Image display device

Abstract

To provide an image display device which is uniform in brightness in a visual field angle range for incidence into pupils of an observer with high light utilization efficiency.SOLUTION: The image display device has: an image display element emitting image light; and a light guide plate including an incident part into which the image light is made incident and an emission part which emits the image light. The emission part includes a first separation surface and a second separation surface. An incidence angle [°] of light incident on a prescribed location in an eye-box from the first separation surface, an incidence angle [°] of light incident on the prescribed location from the second separation surface, an angle [°] formed between the first or second separation surface and a surface normal line of the light guide plate, a refractive index of the light guide plate to light of a prescribed wavelength included in a bandwidth of the image light, a reflection rate to light of the prescribed wavelength incident into the first separation surface at an incidence angle θ[°], and a reflection rate of light of the prescribed wavelength incident into the second separation surface at the incidence angle θ[°] are each appropriately set.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an image display device including a light guide plate that guides a displayed image to a viewer's pupil. [Background technology]

[0002] Conventionally, there is known an image display device equipped with a light guide plate that guides a display image to the pupil of an observer. Fig. 18 is a conceptual diagram of light beams propagating inside the 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 120, enter an entrance portion 131 at different angles of incidence, and are deflected, and then propagate inside the light guide plate 130 at different total reflection angles α10, α20, and α30 (α10<α20<α30). A portion of the light beams that enter the exit portion 132 are deflected and head toward the pupil SP of the observer, and the other light beams propagate inside the light guide plate 130 by total reflection and enter the exit portion 132. In conventional image display devices, the width of the area (effective area) where the lights L10, L20, and L30 overlap at the position of the observer's pupil SP is smaller than the width of the light beam emitted from the emission section 132, and a large amount of unnecessary light is generated relative to the effective area, significantly reducing the light utilization efficiency.

[0003] Patent Document 1 discloses a configuration in which an appropriate incident angle range with high reflectance and low incidence angle dependency is set for multiple separation surfaces tilted at the same angle in order to increase the intensity of each light ray incident on the observer's pupil. Patent Document 2 discloses a configuration in which different light reflectances are set for multiple semi-transmitting layers based on angle dependency in order to increase light guide efficiency, so that only the light of the angle component incident on the observer's pupil is reflected and the light of the other angle components is transmitted. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-165743 A [Patent Document 2] International Publication No. 2018 / 221026 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the configurations of Patent Documents 1 and 2, the reflectance is constant within the range of angles of incidence of the separation surface in the optical path along which the light from the image display element is deflected to the observer's pupil. As a result, the light beams reflected by the separation surface at different exit angles are not uniform, resulting in non-uniform luminance within the range of viewing angles incident on the observer's pupil.

[0006] An object of the present invention is to provide an image display device which has high light utilization efficiency and has uniform luminance over the range of viewing angles at which light enters the observer's pupil. [Means for solving the problem]

[0007] An image display device as one aspect of the present invention includes an image display element that emits image light, and a light guide plate that has an entrance section into which the image light is incident and an exit section that emits the image light, the exit section having a first separation surface and a second separation surface, where the angle of incidence [°] of light incident from the first separation surface to a predetermined position in the eye box is β1, the angle of incidence [°] of light incident from the second separation surface to the predetermined position is β2, the angle [°] between the first or second separation surface and a surface normal to the light guide plate is θM, the refractive index of the light guide plate for light of a predetermined wavelength included in the band of image light is n, the reflectance of the light of the predetermined wavelength incident on the first separation surface at an incident angle θ [°] is R1(θ), and the reflectance of the light of the predetermined wavelength incident on the second separation surface at an incident angle θ [°] is R2(θ), R2(θ2) <R1(θ1)<R2(θ1) θ1=90-(θM-S(β1)) θ2=90-(θM-S(β2)) S(θ)=sin^(-1)(sin(θ) / n) β1>β2 The present invention is characterized in that the following conditional expression is satisfied: Effect of the Invention

[0008] According to the present invention, it is possible to provide an image display device which has high light utilization efficiency and has uniform luminance over the range of viewing angles at which light enters the observer's pupil. [Brief description of the drawings]

