Light guide element, image display device, and method for manufacturing light guide element

Abstract

To provide a high efficiency light guide element.SOLUTION: A light guide element has a first light guide portion that propagates a light beam incident thereon while reflecting the light beam therein, and a second light guide portion that emits the light beam from the first light guide portion part by part while reflecting the light beam therein. A first optical film 10-i is provided on the first light guide portion, and a second optical film 11-i different in characteristics from the first optical film is provided on the second light guide portion to be adjacent to the first optical film. A first light guide member 1-i constituting the first light guide portion and a second light guide member 1-ii constituting the second light guide portion are closely adhered or joined to each other.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a light guide element suitable for image display devices such as head-mounted displays, smart glasses, and head-up displays. [Background technology]

[0002] In order to obtain a uniform illumination distribution on the illuminated surface, which is a display element or an observer's pupil plane, Patent Documents 1 and 2 disclose light guide elements that guide light from a light source to the illuminated surface. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent Publication No. 2023 / 0037929 [Patent Document 2] U.S. Patent Publication No. 2022 / 0066214 Summary of the Invention [Problem to be solved by the invention]

[0004] Such light guide elements are required to have high efficiency. [Means for solving the problem]

[0005] A light guide element according to one aspect of the present invention includes a first light guide portion that internally reflects and propagates an incident light beam, and a second light guide portion that internally reflects the light beam from the first light guide portion and emits the light beam at intervals. A first optical film is provided in the first light guide portion, and a second optical film having properties different from those of the first optical film is provided in the second light guide portion so as to be adjacent to the first optical film. The first light guide member constituting the first light guide portion and the second light guide member constituting the second light guide portion are in close contact or bonded to each other. Note that an image display device using the above light guide element also constitutes another aspect of the present invention.

[0006] Another aspect of the present invention relates to a manufacturing method applicable to the manufacture of a light guide element having a first light guide portion that internally reflects and propagates an incident light beam, and a second light guide portion that internally reflects the light beam from the first light guide portion and emits the light beam at intervals of a portion. The manufacturing method includes the steps of: preparing a first light guide member provided with a first optical film as a component constituting the first light guide portion; preparing a second light guide member provided with a second optical film having properties different from those of the first optical film as a component constituting the second light guide portion; and closely contacting or bonding the first light guide member and the second light guide member so that the first optical film and the second optical film are adjacent to each other. [Effects of the Invention]

[0007] According to the present invention, a highly efficient light guide element can be provided. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 2 is a diagram showing the configuration of an image generating unit of the image display device according to the first embodiment. [Figure 2] FIG. 2 is a diagram showing a light guide element of the image display device according to the first embodiment. [Figure 3] FIG. 2 is a diagram showing an incident deflection unit of the image display device according to the first embodiment. [Figure 4] FIG. 10 is a diagram showing another example of the incident deflection unit. [Figure 5] FIG. 10 is a diagram showing yet another example of the incident deflection unit. [Figure 6] FIG. 6 is a diagram showing an example of the configuration of the incident deflection unit in FIG. 5. [Figure 7] FIG. 4 is a diagram showing the spectral characteristics of an optical film provided on a first element in Example 1. [Figure 8] FIG. 2 is a diagram showing a light source unit of the display device of the first embodiment. [Figure 9] FIG. [Figure 10] FIG. 10 is a diagram showing another example of the light source unit. [Figure 11] 4 is a diagram showing the spectral characteristics of an optical film provided on a second element in Example 1. FIG. [Figure 12] FIG. 1 is a diagram showing a conventional film formation method. [Figure 13] 3A to 3C are diagrams showing a method for producing a light-guiding element in Example 1. [Figure 14] 4A to 4C are other views showing the method for producing the light-guiding element in the first embodiment. [Figure 15] 3A to 3C are diagrams illustrating a method for manufacturing the light guide member according to the first embodiment. [Figure 16] 5A to 5C are other views showing the method for manufacturing the light guide member according to the first embodiment. [Figure 17] FIG. 10 is a diagram showing the configuration of an image generating unit according to a second embodiment. [Figure 18] FIG. 11 is a diagram showing the configuration of an image generating unit according to a third embodiment. [Figure 19] FIG. 10 is a diagram showing the configuration of an image generating unit according to a fourth embodiment. [Figure 20] FIG. 10 is a diagram showing the spectral characteristics of an optical film provided on a second element of Example 4. [Figure 21] FIG. 10 is a diagram showing another configuration of the image generating unit according to the fourth embodiment. [Figure 22] FIG. 10 is a diagram showing yet another configuration of the image generating unit according to the fourth embodiment. [Figure 23] FIG. 10 is a diagram showing a light beam directed from a light guide element to a display element in the fourth embodiment. [Figure 24] FIG. 10 is a diagram showing the configuration of a display device according to a fifth embodiment. [Figure 25] FIG. 13 is a diagram showing the configuration of a display device according to a sixth embodiment. [Figure 26] FIG. 13 is a diagram showing the configuration of an HMD using an image generating unit according to a fifth embodiment. [Figure 27] FIG. 2 is a diagram showing the configuration of a HUD using an image generating unit according to the first embodiment. [Figure 28] FIG. 2 is a diagram showing the configuration of a projector using the image generation unit of the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

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

[0010] 1 shows the configuration of an image generating unit 100 used in the image display device of Example 1. The image generating unit 100 is configured by a light guide element configured so that a first light guide member 1-i and a second light guide member 1-ii are continuous, a light source unit (light generating unit) 50, and a display element 60. As shown in the figure, the longitudinal direction of each light guide member is defined as the X direction, the width direction is defined as the Y direction, and the thickness direction is defined as the Z direction.

[0011] The light guide element is an element that propagates an incident light beam while reflecting it internally, and emits a portion of the light beam at a time from an emission region (a surface R2 of the second light guide member 1-ii, which will be described later). In the light guide element, the first light guide member 1-i constitutes a first light guide portion, and the second light guide member 1-ii constitutes a second light guide portion.

