# US 11,307,419 B2 · Display apparatus

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- Number: US 11,307,419 B2
- Document ID: US11307419B2
- Status: Granted
- Kind: B2
- Application number: 17/101,129
- Filed: 2020-11-23
- Published: 2021-03-11
- Granted: 2022-04-19
- Earliest claimed: 2016-12-28
- Assignees: Seiko Epson Corporation
- Applicants: Seiko Epson Corporation
- Inventors: Shohei Yoshida
- Web page: https://patentgrep.com/patent/US11307419B2

## CPC

- G02B 27/0172: {characterised by optical features}
- G02B 6/0031: {Reflecting element, sheet or layer}
- G02B 6/0055: {Reflecting element, sheet or layer}
- G02B 2027/0125: {Field-of-view increase by wavefront division}
- G02B 2027/0178: {Eyeglass type (eyeglass details G02C)}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

A display apparatus includes an image forming device and a light guide. The light guide includes an incident portion and an emission portion including a plurality of mirrors. In the light guide, the total reflection surface is disposed to be inclined with respect to a virtual plane perpendicular to a visual axis, and the mirrors are disposed to be inclined with respect to the total reflection surface. The mirror angle is set such that the light guide angle, the mirror angle, the light angle, the limit incidence angle, and the refractive index of the light guide satisfy the predetermined relationship.

## Claims

### Claim 1

A display apparatus comprising:
an image forming device that generates image light; and
a light guide that guides the image light, wherein
the light guide includes a first surface, a first mirror, and a second mirror,
the image forming device causes the image light to enter an inside of the light guide from the first surface,
the first mirror (i) causes a part of the image light guided inside the light guide to be reflected, and (ii) causes another part of the image light to be transmitted,
the second mirror (i) causes a part of the image light guided inside the light guide to be reflected, and (ii) causes another part of the image light to be transmitted,
the first mirror is disposed to be inclined with respect to the first surface,
the second mirror is disposed to be inclined with respect to the first surface,
in a plan view of the display apparatus, the first surface is disposed to be inclined with respect to a virtual plane perpendicular to a visual axis, and
when (i) an inclination angle of the first surface with respect to the virtual plane is defined as a light guide angle α, (ii) an inclination angle of each of the first mirror and the second mirror with respect to the first surface is defined as a mirror angle β, (iii) an angle between a light beam incident on an eye of an observer and the visual axis is defined as a light beam angle η, the light beam being a light beam that forms an angle of view among the image light, (iv) an incidence angle of the image light when the reflectance of the image light becomes 0 with respect to each of the first mirror and the second mirror is defined as a limit incidence angle θth, and (v) a refractive index of the light guide is n, the angle β of each of the first mirror and the second mirror is set so as to satisfy Expressions (1), (2), and (3) described below:
β1<β≤β2 (1)
β1=½×[sin−1(1/n)+sin−1(η+α)/n)] (2)
β2=1/3×[θth+sin−1(sin(η+α)/n))] (3)
in the plan view, the light guide angle α at which the first surface is inclined with respect to the virtual plane is larger than 0 degrees.

### Claim 2 (depends on 1)

The display apparatus according to claim 1, wherein expressions (4) and (5) below are satisfied:
10 degrees the light beam angle η≤15 degrees (4), and
1.4 the refractive index n≤1.8 (5).

### Claim 3 (depends on 1)

The display apparatus according to claim 1, wherein the light guide angle α is equal to or larger than 4 degrees.

### Claim 4 (depends on 1)

The display apparatus according to claim 1, wherein
the light guide includes a second surface, the second surface is opposite the first surface in the plan view, and
the light guide guides the image light by the first surface and the second surface.

### Claim 5 (depends on 1)

The display apparatus according to claim 1, wherein
the light guide includes an incident portion including a part of the first surface, and
the image forming device causes the image light to enter the inside of the light guide from a part of the first surface included in the incident portion.

### Claim 6 (depends on 5)

The display apparatus according to claim 5, wherein
the incident portion includes a mirror,
the mirror of the incident portion is disposed to be inclined with respect to each of the first surface and the virtual plane,
an inclination angle of the mirror of the incident portion with respect to the first surface is defined as an angle ω,
an inclination angle of the mirror of the incident portion with respect to the virtual plane is defined as an angle A, and
the inclination angle A of the mirror of the incident portion is set so as to satisfy an Expression A=ω+α.