MXPA06001089A - Spoke light compensation for motion artifact reduction - Google Patents

Abstract

A sequential color display system (10) includes a color changer (14, 16) that causes each of a set of primary colors to appear on an imager that illuminates of each of a plurality of pixels on a display screen. A controller (30, 31) applies control signals to the imager to control the pixel brightness for each color. Each time the color changer transitions from one primary color to another, a spoke (18) occurs, and mixed light of two colors will illuminate the imager. The controller causes the imager to use such spoke light when the brightness level for each color for the associated pixel exceeds a prescribed threshold. When making use of the spoke light, the controller alters the control signal to decrease brightness of at least one primary color in substantial time proximity to the occurrence of the spoke to compensate for the brightness increase caused by using the light during the spoke.

Description

FLASH LIGHT COMPENSATION FOR A REDUCTION OF MOTION ARTIFACT CROSS REFERENCE WITH RELATED APPLICATIONS This application claims the benefit in accordance with 35 U.S.C. 119 (e) of U.S. Provisional Patent Application Serial No. 60 / 491,100, filed July 30, 2003, the teachings of which are incorporated herein by reference.

FIELD OF THE INVENTION The invention relates to a technique for operating a sequential color display system, and more particularly, to a technique that reduces the severity of motion artifacts caused by the compensation of brightness increases made during the color transitions.

BACKGROUND OF THE INVENTION At present, there are television projection systems that use a type of semiconductor device known as a Digital Micromirror Device (DMD). A typical DMD comprises a plurality of individually mobile micromirrors arranged in a rectangular configuration. Each micromirror rotates over a limited arc, typically within the range of 10 ° -12 ° under the control of an activating cell that secures a bit therein. After a previously secured "1" bit, the activating cell causes its associated micromirror to rotate to a first position. Conversely, the application of a bit "0" previously secured with the activating cell causes the activating cell to rotate its associated micromirror to a second position. By properly placing the DMD between a light source and a projection lens, each individual micromirror of the DMD device; when it rotates through its trigger cell corresponding to a first position, it will reflect the light from the light source through the lens and onto a display screen to illuminate an individual image element (pixel) in the display. When it rotates to its second position, each micromirror reflects light away from the display screen, which causes the corresponding pixel to appear dark. An example of such a DMD device is the DMD of the DLP ™ system available from Texas Instruments, Dallas, Texas. Current television projection systems incorporating a DMD of the type described, control the brightness (illumination) of the individual pixels by controlling the interval during which the micromirrors remain "on" (ie, rotated to their first position), against the interval during which the micromirrors remain "off" (ie, rotated to their second position), hereinafter referred to as the operating cycle. For this purpose, such DMD-type projection systems use pulse width modulation to control the brightness of the pixel by varying the duty cycle of each micromirror in accordance with the state of the pulses in a sequence of pulse width segments. Each pulse width segment comprises a pulse chain of a different duration of time. The state of activation of each impulse in a pulse width segment (ie, if each pulse goes off or on), determine if the micromirror remains off or on, respectively, for the duration of that impulse. In other words, the larger the sum of the total widths of the impulses in a pulse width segment that are turned on (activated) during an image interval, the greater the operating cycle of the micromirror associated with such impulses will be and higher the brightness of the pixel during such an interval. In television projection systems using such a DMD, an image interval, that is, the time between the display of the successive images, depends on the selected television standard. The NTSC standard currently in use in the United States requires an image interval of 1/60 second, while certain European television standards employ an image interval of 1/50 second. Current DMD-type television projection systems typically provide a color display when projecting red images, green and blue, either simultaneously or in sequence during each image interval. A typical DMD projection system in sequence uses a color changer typically in the form of a color wheel activated by motor, interposed in the path of light of the DMD. The color wheel has a plurality of separate primary color windows, typically red, green and blue, so that during the successive intervals, the red, green and blue light, respectively, falls on the DMD. As described, the combination of the DMD and the color wheel implements a color display in sequence. In order to minimize the color interruption artifact of the sequential display, the color sequence appears multiple times per incoming image. In this way, the color wheel must change the color of the DMD illumination multiple times during each image interval. For example, a DMD-type television set that changes the lighting color 12 times per image interval will display each of the three primary colors four times per incoming image, which produces a display called 4X. A "flash" occurs when the light hitting in the DMD undergoes a transition from a primary color to the next primary color. In normal form, the display does not use light (ie, "flash light") associated with a flash because it can not easily form a color saturated with such "mixed" light. However, at least one current DMD-type system (ie, the Texas Instruments DLP system) has an option, referred to as "light-flash recapture" (SLR) that uses some flash light under certain conditions, which makes it possible for a white object to have a higher peak brightness. The color changes constantly during each flash. In order to obtain a more consistent color reproduction, the flash is used completely or is not used at all. In addition, the Texas Instruments support circuitry for your DMD makes use of three flashes of different colors at a time, or does not use them. When used, a group of three flashes produce a large amount of added white light, typically about 8% of the light time without full flash. The Texas Instruments digital micromirror system adds flash light over a prescribed brightness threshold, typically approximately 60% of the total brightness. Below this mobile, the flash light remains unused. In this way, when the brightness increases just below the threshold to a value equal to the threshold, the flashes are "activated", which adds the flash light. In order not to have a large discontinuity in the brightness characteristic, a corresponding reduction in the non-flash light must occur so that the resulting incremental brightness increases in the order of a least important bit (LSB). However, when the corresponding reduction occurs at very different times in the image period than those occupied by the activated flashes, the conditions for a severe motion contour artifact are given. Thus, there is a need for a technique to place the correct amount of compensation reduction in the non-flash segments at the appropriate time for each flash that is activated.

