Image display device

Abstract

To provide an image display device capable of achieving both downsizing and a wider viewing angle.SOLUTION: An image display device comprises: a light source (11); an image generation element (20) converting light from the light source (11) into image light; a light guide element (10) guiding the image light to the pupil of an observer; and a light guide part (21) guiding the image light to the light guide element (10). A distance between an emission surface (13a) of the image generation element for emitting image light and an incidence surface (21a) of the light guide part for receiving the image light is longer than 0 mm and equal to or less than 5 mm.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an image display device that allows an observer to view an image.

Background Art

[0002] Conventionally, an image display device including a light guide plate is known. FIG. 18 is a schematic diagram of a light beam propagating inside the light guide plate in a conventional image display device. The light beam from the image generating element enters the first deflecting unit 1, is deflected, and then propagates inside the light guide plate 3 by total reflection. Part of the light beam that has entered the second deflecting unit 2 is deflected toward the observer's pupil SP, and the other part is reflected, propagates inside the light guide plate 3 by total reflection, and enters the second deflecting unit 2. With such a configuration, a plurality of light beams are emitted from the second deflecting unit 2, and the area where the observer can view the light beams is expanded. Patent Document 1 discloses a configuration in which a light guide plate is disposed between MEMS (Micro Electro Mechanical Systems) and an optical system in order to reduce the size of the image display device.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of Invention

Problems to be Solved by the Invention

[0004] However, although Patent Document 1 discloses that the image display device is to be reduced in size, it does not disclose conditions for achieving a wide viewing angle. If the interval between the MEMS and the light guide plate is not set appropriately, the field of view will become extremely narrow.

[0005] An object of the present invention is to provide an image display device that can achieve both size reduction and a wide viewing angle.

Means for Solving the Problems

[0006] An image display device as one aspect of the present invention comprises a light source, an image generation element that converts light from the light source into image light, a light guide element that guides the image light to the observer's pupil, and a light guide section that guides the image light to the light guide element. The image generation element is arranged to face a second surface opposite to the first surface of the light guide element. Light from the light source enters the first surface, passes through the light guide element and the light guide section, and enters the image generation element, where it is converted into image light. This image light passes through the light guide section and enters the second surface. The distance between the emission surface of the image generation element that emits image light and the incidence surface of the light guide section into which the image light enters is greater than 0 mm and less than or equal to 5 mm. Furthermore, when InW is the length of the light guide element in the direction in which the image light propagates through the incident surface, d is the length of the light guide element in the direction perpendicular to the incident surface, and nd is the refractive index of the light guide element at line d, 2×d×tan(asin(1 / nd)) / InW≧0.25 The following condition is satisfied It is characterized by the following: [Effects of the Invention]

[0007] According to the present invention, it is possible to provide an image display device that can achieve both miniaturization and a wide viewing angle. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic diagram of an example of an image display device according to an embodiment of the present invention. [Figure 2] This is an explanatory diagram of the optical path in the image display device of Example 1. [Figure 3] This is a diagram showing the configuration of the image display device in Example 1. [Figure 4] This diagram shows the structure of MEMS. [Figure 5] This is a diagram showing the configuration of the incident deflection mechanism. [Figure 6] This is a diagram showing the configuration of the light source. [Figure 7] This diagram shows the light distribution characteristics of the light-emitting part. [Figure 8] This is an explanatory diagram of the diffraction propagation conditions. [Figure 9] This figure shows the diffraction propagation conditions. [Figure 10] This diagram shows the structure of MEMS. [Figure 11] This is a diagram showing the arrangement of the waveplates. [Figure 12] This is a diagram showing the relationship between the incident deflection unit and the incident light beam. [Figure 13] This is a configuration diagram of the image display device of Example 2. [Figure 14] This is a configuration diagram of the image display device of Example 3. [Figure 15] This is a configuration diagram of the image display device of Example 4. [Figure 16] This is a diagram showing the incident angle characteristics of the incident deflection unit. [Figure 17] This is a configuration diagram of the image display device of Example 5. [Figure 18] This is a schematic diagram of a light beam propagating inside a light guide plate of a conventional example. [Mode for Carrying Out the Invention]

[0009] Hereinafter, examples of the present invention will be described in detail with reference to the drawings. In each drawing, identical members are assigned identical reference numerals, and duplicate descriptions are omitted.

