JP2022183889A - Combiner, head-up display and moving object - Google Patents

Abstract

To provide a combiner characterized by making noise images less conspicuous.SOLUTION: This combiner includes a first and a second surface and is used for head-up display. The combiner includes a first substrate that forms the first surface, a second substrate that forms the second surface, a joint layer that joins the first and second substrates together, and a hologram element located between the first and second substrates. The noise diffraction rate (%) of noise image luminance in the combiner that is caused by light emitted from a testing light source and entering the combiner from the second surface and then emitted from the first surface after being reflected at the first surface and diffracted by the hologram element, to luminance in the light source that is caused by light emitted from the testing light source, can be made to be 0.11% or less.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to combiners, head-up displays, and moving bodies.

A head-up display provides a display within the user's field of view. The head-up display has a transparent combiner. The combiner is projected with image light. In the head-up display disclosed in Patent Document 1, the combiner includes a hologram element. The hologram element diffracts the image light and directs it to the user. A user can observe the images in the combiner. Also, the user can secure a field of view through the transparent combiner.

JP-A-2000-35513

When the combiner disclosed in Patent Document 1 is used, noise images such as the sun and outdoor lights can be observed brightly inside the combiner. A noise image is observed at a position different from the actual position. SUMMARY OF THE INVENTION The present invention has been made in consideration of such points, and an object of the present invention is to make the noise image inconspicuous.

A first combiner according to an embodiment of the present disclosure comprises:
A combiner for a head-up display including a first side and a second side,
a first substrate forming the first surface;
a second substrate forming the second surface;
a bonding layer that bonds the first substrate and the second substrate;
a hologram element positioned between the first substrate and the second substrate;
Luminance (Watt/steradian ) to the luminance (watts/steradian) at the light source due to the light emitted from the light source is 0.11% or less.

In the first combiner according to one embodiment of the present disclosure, the first substrate may include an antireflection layer forming the first surface.

In the first combiner according to one embodiment of the present disclosure, the reflectance at the first surface may be 1% or less.

In the first combiner according to one embodiment of the present disclosure, the diffraction efficiency of the hologram element may be 60% or less.

In the first combiner according to an embodiment of the present disclosure, the diffraction efficiency H (%) of the hologram element, the full width at half maximum W (nm) in the wavelength distribution of the diffraction efficiency of the hologram element, and the reflection at the antireflection layer The rate R (%) is
(H/100)×W×(R/100)×(1−(R/100))≦0.098
may be

A second combiner according to an embodiment of the present disclosure comprises:
A combiner for a head-up display including a first side and a second side,
a first substrate forming the first surface;
a second substrate forming the second surface;
a bonding layer that bonds the first substrate and the second substrate;
a hologram element positioned between the first substrate and the second substrate;
The first substrate includes an antireflection layer forming the first surface,
The reflectance of the first surface is 1% or less.

A third combiner according to an embodiment of the present disclosure comprises:
a first substrate and a second substrate;
a bonding layer that bonds the first substrate and the second substrate;
a hologram element positioned between the first substrate and the second substrate;
The diffraction efficiency of the hologram element is 60% or less.

A fourth combiner according to an embodiment of the present disclosure comprises:
A combiner for a head-up display including a first side and a second side,
a first substrate forming the first surface;
a second substrate forming the second surface;
a bonding layer that bonds the first substrate and the second substrate;
a hologram element located between the first substrate and the second substrate;
The first substrate includes an antireflection layer forming the first surface,
The diffraction efficiency H (%) of the hologram element, the full width at half maximum W (nm) in the wavelength distribution of the diffraction efficiency of the hologram element, and the reflectance R (%) of the antireflection layer are
(H/100)×W×(R/100)×(1−(R/100))≦0.098
becomes.

A head-up display according to an embodiment of the present disclosure includes
an image forming device that emits image light;
and any one of the first to fourth combiners according to an embodiment of the present disclosure irradiated with the image light.

A moving object according to an embodiment of the present disclosure includes any head-up display according to an embodiment of the present disclosure.

According to the present invention, noise images can be made inconspicuous.

FIG. 1 is a diagram for explaining an embodiment, and is a side view showing a specific example of a moving body and a head-up display. 2 is a side sectional view showing the combiner of the head-up display shown in FIG. 1; FIG. 3A is a cross-sectional view showing an example of a first substrate that may be included in the combiner shown in FIG. 2. FIG. 3B is a cross-sectional view showing another example of a first substrate that can be included in the combiner shown in FIG. 2. FIG. 3C is a cross-sectional view showing yet another example of a first substrate that can be included in the combiner shown in FIG. 2. FIG. FIG. 4 is a diagram illustrating a method of manufacturing a hologram recording layer included in the combiner shown in FIG. 5 is a graph showing an example of spectral transmittance of a hologram element included in the combiner shown in FIG. 2. FIG. FIG. 6 is a diagram showing a method of measuring the spectral transmittance of the hologram element shown in FIG. FIG. 7 is a diagram illustrating the operation of the combiner shown in FIG. 2; FIG. 8 is a diagram showing a method of measuring the noise diffraction index of the combiner shown in FIG. 9 is a graph showing the spectral intensity of the light source used in the measurement method of FIG. 9. FIG. FIG. 10 is a cross-sectional view showing the configuration of samples 1 to 10. FIG.

An embodiment of the present disclosure will be described below with reference to the drawings. In the drawings attached to this specification, for the convenience of illustration and ease of understanding, the scale and the ratio of vertical and horizontal dimensions are changed and exaggerated from those of the real thing. In addition, configurations and the like shown in some drawings may be omitted in other drawings.

In this specification, terms that specify shapes and geometric conditions and their degrees, such as "parallel", "perpendicular", "identical", length and angle values, etc., are limited to strict meanings. It is interpreted to include the extent to which similar functions can be expected without being

In this specification, terms such as "sheet", "film" and "plate" are not distinguished from each other based solely on a difference in designation. For example, a "transparent plate" cannot be distinguished from a member called a transparent film or a transparent sheet only by the difference in name.

In this specification, the normal direction of a sheet-like (sheet-like, plate-like) member refers to the normal direction to the sheet surface of the target sheet-like (film-like, plate-like) member. In addition, the "sheet surface (film surface, plate surface)" refers to the sheet-like member (film-like) that is the target when the target sheet-like (film-like, plate-like) member is viewed as a whole and from a broad perspective. member, plate-shaped member).

In order to clarify the directional relationships among the figures, some of the figures show the first direction D1, the second direction D2, the third direction D3 and the normal direction ND as common directions by means of commonly labeled arrows. is shown as In the following examples, the first direction D1 and the second direction D2 are parallel to the horizontal direction, and the third direction D3 is parallel to the vertical direction. The tip side of the arrow is one side in each direction. An arrow pointing forward from the plane of the drawing along a direction perpendicular to the plane of the drawing is indicated by a dot in a circle, as shown in FIG. 2, for example.