BRIEF DESCRIPTION OF THE INVENTION In summary, in accordance with the present principles, a method is provided for operating a sequential color display system that includes a color changer that causes each of a group of primary colors to illuminate an image former which controls the brightness of each of the plurality of pixels of each color. The method begins by applying control signals to the imager, each of them, typically a sequence of pulse width segments, with each segment illuminating an associated pixel for a color corresponding to a brightness level according to the state of the control signal. Each time the color changer changes from one primary color to the other, an interval occurs (flash) and the mixed light of the two colors will illuminate the image former. The light that occurs during at least one group of flashes is used when the brightness level for at least one color for the associated pixel exceeds a prescribed threshold. When the flash light is used, the control signal is altered to decrease the brightness of at least one primary color in a proximity of time important for the presence of a flash, in order to compensate for the increase in brightness caused by the flash. use of light during that flash. While the flash light compensation technique of the present principles can be used, with advantage, in a DMD system employing pulse width modulation, the technique will find application in other types of sequential deployment systems.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 illustrates a schematic block diagram of a sequential color deployment system for practicing the flash light compensation technique of the present principles. Figure 2 illustrates a source view of a color wheel comprising part of the deployment system of Figure 1. Figure 3 illustrates a table describing a group of bit planes that control the pulses within each pulse width segment. which activates the image former in the system of Figure 1. Figures 4 through 8, collectively, illustrate an enumeration table of the bit planes that control the pulse width segments that handle the brightness of a corresponding color of each pixel within the deployment system of the Figure 1. Figure 9 illustrates the distribution of light between the pulse width segments for a brightness level below which, the flashes of the first group remain deactivated. Figure 10 illustrates a light distribution between the pulse width segment for a level of brightness in which the first group of flashes is activated; and Figure 11 illustrates a characteristic curve of a light output as a function of the light input, showing the influence of the non-flash light and the flash light.

