Image display device

Abstract

To provide an image display device that, with a simple configuration, can display an image with good resolution.SOLUTION: An image display device has: a light source unit 10; an image creation element 30 that creates an image light beam; a light guide member 20 that emits a light beam from the light source unit toward the image creation element as an illumination light beam while propagating the light beam inside the light guide member; an optical system 50 that guides the image light beam from the image creation element to an observation side or a projection side; and a light distribution angle control element 40 that is arranged between the light guide member and the optical system, and controls the light distribution angle of the image light beam. The divergence angle of the light beam emitted from the light source unit is defined as θ1, the divergence angle of the light beam emitted from the light guide member toward the image creation element as θ2, the divergence angle of the image light beam emitted from the light distribution angle control element as θ3, and 2NA as the capture angle of the optical system as θ4. The conditions of 0.9≤θ2 / θ1≤1.1, θ2<θ3, and 0.2≤θ3 / θ4≤1.5 are satisfied.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an image display device such as a head mounted display or smart glasses. [Background technology]

[0002] Patent Document 1 discloses an image display device in which light from a light source is incident on an image generating element as a backlight with wide light distribution characteristics via a light guiding member, and the light emitted from the image generating element is directed to an observer's pupil or a projection surface via an optical system. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent Publication No. 2020 / 0341194 Summary of the Invention [Problem to be solved by the invention]

[0004] In the image display device of Patent Document 1, an element (diffuser plate) that controls the light distribution angle is disposed between the image generating element and the optical system. As a result, the resolution of the image formed by the light emitted from the optical system decreases. In addition, since the element that controls the light distribution angle is provided in the light guiding member, the configuration becomes complicated.

[0005] The present invention provides an image display device that has a simple configuration but is capable of displaying images with good resolution. [Means for solving the problem]

[0006] An image display device according to one aspect of the present invention includes a light source unit, an image generating element that generates an image light beam by modulating an incident light beam, a light guiding member that propagates the light beam from the light source unit inside and emits a portion of the light beam from a plurality of regions as an illumination light beam toward the image generating element, an optical system that guides the image light beam from the image generating element to an observation side or a projection side, and a light distribution angle control element that is disposed between the light guiding member and the optical system and controls the light distribution angle of the image light beam. When the divergence angle of the light beam emitted from the light source unit is θ1, the divergence angle of the light beam emitted from the light guiding member toward the image generating element is θ2, the divergence angle of the image light beam emitted from the light distribution angle control element is θ3, and 2NA as the capture angle of the optical system is θ4, 0.9≦θ2 / θ1≦1.1 θ2<θ3 0.2≦θ3 / θ4≦1.5 The present invention is characterized in that it satisfies the following conditions.

[0007] According to another aspect of the present invention, there is provided an image display device comprising: a light source unit, an image generating element that generates an image light beam by modulating an incident light beam, a light guiding member that propagates the light beam from the light source unit inside and outputs a portion of the light beam from a plurality of regions as an illumination light beam toward the image generating element, an optical system that guides the image light beam from the image generating element to an observation side or a projection side, and a light distribution angle control element that is disposed between the light guiding member and the image generating element and controls the light distribution angle of at least one of the illumination light beam and the image light beam. When the divergence angle of the light beam emitted from the light source unit is θ1, the divergence angle of the light beam emitted from the light guiding member toward the image generating element is θ2, the divergence angle of the light beam of the illumination light beam and the image light beam that is emitted from the light distribution angle control element toward the optical system is θ3, and 2NA as the acceptance angle of the optical system is θ4, 0.9≦θ2 / θ1≦1.1 θ2<θ3 0.2≦θ3 / θ4≦1.5 An image display system having the above-mentioned image display device and either an eyepiece optical system that guides an image light beam from the image display device to an observer's eye or a projection optical system that projects the image light beam onto a projection surface constitutes another aspect of the present invention. Effect of the Invention

[0008] According to the present invention, it is possible to display an image having a good resolution even with a simple configuration. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing a configuration of an image display device according to a first embodiment. [Diagram 2] FIG. 2 is a diagram showing the configuration of an incident deflection element in the first embodiment. [Diagram 3] 4 is a diagram showing the configuration of another incident deflection element in the first embodiment. [Figure 4] FIG. 13 is a diagram showing the configuration of still another incident deflection element in the first embodiment. [Diagram 5] FIG. 2 is a diagram showing the configuration of an output deflection element in the first embodiment. [Figure 6] FIG. 4 is a diagram showing the characteristics of the dielectric multilayer film in Example 1. [Figure 7] FIG. 4 is a diagram showing another configuration of the image display device according to the first embodiment. [Figure 8] FIG. 2 is a diagram showing the configuration of a light source unit in the first embodiment. [Figure 9] FIG. 4 is a diagram showing the configuration of another light source unit in the first embodiment. [Figure 10] FIG. 13 is a diagram showing the configuration of still another light source unit in the first embodiment. [Figure 11] FIG. 4 is a diagram showing the characteristics of the light distribution angle control element in the first embodiment. [Figure 12] FIG. 2 is a diagram showing the peripheral configuration of an image generating element in the first embodiment. [Figure 13] 4A to 4C are diagrams for explaining the resolution in Example 1. [Figure 14] FIG. 2 is a diagram showing the configuration of the periphery of an image generating element in the image display device according to the first embodiment. [Figure 15] FIG. 2 is a diagram showing an application example of the image display device according to the first embodiment. [Figure 16] FIG. 4 is a diagram showing another application example of the image display device according to the first embodiment. [Figure 17] FIG. 11 is a diagram showing still another application example of the image display device according to the first embodiment. [Figure 18]FIG. 11 is a diagram showing the configuration of an image generating apparatus according to a second embodiment. [Figure 19] FIG. 11 is a diagram showing the peripheral configuration of an image generating element in the second embodiment. [Figure 20] FIG. 11 is a diagram showing the configuration of an image generating apparatus according to a third embodiment. [Figure 21] FIG. 11 is a diagram showing the peripheral configuration of an image generating element in a third embodiment. [Figure 22] FIG. 13 is a diagram showing the configuration of an image generating apparatus according to a fourth embodiment. [Figure 23] FIG. 13 is a diagram showing the configuration of a light distribution angle control element in Example 4. [Figure 24] FIG. 13 is another diagram showing the configuration of the light distribution angle control element in the fourth embodiment. [Diagram 25] FIG. 13 is a diagram showing the configuration of an image generating apparatus according to a fifth embodiment. [Figure 26] FIG. 13 is a diagram showing the peripheral configuration of an image generating element in the fifth embodiment. [Figure 27] FIG. 13 is another diagram showing the peripheral configuration of the image generating element in the fifth embodiment. [Figure 28] FIG. 13 is a diagram showing the configuration of an image generating apparatus according to a sixth embodiment. [Figure 29] FIG. 23 is a diagram showing the peripheral configuration of an image generating element in the sixth embodiment. [Diagram 30] FIG. 13 is a diagram showing the configuration around an image generating element according to a sixth embodiment. [Diagram 31] FIG. 13 is a diagram showing the configuration of an image generating apparatus according to a seventh embodiment. [Diagram 32] FIG. 23 is a diagram showing the peripheral configuration of an image generating element in Example 7. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings. EXAMPLES

[0011] 1 shows the configuration of an image display device according to Example 1. The image display device is composed of an image generating unit 100 and an optical system 50, and an image light beam 80 generated by the image generating unit 100 is guided to the observation side or the projection side via the optical system 50 so that the observer can view the image.

