US-12625368-B2 - Head-up display system and transportation machine

Abstract

Provided is a head-up display system and a transportation machine including the head-up display system, the head-up display system including a windshield glass having a selective reflection layer and a projector including laser light sources of three colors of blue light, green light, and red light for forming a projection image on the windshield glass, in which the selective reflection layer includes the following selective reflection central wavelengths λ B , λ G , and λ R at a light incidence angle of 60°, 400 ⁢ nm ≤ λ B < 500 ⁢ ⁢ nm 500 ⁢ nm ≤ λ G < 600 ⁢ ⁢ nm 600 ⁢ nm ≤ λ R < 700 ⁢ ⁢ nm all of X B /X G , X B /X R , and X G /X R are in a range of 0.80 to 1.20. In the above, X B =R B ×L B , X G =R G ×L G , and X R =R R ×L R . R B , R G , and R R indicate a natural light reflectivity at λ B , λ G , and λ R , and L B , L G , and L R indicate the brightness of blue, green, and red laser beam emitted from the projector.

Inventors

• Akihiro Anzai
• Eiichiro Aminaka

Assignees

• FUJIFILM CORPORATION

Dates

Publication Date

20260512

Application Date

20240220

Priority Date

20210930

Claims (10)

1. 1 . A head-up display system comprising: a windshield glass having a selective reflection layer; and a projector including a laser light source for forming a projection image on the windshield glass, wherein the selective reflection layer includes three wavelengths of λ B , λ G , and λ R as selective reflection central wavelengths at a light incidence angle of 60°, 400 ⁢ nm ≤ λ B < 500 ⁢ ⁢ nm 500 ⁢ nm ≤ λ G < 600 ⁢ ⁢ nm 600 ⁢ nm ≤ λ R < 700 ⁢ ⁢ nm the laser light source emits laser beam of three colors of blue light, green light, and red light, and all of the following regulations (a) to (c) are satisfied, regulation (a) 0.80≤X B /X G ≤1.20 regulation (b) 0.80≤X B /X R ≤1.20 regulation (c) 0.80≤X G /X R ≤1.20 in the regulations, X B =R B ×L B , X G =R G ×L G , and X R =R R ×L R , R B indicates a natural light reflectivity of the selective reflection layer at λ B , R G indicates a natural light reflectivity of the selective reflection layer at λ G , and R R indicates a natural light reflectivity of the selective reflection layer at λ R , and L B represents brightness of blue laser beam in light emitted from the projector, L G represents brightness of green laser beam in the light emitted from the projector, and L R represents brightness of red laser beam in the light emitted from the projector.
2. 2 . The head-up display system according to claim 1 , wherein all of the following regulations (a1) to (c1) are satisfied, regulation (a1) 0.90≤X B /X G ≤1.10 regulation (b1) 0.90≤X B /X R ≤1.10 regulation (c1) 0.90≤X G /X R ≤1.10 in the regulations, X B , X G , and X R have the same meanings as X B , X G , and X R described above.
3. 3 . The head-up display system according to claim 1 , wherein the natural light reflectivities R B , R G , and R R of the selective reflection layer satisfy a relationship of R B >R G ≥R R .
4. 4 . The head-up display system according to claim 1 , wherein the natural light reflectivities R B and R G of the selective reflection layer satisfy a relationship of R B /R G ≥1.10.
5. 5 . The head-up display system according to claim 1 , wherein in the selective reflection layer, all of the selective reflection central wavelengths λ B , λ G , and λ R at the light incidence angle of 60° have a half-width of 100 nm or less, and all of the natural light reflectivities R B , R G , and R R are 25% or more.
6. 6 . The head-up display system according to claim 2 , wherein in the selective reflection layer, all of the selective reflection central wavelengths λ B , λ G , and λ R at the light incidence angle of 60° have a half-width of 100 nm or less, and wherein all of the natural light reflectivities R B , R G , and R R of the selective reflection layer are 25% or more, the natural light reflectivities R B , R G , and R R of the selective reflection layer satisfy a relationship of R B >R G ≥R R , and the natural light reflectivities R B and R G of the selective reflection layer satisfy a relationship of R B /R G ≥1.10.
7. 7 . The head-up display system according to claim 1 , wherein the windshield glass includes at least one polarization conversion layer.
8. 8 . The head-up display system according to claim 1 , wherein the selective reflection layer consists of a cholesteric liquid crystal.
9. 9 . The head-up display system according to claim 1 , wherein the selective reflection layer is formed by laminating an optically anisotropic layer and an optically isotropic layer.
10. 10 . A transportation machine comprising: the head-up display system according to claim 1 .

