Patent Publication Number: US-7218437-B2

Title: Field sequential color efficiency

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation application of pending U.S. patent application Ser. No. 10/513,631, which is assigned to the assignee of the present invention, which was filed on Nov. 5, 2004, which is a 371 National Phase of International Application No. PCT/US2003/014481 filed on May 6, 2003, which claims priority under 35 U.S.C. §119(e) to the following U.S. patent application Ser. No. 60/3 80,098 filed on May 6, 2002. 
     This application is related to the following commonly owned copending U.S. Patent Application: 
     Provisional Application Ser. No. 60/380,098, “Field Sequential Color Efficiency Enhancement”, filed May 6, 2002, and claims the benefit of its earlier filing date under 35 U.S.C. 119(e). 
    
    
     TECHNICAL FIELD 
     The present invention relates to the field of field sequential color display systems, and more particularly to enhancing the primary drive lamp efficiency in a field sequential color display. 
     BACKGROUND INFORMATION 
     Field sequential color displays, such as the one disclosed in U.S. Pat. No. 5,319,491, which is hereby incorporated herein by reference in its entirety, may use either pulse width modulation of primary colors (also known as time-multiplexing) to create color mixtures on a display screen, or amplitude modulation of each primary color to create the same effect Bach of these approaches provides sequential cycling of the primary colors in the screen at a high enough frequency that an individual&#39;s attribute of persistence of vision integrates the resulting light energy into a seamless image. 
     Field sequential displays, such as the one disclosed in U.S. Pat. No. 5,319,491, feeds light to pixels of each primary color, e.g., red, green, blue, by activating and deactivating lamps, referred to herein as “primary lamps.” The energy required to drive the primary lamps has been increasing in recent years in order to improve contrast ratios, viewing angles and visibility of the displays such as by having brighter primary lamps. 
     Therefore, there is a need in the art to drive primary lamps more efficiently in field sequential color displays. 
     SUMMARY 
     The problems outlined above may at least in part be solved in some embodiments of the present invention by mitigating the inherent energy inefficiencies inherent with continuous and/or phased illumination requirements as described below. 
     In one embodiment, a method for generating colors efficiently using pulse width modulation may comprise the step of waiting for a start signal for a primary color subcycle. The method may further comprise the step of receiving the start signal. The method may further comprise activating a primary light source used to drive the primary color during the primary color subcycle if there is data in the primary color&#39;s buffer. The method may further comprise continuing to activate the primary light source during the primary color subcycle until there is no data in the primary color&#39;s buffer. The method may further comprise deactivating the primary light source during the primary color subcycle if there is no data in the primary color&#39;s buffer. 
     In another embodiment of the present invention, a method for generating colors efficiently using amplitude modulation may comprise the step of normalizing a highest amplitude signal for one of a plurality of primary colors. The method may further comprise adjusting a drive light source intensity to a percentage of a maximum intensity where the percentage corresponds to a content of the normalized primary color in a frame. The method may further comprise adjusting an amplitude of all but the normalized primary color proportionally. 
     In another embodiment of the present invention, a method for generating colors efficiently using amplitude module may comprise the step of setting a maximum intensity for a light source intensity to a first value. The method may further comprise setting a maximum pixel intensity for each of the plurality of pixels to a second value. The method may further comprise adjusting the maximum intensity for the light source intensity by the first value divided by the second value. The method may further comprise adjusting an amplitude for each of the plurality of pixels by the second value divided by the first value. 