[0012] In the image generating unit 100, a parallel light beam 60 emitted from the light source unit 10 is deflected by an input deflection unit 21 provided on the surface of a light guide plate 20 serving as a light guiding member, and enters the light guide plate 20. The light beam that entered the light guide plate 20 propagates while being internally reflected (total reflected) within the light guide plate 20, and while propagating, is split and deflected into a plurality of beams by an output deflection unit 22 provided on the surface of the light guide plate 20, and each beam is guided to the image generating element 30 as an illumination light beam 70. The image generating element 30 serving as a light modulation element generates an image light beam 70a by modulating the illumination light beam 70 incident from the light guide plate 20 in accordance with an image signal input from the outside.

[0013] 2(a) and (b) show examples of the incident deflection unit 21. The incident deflection units 21a-i and 21a-ii are prism elements that refract or reflect the light beam 60 from the light source unit 10 and deflect it to an angle required for propagation inside the light guide plate 20.

[0014] 3(a) to (d) show another example of the incident deflection unit 21. The incident deflection units 21b-i, 21b-ii, 21b-iii, and 21b-iv are diffractive optical elements having a lattice structure with a fine pitch P equal to or less than the wavelength λ of the light beam 60, and deflect the light beam 60 from the light source unit 10 by diffraction and guide it into the light guide plate 20. By using a diffractive optical element as the incident deflection unit 21, a thin configuration with reduced physical unevenness can be achieved. Note that a diffractive optical element having a lattice structure with a pitch equal to or less than the wavelength has optical anisotropy with respect to polarized light. In this embodiment, the light beam 60 emitted from the light source unit 10 is S-polarized light, and the incident deflection units 21b-i to iv have the property of diffracting S-polarized light. Therefore, the S-polarized light beam 60 from the light source unit 10 is diffracted and guided into the light guide plate 20. Note that the shape, height, and refractive index of the lattice structure for controlling the efficiency and diffraction angle for each diffraction order may be set according to the requirements of the image display device. Furthermore, a holographic element having a deflecting effect on a light beam and anisotropy with respect to polarized light may be used in the incident deflection section.

[0015] 4(a) and (b) show an example in which an incident deflection unit is not provided on the light guide plate 20. By making the light beam 60 from the light source unit 10 incident on the incident surface of the light guide plate 20 from a direction inclined with respect to the normal line, the light beam 60 can be guided into the light guide plate 20 by the refraction effect of the incident surface of the light guide plate 20.

[0016] In FIG. 1, the light beam 60 propagated in the light guide plate 20 is outputted toward the image generating element 30 as illumination light beams 70 split by the output deflection unit 22 in the x direction in the figure. FIGS. 5(a) to 5(c) show the configuration of the output deflection unit 22. In order to improve the uniformity of brightness on the image generating element 30, which is the irradiated surface, the output deflection unit 22 has a plurality of (first to third) regions (22a-i, 2a-ii, 22a-iii), (22b-i, 22b-ii, 22b-iii), and (22c-i, 2c-ii, 22c-iii) having different output efficiencies. By appropriately setting the output efficiency of each of the plurality of regions as shown in Table 1, the amount of output light from the output deflection unit 22 can be made uniform.

[0017] [Table 1]

[0018] 5(a) is configured with any one of the diffractive optical elements shown in FIGS. 3(a) to 3(d), and the output efficiency and deflection action are controlled by the same element. This allows the illumination light beam 70 to be made perpendicular or nearly perpendicular and uniformly incident on the incident surface of the image generating element 30.

[0019] In addition, the manufacturing variation of the diffractive optical element is large, and the emission efficiency may deviate from the desired efficiency. For this reason, it is desirable that the emission deflection unit 22 is made of a dielectric multilayer film with less film formation variation. FIG. 6 shows, as an example, the characteristics of the dielectric multilayer film constituting the region 22b-ii of the emission deflection unit 22 shown in FIG. 5(b). Since the region 22b-ii does not have a deflection effect, the illumination light beam 70 emitted therefrom advances in a direction inclined with respect to the normal line of the emission surface of the light guide plate 20. In this case, it is desirable to arrange the light guide plate 20 so that the illumination light beam 70 emitted from the emission deflection unit 22 is incident on the image generating element 30 perpendicularly or nearly perpendicularly, as shown in FIG. 7.

[0020] 7 is difficult, a deflection element 23 may be disposed between the output deflection unit 22 and the image generating element 30, as shown in Fig. 5(c), for directing the illumination light beam 70, outputted obliquely from the output deflection unit 22, perpendicularly or nearly perpendicularly to the image generating element 30. The deflection element 23 may have any one of the functions of refraction, reflection, and diffraction with respect to the illumination light beam 70.

[0021] 8(a) and (b) show the configuration of the light source unit 10. The light source unit 10 has a light emitting unit 11, a collimator lens 12, and a mask 13. FIG. 8(c) shows a cross section of a light beam 14 emitted from the light emitting unit 11. The light emitting unit 11 is a semiconductor laser element. The light beam 14, which is linearly polarized light emitted in the z direction from the light emitting unit 11, has different light distribution angles u and v in the x and y directions as shown in FIG. 8(a) and (b). Therefore, as shown in FIG. 9, the cross section (FFP) of the light beam 14 on the xy plane is elliptical. The light beam 14 having this elliptical cross section has the same focal length in the x and y directions. The light beam is collimated by the collimator lens 12.

[0022] It is also possible to use an anamorphic collimator lens system to shape a light beam having an elliptical cross section so that a substantially circular collimated light beam is emitted from the light source unit 10 .

[0023] Furthermore, the mask 13 disposed behind the collimator lens 12 shapes the light beam 14. The opening shape of the mask 13 is similar to the shape of each of the regions of the output deflection section 22 divided as described above.

[0024] 8(a), (b) and 9, the light source unit 10 has a single light-emitting unit 11. In contrast, in order to display a color image, the light source unit 10 may have at least two (three in this embodiment) light-emitting units 11a to 11c as shown in Figs. 10(a) to 10(c). Then, light of three different wavelengths from these light-emitting units 11a to 11c may be incident on a single light guide plate 20.

