WO2005088599A1

WO2005088599A1 - Full color video display using black-white display with tri-color light source

Info

Publication number: WO2005088599A1
Application number: PCT/US2005/005853
Authority: WO
Inventors: Enhao Li; Shushan Li
Original assignee: Enhao Li; Shushan Li
Priority date: 2004-02-28
Filing date: 2005-02-24
Publication date: 2005-09-22
Also published as: TW200534226A

Abstract

A full color video display system utilizes a black white display and a tri-color light source. The black white display is a LCD in which an image of every pixel on the entire panel is synchronously updated (i.e. a-field-at-a-time) rather than scanned row-by-row (i.e. a-line-at-a-time). The pixel circuits in the LCD panel include at least two thin film transistors (TFT) and two storage capacitors (Cs). The first Cs functions as the signal memory. The functions of the second Cs and the first TFT are the same as those in the conventional active matrix LCD. The second TFT functions as one of image switches to update the image of every pixel at the same time. The tri-color light source is switched on/off in sequence to emit red, green and blue uniform light when the LCD panel is synchronically updated to the corresponding image.

Description

FULL COLOR VIDEO DISPLAY USING BLACK-WHITE DISPLAY WITH TRICOLOR LIGHT SOURCE

RELATED APPLICATIONS [0001] This application claims priority to U.S. Provisional Patent Application, Serial Number 60/548,648, entitled "FULL COLOR FLAT PANEL VIDEO DISPLAY BY USING BLACK-WHITE LCD WITH TRI-COLOR LEDs BACKLIGHT" filed on February 28, 2004, having Enhao Li and Shushan Li, listed as the inventors, the entire content of which is hereby incorporated by reference.

BACKGROUND [0002] This invention relates to color video display systems and particularly to a single panel field sequential color video display using black-white display with tri-color light source.

[0003] Television made by a large flat screen display like plasma display panel (PDP) or liquid crystal display (LCD) is thinner, lighter, and cheaper with better color reality, higher contrast, and higher brightness than televisions made by other displays like projection television (TV) and traditional direct view cathode ray tube (CRT) TV. The need of high-resolution flat panel display for high definition television (HDTV) is strong on the market. Bulky CRT direct view TV will eventually be replaced by the flat panel display TV such as the active matrix liquid crystal display (AMLCD) TV and PDP TV. Size, cost, resolution, brightness, and contrast are important characteristics of consumer designs. The lower cost, higher quality, lighter and thinner flat panel TV will continually expand and dominate the consumer TV market.

[0004] Today's flat panel displays for TV applications use spatial color principle such as color filter RGB sub-pixel in LCD TV. The separate sub-pixels are used to modulate respective primary colors. Such color panel technologies have three limitations: firstly, the requirement for sub-pixels limits the effective image resolution.

Secondly, white light falls on each of the sub-pixels, but only the color of the light for which the sub-pixel is designed is usable~the remainder is wasted. Thus a two-third loss of efficiency results. Thirdly, state of the art panel resolution is lower, or the panel cost is higher, because of using sub-pixels. The cost of color filter is over one fifth of a full color

LCD. Two-third more driver channels for display using sub-pixel are also one of the high cost reasons. PDP TV and LCD TV are the best flat panel display TVs in the market. The pixel size of PDP is bigger than that of LCD. All spatial color displays lose their two thirds of its resolution.

[0005] Until the high bright blue LED (light emitting diode) was successfully developed at the beginning of nineteen nineties, the flat tri-color LEDs backlight display using the principle of field sequential color was not possible. Terry Scheffer invented field sequential color display by TNLCD (twist nematic liquid crystal display) in US Patent No. 4019808 and No. 4239349 in 1977 and 1980 respectively. Dean Irwin proposed a field sequential color LCD using LED backlight in US Patent No. 4978952, issued on December 18, 1990. The content of each of those patents is incorporated by reference. However, because the response time of LCD was slow and because the image on every pixel does not synchronously show up with the corresponding light from the flat backlight, no qualified flat sequential full color LCD was made. Because the response time of the Pi- cell LCD reaches 2.5ms today and the present invention of a-field-at-a-time, it is possible to implement a flat field sequential color video display.

[0006] Single panel LCD projection TV using the principle of the field sequential color has appeared on the market. The cost of single panel projection TV is much lower than that using three panels. Peter Janssen et al. of Philips Electronics North America Corporation invented a prism scrolling color wheel to solve one of problems of field sequential color LCD panel projection TV in US Patent No. 5532763 and No. 5608467, in which the color lights synchronously scan the LCD panel downward as the corresponding image is scanned row-by-row on the LCD panel. The content of each of those patents is incorporated by reference. A bulky mechanical scrolling color wheel from Philips to match the image a-line-at-a-time cannot be used for flat TV application.

