Colour display device
A color display device ( 1 ) comprises a plurality of picture elements ( 3, 4, 5 ), the plurality of picture elements having a viewing side ( 5 ) and a rear side ( 6 ). Each picture element includes a light valve ( 7, 8, 9 ). The display device comprises a switchable part ( 12, 13 ) for selectively directing light of a first color and light of a second color through the light valve from the rear side to the viewing side. Each light valve comprises a first and a second switchable color filter ( 17, 19 ) having a transmittance for a third color and a fourth color, respectively, and arranged in succession in the path of the light.
1. A colour display device comprising a plurality of picture elements, the plurality of picture elements having a viewing side and a rear side, each picture element including a light valve,
the display device comprising a switchable part for selectively directing light of a first colour and light of a second colour along a light path through the light valve from the rear side to the viewing side, and
each light valve comprising a first and a second switchable colour filter having a transmittance for a third colour and a fourth colour, respectively, and arranged in succession in the light path, the first, second, third and fourth colour being different non-white colours.
2. A colour display device according to claim 1 , wherein each picture element comprises one light valve.
3. A colour display device according to claim 1 , wherein each light valve includes an electrowetting element having a fluid operable as switchable colour filter.
4. A colour display device according to claim 3 , wherein the electrowetting element includes an electrowetting cell having two fluids independently operable as switchable colour filter.
5. A colour display device according to claim 1 , wherein the switchable part includes an illumination unit for generating light of the first colour and light of the second colour.
6. A colour display device according to claim 5 , wherein the illumination unit is arranged on the rear side of the plurality of light valves.
7. A colour display device according to claim 5 , wherein the illumination unit is arranged on the viewing side of the plurality of light valves and a reflector is arranged on the rear side of the plurality of light valves.
8. A colour display device according to claim 1 , wherein the switchable part includes a controllable reflector having a reflectance selectable between the first colour and the second colour and arranged on the rear side of the plurality of light valves.
9. A colour display device according to claim 8 , wherein the controllable reflector includes a colour filter having a transmission selectable between the first colour and the second colour.
10. A colour display device according to claim 8 , wherein the switchable part includes a plurality of controllable reflectors, each controllable reflector being arranged on the rear side of each of the light valves.
11. A colour display device according to claim 10 , wherein the reflectance of each of the reflectors is independently controllable.
12. A colour display device according to claim 1 , wherein the first colour and the third colour are complementary and the second colour and the fourth colour are complementary.
13. A colour display device according to claim 1 , wherein the switchable part is arranged for selectively directing light of a further colour and/or the light valve comprises a further switchable colour filter having a transmittance for a further colour.
14. A method of forming a colour image using a plurality of picture elements, the plurality of picture elements having a viewing side and a rear side, each picture element containing a light valve, the method comprising the steps of
time-sequentially directing light of a first colour and light of a second colour along a light path through the light valve from the rear side to the viewing side, and
filtering the light by a first and a second switchable colour filter in the light valve, the first and second filter having a transmittance for a third colour and a fourth colour, respectively, and arranged in succession in the path of the light,
the switching of the colour filters being synchronous with the time-sequentially directing light of the first colour and light of the second colour.
15. A method according to claim 14 , including the step of generating the light of the first colour and the light of the second colour in an illumination unit.
16. A method according to claim 15 , in which the illumination unit is arranged on the rear side of the plurality of light valves.
17. A method according to claim 15 , in which the illumination unit is arranged on the viewing side of the plurality of light valves.
18. A method according to claim 14 , the method including the step of passing light entering from the viewing side through light valves twice via a reflector arranged on the rear side of the plurality of light valves.
19. A colour display device according to claim 1 , wherein the switchable part and each light valve are independently controllable.
20. A method according to claim 14 , wherein the switching of the colour filters and the time-sequentially directing light are independently controllable.