HK1159912B - Projection display system using hierarchical temporal multiplexing of primary colors - Google Patents

Description

Projection display system using hierarchical temporal multiplexing of primary colors

Technical Field

The present invention relates to the field of display systems, and more particularly to a solid state light source based display system with the present (native) color gamut that will display an image according to image data with a target color gamut.

Background

Fig. 1a illustrates a typical spatially modulated projection system. The heart of most spatially modulated color Projection systems such as micro-mirror or Liquid Crystal On Silicon (LCOS) projectors (see e.h. Stupp et al, "Projection Displays" by John Wiley and Sons ltd, 1999) is a light pipe that includes a white light lamp 110 and a color wheel 120. Color wheel 120 typically contains three different types of filters for selectively passing the spectra of the red, green, and blue { R, G, B } primary colors. More recently, the color wheel also provides a fourth transparent filter (clear filter) selectively used to reproduce a predefined set of colors, in particular for the gray colors (see us patent No. 6,910,777). The four primary color system is similar to the CMYK color system of a printer and results in higher brightness and contrast specifications. This concept has been generalized to provide five or more primary colors to enhance the reproduced color gamut (see U.S. patent nos. 5,526,063 and 6,769,772).

However, in all of these display systems, only one of the color primaries (e.g., red, green, or blue) may be turned on at any particular instance of time. Thus, the color properties of the display system are completely specified by the chromaticity and luminance properties of the color filters used in the color wheel 120 (see Jansen et al, "Visible Laser and Laser Array Sources for Projection Displays", Proc. of SPIE Vol. 6135, 2006). For example, the color gamut of a display system cannot be changed to match a predefined standard color gamut. As a result, display device performance depends greatly on the quality of the color primary filters used on the color wheel 120 and how close these primaries are to predefined standard or target gamut color primaries in terms of their chromaticity. This can be a serious limitation, especially since such a number of standards are defined and redefined at a much faster rate today.

Recently, the projection industry, like any other display industry, has been driven to produce compact, low power, high lifetime projectors without sacrificing display quality. This witnesses the advent of projectors illuminated by Solid State Light (SSL) sources such as Light Emitting Diodes (LEDs) and Laser Diodes (LDs) (see us 7,101,049 and us 7,334,901, the disclosures of which are incorporated herein by reference). SSL sources can provide bright and saturated colors with orders of magnitude longer lifetimes. Fig. 1b illustrates a spatially modulated projection system using an SSL source 140. Each of the color primaries in the light pipe of the Projection system illustrated in fig. 1b is generated by SSL 140 comprising a single SSL device or an Array of SSL devices of a particular color (see U.S. patent nos. 7,101,049, 7,210,806 and 7,334,901 and Jansen et al, "Visible Laser and Laser Array Sources for Projection Displays", proc. of SPIE vol. 6135, 2006). Furthermore, because the plurality of primary colors are provided by the plurality of light sources, the lightpipe need not include any color wheels. The most important features of the projection system architecture illustrated in fig. 1b in the context of the present invention are: unlike projectors with a bulb and color wheel, in projectors with multiple SSLs, such as the projection system architecture illustrated in fig. 1b, more than one color primary can be switched on simultaneously as described in the prior art (see U.S. patent No. 7,334,901). Furthermore, unlike arc lamps used in most common projection systems, such as that illustrated in fig. 1a, which typically require tens of seconds to turn on, SSL can be turned on and off in much less than one microsecond.

In a conventional spatially modulated projector such as that illustrated in fig. 1a, the color properties of the display can only be manipulated in a limited way, since they are completely specified by the physical properties of the color filters. For example, to match a display system color gamut to a predefined standard such as NTSC 210 or HDTV 220 illustrated in fig. 2 (which shows various color gamuts plotted in the (u ', v') chromaticity color space), white point or luminance is an important performance parameter for any projection-based product in the display market. However, the color gamut generated by a conventional spatially modulated projector such as that illustrated in fig. 1a is defined by its chromaticity coordinates of the red, green and blue filters and cannot be changed without changing the color filters 120 or the light bulb 110. Typically, the white point of a conventional spatially modulated projector such as that illustrated in fig. 1a can be varied only in a limited way by biasing the displayed image pixel gray scale value of each color primary at the expense of reduced contrast, dynamic range, power-conversion efficiency (wall-plug efficiency) and overall realized brightness. Furthermore, the controls for changing these properties are often not independent of each other, resulting in a very difficult calibration procedure that will suffer from convergence problems, especially if multiple properties such as brightness and white point are being optimized together.

To ensure that the display system conforms to color property standard parameters (such as color gamut, brightness, and white point), the display industry must comply with strict quality measurements when manufacturing the light source 110 and the color filter 120. For example, if the color gamut resulting from color filter 120 does not encompass NTSC gamut 210, sophisticated gamut mapping methods need to be utilized and may still not provide the required visual quality when using a wider color gamut light source such as SSL source 140 as illustrated in fig. 2. As illustrated in fig. 2, the color gamut 250 and 260 provided by the SSL source 140 is typically much wider than the color gamut of typical commercial display systems such as NTSC 210 or HDTV 220. When the native gamut of the display system is much wider than the target gamut, such as when the SSL-based projection display system architecture illustrated in fig. 1b is used with the target of a commercial display color gamut, such as NTSC 210 and HDTV 220, special color mapping techniques are utilized to limit the native gamut of the display system to the target gamut. In addition to wasting the potentially higher luminous flux provided by the typically wider color gamuts 250 and 260 of the SSL sources, these techniques are often severely nonlinear and often require custom adaptations for each particular SSL device.

Disclosure of Invention

The hierarchical multi-color primary multiplexing system of the present invention takes advantage of the ability of multiple color primaries to operate (on-cycle) simultaneously (see U.S. patent No. 7,334,901) provided by an SSL-based projection display system to remove all of these rigidities. Using the present hierarchical color primary multiplexing system, a display system can be easily provided that conforms to the standard target gamut, white point, and brightness for a variety of SSL sources that may not strictly adhere to the predefined standard. Furthermore, the present hierarchical color primary multiplexing system can also be used to maximize display system capabilities, particularly brightness and power conversion efficiency, while fully complying with desired target color gamut and white point specifications.

At the heart of many projection display systems are Spatial Light Modulators (SLMs), such as micromirrors and LCOS devices (see U.S. patent nos. 5,535,047 and 4,596,992). In projection systems such as those illustrated in fig. 1a and 1b that use reflective-type SLM devices, such as micro-mirror or LCOS devices, the reflective state of each SLM device pixel that forms a digital image can be set digitally based on the desired on/off state of each pixel of the pixel. The projected image is formed by spatially sequentially modulating each display system color primary using an SLM device having image pixel gray scale data for each color primary. Pixel gray scale data for each color primary, which is typically expressed as a multi-bit word, is typically converted to a serial bit stream using Pulse Width Modulation (PWM) techniques. These PWM bits are used to set the on/off state of the SLM device pixels. Typically, the digital image data associated with each color primary is sequentially modulated in a time multiplexed manner by the SLM device. This temporal multiplexing of each primary color in conjunction with PWM techniques is used to create a spatially modulated 1-bit plane for each color primary, which is loaded into the SLM device to set the on/off state of each of its pixels to express different gray scale values for each image pixel color primary (see U.S. patent No. 5,280,277). However, when an SSL source is used in an architecture such as that shown in fig. 1b, the color primaries generated by the SSL source will typically have different chromaticity characteristics than the color gamut required by most commercial display systems as illustrated in fig. 2. As a result, conventional temporal multiplexing of the native color primaries of these display systems (meaning the native color primaries generated by the SSL device) cannot be used. Furthermore, as explained previously, the color gamut mapping schemes currently used in SSL-based projection systems are inflexible and inefficient. It is therefore an object of the present invention to describe a hierarchical multi-color temporal multiplexing system that can be used in SSL-based projection systems to improve the color quality and stability and efficiency of the display system.