[0010] Figure 1 is a schematic diagram of an example of an image display device according to an embodiment of the present invention. The image display device of this embodiment includes a light guide plate (light guide element) 10, a frame 900, a first acquisition unit 910, a second acquisition unit 920, a control unit 930, and an image generation element (not shown). The image display device allows an observer 1000 to visually recognize a display image 1100 via the light guide plate 10.

[0011] The first acquisition unit 910 is, for example, an imaging device such as a camera, and acquires at least one of position information and viewpoint information of the observer 1000. The position information of the observer 1000 is information related to the position of at least a part of the user, for example, information related to the position of the pupil SP of the observer 1000. Further, the viewpoint information of the observer 1000 is information related to the viewpoint and line of sight of the observer 1000, for example, information related to the movement of the user's pupil SP. The first acquisition unit 910 can detect the deviation amount of the position of the observer's pupil SP relative to the image generation element by acquiring the position information of the user. The control unit 930 can correct the relative position deviation between the image generation element and the pupil SP of the observer 1000 based on the information acquired by the first acquisition unit 910.

[0012] The second acquisition unit 920 is, for example, an imaging device such as a camera, and acquires external world information (surrounding information). The second acquisition unit 920 can detect the brightness of the external world by acquiring the external world information. The control unit 930 can display a display image 1100 with appropriate luminance for the observer 1000 based on the information acquired by the second acquisition unit 920. Note that the brightness of the display image 1100 can also be arbitrarily determined by the observer 1000 operating the control unit 930, regardless of the information acquired by the second acquisition unit 920.

[0013] The image generation element converts light from a light source into image light. The image generation element may be arranged for each eye, or may be arranged for one eye. When the image generation element is arranged for each eye, it is also possible to give parallax to the display image and allow the observer 1000 to stereoscopically view the display image 1100.

[0014] Note that the control unit 930 may be disposed outside the frame 900, or may be disposed inside the frame 900. When disposed outside the frame 900, the connection between the control unit 930 and the frame 900 may be wired or wireless. [Examples]

[0015] Figure 2 is a configuration diagram of the image display device of this embodiment. Figure 3 is an explanatory diagram of the optical path in the image display device of this embodiment. The image display device of this embodiment includes a light guide plate 10, a light source 11, a λ / 4 wave plate 12, an incident deflection means (light guide section) 21, an exit deflection means 22, and MEMS (Micro Electro Mechanical Systems) 20. In this embodiment, the incident deflection means 21 and the exit deflection means 22 are coupled to the light guide plate 10.

[0016] The λ / 4 waveplate 12 is a waveplate that imparts a phase difference of λ / 4. The MEMS 20 includes a reflector 13 that reflects incident light and an outer casing (protective member) 14 for protecting the reflector 13. As shown in Figure 4, it is a two-dimensional scanning mirror of raster scanning type in which the reflector 13 swings around the x and y axes with the center of the reflector 13 as its axis. The light beam emitted from the light source 11 passes through the light guide plate 10, the incident deflection means 21, and the λ / 4 waveplate 12 and enters the MEMS 20. In this embodiment, the MEMS 20 is used as an example of an image generation element, but other elements may be used.

[0017] The light beam (image light) emitted from the MEMS 20 is deflected by the incident deflection means 21 and propagates through the inside of the light guide plate 10 by total internal reflection. The light beam incident on the light beam splitting deflection means 10a provided on the light guide plate 10 is deflected while being split in the x-axis direction and guided to the exit deflection means 22. The light beam incident on the exit deflection means 22 is deflected while being split in the y-axis direction and emitted to the pupil SP. In this embodiment, the direction of deflection by the incident deflection means 21 (x-direction) and the direction of deflection by the light beam splitting deflection means 10a (y-direction) are orthogonal, but each means may deflect the light beam at different angles as long as the light beam incident on the light guide plate 10 can be emitted to the pupil SP.

[0018] Figure 5 is a diagram of the configuration of the incident deflection means 21. The incident deflection means 21 includes a diffracting element having a lattice structure P finer than the wavelength λ of the light beam emitted from the light source 11, as shown in Figures 5(a) to 5(d), and has optical anisotropy due to polarization. In this embodiment, the incident deflection means 21 has the characteristic of transmitting P-polarized light and diffracting S-polarized light (polarization selectivity). In this embodiment, the light beam emitted from the light source 11 is P-polarized, is not diffracted by the incident deflection means 21, and passes through the incident deflection means 21. The efficiency and diffraction angle for each diffraction order can be controlled by changing the shape, height, and refractive index of the lattice structure, and can be determined according to the requirements of the image display device. In addition, although the incident deflection means 21 is a diffracting optical element in this embodiment, it may be a holographic element as long as it has a light beam deflection effect and anisotropy due to polarization.