     The foregoing has outlined rather broadly the features and technical advantages of one or more embodiments of the present invention in order that the detailed description of the invention that follows may be better understood Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A better understanding of the present invention can be obtained when the following detailed description is considered in conjunction with the following drawings, in which: 
         FIG. 1  illustrates an embodiment of a data processing system configured in accordance with the present invention; 
         FIG. 2  is a perspective view of an optical display of the present invention; 
         FIG. 3  is a perspective view of an alternative light source for the display as shown in  FIG. 2 ; 
         FIG. 4  is a flowchart of a drive lamp algorithm in accordance with an embodiment of the present invention; 
         FIG. 5  is a flowchart of a method for generating colors efficiently using pulse width modulation in accordance with an embodiment of the present invention; 
         FIG. 6A  illustrates a timing diagram depicting the signal pulse widths for four pixels and the colors blue, green and red in the field sequential color display system using pulse-width modulation and using the trailing edge to determine color intensities; 
         FIG. 6B  illustrates a timing diagram depicting the signal pulse widths for four pixels and the colors blue, green and red in the field sequential color display system using the method of  FIG. 5  in accordance with an embodiment of the present invention as well as using the trailing edge to determine color intensities; 
         FIG. 7A  illustrates a timing diagram depicting the signal pulse widths for four pixels and the colors blue, green and red in a field sequential color display system using pulse-width modulation and using the leading edge to determine color intensities; 
         FIG. 7B  illustrates a timing diagram depicting the signal pulse widths for four pixels and the colors blue, green and red in a field sequential color display system using the method of  FIG. 5  in accordance with an embodiment of the present invention as well as using the leading edge to determine color intensities; 
         FIG. 8A  illustrates a timing diagram depicting the signal pulse widths for four pixels and the colors blue, green and red in a field sequential color display system using amplitude modulation; 
         FIG. 8B  illustrates a timing diagram depicting the signal pulse widths for four pixels and the colors blue, green and red in a field sequential color display system using either the method of  FIG. 9  or  FIG. 10  in accordance with an embodiment of the present invention; 
         FIG. 9  is a flowchart of a method for generating colors efficiently using amplitude modulation in accordance with an embodiment of the present invention; and 
         FIG. 10  is a flowchart of another method for generating colors efficiently using amplitude modulation in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention comprises a system and method for creating colors on a display efficiently. In one embodiment of the present invention, a start signal for a primary color subcycle may be received. A primary light source (which may be generalized to an illumination device of any design) used to drive the primary color may be activated during the primary color subcycle if there is data in the primary color&#39;s buffer. The primary light source may be continued to be activated during the primary color subcycle until there is no data in the primary color&#39;s buffer. The primary light source may be deactivated during the primary color subcycle if there is no data in the primary color&#39;s buffer. In another embodiment of the present invention, a highest amplitude signal for one of a plurality of primary colors may be normalized. A drive light source intensity may be adjusted to a percentage of a maximum intensity where the percentage corresponds to a content of the normalized primary color in a frame. The amplitude of all but the normalized primary color may be adjusted proportionally. In another embodiment of the present invention, a maximum intensity for a light source intensity may be set to a first value. A maximum pixel intensity for each of a plurality of pixels may be set to a second value. The maximum intensity for the light source intensity may be adjusted by the first value divided by the second value. An amplitude for each of the plurality of pixels may be adjusted by the second value divided by the first value. 
     Although the present invention is described with reference to a computer system, it is noted that the principles of the present invention may be applied to any system that has a field sequential decoder such as a television, a telephone, a projection system or a LCD display. It is further noted that a person of ordinary skill in the art would be capable of applying the principles of the present invention as discussed herein to such systems. It is further noted that embodiments applying the principles of the present invention to such systems would fall within the scope of the present invention. 
     In the following description, numerous specific details are set forth to provide a thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced without such specific details. In other instances, well-known circuits have been shown in block diagram form in order not to obscure the present invention in unnecessary detail. For the most part, details considering timing considerations and the like have been omitted inasmuch as such details are not necessary to obtain a complete understanding of the present invention and are within the skills of persons of ordinary skill in the relevant art. 
     As stated in the Background Information section, field sequential displays, such as the one disclosed in U.S. Pat. No. 5,319,491, feeds light to pixels of each primary color, e.g., red, green, blue, by activating and deactivating primary lamps. The energy required to drive the primary lamps has been increasing in recent years in order to improve contrast ratios, viewing angles and visibility of the displays such as by having brighter primary lamps. Therefore, there is a need in the art to drive primary lamps more efficiently in field sequential color displays as addressed by the present invention discussed below. 