1 to 9 are diagrams for explaining an embodiment. As shown in FIGS. 1 and 2, the head-up display 20 has an image forming device 30 and a combiner 40 . Combiner 40 is transparent. The head-up display 20 uses the combiner 40 to display the image formed by the image forming device 30 to the user 5 . A user 5 of the head-up display 20 can observe behind the combiner 40 through the combiner 40 . An imaging device may image the user 5 observing the combiner 40 via the combiner 40 . This embodiment is designed to make the noise image 88, which has been a problem in the conventional head-up display, inconspicuous. An embodiment will now be described with reference to specific examples shown in the drawings.

As used herein, "transparent" means that the visible light transmittance is 50% or more, preferably 80% or more. The visible light transmittance is measured using a spectrophotometer ("UV-3100PC" manufactured by Shimadzu Corporation, compliant with JISK0115) within a range of measurement wavelengths from 380 nm to 780 nm at intervals of 1 nm, at each wavelength. It is specified as the average value of total light transmittance.

The head-up display 20 according to this embodiment can be applied to various fields. Head-up display 20 may be applied to a head-mounted display. A heads-up display 20 may be applied to the prompter. The prompter may be used for lectures, imaging, and the like.

In the illustrated example, the head-up display 20 is applied to the moving body 10. FIG. The moving body 10 is a movable device. The mobile object 10 may be movable with a person on it. Examples of mobile objects 10 include ships, airplanes, drones, railway vehicles, and illustrated automobiles 12 . As shown in FIG. 1 , the combiner 40 constitutes the front window 14 of the automobile 12 .

The image forming device 30 emits image light that forms an image. A user 5 observes the image by receiving the image light. The image forming device 30 is not particularly limited, and various devices capable of forming images can be used. In the example shown in FIG. 1, the image forming device 30 is located within the dashboard. The image forming apparatus 30 is hidden by the dashboard.

Image forming apparatus 30 may employ a dot matrix method. The dot matrix image forming apparatus 30 has a plurality of pixels forming each dot. This image forming apparatus 30 forms a desired image by controlling the light emission state of each pixel. Examples of the image forming device 30 include a transmissive liquid crystal display device, a reflective liquid crystal display device, a laser display device, an electroluminescence display device also called an EL display device, and the like.

The image forming apparatus 30 may have an optical sheet and a light source that illuminates the optical sheet from behind. The optical sheet may have a transparent film and a printed layer having visible light transmittance printed on the transparent film. As another example, the optical sheet may be a light shielding plate provided with openings and transmissive portions. The light source may be a surface light source device that emits light in a planar manner. According to these display devices, display corresponding to the optical sheet, such as pictograms and marks, can be displayed.

Image light from image forming device 30 is projected onto combiner 40 . The image forming apparatus 30 may include a projection optical system 35 indicated by a two-dot chain line in FIG. Projection optics 35 guide image light from image forming device 30 to combiner 40 . Projection optics 35 may include mirrors, lenses, prisms, diffractive optical elements, and combinations thereof.

The combiner 40 directs the image light from the image forming device 30 to the user 5, as shown in FIG. As shown in FIG. 2 , the combiner 40 may include a first substrate 51 , a second substrate 52 , a bonding layer 45 and a hologram element 60 . Combiner 40 is transparent as described above. To give the combiner 40 transparency, the components of the combiner 40 are also transparent.

The combiner 40 has a first side 41 and a second side 42 . In the example shown in FIG. 2, the combiner 40 has a normal direction ND. The first surface 41 and the second surface 42 form a pair of main surfaces of the combiner 40 . The first surface 41 and the second surface 42 face each other in the normal direction ND. The first surface 41 and the second surface 42 spread in a direction perpendicular to the normal direction ND. The first substrate 51 constitutes the first surface 41 . A second substrate 52 constitutes the second surface 42 . The first surface 41 serves as an incident surface for image light from the image forming apparatus 30 .

The first substrate 51 and the second substrate 52 are stacked in the normal direction ND. The bonding layer 45 is located between the first substrate 51 and the second substrate 52 in the normal direction ND. The bonding layer 45 is in contact with the first substrate 51 and the second substrate 52 . The bonding layer 45 is bonded to the first substrate 51 and the second substrate 52 . As a result, the bonding layer 45 bonds the first substrate 51 and the second substrate 52 together. The hologram element 60 is positioned between the first substrate 51 and the second substrate 52 in the normal direction ND. The hologram element 60 is at least partially in contact with the bonding layer 45 . In the illustrated example, the hologram element 60 is separated from both the first substrate 51 and the second substrate 52 in the normal direction ND. A bonding layer 45 is positioned between the hologram element 60 and the first substrate 51 . A bonding layer 45 is positioned between the hologram element 60 and the second substrate 52 . The hologram element 60 is in contact with the bonding layer 45 on its entire outer surface.

In the illustrated example, the normal direction ND of the combiner 40 is the normal direction of the first surface 41, the normal direction of the second surface 42, the normal direction of the first substrate 51, and the normal direction of the second substrate 52. , the normal direction of the bonding layer 45 , and the normal direction of the hologram element 60 . For convenience of understanding, the combiner 40 is shown in a flat plate shape in FIG. 2 and the like. As shown in FIG. 1, combiner 40 may be curved.

The first substrate 51 and the second substrate 52 are transparent plates. The first substrate 51 and the second substrate 52 function as substrates that support the hologram element 60 . In the illustrated example, the first substrate 51 and the second substrate 52 function as windshield members. As a material for the first substrate 51 and the second substrate 52, a glass such as soda lime glass or soda lime glass may be used. As a material for the first substrate 51 and the second substrate 52, a resin such as acrylic resin or polycarbonate may be used. The thickness along the normal direction ND of the first substrate 51 and the second substrate 52 may be 1 mm or more and 5 mm or less. The first substrate 51 and the second substrate 52 may be identically configured with the same material, may be configured with different materials, or may have different configurations.

The first substrate 51 and the second substrate 52 may include multiple layers, as indicated by the two-dot chain lines in FIG. At least one of the first substrate 51 and the second substrate 52 may include a transparent plate 56 and an antireflection layer 57 . The antireflection layer 57 may constitute the first surface 41 , which is the outermost surface of the combiner 40 . The antireflection layer 57 may constitute the second surface 42 , which is the outermost surface of the combiner 40 .

The transparent plate 56 may be a glass plate such as soda lime glass or blue plate glass. The transparent plate 56 may be a resin plate such as acrylic resin or polycarbonate.