[0012] The first light guide member 1-i and the second light guide member 1-ii are configured with transparent substrates (light-transmitting substrates) 30-i and 30-ii as base members, respectively. Each transparent substrate has an R1 surface that reflects the incident light beam (actually, reflection by a reflective film, described later) and an R2 surface that faces the R1 surface in the Z direction and reflects or transmits the light beam reflected by the R1 surface (actually, reflection or transmission by a transflective film, described later). Optical films 10-i and 10-ii and optical films 11-i and 11-ii that reflect at least a partial spectrum of the light beam from the light source unit 50 are formed on the R1 and R2 surfaces of the transparent substrates 30-i and 30-ii, respectively, to produce the first light guide member 1-i and the second light guide member 1-ii. The optical film 10-i corresponds to the first optical film, and the optical film 11-i corresponds to the second optical film.

[0013] As shown in Fig. 2, the optical film 10-i has an opening AP for allowing the light beam Ray1 to enter the first light guide member 1-i (transparent substrate 30-i). The shape of the opening AP may be rectangular as shown in Fig. 2, or may be any shape such as a square, a circle, or a polygon. Alternatively, as shown in Fig. 3, the optical film 10-i may not have an opening AP, and the light beam may be incident from an end face in the Z direction of the first light guide member 1-i.

[0014] The light source unit 50 is disposed so that the light beam is incident on the first light guide member 1-i from an oblique direction according to the propagation angle of the light beam in each light guide member. However, as shown in Figures 4(a) and 4(b), the light beam from the light source unit 50 may be incident on the incident deflection elements 20a-i and 20a-ii from a direction perpendicular to the first light guide member 1-i, and the light beam may be deflected in an oblique direction according to the propagation angle of the light beam in each light guide member before being incident on the first light guide member 1-i. The incident deflection elements 20a-i and 20a-ii are prism elements that refract or reflect the light beam from the light source unit 50.

[0015] 5 may be used to make the light beam from the light source unit 50 obliquely incident on the first light guiding member 1-i. The incident deflection element 20b is any one of the diffractive optical elements 20b-i to 20b-iv having a grating structure formed at a pitch finer than the wavelength of the light beam from the light source unit 50, as shown in FIGS. 6(a) to 6(d). By using such a diffractive optical element as the incident deflection element 20b, physical irregularities can be reduced, and the configuration including the incident deflection element 20b can be made thinner.

[0016] A diffractive optical element having a lattice structure finer than the wavelength of the light beam has optical anisotropy with respect to polarization. When the light beam emitted from the light source unit 50 is S-polarized light, the incident deflection element 20b has the property of diffracting S-polarized light, so that the S-polarized light from the light source unit 50 is diffracted and enters the first light guiding member 1-i. The efficiency and diffraction angle for each diffraction order can be controlled by changing the shape, height, refractive index, etc. of the lattice structure according to the specifications required of the image generation unit 100. Alternatively, a holographic element having a light beam deflection action and anisotropy with respect to polarization may be used as the incident deflection element 20b.

[0017] The propagation of light beams incident on the first light guide member 1-i and the second light guide member 1-ii will be described using FIG. 1. The light beam incident on the first light guide member 1-i propagates in the X direction while being alternately reflected by the R1 and R2 surfaces, and then enters the second light guide member 1-ii from its end face in the X direction. The light beam also propagates in the X direction in the second light guide member 1-ii while being alternately reflected by the R1 and R2 surfaces. At this time, part of the light beam is reflected on the R1 surface of the second light guide member 1-ii, and the rest is transmitted and emitted to the outside of the second light guide member 1-ii. As a result, part of the light beams incident on the second light guide member 1-ii is emitted from the R1 surface toward and illuminates the display element 60.

[0018] In order to efficiently propagate the light beam from the light source unit 50 within the first light guide member 1-i, optical films 10-i and 10-ii are formed on the R1 and R2 surfaces of the first light guide member 1-i as reflective films having a high reflectance characteristic of nearly 100% for visible light, as shown in FIG. 7. Since the light beam propagates within the first light guide member 1-i while being reflected multiple times, it is desirable that the optical films 10-i and 10-ii be formed of a dielectric multilayer film with low absorption rather than a metal film. By forming the optical films 10-i and 10-ii, it is possible to reflect and propagate the light beam within the first light guide member 1-i even if the R1 and R2 surfaces do not satisfy the total reflection condition. Specifically, when the angle of incidence of the light beam on the R1 and R2 surfaces is θ and the refractive index of the transparent substrate 30-i at the d-line (wavelength 587.6 nm) is nd, θ<(asin(1 / nd)) Even if the incident angle θ is smaller than (asin(1 / nd)), the light beam can be reflected and propagated within the first light guide member 1-i. By making the incident angle θ smaller than (asin(1 / nd)), the propagation length of the light beam in one round trip between the R1 surface and the R2 surface can be shortened, and the light beam in each round trip can be prevented from being separated in the X direction.

[0019] 8(a) and 8(b) respectively show the XZ cross section and the YZ cross section of the light source section 50. Fig. 9 shows the XY cross section of the light beam emitted from the light emitting section 51 of the light source section 50.

[0020] As shown in Figures 8(a) and 8(b), the light beam emitted from the light-emitting unit 51 is linearly polarized and has different light distribution angles in the X and Y directions. Therefore, as shown in Figure 9, the shape of the light beam (FFP) in the XY cross section is elliptical. The light beam with an elliptical cross section is converted into a parallel light beam by a collimator lens 52 having the same focal length. As a result, as shown in Figure 8(c), a collimated light beam 54 with an elliptical cross section whose width u in the X direction is shorter than its width v in the Y direction is emitted from the light source unit 50.