[0025] In Fig. 10(a) and (b), the light emitting unit 11a is a red semiconductor laser element that emits a red laser beam having a wavelength of 620 to 650 nm, and the light emitting unit 11b is a blue semiconductor laser element that emits a blue laser beam having a wavelength of 440 to 470 nm. The light emitting unit 11c is a green semiconductor laser element that emits a green laser beam having a wavelength of 520 to 550 nm. The light beams emitted from the light emitting units 11a to 11c are collimated by the collimator lenses 12a to 12c provided for each light emitting unit, and then combined by the combining elements 15a to 15c, and are emitted from the light source unit 10 as white light. The combining elements 15a to 15c may be wavelength-selective dichroic filters, or may be polarization-selective polarizing beam splitters. Although the combining elements 15a to 15c are shown as plate-shaped elements, prism-shaped elements filled with glass or resin may also be used.

[0026] In addition, the green semiconductor laser element that emits green laser light, which is important in determining the brightness of the image display device, is arranged as the light-emitting unit 11c because it is desirable that the number of optical elements through which the green laser light passes is small and that the optical path after being collimated is short in order to reduce losses.

[0027] Furthermore, since the red semiconductor laser element has a large change in characteristics due to temperature, it is arranged as the light emitting section 11a in the light source section 10 where the volume of the heat sink (not shown) which is a heat dissipation mechanism can be most easily secured.

[0028] In the configuration shown in Fig. 10(b), the green laser light from the light-emitting unit 11c is transmitted through the combining element 15d and combined with the red and blue laser lights. This makes it possible to reduce the efficiency reduction caused by the positioning error between the light-emitting unit 11c and the combining element 15d more than in the configuration of Fig. 10(a).

[0029] 10(c), the laser beams emitted from the light-emitting units 11a to 11c may be combined via the optical waveguide 16 and then emitted from the lenses 12d and 12e. In this case, the combined laser beam emitted from the optical waveguide 16 is a coaxial white light, so a collimator lens for each light-emitting unit is not required. However, a lens 12d with negative power and a lens 12e with positive power are provided to correct aberrations for each color. The cross section of the optical waveguide 16 may be circular or rectangular with equal widths on the top, bottom, left and right sides, so that the cross section (FFP) of the light beam emitted from the optical waveguide 16 may be circular.

[0030] 1, when a diffractive optical element is used for at least one of the entrance deflection unit 21 and the exit deflection unit 22, the diffraction angle differs for each wavelength of the light beam incident thereon, and therefore multiple light guide plates 20 are required according to the wavelength of the light emitting unit to be used. On the other hand, when a dielectric multilayer film is used for at least one of the entrance deflection unit 21 and the exit deflection unit 22, light beams of multiple wavelengths can be propagated by a single light guide plate 20. This is because a semiconductor laser element with a narrow-band emission spectrum is used as the light emitting unit, and thereby it is possible to provide a dielectric multilayer film that satisfies the characteristics for each wavelength.

[0031] In the image generating unit 100 configured as above, as described above, the light beam 60 emitted from the light source unit 10 is collimated by the collimator lens system arranged in the light source unit 10. The semiconductor laser element in the light source unit 10 has a very small light emitting point (for example, 50 μm or less) and a narrow light distribution angle (for example, full width at half maximum (FWHM) is 25 degrees or less), so that a light beam with a very high degree of parallelism is emitted from the collimator lens system. In this embodiment, the light distribution characteristic of the light beam 60 is assumed to be within FWHM ±2 degrees. In order to reduce the variation in the emission efficiency of the above-mentioned emission deflection unit 22, it is desirable to set the light distribution characteristic of the light beam 60 within FWHM ±1 degree. Furthermore, in order to reduce the variation in the incident position of the light beam incident on each of the above-mentioned multiple regions of the emission deflection unit 22, it is desirable to set the light distribution characteristic of the light beam 60 within FWHM ±0.5 degrees.

[0032] The entrance surface and exit surface of the light guide plate 20 are arranged with a high degree of parallelism, and the light beam 60 propagates through the light guide plate 20 with its angle maintained. For this reason, the light distribution characteristic of the illumination light beam 70 propagating through the light guide plate 20 and exiting from the exit deflection section 22 is approximately equal to the light distribution characteristic of the light beam 60 exiting from the light source section 10 and entering the light guide plate 20. In other words, the divergence angle (FWHM) of the light distribution angle of the light beam 60 is θ1, and the divergence angle (FWHM) of the illumination light beam 70 is θ2. In this case, θ1 and θ2 are expressed as follows: 0.9≦θ2 / θ1≦1.1 (1) The following conditions are satisfied.

[0033] The illumination light beam 70 emitted from the output deflection unit 22 enters the image generating element 30 while maintaining the light distribution characteristic of formula (1). The image generating element 30 in this embodiment is a transmissive liquid crystal element, and by driving the liquid crystal in response to an image signal input from the outside, the illumination light beam 70 incident from the front entrance surface is converted into an image light beam 70a corresponding to the image signal and emitted from the rear exit surface. The light distribution characteristic of the light beam hardly changes before and after passing through the image generating element 30. In addition, since the transmissive liquid crystal element has an incident angle characteristic, it is desirable to make the illumination light beam 70 enter the entrance surface of the transmissive liquid crystal element perpendicular (from the normal direction of the entrance surface) or nearly perpendicular. The image light beam emitted from the image generating element 30 exits from the image display device via the optical system 50.

[0034] The acceptance angle (2NA: NA is the numerical aperture) of the light beam of the optical system 50 varies depending on the requirements of the image display device. However, as described above, the image light beam 70a emitted from the image generating element 30 maintains the light distribution characteristic shown in formula (1). In other words, it is necessary to set the light distribution characteristic of the image light beam 70a in accordance with the acceptance angle (2NA) of the light beam required by the optical system 50. For this reason, in this embodiment, the light distribution angle control element 40 is disposed between the image generating element 30 and the optical system 50.

[0035] Image light beam 70a emitted from image generating element 30 enters light distribution angle control element 40, where it is converted into image light beam 80 having light distribution characteristics (light distribution angle) different from image light beam 70a, and enters optical system 50. The FWHM as the divergence angle of illumination light beam 70 emitted from light guide plate 20 is θ2, the FWHM as the divergence angle of image light beam 80 traveling from light distribution angle control element 40 to optical system 50 is θ3, and the acceptance angle (2NA) of optical system 50 is θ4. In this case, θ2 to θ4 are expressed as follows: θ2<θ3 (2) 0.2≦θ3 / θ4≦1.5 (3) If the upper limit value of the formula (3) is too large, the capture efficiency of the optical system 50 decreases, so it is more preferable to set the upper limit value of the formula (3) as follows:

[0036] 0.2≦θ3 / θ4≦1.2 (3a) Moreover, if the lower limit of the formula (3a) is too small, the visibility of the displayed image is reduced. Therefore, it is more preferable to set the lower limit of the formula (3a) as follows.

[0037] 0.5≦θ3 / θ4≦1.2 (3b) By satisfying the above conditions, it is possible to generate with high efficiency an image light flux 80 that meets the requirements of the image display device.

