Image display device

Abstract

The invention relates to an image display device. The image display device includes: an image display element configured to emit image light; and a light guide plate including an entry portion into which the image light enters and an exit portion from which the image light exits. The exit portion includes, in order from the entry portion side, a first separation surface and a second separation surface. Each of the first separation surface and the second separation surface is configured to separate incident light into reflected light and transmitted light. A predetermined inequality is satisfied.

Description

Technical Field

[0001] One of the aspects of the embodiments is directed to an image display device having a light guide plate configured to guide a display image (light) to a pupil of an observer. Background Art

[0002] There is conventionally known an image display device having a light guide plate configured to guide a display image to a pupil of an observer. Fig.18 1 is a conceptual diagram of light beams propagating inside a light guide plate of a conventional image display device. Light beams L10, L20, and L30 emitted from pixels of an image display element 110 pass through a projection optical system 1200, enter an entrance portion 1310 at different incident angles, are deflected, and then propagate inside a light guide plate 130 at different total reflection angles α10, α20, and α30 (α10<α20<α30). A portion of the light beam incident on an exit portion 132 is deflected and travels toward an observer's pupil SP, and the other light beams propagate inside the light guide plate 130 by total reflection and enter the exit portion 132. In a conventional image display device, the width of an area (effective area) where the light beams L10, L20, and L30 overlap each other at the position of an observer's pupil SP is smaller than the width of the light beam emitted from the exit portion 132, and a large amount of unnecessary light is generated in the effective area, and light utilization efficiency is significantly reduced.

[0003] Japanese Patent Laid-Open No. 2018-165743 discloses a configuration configured to set an appropriate incident angle range with high reflectivity and low incident angle dependence for multiple separated surfaces deflected at the same angle so as to increase the intensity of each light beam incident on the pupil of the observer. PCT International Publication WO2018 / 221026 discloses a configuration configured to set different light reflectivities for multiple semi-transmissive layers based on angle dependence to reflect light of an angle component incident on the pupil of the observer and transmit light of another angle component so as to improve light guiding efficiency. Summary of the invention

[0004] An image display device according to one aspect of the present disclosure includes: an image display element configured to emit image light; and a light guide plate including an entrance portion and an exit portion, wherein the image light enters the entrance portion and the image light exits from the exit portion. The exit portion includes a first separation surface and a second separation surface in sequence from the entrance portion side. Each of the first separation surface and the second separation surface is configured to separate incident light into reflected light and transmitted light. The following inequality is satisfied:

[0005] R2(θ2)<R1(θ1)<R2(θ1)

[0006] θ1=90-(θM-S(β1))

[0007] θ2=90-(θM-S(β2))

[0008] S(θ)=sin^(-1)(sin(θ) / n)

[0009] β1>β2

[0010] Wherein β1 is the incident angle [°] of light incident from the first separation surface to a predetermined position in the eyebox, β2 is the incident angle [°] of light incident from the second separation surface to the predetermined position, θM is the angle [°] between the first separation surface or the second separation surface and the surface normal of the light guide plate, n is the refractive index of the light guide plate for light with a predetermined wavelength included in the band of the image light, R1(θ) is the reflectivity of the light with the predetermined wavelength incident on the first separation surface at an incident angle θ[°], and R2(θ) is the reflectivity of the light with the predetermined wavelength incident on the second separation surface at an incident angle θ[°].

[0011] Further features of various embodiments of the present disclosure will become apparent from the following description of the embodiments with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is a conceptual diagram of an incident angle and an effective diameter of light on a separation surface in an image display device according to an embodiment of the present disclosure.

[0013] Figure 2 is a conceptual diagram of a light beam propagating inside the light guide plate in this embodiment.

[0014] Figure 3 is a conceptual diagram of the position of the separation surface and the incident angle of light viewed from a predetermined position of the pupil of the observer in this embodiment.

[0015] Figure 4A and Figure 4B is a schematic diagram of multiple separation surfaces in this embodiment.

[0016] Figure 5A , Figure 5B and Figure 5C The figure shows an example configuration of the entry section.

[0017] Fig. 6A , Figure 6B , Figure 6C , Fig.6D and Fig. 6E Other configuration examples of the entry section are illustrated.

[0018] Fig. 7A and Figure 7B Other configuration examples of the entry section are illustrated.