[0009] [Figure 1] 5 is a conceptual diagram showing the angle of incidence of light on a separation surface and an effective diameter in the image display device according to the embodiment of the present invention. [Diagram 2] 3 is a conceptual diagram of a light flux propagating inside the light guide plate of the present embodiment. FIG. [Diagram 3] 4 is a conceptual diagram of the position of a separation surface and the angle of incidence of light as viewed from a predetermined position of the observer's pupil in this embodiment. [Figure 4] FIG. 2 is a schematic diagram of multiple separation planes of the present embodiment. [Diagram 5] FIG. 2 is a diagram illustrating a configuration example of an incident portion. [Figure 6] FIG. 2 is a diagram illustrating a configuration example of an incident portion. [Figure 7] FIG. 2 is a diagram illustrating a configuration example of an incident portion. [Figure 8] FIG. 1 is a configuration diagram of an image display device according to a first embodiment. [Figure 9] 4 is a diagram showing the angular characteristics of the reflectance of S-polarized light of the dielectric multilayer film of Example 1. FIG. [Figure 10] 4 is a diagram showing the angular characteristics of the reflectance of P-polarized light of the dielectric multilayer film of Example 1. FIG. [Figure 11] FIG. 11 is a configuration diagram of an image display device according to a second embodiment. [Figure 12] 13 is a diagram showing the angular characteristics of the reflectance of S-polarized light of the dielectric multilayer film of Example 2. FIG. [Figure 13] FIG. 13 is a diagram showing the angular characteristics of the reflectance of P-polarized light of the dielectric multilayer film of Example 2. [Figure 14] FIG. 11 is a configuration diagram of an image display device according to a third embodiment. [Figure 15] FIG. 13 is a diagram showing the angular characteristics of the reflectance of S-polarized light of the dielectric multilayer film of Example 3. [Figure 16] FIG. 11 is a configuration diagram of an image display device according to a fourth embodiment. [Figure 17]FIG. 13 is a diagram showing the angular characteristics of the reflectance of S-polarized light of the dielectric multilayer film of Example 4. [Figure 18] FIG. 13 is a conceptual diagram of a light flux propagating inside a light guide plate of a conventional image display device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals are used to refer to the same components, and duplicated descriptions will be omitted.

[0011] FIG. 1 is a conceptual diagram of the angle of incidence and effective diameter of light on a separation surface in an image display device according to an embodiment of the present invention. The image display device includes an image display element (image generating element) 1 that emits image light (image display light), a projection optical system 2, and a light guide plate 3 that includes an entrance section 31 where the image light is incident and an exit section 32 where the image light is exited. Note that, for example, a combination of a liquid crystal panel and an illumination optical system may be used as the image display element 1. Also, a self-luminous display in which a light source (OLED or LED) is arranged for each pixel, or a combination of a MEMS (Micro Electro Mechanical Systems) and a laser light source may be used as the image display element 1. The projection optical system 2 includes optical elements such as a lens, a diffractive optical element, a holographic element, or a metasurface.

[0012] Light beams L1, L2, and L3 emitted from pixels of the image display element 1 enter the projection optical system 2, enter the entrance section 31 at different angles, are deflected, and then propagate inside the light guide plate 3 at different total reflection angles α1, α2, and α3 (α1<α2<α3). A portion of the light beam that enters the exit section 32 is deflected and heads toward the observer's pupil SP, while the other light beam propagates inside the light guide plate 3 by total reflection and enters the exit section 32.

[0013] In this embodiment, the exit unit 32 includes a plurality of separation surfaces. In this embodiment, high light utilization efficiency can be achieved by appropriately setting the angular characteristics of the reflectance of the plurality of separation surfaces so as to reflect the light of the angle component incident on the observer's pupil SP and transmit the light of the other angle components.

[0014] The wavelength range and polarization components of the image light emitted from the image display element 1 may be appropriately set according to the configurations of the entrance section 31, the extension section, and the emission section 32. For example, the image display element may be configured to emit monochromatic light using only a green laser light source.

[0015] The angular characteristics of the reflectance of the multiple separation surfaces will be described below. FIG. 2 is a conceptual diagram of a light beam propagating inside the light guide plate 3 of this embodiment. The separation surfaces M1, M2, and M3 are provided in this order from the -y side (the side closer to the incident part 31) to the +y side (the side farther from the incident part 31). In order to extract the light incident on the observer's pupil SP, the corresponding separation surfaces need to reflect the light with different total reflection angles. The light with the corresponding total reflection angles of the separation surfaces M1, M2, and M3 are respectively called light L1, L2, and L3. The angles of incidence θ1, θ2, and θ3 of the angle components of the light incident on the observer's pupil SP on the separation surfaces M1, M2, and M3 have the following magnitude relationship.

