Ergonomic head mounted display device and optical system

Patent metadata

Field	Value
Publication number	US-9348143-B2
Application number	US-201113335884-A
Country	US
Kind code	B2
Filing date	Dec 22, 2011
Priority date	Dec 24, 2010
Publication date	May 24, 2016
Grant date	May 24, 2016

Abstract

This invention concerns an ergonomic optical see-through head mounted display device with an eyeglass appearance. The see-through head-mounted display device consists of a transparent, freeform waveguide prism for viewing a displayed virtual image, a see-through compensation lens for enabling proper viewing of a real-world scene when combined together with the prism, and a miniature image display unit for supplying display content. The freeform waveguide prism, containing multiple freeform refractive and reflective surfaces, guides light originated from the miniature display unit toward a user's pupil and enables a user to view a magnified image of the displayed content. A see-through compensation lens, containing multiple freeform refractive surfaces, enables proper viewing of the surrounding environment, through the combined waveguide and lens. The waveguide prism and the see-through compensation lens are properly designed to ergonomically fit human heads enabling a wraparound design of a lightweight, compact, and see-through display system.

First claim

What is claimed is:

1. A freeform waveguide comprising at least three physical surfaces, at least one of which contains a plurality of reflective and refractive freeform optical surfaces disposed thereon, where an interior space defined by the physical surfaces is filled by a refractive medium having an index (n) greater than 1, where the plurality of reflective and refractive surfaces folds and extends an optical path length so that the waveguide can be fit to an eyeglass shape, which enables an image display unit to be placed at a side of a head, and which enables a wide see-through field of view of up to 90° relative to a straight ahead view in temple directions, and up to 60° in a nasal direction, and up to 60° above and below relative to a straight ahead view, where inner and outer surfaces thereof are designed, within a constraint of fitting an eyeglass form factor and a maximum thickness, so that the plurality of freeform reflective and refractive optical surfaces guide light towards a pupil of a user without distorting the image, the physical and optical surfaces comprising:
(a) a physical inner surface 115 , disposed towards the pupil of the user, where the physical inner surface is constrained to approximate a pre-designated curved surface for an eyeglass form factor, where the inner surface is configured to reflect an image to an eyeball of the user with a minimum amount of distortion;
(b) a physical outer surface 125 , disposed towards an external scene, where the physical outer surface is configured to reflect an image to the pupil of the user with a minimum amount of distortion, where the physical outer surface is within a maximum distance of the inner surface at all points, where the physical outer surface contains at least one refractive surface to allow light from the external scene to pass through the waveguide and reach the eyeball of the user;
(c) a physical edge surface 120 , which optionally contains a refractive surface for light from an image display unit to enter the waveguide;
(d) a refractive input surface 130 , disposed on one of the physical surfaces, that allows light from an image display unit to enter the waveguide;
(e) a refractive output surface 135 that allows light to exit the waveguide, disposed upon the physical inner surface, near the pupil of the user; and
(f) a plurality of three (3) or more freeform reflective surfaces, disposed upon the physical inner and outer surfaces, where each reflection is produced by either satisfying a Total Internal Reflection criterion, or by application of a semi-transparent, partially reflective coating to the surface of the waveguide; where these reflections are optimized to guide the light along the interior of the waveguide with a minimum of distortion, where a plurality of reflections extends the optical path length such that the waveguide enables a wide see-through field of view, and a size suitable to fitting to a human head;

whereupon light 140 from an image display unit 105 enters the waveguide, through the refractive input surface 130 ;
whereupon the light 140 follows a path 145 along the waveguide that comprises the plurality of reflections upon the plurality of reflective and refractive surfaces, from the refractive input surface 130 to the refractive output surface 135 , where each reflection is produced either by satisfying conditions of Total Internal Reflection, or by a semi-transparent coating applied to the surface;
whereupon light 140 passes through the refractive output surface 135 beyond which the user places the pupil 150 to view the image;
whereupon light 198 from the external scene is refracted through the physical outer surface 125 of the waveguide 100 and the physical inner surface 115 of the waveguide before reaching the pupil 150 , where the see-through field of view through the waveguide is up to 90° in the temple directions, up to 60° in the nasal direction, and up to 60° above and below a straight ahead view.