Drawings

The present invention is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings in which like reference numerals refer to similar elements.

Fig. 1a illustrates the light path of a color wheel based SLM projector.

Fig. 1b illustrates the optical path of an SSL-based SLM projector.

Fig. 2 illustrates a typical target gamut in relation to the color gamut capability of an SSL device.

Fig. 3 illustrates a block diagram of a hierarchical time multiplexed SSL-based SLM projector incorporating the present invention.

Fig. 4 illustrates an operational timeline of a hierarchical time multiplexed SSL-based SLM projector incorporating the present invention.

Detailed Description

Preferred embodiments of the present invention provide apparatus, methods and systems for hierarchically multiplexing the native color primaries of an SSL-based display system in order to improve the color quality and stability and efficiency of the display system. This object is achieved by exploiting the high speed on/off switching capability of the SSL device and the possible running simultaneity of the different SSL primaries through the following steps: the native color primaries of the SSL device are multiplexed hierarchically to synthesize a set of new color primaries, which are then time multiplexed to create a spatial color field to be modulated by the SLM device to create the projected image. In a first level of the hierarchy, SSL device native primaries are simultaneously time multiplexed to allocate appropriate proportions of the different SSL native primaries to create a set of composite color primaries. Each composite color primary is thus generated by a high-speed, simultaneously time-multiplexed pattern of SSL native color primaries. In a second level of the hierarchy, each of these simultaneously multiplexed patterns is treated as a single time multiplexed block of SSL native color primaries, meaning the new composite color primaries. These simultaneous time multiplexed blocks of SSL native color primaries are then further time multiplexed together to create a particular white point, which will be used to represent the gray values of the digital image pixels relative to that particular white point. The time-multiplexed blocks of SSL native color primaries thus created in the second level may then be scaled (scale) in a third level of the hierarchy to increase the brightness of the display system with the increased luminous flux due to the simultaneity of the native SSL primaries.

Additional objects and advantages of various aspects of the present invention will become apparent from the following detailed description of preferred embodiments thereof, which proceeds with reference to the accompanying drawings. In this regard, reference in the following detailed description of the invention to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of the phrase "in one embodiment" in various places in the detailed description are not necessarily all referring to the same embodiment.

A hierarchical multi-color primary time multiplexing system for use in an SSL-based projection display system is described herein. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to one skilled in the art that the present invention may be practiced with different specific details. In other instances, structures and devices are shown in block diagram form in order to avoid obscuring the invention.

The hierarchical multi-color primary time multiplexing system described herein is illustrated in fig. 3 in the context of a projection display system in the form of a functional block diagram. Similar to the SSL-based projection system illustrated in fig. 1b, a projection system 300 incorporating the hierarchical multi-color primary time multiplexing system of the present invention comprises an SLM device 310 illuminated by a set of SSL devices 322, 324 and 326, each SSL device 322, 324 and 326 providing one of the native color primaries of the projection system 300. The light generated by the set of SSL devices 322, 324 and 326 is collimated by illumination optics 330, combined and then forwarded and coupled onto the optical surface of SLM device 310. The coupled light is then spatially modulated by SLM device 310 and then magnified to form a display projected image 350 by projection optics 340. The core of the operation of the projection system 300 incorporating the hierarchical multi-color primary time multiplexing system of the present invention is the hierarchical multiplexing function block 360, which hierarchical multiplexing function block 360 generates a high speed on/off signal 365 that controls the on/off duty cycle of the SSL devices 322, 324 and 326 and provides the PWM modulation function block 390 with display image data expressed as composite color primaries. The PWM modulation function 390 converts the display image data provided by the hierarchical multiplexing function 360 into spatially modulated 1-bit planes, which are then coupled into the SLM device 310 to control the on-state of each of its pixels.

A timeline of the operation of the hierarchical multiplexing function 360 is illustrated in fig. 4. Image data expressed in terms of a target color gamut color primary, such as NTSC 210 or HDTV 220 illustrated in fig. 2, will be provided to the hierarchical multiplexing functional block 360 as an image data input 361, which image data input 361 will typically incorporate an image frame periodic signal plus a number of multi-bit words, each multi-bit word expressing a grayscale value for each color primary of the target color gamut. Digital inputs 362 and 363 are also provided as one time input to the hierarchical multiplexing function block 360, the digital inputs 362 and 363 specifying the color coordinates of the SSL devices 322, 324 and 326 in the (u ', v') or (x, y) color space and the color coordinates of the target gamut color primaries, respectively. Based on the values of the digital inputs 362 and 363, the hierarchical multiplexing function block 360 will calculate the simultaneous duty cycle of each SSL device 322, 324 and 326 required to synthesize the target gamut color primaries as specified by the external input 363. The calculated simultaneous duty cycles of the SSL devices 322, 324 and 326 represent the level of SSL device simultaneity required for synthesizing the target gamut color primaries. The calculated simultaneous duty cycles are used to create a timing signal 365 that is provided to the SSL devices 322, 324 and 326 to control the simultaneous duty cycle operation of each SSL device 322, 324 and 326 during each composite color slot cycle 420 illustrated in fig. 4.

Referring to FIG. 4, an image frame 410 that would operate at either 60Hz or 120Hz in most display systems will typically be divided into a composite color slot cycle 420, the composite color slot cycle 420 representing the duration during which a spatially modulated 1-bit field will be loaded into the SLM device 310. Typically, the number of composite color slot periods 420 over the duration of the image frame 410 will be equal to the number of composite primary colors multiplied by the number of PWM bits (2)^N-1), where N represents the number of bits comprising each multi-bit word representing a grey value of a pixel of the image. Most digital image data is formatted using a target color gamut expressed in three color primaries, such as NTSC 210 or HDTV 220 illustrated in fig. 2, where image pixel grayscale values are expressed in 8-bit words, which would result in the exemplary image frame period 420 illustrated in fig. 4 comprising 765 color slot periods 420. For example, when a projection system 300 incorporating the hierarchical multi-color primary time multiplexing of the present invention is operating with a 60Hz image frame period 420, a typical duration of the composite color slot period 420 would be about 21.8 microseconds. Those skilled in the art will appreciate how to derive design parameters for image frame period 420 for display systems 300 that use a larger number of color primaries, a higher image frame period rate, and/or a higher number of bits representing the gray scale values of the image pixels.