[0016] θ1>θ2>θ3 Therefore, on the separation surface on the -y side, the reflectance corresponding to a large incident angle in the incident angle range in the optical path deflected to the observer's pupil SP is increased, and the reflectance corresponding to a small incident angle is decreased. Also, on the separation surface on the +y side, the reflectance corresponding to a small incident angle in the incident angle range in the optical path deflected to the observer's pupil SP is increased. This makes it possible to realize high light utilization efficiency.

[0017] The magnitude relationship between the reflectances of the separation surfaces and between the reflectances of the separation surfaces will be described below. In Fig. 2, the optical effective diameters A1, A2, and A3 of the separation surfaces M1, M2, and M3 have the following magnitude relationship.

[0018] A1 <A2<A3 By setting the angle characteristic of the reflectance so as to correct the relationship between the effective optical diameters of the separation surfaces, the light beams emitted from each separation surface at different exit angles become uniform. In other words, the reflectance for the corresponding light is set high for a separation surface with a small effective optical diameter, and the reflectance for the corresponding light is set low for a separation surface with a large effective optical diameter. The reflectances R1(θ), R2(θ), and R3(θ) for the incident light (light of a predetermined wavelength included in the band of the image light of the light guide plate 3) incident at an incident angle θ on each of the separation surfaces M1, M2, and M3 have the following relationship (1).

[0019] R1(θ1)>R2(θ2)>R3(θ3) (1) In addition, the reflectance of the separation surface on the -y side (the side closer to the entrance unit 31) for light at a predetermined incident angle in the incident angle range in the optical path deflected to the observer's pupil SP is made low, and the reflectance of the separation surface on the +y side (the side farther from the entrance unit 31) is made high. This makes the light beams reflected at the multiple separation surfaces with the same exit angle uniform. Since the light beam is reflected at the separation surface on the -y side, in order to obtain a similar light beam at the separation surface on the +y side, it is necessary to relatively increase the reflectance. Therefore, the reflectances R1(θ1), R2(θ1), and R3(θ1) of the incident light incident at the incident angle θ1 on each of the separation surfaces M1, M2, and M3 have the following relationship (2).

[0020] R1(θ1) <R2(θ1)<R3(θ1) (2) From the relationships (1) and (2), the reflectances of the separation surfaces M1 and M2 have the following relationship (3).

[0021] R2(θ2) <R1(θ1)<R2(θ1) (3) By making the multiple separation surfaces satisfy the relationship (3), it is possible to realize an image display device that has high light utilization efficiency and has uniform luminance over the range of viewing angles at which light enters the observer's pupil SP.

[0022] 3 is a conceptual diagram of the positions of separation surfaces M1, M2 and the angles of incidence of light as viewed from a predetermined position of the observer's pupil SP in this embodiment. The angles of incidence θ1 [°], θ2 [°] of light incident on separation surfaces M1, M2 at a predetermined position of the observer's pupil SP are expressed by the following formula:

[0023] θ1=90-(θM-S(β1)) θ2=90-(θM-S(β2)) S(θ)=sin^(-1)(sin(θ) / n) Here, β1 is the angle of incidence [°] of light incident from separation surface M1 to a predetermined position of the observer's pupil SP. β2 is the angle of incidence [°] of light incident from separation surface M2 to a predetermined position of the observer's pupil SP. Note that the angle of incidence β1 is greater than the angle of incidence β2. θM is the angle [°] between each separation surface and the surface normal of the light guide plate 3. n is the refractive index for light of a predetermined wavelength included in the band of image light of the light guide plate 3. S(θ) represents refraction according to Snell's law.

[0024] FIG. 4 is a schematic diagram of a plurality of separation surfaces in this embodiment. FIG. 4(A) shows a case where the angle θM between each separation surface and the surface normal of the light guide plate 3 is greater than 0° and smaller than 45°. In this case, each separation surface transmits light in a relatively vertical incidence angle range, and reflects light in a relatively oblique incidence angle range, so that the light can be deflected to the observer's pupil SP. The incidence angle characteristic of the reflectance at this time is obtained by using a dielectric multilayer film for each separation surface. Specifically, each separation surface is configured using a dielectric multilayer film that transmits P-polarized light and has the above-mentioned incidence angle characteristic for S-polarized light. In the relatively oblique incidence angle range of S-polarized light, each separation surface satisfies the relationship (3), thereby realizing uniform brightness in the viewing angle range in which the light is incident on the observer's pupil SP with high utilization efficiency.