The antireflection layer 57 may employ various configurations capable of suppressing reflection. Antireflection layer 57 may have the configuration shown in FIGS. 3A-3C. FIG. 3A shows a single layer antireflection layer 57 . The antireflection layer 57 shown in FIG. 3A has a low refractive index lower than the refractive index of the layer (the transparent plate 56 in the illustrated example) adjacent to this antireflection layer 57 in the normal direction ND. Layer 57a. The antireflection layer 57 shown in FIG. 6B has a low refractive index layer 57a and a high refractive index layer 57b in order from the outermost surface in the third direction D3. The antireflection layer 57 shown in FIG. 3C has multiple low refractive index layers 57a and multiple high refractive index layers 57b. In the example shown in FIG. 3C, the low refractive index layers 57a and the high refractive index layers 57b are repeatedly arranged in order from the first surface 41 side in the third direction D3. In the example shown in FIGS. 3A-3C, antireflection layer 57 suppresses reflections by causing light reflected at different optical interfaces to cancel. The thickness and refractive index of the layers included in the antireflection layer 57 can be appropriately selected according to the wavelength of light whose reflection is to be suppressed. The thickness of the low refractive index layer 57a and the high refractive index layer 57b included in the antireflection layer 57 is less than 780 nm.

The low-refractive-index layer 57a and the high-refractive-index layer 57b can be produced by irradiating an applied layer of a liquid ultraviolet curable resin composition with ultraviolet rays. The liquid ultraviolet curable resin composition for producing the low refractive index layer 57a may contain particles for adjusting the refractive index, such as hollow silica, an initiator, and a fluorine additive. The liquid ultraviolet curable resin composition for producing the high refractive index layer 57b may contain particles for adjusting the refractive index, such as a high refractive filler and an initiator. The low refractive index layer 57a and the high refractive index layer 57b can be produced by physical vapor deposition such as vacuum deposition and sputtering.

From the viewpoint of making a noise image 88 (to be described later) inconspicuous, the reflectance on the surface of the combiner 40 constituted by the antireflection layer 57 may be 1% or less, or 0.5% or less. The reflectance is measured using a spectrophotometer ("UV-3100PC" manufactured by Shimadzu Corporation, compliant with JISK0115) at intervals of 1 nm within a range of measurement wavelengths of 400 nm or more and 700 nm or less. specified as the maximum value. The angle of incidence for measuring the reflectance is the angle of incidence on the combiner 40 at which the diffraction efficiency of the hologram element 60 takes the maximum value. However, if the incident angle to the combiner 40 at which the diffraction efficiency of the hologram element 60 takes the maximum value is less than 5°, it becomes difficult to measure the reflectance. 5°. The incident angle is the angle (°) formed by the traveling direction of the incident light with respect to the normal direction to the plane of incidence, and is less than 90°. The reflectance of the combiner 40 is measured with a black sheet attached to the surface of the combiner 40 opposite to the incident surface. As the black sheet, a sheet having a lightness L ^* value of 30 in the L ^* a ^* b ^* color system specified using a spectrophotometer (“CM-700d” manufactured by Konica Minolta) is used.

The first substrate 51 and the second substrate 52 are not limited to the illustrated example, and may include other functional layers expected to exhibit specific functions. One functional layer may exhibit two or more functions. Examples of functions that can be imparted to the first substrate 51 and the second substrate 52 include a scratch-resistant hard coat (HC) function, an infrared shielding (reflecting) function, an ultraviolet shielding (reflecting) function, an antifouling function, and the like. be.

The bonding layer 45 bonds the first substrate 51 and the second substrate 52 together. The bonding layer 45 is a transparent layer. As the bonding layer 45, a layer made of various materials having adhesiveness or cohesiveness may be used. As an example, the material of the bonding layer 45 may be a thermoplastic resin. The bonding layer 45 made of thermoplastic resin bonds to the first substrate 51 and the second substrate 52 by being heated and pressurized between the first substrate 51 and the second substrate 52 . Polyvinyl butyral (PVB) may be used as the thermoplastic resin forming the bonding layer 45 . The thickness of the bonding layer 45 in the normal direction ND is, for example, 20 μm or more and 1000 μm or less. The bonding layer 45 may be given various functions. Examples of various functions include an antistatic function and an ultraviolet absorption function.

The hologram element 60 diffracts the image light and directs it to the user 5 . The hologram element 60 is transparent in order to impart transparency to the combiner 40 . The hologram element 60 is sheet-like.

Hologram element 60 includes a hologram recording layer 62 . The hologram recording layer 62 is a so-called hologram. The hologram recording layer 62 diffracts light of a specific wavelength incident from a specific incident direction with high diffraction efficiency and directs it in a specific direction. The hologram recording layer 62 records interference fringes for realizing a diffraction function. The hologram recording layer 62 diffracts incident light that satisfies the Bragg condition with high diffraction efficiency and directs it in a specific direction. The hologram recording layer 62 diffracts the image light from the image forming device 30 with high efficiency. The image forming device 30 is arranged at a predetermined position with respect to the combiner 40 . The hologram recording layer 62 diffracts the image light toward a predetermined position with respect to the combiner 40 .

In the example shown in FIG. 2, the hologram recording layer 62 highly efficiently diffracts image light incident along the normal direction ND at an incident angle of 0°. The hologram recording layer 62 highly efficiently diffracts the image light in a second direction D2 orthogonal to the first direction D1 and inclined at 45° with respect to the normal direction ND.

Information about the interference fringes can be recorded in the hologram recording layer 62 in various forms. The hologram recording layer 62 may be a phase-type hologram or an amplitude-type hologram. The hologram recording layer 62 may be a reflection hologram or a transmission hologram. The hologram recording layer 62 may be a relief hologram, or may be a relief hologram as a computer generated hologram (CGH). The hologram recording layer 62 may be a volume hologram in that it is easy to increase the area. The hologram recording layer 62 may be a reflective volume hologram with sharp wavelength selectivity and angle selectivity.

FIG. 4 shows a method of exposing the photosensitive material layer 63 when creating a reflective volume hologram. Examples of the photosensitive material layer 63, which is the raw material of the hologram recording layer 62, include layers such as silver salt sensitive material, gelatin dichromate, crosslinkable polymer, and photopolymer. The thickness of the photosensitive material layer 63 and the obtained hologram recording layer 62 along the normal direction ND may be 1 μm or more and 100 μm or less, or may be 5 μm or more and 40 μm or less.