Referring to fig. 4, the composite color slot cycle 420 is further divided into a number of SSL duty cycles 430, where the latter represent the on/off state durations of the SSL devices 322, 324 and 326. The number of SSL duty cycles 430 within each color slot cycle 420 is determined by the accuracy required in synthesizing the target gamut color primary 460 using the native color primaries 440 of SSL devices 322, 324, and 326, and by the on/off of SSL devices 322, 324, and 326The maximum value of the off-switching speed defines the upper limit. For example, if the maximum value of the on/off switching speed of the SSL devices 322, 324 and 326 is 1-MHz, which is equal to a minimum SSL duty cycle 430 of one microsecond, the synthesized color slot cycle 420 may incorporate a maximum number of 21 SSL duty cycles 430, which would allow the ability to express the synthesized target gamut color primaries 460 with less than 2.4% accuracy using the native color primaries 440 of the SSL devices 322, 324 and 326. In practice, to facilitate digital logic implementation of the hierarchical multiplexing function block 360, the number of SSL duty cycles 430 will be about 2ⁿAnd in the case of the previous example, the number of SSL duty cycles 430 within each color slot cycle 420 would be 16 cycles.

Although the diagram of fig. 4 shows a timeline of the operation of the hierarchical multiplexing function block 360 when three SSL color primaries are used to synthesize three target gamut color primaries, the principle of operation of the hierarchical multiplexing function block 360 is equally applicable when more than three SSL color primaries are used and may also be used to synthesize more than three target gamut color primaries. The most important aspect of the operation of the hierarchical multiplexing function block 360 is that the target gamut color primaries will have to be fully contained within the gamut formed by the SSL color primaries. For example, of particular interest in several applications is the use of multiple color primaries such as cyan (C), yellow (Y), magenta (M) in addition to red, green and blue and also the addition of white (K) as a color primary to adjust the saturation level of the primary color, all of which may be accomplished by embodiments of the hierarchical multiplexing functional block 360. In this case example, the target primary color would be synthesized by adjusting the simultaneous duty cycles of SSL devices 322, 324, and 326; for example, the synthesized C-primary timeslot will incorporate the least green SSL primary contribution, and similarly, the synthesized K-primary timeslot will incorporate the appropriate simultaneous contributions from all three SSL devices 322, 324 and 326 that are needed to generate the desired white of the K-primary.

In one embodiment of a hierarchical multi-color primary time multiplexed projection system 300 incorporating the present invention, except when generating the governing SSL devices 322, 324, and 326In addition to the control signals 365 for inter-multiplexing and simultaneous operation, the hierarchical multiplexing function block 360 also synchronizes the operation of the SSL devices 322, 324 and 326 with the operation of the PWM conversion function block 390. Specifically, the hierarchical multiplexing function block 360 will provide inputs 366 to the PWM conversion function block 390, the inputs 366 incorporating: (1) SYNC signal representing the timing of color slot cycle 420; (2) for each pixel of the digital image, a 1-bit value (1-bit plane) for each bit of the grayscale multibit word for each synthesized target gamut color primary; and (3) the number of color slot cycles 420 allocated for the 1-bit plane. In one embodiment of the hierarchical multiplexing functional block 360, an input 366 representing the nth significant bit of a multi-bit gray scale value for a particular color primary will incorporate a 1-bit value (0 or 1) plus 2 for that bit of each digital image pixelⁿAn allocation of one color slot cycle 420 (a digital control word that specifies the number of color slot cycles to apply the transmitted 1-bit field of image pixel on/off states to control the reflective state of each pixel). In response to the input 366, the PWM function block 390 synchronously forwards the 1-bit field value output by the hierarchical multiplexing function block 360 to the SLM device 310 during the assigned number of color slot cycle 420 durations.

The 1-bit planes associated with at least two significant bits in the gray scale multi-bit word of the synthesized target gamut green (G) primary are illustrated in fig. 4 as 472 and 474, respectively. As illustrated in fig. 4, the least significant bits of the gray value will require one color slot cycle 420 during which the hierarchical multiplexing function block 360 will assign and command to each SSL device 322, 324, and 326 the appropriate number of duty cycles 430 required to synthesize the target gamut G-primary and output these values to the SSL devices 322, 324, and 326 via interface signal 365, and will simultaneously output a 1-bit field value 472 (illustrated in fig. 4) associated with the command to the PWM function block 390 to synchronously forward the output 1-bit field value to the SLM device 310 during the assigned number of color slot cycles 420 durations, in which case the assigned number of color slot cycles 420 durations will be equal to only one color slot cycle 420 duration. Fig. 4 also illustrates an example case of the second least significant bit of the grayscale multi-bit word of the synthesized target gamut red (R) primary, in which case the hierarchical multiplexing function block 360 will assign and command to each SSL device 322, 324, and 326 the appropriate number of duty cycles 420 required to synthesize the target gamut R-primary and output these values to SSL devices 322, 324, and 326 via interface signal 365, and will simultaneously output the 1-bit field value 474 (illustrated in fig. 4) associated with the command to PWM function block 390 to synchronously forward the output 1-bit field value to SLM device 310 during the assigned number of color slot cycles 420 durations, in which case the assigned number of color slot cycles 420 durations will equal two color slot cycles 420 durations. A person skilled in the art will know how to implement the specifications outlined in the above examples for the more significant bits of the grey value of each target gamut color primary.

In another embodiment of the projection system 300 of the present invention, the hierarchical multiplexing functional block 360 will incorporate means to reduce the possible temporal speckle that may be caused by clustering the color slot cycles 420 assigned to the more significant bits of the pixel gray value. In current projection display systems using color wheels, such as that illustrated in fig. 1a, the 1-bit planes of a particular color primary are typically clustered over the duration of the color filter, which often causes significant projected image speckle and artifacts, particularly in high brightness images. This type of image speckle is typically caused by the time-multiplexed aspect of the color sequential nature associated with the color wheel and the clustering of 1-bit planes associated with the gray scale bits of each color primary. In this embodiment, the projection system 300 of the present invention incorporating the hierarchical multiplexing functional block 360 will avoid this type of color slot clustering by assigning a maximum number of contiguous color slot cycles 420 to each color primary, and will also temporally interleave the assigned color slot cycles 420 to prevent excessive proximity of the color slot cycles 420 assigned to the same composite color primary. For example, when the maximum number of contiguous color slot periods 420 is limited to 16 time slots, the hierarchical multiplexing functional block 360 will divide the number of color slot periods 420 required for a higher gray word bit than the fourth least significant bit into clusters of 16 time slots and then interleave the clusters of 16 time slots of the different composite color primaries 460 such that the resulting allocation for any single composite color primary is no greater than 16 time slots. In this example, the hierarchical multiplexing function 360 would allocate the number of color slot cycles 420 to all gray word bits up to the fourth least significant bit based on the criteria discussed in the preceding paragraph, but would allocate 2 16-slot groups for the fifth least significant bit of the gray word bits of each composite color primary 460, 4 16-slot groups for the sixth least significant bit of the gray word bits of each composite color primary 460 and 8 16-slot groups for the most significant bit of the gray word bits of each composite color primary 460, and would then interleave these 16-slot assignments such that no more than 16 slots are allocated for contiguous color slots of each composite color primary 460. This limitation on the number of contiguous color slot assignments for each composite color primary, plus having the assigned largest size set (16-slots in the case of the above example) of different composite color primaries 460 interleave will greatly reduce temporal image speckle due to the increased temporal color uniformity achieved by the increased rate of temporal multiplexing of the composite color primaries 460.