[0019] Figure 8 The configuration of an image display device according to Example 1 is illustrated.

[0020] Fig.9A , Fig. 9B and Fig. 9C Angular characteristics of reflectivity of the dielectric multilayer film according to Example 1 for S-polarized light are illustrated.

[0021] Fig.10 Angular characteristics of reflectivity of the dielectric multilayer film according to Example 1 for P-polarized light are illustrated.

[0022] Fig.11 is a configuration diagram of an image display device according to Example 2.

[0023] Fig. 12A , Fig. 12B and Fig. 12C Angular characteristics of reflectivity of the dielectric multilayer film according to Example 2 for S-polarized light are illustrated.

[0024] Fig.13 Angular characteristics of reflectivity of the dielectric multilayer film according to Example 2 for P-polarized light are illustrated.

[0025] Fig.14 is a configuration diagram of an image display device according to Example 3.

[0026] Fig.15A , Fig. 15B and Fig. 15C Angular characteristics of reflectivity of the dielectric multilayer film according to Example 3 for S-polarized light are illustrated.

[0027] Fig.16 is a configuration diagram of an image display device according to Example 4.

[0028] Fig.17A , Fig. 17B and Fig. 17C Angular characteristics of reflectivity of the dielectric multilayer film according to Example 4 for S-polarized light are illustrated.

[0029] Fig.18 This is a conceptual diagram of a light beam propagating inside a light guide plate in a conventional image display device. DETAILED DESCRIPTION

[0030] Now, with reference to the accompanying drawings, a detailed description of embodiments according to the present disclosure will be given. Corresponding elements in various figures will be marked with the same reference numerals, and their repeated description will be omitted.

[0031] Figure 1 1 is a conceptual diagram of the incident angle and effective diameter of light on a separation surface in an image display device according to an embodiment of the present disclosure. The image display device includes an image display element (image generating element) 1 configured to emit image light (image display light), a projection optical system 2, and a light guide plate 3 having an entrance portion 31 for image light to enter and an exit portion 32 for image light to exit. For example, a combination of a liquid crystal panel and an illumination optical system can be used as the image display element 1. A self-luminous display in which a light source (OLED or LED) is deployed for each pixel, or a combination of a microelectromechanical system (MEMS) and a laser light source can be used as the image display element 1. The projection optical system 2 includes an optical element such as a lens, a diffractive optical element, a holographic element, or a metasurface.

[0032] Light beams L1, L2, and L3 emitted from the pixels of the image display element 1 enter the projection optical system 2, enter the entrance portion 31 at different angles, are deflected, and then propagate through the light guide plate 3 at different total reflection angles α1, α2, and α3 (α1<α2<α3). A portion of the light beams entering the exit portion 32 are deflected toward the pupil SP of the observer, while the other light beams propagate through the light guide plate 3 by total reflection and enter the exit portion 32.

[0033] In this embodiment, the exit portion 32 has a plurality of separation surfaces. Each separation surface is configured to separate incident light into reflected light and transmitted light. This embodiment appropriately sets the angular characteristics of the reflectivity of the plurality of separation surfaces so as to reflect the light of the angle component entering the pupil SP of the observer and transmit the light of the other angle components, thereby achieving high light utilization efficiency.

[0034] The wavelength range and polarization component of the image light emitted from the image display element 1 can be appropriately set according to the configuration of the entrance portion 31, the extension portion, and the exit portion 32. For example, the image display element can be configured to emit monochromatic light using only a green laser light source.

[0035] A description will now be given of the angular characteristics of the reflectance of a plurality of separation surfaces. Figure 2: is a conceptual diagram of a light beam propagating inside the light guide plate 3 according to this embodiment. Separation surfaces M1, M2 and M3 are provided in sequence from the -y side (the side closer to the entrance portion 31) to the +y side (the side farther from the entrance portion 31). In order to extract the light entering the pupil SP of the observer, the corresponding separation surfaces are to reflect light beams with different total reflection angles. The light beams with corresponding total reflection angles of the separation surfaces M1, M2 and M3 will be referred to as light L1, L2 and L3, respectively. The incident angles θ1, θ2 and θ3 of the angular components of the light entering the pupil SP of the observer on the separation surfaces M1, M2 and M3 have the following relationship.