[0019] P-polarized light that has passed through the incident deflection means 21 is reflected by the reflector 13 and enters the incident deflection means 21 again. Here, the λ / 4 wave plate 12, which is placed between the incident deflection means 21 and the MEMS 20, reverses the phase of the P-polarized light that has passed through the incident deflection means 21 by 90 degrees before it enters the incident deflection means 21 again, becoming S-polarized light. The light beam that enters the incident deflection means 21 again as S-polarized light is diffracted by the incident deflection means 21 and propagates through the light guide plate 10 by total internal reflection.

[0020] Figure 6 is a diagram of the configuration of the light source 11. Figure 7 is a diagram showing the light distribution characteristics of the light-emitting section 15. The light emitted from the light-emitting section 15 is linearly polarized and has different divergence angles in the x-axis and y-axis directions. Therefore, the light beam cross-section (FFP) of the light emitted from the light-emitting section 15 in an xy cross-section perpendicular to the z-axis direction is elliptical. The light emitted from the light-emitting section 15 is parallelized by the collimator lens 16 having the same focal length. As a result, the light source 11 emits a collimated light beam 18 with an elliptical cross-sectional shape, where the x-axis is the minor axis, as shown in Figure 6(c). By using an anamorphic collimator lens system, the light source 11 can emit a collimated light beam with a substantially circular cross-sectional shape.

[0021] Alternatively, a λ / 2 wave plate 17 may be placed behind the collimator lens 16 (on the opposite side from the light-emitting part 15) to control the polarization of the emitted light. In this embodiment, the light beam emitted from the light source 11 is a collimated light beam in the wavelength range of 520 to 540 nm from a semiconductor laser, but it may also be a collimated light beam synthesized from the light beams of red, green, and blue semiconductor lasers. A photonic crystal laser or a light-emitting diode may be used instead of a semiconductor laser.

[0022] The diffraction propagation conditions will be explained below with reference to Figure 8. Figure 8 is an explanatory diagram of the diffraction propagation conditions.

[0023] In this embodiment, when the reflector 13 is tilted by an angle ω when a light beam is incident on it, the light beam (18-, 18+) reflected by the reflector 13 is tilted by an angle 2ω (=θ) with respect to the collimated light beam 18. The separated light beam is incident on the incident deflection means 21 as shown in Figure 8(b). The width φ' of the light beam across the entire field of view separated on the incident deflection means 21 is expressed by the following equation (1).

[0024] φ' = φ + 2 × L × tanθ (1) Here, φ is the diameter of the light beam incident on the reflector 13. L is the distance between the reflecting surface (emission surface) 13a of the reflector 13 that emits image light and the incident surface 21a of the incident deflection means 21 that is incident on it. θ is the emission angle of the image light from the reflector 13. In this embodiment, the distance L is the distance (shortest length) between the center of the reflecting surface 13a and the incident surface 21a of the incident deflection means 21.

[0025] In this embodiment, as shown in Figure 8(b), the width InW of the incident deflection means 21 and the width φ' of the light beam across the entire field of view separated on the incident deflection means 21 are assumed to be the same. Note that when a light beam with a diameter greater than the diameter of the reflective surface (effective diameter) m of the reflector 13 is incident on the reflector 13, the light beam in the region outside the effective diameter m area is not properly guided, so the effective diameter m of the reflector 13 becomes the diameter φ of the light beam incident on the reflector 13.

[0026] As mentioned above, the light beam that is again incident on the incident deflection means 21 is diffracted and propagates through the inside of the light guide plate 10 by total internal reflection. However, when the diffracted light beam is again incident on the incident deflection means 21, it is diffracted again and does not propagate correctly.

[0027] Therefore, in this embodiment, the following condition (2) must be satisfied so that the diffracted light beam does not re-enter the incident deflection means 21.

[0028] D / InW≧0.25 (2) Here, InW is the length of the light guide plate 10 on the incident surface 21a in the direction (x-axis direction) in which the image light propagates. D is the propagation distance of one total internal reflection of the light beam (18-) at the negative angle of view.

[0029] Furthermore, when d is the length of the light guide plate 10 in the direction perpendicular to the incident surface 21a, and θc is the critical angle of the light guide plate 10, the propagation distance D is expressed by the following equation (3).