SUMMARY [0007] One embodiment of the present invention pertains to a system to achieve a high performance low cost color video display using an active driving display and a tri-color light source. A new active driving method: a-field-at-a-time was invented using an active driving display with a new pixel circuit of active components. In one preferred embodiment of the present invention, a flat tri-color (red, green and blue) light source as backlight is made of red, green, and blue LEDs with a diffuser. The red, green, and blue LEDs are turned on in sequence, and the red, green, and blue lights illuminate on the black white LCD panel in sequence respectively. This LCD panel is an active matrix liquid crystal display (AMLCD), for example, an amorphous silicon thin film transistor (a- Si TFT) twist nematic liquid crystal display (TN LCD). However, pixel circuits of active driving display in one embodiment of the present invention are different from that of the conventional AMLCD. There are at least two TFTs and at least two storage capacitors on each pixel. One of the TFTs has the same function as the TFT in the traditional AMLCD. The new second TFT (212, 312) functions as an image switch controlled by a global bus line (213, 313). The new first storage capacitor (211, 311) is just under the global bus line (213, 313) in each local pixel. It functions as the signal memory. The second storage capacitor (214, 314) has the same function as on conventional AMLCD. Both second TFT (212, 312) and second capacitor (214, 314) are made compatible with the traditional AMLCD processing. These newly added image switches TFT (212, 312) controlled by a single signal from global bus line are utilized to update the image of every pixel on the panel at the same time in order to respond to any one of the red, green and blue lights synchronously rather than row-by-row scanning. This is a new driving method of a real field sequential color. The image on the invented display is changed a-field-at-a-time rather than a-line-at-a-time in the traditional matrix display or a-point-at-a-time in CRT (cathode ray tube) display BRIEF DESCRIPTION OF THE DRAWINGS [0008] The following drawings form part of the present specification and are included to further demonstrate certain aspects of the present invention. The invention may be better understood by reference to one or more of these drawings in combination with the detailed description of specific embodiments presented herein.

[0009] FIGURE 1 shows a side perspective view of the structure of a color video display using single LCD panel and tri-color flat backlight; and

[0010] FIGURE 2 show a schematic diagram of a pixel circuit of the active driving display panel; and

[0011] FIGURE 3 is an example of the pixel layouts of a pixel circuit of the active driving display panel.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS [0012] FIGURE 1 is a side view structure of a full color video display using a single black white panel which includes an active matrix driving black white LCD panel (101), and a flat tri-color LEDs backlight system (102) for generating primary color red, green and blue light sequentially. The black white LCD panel (101) driven by the active matrix consists of a front polarizer (103) as the linear polarized light analyzer, a common substrate (104) coated with ITO electrodes and polyimide buffering layer, an active matrix substrate (105) attached with row scan driver ICs and column driver ICs, rear polarizer (106) as the linear polarized light generator, a light modulation material layer liquid crystal (107). The tri-color backlight (102) consists of a light diffuser (108) uniformly to diffuse the light, and the tri-color LEDs (109) (red LEDs, green LEDs and blue LEDs) embedded in the sides of diffuser plate (108) on which all surfaces are coated with reflective film except front polished surface for diffusing.

[0013] FIGURE 2 is a diagram of a pixel circuit. There are two TFT switches and two storage capacitors. The first TFT (210) is a switch whose function is similar to the one on the conventional TFT LCD. When the corresponding line (216) is selected, this TFT (210) is turned on by being applied a positive voltage on its gate from gate line (216), the signal on the column line (218) from the data driver passes through the TFT (210) and charges the capacitor (211). The signal is stored in the storage capacitor (211) until all lines are scanned and signals are stored. When the last line is finished scanning to load, the second TFT (212) on each pixel of the entire display are synchronously turned on by the global bus line (213) at the same time the corresponding LEDs of the backlight (102) in Figure 1 are turned on. The global bus line of each pixel is linked together either on or outside the display panel. It means that every image on each pixel is synchronously updated by the image switch controlled by a single control signal from the linked global bus line. The image on each pixel is updated by the signal saved earlier on the capacitor (211). And this signal will be stored in the second storage capacitor (214) and the liquid crystal pixel capacitor (215). The second storage capacitor (214) has the same function as the storage capacitor on the conventional TFT LCD.

