JP2022129525A - Image projector - Google Patents

Abstract

To provide an image projector that can simplify an optical member needed to project an image using light with a plurality of wavelengths and can reduce the size and the weight.SOLUTION: The image projector includes: a first image irradiation unit (40a) for applying a first light; a second image irradiation unit (40b) for applying a second light; a first light entering unit (22) to which the first light and the second light enter; an optical waveguide unit (21) for guiding a part of the first light and a part of the second light as a first waveguide light and a second waveguide light; a light guide plate unit (20) having a first light emission unit (23) for emitting the first waveguide light and the second waveguide light; and a first diffraction grating unit (10) provided in the first light entering unit (22). The incident angle of the first light to the first diffraction grating unit (10) is different from the incident angle of the second light to the first diffraction grating unit (10). A part of the first light and a part of the second light diffracted by the first diffraction grating unit (10) satisfy the total reflection condition of the optical 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 conventional wearable HUDs, in order to irradiate light of multiple wavelengths and project colorful images, it is necessary to use multiple light sources and optical members suitable for each wavelength. However, there is a problem that the number of parts increases. Further, in the case of projecting an image by superimposing light of a plurality of wavelengths, there is a problem that it is difficult to adjust the optical axis of the optical member.

Therefore, the present invention has been devised in view of the above-mentioned conventional problems, and it is possible to simplify the optical members necessary for performing image projection using light of multiple wavelengths, and to reduce the size and weight. An object of the present invention is to provide an image projection device.

In order to solve the above problems, the image projection device of the present invention includes a first image irradiation section that emits a first light, a second image irradiation section that emits a second light, and the first light and the second light. a first light incident portion into which light is incident; an optical waveguide portion that guides part of the first light and part of the second light as first guided light and second guided light, respectively; a light guide plate portion having a first light emitting portion for emitting guided light and the second guided light; and a first diffraction grating portion provided in the first light incident portion. The incident angles of the first light and the second light are different, and part of the first light and part of the second light diffracted by the first diffraction grating meet the total reflection condition of the optical waveguide. characterized by fulfilling

In such an image projector of the present invention, the first light and the second light are made incident on the first diffraction grating section at different angles of incidence, and the first light and the second light are totally reflected by the optical waveguide section. Since the light is guided up to the first light emitting portion, it is possible to simplify the optical member and reduce the size and weight.

Further, in one aspect of the present invention, the first guided light and the second guided light have an incident position in the first light entrance section, a reflected position in the optical waveguide section, and an exit position in the first light exit section. They are substantially the same.

Further, in one aspect of the present invention, the light guide plate section includes a second light emitting section that transmits one of the lights split by the first diffraction grating section and emits the light toward an external screen, The light emitting section emits the first guided light and the second guided light toward the external screen.

Further, in one aspect of the present invention, a digital mirror device having a plurality of minute mirrors controlled based on image information is provided, and the first guided light and the second guided light emitted from the first light emitting section are provided. is reflected in the viewing direction through the digital mirror device.

In one aspect of the present invention, a second diffraction grating section provided in the first light emitting section is provided, and the second diffraction grating section includes a part of the first guided light and a part of the second guided light. Some of the light beams are diffracted, respectively, and irradiated in the viewpoint direction at different emission angles as first and second outgoing diffracted light beams.

Further, in one aspect of the present invention, the first diffraction grating and the second diffraction grating are arranged parallel or perpendicular to each other.

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

In one aspect of the present invention, the first 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, and is separate from the light guide plate portion. formed in the body.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide an image projection apparatus capable of simplifying the optical members necessary for projecting an image using light of multiple wavelengths and reducing the size and weight of the apparatus.