[0030] D = 2 × d × tanθc (3) Since the critical angle θc is determined by the refractive index nd at the d line (wavelength 587.6 nm) of the light guide plate 10, equation (3) can be expressed as equation (4) below.

[0031] D = 2 × d × tan(asin(1 / nd)) (4) By substituting equation (4) into condition (2), condition (2) can be expressed as the following condition (5).

[0032] 2×d×tan(asin(1 / nd)) / InW≧0.25 (5) As mentioned above, in this embodiment, the width InW of the incident deflection means 21 and the width φ' of the light beam for the entire field of view separated on the incident deflection means 21 are assumed to be the same. Therefore, using equation (1), condition (5) can be transformed into the following condition (6). L≦(2×d×tan(asin(1 / nd))-0.25φ) / (0.5×tanθ) (6) By satisfying condition (6) for distance L, an image display device that achieves both miniaturization and a wide viewing angle can be realized. Specifically, condition (6) can be satisfied if distance L is longer than 0 mm and 5 mm or less. It is desirable that distance L be 4 mm or less, and even more desirable that distance L be 3 mm or less.

[0033] Condition (6) can be further simplified to satisfy the following condition (6a).

[0034] 0 <L / φ≦5 (6a) Even if equation (5) is satisfied, it is possible to propagate the light beam across the entire field of view, but as shown in Figure 9(a), a portion of the diffracted light beam is re-entered by the incident deflection means 21 and is not properly guided. In order to efficiently propagate the light beam, it is desirable to satisfy the following condition equation (7).

[0035] 2×d×tan(asin(1 / nd)) / InW≧0.5 (7) Furthermore, considering uniformity within the pupil SP, it is even more desirable to satisfy the following condition (8).

[0036] 2×d×tan(asin(1 / nd)) / InW≧1.0 (8) As mentioned above, it is desirable that the width InW of the incident deflection means 21 and the width φ' of the light beam for the entire field of view separated on the incident deflection means 21 be the same. However, as shown in Figure 9(b), a portion of the light beam for a certain field of view may be incident on the incident deflection means 21 again and not properly guided, but it is still possible for the light beam to propagate. In that case, it is desirable that the width InW of the incident deflection means 21, the width φ' of the light beam for the entire field of view separated on the incident deflection means 21, and the diameter φ of the light beam incident on the reflector 13 satisfy the following condition (9).

[0037] φ' <InW+2×φ (9) Even if equation (9) is satisfied, it is possible to propagate the light beam across the entire field of view, but as shown in Figure 9(a), a portion of the diffracted light beam is re-entered by the incident deflection means 21 and is not properly guided. In order to efficiently propagate the light beam, it is desirable to satisfy the following condition equation (10).

[0038] φ'≦InW+φ (10) Furthermore, considering uniformity within the pupil SP, it is even more desirable to satisfy the following condition (11).

[0039] φ'≦InW (11) The field of view of the image display device is described below. Since the light beam propagates through the inside of the light guide plate 10 by total internal reflection while preserving the angle, it is necessary to incident the light beam on the incident deflection means 21 at an angle equivalent to the field of view to be obtained with the pupil SP. As shown in equation (1), if the emission angle θ of the light reflected by the reflector 13 increases, the width φ' of the light beam of the entire field of view separated on the incident deflection means 21 increases, making it difficult to satisfy the diffraction propagation conditions. By shortening the distance L between the reflector 13 and the incident deflection means 21, it is possible to suppress the increase in the width φ' of the light beam of the entire field of view separated on the incident deflection means 21 even if the emission angle θ is increased, and the diffraction propagation conditions can be satisfied at a wider angle. This makes it possible to widen the field of view of the image display device. In this embodiment, as shown in Figure 2, the MEMS 20 is arranged to face the second surface 10c of the light guide plate 10, which is opposite the first surface 10b into which the light beam emitted from the light source 11 is incident. Therefore, the light beam emitted from the light source 11 enters the light guide plate 10 from the first surface 10b, passes through the light guide plate 10, the incident deflection means 21, and the λ / 4 wave plate 12, and enters the MEMS 20. This configuration makes it possible to shorten the distance L between the reflector 13 and the incident deflection means 21. In order to prevent light loss, an anti-reflective coating is applied to the first surface 10b of the light guide plate 10, into which the light beam emitted from the light source 11 enters.

[0040] The following describes a more desirable configuration.

