Light projector
A light projector for an augmented reality headset is disclosed. First and second optical arrangements receive light from a polarising beam splitter so that light is reflected, focused and directed back towards the polarising beam splitter from each optical arrangement. The first and second optical arrangements comprise first and second mirrors and first and second quarter-wave plates. The polarising beam splitter receives and combines light from the first and second optical arrangements so that the combined light, which is unpolarised, is provided to an exit pupil. The first and second optical arrangements are angled relative to one another so that the image from the first optical arrangement is aligned with the image from the second optical arrangement.
1 . A light projector for an augmented reality headset, comprising:
an image generator configured to provide image-bearing unpolarised light of an image;
a polarising beam splitter configured to:
receive the image-bearing unpolarised light of the image from the image generator at a first side of the polarising beam splitter; and
split the image-bearing unpolarised light of the image into a first path and a second path by reflecting first linearly polarised light of a first orientation that is split from the image-bearing unpolarised light of the image into the first path and transmitting second linearly polarised light of a second orientation that is split from the image-bearing unpolarised light of the image into the second path, wherein the first orientation is orthogonal to the second orientation, wherein each of the first linearly polarised light in the first path and the second linearly polarised light in the second path remains image-bearing;
a first optical arrangement including a first mirror and a first quarter-wave plate that is disposed between the first mirror and a second side the polarising beam splitter that is opposite the first side; and
a second optical arrangement including a second mirror and a second quarter-wave plate that is disposed between the second mirror and a third side the polarising beam splitter,
wherein the first quarter-wave plate of the first optical arrangement is configured to receive the first linearly polarised light of the first orientation that is in the first path from the polarising beam splitter and output first-hand polarised first light to the first mirror that reflects the first-hand polarised first light back to the first quarter-wave plate as second-hand polarised first light without the first mirror outputting light of an additional image, and the first quarter-wave plate transforms the second-hand polarised first light into first linearly polarised light of the second orientation that is output by the first quarter-wave plate to the second side of the polarising beam splitter;
wherein the second quarter-wave plate of the second optical arrangement is configured to receive the second linearly polarised light of the second orientation that is in the second path from the polarising beam splitter and output second-hand polarised second light to the second mirror that reflects the second-hand polarised second light back to the second quarter-wave plate as first-hand polarised second light without the second mirror outputting light of an additional image, and the second quarter-wave plate transforms the first-hand polarised second light into second linearly polarised light of the first orientation that is output by the second quarter-wave plate to the third side of the polarising beam splitter,
wherein the polarising beam splitter is configured to receive and combine the first linearly polarised light of the second orientation from the first optical arrangement and the second linearly polarised light of the first orientation from the second optical arrangement so that the combined light, which is unpolarised, is provided to an exit pupil at a fourth side of the polarising beam splitter that is opposite third side, and
wherein the first optical arrangement and the second optical arrangement are angled relative to one another so that the image from the image-bearing light in the first path is aligned with the image from the image-bearing light in the second path.
2 . The light projector of claim 1 , wherein:
the first mirror and the second mirror are configured to focus light.
3 . The light projector of claim 2 , wherein:
the first mirror and the second mirror are a first concave mirror and a second concave mirror, respectively.
4 . The light projector of claim 3 , wherein each of the first concave mirror and the second concave mirror is a spherical mirror.
5 . The light projector of claim 1 , wherein:
the first optical arrangement and the second optical arrangement further comprise a first lens and a second lens respectively for focusing or collimating the light of the first path and second path respectively.
6 . The light projector of claim 1 , wherein the image generator comprises a LED array.
7 . The light projector of claim 6 , wherein the image generator comprises a micro LED array.
8 . The light projector of claim 1 , wherein the polarising beam splitter is a rectangular cuboid comprising a top face corresponding to the fourth side, a bottom face corresponding to the third side, and four side faces including the first side and the second side.