     Referring to  FIG. 1 ,  FIG. 1  illustrates a typical hardware configuration of data processing system  100  which is representative of a hardware environment for practicing the present invention. Data processing system  100  may have a processing unit  110  coupled to various other components by system bus  112 . An operating system  140 , may run on processor  110  and provide control and coordinate the functions of the various components of  FIG. 1 . An application  150  in accordance with the principles of the present invention may run in conjunction with operating system  140  and provide calls to operating system  140  where the calls implement the various functions or services to be performed by application  150 . Read-Only Memory (ROM)  116  may be coupled to system bus  112  and include a Basic Input/Output System (“BIOS”) that controls certain basic functions of data processing system  100 . Random access memory (RAM)  114  and Disk adapter  118  may also be coupled to system bus  112 . It should be noted that software components including operating system  140  and application  150  may be loaded into RAM  114  which may be data processing system&#39;s  100  main memory for execution. Disk adapter  118  may be an integrated drive electronics (“IDE”) adapter that communicates with a disk unit  120 , e.g., disk drive. 
     Referring to  FIG. 1 , data processing system  100  may further comprise a communications adapter  134  coupled to bus  112 . I/O devices may also be connected to system bus  112  via a user interface adapter  122  and a display adapter  136 . Keyboard  124 , mouse  126  and speaker  130  may all be interconnected to bus  112  through user interface adapter  122 . Event data may be inputted to data processing system  100  through any of these devices. A display  138 , as described in further detail in conjunction with  FIG. 2 , may be connected to system bus  112  by display adapter  136 . In this manner, a user is capable of inputting to data processing system  100  through keyboard  124  or mouse  126  and receiving output from data processing system  100  via display  138 . It is noted that data processing system  100  is illustrative of a field sequential color display system and that the principles of the present invention, as discussed herein, may be applied to other systems, e.g., televisions, telephones, projection systems, LCD displays, that has a field sequential decoder. 
     Referring to  FIG. 2 ,  FIG. 2  illustrates an embodiment of the present invention of an optical display  138 . Optical display  138  may comprise a light guidance substrate  202  which further comprises a flat-panel, n×m Matrix of optical shutters (also known as pixels, i.e., picture elements)  204  and a light source  206  which is capable of selectively providing white, red, green, blue, monochrome, and infrared light to the matrix  204 . The light source  206  is connected to the matrix  204  by means of an opaque throat  208 . Behind the light guidance substrate  202  and in parallel, spaced-apart relationship with it is an opaque backing layer  210 . The edges of the light guidance substrate  202  are silvered, as indicated, for example, at  212 . 
     The light source  206  comprises an elliptical reflector  214  which extends the length of the side of the light guidance substrate  202  on which it is placed. In one embodiment, reflector  214  includes three tubular lamps  216   a ,  216   b , and  216   c  (not entirely shown in  FIG. 2 ) disposed in a serial, coaxial manner. The lamps  216   a ,  216   b  and  216   c  provide, respectively, red, green, and blue light The longitudinal axis of the lamps  216   a ,  216   b  and  216   c  is offset from the major axis of the reflector  214  in order to reduce optical losses due to the presence of on-axis light rays that fail to reflect off the top surface of the light guidance substrate. In other words, the lamps are situated to minimize the presence of light which is unusable for shuttering/display purposes. In another embodiment, the three tubular lamps  216   a–c  may be replaced with a series of colored Light Emitting Diodes (LED&#39;s) or cold cathode fluorescent lighting. 
     The light source  206  further comprises the opaque throat aperture  208  which is rigidly disposed on one edge of the light guidance substrate  202 . The aperture  208  in turn rigidly supports the reflector  214  and its associated lamps  216   a ,  216   b  and  216   c . The aperture  208  is proportioned to admit and allow throughput of light from the light source  206  which enters at angles such that the sine of any given angle is less than the quotient of the throat height divided by the throat depth. 
     In  FIG. 3 , there is shown an alternative light source which comprises an opaque throat aperture  208  as discussed above which is rigidly connected to an elliptical reflector  214  also as discussed above. However, within the reflector  214  are disposed a red lamp  216   a , a green lamp  216   b , and a blue lamp  216   c  in a vertical stack within the reflector  214 . Lamps  216   a ,  216   b  and  216   c  may collectively or individually be referred to as lamps  216  or lamp  216 , respectively. It is noted that lamp  216  may be referred to herein as a “primary lamp” or a “drive lamp.” 
     Should infrared light be desired, the colored lamps may either be replaced with an infrared lamp, or an infrared lamp may be disposed next to the colored lamps within the reflector  214 , or an infrared lamp may be disposed within its own reflector (not shown) on another edge of the light guidance substrate  202 . 