[0041] In order to shorten the distance L between the reflector 13 and the incident deflection means 21, it is desirable that the light beam emitted from the light source 11 be incident on the MEMS 20 so as to be perpendicular to the reflective surface of the reflector 13 (including cases where it is substantially perpendicular (approximately perpendicular)). That is, it is desirable that the reflector 13 be positioned such that the reflective surface of the reflector 13 is approximately parallel to the incident surface 21a of the incident deflection means 21 when it is not driven (stationary, not energized). Here, approximately parallel means that the degree of parallelism between the two surfaces is within ±2°. That is, it is sufficient that the inclination angle of the reflective surface of the reflector 13 with respect to the incident surface 21a of the incident deflection means 21 when it is not driven is within ±2°. Also, as shown in Figure 10, when it is not driven, the reflective surface of the reflector 13 and the injection surface or substrate surface 19 of the casing 14 are approximately parallel, so the parallelism between the injection surface or substrate surface 19 of the casing 14 and the incident surface 21a of the incident deflection means 21 may be used.

[0042] Furthermore, it is desirable that the light beam emitted from the light source 11 be incident on the incident deflection means 21 so as to be perpendicular to (including substantially perpendicular (approximately perpendicular)) the incident surface 21b of the incident deflection means 21 that is opposite to the incident surface 21a of the incident deflection means 21. In this embodiment, taking into account the transmittance characteristics of P-polarized light of the incident deflection means 21, the light beam emitted from the light source 11 is configured to be incident on the incident surface 21b of the incident deflection means 21 within a range of ±10° with respect to the normal of the incident surface 21b of the incident deflection means 21.

[0043] Furthermore, it is desirable that the λ / 4 wave plate 12 be thin. The λ / 4 wave plate 12 may be a phase difference plate made of quartz, or it may be a substrate with a film laminated to it. When using a substrate with a film laminated to it, using a material with a high refractive index for the substrate will shorten the air-equivalent length, thus shortening the distance L. Specifically, it is desirable to use a material with a refractive index of 1.5 or higher.

[0044] Furthermore, the λ / 4 wave plate 12 may be held using the outer casing 14, as shown in Figure 11(a). By positioning the λ / 4 wave plate 12 adjacent to the opening of the outer casing 14, it also serves as a cover glass, preventing foreign matter from entering the interior. The λ / 4 wave plate 12 may be bonded to the outer casing 14 with an adhesive, or it may be held by a mechanical component such as a retaining spring, as long as it is positioned adjacent to the opening of the outer casing 14.

[0045] Furthermore, the λ / 4 waveplate 12 may be formed on the reflective surface 13a of the reflector 13, as shown in Figure 11(b). By forming the λ / 4 waveplate 12 on the reflective surface 13a, it becomes unnecessary to arrange a separate optical element, and the distance L can be shortened to its minimum. In this case, the λ / 4 waveplate 12 is configured as a waveplate on a film made of polycarbonate or an olefin resin.

[0046] Furthermore, as shown in Figure 6(c), the cross-sectional shape of the collimated light beam emitted from the light source 11 is elliptical. In this case, if the cross-sectional shape of the light beam incident on the incident deflection means 21 is also elliptical, it is desirable to align the propagation direction (x-axis direction) in which the light guide plate 10 propagates the image light with the minor axis direction of the ellipse, as shown in Figure 12. This makes it possible to reduce the width φ' of the light beam for the entire field of view separated on the incident deflection means 21 compared to a circular light beam, thereby enabling a wider field of view and a smaller width InW of the incident deflection means 21. [Examples]

[0047] This embodiment differs from Embodiment 1 in that the light beam emitted from the light source 11 is deflected once before entering the light guide plate 10. In this embodiment, only the configurations that differ from Embodiment 1 will be described, and the common configurations will not be described.

[0048] Figure 13 is a configuration diagram of the image display device of this embodiment. The image display device of this embodiment has a deflection element 31 in addition to the configuration of Embodiment 1. In this embodiment, the deflection element 31 is a metal mirror, but it may be a dielectric mirror or a PBS (Polarizing Beam Splitter) as long as it can deflect light toward the light guide plate 10.

[0049] In this embodiment, the light beam emitted from the light source 11 is deflected by the deflection element 31 before being incident on the light guide plate 10. In this embodiment, the depth direction (z direction) of the MEMS 20 can be shortened by rotating the light source 11 around the y-axis compared to Embodiment 1.

