Light guide element and display device

Abstract

To suppress the thickness of a light guide element and to emit a luminous flux with high distribution density.SOLUTION: The light guide device 10 includes a first optical device 10a that is an optical device that propagates incident light inside while reflecting the incident light on a first surface 10a - 1 and a second surface 21a - 2 and emits the light, the first optical device 21a further having a third surface 11a that reflects a first light 10a - 1, which is a part of the incident light, toward the inside and transmits a second light 14a - 2, which is another part of the incident light, and a second optical device 14a that reflects second light on at least one of reflecting surfaces LA - 1 and LA - 2. And a second optical device 14a which transmits the light through the third surface again and makes the light incident on the first optical device.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a light guide element suitable for a display device or the like. [Background technology]

[0002] An example of a light-guiding element that guides light that displays an image (image light) to the viewer's pupil is shown in Figure 24. After the image light enters and is deflected by a first deflection unit 1, it enters a substrate 3, is totally reflected by two surfaces of the substrate, propagates inside, and enters a second deflection unit 2. A portion of the image light that enters the second deflection unit 2 is deflected by the second deflection unit 2 and guided to the viewer's pupil SP. Meanwhile, another portion of the image light that enters the second deflection unit 2 is reflected, is totally reflected within the substrate 3, and then enters the second deflection unit 2 again. From the second deflection unit 2, multiple split light beams are guided to the pupil SP as the image light.

[0003] However, if the light beams emitted from the second deflection unit 2 are distributed discretely (i.e., the distribution density of the light beams is low), the quality of the observed image will be reduced. Patent Document 1 discloses a light guide element that can guide light beams with a high distribution density to the observer's pupil by stacking a main substrate corresponding to the above-mentioned substrate 3 with a half mirror layer and a sub-substrate for duplicating light. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6562088 Summary of the Invention [Problem to be solved by the invention]

[0005] In the configuration in which a main substrate, a half mirror layer, and a sub-substrate are stacked as disclosed in Patent Document 1, the thickness of the light guide element placed in front of the viewer's eyes increases. [Means for solving the problem]

[0006] A light guide element according to one aspect of the present invention is an optical element that reflects incident light at a first surface and a second surface while propagating the light inside and emitting the light, the light guide element further having a third surface that reflects a first light component of the incident light toward the inside and transmits a second light component of the incident light, and a second optical element that reflects the second light component at at least one reflective surface and transmits the second light component again through the third surface to be incident on the first optical element. Note that a display device using the light guide element also constitutes another aspect of the present invention. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a light guide element that emits a light flux with a high distribution density while suppressing an increase in thickness. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing a display device according to an embodiment. [Figure 2] FIG. 2 is a diagram showing the optical configuration of a display device according to an embodiment. [Figure 3] FIG. 2 is a diagram showing the configuration of an image generating unit in the first embodiment. [Figure 4] FIG. 2 is a diagram showing a display element according to the first embodiment. [Figure 5] FIG. 10 is a diagram showing a light flux distribution in an eye box in an embodiment. [Figure 6] 1 is a diagram showing the relationship between the luminous flux distribution in the eyebox and the observer's pupil. [Figure 7] FIG. 2 is a diagram showing the configuration of an incident deflection unit in the first embodiment. [Figure 8] FIG. 2 is a graph showing the characteristics of the angle selective film in Example 1. [Figure 9] FIG. 10 is a diagram showing another configuration of the incident deflection unit in the first embodiment. [Figure 10] FIG. 10 is a diagram showing yet another configuration of the incident deflection unit in the first embodiment. [Figure 11] FIG. 10 is a diagram showing the configuration of an incident deflection unit in the second embodiment. [Figure 12] FIG. 10 is a diagram showing the configuration of an optical element according to a second embodiment. [Figure 13]FIG. 10 is a diagram showing the configuration of an incident deflection unit in the third embodiment. [Figure 14] FIG. 10 is a graph showing the characteristics of the angle selective film in Example 3. [Figure 15] FIG. 10 is a diagram showing the configuration of an incident deflection unit in the fourth embodiment. [Figure 16] FIG. 10 is a diagram showing the configuration of an optical element according to a fourth embodiment. [Figure 17] FIG. 13 is a diagram showing the configuration of an incident deflection unit in the fifth embodiment. [Figure 18] FIG. 20 is a diagram showing the configuration of an image generating unit in the sixth embodiment. [Figure 19] FIG. 13 is a diagram showing the configuration of an output deflection unit in the sixth embodiment. [Figure 20] FIG. 20 is a diagram showing another configuration of the output deflection unit in the sixth embodiment. [Figure 21] FIG. 20 is a diagram showing yet another configuration of the output deflection unit in the sixth embodiment. [Figure 22] FIG. 20 is a diagram showing another configuration of the image generating unit in the sixth embodiment. [Figure 23] FIG. 20 is a diagram showing yet another configuration of the image generating unit in the sixth embodiment. [Figure 24] FIG. 10 is a diagram showing a conventional light guide element. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0010] FIG. 1 shows an example of a display device (smart glasses or a head-mounted display) as an embodiment. The display device has a frame 900 worn on the head of an observer (user) 1000, and an image generation unit (not shown) and a light guide plate 10 as a light guide element held by the frame 900. The display device guides image light emitted from the image generation unit to the eyes (pupils) of the observer 1000 via the light guide plate 10, thereby displaying a display image (image) 1100 and allowing the observer 1000 to view it. Details of the image generation unit will be described later, but the image generation unit may be provided for each of the eyes of the observer 1000, or may be provided for one eye. When an image generation unit is provided for both eyes, it is also possible to view a stereoscopic image by providing parallax between left and right display images viewed by both eyes.