[0038] The light distribution angle control element 40 may be a lens diffuser plate having a microlens array, or may be a holographic element having various patterns formed on its surface. The light distribution angle control element 40 may have different characteristics on the optical axis (central portion) and off the optical axis (peripheral portion). FIG. 11(a) shows a case where the divergence angle of the image light flux 80 differs between the central portion and the peripheral portion. When the divergence angle 80a of the image light flux 80 emitted from the central portion is θ3α, and the divergence angle 80b of the image light flux 80 emitted from the peripheral portion is θ3β, θ3α and θ3β are expressed as follows: θ3α>θ3β (4) This makes it possible to reduce the loss of light quantity in the peripheral portion, and to improve both the light quantity and the peripheral illumination ratio.

[0039] 11(b) shows a case where the angle of the chief ray 80c of the image light beam 80 emitted from the center of the light distribution angle control element 40 is different from that of the chief ray 80d of the image light beam 80 emitted from the peripheral portion, that is, the chief ray 80d of the peripheral portion is inclined with respect to the chief ray 80c of the center. As shown in this figure, by giving the light distribution angle control element 40 a light distribution angle control characteristic in which the chief ray 80d of the peripheral portion converges (approaches the chief ray 80c of the center), the downstream optical system 50 can be made compact. The chief ray in this embodiment is a light ray located at the center of the image light beam emitted from each region of the image generation element 30 and each region of the light distribution angle control element 40, and is also a light ray located at the center of the illumination light beam emitted from each region of the emission deflection section 22 of the light guide plate 20.

[0040] Next, the resolution of the displayed image will be described with reference to FIG. 12 and FIGS. 13(a) and 13(b). In general, in order to properly display an image, the position of the back focus BF of the optical system 50 is made to coincide with the exit surface (image display surface) of the image generating element 30 as shown in FIG. 12. However, if the light distribution angle control element 40 is disposed in the optical path of the optical system 50, the original image (optical image) shown in FIG. 13(a) becomes an image with a reduced resolution as shown in FIG. 13(b). In this embodiment, as described above, a light flux with high parallelism is guaranteed as the light flux until it enters the light distribution angle control element 40. In this case, the optical image on the image generating element 30 and the optical image on the light distribution angle control element 40 are almost equal. That is, the optical image on the light distribution angle control element 40 can be regarded as a secondary image of the optical image on the image generating element 30. Therefore, by making the position of the back focus BF of the optical system 50 and the position of the light distribution angle control element 40 almost coincide with each other, it is possible to avoid a reduction in the resolution of the displayed image.

[0041] 12, the back focus of the optical system 50 is BF, and the distance on the optical axis between the apex of the optical surface (lens surface) of the optical system 50 that is closest to the image generating element 30 and the exit surface of the light distribution angle control element 40 is BL. 0.9≦BL / BF≦1.1 (5) The following conditions are satisfied:

[0042] Fig. 14 shows the configuration of an image display system 300 to which the image display device of this embodiment is applied. The upper part of Fig. 14 shows an xz cross section, and the lower part shows an xy cross section. The image light beam emitted from the image generating unit 100 and then emitted from the optical system 50 is deflected by the entrance deflection unit 200i provided in the eyepiece light guide plate 200, enters the eyepiece light guide plate 200 as the eyepiece optical system, and enters the splitting deflection unit 200e while being totally reflected inside the eyepiece light guide plate 200. The image light beam that enters the splitting deflection unit 200e is deflected while being split into multiple beams in the x direction, and is guided to the exit deflection unit 200o.

[0043] The image light beam incident on the output deflection unit 200o is deflected while being split into multiple beams in the y direction, and directed toward the viewer's eye (pupil) SP. In Fig. 14, the direction (x direction) in which the image light beam is deflected by the input deflection unit 200i and the direction (y direction) in which the image light beam is deflected by the splitting deflection unit 200e are perpendicular to each other, but these do not need to be perpendicular as long as the image light beam incident on the eyepiece light guide plate 200 is output so as to be directed toward the pupil SP. Furthermore, since it is sufficient to guide the image light beam output from the image generation unit 100 to the pupil SP, a birdbath optical system using a half mirror or a refractive optical system using a polarized reflecting lens or a Fresnel lens may be used instead of the eyepiece light guide plate 200.

[0044] FIG. 15 shows a head mounted display (HMD) or smart glasses using the image display system of FIG. 14. The frame 400 holds the eyepiece light guide plate 200 in front of both eyes of the observer 1000, and holds image display devices corresponding to the eyepiece light guide plate 200. The image light beams emitted from the image generating unit 100 of each image display device are guided to the eyes of the observer 1000 through the eyepiece light guide plate 200. This allows the observer 1000 to view the display image 1100. By presenting display images having a parallax between the left and right eyes, the observer can view a stereoscopic image. In addition, a control unit 430 that controls the driving of the image generating element in the image generating unit 100 and the light amount of the light source unit 10 is connected to the frame 400. The control unit 430 may be arranged outside the frame 400 as shown in the figure and connected to the image generating unit 100 so as to be communicable by wire or wirelessly, or may be arranged inside the frame 400.

[0045] Further, a first information acquisition unit 410 including a camera that acquires pupil information indicating the position and movement (viewpoint or line of sight) of the observer 1000's pupil is attached to the frame 400. The control unit 430 corrects the position of the display image 1100 (the image generation position on the image generation element) based on the pupil information. Further, a second information acquisition unit 420 including a camera that acquires outside world (surroundings) information is attached to the frame 400. The control unit 430 adjusts the brightness of the display image 1100 according to the brightness of the outside world acquired from the outside world information.

[0046] 16 shows a head-up display (HUD) 450 as an in-vehicle image display system to which the image display device of this embodiment is applied. The HUD 450 has an image generating unit 100a, a projection optical system 50a, a first information acquisition unit 420a, a second information acquisition unit 410a, and a control unit 430a. The HUD 450 is mounted on an automobile 500 as a moving device, and projects and displays an image (virtual image) 1100a for supporting a user (driver or passenger) of the automobile 500 on a windshield as a projection surface via the projection optical system 50a. Note that the moving device may be a train, a ship, an airplane, or the like, in addition to an automobile.

[0047] The first information acquisition unit 420a includes a camera that acquires pupil information indicating the position and movement (viewpoint or line of sight) of the user's pupil SP. The control unit 430a corrects the position of the display image 1100a (the image generation position on the image generation element) based on the pupil information. The second information acquisition unit 410a includes a camera that acquires outside world (periphery) information. The control unit 430a adjusts the brightness of the display image 1100a according to the brightness of the outside world obtained from the outside world information, and displays the display image 1100a superimposed on the outside world image obtained from the outside world information. The second information acquisition unit 410a may acquire not only the outside world information in front, but also the outside world information behind, to the side, etc. In addition, the control unit 430a determines the possibility of collision of the automobile 500 with an obstacle (object) obtained from the outside world information, and when there is a possibility of collision, issues a warning or controls any of the drive unit (engine, motor, etc.), brakes, and steering of the automobile 500. The warning method includes generating a warning sound, displaying warning information on the display screen of the car navigation system, and emitting vibrations to the seat belt or steering wheel.