[0050] Furthermore, as shown in Figure 13(b), a photodetector 32 that monitors information about the light source 11 may be placed on the back surface of the deflection element 31. In this embodiment, the photodetector 32 senses the amount of light, but it may also sense the color. By placing a photodetector 32 that monitors information about the light source 11 and using feedback control, variations in the light source 11 can be reduced and the quality of the displayed image can be improved.

[0051] Furthermore, as shown in Figure 13(c), by considering the reflectivity characteristics of the deflection element 31 and directing the light beam emitted from the light source 11 onto the deflection element 31 as S-polarized light, it is possible to ensure high reflectivity. In this case, a wave plate 33 can be placed between the deflection element 31 and the light guide plate 10. The S-polarized light emitted from the deflection element 31 has its phase rotated by 90° by the wave plate 33 and is incident on the light guide plate 10 as P-polarized light. [Examples]

[0052] This embodiment differs from Embodiment 1 in that the light beam emitted from the light source 11 is deflected twice before entering the light guide plate 10. In this embodiment, only the configurations that differ from Embodiment 1 will be described, and the common configurations will not be described.

[0053] Figure 14 is a diagram showing the configuration of the image display device of this embodiment. The image display device of this embodiment has deflection elements 34 and 35 in addition to the configuration of Embodiment 1.

[0054] In this embodiment, the light beam emitted from the light source 11 is deflected twice by the deflection elements 34 and 35 before entering the light guide plate 10. In this embodiment, by deflecting the light beam emitted from the light source 11 twice, the light source 11 can be housed within the frame 900, thereby enabling miniaturization of the entire device.

[0055] Alternatively, as shown in Figure 14(b), an element 36 having two reflective surfaces may be provided instead of the deflection elements 34 and 35. In this case, deflection can also be achieved by total internal reflection by selecting a glass material with an appropriate refractive index. [Examples]

[0056] This embodiment differs from Embodiment 1 in that the image light from the reflecting mirror 13 of the MEMS 20 is incident on the incident deflection means 21 at an inclination with respect to the normal of the incident surface 21a of the incident deflection means 21. In this embodiment, only the configurations that differ from Embodiment 1 will be described, and the common configurations will not be described.

[0057] Figure 15 is a diagram showing the configuration of the image display device in this embodiment. Figure 16 is a diagram showing the incident angle characteristics of the incident deflection means 21, and shows the diffraction efficiency of the light beam incident on the incident deflection means 21 with respect to the incident angle.

[0058] As shown in Figure 16, if the diffraction efficiency of the incident deflection means 21 is not maximized when the incident angle is 0°, the light can be propagated efficiently within the light guide plate 10 by incidenting the light beam at the incident angle that maximizes the diffraction efficiency. It is not necessary to incident the light at the incident angle that maximizes the diffraction efficiency; it may be incident at an incident angle within ±5° of the incident angle that maximizes the diffraction efficiency. In this case, the optical distance between the reflector 13 and the incident deflection means 21 will be longer than when the image light is incident perpendicularly to the incident surface 21a of the incident deflection means 21. However, by arranging the reflector 13 such that its reflective surface 13a is approximately parallel to the incident surface 21a of the incident deflection means 21 when the reflector 13 is not driven, the increase in the optical distance can be suppressed more effectively than by tilting the entire MEMS 20. Approximately parallel means that the parallelism of the two surfaces is within ±2°. Furthermore, since the reflective surface 13a of the non-driven mirror 13 and the injection surface or substrate surface 19 of the outer casing 14 are substantially parallel, the parallelism between the injection surface or substrate surface 19 of the outer casing 14 and the incidence surface 21a of the incidence deflection means 21 may be used.

[0059] Furthermore, in this embodiment, since the image light emitted from the reflecting mirror 13 is inclined with respect to the normal of the reflecting surface 13a of the reflecting mirror 13, even if the angle of view of the light beam is the same, the light beam incident on the reflecting mirror 13 and the emitted image light do not coincide. In other words, a configuration can be realized in which the incident light beam does not pass through the incident deflection means 21. If it is not necessary to transmit light through the incident deflection means 21, there is no need to control the polarization, and it is not necessary to place the λ / 4 wave plate 12 between the incident deflection means 21 and the MEMS 20. [Examples]

[0060] This embodiment differs from Embodiment 1 in that it uses a spatial light modulator (SLM) instead of a MEMS as the image generation element. In this embodiment, only the configurations that differ from Embodiment 1 will be described, and the common configurations will not be described.