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. 2 is a schematic perspective view showing an enlarged light incident portion 22 of the image projection device according to the first embodiment; FIG. 4A and 4B are photographs showing paths of light when a laser beam is incident on the light guide plate portion 20, FIG. 4A showing the path of red light, FIG. (c) shows paths when red light and green light are incident simultaneously. FIG. 5 is a schematic diagram showing the structure of an image projection device according to a second embodiment; FIG. 10 is a schematic diagram showing the structure of an image projection device according to a modification of the second embodiment; FIG. 11 is a schematic diagram showing the structure of an image projection device according to a third embodiment; FIG. 11 is a schematic diagram showing the structure of an image projection device according to a fourth embodiment; FIG. 11 is a schematic perspective view showing an enlarged light emitting portion 23 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 fifth embodiment; FIG. 12 is a schematic diagram showing the structure of an image projection device according to a modification of the fifth embodiment; 12A and 12B are schematic perspective views showing the arrangement of the diffraction grating portion 10 and the diffraction grating portion 80 in the sixth embodiment, FIG. 12A showing the diffraction grating portion 10 and FIG. 12B showing the diffraction grating portion 80; there is FIG. 11 is a schematic diagram showing a structural example of an image irradiation unit 40 of an image projection device according to 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 device includes a diffraction grating section 10, a light guide plate section 20, and image irradiation sections 40a, 40b, and 40c. 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 light emitting portion 23 , an optical filter 31 , and an optical shutter portion 32 . I have.

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 light passes through the optical waveguide portion 21 from one surface side to the other surface side, it is possible to visually recognize the direction of the external screen 60 through the optical waveguide portion 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. An end face is formed on the other end side of the optical waveguide portion 21 and a light emitting portion 23 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 light emitting portion 23 is an inclined surface formed at the other end of the optical waveguide portion 21 (the end portion opposite to the light incident portion 22), and corresponds to the first light emitting portion in the present invention. The inclined surface of the light emitting portion 23 is set at an angle such that the light propagating through the optical waveguide portion 21 is not totally reflected at the light emitting portion 23 . Moreover, in order to improve the efficiency of extracting light from the light emitting portion 23, the surface of the light emitting portion 23 may be provided with an antireflection film or an antireflection structure.

The optical filter 31 is an optical member that transmits light in a predetermined wavelength range and blocks light in other wavelengths. In this embodiment, as the optical filter 31, a band-pass filter is used that blocks light of a predetermined wavelength and transmits light of other wavelengths.

The optical shutter section 32 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 32 is not limited, and a known liquid crystal shutter or the like can be used.

The image irradiation units 40a, 40b, and 40c are devices for irradiating the diffraction grating unit 10 with the first light, the second light, and the third light for projecting the first image, the second image, and the third image, respectively. be. The image irradiation units 40a and 40b respectively correspond to a first image irradiation unit and a second image irradiation unit in the present invention. The image irradiation units 40a, 40b, and 40c are provided as separate structures, and the incident angles of the first light, the second light, and the third light with respect to the diffraction grating unit 10 are different. Also, the wavelengths of the first light, the second light, and the third light are different. For example, the first light is red light, the second light is green light, and the third light is blue light.

The specific configuration of the image irradiation units 40a, 40b, and 40c is not limited, but in the example shown in FIG. 2, the image irradiation unit 40 includes a light source unit, a half-wave plate, and a polarizer. The image irradiation units 40a, 40b, and 40c irradiate the diffraction grating unit 10 with light through mirrors, bandpass filters, and the like. The light source unit preferably uses a laser light source, and an image forming unit (not shown) is irradiated with laser light emitted from the light source unit to form the first image, the second image, and the third image into the first light, the second light, and the third image. Include in the third 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 .

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 perspective view showing an enlarged light incident portion 22 of the image projection device according to this embodiment. The dashed arrows shown in the drawing indicate the path of the first light LR, the two-dot chain line indicates the path of the second light LG, and the one-dot chain line indicates the path of the third light LB.

The first light LR, the second light LG, and the third light LB emitted from the image irradiation units 40a, 40b, and 40c reach the diffraction grating unit 10 at different incident angles. In the diffraction grating section 10, 0th-order light T1, −1st-order light T2, +1st-order light I1, and −2nd-order light I2 are taken out as diffracted light according to the incident angles of the first light, the second light, and the third light. , enter the light entrance portion 22 .

Here, since the incident angle of the diffracted 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, +1st order light I1 and The inclination angle of the light incident portion 22 is set so that any one of the -secondary light I2 satisfies the total reflection condition on both surfaces of the optical waveguide portion 21 . As an example, the first light LR and the second light LG are arranged so that the +1st order light I1 of each of the first light LR, the second light LG and the third light LB is incident on the light incident portion 22 at the same angle. , the incident angle of the third light LB to the diffraction grating section 10 is set.

