Hierarchical Multicolor Primaries Temporal Multiplexing System

• US 20100091050A1
• Filed: 10/10/2008
• Published: 04/15/2010
• Est. Priority Date: 10/10/2008
• Status: Active Grant

• Current Assignee: Ostendo Technologies Inc.
• Original Assignee: Ostendo Technologies Inc.
• Inventors: El-Ghoroury, Hussein S., Majumder, Aditi, Brown, Robert G. W., Lanzone, Andrew J.
• Granted Patent: US 8,098,265 B2
• Time in Patent Office: Days
• US Class Current: 345/691
• CPC Class Codes: H04N 9/3155 for controlling the light source light source control per se H05B35/00 – H05B47/00; control of an illumination source for displays in general G09G3/3406
• CPC Class Codes: H04N 9/3164 using multiple light sources
• CPC Class Codes: H04N 9/3182 Colour adjustment, e.g. white balance, shading or gamut white balance per se H04N9/73; control of amplitude of colour signals H04N9/68; colour control circuits for displays in general G09G5/02, G09G3/2003, G09G3/3607

Abstract

This invention describes an apparatus, methods and a system for high speed hierarchical multiplexing the native color primaries of SSL-based display systems in order to improve color quality and stability as well as brightness and the efficiency of the display system.

Claims

1. A solid state light (SSL) based projection display system comprising:

a spatial light modulator (SLM) device having a plurality of digitally controllable pixels and illuminated by a plurality of SSL devices optically coupled to the SLM by illumination optics;

projection optics optically coupled to the SLM device to magnify an image generated by the SLM device;

a pulse width modulation (PWM) block coupled to the SLM device to control the reflective states of each of the pixels of an image forming surface of the SLM device; and

a hierarchical multiplexing functional block coupled to receive digital image data and a multiplicity of other external inputs and to provide control and synchronization signals to the plurality of SSL devices and the PWM modulation functional block.

2. The hierarchical multiplexing functional block of claim 1 coupled to accept an externally provided image frame cycle signal and generate two lower tier synchronization signals, a first conveying timing of color slots comprising the image frame cycle, and a second conveying timing of simultaneous on/off duty cycles of the SSL devices in each of the plurality of color slots.

3. The solid state light (SSL) based projection display system of claim 2 wherein the plurality of solid state (SSL) devices each provide one of a multiplicity of light color primaries, each SSL device being electrically coupled to receive a temporal control signal for temporal control of the on/off state of each SSL device in each color slot in synchronism with the timing of the respective duty cycle.

4. The solid state light (SSL) based projection display system of claim 3 wherein the SSL devices operate simultaneously and at different duty cycles during different color slot cycles.

5. The solid state light (SSL) based projection display system of claim 3 wherein the hierarchical multiplexing functional block computes the simultaneous duty cycles during each of the plurality of color slots of each of the SSL device light color primaries required to synthesize the target white point.

6. The solid state light (SSL) based projection display system of claim 2 wherein the pulse width modulation (PWM) block is coupled to receive 1-bit fields specifying each image pixel on/off state, a color slot synchronization signal and a digital control word specifying the number of color slot cycles to apply the image pixel on/off state 1-bit fields to control the digitally controllable pixels.

7. The solid state light (SSL) based projection display system of claim 6 wherein:

the plurality of solid state (SSL) devices each provide one of a multiplicity of light color primaries, each SSL device being electrically coupled to receive a temporal control signal for temporal control of the on/off state of each SSL device in each color slot in synchronism with the timing of the respective duty cycle; and

,

the hierarchical multiplexing functional block is coupled to provide the SSL devices with the on/off state temporal control signal in synchronism with providing the pulse width modulation (PWM) functional block with 1-bit fields specifying the on/off state of each of the digital image pixels and the digital control word specifying the number of color slot cycles to apply the conveyed 1-bit fields data.

8. The solid state light (SSL) based projection display system of claim 2 wherein:

the plurality of solid state (SSL) devices provide a multiplicity of light color primaries, each SSL device being electrically coupled to allow temporal control of the on/off duty cycles of the SSL device in each color slot in synchronism with the timing of the respective duty cycle;

wherein the hierarchical multiplexing functional block is coupled to accept an external signal specifying brightness and chromaticity (SSL gamut) of each of the light color primaries generated by the plurality of SSL devices;

to accept an external signal specifying the brightness and chromaticity of color primaries defining a target gamut for the display system; and

to accept an external signal specifying the brightness and chromaticity of a target white point for the display system.

9. The solid state light (SSL) based projection display system of claim 8 wherein the target gamut is fully contained within the SSL gamut.

10. The solid state light (SSL) based projection display system of claim 8 wherein the target gamut is either NTSC or HDTV display systems gamut standards.

11. The solid state light (SSL) based projection display system of claim 8 wherein:

the plurality of solid state (SSL) devices provide a multiplicity of light color primaries, each SSL device being electrically coupled to allow temporal control of the on/off state of each SSL device in each of a plurality of color slots in synchronism with the timing of the respective duty cycle; and

,

wherein the hierarchical multiplexing functional block is coupled to compute the simultaneous on/off duty cycles during each of the color slots of each of the light color primaries generated by the plurality of SSL devices required to synthesize each of the color primaries defining the target gamut.

12. The solid state light (SSL) based projection display system of claim 11 wherein the hierarchical multiplexing functional block allocates within each image frame cycle an appropriate number of color slots to each of the synthesized color primaries.