2. The waveguide of claim 1 , where the plurality of reflections extends the optical path length so that the waveguide has a width of greater than 25 mm, from pupil to temple.

3. The waveguide of claim 1 , where constraints upon the inner surface comprise:
(a) a first reference curved surface 230 , which approximates the shape of an average human head, where the inner surface is constrained to lie outside of the first reference curved surface;
(b) a second reference surface 240 , which limits an extent to which the waveguide projects out from a face of a user, where the inner surface is constrained to lie inside of the second reference surface;
(c) a maximum distance between the inner physical surface 115 and outer physical surface 225 ;
(d) an upper and lower bound on a width 244 of the waveguide from a pupil to a temple in a horizontal dimension, so that the waveguide reaches the side of the head and is sufficiently wide to yield a designated see-through field of view set by an upper extent 290 a thereof;
(e) an upper and lower bound on the width 246 of the waveguide from pupil to a nose in the horizontal dimension, so that the waveguide is sufficiently wide to yield the designated see-through field of view set by a lower extent 290 b thereof, but does not interfere with a nose bridge;
(f) a lower bound on a height of the waveguide from pupil in a vertical dimension, so that the waveguide is sufficiently wide to yield the designated see-through field of view set by upper 290 c or lower 290 d extents thereof; and
(g) a surface segment 215 a , where the inner surface is constrained to fit an eyeglass form factor, where the width of the surface segment is bounded by the upper 290 a and lower 290 b extent of the designated see-through field of view in a horizontal direction, and a height of the surface segment is bounded by the upper 290 c and lower 290 d extent of the see-through field of view in a vertical direction, projected on the inner surface, where a local radius of curvature of the surface segment is bounded by a range dependent on the eyeglass form factor;

whereupon the shape of the inner and outer waveguide surfaces are optimized to minimize optical distortion from an entry point of the waveguide to an exit point of the waveguide within these constraints.

4. The waveguide of claim 3 , where specific constraints comprise:
(a) the center of the first reference curved surface is defined by reference dimensions Y ref1 , the distance between a midline of the head and the center of the reference surface to a temple side of the head, Z ref1 , the distance between the pupil and the center of the reference surface from front to back of the head, and Y HIPD , where Y HIPD is the distance from the pupil to a midpoint of the head, where typically Y ref1 is in the range of 0 to 40 mm, Z ref1 is in the range of 30 to 90 mm, and Y HIPD is in the range of 20 to 40 mm; a radius of curvature of the first reference surface is in the range of 40 to 100 mm in the horizontal dimension;
(b) a position of the second reference surface is defined by reference dimension Z ref2 , the distance from the pupil to the reference surface, where Z ref2 is less than 40 mm;
(c) the maximum distance between the inner physical surface and outer physical surface is less than 40 mm;
(d) the upper bound on the width of the waveguide in the temple direction is 80 mm;
(e) the lower bound on the width of the waveguide in the temple direction is 15 mm;
(f) the upper bound on the width of the waveguide from pupil to nose is 40 mm; and
(g) the lower bound on the width of the waveguide from pupil to nose is 8 mm.

5. The waveguide of claim 3 , where the shape of the inner surface is constrained by approximating the appearance

Assignees

• Gao Chunyu
• Hua Hong
• Lin Yuxiang
• Magic Leap Inc

Inventors

• Gao Chunyu
• Hua Hong
• Lin Yuxiang

Classifications

• G02B27/283

  used for beam splitting or combining · CPC title

• G02B6/003

  Lens or lenticular sheet or layer · CPC title

• G02B27/0172 Primary

  characterised by optical features · CPC title

• G02B2027/0178

  Eyeglass type (eyeglass details G02C) · CPC title

• G02B5/30

  Polarising elements (light-modulating devices with active elements G02F1/00) · CPC title