Among the diffracted lights of the first light LR, the second light LG, and the third light LB diffracted by the diffraction grating section 10 , those that satisfy the total reflection condition of the optical waveguide section 21 are totally reflected within the optical waveguide section 21 . propagates as guided light. At this time, as shown in FIGS. 2 and 3, the first guided light, the second guided light, and the third guided light enter the optical waveguide section 21 from the same position of the light incident section 22, travel at the same angle, and travel in the same direction. Since the total reflection is repeated at the position, the light reaches the same position of the light emitting section 23 along the same path.

The first guided light, the second guided light, and the third guided light that have reached the light emitting portion 23 are emitted from the light emitting portion 23 to the outside, and project the first image, the second image, and the third image, respectively. As shown in FIGS. 2 and 3, the first guided light, the second guided light, and the third guided light travel through the optical waveguide section 21 along the same path and at the same angle to reach the light exit section 23. The second image and the third image are irradiated from the light emitting section 23 at the same angle. Therefore, the first image, the second image, and the third image are superimposed and projected on the same position on the screen, and a color image using red light, green light, and blue light can be projected. As in the present embodiment, by displaying an image with light of multiple wavelengths, the image of the display content indicating a warning is projected in red, and the image of the display content to give a calm atmosphere or a refreshing feeling is projected in blue or green. It is also possible to obtain a color psychology effect, such as by projecting with

Among the first light LR, the second light LG, and the third light LB diffracted by the diffraction grating section 10, the diffracted light that does not satisfy the total reflection condition in the optical waveguide section 21 is emitted from the second light emitting section of the optical waveguide section 21. taken out from the Here, since the optical filter 31 is provided in the second light emitting portion, only the light of the wavelength selected from the first light LR, the second light LG, and the third light LB is transmitted through the optical filter 31. is removed to the outside. Further, when the optical shutter section 32 is in the transmission state, the light transmitted through the optical filter 31 is irradiated to the outside and an image is projected. When the optical shutter section 32 is in the blocked state, the light transmitted through the optical filter 31 is blocked by the optical shutter section 32 and no image is projected.

In the example shown in FIG. 2, an optical filter 31 and an optical shutter section 32 are provided in the second light emitting section to select light emitted from the second light emitting section to the outside. All of the first light LR, the second light LG, and the third light LB may be emitted to the outside from the second light emitting section without providing the shutter section 32 . In addition, although FIG. 2 shows an example in which the light emitting portion 23 has a flat surface, the light emitting portion 23 is formed in a concave shape or a convex shape to function as a lens so that the first light LR, the second light LG, The spread angle of the third light LB may be adjusted.

4A and 4B are photographs showing paths of light when a laser beam is incident on the light guide plate portion 20. FIG. 4A shows the path of red light, and FIG. 4B shows the path of green light. FIG. 4(c) shows paths when red light and green light are incident simultaneously. The bright lines in FIGS. 4A and 4B indicate the path of the light, and the total reflection is repeated at the interface of the optical waveguide 21, and the light travels from the light entrance portion 22 to the light exit portion 23. Laser light is arriving. Further, as shown in FIG. 4C, the incident positions and incident angles of the red light and the green light in the light incident portion 22 are the same, and the paths in the optical waveguide portion 21 are also overlapped.

As described above, in the image projection apparatus of the present embodiment, the first light LR, the second light LG, and the third light LB are made incident on the diffraction grating section 10 at different angles of incidence, and the first light LR and the second light LG , the third light LB is totally reflected by the optical waveguide section 21 and guided to the light emitting section 23, so that the optical members can be simplified and the size and weight can be reduced. In addition, since the light emitted from the light emitting portion 23 is emitted from the same position at the same angle, it is not necessary to align the optical axes of the optical members even when light beams of a plurality of wavelengths are superimposed. However, when the waveguide distance in the optical waveguide section 21 is long, or when the optical waveguide section 21 is configured with a free-form surface, it is conceivable that the emission position of each light in the light emission section 23 may shift. The optical path of each light may be adjusted according to the shape and size of the light guide plate section 20 . Also, the optical paths may be adjusted in consideration of the possibility that the lights may optically interfere with each other. Further, it is also possible to irradiate the light that does not satisfy the total reflection condition in the optical waveguide section 21 to the outside from the second light emitting section to perform various image projections.

