US-12619083-B2 - Virtual-image display device and optical unit

US12619083B2US 12619083 B2US12619083 B2US 12619083B2US-12619083-B2

Abstract

A virtual-image display device includes a display panel configured to output image light, a projection optical system configured to collimate the image light from the display panel, and a light-guiding member including a light-guiding plate configured to guide the image light, an input diffraction optical element configured to cause the image light to enter the light-guiding plate, and an output diffraction optical element configured to cause the image light to be outputted from the light-guiding plate. A diffraction region of the input diffraction optical element covers an incident region of the image light at the light-guiding member, and the diffraction region is set at a region in which the image light diffracted at the input diffraction optical element is reflected on an opposing surface of the light-guiding plate, and enters an outside of the input diffraction optical element.

Inventors

Takashi Tajiri

Assignees

SEIKO EPSON CORPORATION

Dates

Publication Date: 20260505
Application Date: 20250116
Priority Date: 20240123

Claims (10)

1 . A virtual-image display device comprising: a display panel configured to output image light; a projection optical system configured to collimate the image light from the display panel; and a light-guiding member including a light-guiding plate configured to guide the image light, an input diffraction optical element configured to cause the image light to enter the light-guiding plate, and an output diffraction optical element configured to cause the image light to be outputted from the light-guiding plate, wherein a diffraction region of the input diffraction optical element covers an incident region of the image light at the light-guiding member, and the diffraction region is set in a region in which the image light diffracted at the input diffraction optical element is reflected on an opposing surface of the light-guiding plate, and enters an outside of the input diffraction optical element, wherein the region in which the image light enters the outside of the input diffraction optical element is defined by an external incidence structure in which a size of the incident region is set such that a size of the diffraction region is less than or equal to a width until a light beam turns back in a light-guiding direction, the width until the light beam turns back being defined as two times a thickness of the light-guiding plate multiplied by a tangent value of a critical angle of the light beam.
2 . The virtual-image display device according to claim 1 , further comprising: a region restricting member configured to restrict the incident region.
3 . The virtual-image display device according to claim 1 , wherein the diffraction region is configured such that an expansion size is small at a light guiding side relative to the incident region.
4 . The virtual-image display device according to claim 1 , wherein the diffraction region and the incident region are substantially equal.
5 . The virtual-image display device according to claim 1 , wherein the input diffraction optical element is disposed at a position of an exit pupil of the projection optical system.
6 . The virtual-image display device according to claim 1 , wherein a cover member is provided either between the projection optical system and the light-guiding member or at an outside relative to the light-guiding member.
7 . The virtual-image display device according to claim 1 , further comprising: a first display panel serving as a display panel configured to output first image light of the image light; a second display panel configured to output second image light having a wavelength region differing from the first image light; a third display panel configured to output third image light having a wavelength region differing from the first image light and the second image light; and a cross dichroic prism configured to synthesize the first image light, the second image light, and the third image light.
8 . The virtual-image display device according to claim 1 , further comprising: a first light-guiding member serving as the light-guiding member; and a second light-guiding member configured to diffract the image light having a wavelength region differing from the first light-guiding member.
9 . The virtual-image display device according to claim 1 , wherein the diffraction region has a circular shape.
10 . An optical unit comprising: a display panel configured to output image light; a projection optical system configured to collimate the image light from the display panel; and a light-guiding member including a light-guiding plate configured to guide the image light, an input diffraction optical element configured to cause the image light to enter the light-guiding plate, and an output diffraction optical element configured to cause the image light to be outputted from the light-guiding plate, wherein a diffraction region of the input diffraction optical element covers an incident region of the image light at the light-guiding member, and the diffraction region is set at a region in which the image light diffracted at the input diffraction optical element is reflected on an opposing surface of the light-guiding plate, and enters an outside of the input diffraction optical element, wherein the region in which the image light enters the outside of the input diffraction optical element is defined by an external incidence structure in which a size of the incident region is set such that a size of the diffraction region is less than or equal to a width until a light beam turns back in a light-guiding direction, the width until the light beam turns back being defined as two times a thickness of the light-guiding plate multiplied by a tangent value of a critical angle of the light beam.

