Image display device having maximum emission angle of first image light smaller than maximum viewing angle of virtual image

Patent metadata

Field	Value
Publication number	US-10739601-B2
Application number	US-201615557064-A
Country	US
Kind code	B2
Filing date	Feb 1, 2016
Priority date	Mar 9, 2015
Publication date	Aug 11, 2020
Grant date	Aug 11, 2020

Abstract

The image display device includes an image generating unit that emits first image light, a pupil expanding element that expands a diameter of a light flux included in the first image light from the image generating unit to obtain second image light, a first light condensing optical system that condenses the second image light and forms an intermediate image, and a second light condensing optical system that condenses light from the intermediate image and generates a virtual image on eye of a viewer, in a plane including at least the image generating unit, the pupil expanding element, and the eye of the viewer, a maximum emission angle of the first image light is smaller than a maximum viewing angle of the virtual image, and the diameter of the light flux included in the second image light is greater than that of a light flux included in the virtual image.

First claim

The invention claimed is:

1. An image display device comprising:
an image generating unit that emits first image light;
a pupil expanding element that expands a diameter of a light flux included in the first image light from the image generating unit to obtain second image light;
a first light condensing optical system that condenses the second image light and forms an intermediate image; and
a second light condensing optical system that condenses light from the intermediate image and generates a virtual image on an eye of a viewer,
wherein, in a plane including at least the image generating unit, the pupil expanding element, and the eye of the viewer,
a maximum emission angle of the first image light is smaller than a maximum viewing angle of the virtual image, and
the diameter of the light flux included in the second image light is greater than that of a light flux included in the virtual image.

2. The image display device according to claim 1 ,
wherein an angular magnification, which is defined as the maximum viewing angle of the virtual image with respect to the maximum emission angle of the first image light, is 1 or more and 2.5 or less.

3. The image display device according to claim 2 ,
wherein the angular magnification is 1.1 or more and 1.7 or less.

4. The image display device according to claim 2 ,
wherein a magnification ratio of the pupil expanding element is such that a diameter of the light flux included in the second image light is equal to or greater than a size obtained by multiplying a diameter of the light flux included in the virtual image by the angular magnification.

5. The image display device according to claim 1 ,
wherein an angular magnification, defined as a substantial focal distance of the first light condensing optical system is divided by a substantial focal distance of the second light condensing optical system, is 1 or more and 2.5 or less.

6. The image display device according to claim 5 ,
wherein the angular magnification is 1.1 or more and 1.7 or less.

7. The image display device according to claim 5 ,
wherein a magnification ratio of the pupil expanding element is such that a diameter of the light flux included in the second image light is equal to or greater than a size obtained by multiplying a diameter of the light flux included in the virtual image by the angular magnification.

8. The image display device according to claim 1 ,
wherein the image generating unit is a light scanning device which scans the light emitted from a light source unit to obtain the first image light.

9. The image display device according to claim 1 ,
wherein the image generating unit includes an electro-optical device and a collimator lens.

10. The image display device according to claim 1 ,
wherein the pupil expanding element is an optical element in which a plurality of light guiding materials are bonded to each other through a half mirror layer.

11. The image display device according to claim 1 ,
wherein the pupil expanding element is an optical element including a diffraction element.

12. The image display device according to claim 1 ,
wherein the first light condensing optical system is an optical system having at least positive power and negative power, and totally has the positive power.

13. The image display device according to claim 1 ,
wherein the second light condensing optical system is a concave mirror having the positive power in a plane including at least the image generating unit, the pupil expanding element, and the eye of the viewer.

14. The image display device according to claim 1 ,
wherein the second light condensing optical system is a reflective type hologram having the positive power in the plane including at least the image generating unit, the pupil expanding element, and the eye of the viewer.

15. The image display device according to claim 1 , wherein
the pupil expanding element has a first surface and a second surface that is a surface opposite to the first surface,
the first surface is a surface in which the first image light enters,
the second surface is a surface that emits the second image light.

16. The image display device according to claim 15 ,
wherein an incident angle of the first image light to the first surface is the same as an emission angle of the second image light from the second surface.

Assignees

• Seiko Epson Corp

Inventors

• Yonekubo Masatoshi
• Yokoyama Osamu
• Takeda Takashi
• Ide Mitsutaka
• Ishida Daisuke

Classifications

• G02B5/32 Primary

  Holograms used as optical elements · CPC title

• G02B5/1871

  Transmissive phase gratings · CPC title

• G02B5/1814

  structurally combined with one or more further optical elements, e.g. lenses, mirrors, prisms or other diffraction gratings (G02B5/189 takes precedence) · CPC title

• G02B2027/0107

  with optical power · CPC title

• G02B27/0081

  with means for altering, e.g. enlarging, the entrance or exit pupil · CPC title