[0025] In the case of FIG. 4(A), it is preferable to satisfy the following conditional expression (4).

[0026] 1.0 <R1(θ1) / R2(θ2)<5.0 (4) Condition (4) specifies the reflectance for correcting the relationship between the effective optical diameters of the respective separation surfaces. If the upper limit is exceeded, the reflectance is over-corrected with respect to the relationship between the effective optical diameters of the respective separation surfaces, and the light beams with different exit angles extracted from each separation surface will not be uniform, which is not preferable.

[0027] It is more preferable that the numerical range of conditional expression (4) be the numerical range of the following conditional expression (4a).

[0028] 1.0 <R1(θ1) / R2(θ2)<4.0 (4a) It is even more preferable that the numerical range of conditional expression (4) be the numerical range of the following conditional expression (4b).

[0029] 1.0 <R1(θ1) / R2(θ2)<3.0 (4b) In this embodiment, it is preferable to satisfy the following conditional expression (5).

[0030] 90-θM-5≦κ≦90-θM+5 (5) Condition (5) may be expressed as condition (5a).

[0031] 85-θM≦κ≦95-θM (5a) Here, κ is the Brewster condition for the dielectric multilayer film on each separation surface, and is expressed by the following formula.

[0032]

number

[0033] where n H is the refractive index of the high refractive index film constituting the dielectric multilayer film for light of a predetermined wavelength included in the band of image light. L is the refractive index of the low refractive index film constituting the dielectric multilayer film for light of a predetermined wavelength included in the band of the image light. The light of the predetermined wavelength included in the band of the image light is, for example, light of the dominant wavelength. The dominant wavelength is, for example, the peak wavelength of the band of the image light.

[0034] The angle ranges of the left and right sides of condition (5) are the incidence angle ranges of relatively oblique incidence. By satisfying condition (5), a configuration that transmits P-polarized light can be realized.

[0035] FIG. 4(B) shows a case where the angle θM between each separation surface and the surface normal of the light guide plate 3 is greater than 45° and smaller than 90°. In this case, each separation surface reflects light in a relatively normal incidence angle range and transmits light in a relatively oblique incidence angle range, thereby deflecting the light to the observer's pupil SP. The incidence angle characteristic of the reflectance at this time is obtained by using a dielectric multilayer film for each separation surface. Specifically, each separation surface is configured using a dielectric multilayer film that transmits S-polarized light and has the above-mentioned incidence angle characteristic for P-polarized light. In the relatively oblique incidence angle range of P-polarized light, each separation surface satisfies the relationship (5), thereby realizing uniform brightness in the viewing angle range where the light is incident on the observer's pupil SP with high utilization efficiency.

[0036] In the case of FIG. 4B, it is preferable to satisfy the following conditional expression (6).

[0037] 1.0 <R1(θ1) / R2(θ2)<4.0 (6) Condition (6) specifies the reflectance for correcting the relationship between the effective optical diameters of the respective separation surfaces. If the upper limit of the condition is exceeded, the reflectance is over-corrected with respect to the relationship between the effective optical diameters of the respective separation surfaces, and the light beams with different exit angles extracted from each separation surface will not be uniform, which is not preferable.

[0038] It is more preferable that the numerical range of conditional expression (6) be the numerical range of the following conditional expression (6a).

[0039] 1.0 <R1(θ1) / R2(θ2)<3.0 (6a) It is even more preferable that the numerical range of conditional expression (4) be the numerical range of the following conditional expression (4b).

[0040] 1.0 <R1(θ1) / R2(θ2)<2.0 (6b) A configuration example of the incident part 31 will be described below. FIGS. 5 to 7 are diagrams showing configuration examples of the incident part 31. As the incident part 31, a prism element 61 may be used as shown in FIGS. 5(A) and 5(B), or a reflecting surface 62 may be used as shown in FIG. 5(C). Also, as shown in FIG. 6(A), a diffractive optical element 71 may be used. Note that the efficiency and diffraction angle for each diffraction order can be controlled by changing the shape, height, and refractive index of the lattice structure of the diffractive optical element 71 as shown in FIGS. 6(B) to 6(E), and may be determined according to the requirements of the image display device. Also, a holographic element may be used as the incident part 31. Furthermore, as shown in FIGS. 7(A) and 7(B), the incident part 31 may be configured to make the light beam from the projection optical system 2 enter the light guide plate 3 at an angle with respect to the normal to the incident surface of the light guide plate 3, and guide the light into the light guide plate 3 by the reflecting surface 81.