In another embodiment, to take advantage of the high speed switching capability of SSL devices 322, 324, and 326 to further improve the contrast of projection system 300, projection system 300 incorporating hierarchical multiplexing function block 360 of the present invention will examine the 1-bit fields associated with each color slot cycle 420 and will insert a black primary (BLK-primary) during these color slot cycles 420 if all of the 1-bit pixel values of their associated 1-bit fields are zero values. This capability is illustrated in fig. 4, which fig. 4 shows the four slots allocated to the synthetic R-primary, where SSL devices 322, 324 and 326 are turned off when their associated 1-bit plane 475 contains a zero value for all image pixels. Without this capability, the SSL devices 322, 324 and 326 would be on with the appropriate duty cycle during the 4 time slots assigned to the synthetic R-primary (such as in the case of the lamp-based and SSL-based projection systems illustrated in fig. 1a and 1b, respectively), but during the 4-time slot duration all SLM device 310 pixels would be in the off state, which would typically cause photons associated with the SLM device 310 to leak through the projection optics and be transmitted onto the projected image 350, which would degrade the maximum black level, which in turn would degrade the contrast level of the projected image 350. In fact, the ability of the hierarchical multiplexing functional block 360 to adaptively insert the BLK-primary when the spatial 1-bit field is zero for all pixels will reduce the photon leakage level during this type of 1-bit field and as a result will significantly improve the black level and contrast of the display system 300. In practice, this adaptive RLK-primary insertion capability of the hierarchical multiplexing functional block 360 will make the maximum black level of the display system 300 high enough to achieve a sequential contrast level of up to 100,000:1, i.e. a sequential contrast level that cannot be achieved by any current projection system.

The functional operation of the projection system 300 incorporating the hierarchical multi-color primary temporal multiplexing system of the present invention is described and the following discussion provides additional details of the design specification and the operation of its main functional blocks, namely the hierarchical multiplexing functional block 360. To achieve the capabilities outlined in the previous embodiments, the hierarchical multiplexing functional block 360 implements the following properties:

a) hierarchy independence-in each level of the hierarchy, only one property of the display system 300 (e.g., color gamut, white point, or brightness) is independently controlled. In level 1 of this hierarchy, the chromaticity mapping from the present gamut of SSL devices 322, 324 and 326 to the synthetic target gamut color primaries is modified. In level 2, the white point of the synthesis target gamut is modified. In level 3, the luminance mapping from the present gamut of SSL devices 322, 324 and 326 to the synthesis target gamut is modified.

b) Hierarchy invariance-when handling properties at the upper level of the hierarchy, properties that have been fixed in the lower level will not be changed. For example, when the white point is changed in level 2, the color gamut implemented in level 1 is not changed.

c) Process invariance-the same processing module is used in each level of the hierarchy, but with different inputs to affect different properties of the display system 300. Each level includes a temporal modulation and brightness processing module.

These properties of the hierarchical multiplexing functional block 360 provide a desired linear convergence towards a target parameter (e.g., target color gamut, white point, or luminance) and handle only one parameter at a time without affecting the other parameters, which greatly simplifies the calibration of the display system 300.

Referring to fig. 3, the processing module of the hierarchical multiplexing functional block 360 utilizes the following parameters, represented by the following reference numerals:

（a）r=(r _x ,r _y )、g=(g _x ,g _y ) And b =: (b _x ,b _y ) Chromaticity coordinates (input 362) representing the color primaries 440 of SSL devices 322, 324, and 326;

（b）L _r 、L _g andL _b indicating the full duty cycle brightness of SSL devices 322, 324 and 326 (input 362);

（c）R=(R _x ,R _y )、G=(G _x ,G _y ) And B =: (B _x ,B _y ) The chromaticity coordinates (input 364) representing the target gamut color primaries 460;

（d）L _R 、L _G andL _B represents the desired luminance of the target gamut color primary 460;

（e）W=(W _x ,W _y ) Chromaticity coordinates representing a target white point for display system 300 (input 364);

（f）L _W representing the requirements of the target white point of the display system 300Luminance (input 364); and

（g）α、βandγrepresenting the fraction of the color slot cycle 420 that is required to be allocated to each SSL device 322, 324, and 326 to achieve the desired target color gamut (input 363) and white point luminance (input 364) for the display system 300.

Note that lower case letters refer to the colors of the SSL device, upper case letters refer to the composite colors, and the brightness of all colors is subscripted by color nameLAnd (4) showing.

Level 0; calibration and initialization

The chromaticity coordinates of the SSL devices 322, 324 and 326 color primaries 440 (SSL gamut) will be measured during the initial calibration of the display system 300r、gAndband brightnessL _r 、L _g AndL _b and provides the chromaticity coordinates and luminance as input 362 to the hierarchical multiplexing function block 360 during initialization of the display system 300. Input 363 and input 364 are also provided to hierarchical multiplexing functional block 360 during initialization of display system 300, where input 363 communicates chromaticity coordinates of target gamut color primariesR、GAndBand brightnessL _R 、L _G AndL _B input 364 conveys the desired white point chromaticity coordinatesWAnd brightnessL _W . The values of inputs 362, 363, and 364 will be stored inside hierarchical multiplexing functional block 360 during initialization of display system 300 for use during subsequent operations.

And (3) processing at a layer 1: color gamut control

Externally provided chromaticity coordinate values of color primaries 440 using SSL devices 322, 324, and 326r、gAndb(input 362), the hierarchical multiplexing function block 360 determines that each SSL device 322, 324, and 326 will be turned on during each color slot period 420 to synthesize the target gamut color primariesR、GAndB(input 363) SSL duty cycle 430Number of (2)、And. Based on the total number of SSL duty cycles 430 within each color slot cycle 420 and the fractional valueα、βAndγto determine the value of each color slot cycle 420、And. For example, if each color slot cycle 420 includes 16 SSL duty cycles 430 and the valueα _G =0.1875 (which represents the fraction of the color slot period 420 allocated to the synthesized green primary during which the red SSL is switched on in order to synthesize the target gamut green primary), then. In this example, ifβ _G =0.875 (which represents the fraction of the color slot period 420 allocated to the synthesized green primary during which the green SSL is switched on in order to synthesize the target gamut green primary), then. Similarly, if in this exampleγ _G =0.0625 (which represents the fraction of the color slot period 420 allocated to the synthesized green primary during which the blue SSL is switched on in order to synthesize the target gamut green primary), then. Thus, in this example, by assigning to the synthesized green color:G) Target gamut green is synthesized by simultaneously turning on red SSL device 322 during three (3) SSL duty cycles 430, green SSL device 324 during fourteen (14) SSL duty cycles 430, and blue SSL device 326 during one (1) SSL duty cycle 430 for color slot cycles 420 of the color primaries (aG) A primary color.