DETAILED DESCRIPTION OF THE INVENTION Figure 1 illustrates a sequential color display system 10 of the type described in the "Single Panel DLP ™ Projection System Optics" Application Report, published by Texas Instrument, in June 2001, suitable for practicing the technique of flash light compensation of the present principles. The system 10 comprises a lamp 12 located at the focus of an elliptical reflector 13 which reflects light from the lamp through a color changer 14 and into an integrating bar 15. As described in more detail below, the color changer 14 serves to sequentially place each of the three primary colors, typically, red, green, and blue primary color windows between the lamp 12 and the integrator bar 15. In In the illustrated embodiment, the color changer 14 takes the form of a color wheel rotated by an engine 16. With reference to Figure 2, the color wheel 14 in the illustrated embodiment has the windows 17- and 174, 172 and 175 and 173 and 176 of red color, green and blue diametrically opposite, respectively. In this way, as the motor 16 rotates the color wheel 14 of Figure 2 in a clockwise direction, the blue, green and red light will strike the integrator bar 15 of Figure 1, in sequence. In practice, the motor 16 rotates the color wheel 14 at a high enough speed so that during an image interval of 1/60 second, the red, green and blue light hits the integrator bar four times, which produces twelve color images within one image interval, four red, four green and four blue interspersed, in a BGR sequence. With reference to Figure 1, the integrator bar 15 gathers the incident light at one end to produce at the other end a region of light of a uniform section that collides with a group of relay optics. The relay optics 18 distribute the light in a plurality of parallel rays which strike a bent mirror 20, which reflects the rays through a group of lenses 22 and on a prism 23 of total internal reflectance (TIR). Prism 23 TIR reflects parallel light rays on a digital mirror (DMD) device 24, such as the DMD device manufactured by Texas Instruments, for selective reflection on a projection lens 26 and on the screen 28. Although the color 14 appears in Figure 1 within the portion of the optical path lying between the lamp 12 and the integrator bar 15, the color wheel 14 can reside anywhere in the optical path between the lamp and the display 28. The DMD 24 takes the form of a semiconductor device having a plurality of individual micromirrors (not shown) arranged in a configuration. By way of example, the DMD manufactured and marketed by Texas Instruments has a micromirror array of 1280 columns per 720 rows, which produces 921,600 pixels in the resulting image projected onto the screen 28. Other DMDs may have different arrays of micromirrors. As mentioned before, each micromirror in the DMD rotates over a limited arc under the control of a corresponding trigger cell (not shown), in response to the state of a binary bit previously secured in the trigger cell. Each micromirror rotates to one of a first and second positions, depending on whether the secured bit applied to the activating cell is "1" or is "0", respectively. When it rotates to its first position, each micromirror reflects the light on the lens 26 and on the screen 28 to illuminate a corresponding pixel. While each micromirror rotates to its second position, the corresponding pixel appears dark. The time during the image interval while each micromirror reflects light through the projection lens 26 and onto the screen 28 (the operating cycle of the micromirror) determines the brightness of the pixel. The individual trigger cells in the DMD 24 receive activation signals from an activating circuit 30 of the type well known in the art and exemplified by the circuitry described in the document "High Definition Display System Based on Micromirror Device" of R.J. Grove et al, International Workshop on HDTV (October 1994). The trigger circuit 30 generates the trigger signals for the trigger cells in the DMD 24 in accordance with the control signals, typically, in the form of sequences of pulse width segments applied to the trigger circuit by a processor 31. Each segment of pulse width comprises a chain of pulses of different durations, the state of each pulse determines whether the micromirror remains on or off for the duration of that impulse. The shorter the impulse (ie, a 1 pulse) that can occur within a pulse width segment, (sometimes called the least important bit or LSB) typically lasts 15 microseconds, while the longer impulses in the segment, each one has a duration greater than an LSB. In practice, each pulse within a pulse width segment is controlled by a bit (hereinafter referred to as a "pixel control" bit), within a digital bitstream whose state determines whether the corresponding pulse is off or on. A bit "1" produces a pulse that turns on, while a bit i "0" produces a pulse that goes off. The total sum (duration) of the pulses activated in a pulse width segment controls the brightness of a corresponding pixel during that segment. Thus, the greater the combined pulse width (as measured in LSB) of the pulses activated in a pulse width segment, the greater the pixel brightness contribution for that segment. For a 4X display, the activator circuit 31 generates each of the four pulse width segments separated by color for each pixel. In this way, during an image interval, the activating circuit 31 generates pixel control bits for the twelve segment, four red, four blue and four green pulses. The transmission of the pixel control bits to the DMD 24 occurs in synchrony with the rotation of the color wheel 14 so that each segment of a given color corresponds to the illumination of that color in the DMD 24. With reference to the wheel of color 14 of Figure 2, a flash 18 is between each pair of windows of different color, such as between window 17? red and the window 172 green. The number of flashes 18 will depend on the number of red, green and blue windows in the color wheel 14. In this way, the color wheel 14 of Figure 2 having two thirds of BGR color (ie, two groups of windows) blue, green and red), will have six flashes 18. In the illustrated mode, the color wheel 14 rotates twice during each image interval, which gives rise to the appearance of twelve flashes during that time. Each flash 18, when the light spot of the lamp 12 passes, produces an interval when the light is mixed, which is when the light contains a mixture of two different colors. For example, the flash 18 located between a blue window and a green one will give rise to a span interval. The flash 18 that is between a red window and a blue one will give rise to an interval of magenta. The flash 18 that is between a red window and a green one will give rise to a yellow interval. Previously, DMD-type projection systems did not use light during a flash (hereinafter called "flash light") due to the difficulty of giving rise to a color saturated with such "mixed light".