[0014] Figure 3 is one of the pixel layout solutions. Anyone skilled in the art knows that two TFTs and two capacitors are compatible with the conventional TFT processing. Copying the pattern of the first TFT (310) side by side creates the second TFT (312). The first storage capacitor (311) is built under the global bus line (313). The second capacitor (314) is built under the pixel ITO (315) between the ITO (315) and next gate scan line (317). The drain of first TFT (310) connects to the column data signal line (318), and the source of the first TFT (310) connects to the first storage capacitor (311). The drain of second TFT (312) connects with the source of the first TFT (310) and to the first storage capacitor (311). The pixel ITO (315) connects with the source of the second TFT (312) and to the second storage capacitor (314).

[0015] There are three types of color generating principle used to produce a full color video display. The first is three-channel color method (such as three guns CRT projection TV and three panel projection TV) in which the three red, green and blue images coincidently combine together on the screen. The second is three-mosaic color sub-pixel in which the red, green and blue sub-pixels form a pixel to trick human eye when the sub-pixel cannot be distinguished. The third is field sequential color in which the time sequential sub-frame red, green and blue images are mixed in the human's brain if the images change fast enough to trick the human's eye. The field sequential color Television was the first color video display technology developed in CBS (Columbia Broadcasting System) in late of nineteen forties. A tri-color (Red, Green, and Blue) filter wheel is mechanically rotating in front of a black-white CRT. Three sub-frame black- white images are converted into a field of red image, a field of green image and a field of blue image, which are mixed in the human's brain to achieve a frame of color video image. The three-channel is more expensive than single panel because it requires three panels or CRTs. The color filter sub-pixel has high quality but still expensive because the cost of color filters is over one-fifth its display cost and requires 3 times column drivers.

[0016] Active driving image-generating device is an active driving display on which there is a circuit of active components on each pixel. Active driving display does not have to be matrix display. The active matrix display is one of examples of active driving display. The conventional active matrix display composes a matrix of row and column. Both active driving display and active matrix display have some active components or active switches, such as TFT, on each pixel. The signal on each pixel of active driving display can be held for a certain period of time. The passive matrix display is made of a simple matrix of row and column without any active components on the pixel. Although the passive matrix display could achieve a-fielcL-at-a-time using the active addressing method by the special driving circuits out of the display panel, no acceptable passive matrix active addressing display has been mass-prodmced. An example of active driving displays with one more TFT and one more capacitor added on each pixel of the conventional active matrix LCD is one of the preferred embodiments of the present invention to implement a-field-at-a-time.

[0017] The television signal is time sequential which is designed to fit for CRT display with the addressing method of a-point-at-a-time. In tfcie electronics of the device, separate red, green and blue signals are derived from th_e appropriate input source (broadcast, cable, direct) as is well known to those skilled in "the art. The color TV signal is actually divided into three separated channels to be amplified. For mosaic color filter matrix display the signal must be processed to form a mixing data stream in order to fit the sub-pixel's arrangement. For the single panel black- white LCD, the separate signal does not need to be processed for mixing. However, certain video signal processing is necessary in order to drive display in accordance with the field sequential color. The parallel red, green and blue signals must be serialized to a serial stream with, for example, the green signal delayed one third of a video field behind the red signal and the blue signal delayed one third of a video field behind the green signal. The three-ctiannel separate color signals are processed into serial signals.

[0018] When one of the serial monochrome TV signals is displayed by the matrix display (such as LCD), the sequential analog video signal is transformed into digital signal by an ADC (analog to digital converter) and stored in the memory. The digital signal will be sent to column data driver 8-bit by 8-bit and held in the driver until the data of an entire line are transferred. It is not necessary to convert analog to digital for digital TV signal. Then the row driver starts to drive the line of display matrix by a latch signal, and the column driver simultaneously starts to send the holding digital signal to that line by the same latch signal to show up that line image. The digital signal is usually converted into analog signal by a DAC (digital to analog converter) by column data driver in AMLCD for digital type driver since the TN type LCD is an analog device to response the gray scale by applying different voltage. The analog video signal can be directly sampled and held in the column signal driver for an entire line. After the entire line video signal is finished to be sampled and held by the column drivesr, the row scan driver starts to scan the corresponding row, and at same time the video signal held in the column driver is latched to the scanned row to show that line's image.

[0019] No matter what the signal is, either digital or analog, the image on the matrix display always shows up row-by-row. This is called a-line-at-a-time. This a-line-at- a-time manner for matrix display already increases the image displaying duty cycle as the times of the column number as that of a-point-at-a-time in CRT. The pixel switch on the conventional active matrix display extends the image showing duty cycle up to almost 100 percent, but it is still row-by-row addressing, i.e. the image on the display is changed a- line-at-a-time. This a-line-at-a-time driving method shows an image a-line-at-a-time.