Alternatively, given a specified value of the number of SSL duty cycles 430 per color slot cycle 420, such as in the previous example where each color slot cycle 420 includes 16 SSL duty cycles 430, a 4-bit Pulse Width Modulation (PWM) technique may be used, each directly according to a simultaneous time-multiplexing ratioα _G 、β _G Andγ _G to determine a value、And。

the time-multiplexed color slot 420 created in level 1 will form a synthetic primary color 460R,G,BReferring to the diagram of fig. 4, the color primary 440 of the SSL devices 322, 324 and 326 will be turned on simultaneously during these time multiplexed color slots 420r,g,bTime duration of arrival、And. Simultaneous time duration、Andwill be determined by the color processing module of the hierarchical multiplexing function block 360 and the resulting synthetic primary color 460R,G,BThe luminance of will be determined in the luminance module of the hierarchical multiplexing function 360. A detailed functional description of the temporal modulation module and the luminance module of the hierarchical multiplexing functional block 360 is given below. These two modules will typically be implemented as high-speed logic as part of the hierarchical multiplexing function block 360.

Time modulation module: as explained previously, the primary color 460 is chromatic for the synthesis of a target color gamutR,G,BA color primary 440 for temporally combining SSL devices 322, 324 and 326 with a ratio { alpha, beta, gamma }, ar,g,bSuch that their combined luminous flux yields the desired target gamut color chromaticity coordinates. The equation for this time modulation synthesis is shown in equation (1) below:

（1.1）

（1.2）

（1.3）

for each synthetic color primary 460R,G,BUnknown ratio ofα,β,γSolve each of these equations independently. In order to find a target color primary (e.g., a green target gamut primary) for a particular color primaryG) Is open to the eyeα,β,γBased on color primaries 440 of SSL devices 322, 324 and 326r,g,bThe chromaticity coordinates of (1.2) are used. Color primary 440 generated by SSL devices 322, 324 and 326r,g,bWould have to be combined in this manner to produce a target synthetic primary color 460R,G,BChroma of: (x,y) And (4) coordinates. For example, to synthesize a green target gamut primaryGIs composed ofr _x ,g _x ,b _x The x-coordinate ratios of the SSL devices 322, 324 and 326 expressed have to be added to the green target gamut x-coordinateG _x . Similarly, y-coordinater _y ,g _y ,b _y The ratios of which must be added to the target gamut y-coordinateG _y . Finding these ratios requires solving forα _G ,β _G ,γ _G The equation set (2).

（2.1）

（2.2）

（2.3）

Similar sets of equations may be used to find a ratio hard for the red and blue target gamut primaries, respectivelyα _R ,β _R ,γ _R Anα _B ,β _B ,γ _B }。

When calculated according to equation (1)α,β,γThe ratios, when temporally combining sets of SSL devices 322, 324 and 326 with equal luminance, will yield the target gamut primary chromaticity point. Since the brightness of each SSL device is likely to be different, the ratio toneα,β,γMust be scaled to account for the distance fromL _r ,L _g ,L _b Denotes the difference in brightness of the SSL devices 322, 324 and 326. For example, to take into account the difference in luminance of the SSL devices 322, 324 and 326, the ratio of the primary color resulting in the green target gamut would have to be modified according to equation (3) belowα _G ,β _G ,γ _G }。

（3.1）

（3.2）

（3.3）

A similar set of equations may be used for the red and blue target gamut primaries. Note that for generating the green target gamut primary G, the valueβ _G General will ratioα _G Andγ _G much larger because G is much closer to G and far from r and b. Similarly, to generate the red target gamut primary R, the valueα _R General will ratioβ _R Andγ _R much larger because R is much closer to R and far from g and b. Similarly, to generate the blue target gamut primary B, the valueγ _B General will ratioα _B Andβ _B much larger because B is much closer to B and far from r and g.

As explained before, in order to use in practice the time ratioα,β,γThe ratio must be converted to an actual time value. The conversion will be done by dividing the ratioα,β,γNormalize to the maximum of these three values and then multiply the resulting value by the size of the color slot 420 expressed in terms of the number of SSL duty cycles 430t _slot To complete. The result is that each SSL device 322, 324, and 326 within the color slot 420 will have to be turned on to synthesize each target gamut primary 460R,G,BThe number of SSL duty cycles 430. For example, to synthesize a green target primary colorGThe simultaneous on-time duty cycle of the SSL devices 322, 324 and 326 may be calculated as shown in equation (4) below, which is bound by-, , Represents it.

（4.1）

（4.2）

（4.3）

Red colourRPrimary color and blue color of targetBTemporal multiplexing ratio for synthesis of a target primary colorα,β,γWill be specified by a similar set of equations. Will be provided withAt the same timeTime multiplexing ratioα,β,γNormalization to the maximum of the three values as specified in equation (4) is intended to be carried out using a color primary 440r,g,bSimultaneity in order to maximize the brightness of the display system 300. The normalized constraint set forth in equation (2.3) will typically set the temporal multiplexing ratio ∑ toneα,β,γSuch that the sum of these three ratios is set to a unity value, which presupposes a color primary 440r,g,bIs sequentially time-multiplexed and is virtually free of color primaries 440r,g,bThe simultaneity of. On the other hand, equation (4) is prepared by further normalizing the time-multiplexing ratioα,β,γ} to incorporate a color primary 440. figr,g,bSimultaneity to modify these ratios to simultaneous time multiplexing ratios. As a result of the normalization of equation (4), each time multiplexing ratioα,β,γThe relative values of these ratios will be scaled up such that the maximum of these ratios is set to unity. The equation (4) yields the effect thatThus, for example, in assigning to a synthetic green color primaryGWill turn on all SSL devices 322, 324 and 326 simultaneously for the duration of the color slot 420, although each SSL device is at a different time duty cycle, the present green primary colorgWill be turned on for the entire duration of the color slot 420. As a result, the combined luminous flux of all SSL devices 322, 324 and 326 will contribute to the resulting luminous flux of each synthetic primary color. In contrast, the native color primary 440, if generated directly using SSL devices 322, 324, and 326 in a color sequential mannerr,g,bAs in the case of the SSL-based projection system shown in fig. 1b, only the luminous flux of the individual SSL devices will contribute to the brightness of the display system.

In addition to increasing the achievable brightness of the display system 300, the native color primary 440 described in the previous paragraph is a large volumer,g,bWill result in the SSL devices 322, 324 and 326 being operated at a high level of duty cycle combined with a lower level of peak power in order to achieve the desired level of white point brightness specified by the external input 364, which in turn will result in a net increase in the electrical energy conversion efficiency of the display system 300 (the SSL devices characteristically exhibit higher efficiency when operated at higher duty cycles and lower peak power levels).

The simultaneous on-time duty cycle of the SSL devices 322, 324 and 326 given by equation (4) is a temporary value and, as will be explained in the discussion below, will have to be adjusted to account for the desired luminance and chromaticity of the white point of the display system 300 based on the values specified by the external input 364.