At present, the Texas Instruments DMD system has an option referred to as "flash light recapture" (SLR), which under certain conditions, uses some flash light, which makes it possible for a white object to have a brightness of much higher crest. Since the color during each flash constantly changes, in order to obtain a consistent color reproduction, a flash is used completely or is not used. In addition, the Texas Instruments support circuitry for your DMD makes use of three flashes of different colors in combination, or does not use it. With the use of a set of three flashes it will give rise to an increased amount of added white light, typically about 8% of the time light without flash. Such light is added to the threshold brightness, typically about 60% of the total brightness. Below this threshold, the flash light remains unused. In this way, when you increase the brightness just below the threshold to a value equal to the threshold, a flash set is activated. In order not to have a large discontinuity in the brightness characteristic, a corresponding reduction in the non-flashing light must occur so that the resulting incremental brightness increases in the order of the least important bit (SLB). When the corresponding reduction occurs at very different times, in the image period, than in the occupied by flashes lit, then the conditions are appropriate for a severe artifact of motion contour. A motion artifact can occur when a moving target has adjacent portions of brightness just above and below the flash light activation threshold. In accordance with the present principles, a technique is provided to reduce the severity of such movement artifacts. As described in detail later, the compensation technique of the present principles compensates for the increased brightness achieved when a flash is "activated" (i.e., the flash light is used for a specific flash) by decreasing most of the brightness of the flash. pixel in a proximity of important time to the occurrence of the flash. The best results are usually obtained when these decreases in pixel brightness occur essentially completely immediately before or after an activated flash. However, good compensation can be achieved even when the diminished pixel brightness does not occur completely immediately before or after the flash is activated, provided that most of the decrease in brightness occurs in time close to flash activation. To understand the flash light compensation technique of the present principles, the way to control the DMD 24 in the system 10 will be described. As mentioned above, the DMD 24 in the illustrated embodiment comprises an array of 921,600 micromirrors. The pixel control bits for the micromirrors reside in the "bit planes", each in the form of a bit string corresponding in length to the number of micromirrors. The bits of each bit plane are loaded into the DMD 24, and depending on whether the individual bits of each plane are logical "1", it is determined that each micromirror is controlled by that bit and will illuminate a corresponding pixel or not. In the illustrated embodiment, the system 10 uses fourteen bit planes, each bit plane controls one or more pulses within one or more segments of pulse width. However, a greater or lesser number of bit planes is possible. To understand the way in which a bit layer controls the pulses with the pulse width segments, it is necessary to refer to Figure 3, which illustrates a table that shows for each bit plane, the expected weighting of the pulses between the pulses. in the pulse width segments. The second to the last row of Figure 3 identify each of the fourteen bit planes, labeled as # 0- # 13, respectively, while the last row of Figure 3 lists the total weighting (measured in LSB) for each bit plane. Thus, for example, the bit plane 0 has a total weight of 1 LSB, while the plane # 13 has a total weight of 66 LSB. The first four rows of Figure 3 show the expected weight distribution between the # 0- # 13 segments for each of the bit planes. For example, in the illustrated embodiment, the # 0 bit plane has a 1-LSB weight that is confined to segment # 2. On the other hand, plane # 5 of bits has a total weight of 6 LSB with the expected distribution of 3 LSB in segment # 2 and 3 LSB in segment # 3. By comparison, plane # 13 of bits has a total weight of 66 LSB with an expected flash of 17, 17, 15 and 17 LSB in segments # 0- # 3, respectively. It should be noted that Figure 3 illustrates the expected distribution of the weighting of each bit plane between the pulse width segments, the actual distribution may vary a bit. For example, for plane # 9 of bits, the actual flash between segments # 2 and # 3 may be 11.5 LSB and 12.5 LSB, respectively. Figures 4 to 8, collectively illustrate an impulse width enumeration table whose values correspond to a particular bit pattern used to control the pulses within one of the segments # 0- # 3, for each of the 0-255 levels of brightness for light without flash. It should be remembered that each pulse width segment corresponds to a separate one of four cases of a given color for a single pixel during an image interval (ie, every 1 / sixtieth of a second). Enumeration values of pulse width contained in the tables of Figures 4 to 8, they will achieve good compensation after activation of the first and second groups of flashes (hereinafter identified as game # 0 and # 1 game, respectively), to each of two different brightness levels, respectively (for example, brightness levels # 150 and # 203). In other words, the enumeration values of pulse width contained in the