters of the imaging lights L1 and L2 are It is possible to adjust the enlargement and reduction ratio of

By using the retroreflective portion 24 of the present embodiment, the guided light that has reached the end portion of the optical waveguide portion 21 is partially re-reflected and the rest is specularly reflected, as shown in FIG. 8 in the third embodiment. Aerial images A1 and A2 can be formed in the same manner as the object. The difference from the third embodiment is that the sheet portion 24a is a thin plate-like member and has flexibility as described above. In addition, the retroreflection efficiency can be designed by adjusting the arrangement and purity of the microbeads on the surface of the sheet portion 24a. Also, by depositing a metal thin film on the surface of the sheet portion 24a, it is possible to construct a reflective retroreflective element or a retroreflective optical filter in which reflection and retroreflection are mixed. By using these structures for the seat portion 24a, it is possible to improve the degree of freedom in optical design and the design.

(Seventh embodiment)
Next, a seventh embodiment of the invention will be described. The description of the content that overlaps with the first embodiment is omitted. In the first to sixth embodiments, the wavelength of the first light emitted from the image irradiation unit 40 is used as it is for the projection of the image EX and the image V1 and the formation of the aerial images A1 and A2. However, by providing a wavelength converting member that converts the wavelength of the first light in the first light emitting section or the second light emitting section, the image EX and the image V1 can be projected in a color different from that of the light emitted from the image irradiating section 40. and aerial images A1 and A2 may be formed.

(Eighth embodiment)
Next, an eighth embodiment of the invention will be described. The description of the content that overlaps with the first embodiment is omitted. From the first embodiment to the seventh embodiment, a grating having periodic irregularities was used as the diffraction grating section 10 . However, the concave-convex portion of the diffraction grating section 10 does not need to have a periodic structure, and may have a holographic grating structure as long as it can diffract light in at least two directions. Moreover, although an example in which the diffraction grating section 10 is formed separately from the light guide plate section 20 has been shown, the diffraction grating section 10 may be formed inside the optical waveguide section 21 or on the surface of the light incident section 22 .

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

DESCRIPTION OF SYMBOLS 10... Diffraction grating part 20... Light-guide plate part 30... External screen 40, 40a, 40b, 50... Image irradiation part 60... Viewpoint 11... Flat part 12... Convex part 13... Concave part 21... Optical waveguide part 22... Light-incidence part 23... Beam splitter 24... Retroreflection part 24a... Sheet part 24b... Retroreflection area 24c... Specular reflection area 25... Partial reflection part 26... Optical filter 41... Light source part 42... Half-wave plate 43... Polarizer 45, 46, 47 Mirror 48 Bandpass filter 61 Optical filter 62 Optical shutter section 63 Projection lenses A1, A2 Aerial images V1, EX Image

Claims (15)

a first image irradiation unit that emits the first light;
a first light incident portion into which the first light is incident; an optical waveguide portion that guides a portion of the first light as guided light while totally reflecting the portion; and a portion of the guided light that is emitted in a viewing direction. a light guide plate portion having a first light emitting portion;
A diffraction grating section provided in the first light incidence section,
The image projection device, wherein the first light emitting section includes a beam splitter provided in the optical waveguide section, and a retroreflective section provided at an end of the optical waveguide section. The image projection device according to claim 1,
The image projection apparatus, wherein the light guide plate section includes a second light emitting section that transmits one of the lights split by the diffraction grating section and emits the light in an external screen direction different from the viewpoint direction. The image projection device according to claim 2,
The image projection device, wherein the viewpoint direction and the external screen direction are substantially parallel. 4. The image projection device according to claim 2 or 3,
An image projection device, wherein an optical shutter section for switching transmission and blocking of light is provided in the first light exit section or the second light exit section. The image projection device according to any one of claims 2 to 4,
An image projection apparatus, wherein a wavelength converting section for converting the wavelength of the first light is provided in the first light emitting section or the second light emitting section. The image projection device according to any one of claims 1 to 5,
The image projection device, wherein the retroreflection section is formed by a mixture of a specular reflection area that specularly reflects light and a retroreflection area that retroreflects light. The image projection device according to any one of claims 1 to 5,
An image projection apparatus according to claim 1, wherein a partial reflection section that reflects part of the waveguided light and transmits the rest is provided between the beam splitter and the retroreflection section. The image projection device according to any one of claims 1 to 7,
A second image irradiation unit that irradiates the diffraction grating with a second light,
the angles of incidence of the first light and the second light with respect to the diffraction grating section are different;
The image projection apparatus, wherein the optical waveguide part guides part of the second light as guided light while totally reflecting the part of the second light. The image projection device according to claim 8,
An image projection apparatus, wherein a selective reflection section that reflects the wavelength of the first light and transmits the wavelength of the second light is provided between the beam splitter and the retroreflection section. The image projection device according to claim 8 or 9,
An image projection apparatus, wherein an optical filter for selectively blocking the wavelength of the first light or the wavelength of the second light is provided in the second light emitting section. The image projection device according to any one of claims 1 to 10,
comprising two said light guide plate portions,
The image projection device according to claim 1, wherein one diffraction grating section is provided in common to each of the first light incident sections of the light guide plate section. The image projection device according to any one of claims 1 to 11,
An image projection device, wherein the optical waveguide has a curved shape. The image projection device according to any one of claims 1 to 12,
The image projection device, wherein the first image irradiation unit includes a liquid crystal display element or a digital mirror device, and changes the content of the first image included in the first light over time. The image projection device according to any one of claims 1 to 13,
The diffraction grating section has a flat plate-shaped portion forming a light incident surface, and an uneven portion formed integrally with the flat plate-shaped portion, and is formed separately from the light guide plate portion. Image projection device. The image projection device according to any one of claims 1 to 13,
The image projection apparatus, wherein the diffraction grating section has a holographic grating that diffracts light in at least two directions.

Images