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a Continuation of PCT International Application No. PCT/JP2022/035856 filed on Sep. 27, 2022, which claims priority under 35 U.S.C. § 119 (a) to Japanese Patent Application No. 2021-162101 filed in Japan on Sep. 30, 2021. Each of the above applications is hereby expressly incorporated by reference, in its entirety, into the present application. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a head-up display system and a transportation machine. 2. Description of the Related Art Recently, it is known as a so-called head-up display or head-up display system for providing various pieces of information such as maps, traveling speed, or vehicle conditions to a driver or the like by projecting images on a windshield glass of a vehicle or other moving objects. By using the head-up display system, drivers or other subjects observe virtual images of images that are projected on the windshield glass and that include the above described various pieces of information. A virtual image formation position is positioned on the driver's field of the vehicle outer side of the windshield glass. The virtual image formation position is usually positioned at the driver's field more than 1000 mm away from the windshield glass, and the outer side of the windshield glass. Therefore, the driver can obtain the above described various pieces of information while looking at the outer side in driver's field without significantly moving his/her line of sight. Thus, in a case of using the head-up display system, it is expected to drive more safely while obtaining various pieces of information. In a head-up display system, in order to reduce a double image generated by reflection of projection light on a front surface and a rear surface of a windshield glass, a technique of using a curved windshield for a vehicle formed of laminated glass having a wedge-shaped cross-sectional shape is known. In addition, studies have been made on a technique in which P-polarized light is made incident on a glass surface to utilize the Brewster's angle, and reflected light from the glass surface is made close to zero. For example, JP2018-81296A describes a windshield glass including a λ/2 retardation layer and four or more cholesteric liquid crystal reflective layers having different central wavelengths of selective reflection. According to the description of JP2018-81296A, by including a cholesteric liquid crystal layer having a central wavelength of selective reflection at 350 nm or more and less than 490 nm as one layer of the cholesteric liquid crystal reflection layers, it is possible to provide a windshield glass in which appearance tint in a direction perpendicular to the windshield glass is transparent and appearance is not impaired even under external light. SUMMARY OF THE INVENTION In a head-up display in which a P-polarized light reflection film is incorporated into a windshield glass, it is required that the appearance tint is transparent (white light appears white) even in a case of being viewed from various angles from the viewpoint of the clearness and designability of a display image in addition to the legal regulation that the transmittance is set to 70% or more. In order to realize this, it is considered that a laser having a narrow band of a luminescence wavelength is used as a light source of the imager, and a selective reflection layer having a narrow half-width of each reflected light and a high reflectivity is used as the reflection layer of the P-polarized light reflection film described in Examples of JP2018-81296A. It is considered that by using such a light source of an imager and the selective reflection layer in combination, the imager light can be efficiently reflected, and the brightness of the image (clearness of the display image) can be increased while maintaining the transmittance high. However, as a result of repeated studies by the present inventors, it has been found that, in the windshield glass described in JP2018-81296A, in a case where the reflectivity is set such that the appearance tint becomes transparent, there is a problem in that the tint of a display image (hereinafter, referred to as “image tint”) becomes red. An object of the present invention is to provide a head-up display system that is a head-up display including a laser light source for forming a projection image and a windshield glass and that has a neutral image tint, and a transportation machine including the head-up display. As a result of intensive examination conducted by the present inventors in view of the above-described problems, it was found that the above-described problems can be solved by controlling a balance between reflectivity of blue light, green light, and red light of a selective reflection layer in a windshield glass and luminescence intensity (brightness) of laser beam of three colors of blue light, green light, and red light in a