Illumination control

1. A diffusion lens for a light source, the lens comprising an adjustable light diffusing layer, wherein the adjustable light diffusing layer is configured so that transmittance properties of the adjustable light diffusing layer can be variably adjusted during operation of a viewable device, such that transmittance through the adjustable light diffusing layer varies inversely with respect to an intensity of light impacting the adjustable light diffusing layer so that luminance variation is reduced over the surface of the lens.

2. The diffusion lens of claim 1 , wherein the light source comprises one or more light emitting diodes (LEDs).

3. The diffusion lens of claim 1 , wherein the light diffusing layer comprises one or more of the following: polymer-dispersed liquid crystals (PDLCs), electrochromatic materials, and photochromic materials.

4. The diffusion lens of claim 1 , wherein the light diffusing layer is on at least one of a light guide, a diffuser, a reflector, a liquid crystal display, an optical layer, a transparent conductive layer, a bulb of the light source, or a case of the light source.

5. The diffusion lens of claim 1 , further comprising a substrate under the light diffusing layer, wherein the substrate comprises at least one of glass, plastic, acrylic, polyester, or an organic layer.

6. The diffusion lens of claim 1 , wherein a surface area of the light diffusing layer is greater than 150 mm 2 .

7. The diffusion lens of claim 1 , wherein the light diffusing layer comprises two or more transparent electrodes and polymer-dispersed liquid crystals.

8. The diffusion lens of claim 1 , wherein the light diffusing layer comprises two or more transparent electrodes and an electrochromatic layer.

9. The diffusion lens of claim 1 , wherein the light diffusing layer comprises a photochromatic layer, wherein the photochromatic layer comprises one or more layers comprising silver halide or a photochromatic pigment.

10. The diffusion lens of claim 1 , wherein luminance variation is a change in luminous intensity of light passing through a first portion and a second portion of the diffusion lens.

11. The diffusion lens of claim 1 , wherein reduced luminance variation is a decrease in the change in luminous intensity of light passing through a first portion and a second portion of the diffusion lens compared to a change in luminous intensity of light passing through a first portion and a second portion of a comparable surface without a light diffusing layer.

12. A method of modulating luminous intensity of light from a light source, the method comprising:

a) providing at least one light source;

b) providing a diffusion lens according to claim 1 interposed between a viewer and the at least one light source; and

c) adjusting a transmittance of the diffusion lens in accordance with a luminous intensity of light from the at least one light source such that transmittance of the diffusion lens varies inversely with luminous intensity.

13. The method of claim 12 wherein the light source comprises one or more LEDs.

14. The method of claim 12 , wherein the diffusion lens comprises at least one of the following: polymer-dispersed liquid crystals (PDLCs), electrochromatic materials, and photochromic materials.

15. The method of claim 12 , wherein the transmittance of the diffusion lens is adjusted by applying a voltage to the luminance adjusting layer, wherein the lens comprises two or more transparent electrodes and a liquid crystal layer comprising polymer-dispersed liquid crystals.

16. The method of claim 12 , wherein the transmittance of the diffusion lens is adjusted by applying a voltage to the diffusion lens, wherein the diffusion lens comprises two or more transparent electrodes and an electrochromatic layer.

17. The method of claim 12 , wherein the transmittance of the diffusion lens is adjusted by altering the absorbance of the diffusion lens, wherein the diffusion lens comprises photochromatic layer comprised of one or more layers comprising silver halide or a photochromatic pigment.

18. A light source comprising:

a substrate; and

a diffusion lens according to claim 1 , wherein the light diffusing layer is configured to adjust light transmittance through the layer in accordance with luminous intensity so as to reduce differences in the luminous intensity of light exiting the light source.

19. The light source of claim 18 , wherein the light source comprises 2 or more light sources.

20. The light source of claim 18 , wherein the light source is larger than 150 mm 2 .

21. The light source of claim 18 , wherein the diffusion lens comprises one or more of the following: a polymer-dispersed liquid crystal (PDLC), an electrochromatic material, and a photochromic material.

22. The light source of claim 18 , wherein the diffusion lens comprises a photochromatic layer comprised of one or more layers comprising at least one of a silver halide or a photochromatic pigment.

23. The light source of claim 18 , wherein the diffusion lens comprises two or more transparent electrodes and a liquid crystal layer comprising polymer-dispersed liquid crystals.

24. The light source of claim 18 , wherein the diffusion lens comprises two or more transparent electrodes and an electrochromatic layer.

25. The light source of claim 18 , wherein the diffusion lens is on top of a surface of the substrate.

26. The light source of claim 18 , wherein the light source comprises a LED.

27. A method of modulating luminous intensity of light from a light source, the method comprising:

a) providing at least one light source;

b) providing a diffusion lens according to claim 1 interposed between a viewer and the at least one light source; and

c) directing light from the light source to the diffusion lens such that transmittance from the diffusion lens varies inversely with luminous intensity.