(Second embodiment)
Next, a second 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. 5 is a schematic diagram showing the structure 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. In addition, the area hatched with oblique lines in the drawing indicates the area irradiated with the irradiation light LW. 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. 5, the image projection device includes one diffraction grating section 10, two light guide plate sections 20, an image irradiation section 40, and an external screen 60. As shown in FIG. A viewer wearing the image projection device visually recognizes the direction of the light guide plate 20 and the external screen 60 with both eyes from two viewpoints 70 . 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, and a light emitting portion 23, respectively.

The external screen 60 is a portion on which the light emitted from the light guide plate portion 20 is projected to display an image. The material forming the external screen 60 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. The example shown in FIG. 5 shows an example in which the external screen 60 is provided separately from the image projection device. By fixing, the relative positional relationship between the external screen 60 and the light guide plate section 20 may be maintained.

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. Also, the two light guide plate portions 20 are flat plates and arranged in a V shape. In FIG. 5, the image irradiation units 40a, 40b, and 40c of the first embodiment are collectively shown as the image irradiation unit 40. However, the first light LR, the second light LG, and the third light LB of a plurality of wavelengths are different incidences. The diffraction grating section 10 is irradiated at an angle. In this embodiment, the plurality of image irradiation units included in the image irradiation unit 40 respectively correspond to the first image irradiation unit and the second image irradiation unit in the present invention.

As in the first embodiment, the first light LR, the second light LG, and the third light LB are incident on the diffraction grating section 10 from the image irradiation section 40, and the first light LR, the third light LR, and the third light LB are diffracted by the diffraction grating section 10. The diffracted lights of the second light LG and the third light LB enter the optical waveguide section 21 from the light incident section 22 of each light guide plate section 20 .

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 drawing. 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. 5, 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.

The first guided light, the second guided light, and the third guided light guided in the two light guide plate portions 20 are irradiated as the irradiation light LW from the respective light emitting portions 23, and the first image, the second image, and the A projected image is displayed by superimposing the third image on the external screen 60 .

As described above, in the image projection apparatus of this embodiment, by providing the common diffraction grating section 10 for the two light guide plate sections 20, the projection image can be visually recognized with both eyes of the viewer. Further, in the image projection apparatus of this embodiment as well, it is possible to simplify the optical members and reduce the size and weight.

(Modification of Second Embodiment)
Next, a modified example of the second 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. 6 is a schematic diagram showing the structure of an image projection device according to a modification of the second embodiment. Solid-line arrows and dashed-line arrows shown in the figure schematically indicate paths of light. This modification differs from the second embodiment in that the two light guide plate portions 20 have curved surfaces.

In the example shown in FIG. 6, 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.

In the example shown in FIG. 6, the two light guide plate portions 20 have a curved surface shape along the direction of the viewpoint 70, but the incident angle of the first light from the diffraction grating portion 10 to the light incident portion 22 is the diffraction condition , it is possible to design the light guide plate portion 20 so as to repeat total reflection along the curved surface. In FIG. 6, the left and right light guide plate portions 20 are drawn in a line-symmetrical shape. Depending on whether the diffracted light is guided light or not, the inclination angle of the light incident part 22 may be different between the left and right sides.

In this modified example, similarly to the second embodiment, it is possible to visually recognize projected images superimposed and displayed on the external screen 60 from the positions of the two viewpoints 70 .

(Third embodiment)
Next, a third 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. 7 is a schematic diagram showing the structure 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. As shown in FIG. 7 , the image projection apparatus of this embodiment includes a diffraction grating section 10 , a light guide plate section 20 , an image irradiation section 40 , a digital mirror device 71 and a reflection mirror section 72 . A viewer wearing the image projection device visually recognizes the direction of the reflecting mirror section 72 from the viewpoint position. The image projection device of this embodiment is a wearable HUD in the shape of eyeglasses, and uses the light guide plate section 20 as a temple of the eyeglasses and the reflecting mirror section 72 as a lens. Although only the left half is shown in FIG. 7, images can be projected to both eyes by providing a similar structure symmetrically.

The digital mirror device 71 has a plurality of micromirrors, and each micromirror can individually change the angle of reflection. It is a member that reflects light. The reflecting mirror section 72 is a member that guides the light including the image reflected by the digital mirror device 71 and reflects the light in the viewing direction. FIG. 7 shows a part of the spectacle lens as the reflecting mirror section 72, but the shape and position are not limited as long as the light from the digital mirror device 71 can be reflected toward the viewpoint.