[0036] θ1>θ2>θ3Therefore, in the separation surface on the -y side, the reflectivity corresponding to the large incident angle in the incident angle range in the light path deflected toward the pupil SP of the observer increases, and the reflectivity corresponding to the small incident angle decreases. In the separation surface on the +y side, the reflectivity corresponding to the small incident angle in the incident angle range in the light path deflected toward the pupil SP of the observer increases. This configuration can achieve high light utilization efficiency.

[0037] A description will now be given of the relationship between the reflectances of the separation surfaces and the relationship between the reflectances within the separation surfaces. Figure 2 , the optically effective diameters A1, A2 and A3 of the separation surfaces M1, M2 and M3 have the following relationship.

[0038] A1<A2<A3

[0039] By setting the angular characteristics of the reflectivity to correct the relationship between the optically effective diameters of the separation surfaces, the light beams emitted from each separation surface at different departure angles become uniform. That is, for a separation surface having a small optically effective diameter, the reflectivity for the corresponding light can be set high, and for a separation surface having a large optically effective diameter, the reflectivity for the corresponding light can be set low. The reflectivities R1(θ), R2(θ), and R3(θ) of the incident light (the light of a predetermined wavelength included in the image light band of the light guide plate 3) incident at an incident angle θ on each of the separation surfaces M1, M2, and M3 satisfy the following inequality (1):

[0040] R1(θ1)>R2(θ2)>R3(θ3) (1)

[0041] The reflectivity of the separation surface on the -y side (the side closer to the entrance portion 31) of the light at a predetermined incident angle in the incident angle range in the optical path deflected toward the pupil SP of the observer decreases, and the reflectivity of the separation surface on the +y side (the side farther from the entrance portion 31) increases. As a result, the light beams of the same departure angle reflected by the plurality of separation surfaces become uniform. Since the light beams are reflected by the separation surfaces on the -y side, in order to obtain similar light beams on the separation surfaces on the +y side, the reflectivity is relatively high. Therefore, the reflectivities R1(θ1), R2(θ1), and R3(θ1) of the incident light beams incident on each of the separation surfaces M1, M2, and M3 at the incident angle θ1 satisfy the following inequality (2):

[0042] R1(θ1)<R2(θ1)<R3(θ1) (2)

[0043] From inequalities (1) and (2), the reflectivity of the separation surfaces M1 and M2 satisfies the following inequality (3):

[0044] R2(θ2)<R1(θ1)<R2(θ1) (3)

[0045] A plurality of separation surfaces satisfying inequality (3) can realize an image display device having uniform luminance over a viewing angle range incident on the pupil SP of an observer with high light utilization efficiency.

[0046] Figure 3 θ1[°] and θ2[°] of light incident on the predetermined position on the pupil SP of the observer from the separation surfaces M1 and M2 are expressed using the following equations:

[0047] θ1=90-(θM-S(β1))

[0048] θ2=90-(θM-S(β2))

[0049] S(θ)=sin^(-1)(sin(θ) / n)

[0050] Here, β1 is an incident angle [°] of light incident from the separation surface M1 on a predetermined position on the pupil SP of the observer. β2 is an incident angle [°] of light incident from the separation surface M2 on a predetermined position on the pupil SP of the observer. The incident angle β1 is greater than the incident angle β2. θM is an angle [°] between each separation surface and the surface normal of the light guide plate 3. n is a refractive index for light of a predetermined wavelength included in the image light band of the light guide plate 3. S(θ) indicates refraction according to Snell's law.

[0051] Figure 4A and Figure 4B is a schematic diagram of a plurality of separation surfaces according to this embodiment. Figure 4A The diagram shows that the angle θM between each separation surface and the surface normal of the light guide plate 3 is greater than 0° and less than 45°. In this case, each separation surface transmits light in a relatively vertical incident angle range and reflects light in a relatively inclined incident angle range, thereby deflecting the light toward the pupil SP of the observer. The incident angle characteristics of the reflectivity at this time are obtained by using a dielectric multilayer film for each separation surface. More specifically, each separation surface includes a dielectric multilayer film that transmits P polarized light and has the above incident angle characteristics for S polarized light. In the relatively inclined incident angle range of S polarized light, satisfying inequality (3) can achieve uniform luminance over the field angle range where light is incident on the pupil SP of the observer with high utilization efficiency.