tables of Figures 4 through 8, provide good compensation flash when activating the flash occurs in the following sequence color order ((B 0 G 1 R 0) (B 1 G 0 R 1) (BGR) (BGR)), with the flashes of the games # 0 1 and # 1, represented as 0 and 1, respectively, in the order of color. As will be better appreciated from here on, while segments # 0- # 3 occur in sequence over time, segment # 2 appears first in brightness followed by segment # 3 and then segments # 1 and # 0. In other words, the No. 2 segment becomes increasingly bright first providing increases brightness of the segments # 0 and # 1 come last in brightness, and experience a decrease in brightness after activation of game # 0 and flash # 1 to compensate for flash light. With reference to Figure 4, brightness level # 1, the impulse controlled by plane # 0 (which has a width of 1 LSB) is activated in segment # 2, while the other impulses in this segment and in others segments remain deactivated. To achieve brightness level # 2, the impulse controlled by the # 1 plane of bits (which has a width of 2 LSB) is activated, while the pulse controlled by plane # 0 is now deactivated during segment # 2. As before, the other impulses in segment # 2 and in other segments remain deactivated. To achieve brightness level # 3, the impulse controlled by plane # 0 (1 LSB) and the impulse controlled by plane # 1 are activated during segment # 2, while the other impulses in segment # 2 and other segments are deactivated. To achieve brightness level # 4, the impulse controlled by plane # 1 remains on, while the impulse controlled by plane # 0 remains off during segment # 2. At the same time, the pulse controlled by plane # 2 (2 LSB) is activated during segment # 3 with the other impulses in segments # 2 and # 3 and in the other segments remain deactivated. To achieve each of the # 5- # 77 levels of brightness, the pulses controlled by other bit planes are reactivated during each of the # 2 and # 3 segments, so that the total bit width (measured in LSB) corresponds to the desired brightness level. However, the pulses in segment # 0 and segment # 1 remain off at these brightness levels. To achieve a brightness level above brightness level # 78, but below brightness level # 206, the pulses controlled by the bit planes associated with segments # 0 and # 1 selectively activate. Between brightness levels 207-255, the pulses controlled by the bit planes associated with segments # 0 and # 1, are fully activated. At brightness level # 255 (the maximum brightness level), all pulses controlled by the bit planes associated with segments # 0- # 3 are activated to reach a total pulse width of 255 LSB. In the present embodiment, flashes of flash game # 0 are activated when the brightness of at least one color, and typically when each of the three primary colors, reaches a prescribed threshold, typically 60% of the total brightness. In terms of brightness levels, illustrated in the pulse width enumeration table of Figures 4-8, the flashes of flash game # 0 is activated when at least one color, and typically when each of the three colors Primarys have a level of brilliance above the # 149 level of brightness in Figure 6, assuming no adjustment in the color temperature. In this way, after the transition from the # 149 level of brightness to a # 150 level of brightness, for each color, the flashes of the game # 0 are activated so that the added flash light increases the brightness of the pixel, as much as a 8% As an example, the activation of flashes of game # 0 of flashes on the level # 149 of brightness for the red color causes an increase in brilliance for that color. To compensate for the flashing light that arises from the activation of flashes of flashing game # 0, a corresponding decrease in brilliance must occur in the non-flashing light to allow increases in brightness in the order of 1 LSB when changing from a # 149 level of brilliance at a # 150 level of brilliance. In accordance with the present principles, the compensation for the additional brightness attributed to the activation of flashes of the # 0 flashing game for a given color (say, red) occurs when selecting a corresponding value from the table of number enumeration of Fig. 4 through 8, which has an associated brightness level that is reduced by almost the same amount as the increased brightness associated with the activation of the flash. This will be better understood with the following example. A desired brightness increase is assumed from the # 149 level of brightness to the # 150 level of brightness for the red color. Let's suppose that the flashing of the game # 0 of flashes is activated on the level # 149 of brilliance. In this way, to compensate for an additional brightness of 16 LSB that occurs from the activation of the flashes, the pulse width segment associated with the brightness level # 134 is selected, better than the pulse width segment associated with the level # 150 of brilliance. The pulse width segment corresponding to brightness level # 134 has a total pulse weighting (measured in LSB) that is 16 times less than the pulse weighting associated with the pulse width segment associated with brightness level # 150 . With the use of the pulse width enumeration values of the table of Figures 4 to 8, to compensate for a flash light it has the advantage that the resulting reduction in brightness occurs essentially very close to time in the presence of The flashes. An impulse width enumeration value of the table in Figure 6 should be considered for brightness level # 134 selected to compensate for the first set