Coherent light emitted from a single light source is split into reference light L4A and object light L4B. The reference light L4A is shaped into divergent light by the lens 71 for reference light. The photosensitive material layer 63 is irradiated with the shaped reference light L4A. The incident direction of the reference light L4A to the photosensitive material layer 63 matches the incident direction of the image light to the hologram element 60 shown in FIG. The object light L4B is shaped into divergent light by the lens 72 for object light. The photosensitive material layer 63 is irradiated with the shaped object light L4B. Different surfaces of the photosensitive material layer 63 are irradiated with the object light L4B and the reference light L4A. An interference pattern is generated on the photosensitive material layer 63 by the object light L4B and the reference light L4A interfering with each other. The interference pattern is recorded as interference fringes in the photosensitive material layer 63 . In the photosensitive material layer 63 using a crosslinkable polymer, interference fringes are recorded as a refractive index pattern. The hologram recording layer 62 is obtained by desensitizing the photosensitive material layer 63 in which the interference fringes are recorded by exposing the entire surface.

The produced hologram recording layer 62 diffracts the illumination light L3A incident from the same direction as the reference light L4A with high diffraction efficiency. That is, the illumination light L3A incident from the same direction as the reference light L4A can satisfy the Bragg condition for the hologram recording layer 62. FIG. By matching or corresponding the optical path of the reference light L4A with the optical path of the image light, the hologram recording layer 62 can be given the desired angle dependency. The reproduction light L3B diffracted by the fabricated hologram recording layer 62 travels along the optical path of the object light L4B that has passed through the photosensitive material layer 63. FIG. By matching or corresponding the optical path of the object light L4B from the combiner 40 to the user 5, the hologram recording layer 62 can be given a desired angle dependency.

The produced hologram recording layer 62 diffracts light of the same wavelength as the reference light L4A and the object light L4B with high efficiency. That is, light having the same wavelength as the reference light L4A and the object light L4B can satisfy the Bragg condition of the hologram recording layer 62. FIG. Desired wavelength dependence can be imparted to the hologram recording layer 62 by matching or corresponding the wavelengths of the reference light L4A and the object light L4B to the center wavelength of the image light. When the image light is blue light, a laser beam with a wavelength of 430 nm or more and 490 nm or less may be used for exposure of the photosensitive material layer 63 . When the image light is green light, a laser beam with a wavelength of 490 nm or more and 550 nm or less may be used for exposure of the photosensitive material layer 63 . When the image light is red light, a laser beam with a wavelength of 640 nm or more and 770 nm or less may be used for exposing the photosensitive material layer 63 .

The hologram element 60 may have multiple hologram recording layers 62 . The plurality of hologram recording layers 62 can diffract light of different wavelengths with high efficiency. For example, image light from image forming device 30 may include blue light, green light, and red light. In this example, the hologram element 60 includes a hologram recording layer 62 that diffracts blue light with high efficiency, a hologram recording layer 62 that diffracts green light with high efficiency, and a hologram recording layer that diffracts red light with high efficiency. 62 may be included. When the hologram recording layer 62 is a volume hologram, the single hologram recording layer 62 may efficiently diffract light in a plurality of wavelength bands by multiple recording.

In the example shown in FIG. 2, the hologram element 60 includes a hologram recording layer 62 and a first sheet 64 and a second sheet 66 stacked in the normal direction ND. The hologram recording layer 62 is positioned between the first sheet 64 and the second sheet 66 . In the illustrated example, the hologram recording layer 62 is bonded to the first sheet 64 and the second sheet 66 .

The first sheet 64 and the second sheet 66 function as base materials that support the hologram recording layer 62 . The first sheet 64 and the second sheet 66 function as protective layers that protect the hologram recording layer 62 . The first sheet 64 and the second sheet 66 are transparent sheets. Examples of materials for the first sheet 64 and the second sheet 66 include polyethylene terephthalate, polyethylene naphthalate, polycarbonate, polystyrene, cyclic polyolefin, and the like. The thickness along the normal direction ND of the first sheet 64 and the second sheet 66 may be 10 μm or more and 100 μm or less. The first sheet 64 and the second sheet 66 may be identically made of the same material, may be made of different materials, or may have different configurations.

FIG. 5 shows an example of the spectral transmittance of the hologram element 60. As shown in FIG. That is, FIG. 5 shows the transmittance of the hologram element 60 for each wavelength. The hologram element 60 in question includes three hologram recording layers 62 fabricated using the exposure method of FIG. The three hologram recording layers 62 were produced using light of three different wavelengths corresponding to the minimum values of the spectral transmittance shown in FIG. 5 as the reference light L4A and the object light L4B. The optical axis of the reference light L4A was along the normal direction ND of the photosensitive material layer 63 . The optical axis of the object light L4B was orthogonal to the first direction D1 and inclined at 45° with respect to the normal direction ND.

FIG. 6 shows a method of measuring the spectral transmittance shown in FIG. Light L61 from light source 80 passes through collimator lens 81 and illuminates hologram element 60 . The optical axis of the light applied to the hologram element 60 was parallel to the normal direction ND. The spectral transmittance of FIG. 5 was obtained by specifying the ratio of the radiant flux (watt) of the linearly transmitted light to the radiant flux (watt) of the light emitted from the light source 80 as the transmittance for each wavelength. A spectrophotometer ("UV-3100PC" manufactured by Shimadzu Corp., conforming to JIS K0115) was used as a spectral transmittance measuring means including a light source 80, a collimating lens 81 and a photometer 82.

In the spectral transmittance of FIG. 5, the transmittance is lowered at wavelengths λ1, λ2, and λ3. Light corresponding to the drop in transmittance is diffracted by the hologram element 60 . That is, wavelength λ 1 , wavelength λ 2 and wavelength λ 3 are the centers of the selected wavelengths of hologram element 60 .

It is preferable to set an upper limit on the diffraction efficiency of the hologram element 60 from the viewpoint of making a noise image 88 (to be described later) inconspicuous. The diffraction efficiency of the hologram element 60 may be 60% or less, 40% or less, or 20% or less. When light of a plurality of wavelengths is used when exposing the hologram recording layer 62, the hologram element 60 has a peak value of diffraction efficiency for the light of the plurality of wavelengths. For example, light with a wavelength of 460 nm, light with a wavelength of 532 nm, and light with a wavelength of 640 nm can be used to expose the photosensitive material layer 63 . When the hologram element 60 has diffraction efficiency peak values for light of a plurality of wavelengths, the "diffraction efficiency of the hologram element 60" means the maximum value of diffraction efficiency for light of each wavelength.