[0052] exist Figure 4A In the case of , the following inequality (4) can be satisfied:

[0053] 1.0<R1(θ1) / R2(θ2)<5.0 (4)

[0054] Inequality (4) defines the reflectivity for correcting the relationship between the optically effective diameters of the separation surfaces. When the value becomes higher than the upper limit, the reflectivity becomes over-corrected for the relationship between the optically effective diameters of the separation surfaces, and the light beams with different departure angles extracted from the respective separation surfaces become uneven.

[0055] Inequality (4) can be replaced by the following inequality (4a):

[0056] 1.0<R1(θ1) / R2(θ2)<4.0 (4a)

[0057] Inequality (4) can be replaced by the following inequality (4b):

[0058] 1.0<R1(θ1) / R2(θ2)<3.0 (4b)

[0059] In this embodiment, the following inequality (5) can be satisfied:

[0060] 90-θM-5≤κ≤90-θM+5 (5)

[0061] Inequality (5) can be replaced by the following inequality (5a):

[0062] 85-θM≤κ≤95-θM (5a)

[0063] where κ is the Brewster condition for the dielectric multilayer at each separation surface and is expressed by the following equation:

[0064]

[0065] Here, n H It is the refractive index of the high refractive index film constituting the dielectric multilayer film with respect to light having a predetermined wavelength included in the image light band. L The refractive index of the low refractive index film constituting the dielectric multilayer film for the light having a predetermined wavelength included in the image light band. The light having a predetermined wavelength included in the image light band is, for example, light having a dominant wavelength. The dominant wavelength is, for example, the peak wavelength of the image light band.

[0066] The angle ranges on the left and right sides of inequality (5) are relatively inclined incident angle ranges. Satisfying inequality (5) can achieve a configuration that transmits P-polarized light.

[0067] Figure 4B The diagram shows that the angle θM between each separation surface and the surface normal of the light guide plate 3 is greater than 45° and less than 90°. In this case, each separation surface reflects light in a relatively vertical incident angle range and transmits light in a relatively inclined incident angle range, so that the light can be deflected toward the pupil SP of the observer. The incident angle characteristics of the reflectivity in this case are obtained by using a dielectric multilayer film for each separation surface. More specifically, each separation surface is configured using a dielectric multilayer film that transmits S-polarized light and has the above incident angle characteristics for P-polarized light. In the relatively inclined incident angle range of P-polarized light, each separation surface satisfies inequality (5) and achieves uniform luminance in the field of view angle range incident on the pupil SP of the observer with high utilization efficiency.

[0068] exist Figure 4B In the case of , the following inequality (6) can be satisfied:

[0069] 1.0<R1(θ1) / R2(θ2)<4.0 (6)

[0070] Inequality (6) defines the reflectivity for correcting the relationship between the optically effective diameters of the separation surfaces. When the value becomes higher than the upper limit of inequality (6), the reflectivity is over-corrected for the relationship between the optically effective diameters of the separation surfaces, and the light beams with different departure angles extracted from the separation surfaces are not uniform.

[0071] Inequality (6) can be replaced by the following inequality (6a):

[0072] 1.0<R1(θ1) / R2(θ2)<3.0 (6a)

[0073] Inequality (6) can be replaced by the following inequality (6b):

[0074] 1.0<R1(θ1) / R2(θ2)<2.0 (6b)

[0075] A description will now be given of a configuration example of the entry section 31. FIG. 5A to FIG. 7B The diagram shows an example of a configuration of the entry section 31. The entry section 31 may be configured as follows: Figure 5A and Figure 5B The prismatic element 61 shown in FIG. Figure 5C The reflective surface 62 shown in FIG. Fig. 6A As shown in FIG. 3 , the entrance portion 31 may use a diffractive optical element 71. The efficiency and diffraction angle of each diffraction order may be controlled by changing the shape and height of the grating structure of the diffractive optical element 71, as well as the refractive index. Figure 6B , Figure 6C , Fig.6D and Fig. 6E As shown in , and can be determined according to the requirements of the image display device. The entrance portion 31 can use a holographic element. Fig. 7A and Figure 7B As shown in , the entrance portion 31 may be configured to allow the light beam from the projection optical system 2 to enter the light guide plate 3 at an inclined angle relative to the normal line of the incident surface of the light guide plate 3 , and guide the light into the light guide plate 3 through the reflective surface 81 .