[0048] 17 shows the configuration of a real image projection system (projector) as an image display system to which the image display device of this embodiment is applied. The image light beam emitted from the image generating unit 100b is projected onto a projection surface 1100b such as a screen via a projection optical system 50b. The projection surface 1100b may be flat or curved. The control unit 430b drives the image generating element in response to an image signal input from the outside, adjusts the light amount of the light source unit 10, and adjusts the zoom and focus of the projection optical system 50a.

[0049] In the image display systems shown in FIGS. 14 to 17, the image generating section 100 of this embodiment may be replaced with an image generating section of another embodiment described later. EXAMPLES

[0050] 18 shows the configuration of an image display device of Example 2. The image display device has an image generating unit 110 and an optical system 50. The image generating unit 110 of this example differs from Example 1 in that the image generating element 31 is a reflective liquid crystal element, and other components that are the same as those of Example 1 are given the same reference numerals as those of Example 1 and will not be described here.

[0051] Illumination light beam 71 emitted from output deflection section 22c provided on light guide plate 20 enters image generating element 31, where it is converted into image light beam 71a and reflected, and then emitted toward output deflection section 22c. The light distribution characteristics of the light beam do not change before and after it enters and leaves image generating element 31. Also, since reflective liquid crystal elements have incident angle characteristics similar to transmissive liquid crystal elements, it is desirable to make illumination light beam 71 enter image generating element 31 perpendicular or nearly perpendicular to the normal to the incident surface.

[0052] The image light beam 71a emitted from the image generating element 31 passes through the emission deflection unit 22c and the light guide plate 20 and enters the light distribution angle control element 40. The emission deflection unit 22c in this embodiment is a diffractive optical element having a lattice structure finer than the wavelength of the incident light, and has optical anisotropy with respect to polarization. Specifically, the emission deflection unit 22c has a property of diffracting S-polarized light and transmitting P-polarized light. Therefore, the light beam 60 as S-polarized light emitted from the light source unit 10 is deflected by the entrance deflection unit 21, propagates through the light guide plate 20, is diffracted by the emission deflection unit 22c, and enters the image generating element 31 as the illumination light beam 71. The illumination light beam 71 is modulated into the image light beam 71a by the image generating element 31 and is reflected. At this time, the image light beam 71a is phase-modulated by the liquid crystal and is emitted as P-polarized light.

[0053] Image light beam 71a as P-polarized light passes through output deflection section 22c without being diffracted, and then passes through light guide plate 20 to be incident on light distribution angle control element 40. Light distribution angle control element 40 diffuses the incident image light beam 71a in accordance with the light acceptance angle (2NA) required by optical system 50.

[0054] Furthermore, in order to transmit the light beam through the output deflection section 22c with high efficiency, it is necessary to make the light beam with high polarization purity incident on the output deflection section 22c. For this reason, the light distribution angle control element 40 is disposed so that the image light beam 71a that has passed through the output deflection section 22c is incident on it. As shown in FIG. 19, the distance on the optical axis between the output surface (output deflection section 22c) of the illumination light beam 71 in the light guide plate 20 and the input / output surface of the image generating element 31 is L1, and the distance on the optical axis between the input / output surface of the image generating element 31 and the input surface of the light distribution angle control element 40 is L2. In this case, L1 and L2 are L1 / L2<1 (6) The following conditions are satisfied. EXAMPLES

[0055] 20 shows the configuration of an image display device of Example 3. The image display device has an image generation unit 120 and an optical system 50. The image generation unit 120 of this example differs from Example 2 in that the image generation element 32 is a reflective micromirror element (digital micromirror device: DMD) in which minute micromirrors are two-dimensionally arranged, and other components common to Example 2 are given the same reference numerals as in Example 2 and will not be described here.

[0056] In the reflective liquid crystal element serving as the image generating element 31 in the second embodiment, the incident angle of the illumination light beam and the exit angle of the image light beam are the same. On the other hand, the DMD serving as the image generating element 32 in the third embodiment forms an image by switching the inclination (two values: ON and OFF) of the micromirror for each pixel on which the illumination light beam 72 is obliquely incident, thereby controlling the deflection direction of the reflected image light beam 72a. Note that since the DMD only controls the deflection (traveling) direction of light, the deflection direction of the incident illumination light beam does not need to be unified as in the case of a liquid crystal display element.

[0057] 21, the illumination light beam 72 emitted from the emission deflection section 22d has its reflection direction deflected by the image generating element 32 and is emitted as an image light beam 72a. If the angle between the normal N of the emission surface of the light guide plate 20 and a principal ray 72p of the illumination light beam 72 emitted from the light guide plate 20 is ω1, and the angle between the normal N of the emission surface of the light guide plate 20 and a principal ray 72ap of the image light beam 72a emitted from the image generating element 32 is ω2, then ω1 and ω2 can be expressed as follows: 20°≦|ω1-ω2|≦40° (7) The following conditions are satisfied.

[0058] Note that the non-image light beam (not shown) reflected by the micromirror in the OFF state is deflected in a direction different from that of the image light beam 72a reflected by the micromirror in the ON state, and is emitted outside the optical path of the image light beam 72a. In this embodiment, the non-image light beam is processed (absorbed, etc.) in the image generating unit 120, and a mask 17 for blocking the non-image light beam is disposed between the light guide plate 20 and the light distribution angle control element 40 as shown in Fig. 20 so that the non-image light beam is not incident on the optical system 50 and is not visually recognized by the observer. As described above, the light beam before being incident on the light distribution angle control element 40 has a high degree of parallelism, which makes it easy to separate the image light beam and the non-image light beam, and therefore the mask 17 is disposed at the above position.

[0059] When a DMD is used as the image generating element 32, the illumination light beam 72 and the image light beam 72a are separated by the angle of incidence with respect to the output deflection unit 22d, so that the output deflection unit 22d is configured with a dielectric multilayer film. Specifically, by utilizing the incident angle characteristics of the dielectric multilayer film to control the transmittance and reflectance depending on the angle of incidence, light that is obliquely incident on the output deflection unit 22d is reflected, and light that is vertically or nearly vertically incident is transmitted.

[0060] By controlling the ratio between the transmittance and reflectance of the light that is obliquely incident on the output deflection section 22d, the uniformity of the illumination light beam 72 that is incident on the entire image generating element 32 can also be ensured. EXAMPLES

[0061] 22 shows the configuration of an image display device of Example 4. The image display device has the same image generating unit 130 and optical system 50 as in Example 3. This example differs from Example 3 in that light distribution angle control element 41 is a transmissive liquid crystal element equipped with a microlens array, and other components common to Example 3 are assigned the same reference numerals as in Example 3 and will not be described here.

[0062] 23 and 24 show the configuration of light distribution angle control element 41 in this embodiment. Light distribution angle control element 41 is a self-luminous device having pixel structure 44 in two-dimensional directions, horizontal and vertical, as shown in FIG.

[0063] 24 shows an enlarged model of a pixel in light distribution angle control element 41. Liquid crystal molecules 47 are filled in transparent electrodes 45 serving as opposing substrates, and a drive circuit 46 is disposed in the pixel structure on one of the substrates. The aperture ratio of a transmissive liquid crystal element is low because drive circuit 46 is disposed in the pixel structure.