[0020] No matter what the application is, the LCD must response fast enough to trick human's eye to form a full color in his head. The response time of LCD had better be less than 10 milliseconds (100Hz frame rate), at least no more than 16.7 milliseconds (60Hz frame rate) in order to avoid perceiving the flicker. The response time of today's AMLCD technology is less than 20 milliseconds. If the response time can be less than 6 milliseconds (~180Hz frame rate), it can show the video image very well. Ten milliseconds (100Hz) are acceptable. It can be made of either a special structure of the LCD cell like pi-cell with a fast response liquid crystal material like fast nematic liquid crystal, or PDLC (Polymer Dispersed Liquid Crystal) or PSLC (Polymer Stabilized Liquid Crystal), or any other possible fast response liquid crystal material.

[0021] One embodiment of the present invention pertains to a revolutionary solution of a-field-at-a-time (or "a-frame-at-a-time") by new pixel circuits to drive the display panel. The image updating can perfectly synchronize with the change of one of uniform tri-color lights from tri-color light source. One preferred embodiment of tri-color light source of the present invention is the flat tri-color backlight made by LEDs with a flat diffuser. This method gives much better color fidelity at lower cost because: firstly it is a new field sequential color that every pixel is exactly synchronous with the corresponding color light, and secondly the LED's high color saturation extends the area of color triangle on the chromaticity diagram. The larger color triangle of LEDs than that of color filter enables it to achieve more colors like reality.

[0022] One of the examples of present invention to implement a-field-at-a-time is a new design of pixel circuits based on the AMLCD shown in Figure 2, in which there are two TFTs and two storage capacitors as shown in Figure 3. The first TFT (210, 310) is switched on by a signal from the gate scan line (216, 316). The data signal from the column bus line (218, 318) flows through the drain of TFT (210, 310) to the source of TFT (210, 310), and data is stored in the first storage capacitor (211, 311). After the data of all lines of display are finished scanning to load as the conventional AMLCD, there is a signal from global bus line (213, 313) to switch on the second TFT (212, 312) on every pixel. The TFT (212, 312) lets the signal stored in capacitor (211, 311) be transferred to the pixel capacitor (215, 315) and the second capacitor (214, 314) of every pixel simultaneously. The duration of the global bus line signal to send the signal stored in storage capacitor (211, 311) to pixel capacitor (215, 315) is about the same as or a little bit longer than the duration of scanning each line to load data. After the signal on each storage capacitor Cs (211, 311) is synchronously transferred to the pixel capacitor (215, 315) and storage capacitor Cs (214, 314), the global bus line control signal goes low to lock the image signal on the pixel to show the image until the last line is scanned for next color image.

[0023] Those skilled in the art know that the image signal can be stored in the capacitor (211, 311) without leaking. Because the Vgs (voltage between gate and source) of TFT (212, 312) is zero or negative when signal is stored in capacitor (211, 311), the Vds (voltage between drain and source) from the signal stored on the capacitor (211, 311) cannot open the TFT (212, 312) according to I-V (Intensity of electric current- Voltage) characteristics of the TFT. The TFT (212, 312) can be switched on by applying the positive voltage on its gate from global bus line (213, 313).

[0024] Only when all the signals of one frame of image are transferred to pixels, signal of global bus line (213, 313) goes low to isolate the image signal on the pixel capacitor (215, 315) and pixel storage capacitor (214, 314). When the image is displaying on every pixel, the next color image signal start to be loaded into signal storage capacitor (211, 311) row-by-row. The displaying time of each color image is exactly the same as the shining time of the corresponding color light. The on-state time of TFT (212, 312) is about the same as that of each line scanning, or the on-state time of TFT (211, 311). As a matter of fact, the signal is still sent to the display by a-line-at-a-time (row-by-row), the same behavior as in the matrix display. But the images show up simultaneously. That is a-field- at-a-time for image because the images on each pixel appear synchronously. At the same time one of the tri-color lights is turned on by the starting edge of "the same signal as controlling TFT (212, 312) from global bus line (213, 313). The backLdght keeps on until the next frame image comes. When next frame image comes, the previous color Light are turned off and the new image corresponding color Light are turned on fc>y the new starting edge of the controlling signal of global bus line (213, 313).