[0011] The first information acquisition unit 910 is, for example, an imaging device such as a digital 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 relating to the position of at least a part of the observer 1000, for example, information relating to the position of the observer's 1000's pupils. The viewpoint information of the observer 1000 is information relating to the viewpoint or line of sight of the observer 1000, for example, information relating to the movement of the observer's pupils. The second information acquisition unit 920 is, for example, an imaging device such as a digital camera, and acquires external world information (peripheral information).

[0012] The control unit 200 is configured with a processor such as a CPU (Central Processing Unit), and is capable of acquiring the amount of deviation between the image light emitted from the image generation unit and the pupil position of the viewer 1000 based on the position information of the viewer 1000 acquired by the first information acquisition means 910. The control unit 200 can correct the positional deviation of the image light with respect to the pupil position of the viewer 1000 based on the position information acquired by the first information acquisition unit 910.

[0013] The control unit 200 also acquires the brightness of the outside world based on the outside world information acquired by the second information acquisition unit 920, and sets the luminance of the image light (display image 1100) appropriately for the acquired brightness. Note that the brightness of the display image 1100 can also be changed in response to an operation by the observer 1000. [Example]

[0014] 2(a) shows the optical configuration of the display device of Example 1. In the figure, the in-plane directions of the light guide plate 10 are the xy directions, and the thickness direction of the light guide plate 10 is the z direction.

[0015] A luminous flux 20 of image light emitted from the image generating unit 100 is incident on and deflected by the incident deflection unit 11 provided on the first surface side of the light guide plate 10, and enters the inside of the light guide plate 10 as a luminous flux 21. The luminous flux 21 propagates inside the light guide plate 10 while being totally reflected by the first surface on the pupil SP side of the light guide plate 10 and a second surface parallel to the first surface on the outside world side, and then enters the splitting deflection unit 12.

[0016] The light beam 21 incident on the splitting deflection unit 12 is split and deflected in the x direction, and is guided to the exit deflection unit 13 as a plurality of split light beams 22. Each split light beam 22 incident on the exit deflection unit 13 is split and deflected in the y direction, and is output as a plurality of split light beams 23 toward the viewer's pupil SP.

[0017] In this embodiment, the direction of deflection by the incident deflection unit 11 and the direction of deflection by the splitting deflection unit 12 are orthogonal to each other, but the deflection direction may be any direction as long as the light beam incident on the light guide plate 10 is emitted toward the pupil SP. Also, as shown in FIG. 2(b), the light guide plate 10 may be configured to have the incident deflection unit 11 and the exit deflection unit 13 without having the splitting deflection unit 12.

[0018] 3(a) and 3(b) show configuration examples 100a and 100b of the image generating section 100. Fig. 4 shows the configuration of a display element 110 as a light modulation element in the image generating section 100.

[0019] The display element 110 is a self-luminous device in which a plurality of pixels 110a are arranged in two dimensions, horizontally and vertically (x-direction and y-direction), and may be an organic EL (organic electro-luminescence) device or a micro LED (micro light emitting diode) device.

[0020] A divergent light beam emitted from the display element 110 is converted into a parallel light beam by the incident optical system 111, which is an afocal optical system, and then enters the incident deflection unit 11. In this embodiment, a lens optical system shown in FIG. 3(a) is used as the incident optical system 111. However, as shown in FIG. 3(b), a prism optical system that deflects the light beam by transmission or reflection using a free-form surface or the like may also be used as the incident optical system 112. The prism optical system in FIG. 3(b) is composed of two prisms 112a and 112b, but it may also be composed of a single prism or three or more prisms.

[0021] The control unit 200 controls the display element 110, such as by causing the display element 110 to display an image and by controlling the lighting and light intensity of each pixel 11a. The control unit 200 may be provided inside the image generating unit 100 as shown in Figures 3(a) and 3(b), or may be provided outside the image generating unit 100 (separate from the frame 900) and be able to communicate with the frame 900 via wire or wirelessly.

[0022] Furthermore, a non-self-luminous device such as an LCD (Liquid Crystal Display), a DMD (Digital Micromirror Device), or a MEMS (Micro-Electro-Mechanical Systems) device may be used as the display element 110. In this case, a light source is provided to irradiate the display element with illumination light, and the control unit 200 controls the lighting and light intensity of the light source.

