# US 11,029,590 B2 · Low-profile beam splitter

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- Number: US 11,029,590 B2
- Document ID: US11029590B2
- Status: Granted
- Kind: B2
- Application number: 16/737,728
- Filed: 2020-01-08
- Published: 2020-07-02
- Granted: 2021-06-08
- Earliest claimed: 2017-03-21
- Assignees: Magic Leap, Inc.
- Applicants: Magic Leap, Inc.
- Inventors: Jahja Trisnadi; Pierre St. Hilaire; Hui-Chuan Cheng; Clinton Carlisle; Michael Anthony Klug; Kevin Richard Curtis
- Web page: https://patentgrep.com/patent/US11029590B2

## CPC

- G03B 21/2066: {Reflectors in illumination beam (in projection beam G03B21/28)}
- G02B 26/103: {having movable or deformable optical fibres, light guides or waveguides as scanning elements (light guides per se G02B6/00)}
- G02B 27/0103: {comprising holographic elements}
- G02B 27/017: {Head mounted}
- G02B 27/0944: {Diffractive optical elements, e.g. gratings, holograms (gratings per se G02B5/18; holograms used as optical elements per se G02B5/32)}
- G02B 27/1006: {for splitting or combining different wavelengths (G02B27/1086, G02B27/141 take precedence)}
- G02B 27/1033: {having a single light modulator for all colour channels}
- G03B 21/005: {Projectors using an electronic spatial light modulator but not peculiar thereto}
- G06V 40/19: Sensors therefor
- G02B 2027/0127: {comprising devices increasing the depth of field}
- G02B 2027/0134: {of stereoscopic type}
- G02B 2027/0138: {comprising image capture systems, e.g. camera}
- G02B 2027/0174: {holographic}
- G02B 2027/0185: {Displaying image at variable distance}
- G06V 20/20: in augmented reality scenes
- G03B: APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR (optical parts of such apparatus G02B; photosensitive materials or processes for photographic purposes G03C; apparatus for processing exposed photographic materials G03D)
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G06V: IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING

## Abstract

Examples of light projector systems for directing input light from a light source to a spatial light modulator are provided. For example, an optical device is disclosed which includes a first surface having a diffractive optical element, a second surface normal to the first surface, and a third surface arranged at an angle to the second surface. The third surface may be a beam splitting surface that is reflective to light of a first state and transmissive to light of a second state. The diffractive optical element may receive an input beam made up of light having the first state, and may convert the input beam into at least a first diffracted beam at a first diffraction angle such that the first diffracted beam is directed toward the second surface, is reflected by the second surface toward the third surface via total internal reflection, and is reflected by the third surface in a direction substantially parallel to the first surface.

## Claims

### Claim 1

An optical device comprising:
a first surface comprising a transmissive diffractive optical element;
a second surface normal to the first surface; and
a third surface arranged at an angle to the second surface, the third surface being reflective to light of a first state and transmissive to light of a second state,
wherein the transmissive diffractive optical element is configured to receive a collimated input beam that is normally incident on the first surface, the collimated input beam comprising light having the first state, and to convert the collimated input beam into at least a first diffracted beam at a first diffraction angle such that the first diffracted beam is directed toward the second surface, is reflected by the second surface toward the third surface via total internal reflection, and is reflected by the third surface in a direction substantially parallel to the first surface.

### Claim 2 (depends on 1)

The optical device of claim 1, wherein the first diffracted beam exits the optical device at the second surface, the optical device further comprising a spatial light modulator adjacent to the second surface to receive the first diffracted beam, the spatial light modulator configured to convert the first diffracted beam into a first modulated beam, the first modulated beam comprising light having the second state, and to direct the first modulated beam back toward the second surface.

### Claim 3 (depends on 2)

The optical device of claim 2, wherein the spatial light modulator is a liquid crystal on silicon (LCOS) spatial light modulator or a digital light processing (DLP) spatial light modulator.

### Claim 4 (depends on 2)

The optical device of claim 2, further comprising a fourth surface opposite the second surface, wherein the fourth surface is configured to receive and transmit the first modulated beam after it passes through the second surface, and wherein the fourth surface is curved.

### Claim 5 (depends on 1)

The optical device of claim 1, wherein the transmissive diffractive optical element is further configured to convert the collimated input beam into a second diffracted beam at a second diffraction angle such that the second diffracted beam is directed toward the third surface and is reflected by the third surface in a direction substantially parallel to the first surface.

### Claim 6 (depends on 5)

The optical device of claim 5, wherein the reflected first diffracted beam and the reflected second diffracted beam are received by a spatial light modulator, wherein the reflected first diffracted beam and the reflected second diffracted beam combine to illuminate the entire spatial light modulator.

