Methods and apparatus for backlighting dual modulation display devices

1. A method for backlighting a dual modulation display device comprising a front modulator illuminated by a backlight comprising a plurality of light sources of two or more types, each type of light source comprising a multi-primary light source having two or more primary color light emitters having different primary color characteristics from corresponding primary color emitters of other types of light source, the multi-primary light source of each type of light source comprising a red primary color emitter, wherein the plurality of the light sources of said two or more types are arranged as an array in alternating fashion, the method comprising:

i. receiving illumination target values for a plurality of locations on the front modulator corresponding to the plurality of light sources, each of the locations on the front modulator configured to be illuminated by two or more of the plurality of light sources;

ii. determining primary color drive values for each primary color for each type of light source based on the primary color characteristics for that primary color and the illumination target value for the location corresponding to that light source, wherein

each adjacent two or more different types of horizontally neighboring light sources form a group and the primary color drive values are determined for each group wherein coupling factors of light spread energy from one light source to the respective other light sources of each group are postulated to be equal when determining said primary color drive values for said group and the red primary color emitter of each type of light source is forced to have the same primary drive value; and

iii. driving the primary color light emitters of each type of light source based on the primary color drive values.

2. A method according to claim 1 wherein the primary color drive values for each type of light source are determined based on the primary color characteristics of that type of light source and the primary color characteristics of at least one other type of light source.

3. A method according to claim 1 comprising determining primary color drive values for a group of light sources selected based on locations and spread functions of the light sources.

4. A method according to claim 1 wherein determining primary color drive values comprises:

i. determining preliminary drive values for each light source based on the type of that light source;

ii. determining weightings for each primary color of each type of light source; and,

iii. applying the weightings to the preliminary drive values.

5. A method according to claim 4 wherein determining the preliminary drive values for each light source comprises converting a fraction of the illumination target value corresponding to that light source to a color space corresponding to the primary color light emitters of that light source.

6. A method for backlighting a dual modulation display device comprising a front modulator illuminated by a backlight comprising a plurality of light sources of two or more types, each type of light source comprising a multi-primary light source having two or more primary color light emitters having different primary color characteristics from corresponding primary color emitters of other types of light source, the multi-primary light source of each type of light source comprising a red primary color emitter, wherein the plurality of the light sources of said two or more types are arranged as an array in alternating fashion, the method comprising:

i. receiving illumination target values for a plurality of locations on the front modulator corresponding to the plurality of light sources, each of the locations on the front modulator configured to be illuminated by two or more of the plurality of light sources;

ii. determining primary color drive values for each primary color for each type of light source based on the primary color characteristics for that primary color and the illumination target value for the location corresponding to that light source, wherein

each adjacent two or more different types of horizontally neighboring light sources form a group and the primary color drive values are determined for each group wherein coupling factors of light spread energy from one light source to the respective other light sources of each group are postulated to be equal when determining said primary color drive values for said group and the red primary color emitter of each type of light source is forced to have the same primary drive value; and

iii. driving the primary color light emitters of each type of light source based on the primary color drive values

wherein determining primary color drive values comprises:

determining preliminary drive values for each light source based on the type of that light source;

determining weightings for each primary color of each type of light source; and,

applying the weightings to the preliminary drive values

and the method comprises determining the weightings by comparing target locations in chromaticity space of the illumination target values to primary locations in chromaticity space of light from the primary color light emitters.

7. A method according to claim 6 comprising determining the weightings based on distances between each primary location and the target location.

8. A method according to claim 7 wherein the weightings are based on a ratio of distances between each primary location and the target location.

9. A method according to claim 6 comprising determining the weighting for each primary color based on distances:

i. between the primary location of one type of light source and the corresponding primary location of another type;

ii. between a midpoint between corresponding primary locations and a white point;

iii. from an orthogonal projection of the target location onto a line passing through the corresponding primary locations to each primary location; and

iv. from an orthogonal projection of the target location onto a line passing through the mid point and the white point to the mid point and to the white point.

10. Apparatus for generating backlight driving signals for a dual modulation display device comprising a front modulator illuminated by a backlight comprising a plurality of light sources of two or more types, each type of light source comprising a multi-primary light source having two or more primary color light emitters having different primary color characteristics from corresponding primary color emitters of other types of light source, the multi-primary light source of each type of light source comprising a red primary color emitter, wherein the plurality of the light sources of said two or more types are arranged as an array in alternating fashion, the apparatus comprising:

i. an illumination target value generator configured to generate illumination target values for a plurality of locations on the front modulator corresponding to the plurality of light sources, each of the locations on the front modulator configured to be illuminated by two or more of the plurality of light sources; and,

ii. a multi-primary calculator configured to determine primary color drive values for each primary color of each type of light source based on the primary color characteristics for that primary color and the illumination target value for the location corresponding to that light source, wherein each adjacent two or more different types of horizontally neighboring light sources form a group and the primary color drive values are determined for each group wherein coupling factors of light spread energy from one light source to the respective other light sources of each group are postulated to be equal when determining said primary color drive values for said group and the red primary color emitter of each type of light source is forced to have the same primary drive value, and output the primary color drive values to a backlight driving circuit.