[0021] It is also possible to use an anamorphic lens as the collimator lens to form a collimated light beam having a circular cross section and emit it from the light source unit 50 .

[0022] Furthermore, a mask 53 may be disposed after the collimator lens 52, and the cross-sectional shape of the collimated light beam may be shaped by passing through an opening in the mask 53. In this case, the shape of the opening in the mask 53 may be similar to the shape of the opening AP provided in the optical film 10-i, as shown in FIG.

[0023] The light source unit 50 may have a single light-emitting unit 51 as shown in Figures 8(a), (b) and 9, or may have three (or more) light-emitting units 51a to 51c that emit light in different colors as shown in Figures 10(a) to (c).

[0024] 10(a), light-emitting unit 51a is a red semiconductor laser that emits red light with a wavelength of 620 to 650 nm, light-emitting unit 51b is a blue semiconductor laser that emits blue light with a wavelength of 440 to 470 nm, and light-emitting unit 51c is a green semiconductor laser that emits green light with a wavelength of 520 to 550 nm. The three colored lights emitted from light-emitting units 51a to 51c are converted into parallel beams by collimator lenses 52a to 52c, respectively, and then combined by combining elements 55a to 52c to be emitted from light source unit 50 as white light.

[0025] As combining elements 55a-52c, dichroic mirrors having wavelength selectivity or polarizing beam splitters having polarization selectivity may be used. Furthermore, combining elements 55a-52c may be plate-shaped elements as shown in the figure, or may be prism-shaped elements filled with glass or resin.

[0026] In order to ensure the brightness of the image displayed by the image display device, it is important to reduce the loss of green light, so it is desirable to use a green semiconductor laser for light-emitting unit 51c, which has a small number of elements through which the light passes and a short optical path after being converted into a parallel beam.

[0027] Furthermore, the characteristics of the red semiconductor laser change significantly depending on the temperature, so the light emitting section 51c, which is the section of the light source section 50 where it is easiest to ensure the volume of a heat sink (not shown) as a heat dissipation structure, may be a red semiconductor laser.

[0028] 10(b) shows a configuration in which a green semiconductor laser is used as light-emitting unit 51c, and green light is transmitted through combining element 55d and combined with blue light and red light, thereby reducing the efficiency reduction caused by the positioning error of combining elements 55a to 52c in FIG.

[0029] As shown in FIG. 10(c), the colored light beams emitted from the light-emitting units 51a to 51c may be combined via an optical waveguide 56. In this case, the colored light beams become coaxial white light beams when they are emitted from the optical waveguide 56, so a collimator lens for each light-emitting unit is not required. However, a negative-power lens 52d and a positive-power lens 52e are required to correct aberrations for each colored light beam. The cross-sectional shape of the optical waveguide 56 can be made circular or square, so that the cross-sectional shape of the light beam emitted from the optical waveguide 56 can also be made circular.

[0030] By using a laser with a narrow-band emission spectrum and high directionality for each light-emitting element, the optical films 10-i and 10-ii of the first light-guiding member 1-i can be formed of a dielectric multilayer film that satisfies the reflection characteristics at each wavelength.

[0031] On the other hand, it is necessary to emit a part of the incident light flux from the R1 surface of the second light guide member 1-ii toward the display element 60. For this reason, an optical film 11-i, which is a transmissive-reflective film with controlled transmittance and reflectance for visible light (transmittance is approximately 80% and reflectance is approximately 20%), is formed on the R1 surface of the second light guide member 1-ii as shown in Fig. 11. In this embodiment, since the object is to propagate the light flux from the light source unit 50 to the display element 60 with high efficiency, an optical film 11-ii that is the same as the optical films 10-i and 10-ii of the first light guide member 1 is formed on the R2 surface of the second light guide member 1-ii.

[0032] When optical films 10-i and 11-i with different characteristics are formed in adjacent regions on the same surface of a single transparent substrate 30-iii, as shown in FIG. 12(b), a mask is first placed in the film-forming region where the optical film 10-i is to be formed, as shown in FIG. 12(a), and a first film formation is performed. Then, as shown in FIG. 12(b), the mask is moved to the film-forming region where the optical film 11-i is to be formed, and a second film formation is performed. If each film-forming region is small, vignetting by the mask can cause the film thickness at the boundary between the optical films 10-i and 11-i to deviate from the specified thickness, resulting in failure to obtain the required characteristics. Furthermore, if the mask is misaligned from the film-forming region, gaps can occur between the optical films 10-i and 11-i, or they can overlap, as shown in FIG. 12(c). These gaps can cause light beams that should be reflected to transmit or light beams that should be transmitted to be reflected, resulting in reduced efficiency and uniformity and stray light.

[0033] In this example, an optical element is manufactured using a manufacturing method including the steps shown in FIG. 13. First, two separate transparent substrates 30-i and 30-ii are prepared, each having a separate deposition area for the optical films 10-i and 11-i. Next, the optical films 10-i and 11-i are deposited on the R1 surfaces of the transparent substrates 30-i and 30-ii from one end to the other in the X direction to manufacture the first and second light guide members 1-i and 1-ii. Then, the X-direction end faces C1 of the first and second light guide members 1-i and 1-ii (transparent substrates 30-i and 30-ii) are brought into close contact with each other. This results in a light guide element in which the optical films 10-i and 11-i with different properties are formed adjacent to each other (preferably adjacent) on the R1 surface without any gaps or overlaps.

[0034] In the X direction, which is the propagation direction of the light beam within the light-guiding element, when the length of each transparent substrate is W1 and the length of an optical film provided on each transparent substrate (for example, optical film 10-i on transparent substrate 30-i) is W2, 0.95≦W1 / W2≦1.05 By satisfying this condition, the optical films 10-i and 11-i are formed so as to be at least adjacent to each other (preferably adjacent to each other) in the light guide element.