### Claim 7 (depends on 1)

The optical device of claim 1, wherein the first, second, and third surfaces are planar.

### Claim 8 (depends on 1)

The optical device of claim 1, wherein the second surface is a curved surface.

### Claim 9 (depends on 1)

The optical device of claim 1, wherein the first, second, and third surfaces form a wedge.

### Claim 10 (depends on 9)

The optical device of claim 9, wherein the wedge comprises a refractive index of at least approximately 1.5.

### Claim 11 (depends on 1)

The optical device of claim 1, wherein the third surface comprises a polarizing beam splitting surface.

### Claim 12 (depends on 1)

The optical device of claim 1, wherein the angle of the third surface with respect to the second surface is less than 45 degrees.

### Claim 13 (depends on 12)

The optical device of claim 12, wherein the angle of the third surface with respect to the second surface is about 30 degrees.

### Claim 14 (depends on 1)

The optical device of claim 1, wherein the first diffraction angle is greater than 0 degrees.

### Claim 15 (depends on 14)

The optical device of claim 14, wherein the first diffraction angle is about 30 degrees.

### Claim 16 (depends on 1)

The optical device of claim 1, wherein the transmissive diffractive optical element comprises a plurality of diffractive features.

### Claim 17 (depends on 16)

The optical device of claim 16, wherein the first diffraction angle is based on a period of the plurality of diffractive features.

### Claim 18

An optical device comprising:
a first surface comprising a reflective diffractive optical element;
a second surface normal to the first surface; and
a third surface arranged at an angle to the second surface, the third surface being reflective to light of a first state and transmissive to light of a second state;
wherein the reflective diffractive optical element is configured to receive a diverging input beam, the diverging input beam comprising light having the first state, and to convert the diverging input beam into at least a first collimated and diffracted beam at a first diffraction angle such that the first collimated and diffracted beam is directed toward the second surface, is reflected by the second surface toward the third surface via total internal reflection, and is reflected by the third surface in a direction substantially parallel to the first surface.

### Claim 19 (depends on 18)

The optical device of claim 18, wherein the first collimated and diffracted beam exits the optical device at the second surface, the optical device further comprising a spatial light modulator adjacent to the second surface to receive the first collimated and diffracted beam, the spatial light modulator configured to convert the first collimated and diffracted beam into a first modulated beam, the first modulated beam comprising light having the second state, and to direct the first modulated beam back toward the second surface.

### Claim 20 (depends on 19)

The optical device of claim 19, wherein the spatial light modulator is a liquid crystal on silicon (LCOS) spatial light modulator or a digital light processing (DLP) spatial light modulator.

### Claim 21 (depends on 19)

The optical device of claim 19, further comprising a fourth surface opposite the second surface, wherein the fourth surface is configured to receive and transmit the first modulated beam after it passes through the second surface, and wherein the fourth surface is curved.

### Claim 22 (depends on 18)

The optical device of claim 18, wherein the reflective diffractive optical element is further configured to convert the diverging input beam into a second collimated and diffracted beam at a second diffraction angle such that the second collimated and diffracted beam is directed toward the third surface and is reflected by the third surface in the direction substantially parallel to the first surface.

### Claim 23 (depends on 22)

The optical device of claim 22, wherein the reflected first collimated and diffracted beam and the reflected second collimated and diffracted beam are received by a spatial light modulator, wherein the reflected first collimated and diffracted beam and the reflected second collimated and diffracted beam combine to illuminate the entire spatial light modulator.

### Claim 24 (depends on 18)

The optical device of claim 18, wherein the reflective diffractive optical element is configured to receive a plurality of angularly or laterally separated diverging input beams and to convert them into collimated and diffracted beams with a reduced amount of angular or lateral separation.

### Claim 25 (depends on 24)

The optical device of claim 24, further comprising a plurality of laterally separated light sources to output the plurality of angularly or laterally separated diverging input beams.

### Claim 26 (depends on 24)

The optical device of claim 24, wherein the reflective diffractive optical element is configured to receive a first input beam of the a plurality of angularly or laterally separated diverging input beams at a first angle and to convert the first input beam into a corresponding first collimated and diffracted beam directed toward the second surface along an optical path, and to receive a second input beam of the a plurality of angularly or laterally separated diverging input beams at a second angle and to convert the second input beam into a second collimated and diffracted beam directed toward the second surface along the optical path.

### Claim 27 (depends on 18)

The optical device of claim 18, wherein the first, second, and third surfaces are planar.

### Claim 28 (depends on 18)

The optical device of claim 18, wherein the second surface is a curved surface.

### Claim 29 (depends on 18)

The optical device of claim 18, wherein the first, second, and third surfaces form a wedge.