[0076] The specific configuration according to each example will be described below. In each example, the image display device emits three colors of light, namely RGB. In each example, the dominant wavelength of the red light (R light) from the image display element 1 is 640nm, the dominant wavelength of the green light (G light) is 520nm, and the dominant wavelength of the blue light (B light) is 450nm.

[0077] Figure 8 : is a configuration diagram of an image display device according to Example 1. The image display device according to Example 1 includes an image display element 1, a projection optical system 2, and a light guide plate 3. The light guide plate 3 includes an entrance portion 31, and an exit portion 32 having 26 separation surfaces M1. The separation surface M1 includes a dielectric multilayer film. The angle θM between the separation surface M1 and the surface normal of the light guide plate 3 is 30°, the distance t between the separation surfaces M1 is 1.00 [mm], the refractive index n of the light guide plate 3 is 1.518, and the thickness d of the light guide plate 3 is 1.73 [mm]. The viewing angle range Δβ incident on the pupil SP of the observer is 38.6°, and the distance (eye distance) ER between the light guide plate 3 and the area where light of the entire viewing angle range Δβ enters is 20.0 [mm], and the size EB (eye frame) of this area is 12.0 [mm].

[0078] As Numerical Example 1, a film configuration of a dielectric multilayer film separating the surfaces M1-2 and M1-12 is illustrated. Fig.9A , Fig. 9B and Fig. 9C The angular characteristics of the reflectivity of S-polarized light of the dielectric multilayer film of the separation surfaces M1-2 and M1-12 at the dominant wavelength of RGB light in Example 1 are illustrated. Considering the position y=-4.5 [mm] of the pupil SP of the observer, the light from the separation surface M1-2 is incident at an incident angle β of 19.8°, and the light from the separation surface M1-12 is incident at an incident angle β of -8.5°. The reflectivities R1-2 (72.6°), R1-12 (54.4°), and R1-12 (72.6°) of the light having the dominant wavelength of G light at the corresponding incident angles of the separation surfaces M1-2 and M1-12 are 14.8%, 7.4%, and 74.8%, respectively. The value R1-2 (72.6°) / R1-12 (54.4°) is 2.00. By setting the angular characteristics of the reflectance to correct the relationship between the optical effective diameters of the separation surfaces in this manner, the light beams reflected on the respective separation surfaces at different departure angles become uniform, and uniform luminance can be achieved.

[0079] Fig.10 The diagram shows the angular characteristics of the reflectance of P polarized light of the dielectric multilayer film separating surfaces M1-2 and M1-12 at the dominant wavelength of G light in Example 1. The refractive index n of the high refractive index film constituting the dielectric multilayer film separating surface M1 at the dominant wavelength of G light is H , the refractive index of the low refractive index film n L , and the refractive index n of the light guide plate 3 are 2.402, 1.457, and 1.518, respectively. The Brewster condition κ is 55.1°. Since the dielectric film is configured to satisfy the Brewster condition κ, the reflectivity decreases in the incident angle range of 55° to 65°.

[0080] Fig.11 : is a configuration diagram of an image display device according to Example 2. The image display device according to Example 2 includes an image display element 1, a projection optical system 2, and a light guide plate 3. The light guide plate 3 includes an entrance portion 31, and an exit portion 32 having 11 separation surfaces M2. The separation surface M2 includes a dielectric multilayer film. The angle θM between the separation surface M2 and the surface normal of the light guide plate 3 is 25°, the distance t between the separation surfaces M2 is 1.00 [mm], the refractive index n of the light guide plate 3 is 1.518, and the thickness d of the light guide plate 3 is 2.14 [mm]. The viewing angle range Δβ incident on the pupil SP of the observer is 18.0°, the distance ER between the light guide plate 3 and the area where light of the entire viewing angle range Δβ enters is 18.0 [mm], and the size EB of this area is 5.0 [mm].