[0023] As described above, by dividing the image light into multiple light beams, the eyebox 30, which is the area in which the viewer can view the displayed image (where the pupil SP can be located), is expanded as shown in FIG. 5. However, as shown in FIG. 5, the divided light beams have a finite size (light beam diameter) φ, and multiple light beams 23 are distributed discretely. The spacing D between the light beams 23 is determined by the propagation distance when the light beams 23 propagate while undergoing total reflection inside the light guide plate 10 (the spacing between the reflection positions of the light beams 21 on the first surface or the second surface shown in FIGS. 3(a) and 3(b)). When the thickness of the light guide plate 10 is d and the critical angle between the first and second surfaces of the light guide plate 10 is θc, it is expressed by the following equation (1).

[0024] D=2×d×tanθc (1) The critical angle θc is determined by the refractive index nd of the light guide plate 10, and equation (1) can be rewritten as equation (2) below.

[0025] D = 2 × d × tan(asin(1 / nd)) (2) Here, we will explain the effect on viewing the displayed image of the discrete distribution of light beams in the eye box 30. As shown in Fig. 6(a), it is preferable that the eye box 30 be enlarged so that the displayed image can be viewed even when the observer's pupil SP moves in the x and y directions. However, if the distribution of light beams 23 in the enlarged eye box 30 is discrete, as shown in Fig. 6(b), some light beams 23 will not reach the observer's retina Re, as shown in Fig. 6(c), resulting in areas where the displayed image cannot be viewed.

[0026] Therefore, in the light guide plate 10 of this embodiment, as shown in FIG. 7, the incident deflection portion 11a, which is provided as a third surface on the substrate 10a serving as a first optical element having light transmissivity, is a partial transmission / reflection surface that transmits a portion of the incident light beam and reflects the other portion. Specifically, the incident deflection portion 11a is provided with an angle-selective dielectric film whose transmittance and reflectance vary depending on the angle of incidence of the light beam. Furthermore, the light guide plate 10 of this embodiment includes a prism 14a serving as a second optical element having light transmissivity and optically coupled to the substrate 10a at the incident deflection portion 11a. Note that in this embodiment, the substrate 10a and the prism 14a are bonded to each other at the incident deflection portion 11a. This prevents unnecessary reflection and refraction near the incident deflection portion 11a. However, the substrate 10a and the prism 14a may be disposed apart (or close to each other) without being bonded.

[0027] The incident deflection unit 11a has an angle with respect to the first surface 10a-1 and the second surface 10a-2 of the substrate 10a. Specifically, the angle formed by the incident deflection unit 11a and the normal to the first surface 10a-1 of the substrate 10a onto which the light beam 20a as incident light is incident is defined as θ. R0 In this case, θ R0 It is preferable that the condition of the following formula (3) is satisfied.

[0028] θ R0 ≦45° (3) In this embodiment, R0 =30°. Therefore, the light beam 20a that is perpendicularly incident on the first surface 10a-1 of the substrate 10a is incident on the incident deflection unit 11a at an angle of 60° with respect to the normal line thereof.

[0029] FIG. 8 shows the characteristics of the angle-selective dielectric film provided on the incident deflection unit 11a. Here, the characteristics are shown when unpolarized R (red), G (green), and B (blue) light are incident on the angle-selective dielectric film. The angle-selective dielectric film has the property of reflecting a portion (approximately 50%) of the incident light beam within an incident angle range of 60°±10° and transmitting the other portion (approximately 50%). Therefore, a portion of the light beam 20a incident on the incident deflection unit 11a is reflected toward the inside of the substrate 10a as light beam (first light) 21a-1, and the remaining light beam (second light) 21a-2 is transmitted through the incident deflection unit 11a and enters the prism 14a.

[0030] The light beam 21a-2 incident on the prism 14a is totally reflected by the first reflecting surface 14a-1 and the second reflecting surface 14a-2 of the prism 14a and then re-enters the incident deflection unit (angle-selective dielectric film) 11a. At this time, the light beam 21a-2 is perpendicularly incident on the incident deflection unit 11a at an incident angle of 0°. As a result, the light beam 21a-2 is transmitted through the incident deflection unit 11a without being reflected much, as shown in FIG. 8. The light beam 21a-2 transmitted through the incident deflection unit 11a is a light beam with an inverted phase relative to the light beam 21a-1 and propagates through the substrate 10a while being totally reflected. As a result, as described above, multiple light beams can be generated from the light beam 21a-2 so as to fill in the gaps between the multiple light beams that are discretely distributed due to the splitting of the light beam 21a-1. This improves the visibility of the displayed image.

[0031] In order to improve light utilization efficiency, it is desirable that the light beams 20 (21a-1, 21a-2) incident on the light guide plate 10 from the image generating unit 100 are linearly polarized light with narrow spectral widths for each of the RGB colors and a unified polarization direction. Specifically, it is desirable that the full width at half maximum (FWHM) of the spectral width be 20 nm or less.

