Display device and system
A head-up display for a vehicle, the head-up display including a picture generating unit arranged to generate a picture on a light receiving surface; and an optical system arranged to image the picture, where the optical system includes an input arranged to receive light of the picture; an output arranged to output light forming an image of the picture; a first mirror and second mirror arranged to guide light from the input to the output along an optical path, where the optical path includes a first optical path from the input to the second mirror including a transmission through the first mirror; and second optical path from the second mirror to the output including a reflection off the first mirror.
1. A head-up display for a vehicle, the head-up display comprising:
a picture generating unit arranged to generate a picture on a light receiving surface, wherein the picture generating unit comprises:
a light source arranged to emit light;
a spatial light modulator arranged to receive the light from the light source and output spatially-modulated light in accordance with a computer-generated hologram represented on the spatial light modulator to form the picture on the light receiving surface; and
a holographic processor arranged to output the computer-generated hologram to the spatial light modulator,
wherein the head-up display further comprises:
an optical system arranged to image the picture, wherein the optical system comprises:
an input arranged to receive light of the picture;
an output arranged to output light forming an image of the picture;
a first mirror and a second mirror arranged to guide light from the input to the output along an optical path, wherein the optical path comprises: a first optical path from the input to the second mirror, wherein the first mirror comprises a polarisation-selective filter configured to reflect light polarised in a first direction and transmit light polarised in a second direction; and a second optical path from the second mirror to the output including a reflection of the light polarised in the first direction off the first mirror.
2. The head-up display as claimed in claim 1 wherein the first transmission through the first mirror comprises a transmission through a first surface of the first mirror and then a transmission through a second surface of the first mirror, wherein a radius of curvature of the first surface is less than a radius of curvature of the second surface.
3. The head-up display as claimed in claim 1 wherein the picture generating unit, the first mirror and the second mirror are arranged on a common straight-line axis.
4. The head-up display as claimed in claim 1 wherein the picture generating unit, the first mirror and the second mirror are substantially coplanar.
5. The head-up display as claimed in claim 1 wherein the light of the picture received by the input of the optical system is polarised in a first direction.
6. The head-up display as claimed in claim 5 wherein the optical system comprises a quarter-waveplate disposed between the first mirror and second mirror, wherein the first optical path includes a first pass of the quarter-waveplate and the second optical path includes a second pass of the quarter-waveplate, wherein the quarter-waveplate is a coating on the second mirror.
7. The head-up display as claimed in claim 1 wherein the second direction is perpendicular to the first direction.
8. The head-up display as claimed in claim 1 wherein the optical system further comprises a third mirror on the optical path; and the first optical path further comprises a second transmission through the first mirror and a reflection off the third mirror.
9. The head-up display as claimed in claim 8 wherein: the second transmission through the first mirror occurs before the reflection off the third mirror; and the reflection off the third mirror occurs before the first transmission through the first mirror.
10. The head-up display as claimed in claim 8 wherein the third mirror is substantially collinear or coplanar with the first mirror and the second mirror.
11. The head-up display as claimed in claim 1 wherein the light of the picture received by the input of the optical system has a first wavelength and the optical system further comprises at least one laser-line selective filter on the optical path.
12. The head-up display as claimed in claim 11 wherein the at least one laser-line selective filter is a coating on the first mirror or the second mirror and the laser-line selective filter is substantially transmissive at the first wavelength and substantially non-transmissive at other optical wavelengths.
13. The head-up display as claimed in claim 12 wherein the laser-line selective filter is the reflective component of the first or the second mirror and the laser-line selective filter is substantially reflective at the first wavelength and substantially non-reflective at other optical wavelengths.
14. The head-up display as claimed in claim 11 wherein the laser-line selective filter is correspondingly selective at a second wavelength and a third wavelength, wherein the second wavelength is not equal to the first wavelength and the third wavelength is not equal to the first wavelength or second wavelength.
15. A method for providing a head-up display for a vehicle, the method comprising:
generating a picture on a light receiving surface, the generating comprising:
representing a computer-generated hologram on a spatial light modulator;
receiving light from a light source on the spatial light modulator;
outputting from the spatial light modulator spatially-modulated light in accordance with a computer-generated hologram; and
receiving the spatially-modulated light on the light receiving surface to form the picture on the light receiving surface,
wherein the method further comprises:
imaging the picture using an optical system, wherein the imaging comprises:
receiving light of the picture at an input of an optical system; and
guiding light of the picture from the input to an output along an optical path, wherein the optical path comprises: a first optical path from the input to a second mirror including, wherein the first mirror comprises a polarisation-selective filter configured to reflect light polarised in a first direction and transmit light polarised in a second direction; and a second optical path from the second mirror to the output including a reflection of the light polarised in the first direction off the first mirror.
16. The method as claimed in claim 15 , wherein the first transmission through the first mirror comprises a transmission through a first surface of the first mirror and then a transmission through a second surface of the first mirror, wherein a radius of curvature of the first surface is less than a radius of curvature of the second surface.
17. The method as claimed in claim 15 , wherein the first mirror is substantially transmissive to light polarised in a first direction and substantially reflective to light polarised in a second direction, wherein the second direction is perpendicular to the first direction.