[0064] Therefore, a microlens array 48 having a microlens corresponding to each pixel is disposed on the surface onto which the light beam is incident. The light beam incident on the light distribution angle control element 41 is converged by the microlens array 48 so as to avoid the drive circuit 46, thereby improving the aperture ratio. The light beam converged by the microlens array 48 passes through the focusing point and then exits from the light distribution angle control element 41 as a diverging light beam. That is, the light distribution angle control element 41 has the function of controlling the light distribution angle of the exiting light beam.

[0065] In addition, the light distribution angle control element 41 is also an image generating element having a pixel structure. Therefore, it is also possible for the light distribution angle control element 41 to display an image to be viewed by the observer. In this case, the image generating element (DMD) 32 arranged in the image generating unit 130, which is upstream of the light distribution angle control element 41, controls the illumination light flux 73 so as to supply the illumination light flux 72 corresponding to the image displayed by the light distribution angle control element 41 to the light distribution angle control element 41. This enables dimming for each region within the display surface of the light distribution angle control element 41, and allows the observer to view an image with a wide dynamic range of brightness (HDR image).

[0066] Generally, an optical system that makes HDR images visible requires a relay optical system that relays images between multiple panels. However, in the case where the parallelism of the light flux is high before it enters light distribution angle control element 41 as in this embodiment, it is possible to make HDR images visible with a simple configuration that does not include a relay optical system.

[0067] The light control region in light distribution angle control element 41 may be a region including only one pixel or a region including multiple pixels. Furthermore, light distribution angle control element 41 shown in this embodiment may be used in place of light distribution angle control element 40 in the other embodiments described above. EXAMPLES

[0068] 25 shows the configuration of an image display device of Example 5. The image display device has an image generating section 140 and an optical system 50. This example differs from Example 1 in that a light distribution angle control element 44 is disposed between a light guide plate 20 and an image generating element 34 serving as a transmissive liquid crystal element, and other components common to Example 1 are given the same reference numerals as in Example 1 and will not be described here.

[0069] In this embodiment and in embodiments 6 and 7 described below, the divergence angle (FWHM) of the light beam emitted from the light source unit 10 is θ1, and the divergence angle (FWHM) of the illumination light beam 70 is θ2. The divergence angle of the light beam emitted from the light distribution angle control element 44 (45) toward the optical system 50, among the illumination light beam and the image light beam, is θ3, and the acceptance angle (2NA) of the optical system 50 is θ4. In this case, 0.9≦θ2 / θ1≦1.1 (8) θ2<θ3 (9) 0.2≦θ3 / θ4≦1.5 (10) The following conditions are satisfied.

[0070] In the image generating unit 100 shown in the first embodiment, as described above, the light beam incident on the light distribution angle control element 40 has a high degree of parallelism, and the optical image on the image generating element 30 and the optical image on the light distribution angle control element 40 are substantially equal. For this reason, by matching the position of the back focus BF of the optical system 50 with the position of the light distribution angle control element 40, it is possible to suppress a decrease in perceived resolution. Conversely, when a light beam with low parallelism is incident on the light distribution angle control element 40 arranged in the light path of the optical system 50, an optical image with a low perceived resolution is displayed as shown in FIG. 13(b).

[0071] For this reason, in this embodiment, a light distribution angle control element 44 is disposed between the light guide plate 20 and the image generating element 34. As shown in Fig. 26, the distance between the incident surface of the image generating element 34 and the surface of the light distribution angle control element 44 facing the image generating element is L1, and the distance between the incident surface of the image generating element 34 and the exit surface (exit deflection section 22) of the light guide plate 20 is L2. In this case, the light distribution angle control element 44 has 0 <L1 / L2<1 (11) If the upper limit value of the formula (11) is too large, the transmission efficiency of the image generating element 30 decreases, so it is preferable to set the upper limit value of the formula (11) as follows.

[0072] 0 <L1 / L2≦0.5 (11a) 27, the back focus of optical system 50 is BF, and the distance on the optical axis between the apex of the optical surface (lens surface) in optical system 50 closest to image generating element 34 and the exit surface of light distribution angle control element 44 is BL. In this case, light distribution angle control element 44 is 0.9≦BL / BF≦1.1 (12) By arranging the lenses so as to satisfy the above condition, it is possible to avoid a decrease in the perceived resolution of the displayed image.

[0073] Like the light distribution angle control element 40 of the first embodiment, the light distribution angle control element 44 may be a lens diffuser plate having a microlens array, or may be a holographic element having various patterns formed on its surface. The light distribution angle control element 44 may have different characteristics on the optical axis (central portion) and off the optical axis (peripheral portion). Furthermore, the chief ray of the peripheral portion of the image light flux traveling from the light distribution angle control element 44 to the optical system 50 may be inclined with respect to the chief ray of the central portion. EXAMPLES

[0074] 28 shows the configuration of an image display device of Example 6. The image display device has an image generating unit 150 and an optical system 50. This example differs from Example 5 in that the image generating element 35 is a reflective liquid crystal element, and components common to Example 5 are given the same reference numerals as in Example 5 and will not be described here.

[0075] Illumination light beam 75 emitted from output deflection section 22m of light guide plate 20 enters image generating element 35, where it is converted into image light beam 85 and is reflected to be emitted toward output deflection section 22m, and then passes through output deflection section 22m and light guide plate 20 toward optical system 50. Note that the light distribution characteristics of the light beam hardly change before and after it enters and leaves image generating element 35. Therefore, image light beam 85 incident on light distribution angle control element 45, which is disposed between light guide plate 20 and image generating element 35, is diffused in accordance with the light capture angle (2NA) required by optical system 50.

[0076] In the configuration of this embodiment, since light distribution angle control element 45 is disposed in the optical path of optical system 50, there is a concern that the perceived resolution of the displayed image may decrease. However, the decrease in perceived resolution is correlated with the distance between image generating element 35 and light distribution angle control element 45. As shown in FIG. 29, the distance between the entrance / exit surface of image generating element 35 and the surface of light distribution angle control element 45 facing the image generating element is L1, and the distance between the entrance / exit surface of image generating element 35 and the exit surface of light guide plate 20 (exit deflection section 22m) is L2. In this case, light distribution angle control element 45 has 0 <L1 / L2<1 (13) If the upper limit value of the formula (13) is too large, the resolution of the displayed image will decrease, so it is preferable to set the upper limit value of the formula (10) as follows:

[0077] 0 <L1 / L2≦0.5 (13a) The closer the light distribution angle control element 45 is to the image generating element 35, the less the perceived resolution is reduced. For this reason, it is desirable that the surface of the light distribution angle control element 45 having the light distribution angle control function faces the entrance / exit surface of the image generating element 35 in close proximity (so that, for example, L1 / L2 is 0.2 or less).