The diffraction efficiency of the hologram element 60 is measured according to JISZ8791:2011. The diffraction efficiency (%) of the hologram element 60 means the maximum ratio of the radiant flux (watt) of the first-order diffracted light to the radiant flux (watt) of the illumination light to the hologram element 60 . Therefore, the radiant flux (watts) of the first-order diffracted light is measured while the hologram element 60 is irradiated with the illumination light satisfying the Bragg condition. Specifically, the optical axis of the illumination light L3A with respect to the hologram element 60 is aligned with the optical axis of the reference light L4A with respect to the photosensitive material layer 63 during exposure. The radiant flux (watts) of first-order diffracted light can be identified by measuring the radiant flux of diffracted light emitted from hologram element 60 in a direction parallel to the optical path of object light L4B during exposure.

From the viewpoint of making a noise image 88 to be described later inconspicuous, it is preferable to set an upper limit to the full width at half maximum W (nm) in the wavelength distribution of the diffraction efficiency of the hologram element 60 . The full width at half maximum W (nm) in the wavelength distribution of the diffraction efficiency of the hologram element 60 may be 15 nm or less, 10 nm or less, or 5 nm or less. The full width at half maximum W means the length (nm) of a wavelength range that extends to both sides including the wavelength at which the peak value of diffraction efficiency is obtained and ensures a diffraction efficiency that is equal to or more than half the peak value of diffraction efficiency. When the hologram element 60 has diffraction efficiency peak values for light of a plurality of wavelengths, the “full width at half maximum W (nm) in the wavelength distribution of the diffraction efficiency of the hologram element 60” is the diffraction efficiency peak for each wavelength of light. means the maximum full width at half maximum for the value.

Next, the operation of the illustrated head-up display 20 will be described.

As shown in FIG. 7, image light L71 is emitted from the image forming apparatus 30. As shown in FIG. Image light L71 is directed to combiner 40 by projection optics 35 . The image light L<b>71 enters the combiner 40 from the first surface 41 . The image light L71 enters the hologram element 60 of the combiner 40 as illumination light L72. The hologram recording layer 62 of the hologram element 60 diffracts the image light L71 as the illumination light L72 with high efficiency. Image light L71 diffracted by hologram element 60 is reflected by hologram element 60 toward user 5 as reproduction light L73. The user 5 can observe the image formed by the image light L72. The user 5 observes the image not at the position of the image forming apparatus 30 but at a position behind the combiner 40 along the direction parallel to the optical path of the reproduction light L73. That is, according to the head-up display 20, the virtual image 85 observed by the user 5 can be displayed behind the combiner 40 with the user 5 as a reference.

In the illustrated head-up display 20 , the position where the virtual image 85 is displayed can be adjusted by the hologram element 60 . By adjusting the distance DY from the object light lens 72 to the photosensitive material layer 63 with respect to the distance DX from the reference light lens 71 to the photosensitive material layer 63 shown in FIG. You can adjust the position and size. Specifically, the virtual image 85 can be displayed farther from the user 5 and the combiner 40 by increasing the ratio of the distance DY to the distance DX (DY/DX). The size of the virtual image 85 can be enlarged by increasing the ratio of the distance DY to the distance DX (DY/DX).

By the way, when a conventional head-up display is used in a place where the sun, outdoor lights, etc. are installed, the sun and outdoor lights may be reflected in the combiner as an unintended noise image 88 . Moreover, the noise image 88 of the sun, outdoor lights, etc. is observed at a position different from the actual position of the sun, outdoor lights, etc. FIG. The appearance of such a noise image 88 degrades the display quality of the head-up display 20 and reduces visibility through the combiner 40 .

The appearance of the noise image 88 is considered as follows. As shown in FIG. 7, noise light L74 from the sun, outdoor lights, or the like enters the combiner 40 via the second surface 42, unlike the image light L72. The noise light L74 reaches the first surface 41 and is reflected by the first surface 41 . After that, the noise light L74 enters the hologram element 60. As shown in FIG. When the optical path of the noise light L74 satisfies the Bragg diffraction condition of the hologram recording layer 62, the noise light L74 is diffracted by the hologram recording layer 62 with high efficiency and travels toward the user 5. FIG. User 5 observes a noise image 88 located behind combiner 40 .

As described above, in order to make the noise image 88 inconspicuous, it is effective to reduce the reflectance of the antireflection layer 57 forming the first surface 41 . By reducing the reflectance of the antireflection layer 57, the radiant flux (W) of the noise light L74 incident on the hologram element 60 can be reduced. Specifically, the reflectance of the antireflection layer 57 may be 1% or less, or 0.5% or less. The reflectance (%) of the antireflection layer 57 can be adjusted by the thickness of the antireflection layer 57, the number of layers included in the antireflection layer 57, the refractive index of the material forming the antireflection layer 57, and the like.

In order to make the noise image 88 inconspicuous, it is effective to reduce the diffraction efficiency of the hologram element 60 . By reducing the diffraction efficiency of the hologram element 60, the noise image 88 can be darkened. Specifically, the diffraction efficiency of the hologram element 60 may be 60% or less, 40% or less, or 20% or less.

Furthermore, in order to make the noise image 88 inconspicuous, it is effective to reduce the full width at half maximum W (nm) in the wavelength distribution of the diffraction efficiency of the hologram element 60 . The noise image 88 can be darkened by reducing the full width at half maximum W (nm) in the wavelength distribution of the diffraction efficiency of the hologram element 60 . Specifically, the full width at half maximum W (nm) in the wavelength distribution of the diffraction efficiency of the hologram element 60 may be 15 nm or less, 10 nm or less, or 5 nm or less.

The diffraction efficiency (%) of hologram element 60 and the full width at half maximum W (nm) in the wavelength distribution of the diffraction efficiency of hologram element 60 can be adjusted by changing the manufacturing conditions of hologram element 60 . For example, the diffraction efficiency (%) and Full width at half maximum W (nm) is adjustable. The diffraction efficiency (%) and the full width at half maximum W (nm) can be adjusted also by the intensity of the exposure light and the exposure time when the photosensitive material layer 63 is exposed.

Furthermore, the inventors of the present invention have made extensive studies and found that the noise image 88 can be made less conspicuous by reducing the noise diffraction rate (%). As shown in FIG. 8, light L74 emitted from the test light source 92 enters the combiner 40 from the second surface 42, is reflected by the first surface 41, is diffracted by the hologram element 60, and emerges from the first surface 41. , L81 is defined as the noise image luminance (Watts/steradian). The luminance caused by the light emitted from the test light source 92 is defined as light source luminance (Watts/steradian). The ratio of light source luminance to noise image luminance is defined as noise diffraction rate (%). In order to make the noise image 88 inconspicuous, it is effective to set the noise diffraction rate (%) to 0.11% or less, and it may be 0.05% or less, or 0.02% or less.