[0041] The specific configuration of each embodiment will be described below. In each embodiment, an image display device that emits three colors of light, RGB, will be described. In each embodiment, the dominant wavelength of red light (R light) from the image display element 1 is 640 nm, the dominant wavelength of green light (G light) is 520 nm, and the dominant wavelength of blue light (B light) is 450 nm.

[0042] FIG. 8 is a configuration diagram of an image display device according to a first embodiment. The image display device according to the first embodiment 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 section 31 and an exit section 32 having 26 separation surfaces M1. The separation surfaces M1 are made of a dielectric multilayer film. The angle θM between the separation surfaces M1 and the surface normal of the light guide plate 3 is 30°, the interval 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 observer's pupil SP is 38.6°, the distance (eye relief) ER between the light guide plate 3 and the area where the light of all the viewing angle ranges Δβ is incident is 20.0 [mm], and the size EB (eye box) of the area is 12.0 [mm].

[0043] The film configuration of the dielectric multilayer film of the separation surface M1-2 and the separation surface M1-12 is shown as Numerical Example 1. Fig. 9 is a diagram showing the angle characteristics of the reflectance of S-polarized light of the dielectric multilayer film of the separation surface M1-2 and the separation surface M1-12 at the main wavelength of RGB light in Example 1. Focusing on the position of y = -4.5 [mm] of the observer's pupil SP, 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 reflectances R1-2 (72.6 °), R1-12 (54.4 °), and R1-12 (72.6 °) for the light of the main wavelength of G at the corresponding incident angles of the separation surface M1-2 and the separation surface M1-12 are 14.8 [%], 7.4 [%], and 74.8 [%], respectively. Moreover, the value R1-2 (72.6°) / R1-12 (54.4°) is 2.00. By setting the angle characteristic of the reflectance in this way so as to correct the relationship between the effective optical diameters of the separation surfaces, the light beams with different exit angles reflected by each separation surface become uniform, thereby achieving uniform brightness.

[0044] 10 is a diagram showing the angle characteristics of the reflectance of P-polarized light of the dielectric multilayer films of the separation surfaces M1-2 and M1-12 at the dominant wavelength of G light in Example 1. The refractive index n 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. Also, the Brewster condition κ is 55.1°. Since the dielectric film is configured to satisfy the Brewster condition κ, the reflectance is reduced in the incident angle range from 55° to 65°.

[0045] FIG. 11 is a configuration diagram of an image display device of Example 2. The image display device of 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 section 31 and an exit section 32 having eleven separation surfaces M2. The separation surfaces M2 are made of a dielectric multilayer film. The angle θM between the separation surfaces M2 and the surface normal of the light guide plate 3 is 25°, the interval t of 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 observer's pupil SP is 18.0°, the distance ER between the light guide plate 3 and the area where the light of all the viewing angle ranges Δβ is incident is 18.0 [mm], and the size EB of the area is 5.0 [mm].

[0046] The film configuration of the dielectric multilayer film of the separation surface M2-2 and the separation surface M2-5 is shown as Numerical Example 2. Fig. 12 is a diagram showing the angle characteristics of the reflectance of S-polarized light of the dielectric multilayer film of the separation surface M2-2 and the separation surface M2-5 at the main wavelength of RGB light in Example 2. Focusing on the position of y = -1.0 [mm] of the observer's pupil SP, 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 reflectances R2-2 (61.0 °), R2-5 (55.0 °), and R2-5 (61.0 °) for the light of the main wavelength of G at the corresponding incident angles of the separation surface M2-2 and the separation surface M2-5 are 25.5 [%], 21.2 [%], and 52.4 [%], respectively. Moreover, the value R2-2 (61.0°) / R2-5 (49.0°) is 1.21. By setting the angle characteristic of the reflectance in this way so as to correct the relationship between the effective optical diameters of the separation surfaces, the light beams reflected by each separation surface at different exit angles become uniform, thereby achieving uniform brightness.