[0081] As Numerical Example 2, a film configuration of a dielectric multilayer film separating the surfaces M2-2 and M2-5 is illustrated. Fig. 12A , Fig. 12B and Fig. 12C The angular characteristics of the reflectivity of S-polarized light of the dielectric multilayer film of the separation surfaces M2-2 and M2-5 at the dominant wavelength of RGB light in Example 2 are illustrated. Considering the position y=-1.0[mm] of the pupil SP of the observer, the light from the separation surface M2-2 is incident at an incident angle β of 9.0°, and the light from the separation surface M2-5 is incident at an incident angle β of 0.0°. The reflectivities R2-2(61.0°), R2-5(55.0°) and R2-5(61.0°) of the light having the dominant wavelength of G light at the corresponding incident angles of the separation surfaces M2-2 and M2-5 are 25.5[%], 21.2[%] and 52.4[%], respectively. The value R2-2(61.0°) / R2-5(49.0°) is 1.21. By setting the angular characteristics of the reflectance to correct the relationship between the optical effective diameters of the separation surfaces in this manner, the light beams reflected on the respective separation surfaces at different departure angles become uniform, and uniform luminance can be achieved.

[0082] Fig.13 The diagram shows the angular characteristics of the reflectance of P-polarized light of the dielectric multilayer film separating surfaces M2-2 and M2-5 at the dominant wavelength of G light in Example 2. The refractive index n of the high-refractive-index film constituting the dielectric multilayer film separating surface M2 at the dominant wavelength of G light is H , the refractive index of the low refractive index film n L , and the refractive index n of the light guide plate 3 are 2.402, 1.457, and 1.518, respectively. The Brewster condition κ is 55.1°. Since the dielectric film is configured to satisfy the Brewster condition κ, the reflectivity decreases in the incident angle range of 50° to 60°.

[0083] Fig.14 The configuration of an image display device according to Example 3 is illustrated. The image display device according to Example 3 includes an image display element 1, a projection optical system 2, and a light guide plate 3. The light guide plate 3 includes an entrance portion 31, and an exit portion 32 having 14 separation surfaces M3. The separation surface M3 includes a dielectric multilayer film. The angle θM between the separation surface M3 and the surface normal of the light guide plate 3 is 60°, the distance t between the separation surfaces M3 is 2.00 [mm], the refractive index n of the light guide plate 3 is 1.516, and the thickness d of the light guide plate 3 is 1.15 [mm]. The viewing angle range Δβ incident on the pupil SP of the observer is 40.0°, the distance ER between the light guide plate 3 and the area where light of the entire viewing angle range Δβ enters is 22.0 [mm], and the size EB of the area is 12.0 [mm].

[0084] As Numerical Example 3, a film configuration of a dielectric multilayer film separating the surfaces M3-2 and M3-6 is illustrated. Fig.15A , Fig. 15B and Fig. 15C The angular characteristics of the reflectivity of S-polarized light of the dielectric multilayer film separating surfaces M3-2 and M3-6 at the dominant wavelength of RGB light in Example 3 are illustrated. Considering the position y=-3.0[mm] of the pupil SP of the observer, the light from the separation surface M3-2 is incident at an incident angle β of 20.0°, and the light from the separation surface M3-6 is incident at an incident angle β of 0.0°. The reflectivities R3-2(43.0°), R3-6(30.0°) and R3-6(43.0°) of the light having the dominant wavelength of G light at the corresponding incident angles of the separation surfaces M3-2 and M3-6 are 24.2[%], 18.6[%] and 49.7[%], respectively. The value R3-2(43.0°) / R3-10(17.0°) is 1.30. By setting the angular characteristics of the reflectance in this manner so as to correct the relationship between the optically effective diameters of the separation surfaces, the light beams reflected on the respective separation surfaces at different departure angles become uniform, and uniform luminance can be achieved.

[0085] Fig.16 The configuration of an image display device according to Example 4 is illustrated. The image display device according to Example 4 includes an image display element 1, a projection optical system 2, and a light guide plate 3. The light guide plate 3 includes an entrance portion 31, and an exit portion 32 having 9 separation surfaces M4. The separation surface M4 includes a dielectric multilayer film. The angle θM between the separation surface M4 and the surface normal of the light guide plate 3 is 65°, the distance t of the separation surface M3 is 2.00 [mm], the refractive index n of the light guide plate 3 is 1.516, and the thickness d of the light guide plate 3 is 1.00 [mm]. The viewing angle range Δβ incident on the pupil SP of the observer is 20.0°, the distance ER between the light guide plate 3 and the area where light of the entire viewing angle range Δβ enters is 22.0 [mm], and the size EB of the area is 10.0 [mm].