The image irradiation unit 40 includes a laser light source that irradiates the first light LR, the second light LG, and the third light LB, and causes the respective lights to enter the diffraction grating unit 10 at different incident angles. In the example shown in FIG. 7, a digital mirror device 71, which is an image forming unit, is provided separately from the image irradiation unit 40, and an image is included in the light emitted from the light guide plate unit 20. An image forming unit may be provided. In this embodiment, the plurality of laser light sources included in the image irradiation section 40 respectively correspond to the first image irradiation section and the second image irradiation section of the invention.

In this embodiment as well, the first light LR, the second light LG, and the third light LB emitted from the image irradiation unit 40 are incident on the diffraction grating unit 10 at different incident angles, and part of the diffracted light is incident on the diffraction grating unit 10. They enter the optical waveguide section 21 at the same angle from the same position on the section 22 . Further, the diffracted lights of the first light LR, the second light LG, and the third light LB satisfy the total reflection condition of the optical waveguide section 21 , repeat total reflection within the optical waveguide section 21 , and reach the light emitting section 23 . reach. The guided light reaching the light emitting portion 23 is emitted from the light guide plate portion 20 and reflected by the digital mirror device 71 . At this time, the minute mirrors included in the digital mirror device 71 have their reflection angles controlled based on the image information, and the light reflected by the digital mirror device 71 includes an image. The light reflected by the digital mirror device 71 is re-reflected in the direction of the viewpoint by the reflecting mirror section 72, and an image is projected onto the viewpoint.

As shown in FIGS. 2 and 3, the first light LR, the second light LG, and the third light LB are totally reflected in the light guide plate section 20 at the same position and angle, so that they are emitted from the light emitting section 23. The irradiation light is reflected by the digital mirror device 71 and the reflection mirror section 72 and reaches the viewpoint along the same path. Therefore, the first image, the second image, and the third image included in the first light LR, the second light LG, and the third light LB are superimposed and incident on the viewpoint, and a color image can be visually recognized. Here, by using well-known time-division driving for image display by the digital mirror device 71, the timing of light irradiation of each color and image formation are synchronized, and the contents of the first image, the second image, and the third image are respectively displayed. can be different. Further, by using PWM (Pulth Width Modulation) for driving the digital mirror device 71 and the image irradiation unit 40, it is possible to perform gradation display with light of each color.

As described above, also in the image projection apparatus of this embodiment, the first light LR, the second light LG, and the third light LB are made incident on the diffraction grating section 10 at different angles of incidence, and the first light LR, the second light LG, Since the third light LB is totally reflected by the optical waveguide section 21 and guided to the light emitting section 23, it is possible to simplify the optical members and reduce the size and weight. In addition, since the light emitted from the light emitting portion 23 is emitted from the same position at the same angle, it is not necessary to align the optical axes of the optical members even when light beams of a plurality of wavelengths are superimposed.

(Fourth embodiment)
Next, a fourth embodiment of the present invention will be described with reference to FIGS. 8 and 9. FIG. The description of the content that overlaps with the first embodiment is omitted. FIG. 8 is a schematic diagram showing the structure of the image projection device according to this embodiment. As shown in FIG. 8, the image projection device includes a diffraction grating section 10, a light guide plate section 20, image irradiation sections 40a and 40b, an image irradiation section 50, an external screen 60, and a diffraction grating section 80. . A viewer wearing the image projection device visually recognizes the direction of the light guide plate section 20 and the external screen 60 from the position of the viewpoint.

As shown in FIG. 1, the diffraction grating sections 10 and 80 are optical elements having a plate-like portion 11, convex portions 12, concave portions 13, and covering portions, and are formed separately from the light guide plate portion 20. there is 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 light emitting portion 23 , an optical filter 31 , and an optical shutter portion 32 . , a projection lens 33 .

The image irradiation section 50 is a device that irradiates the diffraction grating section 10 with light for projecting an image, and is provided as a separate structure from the image irradiation sections 40a and 40b. The wavelengths of the first light and second light emitted by the image irradiation units 40a and 40b and the third light emitted by the image irradiation unit 50 are different. For example, the first light is red light and the second light is blue light. The light, the third light, is green light. Further, the diffracted light diffracted by the diffraction grating section 10 of the third light emitted by the image irradiation section 50 does not satisfy the total reflection condition of the light guide plate section 20 . Part of the light diffracted by the diffraction grating section 10 among the first light and the second light emitted by the image irradiation sections 40 a and 40 b satisfies the total reflection condition of the light guide plate section 20 .