of flashes that are activated at level # 150. The pulse width segment associated with the brightness level # 134 in Figure 6 has segments # 1, # 2, # 3 filled with pulses of a total width of 29, 29, 38 and 38 LSB, respectively. Compared to segments # 2 and # 3 within the pulse width segment corresponding to brightness level # 150, segments # 2 and # 3 associated with brightness level # 134 each are filled with pulses that have the same width total (each with 38 LSB). Only segments # 0 and # 1 of the pulse width segment enumeration table value associated with brightness level # 134 have lower total pulse widths (each with 8 LSB less). However, by adding the 16 LSB increment that arises from activating the flashes of the first set of flashes, to the brightness of 134 LSB associated with the brightness level # 134 which will produce a total pulse width of 150 LSB needed to achieve the brightness corresponding to the # 150 level of brilliance. In addition, the values of the lowest pulse width of segments # 0 and # 1, occur entirely in time just before the first flash of game # 0 and just after the last flash of game # 0 of flashes, which reduces the severity of motion contour artifacts that would otherwise occur when the brightness decrease compensation occurred at very different times in relation to the activation of the flash. With reference to Figures 9 and 10, which help to understand the way in which brightness compensation occurs in accordance with the principles of the present invention, which occurs very close in time to the activation of the flash. Figure 9 illustrates the four thirds of color (ie, the four occurrences of blue, green and red) at a level # 149 of brightness for each color. The first and second thirds of color (corresponding to segments # 0 and # 1, respectively) have a combined brightness of 72 LSB per color, which reflects the sum of the total bit weights of 35 LSB and 37 LSB associated with the segments # 0 and # 1, respectively. With the same witness, the third and fourth thirds (corresponding to segments # 2 and # 3, respectively) have a combined brightness of 77 LSB per color, which reflects the sum of the total bit weights of 39 LSB and 38 LSB associated with segments # 2 and # 3, respectively. Figure 10 illustrates the four thirds of color (ie, the four occurrences of the colors blue, green and red) at the # 150 level of brilliance, together with the activation of the flashes in the # 0 flashing game. As can be seen in Figure 10, a first flash of the flashing set # 0 appears between the first cases of the blue and green colors. A second flash of game # 0 of flashes appears between the first case of red and the second case of blue, while the third flash of the same game appears between the second case of green and the second case of red. When compensating the increase of 16 LSB with light after the activation of the flashes of the game # 0 of flashes, when selecting the enumeration value of the pulse width corresponding to the level # 134 of brightness, the table of Figure 6 gives as result in segments # 1 and # 2 that have total bit weights of 29 LSB and 29 LSB, respectively, while segments # 2 and # 3, have total bit weights of 39 and 38, respectively. Compared with the total pulse widths of segments # 0 and # 1 associated with brightness level # 150, the total pulse widths of segments # 0 and # 1, associated with brightness level # 134, are each 9 LSB less (28 LSB against 37 LSB). Conversely, segments # 2 and # 3 associated with brightness level # 134 have the same total impulse widths (239 LSB and 39 LSB) compared to segments # 2 and # 3, associated with level # 150 of brilliance. When the flash light is compensated with the use of the pulse width numbering value of the table in Figure 6, associated with the brightness level # 134, each of the first two occurrences of the blue, green and red colors associated with segments # 0 and # 1, respectively, will have a reduced brightness. As can be seen in Figure 10, the reduction in brightness of the first occurrences of blue and green appear together before and just after, respectively, the first flash. Similarly, the reduction in brightness of the first occurrence of red and the second appearance of blue occur just before and just after, respectively, of the second flash. In addition, the reduction in brilliance of the second occurrence of green and the second occurrence of red occurs just before and just after, respectively, of the third flash. In other words, with the use of the pulse width numbering value, the table in Figure 6 associated with the brightness level # 134, serves to essentially confine all brightness reduction with the first two occurrences of the blue colors, green and red, corresponding to the interval during which activation of the flash game 0 occurs. The third and fourth occurrences of the colors blue, green and red (corresponding to segments # 2 and # 3) have essentially the same brightness (excluding the increase in brightness that increases after reaching the # 150 level of brightness). The system 10 of Figure 1 will also compensate for an increase in the flash light when the flashes of a second set of flashes (flash game # 1) are activated on a second threshold of brightness of color, typically the # 203 level of brightness . To appreciate the way in which the enumeration table of Figures 4 through 8 achieves flash light compensation under such conditions, an increase in brightness in increasing brightness level # 203 to brightness level # 204 should be considered for the Red color. It should also be assumed