Brightness module: in level 2 of the hierarchical multiplexing functional block 360, the system white point is set to the value specified by the external input 364. When the luminance module calculates each synthetic target primary color 460 created in level 1R,G,BBrightness of, initialize level 2. As shown in the following equation (5), a time ratio ∑ as set forth using equation (3)α,β,γ} to calculate three synthetic primaries 460 created in level 1R,G,BObtained brightness of each ofDegree, which is formed byL _R 、L _G 、L _B Represents it.

（5.1）

（5.2）

（5.3）

And (2) level: white point control

The same temporal modulation module used in level 1 will also be used in level 2, but applied to synthesize the target gamut primary 460R,G,BRather than the color primaries 440 of the SSL devices 322, 324 and 326r,g,b}. In level 2, a single white gamut point will be composited instead of compositing the three individual color primary gamut points of the target gamut. As previously described, it is necessary to determine the proportion of the required time duration of the new primary color to create the desired white point. The same luminance calculation is then used to calculate the luminance of the resulting white point and hence the luminance of the display system 300.

Time modulation: this is similar to the temporal modulation in level 1, but this time the module uses the chromaticity coordinates of the synthetic target primary 460R,G,BGreat and brightnessL _R ,L _G ,L _B }. At this level, the primary colors 460 will be time multiplexed sequentially to produce an external outputAnd 364 target white point chromaticity and luminance. To achieve this, the color primaries 440 of the SSL devices 322, 324 and 326 would have to be modified in such a way that the white point chromaticity W specified by the external input 364 would be achievedr,g,bThe contribution ratio of.

For creating a target white point W, three target gamut synthesis primary colorsR,G,B} 460 will have to be held at a ratioα _W ,β _W ,γ _W Combine to produce a desired white point specified by the external input 364 when sequentially time multiplexed. The following equation (6) is a great deal according to the synthetic gamut primariesR,G,BExpresses the target white point chromaticity.

（6）

Determining the ratio needed to create a white pointα _W ,β _W ,γ _W Needs to be mapped to three unknownsα _W ,β _W ,γ _W Solve equation (6). Similar to the foregoing, three equations are used based on the chromaticity coordinates of the target gamut primaries. Chromaticity with which the target gamut primaries have to produce a white point: (x,y) The manner of the coordinates is combined. Is formed byR _x ,G _x ,B _x The ratios of the x-coordinates of the target gamut primaries expressed have to be added to the x-coordinate of the white pointW _x . Similarly, y-coordinateR _y ,G _y ,B _y The ratios of which must be added to the y-coordinate of the white pointW _y . Finding these ratios requires a mapping toα _W ,β _W ,γ _W Solving the equation set (7).

（7.1）

（7.2）

（7.3）

After solving the above equation set (7), the resulting ratioα _W ,β _W ,γ _W Will need to be scaled up in order to take into account the target gamut primary color(s) synthesized in level 1 and given by equation (5-R,G,BRealized brightness of } -L _R ,L _G ,L _B The difference is as shown in equation (8).

（8.1）

（8.2）

（8.3）

Once the synthesis target gamut has been determined using the sub-groups of equations (7) and (8)R,G,BOfSequence ofTime multiplexing ratioα _W ,β _W ,γ _W To create a desired target white pointW(specified by external input 364), then the native color primaries of SSL devices 322, 324 and 326 created at level 1 would need to be modifiedr,g,bOfAt the same timeTime multiplexing ratioα,β,γTo achieve these ratios. To achieve this, the chinese book has to be made at an appropriate white point ratio according to equations (9) to (11)α _W ,β _W ,γ _W Great for synthesizing each target gamut color primary colorR,G,BWhat is neededAt the same timeThe set of temporal multiplexing ratios alpha, beta, gamma is scaled.

（9.1）

（9.2）

（9.3）

（10.1）

（10.2）

（10.3）

（11.1）

（11.2）

（11.3）

Specified by equations (9) to (11)At the same timeTime multiplexing ratioα,β,γThe set is the final adjusted time ratio required to synthesize the white point luminance and chrominance specified by the external input 364. For each synthetic target gamut primary colorR,G,BWill beAt the same timeTime multiplexing ratioα,β,γThese final values of } are converted into a simultaneous on-time duty cycle of each SSL device 322, 324 and 326, which is bound by-, , }、{, , An, , Represents, as illustrated in equation (4).

Brightness module: is mapped to a target gamut primary color to be synthesized in level 1R,G,BLuminance of } ofL _R 、L _G AndL _B similarly to the case of establishing level 2, it would be necessary to know the white dots synthesized in level 2WTo establish level 3. As shown in equation (12), the sequential time ratio will be usedα _W ,β _W ,γ _W And byL _R ,L _G ,L _B Is calculated by the achieved luminances of the target gamut primaries indicated byL _W The brightness of the white point indicated.

（12）

And (3) level: brightness control

In level 3 of the hierarchical multiplexing functional block 360, a sequential temporal ratio can be prepared by scalingα _W ,β _W ,γ _W Continuously adjust the white point brightness of the display system 300. The brightness calculated at the end of level 2 can be scaledL _W To adjust the brightness of the display system 300 to any desired brightnessL _Ref A reference luminance is indicated which can then be specified by an external input 364. To achieve this, the scale factor would have to be calculated as shown in equation (13)S。

（13）

The scale factor specified using equation (13)SThe simultaneous time multiplexing ratio from level 1 will be scaledα _R ,β _R ,γ _R }、{α _G ,β _G ,γ _G Anα _B ,β _B ,γ _B To produce a desired target brightness valueL _Ref . For example, equation (14) shows how the simultaneous temporal multiplexing ratio of the green primaries will be scaled to produce the desired target luminance valueL _Ref . The equations for the red target gamut primaries and the blue target gamut primaries are similar.

（14.1）

（14.2）

（14.3）

As is apparent from the foregoing description of the functional details of each level of the hierarchical multiplexing functional block 360 of the display system 300 of the present invention, the hierarchical multiplexing functional block 360 enables strict real-time control of the color gamut and white point luminance and chromaticity of the display system 300 by changing the simultaneous temporal multiplexing parameters of the SSL devices 322, 324 and 326 and not biasing or in any way altering the grayscale values of the image data. This capability is critical to achieving the highest color and brightness uniformity in a tiled multi-projector display system (see U.S. patent No. 7,334,901). In these systems, external inputs 363 and 364 will be provided by external blocks to the hierarchical multiplexing block 360, the function of which is to first sense the color and brightness of each of the multiple projectors comprising the tiled multi-projector display system and second generate inputs 363 and 364 for each projector that will achieve and maintain a desired level of color and brightness uniformity across all of the multiple projectors comprising the tiled multi-projector display system (see U.S. patent No. 7,334,901).

By the inventionThe foregoing ability to control the color gamut and white point luminance and chromaticity of the display system 300 in real time implemented by the hierarchical multiplexing functional block 360 can also be used to compensate for color and luminance shifts typically associated with operating temperature changes and SSL device aging (see U.S. patent No. 7,334,901). In this type of application, a light sensor coupled to detect the color and luminance generated by SSL devices 322, 324 and 326 and coupled into SLM device 310 (see us patent No. 7,334,901) will generate an external input 362, which external input 362 will in turn be used by hierarchical multiplexing function 360 in order to adjust the simultaneous time multiplexing parameters of SSL devices 322, 324 and 326, as explained in the previous paragraph, in order to compensate for changes in the color and luminance of SSL devices 322, 324 and 326 and maintain the luminance and chrominance of the composite primary colors. In this case, the hierarchical multiplexing functional block 360 will be prepared by changing the simultaneous time multiplexing ratio-α,β,γThe value of (as explained before) to adjust the mapping of the present primaries of SSL devices 322, 324 and 326 to the primaries of the target gamut specified by external input 363, so as to maintain the luminance and chrominance of the synthetic primaries at the values specified by external input 362.

