Waveguide and augmented/mixed reality device
A waveguide for guiding an image pixel light includes: a solid body including an optical material which is transparent for at least a light with a wavelength of 460 nm; an in-coupling surface located on the solid body; and an out-coupling surface located on the solid body, wherein the optical material has an absorption coefficient κ460 nm for light having a wavelength of 460 nm, a thermal conductivity k, a coefficient of thermal expansion α20° C. at a temperature of 20° C., a refractive index nF related to the hydrogen F-line, and a derivative dnF/dT20° C. which are related in such a way that a thermally induced change of an optical path length within the waveguide due to an absorption of at least one of heat and an optical radiation is quantitatively described by a merit function.
1 . A waveguide for guiding an image pixel light, the waveguide comprising:
a solid body including an optical material which is transparent for at least a light with a wavelength of 460 nm;
an in-coupling surface located on the solid body and configured for coupling the image pixel light into the solid body; and
an out-coupling surface located on the solid body and configured for coupling the image pixel light out again from the solid body,
the optical material having an absorption coefficient κ 460nm for a light having a wavelength of 460 nm, a thermal conductivity k, a coefficient of thermal expansion α 20° C. at a temperature of 20° C., a refractive index n F related to a hydrogen F-line, and a derivative dn F /dT 20° C. , and
the absorption coefficient κ 460nm , the thermal conductivity k, the coefficient of thermal expansion α 20° C. , the refractive index n F related to the hydrogen F-line, and the derivative dn F /dT 20° C. being related in such a way that a thermally induced change of an optical path length within the waveguide due to an absorption of at least one of heat and an optical radiation is quantitatively described by a merit function, which is dw/dT=w·((1/n)(dn/dT)+α), w being the optical path length, T being a temperature of the solid body, n being a refractive index, and a being a linear coefficient of thermal expansion, dw/dT being within a predetermined range.
2 . The waveguide according to claim 1 , wherein at least one of: (a) the solid body defines a longitudinal axis; and (b) the solid body defines a longitudinal axis and includes two opposing surfaces, the two opposing surfaces being configured for guiding the image pixel light along the longitudinal axis of the solid body by a total reflection.
3 . The waveguide according to claim 2 , further comprising at least one of:
(a) a first optical diffractive structure being configured to redirect the image pixel light; and
(b) a second optical diffractive structure which is configured to redirect the image pixel light.
4 . The waveguide according to claim 3 , wherein the optical material has a refractive index n d related to a helium d-line, and wherein the refractive index n d related to a helium d-line is greater than 1.5, wherein the waveguide is configured for an augmented reality or mixed reality device, which is a near-eye display.
5 . The waveguide according to claim 1 , wherein the optical material defines a thermo-optical function F TO =(κ 460nm /k)((1/n F )(dn F /dT 20° C. )+α 20° C. ).
6 . The waveguide according to claim 1 , wherein at least one of: (a) the absorption coefficient κ 460nm is in a range of 0.01/m to 10/m; and (b) the absorption coefficient κ 460nm is less than 10/m.
7 . The waveguide according to claim 1 , wherein the thermal conductivity k is in a range of 0.5W/(m·K) to 1.5W/(m·K).
8 . The waveguide according to claim 1 , wherein the coefficient of thermal expansion α 20° C. is in a range of 0.5·10-6/K to 15·10-6/K.
9 . The waveguide according to claim 1 , wherein the derivative dn F /dT 20° C. is in a range of −1·10-6/K to +9·10-6/K.
10 . The waveguide according to claim 1 , wherein at least one of: (a) the optical material is optically isotropic; and (b) the optical material is selected from a group consisting of glass, polymer, optoceramics, and crystalline material.
11 . A device, which forms an augmented or mixed reality device, the device comprising:
a waveguide of the device, the waveguide being configured for guiding an image pixel light, the waveguide including:
a solid body including an optical material which is transparent for at least a light with a wavelength of 460 nm;
an in-coupling surface located on the solid body and configured for coupling the image pixel light into the solid body; and
an out-coupling surface located on the solid body and configured for coupling the image pixel light out again from the solid body,
the optical material having an absorption coefficient κ 460nm for a light having a wavelength of 460 nm, a thermal conductivity k, a coefficient of thermal expansion α 20° C. at a temperature of 20° C., a refractive index n F related to a hydrogen F-line, and a derivative dn F /dT 20° C. , and
the absorption coefficient κ 460 nm , the thermal conductivity k, the coefficient of thermal expansion α 20° C. , the refractive index n F related to the hydrogen F-line, and the derivative dn F /dT 20° C. being related in such a way that a thermally induced change of an optical path length within the waveguide due to an absorption of at least one of heat and an optical radiation is quantitatively described by a merit function, which is dw/dT=w·((1/n)(dn/dT)+α), w being the optical path length, T being a temperature of the solid body, n being a refractive index, and a being a linear coefficient of thermal expansion, dw/dT being within a predetermined range.
12 . The device according to claim 11 , wherein during delivery of the image pixel light which is coupled into the waveguide, a temperature gradient |grad T| is obtained in the solid body, wherein the temperature gradient |grad T| is in a range of 1 K/cm to 10 K/cm, wherein the device is a near-eye display.
13 . An optical material, comprising:
the optical material, which has an absorption coefficient κ 460 nm for a light having a wavelength of 460 nm, a thermal conductivity k, a coefficient of thermal expansion α 20 ° C. at a temperature of 20° C., a refractive index n F related to a sodium F-line, and a derivative dn F /dT 20° C. ,
the absorption coefficient κ 460 nm , the thermal conductivity k, the coefficient of thermal expansion α 20° C. , the refractive index n F related to the sodium F-line, and the derivative dn F /dT 20° C. being related in such a way that a thermally induced change of an optical path length within the waveguide due to absorption of at least one of heat and an optical radiation is quantitatively described by a merit function, which is dw/dT=w·((1/n)(dn/dT)+α), w being the optical path length, T being a temperature of a solid body including the optical maaterial, n being a refractive index, and α being a linear coefficient of thermal expansion, dw/dT being within a predetermined range.
14 . The optical material according to claim 13 , wherein the optical material has a refractive index n d na related to a helium d-line, and wherein the refractive index n d related to the helium d-line is greater than 1.5, wherein the optical device is configured for a waveguide or an augmented or mixed reality device.
15 . The optical material according to claim 13 , wherein the optical material defines a thermo-optical function F TO ═(κ 460 mm /k)(1/n F )(dn F /dT 20° C. )+α 20° C. ).
16 . The optical material according to claim 13 , wherein at least one of: (a) the absorption coefficient κ 460 nm is in a range of 0.01/m to 10/m; and (b) the absorption coefficient κ 460 nm is less than 10/m.
17 . The optical material according to claim 13 , wherein the thermal conductivity k is in a range of 0.5W/(m·K) to 1.5W/(m·K).
18 . The optical material according to claim 13 , wherein the coefficient of thermal expansion α 20° C. is in a range of 0.5·10-6/K to 15·10-6/K.
19 . The optical material according to claim 13 , wherein the derivative dn F /dT 20° C. is in a range of −1·10-6/K to +9·10-6/K.
20 . The optical material according to claim 13 , wherein at least one of: (a) the optical material is optically isotropic; and (b) the optical material is selected from a group consisting of glass, polymer, optoceramics, and crystalline material.