CROSS REFERENCE TO RELATED APPLICATIONS

This application is a national stage application under 35 U.S.C. 371 and claims the benefit of PCT Application No. PCT/JP2019/005472 having an international filing date of 15 Feb. 2019, which designated the United States, which PCT application claimed the benefit of Japanese Patent Application No. 2018-045061 filed 13 Mar. 2018, the entire disclosures of each of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to an optical device, an image display device including such an optical device, and a display apparatus including such an image display device, and more specifically, to a display apparatus used in a head-mounted display (HMD).

BACKGROUND ART

In recent years, the development of a head-mounted display (HMD), which displays an image from an image forming device on an optical device disposed in front of observer's eyes, has been intensively promoted. Various types of head-mounted displays have been studied, but for the head-mounted displays, there is a strong need for a wider angle of view of a displayed image so as to provide a more realistic image. To address such a demand, a head-mounted display including three deflecting means disposed on a light guide plate constituting an optical device is well known, for example, from U.S. Patent Application Laid-Open No. 2006/0132914A1 or U.S. Patent Application Laid-Open No. 2014/0330966A1.

Further, Japanese Patent Application Laid Open No. 2009-133998 discloses an image display device including

(A) an image forming device including a plurality of pixels arranged in a two-dimensional matrix,

(B) a collimating optical system for collimating light emitted from the pixels of the image forming device to be parallel light, and

(C) an optical device, in which the light collimated to be a plurality of parallel light beams having different traveling orientations in the collimating optical system is incident, guided, and emitted, the optical device including(a) a light guide plate, in which incident light propagates by total reflection, and from which the incident light is emitted,(b) a first diffraction grating member disposed on the light guide plate and including a reflective volume hologram diffraction grating that diffracts and reflects the light incident on the light guide plate such that the light incident on the light guide plate is totally reflected inside the light guide plate, and(c) a second diffraction grating member disposed on the light guide plate and including a reflective volume hologram diffraction grating that diffracts and reflects the light propagated by total reflection inside of the light guide plate and emits the light from the light guide plate, in which

assuming that the center of the first diffraction grating member is an origin, a normal of the first diffraction grating member that passes through the origin or a normal with a direction toward the collimating optical system side as a positive direction is an Xiaxis, an axis line of the light guide plate that passes through the origin, is orthogonal to the Xiaxis, and has a direction toward the second diffraction grating member side as a positive direction is a Yiaxis,

central light emitted from the pixel at the center of the image forming device and passing through the center of the collimating optical system is optically parallel to the XiYiplane and intersects with the XiZiplane at a sharp angle.

CITATION LIST

Patent Literature

Patent Literature 1: U.S. Patent Application Laid-Open No. 2006/0132914A1

Patent Literature 2: U.S. Patent Application Laid-Open No. 2014/0330966A1

Patent Literature 3: Japanese Patent Application Laid Open No. 2009-133998

DISCLOSURE OF INVENTION

Technical Problem

However, in the head-mounted displays disclosed in the above two U.S. Patent Publications, light emitted from the center point of the image forming region of the image forming device is perpendicularly incident on the deflecting means, but the head-mounted displays fail to cope with a request for further widening the angle of view of a display image. Further, the image display device disclosed in Japanese Patent Application Laid Open No. 2009-133998 includes only two diffraction grating members of the first diffraction grating member and the second diffraction grating member, and thus a display image region in the light guide plate can be enlarged only in one direction propagating from the first diffraction grating to the second diffraction grating. However, providing three diffraction grating members can enlarge the display image region in the light guide plate in two directions.

Therefore, it is an object of the present disclosure to provide an optical device having a configuration or a structure that can further widen the angle of view of a display image, an image display device including such an optical device, and a display apparatus including such an image display device.

Solution to Problem

An optical device according to the present disclosure to achieve the above-mentioned object is an optical device, on which light emitted from an image forming device is incident, in which the light is guided, and from which the light is emitted, the optical device including: a light guide plate; a first deflecting unit; and a second deflecting unit. The first deflecting unit includes a first A deflecting member, a first B deflecting member, and a first C deflecting member. The second deflecting unit includes a second A deflecting member, a second B deflecting member, and a second C deflecting member. Part of the light emitted from the image forming device enters the first A deflecting member. The light incident on the first A deflecting member is deflected by the first A deflecting member, enters the first B deflecting member by total reflection inside of the light guide plate, is deflected by the first B deflecting member, enters the first C deflecting member by total reflection inside of the light guide plate, is deflected by the first C deflecting member, and is emitted toward a pupil of an observer. At least remaining part of the light emitted from the image forming device enters the second A deflecting member. The light incident on the second A deflecting member is deflected by the second A deflecting member, enters the second B deflecting member by total reflection inside of the light guide plate, is deflected by the second B deflecting member, enters the second C deflecting member by total reflection inside of the light guide plate, is deflected by the second C deflecting member, and is emitted toward the pupil of the observer. Assuming that a direction obtained when a propagation direction of the light deflected by the first A deflecting member is orthogonally projected on the light guide plate is a first direction, and that a direction obtained when a propagation direction of the light deflected by the second A deflecting member is orthogonally projected on the light guide plate is a second direction, the first direction is opposite to the second direction. Note that the term “total reflection” means total internal reflection or total reflection inside of the light guide plate.

An image display device according to the present disclosure to achieve the above-mentioned object is an image display device including: an image forming device; and an optical device, on which light emitted from the image forming device is incident, in which the light is guided, and from which the light is emitted, the optical device including the optical device according to the present disclosure.

A display apparatus according to the present disclosure to achieve the above-mentioned object is a display apparatus including: a frame to be mounted to a head of an observer; and an image display device attached to the frame, the image display device including an image forming device, and an optical device, on which light emitted from the image forming device is incident, in which the light is guided, and from which the light is emitted, the optical device including the optical device according to the present disclosure.