[0035] Furthermore, if the refractive indexes of the transparent substrates 30-i and 30-ii are equal to each other and the surface precision of the end face C1 is ensured to be equal to or less than the wavelength of the light to be propagated, the light beam can be transmitted without refraction or total reflection at the end face C1. When the angle between the end face C1 and the surface R1 on which the optical film is provided is θC, 10°≦θC≦170° It is preferable to satisfy the following conditions.

[0036] 14 is used to hold the first and second light guide members 1-i and 1-ii after film formation and bring the end faces C1 into close contact with each other. Specifically, a holding member 70 for holding the first light guide member 1-i and a holding member 71 for holding the second light guide member 1-ii are prepared, and an adjustment member 72 connected to these holding members 70 and 71 is screwed in to reduce the gap between the first and second light guide members 1-i and 1-ii, bringing the end faces C1 into close contact with each other.

[0037] Instead of the adjustment member 72, the end faces C1 of the first and second light guide members 1-i and 1-ii may be brought into close contact with each other by using the elastic force of an elastic member such as rubber, sponge, or spring. In this case, it is desirable that the end faces C1 of the first and second light guide members 1-i and 1-ii are nearly parallel to each other. 70°≦θC≦110° Furthermore, in order to increase the holding strength, it is preferable that the following conditions be satisfied: 85°≦θC≦95° It is more preferable that the following conditions be satisfied:

[0038] 14, when using a holding member 70 shaped to cover the outer peripheries of the first and second light guide members 1-i and 1-ii, it is desirable to provide an opening InAP through which the light beam enters the first light guide member 1-i and an opening OutAP through which the light beam exits the second light guide member 1-ii in the holding member 70. The openings InAP and OutAP may be provided as a single opening.

[0039] Next, a method for fabricating the first and second light guide members 1-i and 1-ii by depositing films on transparent substrates 30-i and 30-ii (hereinafter collectively referred to as 30) will be described. Figures 15(a) and 15(b) show the relationship between the film deposition source and the transparent substrate 30 as viewed from the Y and Z directions, respectively. The transparent substrate 30 has the shape of the first and second light guide members 1-i and 1-ii to be ultimately joined. As shown in Figure 15(b), the holders that hold each transparent substrate do not hold the joint C of each transparent substrate, but rather hold the vicinity of the Y-direction end (indicated by the dashed line), which is an area where no light beam is incident. By depositing a film on each transparent substrate in this state, it is possible to deposit a film from one end to the other end in the X direction.

[0040] Furthermore, by arranging multiple transparent substrates in the X direction and performing film formation on them, simultaneous film formation on multiple transparent substrates is possible. Furthermore, as shown in Figure 15(c), multiple transparent substrates can be arranged in the circumferential direction and height direction of a cylindrical member 80 with the X direction as the tangent direction. The cylindrical member 80 rotates around an axis extending in the Y direction with its circumferential surface facing the film formation source. This allows simultaneous film formation on multiple transparent substrates.

[0041] 16, an optical film may be formed on a transparent substrate (first substrate or second substrate) 90 large enough to encompass multiple transparent substrates 30, and then multiple light guide members (first light guide members or second light guide members) may be cut out from the transparent substrate 90. During film formation, a mask corresponding to the film formation area and the need to hold the transparent substrate 90 is required, and a non-film formation area 91 is created around the periphery of the transparent substrate 90. By performing cutting (dicing) to cut out multiple light guide members from the film formation area that avoids the non-film formation area 91, multiple light guide members with films formed to one end or the other end can be produced simultaneously.

[0042] Although the transparent substrate 90 in Fig. 16 is circular, it may be rectangular. Furthermore, by attaching the transparent substrate 90 to a cylindrical member 80 as shown in Fig. 15(c) and performing film formation, it is possible to manufacture a plurality of light guide members more efficiently. [Example]

[0043] 17 shows the configuration of the image generating unit 200 of Example 2. In the image generating unit 200, components common to the image generating unit 100 of Example 1 are denoted by the same reference numerals as in Example 1, and their explanation will be omitted. The image generating unit 200 of this example differs from Example 1 in that the end faces C2 in the X direction of the first and second light guiding members 1-i and 1-ii are joined together by optical contact.

[0044] In the first embodiment, the end faces C1 having a surface accuracy equal to or less than the wavelength of the light beam are brought into close contact with each other to produce an integrated light guide element, but a holding mechanism is required to maintain the joint between the end faces C1.

[0045] In this embodiment, the end faces C2, whose surface precision is ensured to be equal to or less than the wavelength of the light beam, are brought into close contact with each other, and then heated to fuse them together through intermolecular migration. This eliminates the need for a holding mechanism, making it possible to reduce the size of the image generating unit 200 and increase the strength of the light guide element.

[0046] When the angle between the end surface (fused surface) C2 and the surface R1 on which the optical film is provided is θC, 10°≦θC≦170° It is preferable that the following conditions are satisfied. In addition, the larger the area of ​​the end face C2, the more the bonding strength can be improved. 10°≦θC≦70° or 110°≦θC≦170° It is more preferable that the following conditions be satisfied: [Example]

[0047] 18 shows the configuration of an image generating unit 300 of Example 3. In the image generating unit 300, components common to the image generating unit 100 of Example 1 are denoted by the same reference numerals as in Example 1, and a description thereof will be omitted. The image generating unit 300 of this example differs from Example 2 in that the end faces C3 in the X direction of the first and second light guide members 1-i and 1-ii are joined together with an adhesive B.

[0048] In Examples 1 and 2, the end faces C1 and C2 require high surface precision equal to or less than the wavelength of the light beam, and when the light guide member is cut out by cutting the substrate 90, for example, as shown in Figure 16, the cross section needs to be polished. Furthermore, heating is also required to cause intermolecular movement by optical contact as in Example 2, which requires many manufacturing steps. In contrast, in this Example, adhesive B is used for bonding, so polishing of the end faces after cutting and heating after adhesion are not required.