[0047] 13 is a diagram showing the angular characteristics of the reflectance of P-polarized light of the dielectric multilayer films of the separation surfaces M2-2 and M2-5 at the dominant wavelength of G light in Example 2. The refractive index n 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. Also, the Brewster condition κ is 55.1°. Since the dielectric film is configured to satisfy the Brewster condition κ, the reflectance is reduced in the incident angle range from 50° to 60°.

[0048] FIG. 14 is a configuration diagram of an image display device of Example 3. The image display device of 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 section 31 and an exit section 32 having 14 separation surfaces M3. The separation surfaces M3 are made of a dielectric multilayer film. The angle θM between the separation surfaces M3 and the surface normal of the light guide plate 3 is 60°, the interval t of 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 observer's pupil SP is 40.0°, the distance ER between the light guide plate 3 and the area where the light of all the viewing angle ranges Δβ is incident is 22.0 [mm], and the size EB of the area is 12.0 [mm].

[0049] The film configuration of the dielectric multilayer film of the separation surface M3-2 and the separation surface M3-6 is shown as Numerical Example 3. Fig. 15 is a diagram showing the angle characteristics of the reflectance of S-polarized light of the dielectric multilayer film of the separation surface M3-2 and the separation surface M3-6 at the main wavelength of RGB light in Example 3. Focusing on the position of y = -3.0 [mm] of the observer's pupil SP, 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 reflectances R3-2 (43.0 °), R3-6 (30.0 °), and R3-6 (43.0 °) for the light of the main wavelength of G at the corresponding incident angles of the separation surface M2-2 and the separation surface M2-5 are 24.2 [%], 18.6 [%], and 49.7 [%], respectively. Moreover, the value R3-2 (43.0°) / R3-10 (17.0°) is 1.30. By setting the angle characteristic of the reflectance in this way so as to correct the relationship between the effective optical diameters of the separation surfaces, the light beams reflected by each separation surface at different exit angles become uniform, thereby achieving uniform brightness.

[0050] FIG. 16 is a configuration diagram of an image display device of Example 4. The image display device of 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 nine separation surfaces M4. The separation surfaces M4 are formed of a dielectric multilayer film. The angle θM between the separation surfaces M4 and the surface normal of the light guide plate 3 is 65°, the interval t of 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 1.00 [mm]. The viewing angle range Δβ incident on the observer's pupil SP is 20.0°, the distance ER between the light guide plate 3 and the area where the light of all the viewing angle ranges Δβ is incident is 22.0 [mm], and the size EB of the area is 10.0 [mm].

[0051] The film configuration of the dielectric multilayer film of the separation surface M4-1 and the separation surface M4-4 is shown as Numerical Example 4. FIG. 17 is a diagram showing the angle characteristics of the reflectance of S-polarized light of the dielectric multilayer film of the separation surface M4-1 and the separation surface M4-4 at the main wavelength of RGB light in Example 4. Focusing on the position of y=-4.0 [mm] of the observer's pupil SP, 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 reflectances R4-1 (31.6°), R4-4 (21.7°), and R4-4 (31.6°) for the light of the main wavelength of G at the corresponding incident angles of the separation surface M4-1 and the separation surface M4-4 are 16.7 [%], 12.8 [%], and 31.5 [%], respectively. Moreover, the value R4-1 (31.6°) / R4-4 (21.7°) is 1.30. By setting the angle characteristic of the reflectance in this way so as to correct the relationship between the effective optical diameters of the separation surfaces, the light beams with different exit angles reflected by each separation surface become uniform, thereby achieving uniform brightness.