[0078] 30, the back focus of optical system 50 is BF, and the distance on the optical axis between the apex of the optical surface (lens surface) of optical system 50 that is closest to the image generating element and the exit surface of light distribution angle control element 45 is BL. In this case, light distribution angle control element 45 is 0.9≦BL / BF≦1.1 (14) By arranging the lenses so as to satisfy the above condition, it is possible to suppress a decrease in perceived resolution.

[0079] In this embodiment, the output deflection unit 22m is a diffractive optical element having a lattice structure finer than the wavelength, and has optical anisotropy with respect to polarized light. Specifically, the output deflection unit 22m has a property of diffracting S-polarized light and transmitting P-polarized light. For this reason, the light beam 60 outputted as S-polarized light from the light source unit 10 is deflected by the input deflection unit 21, propagates through the light guide plate 20, is diffracted by the output deflection unit 22m, passes through the light distribution angle control element 45, and enters the image generating element 35 as an illumination light beam 75. The illumination light beam 75 is modulated into an image light beam 85 by the image generating element 35 and is reflected. At this time, the image light beam 85 has its phase modulated by the liquid crystal and is outputted as P-polarized light.

[0080] Image light beam 85 as P-polarized light is diffused by light distribution angle control element 45, and passes through light guide plate 20 without being diffracted by output deflection section 22m, and enters optical system 50. Image light beam 85 is diffused by light distribution angle control element 45 in accordance with the light acceptance angle (2NA) required by optical system 50, and in this embodiment, it is diffused by light distribution angle control element 45 on the outbound and return optical paths. When the degree of diffusion required for light distribution angle control element 45 is σ, the degree of diffusion on one surface (on the outbound path and on the return path) is σ×1 / √2.

[0081] Incidentally, the light distribution angle control element 45 may be one that diffuses the light flux only in one optical path, rather than in both optical paths. EXAMPLES

[0082] 31 shows the configuration of an image display device of Example 7. The image display device has an image generating unit 160 and an optical system 50. This example differs from Example 6 in that the image generating element 36 is a DMD, and components common to Example 6 are given the same reference numerals as in Example 6 and will not be described here.

[0083] As described in the second embodiment, the DMD as the image generating element 36 forms an image by switching the inclination (ON / OFF) of the micromirror for each pixel on which the illumination light beam 76 from the light guide plate 20 (output deflection section 22n) is obliquely incident, thereby controlling the deflection direction of the reflected image light beam 86. Since the DMD only controls the deflection (traveling) direction of light, the deflection direction of the incident illumination light beam does not need to be uniform, as in the case of a liquid crystal display element.

[0084] 32, the illumination light beam 76 emitted from the emission deflection section 22n is incident on the image generating element 36 via the light distribution angle control element 45, and the reflection direction is deflected by the image generating element 36 to be emitted as an image light beam 86. When the angle between the normal N of the emission surface of the light guide plate 20 and the principal ray 76p of the illumination light beam 76 emitted from the light guide plate 20 is ω1, and the angle between the normal N of the emission surface of the light guide plate 20 and the principal ray 86p of the image light beam 86 emitted from the image generating element 36 is ω2, ω1 and ω2 are expressed as follows: 20°≦|ω1-ω2|≦40° (15) The following conditions are satisfied.

[0085] Note that the non-image light beam (not shown) reflected by the micromirror in the OFF state is deflected in a direction different from that of the image light beam 86 reflected by the micromirror in the ON state, and is emitted outside the optical path of the image light beam 86. In this embodiment, the non-image light beam is processed (absorbed, etc.) in the image generating unit 160, and a mask 17a that blocks the non-image light beam is disposed between the light guide plate 20 and the optical system 50 as shown in Fig. 31 so that the non-image light beam is not incident on the optical system 50 and viewed by the observer.

[0086] When a DMD is used as the image generating element 36, the illumination light beam 76 and the image light beam 86 are separated by the angle of incidence with respect to the output deflection unit 22n, so that the output deflection unit 22n is configured with a dielectric multilayer film. Specifically, by utilizing the incident angle characteristics of the dielectric multilayer film to control the transmittance and reflectance depending on the angle of incidence, light that is obliquely incident on the output deflection unit 22n is reflected, and light that is vertically or nearly vertically incident is transmitted.

[0087] Incidentally, by controlling the ratio between the transmittance and the reflectance of the light that is obliquely incident on the output deflection portion 22n, the uniformity of the illumination light beam 76 that is incident on the entire image generating element 36 can also be ensured.

[0088] The above embodiment includes the following configurations.

[0089] (Configuration 1) A light source unit; an image generating element that modulates an incident light beam to generate an image light beam; a light guiding member that causes a light beam from the light source unit to propagate inside and emits a portion of the light beam from a plurality of regions toward the image generating element as an illumination light beam; an optical system for directing an image light beam from the image generating element to an observation side or a projection side; a light distribution angle control element that is disposed between the light guiding member and the optical system and controls a light distribution angle of the image light flux, When the divergence angle of the light flux emitted from the light source unit is θ1, the divergence angle of the light flux emitted from the light guiding member toward the image generation element is θ2, the divergence angle of the image light flux emitted from the light distribution angle control element is θ3, and 2NA as an acceptance angle of the optical system is θ4, 0.9≦θ2 / θ1≦1.1 θ2<θ3 0.2≦θ3 / θ4≦1.5 An image display device characterized in that the following conditions are satisfied. (Configuration 2) Let BF be the back focus of the optical system, and BL be the distance between the vertex of the optical surface of the optical system that is closest to the image generating element and the exit surface of the light distribution angle control element. 0.9≦BL / BF≦1.1 2. The image display device according to claim 1, wherein the following conditions are satisfied: (Configuration 3) the image generating element is a transmissive image generating element, 3. The image display device according to configuration 1 or 2, wherein the light distribution angle control element is disposed between the image generation element and the optical system. (Configuration 4) the image generating element is a reflective image generating element, 3. The image display device according to configuration 1 or 2, wherein the image light beam from the image generating element passes through the light guiding member and enters the optical system. (Configuration 5) When the distance between the exit surface of the image generating element and the exit surface of the light guiding member is L1, and the distance between the exit surface of the image generating element and the entrance surface of the light distribution angle control element is L2, L1 / L2<1 5. The image display device according to configuration 4, which satisfies the following conditions: (Configuration 6) Let ω1 be the angle between the normal to the exit surface of the light guiding member and the chief ray of the illumination light beam exiting from the light guiding member, and ω2 be the angle between the normal and the chief ray of the image light beam exiting from the image generating element. 20°≦|ω1-ω2|≦40° 6. The image display device according to configuration 5, which satisfies the following conditions: (Configuration 7) A light source unit; an image generating element that modulates an incident light beam to generate an image light beam; a light guiding member that causes a light beam from the light source unit to propagate inside and emits a portion of the light beam from a plurality of regions toward the image generating element as an illumination light beam; an optical system for directing an image light beam from the image generating element to an observation side or a projection side; a light distribution angle control element disposed between the light guiding member and the image generating element, the light distribution angle control element controlling at least one of the illumination light beam and the image light beam; Let θ1 be the divergence angle of the light flux emitted from the light source unit, θ2 be the divergence angle of the light flux emitted from the light guiding member toward the image generating element, θ3 be the divergence angle of the light flux of the illumination light flux and the image light flux emitted from the light distribution angle control element toward the optical system, and θ4 be 2NA as the acceptance angle of the optical system. 0.9≦θ2 / θ1≦1.1 θ2<θ3 0.2≦θ3 / θ4≦1.5 An image display device characterized in that the following conditions are satisfied. (Configuration 8) Let L1 be the distance between the incident surface of the image generating element and the surface of the light distribution angle control element facing the image generating element, and let L2 be the distance between the incident surface of the image generating element and the exit surface of the light guiding member from which the illumination light flux exits. 0 <L1 / L2<1 8. The image display device according to configuration 7, which satisfies the following conditions: (Configuration 9) Let BF be the back focus of the optical system, and BL be the distance between the vertex of the optical surface of the optical system that is closest to the image generating element and the exit surface of the light distribution angle control element. 0.9≦BL / BF≦1.1 9. The image display device according to configuration 7 or 8, which satisfies the following conditions: (Configuration 10) the image generating element is a transmissive image generating element, 8. The image display device according to configuration 7, wherein the light distribution angle control element is disposed between the light guiding member and the optical system. (Configuration 11) the image generating element is a reflective image generating element, 8. The image display device according to configuration 7, wherein the image light flux from the image generating element passes through the light guiding member via the light distribution angle control element and is incident on the optical system. (Configuration 12) 12. The image display device according to configuration 11, wherein a surface of the light distribution angle control element having a light distribution angle control function faces the image generation element. (Configuration 13) Let ω1 be the angle between the normal to the exit surface of the light guiding member and the chief ray of the illumination light beam exiting from the light guiding member, and ω2 be the angle between the normal and the chief ray of the image light beam exiting from the image generating element. 20°≦|ω1-ω2|≦40° 13. The image display device according to configuration 11 or 12, which satisfies the following conditions: (Configuration 14) An image display device according to any one of configurations 1 to 13, an eyepiece optical system for directing the image light beam from the image display device to an observer's eye, or a projection optical system for projecting the image light beam onto a projection surface;