FIG. 8 shows a test apparatus 90 for measuring noise diffraction rate (%). The test apparatus 90 includes a test light source 92 , a collimating lens 93 and a luminance meter 94 . The light L81 from the test light source 92 is shaped by the collimator lens 93 and then directed toward the combiner 40 to be measured. The test light source 92 is a natural light LED (model number: equivalent to HLV2-22-3W) manufactured by CCS Corporation. FIG. 9 shows the spectral distribution of the test light source 92. As shown in FIG. That is, FIG. 9 shows the intensity ratio of light of each wavelength emitted from the test light source 92 . The test light source 92 is positioned with respect to the hologram element 60 so that the light reflected by the first surface 41 satisfies the Bragg condition of the hologram element 60 . In the case where the hologram element 60 is manufactured through the exposure process shown in FIG. Match the optical axis. A luminance measuring device 94 measures the noise image luminance on the second surface 42 of the combiner 40 from the emission direction of the first-order diffracted light. The luminance of the test light source 92 is also measured using the luminance measuring device 94 . The brightness of the light source is measured in a direction parallel to the optical path of the light L81. The luminance measuring device 94 is a two-dimensional color luminance meter (CA-2500) manufactured by Konica Minolta.

Furthermore, the inventors of the present invention have made extensive studies and found that the noise image 88 can be made inconspicuous by satisfying the following conditional expression (A). “H” in conditional expression (A) is the diffraction efficiency (%) of the hologram element 60 . When the hologram element 60 has diffraction efficiency peak values at a plurality of wavelengths used when the hologram recording layer 62 is exposed, the maximum value (%) of the diffraction efficiency peak values is the value of “H”. “W” in conditional expression (A) is the full width at half maximum W in the wavelength distribution of the diffraction efficiency of the hologram element 60 . When the hologram element 60 has diffraction efficiency peak values at a plurality of wavelengths, the maximum value (nm) of the full width at half maximum specified for the plurality of peak values is the value of “W”.
“R” in conditional expression (A) is the reflectance (%) of the first surface of the combiner 40 .
(H/100)×W×(R/100)×(1−(R/100))≦0.098
... conditional expression (A)

Here, an example of experiments conducted by the inventors of the present invention will be described.

Samples 1-10 of the combiner 40 shown in FIG. 10 were made. The combiner 40 had a first substrate 51 , a second substrate 52 , a bonding layer 45 and a hologram element 60 . The hologram element 60 had a first sheet 64 , a hologram recording layer 62 and a second sheet 66 . In samples 1-3 and samples 6-10, the first substrate 51 had a transparent plate 56 and an antireflection layer 57 . The combiner 40 according to samples 1 to 10 was laminated glass in which the hologram element 60 was arranged in the bonding layer 45 .

The first substrate 51 and the second substrate 52 had a square shape of 150 mm×150 mm when observed from the normal direction ND. The hologram element 60 had a square shape of 100 mm×100 mm when observed from the normal direction ND. The hologram element 60 was arranged with respect to the first substrate 51 and the second substrate 52 so that the periphery of the hologram element 60 was located 25 mm inside from the periphery of the first substrate 51 and the second substrate 52 .

<Sample 1>
In sample 1, the thickness T1 along the normal direction ND of the first substrate 51 was set to 2 mm. A blue plate glass was used as the transparent plate 56 . The reflectance at the first surface 41 constituted by the antireflection layer 57 was 1%. The thickness T2 along the normal direction ND of the second substrate 52 was set to 2 mm. Soda plate glass was used as the second substrate 52 . Polyvinyl butyral (PVB) was used as the bonding layer 45 . A thickness T3 of the bonding layer 45 between the hologram element 60 and the first substrate 51 was set to 380 μm. A thickness T3 of the bonding layer 45 between the hologram element 60 and the second substrate 52 was set to 380 μm.

Hologram element 60 had a single hologram recording layer 62 . This single hologram recording layer 62 had wavelength selectivity with respect to blue wavelength (460 nm) light, green wavelength (532 nm) light, and red wavelength (640 nm) light by multiple exposure. . That is, the blue wavelength light, the green wavelength light, and the red wavelength light each satisfied the Bragg condition for the single hologram recording layer 62 . The hologram recording layer 62 was produced under the exposure conditions shown in FIG. 4 using blue wavelength light, green wavelength light, and red wavelength light. The hologram recording layer 62 had diffraction characteristics similar to those of the hologram recording layer 62 shown in FIG. That is, the hologram recording layer 62 is designed so that the Bragg condition is satisfied by light incident along the normal direction ND. The hologram recording layer 62 diffracted the incident light that satisfies the Bragg condition with high efficiency in a second direction D2 orthogonal to the first direction D1 and inclined at 45° with respect to the normal direction ND.

The hologram element 60 had diffraction efficiency peak values at three wavelengths corresponding to the hologram recording layer 62 . The diffraction efficiency of the hologram element 60 was calculated as the maximum value of the peak values of the three diffraction efficiencies, and was 60%. The full width at half maximum W in the wavelength distribution of the diffraction efficiency of the hologram element was 5 nm. The full width at half maximum W was the maximum value of the full width at half maximum specified for the three diffraction efficiency peak values.

The hologram recording layer 62 was made using a crosslinkable polymer. The thickness T6 of the hologram recording layer 62 was 15 μm. The first sheet 64 and the second sheet 66 were polyethylene terephthalate sheets. The thickness T7 of the first sheet 64 was 50 μm. The thickness T8 of the second sheet 66 was 38 μm.

<Sample 2>
Sample 2 differs from Sample 1 in the full width at half maximum W in the wavelength distribution of the diffraction efficiency of the hologram element. Sample 2 was otherwise similar to Sample 1.

In sample 2, the hologram element 60 had diffraction efficiency peak values at three wavelengths corresponding to the hologram recording layer 62 . The diffraction efficiency of the hologram element 60 was calculated as the maximum value of the peak values of the three diffraction efficiencies, and was 60%. The full width at half maximum W in the wavelength distribution of the diffraction efficiency of the hologram element was 10 nm. The full width at half maximum W was the maximum value of the full width at half maximum specified for the three diffraction efficiency peak values.

In Sample 2, the reflectance on the first surface 41 constituted by the antireflection layer 57 was 1%.

<Sample 3>
Sample 3 differs from Sample 1 in the full width at half maximum W in the wavelength distribution of the diffraction efficiency of the hologram element. Sample 3 was otherwise similar to Sample 1.

In sample 3, the hologram element 60 had diffraction efficiency peak values at three wavelengths corresponding to the hologram recording layer 62 . The diffraction efficiency of the hologram element 60 was calculated as the maximum value of the peak values of the three diffraction efficiencies, and was 60%. The full width at half maximum W in the wavelength distribution of the diffraction efficiency of the hologram element was 15 nm. The full width at half maximum W was the maximum value of the full width at half maximum specified for the three diffraction efficiency peak values.