9 . A light projector for an augmented reality headset, comprising:
an image generator configured to provide image-bearing unpolarised light of an image;
a beam splitter configured to receive the image-bearing unpolarised light of the image from the image generator at a first side of the beam splitter and to split it into a first path comprising first image-bearing light of a first orientation from the image with unpolarised light and a second path comprising second image-bearing light of a second orientation from the image with unpolarised light;
a first optical arrangement including a first mirror and a first quarter-wave plate that is disposed between the first mirror and a second side of the beam splitter that is opposite the first side; and
a second optical arrangement including a second mirror and a second quarter-wave plate that is disposed between the second mirror and a third side of the beam splitter,
wherein the first quarter-wave plate of the first optical arrangement is configured to receive the first image-bearing light of the first orientation that is in the first path from the beam splitter and output first-hand polarised first light to the first mirror that reflects the first-hand polarised first light back to the first quarter-wave plate as second-hand polarised first light without the first mirror outputting light of an additional image, and the first quarter-wave plate transforms the second-hand polarised first light into first image-bearing light of the second orientation that is output by the first quarter-wave plate to the second side of the beam splitter;
wherein the second quarter-wave plate of the second optical arrangement is configured to receive the second image-bearing light of the second orientation that is in the second path from the beam splitter and output second-hand polarised second light to the second mirror that reflects the second-hand polarised second light back to the second quarter-wave plate as first-hand polarised second light without the second mirror outputting light of an additional image, and the second quarter-wave plate transforms the first-hand polarised second light into second image-bearing light of the first orientation that is output by the second quarter-wave plate to the third side of the beam splitter; and
wherein the beam splitter is configured to receive and combine the first image-bearing light of the second orientation from the first optical arrangement and the second image-bearing light of the first orientation from the second optical arrangement so that the combined image-bearing light, which is unpolarised, is provided to an exit pupil at a fourth side of the beam splitter that is opposite third side, and
wherein the first optical arrangement and the second optical arrangement are angled relative to one another so that the image from the first path is aligned with the image from the second path.
10 . The light projector of claim 9 , wherein:
the first mirror and the second mirror are configured to focus light.
11 . The light projector of claim 10 , wherein:
the first mirror and the second mirror are a first concave mirror and a second concave mirror, respectively.
12 . The light projector of claim 11 , wherein each of the first concave mirror and the second concave mirror is a spherical mirror.
13 . The light projector of claim 9 , wherein:
the first optical arrangement and the second optical arrangement further comprise a first lens and a second lens respectively for focusing or collimating the light of the first path and second path respectively.
14 . The light projector of claim 9 , wherein the image generator comprises a LED array.
15 . The light projector of claim 14 , wherein the image generator comprises a micro LED array.
16 . The light projector of claim 9 , wherein the beam splitter is a rectangular cuboid comprising a top face corresponding to the fourth side, a bottom face corresponding to the third side, and four side faces including the first side and the second side.
17 . A method of assembling a light projector for an augmented reality headset, comprising:
providing an image generator configured to provide image-bearing unpolarised light of an image;
arranging a beam splitter to receive the image-bearing unpolarised light of the image from the image generator at a first side of the beam splitter and to split it into a first path comprising first image-bearing light of a first orientation from the image with unpolarised light and a second path comprising second image-bearing light of a second orientation from the image with unpolarised light;
arranging a first optical arrangement including a first mirror and a first quarter-wave plate that is disposed between the first mirror and a second side of the beam splitter that is opposite the first side, the first quarter-wave plate of the first optical arrangement to receive the first image-bearing light of the first orientation that is in the first path from the beam splitter and output first-hand polarised first light to the first mirror that reflects the first-hand polarised first light back to the first quarter-wave plate as second-hand polarised first light without the first mirror outputting light of an additional image, and the first quarter-wave plate transforms the second-hand polarised first light into first image-bearing light of the second orientation that is output by the first quarter-wave plate to the second side of the beam splitter;
arranging a second optical arrangement including a second mirror and a second quarter-wave plate that is disposed between the second mirror and a third side of the beam splitter, the second quarter-wave plate of the second optical arrangement to receive the second image-bearing light of the second orientation that is in the second path from the beam splitter and output second-hand polarised second light to the second mirror that reflects the second-hand polarised second light back to the second quarter-wave plate as first-hand polarised second light without the second mirror outputting light of an additional image, and the second quarter-wave plate transforms the first-hand polarised second light into second image-bearing light of the first orientation that is output by the second quarter-wave plate to the third side of the beam splitter;
and
aligning the first optical arrangement and the second optical arrangement so that the image from the first path is aligned with the image from the second path when they are combined by the beam splitter and provided to an exit pupil at a fourth side of the beam splitter that is opposite third side with image-bearing unpolarised light.
18 . The method of claim 17 , wherein:
the first mirror and the second mirror are configured to focus light.
19 . The method of claim 17 , wherein the image generator is an LED array.
20 . The method of claim 17 , wherein the beam splitter is a rectangular cuboid comprising a top face corresponding to the fourth side, a bottom face corresponding to the third side, and four side faces including the first side and the second side.