In summary, the SSL-based projection display system 300 of the present invention incorporates a hierarchical multiplexing function block 360, the hierarchical multiplexing function block 360 achieves the following operational and performance advantages through simultaneous time multiplexing of SSL device operational duty cycles synchronized with the time operation of the SLM device 310:

1. the ability to synthesize any desired target gamut including a plurality of synthetic primaries that are fully contained within the native gamut formed by the color primaries of the SSL device;

2. the ability to selectively incorporate white primaries and/or black primaries within a composite gamut in order to improve the color saturation and contrast levels of the display system;

3. the ability to selectively interleave the time slot assignments of the composite primaries in order to reduce projected image speckle and artifacts that may be caused by adjacent sequential time slots of the same color primary;

4. the ability to control the mapping from the SSL device's native gamut to the target composite gamut in real-time in order to compensate for possible variations in the SSL device's native gamut and maintain the stability of the target gamut luminance and chromaticity;

5. the ability to synthesize any desired target white point luminance and chromaticity without biasing or altering the image data gray scale values;

6. the ability to strictly control white point luminance and chromaticity of a display system in real time by changing the SSL device operating duty cycle while time multiplexing and not biasing or altering the image data gray scale values;

7. the ability to achieve higher levels of brightness and power conversion efficiency than display systems using SSL based on conventional color sequential schemes; and

8. the ability to achieve higher contrast, dynamic range, power conversion efficiency, and overall brightness than display systems that rely on manipulating the image grayscale values to adjust their gamut or color point characteristics (whether lamp-based or SSL-based display systems).

In the foregoing detailed description, the invention has been described with reference to specific embodiments thereof. However, it will be apparent that: various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention. Accordingly, the design details and drawings are to be regarded as illustrative rather than restrictive. Those skilled in the art will recognize that portions of the present invention may be implemented differently than the embodiments described above for the preferred embodiments. For example, those skilled in the art will recognize that the SSL-based projection display system 300 incorporating the hierarchical multiplexing function block 360 of the present invention may be implemented with many variations for: the number of SSL devices used, the number of color primaries associated with the SSL devices used, the specific design details of the projection optics 340, the specific design details of the illumination optics 330, the specific design details of the PWM conversion block 390 and its interface with the SLM device 310, the specific implementation details of the hierarchical multiplexing function block 360, and the specific design details of the coupling of the external interfaces 362, 363 and 364. It will further be appreciated by those skilled in the art that many changes may be made to the details of the above-described embodiments of the invention without departing from the underlying principles thereof. The scope of the invention should, therefore, be determined only by the following claims.

Claims (29)

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

a plurality of pixel illumination devices for illuminating a plurality of pixels in each of a plurality of color timeslots, each pixel having a digitally controllable on/off state, the pixel illumination devices using solid state light sources;

a projection optics optically coupled to magnify an image generated by the plurality of digitally controllable pixels;

a Pulse Width Modulation (PWM) block coupled to the pixel illumination device to control an on/off state of each digitally controllable pixel; and

a hierarchical multiplexing functional block coupled to receive digital image data and a number of other external inputs and to provide control and synchronization signals to the plurality of pixel illumination devices and the Pulse Width Modulation (PWM) block that compensates for variations in native color gamut of the solid state light source with changes in operating temperature and aged color and brightness offsets in response to external input signals to cause the plurality of digitally controllable pixels to generate an image in a target color gamut of the display system in response to the image data;

wherein the hierarchical multiplexing functional block performs three levels of processing, thereby:

in a first processing level, called gamut control level, the simultaneous on/off duty cycle required for synthesizing the target gamut is calculated for each pixel lighting device by mapping the chromaticity and luminance values of the native color primaries of the pixel lighting device provided by the external input to the chromaticity and luminance values of the target gamut color primaries provided by the external input;

in a second processing level, referred to as a white point control level, modifying the simultaneous on/off duty cycles of the pixel lighting devices calculated in the first processing level to incorporate the chromaticity and luminance values of the desired white point provided by an external input; and

in a third processing level, referred to as a brightness control level, the simultaneous on/off duty cycles of the pixel illumination devices calculated in the second processing level are further modified to incorporate brightness adjustments of the display system white point provided by the external input.

2. The solid state light based projection display system of claim 1 wherein the hierarchical multiplexing functional block is coupled to accept an externally provided image frame cycle signal and generate two lower level synchronization signals, a first synchronization signal conveying timing of color slots comprising the image frame cycle and a second synchronization signal conveying timing of simultaneous on/off duty cycles of digitally controllable pixels in each of the plurality of color slots.

3. The solid state light based projection display system of claim 2 wherein the plurality of pixel illumination devices provide a multiplicity of light color primaries for each pixel, each pixel illumination device being electrically coupled to receive a time control signal for temporally controlling the on/off state of each pixel of the pixel illumination device in each color time slot in synchronization with the timing of a respective on/off duty cycle.

4. The solid state light based projection display system of claim 3 wherein the pixel illumination devices operate simultaneously for different light color primaries and with different on/off duty cycles during different color slot periods.

5. The solid state light based projection display system of claim 4 wherein said hierarchical multiplexing functional block calculates a simultaneous on/off duty cycle required to synthesize a target white point during each of said plurality of color time slots of each pixel luminaire color primary.

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

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

the plurality of pixel illumination devices each providing one of a plurality of light color primaries, each pixel illumination device being electrically coupled to receive a time control signal for temporally controlling an on/off state of each pixel illumination device in each color time slot in synchronization with a timing of a respective on/off duty cycle; and

the hierarchical multiplexing functional block is coupled to provide the on/off state time control signals to the pixel lighting apparatus in synchronization with providing the digital control words of the Pulse Width Modulation (PWM) block with a 1-bit field specifying the on/off state of each digital image pixel and data specifying a number of color slot periods to apply the transmitted 1-bit field.

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

the plurality of pixel illumination devices providing a plurality of light color primaries, each pixel illumination device being electrically coupled to allow on/off duty cycles of the pixel illumination devices to be controlled in time in each color time slot in synchronization with the timing of the respective on/off duty cycles;

wherein the hierarchical multiplexing functional block is coupled to accept external signals specifying luminance and chromaticity in a solid state light source gamut for each light color primary generated by the plurality of pixel illumination devices;

to accept an external signal specifying the luminance and chromaticity of a color primary defining a target color gamut of the display system; and

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

9. The solid state light based projection display system of claim 8 wherein the target color gamut is completely contained within the solid state light source color gamut.

10. The solid state light based projection display system of claim 8 wherein the target color gamut is the NTSC or HDTV display system color gamut standard.