11. Apparatus according to claim 10 wherein the multi-primary calculator is configured to determine primary color drive values for each type of light source based on the primary color characteristics of that type of light source and the primary color characteristics of at least one other type of light source.

12. Apparatus according to claim 10 wherein the multi-primary calculator is configured to determine primary color drive values for a group of light sources selected based on locations and spread functions of the light sources.

13. Apparatus according to claim 10 wherein the multi-primary calculator is configured to determine primary color drive values for each light source independently based on the primary color characteristics of one or more neighboring light sources.

14. Apparatus according to claim 13 wherein the multi-primary calculator is configured to determine, for each light source, drive values for two or more types of light source and select the drive values for the type of light source corresponding to that light source.

15. Apparatus according to claim 10 wherein the multi-primary calculator is configured to determine primary color drive values by:

i. determining preliminary drive values for each light source based on the type of that light source;

ii. determining weightings for each primary color of each type of light source; and,

iii. applying the weightings to the preliminary drive values.

16. Apparatus for generating backlight driving signals for a dual modulation display device comprising a front modulator illuminated by a backlight comprising a plurality of light sources of two or more types, each type of light source comprising a multi-primary light source having two or more primary color light emitters having different primary color characteristics from corresponding primary color emitters of other types of light source, the multi-primary light source of each type of light source comprising a red primary color emitter, wherein the plurality of the light sources of said two or more types are arranged as an array in alternating fashion, the apparatus comprising:

i. an illumination target value generator configured to generate illumination target values for a plurality of locations on the front modulator corresponding to the plurality of light sources, each of the locations on the front modulator configured to be illuminated by two or more of the plurality of light sources; and,

ii. a multi-primary calculator configured to determine primary color drive values for each primary color of each type of light source based on the primary color characteristics for that primary color and the illumination target value for the location corresponding to that light source, wherein each adjacent two or more different types of horizontally neighboring light sources form a group and the primary color drive values are determined for each group wherein coupling factors of light spread energy from one light source to the respective other light sources of each group are postulated to be equal when determining said primary color drive values for said group and the red primary color emitter of each type of light source is forced to have the same primary drive value, and output the primary color drive values to a backlight driving circuit;

wherein the multi-primary calculator is configured to determine primary color drive values by:

determining preliminary drive values for each light source based on the type of that light source;

determining weightings for each primary color of each type of light source; and,

applying the weightings to the preliminary drive values;

wherein the multi-primary calculator is configured to determine primary color drive values for each light source by converting a fraction of the illumination target value corresponding to that light source to a color space corresponding to the primary color light emitters of that light source.

17. Apparatus for generating backlight driving signals for a dual modulation display device comprising a front modulator illuminated by a backlight comprising a plurality of light sources of two or more types, each type of light source comprising a multi-primary light source having two or more primary color light emitters having different primary color characteristics from corresponding primary color emitters of other types of light source, the multi-primary light source of each type of light source comprising a red primary color emitter, wherein the plurality of the light sources of said two or more types are arranged as an array in alternating fashion, the apparatus comprising:

i. an illumination target value generator configured to generate illumination target values for a plurality of locations on the front modulator corresponding to the plurality of light sources, each of the locations on the front modulator configured to be illuminated by two or more of the plurality of light sources; and,

ii. a multi-primary calculator configured to determine primary color drive values for each primary color of each type of light source based on the primary color characteristics for that primary color and the illumination target value for the location corresponding to that light source, wherein each adjacent two or more different types of horizontally neighboring light sources form a group and the primary color drive values are determined for each group wherein coupling factors of light spread energy from one light source to the respective other light sources of each group are postulated to be equal when determining said primary color drive values for said group and the red primary color emitter of each type of light source is forced to have the same primary drive value, and output the primary color drive values to a backlight driving circuit;

wherein the multi-primary calculator is configured to determine primary color drive values by:

determining preliminary drive values for each light source based on the type of that light source;

determining weightings for each primary color of each type of light source; and,

applying the weightings to the preliminary drive values;

wherein the multi-primary calculator is configured to determine the weightings by comparing target locations in chromaticity space of the illumination target values to primary locations in chromaticity space of light from the primary color light emitters.

18. Apparatus according to claim 17 wherein the multi-primary calculator is configured to determine the weightings based on distances between each primary location and the target location.

19. Apparatus according to claim 18 wherein the multi-primary calculator is configured to determine the weightings based on a ratio of distances between each primary location and the target location.

20. Apparatus according to claim 17 wherein the multi-primary calculator is configured to determine the weighting for each primary color based on distances:

i. between the primary location of one type of light source and the corresponding primary location of another type;

ii. between a midpoint between corresponding primary locations and a white point;

iii. from an orthogonal projection of the target location onto a line passing through the corresponding primary locations to each primary location; and

iv. from an orthogonal projection of the target location onto a line passing through the mid point and the white point to the mid point and to the white point.