# US 2017/0285348 A1 · Light homogenization

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 2017/0285348 A1
- Document ID: US20170285348A1
- Status: Published application
- Kind: A1
- Application number: 15/479,252
- Filed: 2017-04-04
- Published: 2017-10-05
- Earliest claimed: 2016-04-04
- Assignees: Akonia Holographics LLC
- Applicants: Akonia Holographics, LLC
- Inventors: Mark R. Ayres; Adam Urness; Kenneth E. Anderson; Friso Schlottau
- Web page: https://patentgrep.com/patent/US20170285348A1

## CPC

- G02B 27/0172: {characterised by optical features}
- G02B 5/18: Diffraction gratings {(holographic optical elements G02B5/32, G03H; integrally combined with optical fibres G02B6/02057; for coupling light guides G02B6/34; integrally combined with optical integrated light guides G02B6/12; grating systems G02B27/44)}
- G02B 6/0016: {Grooves, prisms, gratings, scattering particles or rough surfaces}
- G02B 6/0031: {Reflecting element, sheet or layer}
- G02B 6/0055: {Reflecting element, sheet or layer}
- G02B 27/14: operating by reflection only
- G02B 27/144: {using partially transparent surfaces without spectral selectivity (G02B27/147 takes precedence)}
- G03H 1/02: Details {of features involved during the holographic process; Replication of holograms without interference recording}
- G03H 1/0402: {Recording geometries or arrangements (G03H1/0443, G03H1/0476, G03H1/16 take precedence)}
- G02B 5/32: Holograms used as optical elements
- G02B 2027/0118: {comprising devices for improving the contrast of the display / brillance control visibility}
- G02B 2027/0147: {comprising a device modifying the resolution of the displayed image}
- G02B 2027/0174: {holographic}
- G02B 2027/0178: {Eyeglass type (eyeglass details G02C)}
- G03H 2001/0216: {Optical components (G03H2001/0224, G03H1/0256 take precedence; corresponding details, see subgroups of G03H2223/00)}
- G03H 2001/026: {Recording materials or recording processes (G03H2226/11 takes precedence; corresponding details, see subgroups of G03H2260/00)}
- G03H 2001/0441: {Formation of interference pattern, not otherwise provided for}
- G03H 2222/45: Interference beam at recording stage, i.e. following combination of object and reference beams
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G03H: HOLOGRAPHIC PROCESSES OR APPARATUS (holograms, e.g. point holograms, used as ordinary optical elements G02B5/32; producing stereoscopic or other three-dimensional effects G02B30/00; diffraction-grating systems G02B27/44; systems using moiré fringes G02B27/60; optical logic elements G02F3/00; stereo-photography G03B35/00; photosensitive materials or processes for photographic purposes G03C; {stereo-photographic or similar processes G03C9/00}; apparatus for processing exposed photographic materials G03D; analogue computers performing mathematical operations with the aid of optical elements G06E3/00; authentication by radiation, of concealed information carried by holograms or diffraction gratings G06K19/16; holographic storage G11B7/0065, G11C13/04; {stereoscopic or other three dimensional effects in television systems H04N13/00})

## Abstract

An optical reflective device for homogenizing light including a waveguide having a first and second waveguide surface and a partially reflective element is disclosed. The partially reflective element may be located between the first waveguide surface and the second waveguide surface. The partially reflective element may have a reflective axis parallel to a waveguide surface normal. The partially reflective element may be configured to reflect light incident on the partially reflective element at a first reflectivity for a first set of incidence angles and reflect light incident on the partially reflective element at a second reflectivity for a second set of incident angles.

## Claims

### Claim 1

A device for homogenizing light, comprising:
a waveguide having a first waveguide surface and a second waveguide surface parallel to the first waveguide surface; and
a partially reflective element located between the first waveguide surface and the second waveguide surface, the partially reflective element having a reflective axis parallel to a waveguide surface normal.

### Claim 2 (depends on 1)

The device of claim 1, wherein the partially reflective element is configured to reflect light incident on the partially reflective element at a first reflectivity for a first set of incidence angles and to reflect light incident on the partially reflective element at a second reflectivity for a second set of incident angles, the first reflectivity being different from the second reflectivity.

### Claim 3 (depends on 1)

The device of claim 1, wherein:
the waveguide comprises a first layer having parallel plane surfaces and a second layer having parallel plane surfaces;
the device further comprising an interior plane surface of the parallel plane surfaces of the first layer abuts an interior plane surface of the parallel plane surfaces of the second layer;
wherein the first waveguide surface is a plane surface of the first layer opposite the interior plane surface of the parallel plane surfaces of the first layer; and
the second waveguide surface is a plane surface of the second layer opposite the interior plane surface of the parallel plane surfaces of the second layer.