[0052] Numerical Example 1 (unit: nm) JPEG2025063473000003.jpg19957

[0053] Numerical Example 2 (unit: nm) JPEG2025063473000004.jpg19561

[0054] Numerical Example 3 (unit: nm) JPEG2025063473000005.jpg19259

[0055] Numerical Example 4 (unit: nm) JPEG2025063473000006.jpg19259

[0056] The disclosure of this embodiment includes the following configuration. (Configuration 1) an image display element that emits image light; a light guide plate including an entrance portion into which the image light is incident and an exit portion from which the image light is exited; the emission section includes a first separation surface and a second separation surface; Let β1 be the angle of incidence [°] of light incident from the first separation surface to a predetermined position in the eye box, β2 be the angle of incidence [°] of light incident from the second separation surface to the predetermined position, θM be the angle [°] between the first or second separation surface and the surface normal of the light guide plate, n be the refractive index of the light guide plate for light of a predetermined wavelength included in the band of the image light, R1(θ) be the reflectance for the light of the predetermined wavelength incident on the first separation surface at an incident angle θ [°], and R2(θ) be the reflectance for the light of the predetermined wavelength incident on the second separation surface at an incident angle θ [°], R2(θ2) <R1(θ1)<R2(θ1) θ1=90-(θM-S(β1)) θ2=90-(θM-S(β2)) S(θ)=sin^(-1)(sin(θ) / n) β1>β2 1. An image display device, characterized in that the following conditional expression is satisfied: (Configuration 2) 2. The image display device according to configuration 1, wherein the first and second separation surfaces include a dielectric multilayer film. (Configuration 3) The dielectric multilayer film reflects S-polarized light and transmits P-polarized light, 0<θM<45 3. The image display device according to configuration 2, wherein the following condition is satisfied: (Configuration 4) 1.0 <R1(θ1) / R2(θ2)<5.0 4. The image display device according to configuration 3, wherein the following condition is satisfied: (Configuration 5) The refractive index of the high refractive index film constituting the dielectric multilayer film with respect to the light of the predetermined wavelength is n H The refractive index of the low refractive index film constituting the dielectric multilayer film with respect to the light of the predetermined wavelength is n L When 85-θM≦κ≦95-θM (Number 1) JPEG2025063473000007.jpg31111

[0057] 5. The image display device according to configuration 3 or 4, which satisfies the following conditional expression: (Configuration 6) The dielectric multilayer film reflects P-polarized light and transmits S-polarized light, 45<θM<90 3. The image display device according to configuration 2, wherein the following condition is satisfied: (Configuration 7) 1.0 <R1(θ1) / R2(θ2)<4.0 7. The image display device according to configuration 6, wherein the following condition is satisfied:

[0058] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of the gist of the present invention. [Explanation of symbols]

[0059] 1 Image display element 3 Light guide plate 31 Input part 32 Injection part EB Eye Box M1,M2 separation plane

Claims

1. an image display element that emits image light; a light guide plate including an entrance portion into which the image light is incident and an exit portion from which the image light is exited; the emission section includes a first separation surface and a second separation surface; Let β1 be the angle of incidence [°] of light incident from the first separation surface to a predetermined position in the eye box, β2 be the angle of incidence [°] of light incident from the second separation surface to the predetermined position, θM be the angle [°] between the first or second separation surface and the surface normal of the light guide plate, n be the refractive index of the light guide plate for light of a predetermined wavelength included in the band of the image light, R1(θ) be the reflectance for the light of the predetermined wavelength incident on the first separation surface at an incident angle θ [°], and R2(θ) be the reflectance for the light of the predetermined wavelength incident on the second separation surface at an incident angle θ [°], R2(θ2)<R1(θ1)<R2(θ1) θ1=90-(θM-S(β1)) θ2=90-(θM-S(β2)) S(θ)=sin^(-1)(sin(θ) / n) β１＞β２ 1. An image display device, characterized in that the following conditional expression is satisfied:

2. 2. The image display device according to claim 1, wherein the first and second separation surfaces include a dielectric multilayer film.

3. The dielectric multilayer film reflects S-polarized light and transmits P-polarized light, 0<θM<45 3. The image display device according to claim 2, wherein the following condition is satisfied:

4. 1.0<R1(θ1) / R2(θ2)<5.0 4. The image display device according to claim 3, wherein the following condition is satisfied:

5. The refractive index of the high refractive index film constituting the dielectric multilayer film with respect to the light of the predetermined wavelength is n Ｈ The refractive index of the low refractive index film constituting the dielectric multilayer film with respect to the light of the predetermined wavelength is n Ｌ When 85-θM≦κ≦95-θM [0010] 5. The image display device according to claim 3, wherein the following condition is satisfied:

6. The dielectric multilayer film reflects P-polarized light and transmits S-polarized light, 45<θM<90 3. The image display device according to claim 2, wherein the following condition is satisfied:

7. 1.0<R1(θ1) / R2(θ2)<4.0 7. The image display device according to claim 6, wherein the following condition is satisfied:

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