[0032] Furthermore, it is desirable that the spectrum of the image light emitted from the display element 110 is narrow band and has a uniform polarization direction, but a hand-pass filter or polarizer may be disposed between the display element 110 and the light guide plate 10. Furthermore, in order to make the light beam that is incident again on the incident deflection unit 11a via the prism 14a perpendicular to the incident deflection unit 11a, it is preferable to satisfy the condition of the following formula (4). In formula (4), the angle formed between the incident deflection unit 11a and the first reflecting surface 14a-1 of the prism 14a (the reflecting surface from which the second light is first reflected) is defined as θ R1 Let's say.

[0033] 80°≦θ R1 ≦100° (4) θ R1 If θ is smaller than 80°, the end of the second reflecting surface 14a-2 becomes an inclined surface approaching the incident deflection portion 11a, as shown in Figure 9, and it becomes difficult to ensure an appropriate area for the incident deflection portion 11a, which is not preferable. R1 If the angle is greater than 100°, the end of the second reflecting surface 14a-2 becomes an inclined surface that moves away from the incident deflection unit 11a as shown in Figure 10, which undesirably increases the volume of the prism 14a. Since the light beam that does not enter the incident deflection unit 11a is lost without being guided to the eyebox 30, it is desirable to set the area of ​​the incident deflection unit 11a so that it can capture all of the light beam incident from the image generation unit. To achieve this, it is desirable to satisfy the condition of the following equation (5).

[0034] 85°≦θ R1 ≦100° (5) In order to further reduce the volume of the prism 14a, it is desirable to satisfy the condition of the following formula (6).

[0035] 85°≦θ R1 ≦95° (6) The light beam 21a-2 that passes through the incident deflection unit 11a must maintain the same angle before and after passing through it. For this reason, it is desirable that the prism 14a be made of the same material as the substrate 10a, which has the same refractive index nd and Abbe number νd. [Example]

[0036] 11 shows a light guide plate 10 of Example 2. The light guide plate 10 is composed of a substrate 10a and a prism 14b as a second optical element optically coupled to the substrate 10a at its incident deflection section 11b. This example differs from Example 1 in that a light beam 20b from the image generation section 100 is incident on a side surface 14b-1 of the prism 14b. Other than that, this example is the same as Example 1, and the same reference numerals as Example 1 are used to designate components common to Example 1, and a description thereof will be omitted.

[0037] The light beam 20b enters the side surface 14b-1 of the prism 14b, is refracted, and enters the incident deflection unit 11b. The incident deflection unit 11b is provided with an angle-selective dielectric film having the same characteristics as in the first embodiment. In this embodiment, the light beam 20b is also incident on the incident deflection unit 11b at an incident angle of 60°, and a portion of the light beam 20b is reflected by the incident deflection unit 11b and propagates through the substrate 10a as a light beam (first light) 21b-1. Meanwhile, the light beam (second light) 21b-2 that has passed through the incident deflection unit 11b is totally reflected by the first reflecting surface 14b-2 and the second reflecting surface 14b-2 of the prism 14b and enters the incident deflection unit 11b again. At this time, the light beam 21b-2 is perpendicularly incident on the incident deflection unit 11b and passes through the incident deflection unit 11b with almost no reflection. The light beam 21b-2 transmitted through the incident deflection unit 11b propagates through the substrate 10a while being totally reflected as a light beam having an inverted phase with respect to the light beam 21b-1. As a result, it is possible to generate a plurality of light beams split from the light beam 21b-2 so as to fill in the gaps between the plurality of light beams that are discretely distributed by splitting the light beam 21b-1.

[0038] 12, an anti-reflection coating is provided on the region of the side surface 14b-1 of the prism 14b where the light beam 20b is incident, and a reflective coating that reflects the light beam 21b-2 with high reflectance is provided on the region 14b-3 other than the anti-reflection coating. The reflective coating may be a metal film or a dielectric film, but it is preferable to use a dielectric film that has low absorption when the spectral width of the incident light beam is narrow.

[0039] In this embodiment, the diameter of the light beam 20b can be increased because the light beam 20b is incident on the side surface 14b-1 of the prism 14b and refracted. As a result, the light beam 21b-2 can effectively fill in the gaps between the multiple light beams that are discretely distributed after the light beam 21b-1 is separated. [Example]

[0040] 13 shows a light guide plate 10 of Example 3. The light guide plate 10 is composed of a substrate 10a and a prism 14c as a second optical element optically coupled to the substrate 10a at its incident deflection section 11c. This example differs from Example 1 in that the prism 14c is provided with three reflecting surfaces and two light beam separation layers (separation sections: hereinafter simply referred to as separation layers). Other than that, this example is the same as Example 1, and components common to Example 1 will be assigned the same reference numerals as Example 1 and will not be described here.