13. The solid state light (SSL) based projection display system of claim 12 wherein:

wherein the pulse width modulation (PWM) block is coupled to receive 1-bit fields specifying each image pixel on/off state, a color slot synchronization signal and a digital control word specifying the number of color slot cycles to apply the image pixel on/off state 1-bit fields to control the states of each of the pixels; and

,

wherein the allocated number of color slots is sufficient to convey the value of the multiple bit words of each of the image pixel'"'"'s grayscale values in the digital image data using the 1-bit fields.

14. The solid state light (SSL) based projection display system of claim 8 wherein the color slots are comprised of a number of the SSL duty cycles sufficient to achieve a required precision to synthesize the target gamut color primaries.

15. The solid state light (SSL) based projection display system of claim 8 wherein:

the hierarchical multiplexing functional block interleaves the color slots allocated to the synthesized target gamut color primaries to reduce the temporal spackle that could be caused by excessive temporal contiguity of color slots allocated to the same synthesized color primary.

16. The solid state light (SSL) based projection display system of claim 8 wherein:

the pulse width modulation (PWM) block is coupled to receive 1-bit fields specifying each image pixel on/off state, a color slot synchronization signal and a digital control word specifying the number of color slot cycles to apply the image pixel on/off state 1-bit fields to control the reflective states of each of the pixels; and

the hierarchical multiplexing functional block inserts a black primary by turning off all of the SSL devices during the color slots allocated to any of the synthesized color primaries associated with 1-bit fields comprising a zero value for each of the image pixels.

17. The solid state light (SSL) based projection display system of claim 2 wherein the hierarchical multiplexing functional block carries out three levels of processing whereby;

in the first processing level, referred to as gamut control level, simultaneous duty cycles of each of the SSL devices required to synthesize a target gamut are computed by mapping chromaticity and brightness values of native color primaries of the SSL devices, provided by an external input, to chromaticity and brightness values of target gamut color primaries, provided by an external input;

in the second processing level, referred to as white point control level, the simultaneous duty cycles of the SSL devices computed in the first processing level are modified to incorporate the chromaticity and brightness values of the required white point provided by the external input; and

, in the third processing level, referred to as brightness control level, the simultaneous duty cycles of the SSL devices computed in the second processing level are further modified to incorporate required adjustments in brightness of the display system white point provided by the external input.

18. The solid state light (SSL) based projection display system of claim 17 wherein the hierarchical multiplexing functional block is comprised of two processing modules whereby:

in the first processing module of each level, referred to as the temporal modulation module, the simultaneous duty cycles of the SSL devices required to synthesize the target gamut are computed; and

in the second processing module, referred to as the brightness module, the computed simultaneous duty cycles of the SSL devices are modified to synthesize the display system white point brightness.

19. The solid state light (SSL) based projection display system of claim 17 wherein:

the hierarchical multiplexing functional block carries out the three levels of processing, each processing level being level independent in controlling only one property of the display system, either target gamut, white point or brightness;

each processing level is level invariant by not altering the properties of the display system that have been set at a higher processing level; and

each processing level is processing invariant with each of the processing levels using the same two processing modules, but with different inputs to impact different properties of the display system.

20. The solid state light (SSL) based projection display system of claim 17 wherein the hierarchical multiplexing functional block carries out three levels of processing wherein the gamut control and white point control levels each maximize the brightness of the display system by scaling up the computed simultaneous duty cycles of the SSL devices such that the maximum of these duty cycles is set to unit value.

21. The solid state light (SSL) based projection display system of claim 17 wherein the processing levels enable control of the display system gamut and white point brightness and chromaticity only adjusting the duty cycles of the SSL devices and without biasing or altering the image data grayscale values.

22. The solid state light (SSL) based projection display system of claim 17 wherein, because of operating the SSL devices at higher duty cycles, the processing levels enable the solid state light (SSL) based projection display system to achieve higher levels of brightness and wall-plug efficiency than display systems that use SSL devices directly in a color sequential fashion.

23. The solid state light (SSL) based projection display system of claim 1 wherein the spatial light modulator (SLM) device is of the reflective type, comprised of either a plurality of micro mirrors or a plurality of liquid crystal cells, coupled for temporal control of the reflective state of each of its pixels.

24. The solid state light (SSL) based projection display system of claim 1 wherein the color primaries defining a target gamut include at least red, green, blue cyan, magenta, and yellow.

25. The solid state light (SSL) based projection display system of claim 1 wherein:

the plurality of solid state (SSL) devices provide a multiplicity of light color primaries, each SSL device being electrically coupled to allow temporal control of an on/off state of each SSL device in each of a plurality of color slots in synchronism with the timing of the respective duty cycle; and

,

the hierarchical multiplexing functional block is coupled to accept an externally provided image frame cycle signal and generate two lower tier synchronization signals, a first conveying the timing of color slots comprising the image frame cycle, and a second conveying the timing of simultaneous on/off duty cycles of the SSL devices in each of the plurality of color slots, and to compute the simultaneous on/off duty cycles during each of the color slots of each of the light color primaries generated by the plurality of SSL devices required to synthesize each of the color primaries defining the target gamut; and

the hierarchical multiplexing functional block computes the simultaneous duty cycles during each of the plurality of color slots of each of the SSL device light color primaries required to synthesize the target white point; and

,

the hierarchical multiplexing functional block allocates a number of the color slots during the image frame cycle to a synthesized target white point sufficient to allow control of the saturation level of each of the synthesized target color primaries.

26. The solid state light (SSL) based projection display system of claim 1 incorporating the hierarchical multiplexing functional block and used in multi-projectors array (tiled) display systems to achieve color and brightness uniformity across the displayed image.

27. The solid state light (SSL) based projection display system of claim 1 wherein the hierarchical multiplexing functional block compensates for the SSL device color and brightness drifts associated with operating temperature changes and aging of the SSL devices responsive to an external input signal.