[0061] Figure 17 is a diagram showing the configuration of the image display device of this embodiment. In this embodiment, a spatial phase modulator 37 such as an optical phased array (OPA) is used as the image generation element.

[0062] The spatial phase modulator 37 is a device that modulates (changes) the light beam by electrically controlling the spatial distribution (amplitude, phase, and polarization, etc.) of the light beam emitted from the light source 11. Specifically, by controlling the wavefront shape of the light beam incident on the spatial phase modulator 37 and changing the emission angle of the emitted image light, image light for each field of view can be formed. Note that if the spatial phase modulator 37 can control the polarization, it is not necessary to place a λ / 4 wave plate between the light guide plate 10 and the spatial phase modulator 37.

[0063] Furthermore, as shown in Figure 17(b), if the spatial phase modulator 37 is of the transmissive type, it is not necessary to direct the light beam emitted from the light source 11 into the spatial phase modulator 37 from the side of the light guide plate 10, and the distance between the incident deflection means 21 and the spatial phase modulator 37 can be further shortened.

[0064] Table 1 below summarizes the various values ​​for the configurations that can be taken in each embodiment. Note that n1 is the refractive index of air, and n2 is the refractive index nd of the light guide plate 10 at the d line.

[0065] [Table 1]

[0066] This embodiment includes the following configuration.

[0067] (Composition 1) Light source and An image generation element that converts light from the aforementioned light source into image light, A light guide element that directs the aforementioned image light to the observer's pupil, It has a light guide section that guides the image light to the light guide element, An image display device characterized in that the distance between the emission surface of the image generation element that emits the image light and the incident surface of the light guide that receives the image light is greater than 0 mm and less than or equal to 5 mm. (Configuration 2) When InW is the length of the light guide element in the direction in which the image light propagates from the incident surface, d is the length of the light guide element in the direction perpendicular to the incident surface, and nd is the refractive index of the light guide element along line d, 2×d×tan(asin(1 / nd)) / InW≧0.25 The image display device according to configuration 1, characterized in that it satisfies the following conditional expression. (Composition 3) The image generation element is arranged so as to face a second surface that faces the first surface of the light guide element, The image display device according to configuration 1 or 2, characterized in that light from the light source is incident on the first surface, passes through the light guide element and the light guide portion, is incident on the image generation element to be converted into image light, and the image light passes through the light guide portion and is incident on the second surface. (Composition 4) The image display device according to configuration 3, characterized in that the light guide portion includes a diffraction element having polarization selectivity. (Composition 5) The image display device according to configuration 4, characterized in that the light beam emitted from the light source is incident on the light guide at an incident angle of ±10° or less with respect to the normal of the surface of the light guide facing the incident surface. (Composition 6) The image display device according to configuration 4, characterized in that the image light is inclined with respect to the normal to the incident surface and incident on the incident surface at an incident angle of within ±5° of the incident angle at which the diffraction efficiency of the light guide is maximized. (Composition 7) The image display device according to configuration 3, characterized in that an anti-reflective coating is formed on the first surface. (Composition 8) The image display device according to configuration 3, characterized in that the light beam emitted from the light source is deflected in its optical path and then incident on the light guide element from the first surface. (Composition 9) The system further comprises a λ / 4 wave plate disposed between the second surface and the image generation element, The image display device according to configuration 3, characterized in that a light beam from the light source is incident on the first surface, passes through the light guide element, the light guide portion, and the λ / 4 wave plate, and is incident on the image generation element to be converted into image light, and the image light passes through the λ / 4 wave plate and the light guide portion and is incident on the second surface. (Composition 10) The image display device according to any one of configurations 1 to 9, characterized in that the image generation element is a scanning mirror. (Composition 11) The image generation element includes a reflector and a protective member for protecting the reflector. The image display device according to claim 9, characterized in that the λ / 4 wave plate is held by the protective member. (Composition 12) The aforementioned image generation element includes a reflecting mirror, The image display device according to claim 9, characterized in that the λ / 4 wave plate is formed on the reflecting mirror. (Composition 13) The aforementioned image generation element includes a reflecting mirror, The image display device according to any one of configurations 1 to 12, characterized in that the reflector is arranged such that the inclination angle of the reflecting surface of the reflector with respect to the incident surface is within 2° when no power is applied. (Composition 14) When the diameter of the reflective surface of the scanning mirror that reflects the light beam emitted from the light source is φ, and the distance between the reflective surface and the incident surface is L, 0 <L / φ≦5 The image display device according to configuration 10, characterized in that it satisfies the following conditional expression. (Composition 15) The cross-sectional shape of the light beam incident on the light guide is elliptical. An image display device according to any one of configurations 1 to 14, characterized in that the direction of the short axis of the light beam incident on the light guide portion coincides with the direction in which the light guide element propagates the image light. (Composition 16) An image display device according to any one of configurations 1 to 15, characterized in that the distance between the ejection surface and the incident surface is 4 mm or less. (Composition 17) An image display device according to any one of configurations 1 to 16, characterized in that the distance between the ejection surface and the incident surface is 3 mm or less.