     It is noted that  FIGS. 2–3  are illustrative of an embodiment of display  138 . It is noted that the principles of the present invention may be applied to any type of display that uses field sequential colors. It is further noted that a person of ordinary skill in the art would be capable of applying the principles of the present invention as discussed herein to such displays. It is further noted that embodiments applying the principles of the present invention to such displays would fall within the scope of the present invention. 
     The present invention may produce efficiency gains by addressing the matter of wasted light energy in the default light cycle system. When a drive lamp is no longer needed, it may be turned off. The turn-off signal sent to the primary drive lamp may be latched to the trailing edge of the last pixel that has program content for that primary. Accordingly, ultimate efficiency may be a function of program content. 
     A drive lamp algorithm for a pulse-width modulated field sequential color display system prior to the application of the efficiency algorithm of the present invention is disclosed in  FIG. 4 . Referring to  FIG. 4 , the drive lamp algorithm  400  used in a field sequential color display, such as display  138  (see  FIG. 1 ), initializes an incrementation index (“n”), e.g., n=0, in step  401 . 
     In step  402 , a particular primary lamp (“h”) is initialized For example, a primary lamp (“h”) corresponding to the value of “1”, e.g., blue primary lamp, may be initialized. In step  403 , the color bit depth is initialized. The color bit depth may refer to the number of hues or shades of color that may be displayed, e.g., 2 k  colors may be displayed where k typically equals 8. In step  404 , the number of primary colors (“p”), e.g., p=3 for red, green and blue, is initialized. In step  405 , the quiescent gap factor (“g”), referring to the duration between activating and deactivating a primary lamp, is initialized, e.g., g=1. In step  406 , the frame rate (“f”), referring to the duration of time a flame of an image is displayed, is initialized. For example, the frame rate (f) may typically be equal to 1/60 seconds. 
     In step  407 , the temporal subdivision is calculated using the following equation:
 
 s =1/(( k+g )* p*f )  (EQ1)
 
where s is equal to the temporal subdivision, referring to the smallest discretely addressable duration of time within each frame; where k is equal to the bit depth; where g is equal to the gap factor, where p is equal to the number of primary colors and where f is equal to the frame rate.
 
     In step  408 , the primary lamp initialized in step  402  is activated. In step  409 , a wait interval, equal to the temporal subdivision, is implemented. In step  410 , the index is incremented by the value of one, e.g., n=n+1. In step  411 , a determination is made as to whether the index (n) is equal to the bit color depth (k). 
     If the index is not equal to the bit color depth, then a wait interval, equal to the temporal subdivision, is implemented in step  409 . 
     If the index is equal to the bit color depth, then, in step  412 , the lamp initialized in step  402  is deactivated. In step  413 , if the value of “h” (referring to a particular primary lamp) is less than “p” (referring to the number of primary colors), then the value of “h” is incremented. Otherwise, “h” is set to equal the value of “1.” 
     In step  414 , a determination is made as to whether the gap factor (g) is greater than zero. If the gap factor is greater than zero, then, in step  415 , a wait interval, equal to the temporal subdivision times the gap factor, is implemented. Upon implementing the wait interval of step  415 , the index (n) is set to zero in step  416 . 
     If the gap factor (g) is not greater than zero, then the index (n) is set to zero in step  416 . 
     In step  417 , a determination is made as to whether an external command to terminate drive lamp algorithm  400  was received. If an external command to terminate drive lamp algorithm  400  was received, then the routine is shutdown in step  418 . 
     Otherwise, the lamp corresponding to the value of “h” as established in step  413  is activated in step  408 . 
     The efficiency gains using the efficiency algorithm of the present invention in a field sequential color display system using drive lamp algorithm  400  is described below in conjunction with  FIG. 5 .  FIG. 5  is a flowchart of a method  500  for generating colors efficiently using pulse width modulation in accordance with an embodiment of the present invention. 
     Referring to  FIG. 5 , efficiency algorithm  500  may include a step of waiting for a red subcycle start signal in step  501 . In step  502 , a determination is made as to whether the red subcycle is ready. If the red subcycle is not ready, then algorithm  500  waits to receive the red subcycle start signal in step  501 . If the red subcycle is ready, then, in step  503 , a determination is made as to whether there is any data in the red buffer. 