The third light irradiated from the image irradiation unit 50 is diffracted by the diffraction grating unit 10, passes through the optical waveguide unit 21, is irradiated onto the external screen 60 as irradiation light LV, and projects a projected image onto the external screen 60. Project. The projection lens 33 is an optical member for enlarging the light diameter of the irradiation light LV extracted from the second light emitting section and projecting it onto the external screen 60 . Although one lens is shown as the projection lens 33 in FIG. 8, the projection lens 33 may be configured by combining a plurality of lenses. FIG. 8 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 60, but by using an optical member such as a separate lens, it is possible to project the irradiation light LV onto the entire external screen 60. It is also possible to illuminate the illumination light LV and project the image over the entire external screen 60 so as to cover the entire field of view.

FIG. 9 is a schematic perspective view showing an enlarged light emitting section 23 of the image projection device according to this embodiment. The diffraction grating section 80 is arranged in the light emitting section 23, and is an optical member that opens the waveguided light emitted from the light emitting section 23 and extracts it to the outside. In the example shown in FIGS. 8 and 9, the convex portions 12 and concave portions 13 of the diffraction grating portion 80 have the same shape as that of the diffraction grating portion 10, and the uneven portions of the diffraction grating portion 10 and the diffraction grating portion 80 are parallel to each other. are placed in In the diffraction grating section 10 , the projections 12 and the recesses 13 are arranged to face the light entrance section 22 , but in the diffraction grating section 80 , the plate-like portion 11 is arranged to face the light exit section 23 . .

The first light and the second light that have entered the optical waveguide section 21 are totally reflected at the same position in the optical waveguide section 21 at the same angle and reach the light emitting section 23 . A diffraction grating section 80 is provided in the light emitting section 23, and the first light and the second light are diffracted by the diffraction grating section 80, and the first and second output diffracted lights are formed at different diffraction angles. taken out in the viewing direction. At this time, the guided light that has propagated through the optical waveguide section 21 is diffracted by the diffraction grating section 80 and is taken out as imaging light in the direction of the viewpoint while the light diameter increases. Therefore, the diffracted lights of the first light and the second light diffracted by the diffraction grating section 80 travel with their light diameters increasing until they reach the viewpoint. As a result, from the viewpoint, the aerial images A1 and A2 appear to be formed in the space between the diffraction grating section 80 and the external screen 60 . Here, the planes forming the aerial images A1 and A2 are tilted and non-parallel to each other according to the angles of the first and second output diffracted lights, as shown in FIG. The aerial images A1 and A2 are formed circumferentially around the diffraction grating section 80, and a plurality of aerial images A1 and A2 can be arranged and displayed in a dome shape.

Further, by ensuring the distance between the external screen 60 and the diffraction grating section 80, the image V1 projected on the external screen 60 by the irradiation light LV from the second light emitting section and the image formed by the imaging light L1 and L2 are formed. The aerial images A1 and A2 can be visually recognized at the same time. In the examples shown in FIGS. 8 and 9, the structures of the diffraction grating section 10 and the diffraction grating section 80 are the same. The imaging direction and imaging position may be set to appropriate positions.

In the image projection apparatus of the present embodiment, a part of the first light and a part of the second light are diffracted by the diffraction grating section 80 provided in the light emitting section 23 to produce the first output diffracted light and the second output diffracted light. The light is irradiated in the viewing direction at different emission angles. Thereby, the aerial images A1 and A2 can be formed at different angles and positions with the first output diffracted light and the second output diffracted light. Further, the third light from the image irradiation section 50 can be projected from the second light emission section onto the external screen 60, and the image V1 and the aerial images A1 and A2 can be superimposed and visually recognized.

As described above, in the image projection apparatus of this embodiment as well, the first light and the second light are made incident on the diffraction grating section 10 at different angles of incidence, and the first light and the second light are totally reflected by the optical waveguide section 21. Since the light is guided up to the light emitting portion 23, it is possible to simplify the optical members and reduce the size and weight.

(Fifth embodiment)
Next, a 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. 10 is a schematic diagram showing the structure 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. In this embodiment, two curved light guide plate portions 20 are provided, and a common diffraction grating portion 10 is arranged facing the light incident portion 22 provided in each of the light guide plate portions 20 .