### Claim 30 (depends on 29)

The optical device of claim 29, wherein the wedge comprises a refractive index of at least approximately 1.5.

### Claim 31 (depends on 18)

The optical device of claim 18, wherein the third surface comprises a polarizing beam splitting surface.

### Claim 32 (depends on 18)

The optical device of claim 18, wherein the angle of the third surface with respect to the second surface is less than 45 degrees.

### Claim 33 (depends on 32)

The optical device of claim 32, wherein the angle of the third surface with respect to the second surface is about 30 degrees.

### Claim 34 (depends on 18)

The optical device of claim 18, wherein the first diffraction angle is greater than 0 degrees.

### Claim 35 (depends on 34)

The optical device of claim 34, wherein the first diffraction angle is about 30 degrees.

### Claim 36 (depends on 18)

The optical device of claim 18, wherein the first diffraction angle is based on a period of diffractive features of the reflective diffractive optical element.

### Claim 37 (depends on 18)

The optical device of claim 18, wherein the reflective diffractive optical element comprises a hologram.

### Claim 38

A head mounted display (HMD) configured to be worn on a head of a user, the HMD comprising:
a frame;
projection optics supported by the frame and configured to project an image to an eye of the user; and
a light projector system in optical communication with the projection optics, the light projector system configured to provide modulated light encoded with the image, the light projector system comprising:
a light source to emit an input beam;
an optical device comprising:
a first surface with a diffractive optical element,
a second surface normal to the first surface, and
a third surface arranged at an angle to the second surface, the third surface being reflective to light of a first state and transmissive to light of a second state,
wherein the diffractive optical element is configured to receive the input beam, the input beam comprising light having the first state, and to convert the input beam into at least a first diffracted beam at a first diffraction angle such that the first diffracted beam is directed toward the second surface, is reflected by the second surface toward the third surface via total internal reflection, and is reflected by the third surface in a direction substantially parallel to the first surface; and
a spatial light modulator configured to produce the modulated light using the input beam delivered to the spatial light modulator by the optical device.

### Claim 39 (depends on 38)

The HMD of claim 38, wherein the diffractive optical element comprises a transmissive diffractive optical element.

### Claim 40 (depends on 38)

The HMD of claim 38, wherein the diffractive optical element comprises a reflective diffractive optical element.

### Claim 41 (depends on 38)

The HMD of claim 38, wherein the diffractive optical element comprises a diffraction grating.

### Claim 42 (depends on 38)

The HMD of claim 38, wherein the diffractive optical element comprises a hologram.

### Claim 43 (depends on 38)

The HMD of claim 38, further comprising a collimator disposed between the optical device and the light source.

### Claim 44 (depends on 38)

The HMD of claim 38, wherein the projection optics comprise:
in-coupling optical elements; and
out-coupling optical elements,
wherein the in-coupling optical elements are configured to receive and in-couple the modulated light, and
wherein the out-coupling optical elements are configured to out-couple the in-coupled light towards the eye of the user.

### Claim 45 (depends on 44)

The HMD of claim 44, wherein the projection optics comprises a stack of waveguides.

### Claim 46 (depends on 45)

The HMD of claim 45, wherein each waveguide is configured to out-couple light with a different amount of divergence in comparison to one or more other waveguides of the stack of waveguides.

### Claim 47

An optical device comprising:
a first surface comprising a diffractive optical element;
a second surface normal to the first surface; and
a third surface arranged at an angle to the second surface, the third surface being reflective to light of a first state and transmissive to light of a second state,
wherein the diffractive optical element is configured to receive an input beam, the input beam comprising light having the first state, and to convert the input beam into at least a first diffracted beam at a first diffraction angle such that the first diffracted beam is directed toward the second surface, is reflected by the second surface toward the third surface via total internal reflection, and is reflected by the third surface in a direction substantially parallel to the first surface.

### Claim 48 (depends on 47)

The optical device of claim 47, wherein the diffractive optical element comprises a transmissive diffractive optical element.

### Claim 49 (depends on 47)

The optical device of claim 47, wherein the diffractive optical element comprises a reflective diffractive optical element.

### Claim 50 (depends on 47)

The optical device of claim 47, wherein the diffractive optical element comprises a diffraction grating.

### Claim 51 (depends on 47)

The optical device of claim 47, wherein the diffractive optical element comprises a hologram.

### Claim 52 (depends on 47)

The optical device of claim 47, wherein the input beam is collimated by a collimator separate from the optical device.

### Claim 53 (depends on 47)

The optical device of claim 47, wherein the diffractive optical element is configured to convert the input beam into a first collimated and diffracted beam.

### Claim 54 (depends on 47)

The optical device of claim 47, wherein the first and second states are a first polarization state and a second polarization state, respectively.