     If there is data in the red buffer, then the primary lamp for the red primary color is activated in step  504 . In step  505 , a determination is made as to whether there is any data in the red buffer. If there is data in the red buffer, then, in step  506 , the red primary lamp stays activated. A determination is then made in step  505  as to whether there is any data in the red buffer. 
     If, however, there is no data in the red buffer, then, in step  507 , the red primary lamp is deactivated. The red primary lamp may be deactivated during the red subcycle thereby saving energy. In step  508 , algorithm  500  waits to receive a green subcycle start signal. 
     As stated above, a determination is made in step  503 , as to whether there is any data in the red buffer. If there is no data in the red buffer, then, in step  508 , algorithm  500  waits to receive a green subcycle start signal. By not activating the red primary lamp since there is no data in the red buffer, energy is saved. 
     Referring to step  508 , a determination is made in step  509  as to whether the green subcycle is ready. If the green subcycle is not ready, then algorithm  500  waits to receive the green subcycle start signal in step  508 . If the green subcycle is ready, then, in step  510 , a determination is made as to whether there is any data in the green buffer. 
     If there is data in the green buffer, then the primary lamp for the green primary color is activated in step  511 . In step  512 , a determination is made as to whether there is any data in the green buffer. If there is data in the green buffer, then, in step  513 , the green primary lamp stays activated. A determination is then made in step  513  as to whether there is any data in the green buffer. 
     If, however, there is no data in the green buffer, then, in step  514 , the green primary lamp is deactivated. The green primary lamp may be deactivated during the green subcycle thereby saving energy. In step  515 , algorithm  500  waits to receive a blue subcycle start signal. 
     As stated above, a determination is made in step  510 , as to whether there is any data in the green buffer. If there is no data in the blue buffer, then, in step  515 , algorithm  500  waits to receive a blue subcycle start signal. By not activating the green primary lamp since there is no data in the green buffer, energy is saved. 
     Referring to step  515 , a determination is made in step  516  as to whether the blue subcycle is ready. If the blue subcycle is not ready, then algorithm  500  waits to receive the blue subcycle start signal in step  515 . If the blue subcycle is ready, then, in step  517 , a determination is made as to whether there is any data in the blue buffer. 
     If there is data in the blue buffer, then the primary lamp for the blue primary color is activated in step  518 . In step  519 , a determination is made as to whether there is any data in the blue buffer. If there is data in the blue buffer, then, in step  520 , the blue primary lamp stays activated. A determination is then made in step  519  as to whether there is any data in the blue buffer. 
     If, however, there is no data in the blue buffer, then, in step  521 , the blue primary lamp is deactivated. The blue primary lamp may be deactivated during the blue subcycle thereby saving energy. In step  501 , algorithm  500  waits to receive a red subcycle start signal. 
     As stated above, a determination is made in step  517 , as to whether there is any data in the blue buffer. If there is no data in the blue buffer, then, in step  501 , algorithm  500  waits to receive a red subcycle start signal. By not activating the blue primary lamp since there is no data in the blue buffer, energy is saved. 
     It is noted that method  500  may include other and/or additional steps that, for clarity, are not depicted. It is further noted that method  500  may be executed in a different order presented and that the order presented in the discussion of  FIG. 5  is illustrative. It is further noted that certain steps in method  500  may be executed in a substantially simultaneous manner. 
     It is further noted that the field sequential color display system is extensible to more than three primary colors. Drive lamp algorithm  400  ( FIG. 4 ) contains some refinements related to how finely divided the pulse modulation is set Efficiency algorithm  500  ( FIG. 5 ) uses the natural buffer/cache states of the pulse modulation control for the screen&#39;s pixels to shut down unneeded primaries and prevent wasted energy from being expended which may result in lengthening the life span of batteries in portable displays, e.g., Personal Digital Assistant (PDA). 