### Claim 4 (depends on 3)

The device of claim 3, wherein:
the first layer and the second layer have matched indices of refraction; and
the partially reflective element is a partially reflective element disposed on one or both of the interior plane surface of the parallel plane surfaces of the first layer or the interior plane surface of the parallel plane surfaces of the second layer.

### Claim 5 (depends on 3)

The device of claim 3, wherein:
the first layer has an index of refraction different from the second layer; and
the partially reflective element is a boundary condition associated with the first layer and the second layer.

### Claim 6 (depends on 3)

The device of claim 3, further comprising:
a light coupling device disposed within at least one of the first layer or the second layer of the waveguide, the light coupling device comprising,
a grating medium;
a first grating structure within the grating medium, the first grating structure being configured to reflect light of a wavelength about a first reflective axis offset from the waveguide surface normal at a first incidence angle; and
a second grating structure within the grating medium, the second grating structure being configured to reflect light of the wavelength about a second reflective axis offset from the waveguide surface normal at a second incidence angle different from the first incidence angle.

### Claim 7 (depends on 6)

The device of claim 6, wherein at least one of the first grating structure or the second grating structure comprises a hologram.

### Claim 8 (depends on 6)

The device of claim 6, wherein at least one of the first grating structure or the second grating structure comprises a non-holographic diffractive optical element.

### Claim 9 (depends on 6)

The device of claim 6, wherein the partially reflective element at least partially overlaps the grating medium in a direction orthogonal to a plane of the first waveguide surface.

### Claim 10 (depends on 1)

The device of claim 1, wherein the partially reflective element is configured to reflect between 10% and 90% of light incident on the partially reflective element.

### Claim 11 (depends on 1)

The device of claim 1, wherein the partially reflective element comprises a partially reflective plate disposed within the waveguide, the partially reflective plate comprising a plate surface parallel to the first waveguide surface.

### Claim 12 (depends on 1)

The device of claim 1, wherein the partially reflective element comprises a first partially reflective plate and a second partially reflective plate disposed within the waveguide, each of the first and second partially reflective plates comprising a plate surface parallel to the first waveguide surface, each of the first and second partially reflective plates being configured to reflect between 10% and 90% of light incident on a respective one of the first and second partially reflective plates.

### Claim 13 (depends on 1)

The device of claim 1, wherein the partially reflective element comprises:
a grating medium;
a first grating structure within the grating medium, the first grating structure being configured to reflect light of a wavelength about a first reflective axis parallel to the waveguide surface normal at a first incidence angle; and
a second grating structure within the grating medium, the second grating structure being configured to reflect light of the wavelength about a second reflective axis parallel to the waveguide surface normal waveguide at a second incidence angle different from the first incidence angle.

### Claim 14 (depends on 13)

The device of claim 13, wherein at least one of the first grating structure or the second grating structure comprises a hologram.

### Claim 15 (depends on 13)

The device of claim 13, wherein the grating medium is configured to reflect between 10% and 90% of the light of the wavelength incident on the grating medium.

### Claim 16 (depends on 13)

The device of claim 13, wherein each of the first incidence angle and the second incidence angle has a value between 65° and 77° with respect to the waveguide surface normal.

### Claim 17 (depends on 13)

The device of claim 13, wherein the grating medium is configured to allow a majority of light of the wavelength to pass through the grating medium at third incidence angle different from the first incidence angle and the second incidence angle.

### Claim 18

A head mounted display device, comprising:
a light source for providing image-bearing light; and
an optical lens comprising,
a light input section of the optical lens for receiving the image-bearing light;
a waveguide disposed within the optical lens operatively coupled to the light input section, the waveguide having a first waveguide surface and a second waveguide surface parallel to the first waveguide surface;
a partially reflective element located between the first waveguide surface and the second waveguide surface, the partially reflective element having a reflective axis parallel to the waveguide surface normal; and
a light coupling device operatively coupled to the waveguide medium.

### Claim 19

A method for homogenizing light, comprising:
propagating light in a total internal reflection (TIR) waveguide having a first waveguide surface and a second waveguide surface parallel to the first waveguide surface; and
reflecting a portion of the light via a partially reflective element located between the first waveguide surface and the second waveguide surface, the partially reflective element having a reflective axis parallel to a waveguide surface normal.