that the green and blue colors have a level of brightness above the threshold for flash activation of flash game # 1. At flash level # 204, flash game # 1 is activated (in addition to flash game # 0), which gives rise to an increase in brightness for the red color, ie by 16 LSB. In this way, to achieve an increase in brightness increasing to brightness level # 204, brightness level # 203, the value of the pulse width numbering table is selected for the table of Figure 7, associated with the Brightness threshold # 188 (better than the impulse width segment enumeration value associated with brightness level # 204). Under non-flash light conditions, the pulse width numbering value of table 7, associated with brightness level 204 represents the actual value used to obtain this level of brightness. Thus, under non-flashing light conditions, the # 0, # 1, # 2 and # 3 pulse width segments associated with the brightness level # 204 will have total pulse widths of 64, 64, 39 and 38 LSB, respectively, which produce a total pulse width of 204 LSB. However, when the flash light associated with the flash game # 0 is used above the # 149 level of brilliance, and when the flash light associated with the flash of flash game # 0 and # 1 above the level is used # 203, brightness, the pulse width numbering table of Figures 6 to 8, do not really represent, the actual state of occurrences, due to the need to use lower brightness level values to compensate for light of flash. As described above, a corresponding decrease in brightness needs to occur in non-flash light to compensate for flash light, which requires the use of the lower brightness level value of the pulse width numbering table of Figures 6 to the 8, which achieves the necessary brightness reduction, saves the 1 LSB or to increase the brightness increases to the next higher level. When you change the level # 203 and # 204 of brilliance, the pulse width enumeration value is used in the table of Figure 7 corresponding to brightness level # 188 (as opposed to the value associated with brightness level # 204). Compared to segments # 2 and # 3, associated with brightness level # 204, segments # 2 and # 3, associated with brightness level # 188 has the same total pulse width (39 and 38 LSB, respectively) . Only segments # 0 and # 1 associated with brilliance level # 188 have similar widths (each with 8 LSB minus). However, by adding the brightness increase 16 LSB that arises from activating the flashes to a width LSB of 188 total of the segments # 0, # 1 and # 2 and # 3, associated with the level # 188 of brightness will produce the width of boost needed (204 LSB) to achieve the brightness increase in brightness increase to reach the # 204 level of brightness from level # 203. As before, the lower pulse width values of the # 0 and # 1 segments associated with the # 174 brightness level cause a decrease in brightness for the red color, which occurs in time almost equal to the corresponding flashes of the game # 1 of flashes. To better appreciate the contribution of flash light to total light emission, refer to Figure 11, which illustrates a graph of the total emission of light as a function of light without flash and light with flash . Before reaching the # 150 level of brightness, the total emission of light comes from the light without flash. Between brightness levels # 150 and # 203, the total light includes a first fixed amount of flash light (which results from the activation of flashes of flash game # 0) and also a quantity of non-flash light that increases incrementally in a linear fashion to achieve a corresponding increase in total light. Once flashes of flash game # 0 are activated at the # 150 level of brightness, the flashless light falls by almost the same amount as the increase due to flash light, except for an increase to reflect the increase in brightness from level # 149 to # 150. At brightness level # 203, and above, the flashes from flash game # 1 are activated (along with the flashes from game # 0 of flashes), which gives rise to a second fixed amount of flash light. Again, the non-flashing light decreases by an amount corresponding to the increase in flash light, except for an increase associated with the increase in brightness level. As described above, the pulse width enumeration table of Figures 4 to 8 offer very good flash light compensation under circumstances when flash activation occurs during segments # 0 and # 1, of each width segment of impulse. However, the flash activation pattern may differ from (B 0 G 1 R 0) (B 1 G 0 R 1) (BGR) (BGR) and under such circumstances, a different group of bit planes and a table of Impulse width enumeration becomes necessary, depending on where the flashes occur, and which are activated. However, to achieve a flash light compensation in the manner described above, in close proximity to the occurrence of the flash to take into account the corresponding brightness increase due to the use of the flash light. The foregoing describes a technique for achieving flash light compensation in a sequential color display system, so that a decrease in light occurs without flash in close proximity with the occurrence of a flash to reduce the incidence of artifacts. of motion contour. Although the illustrated embodiment has been described in connection with a modulated sequential color display system, the flash light compensation in accordance with the present principles can be achieved without the pulse width modulation, since the reduction in light without flash occurs essentially in proximity of time with the occurrence of flashes.