     A comparison of  FIG. 6A  (default algorithm without efficiency algorithm applied) and  FIG. 6B , in which the algorithm of  FIG. 5  has been incorporated into the lamp driver circuitry, illustrate how the present invention reduces waste and improve display efficiency.  FIG. 6A  illustrates a timing diagram depicting the signal pulse widths for four pixels and the colors blue, green and red in field sequential color display system  100  (see  FIG. 1 ) using pulse-width modulation as well as using the trailing edge to determine color intensities.  FIG. 6B  illustrates a timing diagram depicting the signal pulse widths for four pixels and the colors blue, green and red in field sequential color display system  100  (see  FIG. 1 ) using the method of  FIG. 5  in accordance with an embodiment of the present invention as well as using the trailing edge to determine color intensities. 
     Referring to  FIGS. 6A and 6B , the lower three lines in  FIGS. 6A and 6B  delineate the respective power-on times for the Red, Green, Blue (RGB) drive lamps. For the pixel program content example provided, the overall energy used is less than half of that in the default configuration.  FIG. 6B  depicts the ideal lamp cycle for maximum efficiency, and this cycle may be achieved by using the efficiency algorithm of  FIG. 5  to determine the correct turn-off signals for the main driver sequence initialized in  FIG. 4 . The level of complexity required to achieve this improvement in efficiency may be reduced since it polls system information already in hand and dictates a straightforward interaction between the respective drive lamps and the signals feeding the on-screen pixels. This constitutes the application of the present invention to pulse width modulated field sequential color display devices, whether they are monochromatic systems, RGB systems, or use additional lights (whether visible or non-visible) as part of the drive suite. 
     It is further noted that the principles of the present invention outlined above may apply to a field sequential color display using either the trailing edge or leading edge to determine color intensities since the triggering event latches image data resident in buffers. The specially triggered deactivation in the one addressing mode (trailing edge) disclosed above may be logically mirrored by a corresponding specially triggered activation in the other mode (leading edge), the inverse case of that disclosed. That is, the activation of a primary lamp used to drive a primary color during a primary color subcycle may be delayed until there is data in the primary color&#39;s buffer. If the field sequential color display uses leading edge to determine color intensities,  FIGS. 6A and 6B  may appear as  FIGS. 7A and 7B , respectively.  FIG. 7A  illustrates a timing diagram depicting the signal pulse widths for four pixels and the colors blue, green and red in field sequential color display system  100  (see  FIG. 1 ) using pulse-width modulation and using the leading edge to determine color intensities.  FIG. 7B  illustrates a timing diagram depicting the signal pulse widths for four pixels and the colors blue, green and red in field sequential color display system  100  (see  FIG. 1 ) using the method of  FIG. 5  in accordance with an embodiment of the present invention as well as using the leading edge to determine color intensities. 
     In amplitude-modulated field sequential color display systems, the primary color lamps cycle may be at 100% intensity for each sub-cycle in field sequential color display systems, such as display system  100  (see  FIG. 1 ), as illustrated in  FIG. 8A . The present invention enhances efficiency in field sequential color display systems using amplitude modulation, as illustrated in  FIG. 8B .  FIG. 8A  illustrates a timing diagram depicting the signal pulse widths for four pixels and the colors blue, green and red in field sequential color display system  100  (see  FIG. 1 ) using amplitude modulation.  FIG. 8B  illustrates a timing diagram depicting the signal pulse widths for four pixels and the colors blue, green and red in field sequential color display system  100  (see  FIG. 1 ) using either the method of  FIG. 9  or  FIG. 10  in accordance with an embodiment of the present invention.  FIG. 98  is a flowchart of a method for generating colors efficiently using amplitude modulation in accordance with an embodiment of the present invention.  FIG. 10  is a flowchart of another method for generating colors efficiently using amplitude modulation in accordance with an embodiment of the present invention. 
     Referring to  FIG. 9 , in conjunction with  FIG. 8B , in step  901 , the highest amplitude signal for a given primary color subcycle during a given frame of video information is normalized. In step  902 , a drive lamp intensity is adjusted to a percentage of a maximum intensity where the percentage corresponds to a content of the primary color (whose amplitude signal was normalized) in a frame. In step  903 , an amplitude of all but the primary color whose amplitude signal was normalized is adjusted proportionally. It is noted that method  900  may include other and/or additional steps that, for clarity, are not depicted. It is noted that method  900  may be executed in a different order presented and that the order presented in the discussion of  FIG. 9  is illustrative. It is further noted that certain steps in method  900  may be executed in a substantially simultaneous manner. 