In Sample 3, the reflectance at the first surface 41 composed of the antireflection layer 57 was 1%.

<Sample 4>
Sample 4 differed from Sample 1 in that first substrate 51 did not include antireflection layer 57 . Sample 4 was otherwise similar to Sample 1.

In sample 4, the hologram element 60 had diffraction efficiency peak values at three wavelengths corresponding to the hologram recording layer 62 . The diffraction efficiency of the hologram element 60 was calculated as the maximum value of the peak values of the three diffraction efficiencies, and was 60%. The full width at half maximum W in the wavelength distribution of the diffraction efficiency of the hologram element was 5 nm. The full width at half maximum W was the maximum value of the full width at half maximum specified for the three diffraction efficiency peak values.

In sample 4, the reflectance on the first surface 41 formed by the transparent plate 56 of the first substrate 51 was 4%.

<Sample 5>
Sample 5 differed from Sample 2 in that first substrate 51 did not include antireflection layer 57 . Sample 5 was otherwise similar to Sample 2.

In sample 5, the hologram element 60 had diffraction efficiency peak values at three wavelengths corresponding to the hologram recording layer 62 . The diffraction efficiency of the hologram element 60 was calculated as the maximum value of the peak values of the three diffraction efficiencies, and was 60%. The full width at half maximum W in the wavelength distribution of the diffraction efficiency of the hologram element was 10 nm. The full width at half maximum W was the maximum value of the full width at half maximum specified for the three diffraction efficiency peak values.

In Sample 5, the reflectance on the first surface 41 formed by the transparent plate 56 of the first substrate 51 was 4%.

<Sample 6>
Sample 6 differed from Sample 3 in that first substrate 51 did not include antireflection layer 57 . Sample 6 was otherwise similar to Sample 3.

In sample 6, the hologram element 60 had diffraction efficiency peak values at three wavelengths corresponding to the hologram recording layer 62 . The diffraction efficiency of the hologram element 60 was calculated as the maximum value of the peak values of the three diffraction efficiencies, and was 60%. The full width at half maximum W in the wavelength distribution of the diffraction efficiency of the hologram element was 15 nm. The full width at half maximum W was the maximum value of the full width at half maximum specified for the three diffraction efficiency peak values.

In sample 6, the reflectance on the first surface 41 formed by the transparent plate 56 of the first substrate 51 was 4%.

<Sample 7>
Sample 7 differed from Sample 3 in diffraction efficiency H of the hologram element. Sample 7 was otherwise similar to Sample 3.

In sample 7, the hologram element 60 had diffraction efficiency peak values at three wavelengths corresponding to the hologram recording layer 62 . The diffraction efficiency of the hologram element 60 was calculated as the maximum value of the peak values of the three diffraction efficiencies, and was 80%. The full width at half maximum W in the wavelength distribution of the diffraction efficiency of the hologram element was 15 nm. The full width at half maximum W was the maximum value of the full width at half maximum specified for the three diffraction efficiency peak values.

In Sample 7, the reflectance on the first surface 41 constituted by the antireflection layer 57 was 1%.

<Sample 8>
Sample 8 differed from Sample 3 in diffraction efficiency H of the hologram element. Sample 8 was otherwise similar to Sample 3.

In sample 8, the hologram element 60 had diffraction efficiency peak values at three wavelengths corresponding to the hologram recording layer 62 . The diffraction efficiency of the hologram element 60 was calculated as the maximum value of the peak values of the three diffraction efficiencies, and was 40%. The full width at half maximum W in the wavelength distribution of the diffraction efficiency of the hologram element was 15 nm. The full width at half maximum W was the maximum value of the full width at half maximum specified for the three diffraction efficiency peak values.

In Sample 8, the reflectance on the first surface 41 composed of the antireflection layer 57 was 1%.

<Sample 9>
Sample 9 differed from Sample 3 in diffraction efficiency H of the hologram element. Sample 9 was otherwise similar to Sample 3.

In sample 9, the hologram element 60 had diffraction efficiency peak values at three wavelengths corresponding to the hologram recording layer 62 . The diffraction efficiency of the hologram element 60 was calculated as the maximum value of the three diffraction efficiency peak values, and was 20%. The full width at half maximum W in the wavelength distribution of the diffraction efficiency of the hologram element was 15 nm. The full width at half maximum W was the maximum value of the full width at half maximum specified for the three diffraction efficiency peak values.

In Sample 9, the reflectance on the first surface 41 composed of the antireflection layer 57 was 1%.

<Sample 10>
Sample 10 differed from Sample 2 in the diffraction efficiency H of the hologram element and the reflectance at the antireflection layer 57 . Sample 10 was otherwise similar to Sample 2.

In the sample 10, the hologram element 60 had diffraction efficiency peak values at three wavelengths corresponding to the hologram recording layer 62. FIG. The diffraction efficiency of the hologram element 60 was calculated as the maximum value of the peak values of the three diffraction efficiencies and was 50%. The full width at half maximum W in the wavelength distribution of the diffraction efficiency of the hologram element was 10 nm. The full width at half maximum W was the maximum value of the full width at half maximum specified for the three diffraction efficiency peak values.

In the sample 10, the reflectance on the first surface 41 composed of the antireflection layer 57 was 2%.

<Evaluation>
The presence or absence of the noise image 88 was confirmed for samples 1 to 10. FIG. Samples 1-10 were placed on the windshield of an actual automobile. By adjusting the position and orientation of the car, a noise image 88 of outdoor lights was made to appear in the combiner 40 of samples 1-10. Degradation of visibility through the combiner 40 due to the noise image 88 was evaluated. The evaluation results are described in the "Evaluation" column of Table 1. "A" was entered in the "Evaluation" column for the samples in which the noise image 88 was inconspicuous. "Z" was entered in the column of "evaluation" for the sample whose visibility through the combiner 40 was greatly deteriorated by the noise image 88. A dark and small noise image 88 was confirmed in samples 1-3 and 8-10. However, it was difficult to discriminate that the noise image 88 was an outdoor light. Behind the noise image 88 was also observable. A bright and large noise image 88 was confirmed in samples 4-7. The background behind the noise image 88 could not be observed.