[0086] As Numerical Example 4, a film configuration of a dielectric multilayer film separating surfaces M4-1 and M4-4 is illustrated. Fig.17A , Fig. 17B and Fig. 17CThe angular characteristics of the reflectivity of S-polarized light of the dielectric multilayer film separating surfaces M4-1 and M4-4 at the dominant wavelength of RGB light in Example 4 are illustrated. Considering the position y=-4.0 [mm] of the pupil SP of the observer, the light from the separation surface M4-1 is incident at an incident angle β of 10.0°, and the light from the separation surface M4-4 is incident at an incident angle β of -5.0°. The reflectivities R4-1 (31.6°), R4-4 (21.7°), and R4-4 (31.6°) of the light having the dominant wavelength of G light at the corresponding incident angles of the separation surfaces M4-1 and M4-4 are 16.7%, 12.8%, and 31.5%, respectively. The value R4-1 (31.6°) / R4-4 (21.7°) is 1.30. By setting the angular characteristics of the reflectance to correct the relationship between the optical effective diameters of the separation surfaces in this manner, the light beams reflected on the respective separation surfaces at different departure angles become uniform, and uniform luminance can be achieved.

[0087] Numerical example 1 (unit: nm)

[0088]

[0089] Numerical example 2 (unit: nm)

[0090]

[0091] Numerical example 3 (unit: nm)

[0092]

[0093] Numerical Example 4 (Unit: nm)

[0094]

[0095] Although the present disclosure has described example embodiments, it is to be understood that some embodiments are not limited to the disclosed embodiments.The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

[0096] Each example can provide an image display device having high light utilization efficiency and uniform luminance over a viewing angle range incident on a pupil of an observer.

Claims

1. An image display device, comprising: an image display element configured to emit image light; as well as a light guide plate, the light guide plate comprising an entrance portion and an exit portion, the image light enters the entrance portion, the image light exits from the exit portion, The invention is characterized in that the exit portion includes a first separation surface and a second separation surface in order from the entrance portion side, each of the first separation surface and the second separation surface is configured to separate incident light into reflected light and transmitted light, The following inequalities are satisfied: R2(θ2) <Rl(θ1)<R2(o1) θ1=90-(θM-S(β1)) θ2=90-(θM-S(β2)) S(θ)=sin^(-1)(sin(θ) / n) β1β2 Wherein β1 is the incident angle [°] of light incident from the first separation surface to a predetermined position in the eye frame, β2 is the incident angle [°] of light incident from the second separation surface to the predetermined position, θM is the angle [°] between the first separation surface or the second separation surface and the surface normal of the light guide plate, n is the refractive index of the light guide plate for light with a predetermined wavelength included in the light band of the image light, R1(θ) is the reflectivity of light with the predetermined wavelength incident on the first separation surface at an incident angle θ[°], and R2(θ) is the reflectivity of light with the predetermined wavelength incident on the second separation surface at an incident angle θ[°].

2. The image display device according to claim 1, characterized in that Each of the first separation surface and the second separation surface includes a dielectric multilayer film.

3. The image display device according to claim 2, characterized in that The dielectric multilayer film reflects S-polarized light and transmits P-polarized light, and the following inequality is satisfied: 0<θMM<45.

4. The image display device according to claim 3, characterized in that the following The inequality is satisfied: 1.0 <R1(θ1) / R2(θ2)<5.0。 5. The image display device according to claim 3, characterized in that The following inequalities are satisfied: 85-θM≤K≤95-θM Where n H is the refractive index of the high refractive index film constituting the dielectric multilayer film with respect to light having the predetermined wavelength, and n L is the refractive index of the low-refractive-index film constituting the dielectric multilayer film with respect to light having the predetermined wavelength.

6. The image display device according to claim 2, characterized in that The dielectric multilayer film reflects P-polarized light and transmits S-polarized light, and the following inequality is satisfied: 455<θMM<90.

7. The image display device according to claim 6, characterized in that The following inequalities are satisfied: 1.0 <R1(θ1) / R2(θ2)<4.0。

Images