As shown in FIG. 10, the image projection device includes one diffraction grating section 10, two light guide plate sections 20, an image irradiation section 40, an image irradiation section 50, an external screen 60, and a diffraction grating section 80. ing. A viewer wearing the image projection device visually recognizes the direction of the light guide plate 20 and the external screen 60 with both eyes from two viewpoints 70 .

In the example shown in FIG. 10, 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 and the second light guided through the two light guide plate portions 20 are diffracted by the diffraction grating portions 80 provided in the respective light emitting portions 23 to form the first emitted diffracted light and the second emitted diffracted light. , and form aerial images A1 and A2. In addition, the third light emitted from the image irradiation unit 50 is irradiated onto the external screen 60 as irradiation light LV to project an image.

As described above, in the image projection apparatus of the present embodiment, the two light guide plate portions 20 are provided with the common diffraction grating portion 10, and the light exit portion 23 is provided with the diffraction grating portion 80. The aerial images A1 and A2 can be visually recognized by pressing. Further, in the image projection apparatus of this embodiment as well, it is possible to simplify the optical members and reduce the size and weight.

(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. 11 is a schematic diagram showing the structure of an image projection device according to a modification of the fifth 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. In this embodiment, two flat plate-like 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 of the light guide plate portions 20 .

As shown in FIG. 11, the image projection device includes one diffraction grating section 10, two light guide plate sections 20, an image irradiation section 40, an image irradiation section 50, an external screen 60, and a diffraction grating section 80. ing. A viewer wearing the image projection device visually recognizes the direction of the light guide plate 20 and the external screen 60 with both eyes from two viewpoints 70 .

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 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.

The first light and the second light guided through the two light guide plate portions 20 are diffracted by the diffraction grating portions 80 provided in the respective light emitting portions 23 to form the first emitted diffracted light and the second emitted diffracted light. , and form aerial images A1 and A2. In addition, the third light emitted from the image irradiation unit 50 is irradiated onto the external screen 60 as irradiation light LV to project an image.

In this modified example, as in the fifth embodiment, the two light guide plate portions 20 are provided with a common diffraction grating portion 10, and the light emitting portion 23 is provided with a diffraction grating portion 80. The aerial images A1 and A2 can be visually recognized by pressing. Further, in the image projection apparatus of this embodiment as well, it is possible to simplify the optical members and reduce the size and weight.

(Sixth embodiment)
Next, a sixth embodiment of the invention will be described with reference to FIG. The present embodiment differs from the fourth embodiment in the arrangement of the diffraction grating section 80, and the description of the contents overlapping with the fourth embodiment will be omitted. 12A and 12B are schematic perspective views showing the arrangement of the diffraction grating section 10 and the diffraction grating section 80 according to the embodiment. FIG. 12A shows the diffraction grating section 10, and FIG. 12B shows the diffraction grating section 80. showing. FIG. 13 is a schematic diagram showing a structural example of the image irradiation unit 40 of the image projection device according to this embodiment.

As shown in FIGS. 12A and 12B, the uneven portion of the diffraction grating portion 10 extends along the x-axis direction (vertical direction in the drawing), and the uneven portion of the diffraction grating portion 80 extends along the y-axis direction (vertical direction in the drawing). left-right direction), and the uneven portions are arranged so as to be orthogonal to each other.

Also, the first light LR and the second light LB incident on the diffraction grating section 10 have different angles with respect to the z-axis in the yz plane, and are incident on the diffraction grating section 10 at different incident angles. As described in the first embodiment, the diffracted lights of the first light LR and the second light LB are diffracted in the same direction in the diffraction grating section 10, and the first light LR and the second light LB are diffracted in the optical waveguide section 21. LB propagates through total internal reflection on the same path.

The guided lights of the first light LR and the second light LB that have propagated through the optical waveguide section 21 are incident at the same position and at the same angle on the diffraction grating section 80 provided in the light emitting section 23 . Since the response portion of the diffraction grating section 80 extends along the y-axis direction, the first light LR and the second light LB diffracted by the diffraction grating section 80 are separated in the xz plane and travel in the viewing direction. Aerial images A1 and A2 are separately formed in the vertical direction.

As shown in FIG. 13, the image irradiation unit 40 includes a light source unit 41, a beam splitter 42, polarizers 43a and 43b, a chopper 44, lenses 45 and 47, an aperture 46, mirrors M1, M2 and M3. It has It is preferable that the light source unit 41 uses a laser light source.

