Thin film polarization splitter, its manufacture and ophthalmic lens with projection inserts containing it
View Patent ↗This invention features a thin film polarization splitter, its manufacture and ophthalmic lens with projection inserts containing it.
1. Apparatus comprising:
a polarization splitter comprising a substrate provided with an alternating stack of layers of PrTiO 3 and a material having a lower refractive index, the thickness of these layers e 1 and e 2 respectively satisfying the relations:
e
1
=
λ
n
1
2
+
n
2
2
4
n
1
2
e
2
=
λ
n
1
2
+
n
2
2
4
n
2
2
in which λ is the wavelength considered, n 1 is the refractive index of the first layer and n 2 is the refractive index of the second layer respectively.
2. The apparatus according to claim 1 , wherein the substrate is organic.
3. The apparatus according to claim 2 , wherein the organic substrate is a polythiourethane.
4. The apparatus according to claim 1 , wherein the second material is silicon dioxide.
5. The apparatus according to claim 1 , carrying respectively at least six layers of praseodymium titanate and of second material.
6. The apparatus according to claim 1 , in the form of a cube formed from two prisms one of which is coated with layers of PrTiO 3 and material of lower refractive index according to claim 1 .
7. Apparatus comprising:
a polarization splitter comprising an organic substrate provided with an alternating stack of at least six layers of PrTiO 3 and silicon dioxide, the thickness of these layers e 1 and e 2 respectively satisfying the relations:
e
1
=
λ
n
1
2
+
n
2
2
4
n
1
2
e
2
=
λ
n
1
2
+
n
2
2
4
n
2
2
in which λ is the wavelength considered, n 1 is the refractive index of the first layer and n 2 is the refractive index of the second layer respectively.
8. A method for producing a polarization splitter comprising:
(i) providing a substrate;
(ii) depositing a layer of praseodymium titanate of a thickness e 1 ;
(iii) depositing a layer of a second material of a thickness e 2 ; such that
e
1
=
λ
n
1
2
+
n
2
2
4
n
1
2
e
2
=
λ
n
1
2
+
n
2
2
4
n
2
2
in which λ is the wavelength considered, n 1 is the refractive index of the first layer and n 2 is the refractive index of the second layer, wherein n 1 is greater than n2; and
(iv) repeating steps (ii) and (iii) at least once.
9. The method according to claim 8 , wherein step (iv) comprises at least five repetitions of steps (ii) and (iii).
10. The method according to claim 8 , wherein the substrate is maintained at a temperature greater than ambient temperature during steps (ii) to (iv).
11. The method according to claim 10 , wherein the substrate is maintained at a temperature comprised between 80 and 120° C. during steps (ii) to (iv).
12. The method according to one of claim 8 , wherein the substrate is subject to ionic cleaning prior to step (ii).
13. The method according to claim 12 , wherein the ionic cleaning is performed under argon.
14. The method according to claim 8 , wherein the rate of evaporation during steps (ii) and (iii) is from 1 to 10 nm/s.
15. The method according to claim 14 , wherein the rate of evaporation during steps (ii) and (iii) is from 2 to 5 nm/s.
16. The apparatus of claim 1 , further comprising an ophthalmic lens having inserts for projecting an image towards a user, the inserts comprising the polarization beam splitter.
17. The apparatus of claim 7 , further comprising an ophthalmic lens having inserts for projecting an image towards a user, the inserts comprising the polarization beam splitter.
18. The apparatus according to claim 16 , wherein the polarization beam splitter is in the form of a cube.
19. The apparatus according to claim 17 , wherein the polarization beam splitter is in the form of a cube.
20. The apparatus of claim 16 , further comprising a device for projecting an image towards a user, the projecting device comprising the ophthalmic lens.
21. The apparatus of claim 17 , further comprising a device for projecting an image towards a user, the projecting device comprising the ophthalmic lens.
22. The apparatus of claim 20 , the projection device further comprising a liquid crystal micro-display.
23. The apparatus of claim 21 , the projection device further comprising a liquid crystal micro-display.