Light guide with patterned ink

1. A light-emitting system, comprising:

a light guide configured to guide light received from a light source;

a first light extraction element positioned on a first surface of the light guide and configured to extract a portion of the guided light from the light guide, the first light extraction element having a first reflectance and a first transmittance; and

a second light extraction element positioned on the first surface of the light guide and configured to extract a portion of the guided light from the light guide, the second light extraction element having a second reflectance different from the first reflectance, the second light extraction element having a second transmittance different from the first transmittance.

2. The light-emitting system of claim 1 , wherein:

the first light extraction element being printed on the first surface of the light guide with a first ink; and

the second light extraction element being printed on the first surface of the light guide with a second ink different from the first ink.

3. The light-emitting system of claim 1 , wherein the first light extraction element is configured such that light extracted from the light guide by the first light extraction element has an angular distribution that is approximately Lambertian.

4. The light-emitting system of claim 1 , wherein the first reflectance and the first transmittance sum to about 100%.

5. The light-emitting system of claim 1 , wherein the first reflectance is about 90% and the first transmittance is about 10%.

6. The light-emitting system of claim 1 , wherein the second light extraction element is configured such that light extracted from the light guide by the second light extraction element has an angular distribution that is approximately batwing.

7. The light-emitting system of claim 1 , wherein the second reflectance and the second transmittance sum to about 100%.

8. The light-emitting system of claim 1 , wherein the second reflectance is about 45% and the second transmittance is about 55%.

9. The light-emitting system of claim 8 , wherein the second light extraction element is configured to have a Gaussian diffusion pattern of about 15 degrees.

10. The light-emitting system of claim 1 , wherein:

the first light extraction element is configured such that light extracted from the light guide by the first light extraction element has an angular distribution that is approximately Lambertian;

the second light extraction element is configured such that light extracted from the light guide by the second light extraction element has an angular distribution that is approximately batwing; and

the first surface of the light guide is configured such that light extracted from the light guide by the first light extraction element and the second light extraction element, combined, has an angular distribution that is wider than Lambertian and narrower than batwing.

11. The light-emitting system of claim 1 , further comprising:

a first plurality of light extraction elements positioned on the first surface of the light guide, the first plurality of light extraction elements including the first light extraction element, each light extraction element of the first plurality having a reflectance that equals the first reflectance and a transmittance that equals the first transmittance; and

a second plurality of light extraction elements positioned on the first surface of the light guide, the second plurality of light extraction elements including the second light extraction element, each light extraction element of the second plurality having a reflectance that equals the second reflectance and a transmittance that equals the second transmittance.

12. The light-emitting system of claim 11 , wherein:

the first plurality of light extraction elements are configured such that light extracted from the light guide by each first light extraction element has an angular distribution that is approximately Lambertian;

the second plurality of light extraction elements are configured such that light extracted from the light guide by each second light extraction element has an angular distribution that is approximately batwing; and

the first surface of the light guide is configured such that light extracted from the light guide by the first plurality of light extraction elements and the second plurality light extraction elements, combined, has an angular distribution that is wider than Lambertian and narrower than batwing.

13. The light-emitting system of claim 1 , further comprising the light source, the light source configured to inject light into the light guide through an edge of the light guide.

14. The light-emitting system of claim 1 , further comprising the light source, the light source being positioned in a cavity in the light guide and configured to inject light into the light guide through one or more walls of the cavity.

15. A method for emitting light, the method comprising:

receiving, with a light guide, light from a light source;

guiding, with the light guide, a first portion of the received light to a first light extraction element positioned on a first surface of the light guide, the first light extraction element having a first reflectance and a first transmittance;

extracting, from the light guide, a second portion of the light with the first light extraction element;

guiding, with the light guide, a third portion of the received light to a second light extraction element positioned on the first surface of the light guide, the second light extraction element having a second reflectance different from the first reflectance, the second light extraction element having a second transmittance different from the first transmittance; and

extracting, from the light guide, a fourth portion of the light with the second light extraction element.

16. The method of claim 15 , wherein:

the second portion comprises the first portion, multiplied by the first transmittance; and

the fourth portion comprises the third portion, multiplied by the second transmittance.

17. The method of claim 15 , further comprising:

reflecting, with the first light extraction element, a fifth portion of light such that the fifth portion remains in the light guide; and

reflecting, with the second light extraction element, a sixth portion of light such that the sixth portion remains in the light guide.

18. The method of claim 17 , wherein:

the fifth portion comprises the first portion, multiplied by the first reflectance; and

the sixth portion comprises the third portion, multiplied by the second reflectance.

19. The method of claim 15 , wherein the second light extraction element is configured to have a Gaussian diffusion pattern of about 15 degrees, and further comprising:

angularly broadening the light with the second light extraction element, such that the fourth portion of the light has an angular distribution that is wider than an angular distribution of the second portion of the light.

20. A light-emitting system, comprising:

a light source configured to produce light;

a light guide configured to receive light from the light source and guide the received light;

a plurality of first light extraction elements positioned on a first surface of the light guide, each first light extraction element configured to extract a portion of the guided light from the light guide, the first light extraction elements having a same first reflectance and a same first transmittance, each first light extraction element being printed on the first surface with a first ink; and

a plurality of second light extraction elements positioned on the first surface of the light guide, each second light extraction element configured to extract a portion of the guided light from the light guide, each second light extraction element having a second reflectance different from the first reflectance, each second light extraction element having a second transmittance different from the first transmittance, each second light extraction element being printed on the first surface with a second ink different from the first ink.