The laser light emitted from the light source unit 41 is split by the beam splitter 42, one enters the polarizer 43a, the other enters the polarizer 43b after being reflected by the mirror M1, and the changing directions are orthogonal to each other. adjusted. The laser light incident on the polarizers 43 a and 43 b passes through the chopper 44 . By passing the laser light through the chopper 44, when one laser light passes, the other laser light is blocked, and the light is switched on/off complementarily. That is, the polarization direction of each laser beam is maintained even after passing through the chopper 44 . After that, the two laser beams are coaxially overlapped in the multiplexing section, the beam diameter and the spread angle are adjusted through the lens 45, the aperture 46, and the lens 47, and the beam is reflected by the mirror M3 and emitted to the outside. .

As described above, in the image projection apparatus of the present embodiment, by arranging the uneven portions of the diffraction grating section 10 and the diffraction grating section 80 orthogonally, the aerial images A1 and A2 are vertically divided and formed. be able to.

(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, TiO ₂ and SiO ₂ were used as materials for forming the diffraction gratings 10 and 80. However, a nonlinear optical crystal may be used as a second harmonic generation element (SHG). generation) may be configured. Materials for nonlinear optical crystals include, for example, KTP crystals, LBO crystals, CLBO crystals, and the like.

By using a nonlinear optical crystal for the diffraction grating sections 10 and 80, it is also possible to adjust the incident angle and phase of the laser light to perform wavelength conversion and make the wavelength of the emitted light variable.

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, 80... Diffraction grating part 11... Flat part 12... Convex part 13... Concave part 20... Light guide plate part 21... Optical waveguide part 22... Light entrance part 23... Light emission part 31... Optical filter 32... Optical shutter part 33... Projection lens 40, 40a, 40b, 40c, 50 Image irradiation unit 41 Light source unit 42 Beam splitter 43a, 43b Polarizer 44 Chopper 45, 47 Lens 46 Aperture 60 External screen 70 Viewpoint 71 Digital Mirror device 72...reflecting mirror section

Claims (9)

a first image irradiation unit that emits the first light;
a second image irradiation unit that emits the second light;
a first light incident portion into which the first light and the second light are incident; and a portion of the first light and a portion of the second light that are guided as first guided light and second guided light, respectively. a light guide plate portion having an optical waveguide portion and a first light emitting portion for emitting the first guided light and the second guided light;
A first diffraction grating section provided in the first light incident section,
the angles of incidence of the first light and the second light with respect to the first diffraction grating section are different;
An image projection apparatus, wherein part of the first light and part of the second light diffracted by the first diffraction grating satisfy total reflection conditions of the optical waveguide. The image projection device according to claim 1,
The first waveguide light and the second waveguide light are characterized in that the incident position in the first light entrance section, the reflection position in the optical waveguide section, and the exit position in the first light exit section are substantially the same. image projection device. The image projection device according to claim 1 or 2,
The light guide plate portion includes a second light emitting portion that transmits one of the lights split by the first diffraction grating portion and emits the light toward the external screen,
The image projection apparatus, wherein the first light emitting section emits the first guided light and the second guided light toward the external screen. The image projection device according to claim 1 or 2,
Equipped with a digital mirror device having a plurality of minute mirrors controlled based on image information,
The image projection apparatus according to claim 1, wherein the first guided light and the second guided light emitted from the first light emitting section are reflected in a viewing direction via the digital mirror device. The image projection device according to claim 1 or 2,
A second diffraction grating section provided in the first light emitting section,
The second diffraction grating section diffracts a part of the first waveguide light and a part of the second waveguide light, respectively, and irradiates them as first and second emitted diffracted lights at different emission angles in a viewpoint direction. An image projection device characterized by: The image projection device according to claim 5,
An image projection apparatus, wherein the first diffraction grating and the second diffraction grating are arranged parallel or perpendicular to each other. The image projection device according to any one of claims 1 to 6,
comprising two said light guide plate portions,
An image projection apparatus, wherein one of the first diffraction grating sections 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 7,
The first diffraction grating section has a flat plate-like portion forming a light incident surface, and an uneven portion formed integrally with the flat plate-like 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 8,
The image projection apparatus, wherein the first grating part constitutes a wavelength conversion element.

Images