<Confirmation of Condition 1>
For samples 3, 6 and 10, the noise diffraction rate (%) was measured by the measurement method using the test apparatus 90 described with reference to FIGS. 8 and 9. FIG. The light source luminance was 100,000 (watts/steradian). For sample 3, the noise image luminance was 19 (watts/steradian). For sample 6, the noise image luminance was 140 (Watts/steradian). For sample 10, the noise image luminance was 110 (watts/steradian). The noise diffraction rate of sample 3 was 0.019%. Sample 26 noise diffraction index was 0.14%. For sample 10, the noise diffraction rate was 0.11%. The noise diffraction rate is entered in the "Value" column of "Condition 1" in Table 1. "A" is entered in the column of "Judgment" of "Condition 1" in Table 1 for samples having a noise diffraction index of 0.11 or less as described above. "Z" was entered in the column of "Judgment" of "Condition 1" in Table 1 for the samples whose noise diffraction index was greater than 0.11.

<Confirmation of Condition 2>
For samples 1 to 10, the value of the left side of conditional expression (A) was calculated. The value of the left side of conditional expression (A) is entered in the column of "value" of "condition 2" in Table 1. "A" is entered in the column of "Determination" of "Condition 2" in Table 1 for the samples satisfying the conditional expression (A). In other words, "A" was entered in the column of "determination" of "Condition 2" in Table 1 for the samples for which the value of the left side of conditional expression (A) was 0.098 or less. "Z" was entered in the column of "Judgment" of "Condition 2" in Table 1 for the samples that did not satisfy the conditional expression (A). In other words, "Z" was entered in the column of "determination" of "Condition 2" in Table 1 for samples in which the value of the left side of conditional expression (A) was greater than 0.098.

In one embodiment described above, the combiner 40 includes a first surface 41 and a second surface 42 and is used in the head-up display 20 . The combiner 40 includes a first substrate 51 forming a first surface 41, a second substrate 52 forming a second surface 42, a bonding layer 45 bonding the first substrate 51 and the second substrate 52, and the first substrate and a hologram element 60 located between 51 and the second substrate 52 .

In one embodiment, light L74 emitted from the test light source 92, incident on the combiner 40 from the second surface 42, reflected by the first surface 41, diffracted by the hologram element 60, and emitted from the first surface 41, The noise diffraction rate (%) of the noise image luminance (Watt/steradian) at the combiner 40 caused by L81 to the luminance at the light source (Watt/steradian) caused by the light emitted from the test light source 92 was 0.11. % or less. According to this example, the noise image 88 can be made inconspicuous. Thereby, the display quality of the head-up display 20 can be improved, and the visibility through the combiner 40 can be improved.

In one embodiment, the first substrate 51 may include an antireflection layer 57 forming the first surface 41 . The reflectance on the first surface 41 may be 1% or less. According to this example, the noise image 88 can be made inconspicuous. Thereby, the display quality of the head-up display 20 can be improved, and the visibility through the combiner 40 can be improved.

In one embodiment, the diffraction efficiency of the hologram element 60 may be 60% or less. According to this example, the noise image 88 can be made inconspicuous. Thereby, the display quality of the head-up display 20 can be improved, and the visibility through the combiner 40 can be improved.

In one embodiment, the diffraction efficiency H (%) of the hologram element 60, the full width at half maximum W (nm) in the wavelength distribution of the diffraction efficiency of the hologram element 60, and the reflectance R (%) at the first surface 41 are given by may satisfy the conditional expression (A). According to this example, the noise image 88 can be made inconspicuous. Thereby, the display quality of the head-up display 20 can be improved, and the visibility through the combiner 40 can be improved.
(H/100)×W×(R/100)×(1−(R/100))≦0.098
... conditional expression (A)
Although one embodiment has been described with reference to specific examples, the above specific examples do not limit one embodiment. The embodiment described above can be implemented in various other specific examples, and various omissions, replacements, changes, additions, etc. can be made without departing from the scope of the invention. For example, the second substrate 52 may include an antireflection layer forming the second surface 42 .

D1: first direction, D2: second direction, D3: third direction, ND: normal direction, L4A: reference light, L4B: object light, L3A: illumination light, L3B: reproduced light, 5: user, 10 : moving body 12: automobile 14: front window 20: head-up display 30: image forming apparatus 35: projection optical system 40: combiner 41: first surface 42: second surface 45: junction Layer, 51: first substrate, 52: second substrate, 56: transparent plate, 57: antireflection layer, 57a: low refractive index layer, 57b: high refractive index layer, 60: hologram element, 62: hologram recording layer, 63: photosensitive material layer, 64: first sheet, 66: second sheet, 71: reference light lens, 72: object light lens, 80: light source, 81: collimating lens, 82: photometer, 85: virtual image , 88: noise image, 90: test device, 92: test light source, 94: luminance measuring instrument

Claims (10)

A combiner for a head-up display including a first side and a second side,
a first substrate forming the first surface;
a second substrate forming the second surface;
a bonding layer that bonds the first substrate and the second substrate;
a hologram element positioned between the first substrate and the second substrate;
Luminance (Watt/steradian ) to the luminance (Watt/steradian) at the light source due to the light emitted from the light source is 0.11% or less. The combiner for a head-up display according to claim 1, wherein said first substrate includes an antireflection layer forming said first surface. The combiner for a head-up display according to claim 1 or 2, wherein the reflectance on said first surface is 1% or less. The diffraction efficiency H (%) of the hologram element, the full width at half maximum W (nm) in the wavelength distribution of the diffraction efficiency of the hologram element, and the reflectance R (%) at the first surface are
(H/100)×W×(R/100)×(1−(R/100))≦0.098
The combiner for a head-up display according to any one of claims 1 to 3, wherein: The combiner for a head-up display according to any one of claims 1 to 4, wherein said hologram element has a diffraction efficiency of 60% or less. A combiner for a head-up display including a first side and a second side,
a first substrate forming the first surface;
a second substrate forming the second surface;
a bonding layer that bonds the first substrate and the second substrate;
a hologram element positioned between the first substrate and the second substrate;
The first substrate includes an antireflection layer forming the first surface,
A combiner for a head-up display, wherein the first surface has a reflectance of 1% or less. a first substrate and a second substrate;
a bonding layer that bonds the first substrate and the second substrate;
a hologram element positioned between the first substrate and the second substrate;
A combiner for a head-up display, wherein the hologram element has a diffraction efficiency of 60% or less. A combiner for a head-up display including a first side and a second side,
a first substrate forming the first surface;
a second substrate forming the second surface;
a bonding layer that bonds the first substrate and the second substrate;
a hologram element located between the first substrate and the second substrate;
The first substrate includes an antireflection layer forming the first surface,
The diffraction efficiency H (%) of the hologram element, the full width at half maximum W (nm) in the wavelength distribution of the diffraction efficiency of the hologram element, and the reflectance R (%) at the first surface are
(H/100)×W×(R/100)×(1−(R/100))≦0.098
Combiner for head-up display. an image forming device that emits image light;
and the combiner according to any one of claims 1 to 8, which is irradiated with the image light. A moving object comprising the head-up display according to claim 9 .

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