[0041] A light beam 20c perpendicularly incident on the first surface 10a-1 of the substrate 10a is incident on the incident deflection unit 11c at an angle of 60°. FIG. 14 shows the characteristics of the angle-selective dielectric film provided on the incident deflection unit 11c. Again, this shows the characteristics when unpolarized R, G, and B light are incident on the angle-selective dielectric film. The angle-selective dielectric film has the property of reflecting a portion (approximately 25%) of the light beam incident at an angle of incidence in the range of 60°±10° and transmitting the other portion (approximately 75%). Therefore, a portion of the light beam 20c incident on the incident deflection unit 11c is reflected toward the inside of the substrate 10a as a first light beam (first light) 21c-1, and the remaining light beam (second light) is transmitted through the incident deflection unit 11c and enters the prism 14c.

[0042] A portion of the light beam incident on the prism 14c is transmitted through the first separation layer 15c-1, and the other portion is reflected by the first separation layer 15c-1. The second light beam 21c-2 that transmitted through the first separation layer 15c-1 is totally reflected by the first reflecting surface 14c-1 and the second reflecting surface 14c-2 of the prism 14c, is perpendicularly incident on the incident deflection unit 11a, is transmitted through it, and propagates through the substrate 10a while being totally reflected. Furthermore, a portion of the light beam reflected by the first separation layer 15c-1 is reflected by the second separation layer 15c-2, and the other portion is transmitted through the second separation layer 15c-2. The third light beam 21c-3 that reflected by the second separation layer 15c-2 is perpendicularly incident on the incident deflection unit 11a, is transmitted through it, and propagates through the substrate 10a while being totally reflected. The fourth light beam 21c-4 that passes through the second separation layer 15c-2 is totally reflected by the third reflecting surface 14c-3 of the prism 14c, passes through the transmission area 16c within the prism 14c, and is perpendicularly incident on the incident deflection section 11b, and propagates inside the substrate 10a while being totally reflected.

[0043] Table 1 shows the relationship between the transmittance or reflectance of the incident deflection portion (angle-selective dielectric film) 11c, the first separation layer 15c-1, the second separation layer 15c-2 and the transmission region 16c and the light amount of the first to fourth light beams 21c-1 to 21c-4.

[0044] [Table 1]

[0045] Of the light beam 20c with a light intensity of 1.00, the first light beam 21c-1 is reflected by the incident deflection portion 11c with a reflectance of 0.25 and enters the substrate 10a with an intensity of 0.25. Of the light beam 20c, the second light beam 21c-2 passes through the incident deflection portion 11c with a transmittance of 0.75, passes through the first separation layer 14c-1 with a transmittance of 0.33, is reflected by the first and second reflecting surfaces 14c-2, 14c-2 and enters the substrate 10a with an intensity of 0.25. Furthermore, the third light beam 21c-3 passes through the incident deflection portion 11c with a transmittance of 0.75, is reflected by the first separation layer 14c-1 with a reflectance of 0.67, is reflected by the second separation layer 14c-2 with a reflectance of 0.50 and enters the substrate 10a with an intensity of 0.25. Furthermore, the quantity of light of the fourth light beam 21c-4 that passes through the incident deflection portion 11c with a transmittance of 0.75, is reflected by the first separation layer 14c-1 with a reflectance of 0.67, passes through the second separation layer 14c-2 with a transmittance of 0.50, is reflected by the third reflecting surface 14c-3, and enters the substrate 10a is 0.25.

[0046] In this embodiment, the characteristics of the incident deflection section (angle-selective dielectric film) 11c and the first and second separation layers 14c-1 and 14c-2 are appropriately set, so that the spaces between the multiple discretely distributed light beams obtained by separating the light beam 21c-1 can be effectively filled by the light beams 21c-2 to -4, and the light intensity of each light beam can be made uniform. [Example]

[0047] 15 shows a light guide plate 10 of Example 4. The light guide plate 10 is composed of a substrate 10a and a prism 14d as a second optical element optically coupled to the substrate 10a at its incident deflection section 11d. This Example differs from Example 1 in that the incident deflection section 11d has multiple regions with different characteristics and that the prism 14d has three reflective surfaces. Other than that, this Example is the same as Example 1, and the same reference numerals as Example 1 are used to designate components common to Example 1, and a description thereof will be omitted.

[0048] In this embodiment, the angle between the incident deflection unit 11d and the normal to the first surface 10a-1 of the substrate 10a on which the light beam 20d is incident is defined as θ R0 When θR0 satisfies the condition of the following equation (7).

[0049] θ R0 ≧45° (7) 16, the incident deflection unit 11d has a first region 11d-1 as a partial transmission / reflection region that transmits a portion (approximately 50%) of the incident light and reflects the remaining portion (approximately 50%), and a second region 11d-2 as a transmission region that transmits almost all of the incident light. The first region 11d-1 is provided with an angle-selective dielectric film similar to that in Example 1.