[0049] By using adhesive B with the same (or considered to be the same) refractive index as that of the transparent substrates 30-i and 30-ii, it is possible to transmit the light beam between the end faces C3 without causing refraction or reflection. When the refractive index of the transparent substrates 30-i and 30-ii is n1 and the refractive index of adhesive B is n2, 0.9≦n1 / n2≦1.1 It is preferable that the following condition be satisfied (so that n1 = n2). Also, an adhesive that hardens under UV light is preferable as adhesive B. It is preferable to form an adhesive reservoir (not shown) outside the effective surfaces so that adhesive B does not spill onto the effective surfaces R1 and R2. [Example]

[0050] 19 shows the configuration of an image generating unit 400 according to the fourth embodiment. In the image generating unit 400, components common to the image generating unit 100 according to the first embodiment are denoted by the same reference numerals as in the first embodiment, and a description thereof will be omitted.

[0051] The image generating unit 400 of this embodiment differs from that of Example 1 in that a plurality of optical films (dielectric multilayer films) 12-i, 12-ii, and 12-iii having different characteristics (emission efficiency) are formed in the region (R1 surface) of the light-guiding member (2-i to 2-iii) that emits the light beam toward the display element 60, which corresponds to the second light-guiding member 1-ii of Example 1.

[0052] By forming optical films 12-i, 12-ii, and 12-iii with different properties, it is possible to make the amount of light that passes through each optical film and exits uniform, thereby improving the uniformity of the illumination brightness on the display element 60. Table 1 shows the amount of light incident on, the amount of light that exits, and the emission efficiency of the optical films (first to third regions) 12-i, 12-ii, and 12-iii, and also shows the amount of light that is reflected by each optical film and propagates to the adjacent optical film.

[0053] [Table 1]

[0054] In order to form the optical films 12-i to 12-iii on the R1 surfaces of the light guide members 2-i to 2-iii without gaps or overlaps, the optical films 12-i, 12-ii, and 12-iii are formed on the transparent substrates 30-iv, 30-v, and 30-vi, respectively. Then, the end faces C4, C5, and C6 of the light guide members 2-i to 2-iii in the X direction are joined. That is, the light guide members 2-i to 2-iii can be manufactured in the same manner as the light guide elements of Examples 1 to 3.

[0055] FIG. 20 shows the characteristics of the dielectric multilayer film used as the optical film (second optical film) 12-i shown in FIG. 19. This dielectric multilayer film does not have a deflecting effect. Therefore, the light beam emitted from the optical film 12-i travels in a direction inclined relative to the normal to the exit surface (R1 surface) of the first light guide member 2-i. In this embodiment, the display element 60 is assumed to be a micromirror element (digital micromirror device: DMD) with a two-dimensional array of tiny micromirrors. The DMD used as the display element 60 forms an image by switching the tilt (ON / OFF) of the micromirrors for each pixel onto which the illumination light beam is obliquely incident, thereby controlling the deflection direction of the reflected image light beam. The image light beam reflected and deflected by the micromirrors exits along the normal to the display element 60 and then perpendicularly enters the R1 surface of the same or another light guide member. Here, the perpendicular angle is within a range of ±5° relative to the normal to the R1 surface.

[0056] As shown in Fig. 20, the dielectric multilayer film has different characteristics depending on the incident angle, utilizing the incident angle characteristics of the dielectric. Specifically, it has the characteristic of partially reflecting a light beam incident at an angle and transmitting most of a light beam incident perpendicularly. In this embodiment, when the incident angle of the illumination light incident on the dielectric multilayer film is θin and the incident angle of the image light incident on the dielectric multilayer film is θout, |θin-θout|≧30° It is set to satisfy the following conditions.

[0057] 21 shows the configuration of an image generating unit 400-a that uses, as a display element 61, an element that forms an image light beam by controlling the polarization state of light, such as a liquid crystal element. Since the characteristics of the display element 61 change depending on the angle of the incident light beam, it is desirable to make the illumination light beam incident perpendicular to the effective surface of the display element 61. In order to make the illumination light beam incident perpendicular to the display element 61, the light guide element may be tilted and arranged so that the illumination light beam emitted from the light guide element is incident perpendicularly (90±5°) on the display element 61, as shown in the same figure.

[0058] 21 is difficult, a deflection element 62 may be disposed between the exit surface (R1 surface) of the light guide element and the display element 61, as in the image generating unit 400-b shown in FIG. 22. The deflection element 62 deflects the illumination light beam that is obliquely emitted from the exit surface of the light guide element and guides it perpendicularly to the display element 61. The deflection element 62 may have any of the functions of refraction, reflection, and diffraction on the incident light beam. In order to emit the illumination light beam from the exit surface of the light guide element without any gaps in the X direction, as described above, when the length in the X direction of each optical film (12-i, 12-ii, 12-iii) is W2, and the width in the X direction of the illumination light beam incident on each optical film (before reflection) as shown in FIG. 23 is W3, 0.9≦W2 / W3≦1.1 It is preferable to satisfy the following conditions. [Example]

[0059] 24 shows the configuration of an image display device 500 of Example 5. The image display device 500 differs from Examples 1 to 4 in that it has the image generation section (light generation section) 100 of Example 1 instead of a light source section, and the image light beam emitted from the light guide element formed by the first and second light guide members 3-i and 3-ii is directed to the viewer's eye (pupil) EP instead of a display element. In the image display device 500, components common to Example 1 are assigned the same reference numerals as in Example 1, and a description thereof will be omitted.

[0060] The image display device 500 allows an observer to view information about the outside world while observing a display image via a light-guiding element. That is, the second light-guiding member 3-ii of the image display device 500 needs to ensure transmittance for outside light. Specifically, surfaces other than the exit surface (R1 surface) 13 of the second light-guiding member 3-ii, i.e., the R1 and R2 surfaces of the first light-guiding member 3-i and the R2 surface of the second light-guiding member 3-ii, are either uncoated or provided with an AR (anti-reflection) coating to increase transmittance for outside light.