     An example of implementing method  900  is as follows. If a given video frame has a maximum red content of 77%, then the drive lamp intensity is adjusted to 77% and the amplitude for that pixel is adjusted to 100%. All other pixels are adjusted proportionally as to their digitally-determined intensity value so that their visual output is identical to the default case. This calculation may be conducted continually, adjusting the drive lamps and pixel amplitudes to arrive at the lowest possible energy consumption for every instant of display output. This system lends itself to drive lamps that may not be adversely affected by continuous adjustment of input power. By logical extension, this approach may work equally well if a white lamp, e.g., a backlight, is being color filtered in a field sequential color system. For example, the RGB lamp intensities of  FIG. 8B  may directly map to the white drive lamp, the light from which then passes through color filters (whether stationary or moving such as in a rotating color wheel interposed between the source and the display) prior to being amplitude modulated at the pixel level. 
     Consulting  FIG. 8B , which depicts the amplitude modulated efficiency algorithm being applied to a representative sample program (represented by four pixel data lines), it may be appreciated how much energy is saved at the drive lamps by noting the gap between the dotted line (representing 100% drive lamp intensity) with the actual drive signals for the lamps. 
     Real time adjustment of pixel amplitudes and lamp intensities is described below in conjunction of  FIG. 10 .  FIG. 10  is a flowchart of another method  1000  for generating colors efficiently on a field sequential color display. Referring to  FIG. 10 , in step  1001 , a maximum intensity for a lamp intensity is set to a first value. In step  1002 , a maximum pixel intensity for each of a plurality of pixels is set to a second value. In step  1003 , the maximum intensity for the lamp intensity is adjusted by the first value divided by the second value. In step  1004 , an amplitude for each of the plurality of pixels is adjusted by the second value divided by the first value. It is noted that method  1000  may include other and/or additional steps that, for clarity, are not depicted. It is noted that method  1000  may be executed in a different order presented and that the order presented in the discussion of  FIG. 10  is illustrative. It is further noted that certain steps in method  1000  may be executed in a substantially simultaneous manner. 
     An example of implementing method  1000  is as follows. The process may be initialized by setting the maximum intensity to a fixed value I, e.g., I=256 relative units. For each subcycle, the maximum pixel intensity may be set to m, e.g., m=79 relative units. The lamp intensity for the subcycle may then be set to m/I, e.g., 79/256=30.86% of full intensity, and each pixel&#39;s individual amplitude x shall be adjusted to its new value, X, using the relationship X=I x/m. For example, the fill intensity pixel originally at 79 units may be divided by 79 and multiplied by 256, which normalizes it to 256 units, as expected. A pixel at a different initial value, e.g., 61, may be adjusted by dividing 61 by 79 and multiplying by 256, yielding a corrected amplitude of 197 relative units. In all cases, the actual output intensity at each pixel may be identical to the original default values (excepting very slight shifts due to digital round-off error in applying the algorithm). Interestingly, this approach allows for extending the color palette as aggregate color intensities on-screen depart from full intensity, i.e., the darker hues of program content. This expansion of palette size (increase in amplitude divisions against the standard division value) may numerically be equivalent to I/m times the default palette size. In the example above, where 79 is the maximum pixel intensity during the pertinent subcycle, the palette was increased by I/m=324%. The image encoding software may be responsible for imprinting the additional shading definitions into the data stream being fed to the pixels. As with the efficiency enhancing algorithms, the palette enhancement may be continuously variable in real time as a function of program content. 
     In addition to enhancing the energy efficiency of displays, all the foregoing embodiments, incorporating the principles of the present invention outline above, coincidentally enhance the signal-to-noise ratio of display systems thereby also improving a display&#39;s contrast ratio. The signal-to-noise ratio may be enhanced because the noise floor is attenuated when unused light in a field sequential color cycle is no longer available to generate system noise via intrinsic scattering, etc. 
     Although the method and system are described in connection with several embodiments, it is not intended to be limited to the specific forms set forth herein; but on the contrary, it is intended to cover such alternatives, modifications and equivalents, as can be reasonably included within the spirit and scope of the invention.