[0090] The embodiments described above are merely representative examples, and various modifications and alterations are possible for each embodiment when implementing the present invention. [Explanation of symbols]

[0091] 10 Light source section 20 Light guide plate 30 Image generating element 40 Light distribution angle control element 50 Optical system

Claims

1. A light source unit; an image generating element that modulates an incident light beam to generate an image light beam; a light guiding member that causes a light beam from the light source unit to propagate inside and emits a portion of the light beam from a plurality of regions toward the image generating element as an illumination light beam; an optical system for directing an image light beam from the image generating element to an observation side or a projection side; a light distribution angle control element that is disposed between the light guiding member and the optical system and controls a light distribution angle of the image light flux, When the divergence angle of the light flux emitted from the light source unit is θ1, the divergence angle of the light flux emitted from the light guiding member toward the image generating element is θ2, the divergence angle of the image light flux emitted from the light distribution angle control element is θ3, and 2NA as an acceptance angle of the optical system is θ4, 0.9≦θ2 / θ1≦1.1 θ2<θ3 0.2≦θ3 / θ4≦1.5 An image display device characterized in that the following conditions are satisfied.

2. Let BF be the back focus of the optical system, and BL be the distance between the apex of the optical surface of the optical system that is closest to the image generating element and the exit surface of the light distribution angle control element. 0.9≦BL / BF≦1.1 2. The image display device according to claim 1, wherein the following conditions are satisfied:

3. the image generating element is a transmissive image generating element, 2. The image display device according to claim 1, wherein the light distribution angle control element is disposed between the image generating element and the optical system.

4. the image generating element is a reflective image generating element, 2. The image display device according to claim 1, wherein the image light beam from the image generating element passes through the light guiding member and enters the optical system.

5. When the distance between the exit surface of the image generating element and the exit surface of the light guiding member is L1, and the distance between the exit surface of the image generating element and the entrance surface of the light distribution angle control element is L2, L1 / L2<1 5. The image display device according to claim 4, wherein the following condition is satisfied:

6. Let ω1 be the angle between the normal to the exit surface of the light guiding member and the chief ray of the illumination light beam exiting from the light guiding member, and ω2 be the angle between the normal and the chief ray of the image light beam exiting from the image generating element. 20°≦|ω1−ω2|≦40° 6. The image display device according to claim 5, wherein the following conditions are satisfied:

7. A light source unit; an image generating element that modulates an incident light beam to generate an image light beam; a light guiding member that causes a light beam from the light source unit to propagate inside and emits a portion of the light beam from a plurality of regions toward the image generating element as an illumination light beam; an optical system for directing an image light beam from the image generating element to an observation side or a projection side; a light distribution angle control element disposed between the light guiding member and the image generating element, the light distribution angle control element controlling at least one of the illumination light beam and the image light beam; Let θ1 be the divergence angle of the light flux emitted from the light source unit, θ2 be the divergence angle of the light flux emitted from the light guiding member toward the image generating element, θ3 be the divergence angle of the light flux of the illumination light flux and the image light flux emitted from the light distribution angle control element toward the optical system, and θ4 be 2NA as the acceptance angle of the optical system. 0.9≦θ2 / θ1≦1.1 θ2<θ3 0.2≦θ3 / θ4≦1.5 An image display device characterized in that the following conditions are satisfied.

8. Let L1 be the distance between the incident surface of the image generating element and the surface of the light distribution angle control element facing the image generating element, and L2 be the distance between the incident surface of the image generating element and the exit surface of the light guiding member from which the illumination light flux exits. 0<L1 / L2<1 8. The image display device according to claim 7, wherein the following condition is satisfied:

9. Let BF be the back focus of the optical system, and BL be the distance between the apex of the optical surface of the optical system that is closest to the image generating element and the exit surface of the light distribution angle control element. 0.9≦BL / BF≦1.1 8. The image display device according to claim 7, wherein the following condition is satisfied:

10. the image generating element is a transmissive image generating element, 8. The image display device according to claim 7, wherein the light distribution angle control element is disposed between the light guide member and the optical system.

11. the image generating element is a reflective image generating element, 8. The image display device according to claim 7, wherein the image light flux from the image generating element passes through the light distribution angle control element, passes through the light guiding member, and enters the optical system.

12. 12. The image display device according to claim 11, wherein a surface of the light distribution angle control element having a light distribution angle control function faces the image generation element.

13. Let ω1 be the angle between the normal to the exit surface of the light guiding member and the chief ray of the illumination light beam exiting from the light guiding member, and ω2 be the angle between the normal and the chief ray of the image light beam exiting from the image generating element. 20°≦|ω1−ω2|≦40° 12. The image display device according to claim 11, wherein the following condition is satisfied:

14. The image display device according to any one of claims 1 to 13, an eyepiece optical system for directing the image light beam from the image display device to an observer's eye, or a projection optical system for projecting the image light beam onto a projection surface;

Images