[0061] The image light beam incident on the first light guide member 3-i from the image generating unit 100 propagates through the first and second light guide members 3-i and 3-ii with almost no loss due to total reflection, and a portion of the light is emitted toward the pupil EP from the optical film formed on the exit surface 13 of the second light guide member 3-ii. The dielectric multilayer film, which serves as a transflective film, has partially controlled transmittance and reflectance. The first light guide member 3-i, which is uncoated or AR-coated, and the second light guide member 3-ii, which has a dielectric multilayer film formed on its exit surface 13, are separately manufactured. Then, by bringing their end faces C7 in the X direction into close contact with each other, a light guide element having a dielectric multilayer film formed from one end to the other of the exit surface 13 can be obtained.

[0062] Furthermore, by emitting the image light beams one by one from the exit surface 13, the range within which the observer can see the displayed image (visible range) can be expanded, and the displayed image can be seen without any gaps even if the observer's pupil EP moves.

[0063] In FIG. 24, a portion of the image light beam is emitted in the X direction, but it is also possible to emit a portion of the image light beam in the Y direction using the same principle, thereby expanding the visible range in two dimensions.

[0064] The dielectric multilayer film formed on the exit surface 13 may have the same characteristics at all positions in the X direction, or may be a gradient film whose film thickness is controlled for each position. Also, as in Example 4, it may be configured with a plurality of optical films whose characteristics are different from each other. [Example]

[0065] FIG. 25 shows the configuration of an image display device 600 according to a sixth embodiment. In the image display device 600, first to third light guide members 4-i, 4-ii, and 4-iii are joined together to form a light guide element. Optical films 14-ii and 15-ii provided on the R1 and R2 surfaces of the second light guide member 4-ii are inclined relative to the optical films 14-i, 15-i, and 14-iii of the first and third light guide members 4-ii and 4-iii. Each optical film is a dielectric multilayer film. In the image display device 600, components common to the image generating device 500 according to the fifth embodiment are denoted by the same reference numerals as in the fifth embodiment, and their description will be omitted. In this embodiment, the second light guide member 4-ii corresponds to the first light guide member, and the third light guide member 4-iii corresponds to the second light guide member.

[0066] In the image display device 600, the image light flux emitted from the image generating unit 100 of the first embodiment is incident on the first light guiding member 4-i at a shallow angle. Note that, although Fig. 25 shows the chief ray of the image light flux emitted from the image generating unit 100, it may be a light ray incident at the shallowest angle within the viewing angle visible to the observer.

[0067] In order for the chief ray, which has a shallow propagation angle within the light guide element, to propagate to the viewer's pupil EP, a large number of reflections are required. Generally, in eyeglass-type wearable devices, the image generation unit 100 is placed in a portion corresponding to the eyeglass frame (string), and is at a certain distance from the viewer's pupil EP. If the number of reflections at the optical film is large (the incident angle of the image light beam is small), the loss due to absorption cannot be ignored even if the optical film is made of a dielectric multilayer film.

[0068] In this embodiment, the incident angle of the image light beam with respect to the optical film is changed within the light guide element by joining the first to third light guide members 4-i, 4-ii, and 4-iii together such that the optical films 14-ii and 15-ii of the second light guide member 4-ii are inclined relative to the optical films 14-i, 15-i, and 14-iii of the first and third light guide members 4-ii and 4-iii.

[0069] The image light beam incident from the image generation unit 100 propagates in the X direction within the first light guiding member 4-i while being alternately reflected by the optical films 14-i and 15-i, which are reflective films. Because the angle at which the image light beam propagates within the first light guiding member 4-i is shallow enough not to satisfy the total reflection condition, the optical films 14-i and 15-i are made of dielectric multilayer films that reflect at least a part of the image light beam in the wavelength band contained in the incident image light beam.

[0070] The image light flux propagates through the first light guide member 4-i, passes through the end face C8, and enters the second light guide member 4-ii. The image light flux propagates in the X direction while being alternately reflected by the optical films 14-ii and 15-ii, which are reflective films of the second light guide member 4-ii that are inclined relative to the optical films 14-i and 15-i of the first light guide member 4-i. The angle of incidence of the image light flux on the optical films 14-ii and 15-ii is larger than the angle of incidence of the image light flux on the optical films 14-i and 15-i. This allows the propagation interval of the image light flux in the second light guide member 4-ii to be wider than in the first light guide member 4-i, and reduces absorption of the image light flux by the optical films 14-ii and 15-ii.

[0071] The image light beam propagates through the second light-guiding member 4-ii, passes through the end face C9, and enters the third light-guiding member 4-iii. The image light beam propagates while being alternately reflected by the optical film 14-iii, a transmissive / reflective film provided on the R1 surface of the third light-guiding member 4-iii, and the R2 surface. During this process, a portion of the light beam passes through the optical film 14-iii and exits toward the pupil EP. To enable observation of the outside world, the R2 surface of the third light-guiding member 4-iii is either uncoated or anti-reflection coated to ensure transmittance for external light. By tilting the second light-guiding member 4-ii relative to the first and third light-guiding members 4-i and 4-iii, the propagation angle of the image light beam within the light-guiding element is changed, and the R2 surface of the third light-guiding member 4-iii satisfies the total reflection condition.

[0072] Although FIG. 25 shows a case where the image light beam is incident on the pupil EP obliquely, as explained in the fourth embodiment, the light-guiding element may be tilted or a deflector element may be provided between the light-guiding element and the pupil so that the image light beam is incident on the pupil EP from a direction perpendicular to the pupil EP.

