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JP-7855602-B2 - Virtual image display device, head-up display system, and transport aircraft

JP7855602B2JP 7855602 B2JP7855602 B2JP 7855602B2JP-7855602-B2

Inventors

  • 安西 昭裕

Assignees

  • 富士フイルム株式会社

Dates

Publication Date
20260508
Application Date
20221031
Priority Date
20211105

Claims (13)

  1. A virtual image display device configured to be mounted on a transport aircraft, wherein P-polarized image display light is incident on the projection unit, A virtual image display device having an image display device that emits projected image light, wherein, on the optical path that guides the projected image light to the projection unit, a diffraction reflector with positive optical power and a half-wave plate with a front retardation of 200 nm to 400 nm are provided in order from the image display device side.
  2. The virtual image display device according to claim 1, wherein, on the optical path, a half-wave plate with a front retardation of 200 nm to 400 nm is provided between the diffraction-reflecting element with positive optical power and the image display device.
  3. The virtual image display device according to claim 1 or 2, wherein the diffraction-reflective element with positive optical power is a reflective hologram element having a fixed refractive index distribution with a photosensitive material.
  4. The virtual image display device according to claim 1 or 2, wherein the diffraction-reflecting element having positive optical power comprises an alignment film and a liquid crystal layer, has a liquid crystal alignment pattern corresponding to the periodic pattern of the alignment film, and is a diffraction element having the function of diffracting and reflecting incident light.
  5. The virtual image display device according to claim 1 or 2 , wherein, on the optical path, a transmissive optical element with negative optical power is provided between the diffractive reflective element with positive optical power and the image display device.
  6. The virtual image display device according to claim 5, wherein the aforementioned negative optical power transmissive optical element is a transmissive hologram element having a refractive index distribution with a fixed photosensitive material.
  7. The virtual image display device according to claim 5, wherein the aforementioned negative optical power transmission optical element is a diffraction element having an alignment film and a liquid crystal layer, having a liquid crystal alignment pattern corresponding to the periodic pattern of the alignment film, and having the function of diffracting and transmitting incident light.
  8. The virtual image display device according to claim 5, wherein the aforementioned negative optical power transmissive optical element is a lens that refracts the projected image light.
  9. The virtual image display device according to claim 1 or 2 , wherein the image display device is a light field display.
  10. A head-up display system comprising a windshield glass having a first glass plate, a P-polarizing reflective film, and a second glass plate, and a virtual image display device according to claim 1 or 2 .
  11. The head-up display system according to claim 10, wherein the P-polarizing reflective film has a layer made of cholesteric liquid crystal.
  12. The head-up display system according to claim 10, wherein the P-polarizing reflective film has a layer formed by laminating an optically anisotropic layer and an optically isotropic layer.
  13. A transport aircraft equipped with the head-up display system according to claim 10.

Description

This invention relates to a virtual image display device, a head-up display system, and a transport aircraft. A head-up display (hereinafter also referred to as "HUD") system is known that projects images onto the windshield glass of a vehicle, providing the driver with driving assistance information such as route guidance, driving speed, and warnings through the windshield glass. The HUD system allows the observer to obtain various driving assistance information, such as route guidance, driving speed, and vehicle status, without significantly shifting their gaze or focus while viewing the outside world in front of them, enabling safer and less stressful driving. The basic configuration of a HUD is generally as follows: First, projected light from an image display device integrated into the dashboard is formed as an intermediate image on the surface of an intermediate image screen (diffuser). This intermediate image is magnified by a concave mirror (magnifying mirror), passes through a transmissive window provided in the dashboard, and is reflected by a windshield glass containing a half-mirror with a cholesteric liquid crystal layer or dielectric multilayer film, and guided to the driver. From this point onward, the configuration from the image display device to projection onto the windshield is also referred to as a virtual image display device. Drivers perceive this intermediate image as a so-called virtual image, positioned in front of the windshield glass. In other words, drivers can perceive the driving assistance information as if it were floating above the road. Various proposals have been made regarding virtual image display devices that constitute HUD systems. For example, Patent Document 1 describes a virtual image display device in which a concave mirror is replaced with a positive diffractive optical element (hereinafter also referred to as a positive diffractive reflector element) that has positive optical power. According to Patent Document 1, the virtual image display device with the above configuration can improve the robustness of visibility in response to the curvature of virtual images, and because the diffractive optical element is a flat plate, it is easier to miniaturize compared to HUD systems using concave mirrors, and thus can be mounted in vehicles. In typical HUD systems, the image projection display device of the HUD unit often emits S-polarized light, which is reflected by the windshield glass to allow the driver to see a virtual image. However, because the image light is reflected from both the front and rear surfaces of the windshield glass, there is a problem in that a double image is perceived. Furthermore, because the image light is S-polarized, there is a problem in that the virtual image is not visible when the driver is wearing polarized sunglasses. To solve these problems, research is being conducted on HUD systems that incorporate a P-polarized reflective film into the windshield glass, making the light emitted from the HUD unit P-polarized. Furthermore, as a technique for displaying virtual images in multi-focal or 3D, for example, as described in Patent Document 2, a technique using a light field display as a projection image display device is known. In a light field display, by forming microlenses on the light-emitting pixels, the focal point of each light-emitting pixel can be changed, and images or 3D images with multiple focal points can be displayed. Japanese Patent Publication No. 2020-56880Japanese Patent Publication No. 2020-160296 This is a schematic diagram illustrating an example of the HUD system of the present invention.This is a schematic diagram illustrating another example of the HUD system of the present invention.This is a schematic diagram illustrating yet another example of the HUD system of the present invention.This is a schematic diagram showing one example of the configuration of a windshield glass having a P-polarized reflective film containing a layer made of cholesteric liquid crystal, used in the HUD system of the present invention.This is a schematic cross-sectional view showing one example of the configuration of a windshield glass having a P-polarizing reflective film made of a dielectric multilayer film, used in the HUD system of the present invention.Figure 5 is a schematic diagram showing the relationship between the refractive index of the P-polarized reflective film when the windshield glass is viewed from the front. In this invention, "~" is used to mean that the numerical values before and after it are included as the lower and upper limits. For example, when ε1 is between the numerical values α1 and β1, the range of ε1 is the range that includes the numerical values α1 and β1, and in mathematical notation, this is α1 ≤ ε1 ≤ β1. In this invention, the terms "angle" expressed as a specific numerical value such as 60°, and "parallel" and "perpendicular," unless otherwise specified, include an error range that is generally acceptab