Claims (20)

1. A method for operating a sequential color display system that includes a color changer and an image former, which operate in combination to illuminate in sequence at least one pixel with each of the three primary colors, characterized in that it comprises the steps of: applying a control signal to the imager to cause the imager to illuminate at least one pixel for each primary color at a brightness level in accordance with the control signal; using the light that occurs during at least a first flash of light, corresponding to a first interval when the color changer changes from one color to another, when the at least one pixel has a brightness level over a first prescribed threshold for the at least one color; and altering the control signal when the light is used during such a flash to decrease the brightness of at least one color in close proximity to the occurrence of the flash to compensate for the increase in brightness caused by the use of light during that flash.

The method according to claim 1, characterized in that the step of altering the control signal comprises the step of altering the control signal to decrease the brightness immediately before and after such flash.

3. The method according to claim 2, characterized in that the first brightness threshold differs for each color.

4. The method according to claim 1, characterized in that it further comprises the step of using the light that occurs during at least one additional flash, in addition to the light used during the at least one first flash, when the at least one a color has a level of brilliance on a second threshold.

5. The method according to claim 4, characterized in that the second brightness threshold differs for each color.

The method according to claim 1, characterized in that the step of applying the control signal includes applying a plurality of sequences of pulse width segments, each pulse width segment causing the imager to illuminate an associated pixel for each primary color at a brightness level in accordance with the total activation of the pulses within the impulse segment for such associated pixel.

7. A method for operating a sequential pulse width modulated deployment system, having a color changer and an image former operating in combination to illuminate the sequential form by at least one pixel for each of a group of colors primary, characterized in that it comprises the steps of: applying a plurality of pulse width segment sequences to the imager, each pulse width segment causes the imager to illuminate at least one pixel for each primary color at a level of brightness in accordance with the state of pulse activation within the pulse segment for the at least one pixel; using the light that occurs during the at least one first flash, corresponding to a first interval when the color changer changes from one color to another, when the at least one pixel has a brightness for the at least one color on the prescribed threshold; and altering at least one sequence of the pulse width segments when the light is used during the at least one first flash to decrease the brightness of at least one color in close proximity of time to the occurrence of at least one first flash to compensate for the increased brightness caused by using the light during at least a first flash.

The method according to claim 7, characterized in that the first brightness threshold differs for each color.

The method according to claim 7, characterized in that it also comprises the step of using the light that occurs during at least one additional flash, in addition to the light used during the at least one first flash, when the at least one color has a brightness level over a second threshold.

The method according to claim 7, characterized in that the second brightness threshold differs for each color.

11. A method for operating a sequential pulse width modulated deployment system having a color changer that causes each of a group of primary colors to sequentially illuminate an image former that illuminates each of the plurality of pixels for each primary color, characterized in that it comprises the steps of: applying a plurality of sequences of pulse width segments to the imager, each pulse width segment causes the imager to illuminate each pixel for each primary color at a level of brightness in accordance with the state of pulse activation for each pixel within a pulse segment; selecting at least a first flash, corresponding to a first interval when the color changer changes from a primary color to another primary color; altering at least one sequence of pulse width segments over a pixel brightness level prescribed for at least one color to selectively increase the brightness of the pixel with the use of light during the at least one first flash and to decrease the brightness of the pixel during pulse width segments that occur essentially immediately before and after at least one first flash in order to compensate for the increase in brightness of the flash light.

The method according to claim 11, characterized in that the first brightness threshold differs for each color.

The method according to claim 11, characterized in that it further comprises the step of using the light that occurs during at least a second flash in addition to the light used during the at least one first flash when each color has a level of brilliance on a second threshold.

The method according to claim 13, characterized in that the second brightness threshold differs for each color.

15. A sequential color display system, characterized in that it comprises: a light source; an imager for directing light from the light source to selectively illuminate each of a plurality of pixels on a display screen; a color changer for sequentially changing the color of the light that illuminates each of the plurality of pixels; and a controller for (a) applying a control signal to the imager to cause the imager to illuminate an associated pixel for each primary color at a brightness level in accordance with the control signal; (b) using the light that occurs during the at least one first interval (flash) wherein the color changer changes from one color to another when the at least one color has a brightness level above the first prescribed threshold; and (c) altering the control signal when the light is used during the at least one first flash to decrease the brightness of at least one primary color in close proximity to the occurrence of at least one first flash to compensate for the increase in brightness caused by using the light during at least a first flash.

The apparatus according to claim 15, characterized in that the controller alters the control signal to decrease the brightness immediately before and after at least one first flash.

The apparatus according to claim 15, characterized in that the first brightness threshold is different for each color.

18. The apparatus according to claim 15, characterized in that the controller makes use of the light that occurs during the at least one second flash, in addition to the light used during the at least one first flash, when each color has a level of brilliance on a second threshold.

19. The apparatus according to claim 18, characterized in that the second brightness threshold is different for each color.

20. The apparatus according to claim 15, characterized in that the controller applies a plurality of sequences of pulse width segments, each pulse width segment causes the imager to illuminate an associated pixel for each primary color at a level of brightness in accordance with the state of pulse activation within the pulse segment for such associated pixel.