[0073] [Application example] FIG. 26 shows a head-mounted display (HMD) or smart glasses as an image display system using the image display device 500 of Example 5. A frame 700 holds the image display devices 500 for the right and left eyes such that the exit surfaces 13 of the light guide elements are positioned in front of the right and left eyes of an observer 1000. Image light beams emitted from the image generating units 100 of the image display devices 500 for the right and left eyes are guided to the right and left eyes of the observer 1000 via the light guide elements (3-i, 3-ii). This allows the observer 1000 to view a display image 1100. Displaying display images having parallax between the right and left eyes can also allow the observer to view a stereoscopic image.

[0074] A control unit 730 is connected to the frame 700. The control unit 730 controls the driving of the display elements in the image generating unit 100 and the light intensity of the light source unit 50. The control unit 730 may be arranged outside the frame 700 and connected to the image generating unit 100 so as to be able to communicate with it via wire or wirelessly, or may be arranged inside the frame 700.

[0075] Furthermore, a first information acquisition unit 710 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 700. A control unit 730 corrects the position of the display image 1100 (the position where the image is generated on the display element) based on the pupil information. A second information acquisition unit 720 including a camera that acquires external world (surroundings) information is also attached to the frame 700. The control unit 730 adjusts the brightness of the display image 1100 according to the brightness of the external world obtained from the external world information.

[0076] 27 shows a head-up display (HUD) 750 as an in-vehicle image display system using the image generation unit 100 of the first embodiment. The HUD 750 includes an image generation unit 100a, a projection optical system 800, a first information acquisition unit 720a, a second information acquisition unit 710a, and a control unit 730a. The HUD 750 is mounted on an automobile 900 as a moving device, and projects and displays an image (virtual image) 1100a for supporting a user (driver or passengers) of the automobile 900 onto a windshield as a projection surface via the projection optical system 800. Note that the moving device may be a train, a ship, an airplane, or the like, in addition to an automobile.

[0077] The first information acquisition unit 720a includes a camera that acquires pupil information indicating the position and movement (point of view or line of sight) of the user's pupil EP. The control unit 730a corrects the position of the display image 1100a (the position where the image is generated on the display element) based on the pupil information. The second information acquisition unit 710a includes a camera that acquires external world information. The control unit 730a adjusts the brightness of the display image 1100a according to the brightness of the external world obtained from the external world information, and superimposes the display image 1100a on the external world image obtained from the external world information. The second information acquisition unit 710a may acquire external world information not only from the front, but also from behind, to the sides, etc.

[0078] The control unit 730a determines the possibility of collision of the automobile 900 with an obstacle (object) obtained from external world information, and if there is a possibility of collision, issues a warning or controls any of the drive units (engine, motor, etc.), brakes, and steering of the automobile 900. Warning methods include issuing a warning sound, displaying warning information on the display screen of the car navigation system, and generating vibrations in the seat belt or steering.

[0079] 28 shows the configuration of an image projection device (projector) as an image display system using the image generation unit 100 of the first embodiment. An image light beam emitted from the image generation unit 100b is projected onto a projection surface 1100b such as a screen via a projection optical system 800a. The projection surface 1100b may be flat or curved. The control unit 730b drives the display element in response to an image signal input from the outside, adjusts the light intensity of the light source unit 50, and adjusts the zoom and focus of the projection optical system 800a.

[0080] In the image display systems shown in FIGS. 26 to 28, the image generating units or image display devices of other embodiments may be used.

[0081] The above embodiment includes the following configurations and manufacturing methods.

[0082] (Configuration 1) A light guide element having a first light guide portion that propagates an incident light beam while reflecting it therein, and a second light guide portion that reflects the light beam from the first light guide portion therein and emits a portion of the light beam at a time, a first optical film is provided in the first light guiding portion, and a second optical film having characteristics different from those of the first optical film is provided in the second light guiding portion so as to be adjacent to the first optical film; A light guide element, wherein a first light guide member constituting the first light guide portion and a second light guide member constituting the second light guide portion are in close contact with or joined to each other. (Configuration 2) the first optical film is a reflective film, 2. The light guide element according to configuration 1, wherein the second optical film is a transflective film. (Configuration 3) When the angle formed between the surfaces where the first and second light guide members are in close contact or bonded and the surfaces where the first and second optical films are provided in the first and second light guide members is θC, 10°≦θC≦170° 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 surfaces where the first and second light guide members are in close contact or bonded together are surfaces where no optical film is provided. (Configuration 5) 5. The light guide element according to any one of configurations 1 to 4, wherein the first and second light guide members are joined by optical contact. (Configuration 6) 6. The light guide element according to any one of configurations 1 to 5, wherein the first and second light guide members are joined together with an adhesive. (Configuration 7) 7. The light guide element according to any one of configurations 1 to 6, wherein at least one of the first and second optical films is a dielectric multilayer film. (Configuration 8) the first and second optical films are provided adjacent to each other on first surfaces of the first and second light guide members, 8. The light guide element according to any one of configurations 1 to 7, wherein an optical film identical to the first optical film is provided on the second surfaces of the first and second light guide members. (Configuration 9) In the propagation direction of light within the light-guiding element, when the length of the light-transmitting substrate that is the base member of each of the first and second light-guiding members is W1 and the length of each of the first and second optical films formed on the light-transmitting substrate is W2, 0.95≦W1 / W2≦1.05 9. The light guide element according to any one of configurations 1 to 8, which satisfies the following conditions: (Configuration 10) 10. The light guide element according to any one of configurations 1 to 9, wherein the first light guide member and the second light guide member are in close contact or bonded together such that the first optical film and the second optical film are inclined relative to each other. (Configuration 11) The light guide element according to any one of configurations 1 to 10; a light generating unit that outputs the light beam incident on the light-guiding element, An image display device, characterized in that the light beam emitted from the light guide element is guided to a display element or an observer's eye. (Configuration 12) When the incident angle of the light beam on the surface of the first light-guiding member on which the first optical film is provided is θ and the refractive index of the light-guiding substrate at the d-line is nd, at least a part of the light beam is θ<(asin(1 / nd)) 12. The image display device according to configuration 11, which satisfies the following conditions: (Configuration 13) In the propagation direction of light within the light-guiding element, when the length of each of the first and second optical films is W2 and the width of the light beam incident on each of the first and second optical films is W3, 0.9≦W2 / W3≦1.1 13. The image display device according to configuration 11 or 12, which satisfies the following conditions: (Configuration 14) A method for manufacturing a light guide element having a first light guide portion that propagates an incident light beam while reflecting the light beam therein, and a second light guide portion that reflects the light beam from the first light guide portion therein and emits the light beam at a time, the method comprising: preparing a first light guiding member provided with a first optical film as a member constituting the first light guiding portion; preparing a second light guiding member provided with a second optical film having characteristics different from those of the first optical film as a member constituting the second light guiding portion; a step of closely adhering or bonding the first light-guiding member and the second light-guiding member so that the first optical film and the second optical film are adjacent to each other. (Configuration 15) The step of preparing the first and second light guide members includes: forming the first optical film on a light-transmitting substrate that is a base member of the first light guide member; 15. The manufacturing method according to configuration 14, further comprising the step of forming the second optical film on a light-transmitting substrate that is a base member of the second light-guiding member. (Configuration 16) The step of preparing the first and second light guide members includes: forming the first optical film on a first substrate including a plurality of regions corresponding to a light-transmitting substrate that is a base member of the first light guide member; forming the second optical film on a second substrate including a plurality of regions corresponding to a light-transmitting substrate that is a base member of the second light guide member; and cutting out the first light guide member and the second light guide member from the first substrate and the second substrate, respectively.