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

the plurality of pixel illumination devices providing a plurality of light color primaries, each pixel illumination device being electrically coupled to allow on/off state control of each pixel illumination device in time in synchronization with the timing of a respective on/off duty cycle in each of a plurality of color time slots; and

wherein the hierarchical multiplexing functional block is coupled to calculate, during each color time slot of each light color primary generated by the plurality of pixel lighting devices, a simultaneous on/off duty cycle required to synthesize each color primary defining the target color gamut.

12. The solid state light based projection display system of claim 11 wherein the hierarchical multiplexing functional block assigns a number of color slots to each composite color primary within each image frame period.

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

wherein the Pulse Width Modulation (PWM) block is coupled to receive a 1-bit field specifying an on/off state of each image pixel, a color slot synchronization signal, and a digital control word specifying a number of color slot cycles to apply the image pixel on/off state 1-bit field to control the state of each pixel; and

wherein the allocated number of color slots conveys values of multi-bit words of gray scale values for each image pixel in the digital image data that uses the 1-bit field.

14. The solid state light based projection display system of claim 8 wherein the color time slot includes a number of pixel illumination device on/off duty cycles to synthesize the target gamut color primaries.

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

the hierarchical multiplexing function interleaves the color slots assigned to the target gamut color primaries to reduce temporal speckle that would be caused by excessive temporal adjacency of the color slots assigned to the same composite color primaries.

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

the Pulse Width Modulation (PWM) block is coupled to receive a 1-bit field specifying an on/off state of each image pixel, a color slot synchronization signal, and a digital control word specifying a number of color slot cycles to apply the image pixel on/off state 1-bit field to control a reflective state of each pixel; and

the hierarchical multiplexing functional block inserts the black primary by turning off all pixel illuminators during the color time slots assigned to any composite color primary associated with the 1-bit field including a zero value for each image pixel.

17. The solid state light based projection display system of claim 1 wherein the hierarchical multiplexing functional block comprises two processing modules whereby:

calculating, in a first processing module, called temporal modulation module, of each level, a simultaneous on/off duty cycle of the pixel lighting devices required for synthesizing the target color gamut; and

in a second processing module, referred to as a luminance module, the calculated simultaneous on/off duty cycles of the pixel illumination devices are modified to synthesize a display system white point luminance.

18. The solid state light based projection display system of claim 1 wherein:

the hierarchical multiplexing functional block performs three processing levels, each processing level being hierarchically independent in controlling only one property of the display system, namely a target color gamut, white point or luminance;

each of the second and third processing levels is level-invariant by not altering a property of the display system that has been set at a higher processing level; and

each processing level is process invariant, wherein each processing level uses the same two processing modules, but wherein different inputs are used to affect different properties of the display system.

19. The solid state light based projection display system of claim 1 wherein the hierarchical multiplexing functional block performs three processing levels, wherein the gamut control and white point control levels each maximize the brightness of the display system by scaling up the calculated simultaneous on/off duty cycles of pixel illuminators such that the largest of these on/off duty cycles is set to the maximum value of the solid state light based projection display system.

20. The solid state light based projection display system of claim 1 wherein the processing levels enable control of display system color gamut and white point luminance and chromaticity only by adjusting on/off duty cycles of pixel illuminators and not biasing or altering image data gray scale values.

21. The solid state light based projection display system of claim 1 wherein the processing hierarchy enables the solid state light based projection display system to achieve higher levels of brightness and power conversion efficiency than display systems that directly use solid state light devices in a color sequential manner due to operating pixel illumination devices with higher on/off duty cycles.

22. The solid state light based projection display system of claim 1 wherein the pixel illumination device comprises a solid state light source and a reflective type imaging device comprising a plurality of micro mirrors or a plurality of liquid crystal cells coupled to temporally control the reflective state of each of its pixels.

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

24. The solid state light based projection display system of claim 1 wherein:

the plurality of pixel illumination devices providing a plurality of light color primaries, each pixel illumination device being electrically coupled to allow on/off state control of each pixel illumination device in time in synchronization with the timing of a respective on/off duty cycle in each of a plurality of color time slots; and

the hierarchical multiplexing functional block is coupled to accept an externally provided image frame cycle signal and generate two lower level synchronization signals, a first synchronization signal conveying the timing of color time slots comprising an image frame cycle and a second synchronization signal conveying the timing of simultaneous on/off duty cycles of the pixel illumination devices in each of the plurality of color time slots, and to calculate the simultaneous on/off duty cycles required for synthesizing each color primary defining the target color gamut during each color time slot of each color primary generated by the plurality of pixel illumination devices; and

said hierarchical multiplexing functional block calculating said simultaneous on/off duty cycles required to synthesize a target white point during each of said plurality of color time slots of each pixel luminaire color primary; and

the hierarchical multiplexing function assigns a number of color slots to the synthesis target white point during the image frame period, the number of color slots being sufficient to allow control of the saturation level of each of the synthesis target color primaries.

25. The solid state light based projection display system of claim 1, used in large numbers in a multi-projector array display system to achieve color and brightness uniformity across the displayed image.

26. A method for use in a solid state light based projection display system having: a plurality of pixel illumination devices for illuminating a plurality of pixels in each of a plurality of color timeslots, each pixel having a digitally controllable on/off state, the pixel illumination devices using solid state light sources; and projection optics optically coupled to magnify an image generated by the plurality of digitally controllable pixels, the method comprising:

in a first processing level, referred to as a gamut control level, calculating the simultaneous on/off duty cycle required for synthesizing a target gamut for each pixel lighting device by mapping the chromaticity and luminance values of the native color primaries of the pixel lighting device provided by an external input to the chromaticity and luminance values of the target gamut color primaries provided by the external input and corrected for color and luminance shifts associated with operating temperature changes and aging of the solid state light sources in response to an external input signal;

in a second processing level, referred to as a white point control level, modifying the simultaneous on/off duty cycles of the pixel lighting devices calculated in the first processing level to incorporate the chromaticity and luminance values of the desired white point provided by the external input; and

in a third processing level, referred to as a brightness control level, the simultaneous on/off duty cycles of the pixel illumination devices calculated in the second processing level are modified to incorporate brightness adjustments of the display system white point provided by the external input.

27. The method of claim 26, wherein:

each processing level is level independent in controlling only one property of the display system, namely target color gamut, white point or luminance;

each of the second and third processing levels is level-invariant by not altering a property of the display system that has been set at a higher processing level; and

each processing level is process invariant, wherein each processing level uses the same two processing modules, but wherein different inputs are used to affect different properties of the display system.

28. The method of claim 27, wherein:

calculating, in a first processing module, called temporal modulation module, of each level, a simultaneous on/off duty cycle of the pixel lighting devices required for synthesizing the target color gamut; and

in a second processing module, referred to as a luminance module, the calculated simultaneous on/off duty cycles of the pixel illumination devices are modified to synthesize a display system white point luminance.

29. The method of claim 26, wherein the gamut control and white point control levels each maximize the brightness of the display system by scaling up the calculated simultaneous on/off duty cycles of the pixel illumination devices such that the largest of these on/off duty cycles is set to the maximum value of the solid state light based projection display system.