[0050] In this embodiment, θ R0 = 60°, and light beam 20d perpendicularly incident on first surface 10a-1 of substrate 10a is incident on first region 11d-1 of incident deflection unit 11d at an angle of 30° with respect to the normal. The light beam (first light) reflected by first region 11d-1 propagates inside light guide plate 10a as light beam 21d-1. Meanwhile, the light beam (second light) transmitted through first region 11d-1 of incident deflection unit 11c is incident on prism 14d.

[0051] The light beam incident on prism 14d is totally reflected by first reflecting surface 14d-1, second reflecting surface 14d-2, and third reflecting surface 14d-3 of prism 14d, and then enters second region 11d-2 of incident deflection unit 11d. When the condition of formula (7) is satisfied, the incident angle of the light beam with respect to second region 11d-2 is also 30°, the same as the incident angle of light beam 20d with respect to first region 11d-1, but the incident light beam is transmitted through second region 11d-2.

[0052] The light beam 21d-2 that has passed through the second region 11d-2 propagates through the substrate 10a as a light beam having an inverted phase relative to the light beam 21d-1, thereby allowing the light beam 21d-2 to more effectively fill in the gaps between the multiple light beams that have been discretely distributed after the light beam 21d-1 has been separated.

[0053] Furthermore, in order to make the light beam 21d-2 incident on the incident deflection unit 11d again via the prism 14d at the same incident angle as the incident angle of the light beam 20d on the incident deflection unit 11c, it is sufficient to satisfy the conditions of the following expressions (8) and (9). Here, the angle formed between the incident deflection unit 11d and the first reflecting surface 14d-1 of the prism 14d is defined as θ R1 , the angle formed between the second reflecting surface 14d-2 and the third reflecting surface 14d-3 is θ R2 Let's say.

[0054] 80°≦θ R1 ≦100° (8) 180°-|θ R2 +θ R1 |≦2° (9) [Example]

[0055] 17 shows a light guide plate 10 of Example 5. The light guide plate 10 is composed of a substrate 10a and a prism 14e as a second optical element optically coupled to the substrate 10a at its input deflection section 11e. This Example differs from Example 1 in that the input deflection section 11d is provided with a polarization separation element having polarization selectivity that transmits linearly polarized light in a specific polarization direction (P-polarized light) and reflects linearly polarized light in a polarization direction orthogonal to the P-polarized light (S-polarized light), and in that the prism 14e has three reflecting surfaces. The polarization separation element may be a MacNeille type made of a dielectric multilayer film or a grid type made of a fine shape.

[0056] Other than that, it is the same as the first embodiment, and the same components as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment, and the explanation thereof will be omitted.

[0057] Light beam 20e is incident on substrate 10a as unpolarized light, and S-polarized light (first light) of the light beam 20e is reflected by incident deflection unit 11d and propagates through substrate 10a as light beam 21e-1. On the other hand, P-polarized light (second light) of light beam 20e is transmitted through incident deflection unit 11d and enters prism 14e.

[0058] The light beam (P-polarized light) incident on prism 14d is totally reflected by first reflecting surface 14e-1, second reflecting surface 14e-2, and third reflecting surface 14e-3 of prism 14d, and then re-enters and passes through incident deflection unit 11e, propagating through substrate 10a as light beam 21e-2. At this time, light beam 21e-2 propagates through substrate 10a as a light beam whose phase is inverted relative to light beam 21e-1. As a result, light beam 21e-2 can more effectively fill in the gaps between multiple light beams that have been separated and discretely distributed from light beam 21e-1.

[0059] As described above, according to Examples 1 to 5, it is possible to provide a light guide element that can emit a light flux with a high distribution density while suppressing an increase in thickness.

[0060] In Examples 1 to 5, the prisms (14a to 14e) constituting the light guide plate 10 are described as having two or three reflecting surfaces, but four or more reflecting surfaces may be provided, or only one curved (concave) reflecting surface may be provided. In other words, the prism serving as the second optical element only needs to have at least one reflecting surface. [Example]

[0061] A configuration similar to that of the light guide plate 10 shown in Examples 1 to 5 can also be used to guide illumination light for illuminating a display element disposed in an image generating section.

[0062] FIG. 18 shows the configuration of the image generating unit 100c when the display element 110 is configured as a transmissive LCD. A parallel light beam emitted from the light source unit 130 and incident on the light guide plate 10′ is partially reflected by the input polarization unit 11A and propagates through the substrate 10A while undergoing total internal reflection. The light beam transmitted through the input polarization unit 11A is reflected by a prism 14A optically coupled to the substrate 10A, then passes through the input polarization unit 11A and propagates through the substrate 10A while undergoing total internal reflection. The two light beams thus reaching the output polarization unit 13A are split and deflected in the x direction and emitted toward the display element 110. The image light modulated by the display element 110 enters the light guide plate 10 described in Examples 1 to 5 via the input optical system 111 (or 112).