[0083] 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]

[0084] 1, 2, 3, 4 (-i, -ii, -iii) Light guide member 10,11,12,13,14(-i,-ii,-iii) Optical film 30(-i,-ii) Transparent substrate 60,61 Display element 100,200,300,400 Image generation unit 500,600 image display devices

Claims

1. A light guide element having a first light guide portion that propagates an incident light beam while reflecting the light beam therein, and a second light guide portion that reflects the light beam from the first light guide portion therein and emits the light beam at a time in portions, a first optical film is provided in the first light guiding portion, and a second optical film having characteristics different from those of the first optical film is provided in the second light guiding portion so as to be adjacent to the first optical film; A light guide element, characterized in that a first light guide member constituting the first light guide portion and a second light guide member constituting the second light guide portion are in close contact with or joined to each other.

2. the first optical film is a reflective film, The light guide element according to claim 1 , wherein the second optical film is a transflective film.

3. When the angle formed between the surfaces where the first and second light guide members are in close contact or bonded and the surfaces where the first and second optical films are provided in the first and second light guide members is θC, 10°≦θC≦170° 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 surfaces where the first and second light guide members are in close contact or bonded together are surfaces where no optical film is provided.

5. 2. The light guide element according to claim 1, wherein the first and second light guide members are joined by optical contact.

6. 2. The light guide element according to claim 1, wherein the first and second light guide members are joined together with an adhesive.

7. 2. The light guide element according to claim 1, wherein at least one of the first and second optical films is a dielectric multilayer film.

8. the first and second optical films are provided adjacent to each other on first surfaces of the first and second light guide members, The light guide element according to claim 1 , wherein an optical film identical to the first optical film is provided on the second surfaces of the first and second light guide members.

9. In the light propagation direction within the light-guiding element, when the length of a light-transmitting substrate that is a base member of each of the first and second light-guiding members is W1 and the length of each of the first and second optical films formed on the light-transmitting substrate is W2, 0.95≦W1 / W2≦1.05 2. The light guide element according to claim 1, wherein the following conditions are satisfied:

10. The light guide element according to claim 1 , wherein the first light guide member and the second light guide member are in close contact or bonded together such that the first optical film and the second optical film are inclined relative to each other.

11. The light guide element according to claim 1 ; a light generating unit that outputs the light beam incident on the light-guiding element, An image display device, characterized in that the light beam emitted from the light guide element is guided to a display element or an observer's eye.

12. When the incident angle of the light beam on the surface of the first light-guiding member on which the first optical film is provided is θ and the refractive index of the light-guiding substrate at the d-line is nd, at least a part of the light beam is θ<(asin(1 / nd)) 12. The image display device according to claim 11, wherein the following condition is satisfied:

13. In the propagation direction of light within the light-guiding element, when the length of each of the first and second optical films is W2 and the width of the light beam incident on each of the first and second optical films is W3, 0.9≦W2 / W3≦1.1 12. The image display device according to claim 11, wherein the following condition is satisfied:

14. A method for manufacturing a light guide element having a first light guide portion that propagates an incident light beam while reflecting the light beam therein, and a second light guide portion that reflects the light beam from the first light guide portion therein and emits the light beam at a time in portions, preparing a first light guide member provided with a first optical film as a member constituting the first light guide portion; preparing a second light guiding member provided with a second optical film having characteristics different from those of the first optical film as a member constituting the second light guiding portion; a step of closely adhering or bonding the first light-guiding member and the second light-guiding member so that the first optical film and the second optical film are adjacent to each other.

15. The step of preparing the first and second light guide members includes: forming the first optical film on a plurality of light-transmitting substrates, each of which is a base member of the first light guide member; The manufacturing method according to claim 14 , further comprising the step of forming the second optical film on a plurality of light-transmitting substrates, each of which is a base member of the second light-guiding member.

16. The step of preparing the first and second light guide members includes: forming the first optical film on a first substrate including a plurality of regions corresponding to a light-transmitting substrate that is a base member of the first light guide member; forming the second optical film on a second substrate including a plurality of regions corresponding to a light-transmitting substrate that is a base member of the second light guide member; The manufacturing method according to claim 14 , further comprising the step of cutting out the first light guide member and the second light guide member from the first substrate and the second substrate, respectively.

Images