Description

The present application is based on, and claims priority from JP Application Serial Number 2024-007999, filed Jan. 23, 2024, the disclosure of which is hereby incorporated by reference herein in its entirety. BACKGROUND 1. Technical Field The present disclosure relates to a virtual-image display device and an optical unit that make it possible to observe a virtual image. 2. Related Art There is an image display device that makes it possible to observe a virtual image (JP-A-2022-13157). This image display device includes an image projection module, an image-light duplicating unit, and a light-guiding plate including a light input unit and a light output unit. In order to display an image having uniform brightness, the device in JP-A-2022-13157 uses the image-light duplicating unit to uniformly duplicate an image light entering from the image projection module, and then, causes the light to enter the light input unit. In a case of the device in JP-A-2022-13157, the size of the light input unit increases. This leads to a possibility that light beam diffracted at an input grating of the light input unit is reflected at the opposing surface side, and enters the input grating again. In other words, the device in JP-A-2022-13157 has a problem in which the light beam goes outside of the light-guiding plate again, which deteriorates light utilization efficiency. SUMMARY A virtual-image display device or an optical unit according to one aspect of the present disclosure includes a display panel configured to output image light, a projection optical system configured to collimate the image light from the display panel, and a light-guiding member including a light-guiding plate configured to guide the image light, an input diffraction optical element configured to cause the image light to enter the light-guiding plate, and an output diffraction optical element configured to cause the image light to be outputted from the light-guiding plate, in which a diffraction region of the input diffraction optical element covers an incident region of the image light at the light-guiding member, and the diffraction region is set at a region in which the image light diffracted at the input diffraction optical element is reflected on an opposing surface of the light-guiding plate, and enters an outside of the input diffraction optical element. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view illustrating a state where an HMD according to a first embodiment is mounted. FIG. 2 is a side view illustrating the arrangement of an optical system and the like that constitute a virtual-image display device. FIG. 3 is a plan view illustrating the arrangement of the optical system and the like that constitute the virtual-image display device. FIG. 4 is a conceptual diagram mainly illustrating the optical system of a first display driving unit. FIG. 5 is a rear view mainly illustrating a first light-guiding optical system. FIG. 6 is a partially enlarged rear view of an input diffraction optical element. FIG. 7 is a diagram illustrating the size of the input diffraction optical element or the like. FIG. 8 is a conceptual diagram illustrating an optical system according to a second embodiment. FIG. 9 is a diagram illustrating a size of the input diffraction optical element or the like. FIG. 10 is a conceptual diagram illustrating an optical system according to a third embodiment. FIG. 11 is a conceptual diagram illustrating a modification example of an optical system according to the third embodiment. FIG. 12 is a conceptual diagram illustrating an optical system according to a fourth embodiment. FIG. 13 is a diagram illustrating a modification example of the arrangement of a diffraction region and an incident region. FIG. 14 is a conceptual diagram illustrating a modification example of an optical system that constitutes a virtual-image display device. FIG. 15 is a conceptual diagram illustrating another modification example of an optical system that constitutes a virtual-image display device. DESCRIPTION OF EMBODIMENTS First Embodiment Below, a first embodiment of a virtual-image display device according to the present disclosure will be described with reference to FIGS. 1 to 3 and the like. FIG. 1 is a diagram illustrating a state where a head-mounted display device (hereinafter, also referred to as a head-mounted display or an HMD) 200 is mounted. The HMD 200 causes an observer or a wearer US wearing the HMD 200 to recognize an image as a virtual image. In FIG. 1 and the like, X, Y, and Z represent a rectangular coordinate system. The +X direction corresponds to a lateral direction in which both eyes EY of the observer or the wearer US, who wears the HMD 200, are arranged. The +Y direction corresponds to the upper direction perpendicular to the lateral direction from the viewpoint of the wearer US in which both of the eyes EY are arranged. The +Z direction corresponds to the forward direction or the front side direction from the viewpoin