[0063] The output deflection unit 13A may be configured with a diffractive optical element having a grating structure finer than the wavelength of the light beam, as shown in Figures 19(a) to 19(d). In this case, the incident light beam is deflected by the diffraction action of the diffractive optical element. Alternatively, the output deflection unit 13A may be configured with a plurality of inclined partially reflective / transmissive surfaces 13b-i to -iv, as shown in Figure 20. The partially reflective / transmissive surfaces are provided with a dielectric multilayer film or the like. In this case, the incident light beam is deflected by reflection at the partially reflective / transmissive surfaces.

[0064] In order to improve the uniformity of the amount of illumination light on the illuminated surface, that is, the display element 110, it is desirable that the output deflection unit 13 include a plurality of regions with different output efficiencies. Specifically, the amount of illumination light can be made uniform by gradually increasing the output efficiency (the diffraction rate of the diffractive optical element or the reflectance of the partially reflective / transmissive surface) from the incident side of the output deflection unit 13.

[0065] Furthermore, as shown in FIG. 21, a dielectric multilayer film with different properties may be provided in multiple regions 13c-i to -iv on the display element-side surface of the substrate 10A. If there is a concern about performance degradation due to insufficient film thickness or overlap at the boundaries between the multiple regions 13c-i to -iv, each multilayer film may be formed as a gradient film with a different film thickness depending on the position. In the configuration shown in FIG. 21, a light beam is emitted from the regions 13c-i to -iv at an angle with respect to the normal to the display element-side surface of the substrate 10A. For this reason, it is desirable to dispose a deflector 40 between the light guide plate 10′ and the display element 110 so that the light beam is incident on the display element 110 approximately perpendicularly. The deflector 40 may be any element capable of achieving deflection through refraction, reflection, or diffraction.

[0066] 22 shows the configuration of the image generating unit 100d when the display element 110 is configured as a reflective LCD. In this configuration, a light beam emitted perpendicularly from the output deflection unit 13A of the light guide plate 10' toward the display element 110 is modulated and reflected by the display element 110, passes through the light guide plate 10' as image light, and enters the input optical system 111. Because the polarization directions of the incident light and output light are converted in the reflective LCD, it is desirable that the output deflection unit 13A be configured using a diffractive optical element or polarization separation element having polarization selectivity.

[0067] 23 shows the configuration of the image generating unit 100e when the display element 110 is configured as a DMD. In this configuration, a light beam emitted obliquely from the output deflection unit 13A of the light guide plate 10' toward the display element 110 is modulated and reflected by the display element 110, passes through the light guide plate 10' as image light, and enters the incident optical system 111. Because the angles of the incident light and output light are converted in the DMD, it is desirable to configure the output deflection unit 13A using a dielectric multilayer film with angle selectivity.

[0068] The above embodiment includes the following configurations.

[0069] (Configuration 1) a first optical element that reflects incident light at a first surface and a second surface, propagates the light inside, and emits the light, and further has a third surface that reflects a first light, which is a part of the incident light, toward the inside and transmits a second light, which is the other part of the incident light; a second optical element that reflects the second light from at least one reflecting surface and transmits the second light through the third surface again to cause the second light to be incident on the first optical element. (Configuration 2) 2. The light guide element according to configuration 1, wherein the first optical element and the second optical element are bonded to each other at the third surface. (Configuration 3) The angle formed between the third surface and the at least one reflecting surface from which the second light is first reflected is defined as θ R1 When 80°≦θ R1 ≦100° 3. The light guide element according to configuration 1 or 2, which satisfies the following conditions: (Configuration 4) 4. The light guide element according to any one of configurations 1 to 3, wherein the third surface has different reflectance and transmittance depending on the angle of incidence of the incident light with respect to the third surface. (Configuration 5) 2. The light-guiding element according to claim 1, wherein the third surface reflects the first light, which is linearly polarized in a specific polarization direction among the incident light, and transmits the second light, which is linearly polarized in a polarization direction perpendicular to the specific polarization direction. (Configuration 6) 6. The light-guiding element of any one of configurations 1 to 5, wherein the third surface has a first region that reflects a portion of the second light and transmits another portion of the second light, and a second region that transmits the second light. (Configuration 7) The angle between the third surface and the normal to one of the first and second surfaces onto which the incident light is incident is defined as θ R0 When θ R0 ≦45° 7. The light guide element according to any one of configurations 1 to 6, which satisfies the following conditions: (Configuration 8) The angle between the third surface and the normal to one of the first and second surfaces onto which the incident light is incident is defined as θ R0 When θ R0 ≧45° 7. The light guide element according to any one of configurations 1 to 6, which satisfies the following conditions: (Configuration 9) 9. The light guide element of any one of configurations 1 to 8, wherein the incident light is incident on the first optical element from the first or second surface. (Configuration 10) 9. The light guide element of any one of configurations 1 to 8, wherein the incident light passes through the third surface from the second optical element and enters the first optical element. (Configuration 11) 11. The light guide element of any one of configurations 1 to 10, wherein the second optical element further includes a separation portion that reflects a portion of the second light and transmits another portion of the second light. (Configuration 12) The second optical element is a first separation section that reflects a part of the second light and transmits another part of the second light; a second separation section that reflects a portion of the light reflected by the first separation section and transmits another portion of the light; The light-guiding element of configuration 11, characterized in that light that passes through the first separation section and is reflected by the at least one reflecting surface, light that is reflected by the first separation section and is reflected by the second separation section, and light that is reflected by the first separation section, passes through the second separation section and is reflected by the at least one reflecting surface are transmitted through the third surface and made incident on the first optical element. (Configuration 13) The light guide element according to any one of configurations 1 to 12; a light modulation element that modulates light from the light source, A display device characterized in that light from said light modulation element is guided to an observer's eye via said light guide element. (Configuration 14) The light guide element according to any one of configurations 1 to 12; a light modulation element that modulates light, guides light from a light source to the light modulation element via the light guide element; A display device that displays an image formed by light from the light modulation element. (Configuration 15) A plurality of light beams having different wavelength bands are emitted from the light source, 15. The display device according to configuration 13 or 14, wherein the full width at half maximum as the spectral width of each of the plurality of lights is 20 nm or less.