[0068] Although preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of its gist. [Explanation of Symbols]

[0069] 10. Light guide plate (light guide optical element) 11 Light source 13a Reflective surface (output surface) 20 MEMS (Image Generating Elements) 21 Incident deflection means (light guiding section) 21a Incidence plane 37. Spatial Phase Modulator (Image Generation Element)

Claims

1. Light source and An image generation element that converts light from the aforementioned light source into image light, A light guide element that directs the aforementioned image light to the observer's pupil, It has a light guide section that guides the image light to the light guide element, The image generation element is arranged so as to face a second surface that faces the first surface of the light guide element, Light from the light source enters the first surface, passes through the light guide element and the light guide portion, and enters the image generation element, where it is converted into image light, and this image light passes through the light guide portion and enters the second surface. The distance between the emission surface of the image generation element that emits the image light and the incident surface of the light guide that receives the image light is greater than 0 mm and less than or equal to 5 mm. When InW is the length of the light guide element in the direction in which the image light propagates from the incident surface, d is the length of the light guide element in the direction perpendicular to the incident surface, and nd is the refractive index of the light guide element along line d, 2×d×tan(asin(1 / nd)) / InW≧0.25 An image display device characterized by satisfying the following conditional expression.

2. The image display device according to claim 1, characterized in that the light guide portion includes a diffraction element having polarization selectivity.

3. The image display device according to claim 2, characterized in that the light beam emitted from the light source is incident on the light guide at an incident angle of ±10° or less with respect to the normal of the surface of the light guide facing the incident surface.

4. The image display device according to claim 2, characterized in that the image light is inclined with respect to the normal to the incident surface and is incident on the incident surface at an incident angle of within ±5° of the incident angle that maximizes the diffraction efficiency of the light guide.

5. The image display device according to claim 1, characterized in that an anti-reflective coating is formed on the first surface.

6. The image display device according to claim 1, characterized in that the light beam emitted from the light source is deflected in its optical path and then incident on the light guide element from the first surface.

7. The system further comprises a λ / 4 wave plate disposed between the second surface and the image generation element, The image display device according to claim 1, characterized in that the light beam from the light source is incident on the first surface, passes through the light guide element, the light guide portion, and the λ / 4 wave plate, and is incident on the image generation element to be converted into image light, and the image light passes through the λ / 4 wave plate and the light guide portion and is incident on the second surface.

8. The image display device according to claim 1, characterized in that the image generation element is a scanning mirror.

9. The image generation element includes a reflector and a protective member for protecting the reflector. The image display device according to claim 7, characterized in that the λ / 4 wave plate is held by the protective member.

10. The aforementioned image generation element includes a reflecting mirror, The image display device according to claim 7, characterized in that the λ / 4 wave plate is formed on the reflecting mirror.

11. The aforementioned image generation element includes a reflecting mirror, The image display device according to claim 1, characterized in that the reflector is arranged such that the inclination angle of the reflecting surface of the reflector with respect to the incident surface is within 2° when no power is applied.

12. When the diameter of the reflective surface of the scanning mirror that reflects the light beam emitted from the light source is φ, and the distance between the center of the reflective surface and the incident surface is L, 0 < L / φ ≤ 5 The image display device according to claim 8, characterized in that it satisfies the following conditional expression.

13. The cross-sectional shape of the light beam incident on the light guide is elliptical. The image display device according to claim 1, characterized in that the direction of the short axis of the light beam incident on the light guide portion coincides with the direction in which the light guide element propagates the image light.

14. The image display device according to claim 1, characterized in that the distance between the ejection surface and the incident surface is 4 mm or less.

15. The image display device according to claim 1, characterized in that the distance between the ejection surface and the incident surface is 3 mm or less.

Images