[0070] (Other Examples) The present invention can also be realized by supplying a program that realizes one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and having one or more processors in the computer of the system or device read and execute the program. It can also be realized by a circuit (e.g., ASIC) that realizes one or more functions.

[0071] The embodiments described above are merely representative examples, and various modifications and alterations are possible to each embodiment when implementing the present invention. [Explanation of symbols]

[0072] 10 Light guide plate 10a Substrate (first optical element) 11 Incident deflection section 13 Output deflection section 14 Prism (second optical element) 110 Display element

Claims

1. a first optical element that reflects incident light at a first surface and a second surface, propagates the light inside, and emits the light; and the first optical element further has a third surface that reflects a first light, which is a part of the incident light, toward the inside and transmits a second light, which is the other part of the incident light; a second optical element that reflects the second light from at least one reflecting surface and transmits the second light through the third surface again to cause the second light to be incident on the first optical element.

2. The light guide element according to claim 1 , wherein the first optical element and the second optical element are bonded to each other at the third surface.

3. The angle formed between the third surface and the at least one reflecting surface from which the second light is first reflected is defined as θ Ｒ１ When 80°≦θ Ｒ１ ≦100° 2. The light guide element according to claim 1, wherein the following conditions are satisfied:

4. The light guide element according to claim 1 , wherein the third surface has different reflectance and transmittance depending on the angle of incidence of the incident light with respect to the third surface.

5. 2. The light-guiding element according to claim 1, wherein the third surface reflects the first light, which is linearly polarized in a specific polarization direction, of the incident light, and transmits the second light, which is linearly polarized in a polarization direction perpendicular to the specific polarization direction.

6. 2. The light guide element according to claim 1, wherein the third surface has a first region that reflects a part of the second light and transmits another part of the second light, and a second region that transmits the second light.

7. The angle formed by the third surface and the normal to the surface of the first or second surface onto which the incident light is incident is defined as θ Ｒ０ When i Ｒ０ ≦45° 2. The light guide element according to claim 1, wherein the following conditions are satisfied:

8. The angle formed by the third surface and the normal to the surface of the first or second surface onto which the incident light is incident is defined as θ Ｒ０ When i Ｒ０ ≧45° 2. The light guide element according to claim 1, wherein the following conditions are satisfied:

9. The light guide element according to claim 1 , wherein the incident light is incident on the first optical element from the first or second surface.

10. The light guide element according to claim 1 , wherein the incident light passes through the third surface from the second optical element and enters the first optical element.

11. The light guide element according to claim 1 , wherein the second optical element further comprises a separating portion that reflects a part of the second light and transmits another part of the second light.

12. The second optical element is a first separation unit that reflects a part of the second light and transmits another part of the second light; a second separation section that reflects a portion of the light reflected by the first separation section and transmits another portion of the light; 12. The light guide element according to claim 11, wherein light that passes through the first separation section and is reflected by the at least one reflecting surface, light that is reflected by the first separation section and is reflected by the second separation section, and light that is reflected by the first separation section, passes through the second separation section and is reflected by the at least one reflecting surface are transmitted through the third surface and made incident on the first optical element.

13. The light guide element according to claim 1 ; a light modulation element that modulates light from the light source, A display device characterized in that light from said light modulation element is guided to an observer's eye via said light guide element.

14. The light guide element according to claim 1 ; a light modulation element that modulates light, guides light from a light source to the light modulation element via the light guide element; A display device that displays an image formed by light from the light modulation element.

15. A plurality of light beams having different wavelength bands are emitted from the light source, 15. The display device according to claim 13, wherein the full width at half maximum of each of the plurality of light beams as a spectral width is 20 nm or less.

Images