[0025] The backlight (102) is particularly designed in order "to achieve uniform primary color red, green and blue light in sequence. The red, green and blue LEDs (109) evenly embedded into the four sides of the diffuser plate (108). T ie front surface is particularly polished in order to get uniform distribution light. All four-side surfaces and the rear surface of the diffuser plate (108) are coated with reflective fϊkm in order fully to utilize the light emitted from LEDs (109). The tri-color LEDs backlight (102) made by organic polymer semiconductor films may emit uniform light without "the requirement of the embedding LED into the diffuser. The LEDs are controlled by a signal derived from the global bus line (213, 313). When the TFT (212, 312) is turned on by the global bus line (213, 313), the LEDs of backlight are synchronously turned on by the starting edge of the same global bus line signal. But the duration of one of the three color LEDs is not equal to the duration time of the TFT (212, 312) being on but equal to the time; of a frame image showing on the pixels. So the LEDs keep on until next color image sb ows up. And then the LEDs are switched to another color in sequence, and so on.

[0026] It should be kept in mind that the principle of synchronous showing the image of every pixel, a-field-at-a-time (or "a-frame-at-a-time"), could be used in any other display applications, for example, LCOS, DMD, MEMS, etc. Tlie synchronously displaying image of every pixel is illuminated by the corresponding color light from a light source in sequence. The duration of each color image may be different in order to achieve highest color saturation for each color. The light source for illuminating the a- field-at-a-time display to achieve color video display could be a light source behind the transmissive display as a backlight or a light source in front of the reflective display as a frontlight. This principle could be used for direct viewing display, projection display.

[0027] Those skilled in the art know that the circuits of pixel could be more than two TFTs and more than two capacitors. It is well known that the TFT is actually is an active switch. The TFT may be n-type TFT as shown in the Figure 2- It may also be p- type TFT without being shown in the drawing. It may also include both n-type TFT and p- type. Some of controlling signal for p-type TFT are reversed compared with that of n-type TFT. For example, it needs a negative signal to turn on the p-type TFT rather than a positive signal to turn on the n-type TFT. The TFT could be made by amorphous silicon (a-Si), Poly-silicon (poly-Si, includes LTPS (low temperature poly-silicon), HTPS (high temperature poly-silicon) or other processing, microcrystalline silicon (μC-Si), crystalline silicon (c-Si), organic polymer semiconductor, compound semiconductors (such as CdSe), etc.

[0028] One preferred embodiment of the present invention has been described as an active driving display on which there are two TFTs and two capacitors of each pixel with controlling by a global bus line. This is just an example of the present invention. The implementation of this embodiment of present invention is totally compatible with the processing of the traditional AMLCD. Its cost for mass-production is less than that of conventional AMLCD because no color filter is required and two thirds of column drivers are saved besides the cost of the active matrix processing is identical.

[0029] It should also be kept in mind that many other components may be substituted for the above described system. Other arrangements of components that provide sequential red, green and blue lights may be utilized in conjunction with the present invention. One preferred embodiment of the present invention has been described as a flat tri-color LEDs backlight. The tri-color LEDs backlight is the preferred tri-color light source. It is one of the best solutions for a flat color video display. For reflective display or projection display, the light source may be any kind tri-color light source for giving uniform tri-color lights. Rather than a colored red, green and blue light LEDs, three inorganic EL panel light sources may be utilized in conjunction with a tri-color light source. The tri-color light source could be built by many inorganic semiconductors. It could be also built by three organic LED films together. The light source for flat video display application prefers to flat tri-color LEDs with the diffuser. For other applications, the light source is not necessary to be flat as long as it gives uniform three base colors in sequence respectively.

[0030] It is also noted that the preferred embodiment of the present invention is utilizable with any type of known electronic displays such as a transmissive display, or a reflective display, or a three dimensional display, or micro-display, or a head mounted display, or a virtual display. The invention could also be utilized in a projection system that includes single panel projection and three-panel projection. In certain applications a two-color or quad-color or many-color light source rather than tri-color light source could be used. The sequence of the colors may be not necessarily red, green and blue. It can be any sequence like green, red and blue, or blue green and red, etc. Techniques to speed the response time on a LCD include: heating the panel, low viscosity liquid crystal material, high contrast material and/or making the liquid crystal layer thinner. Any combination of these techniques may be used.

[0031] Although one embodiment of the present invention has been described in conjunction with preferred embodiments, it is to be understood that modifications and variations may be resorted to without departing from the spirit and scope of the invention, as those skilled in the art will readily understand. Such modification and variations are considered to be within the purview and scope of the invention and the appended claims.

REFERENCES CITED [0032] The following references, to the extent that they provide exemplary procedural or other details supplementary to those set forth herein, are specifically incorporated herein by reference.

U.S. PATENT DOCUMENTS

Patent Number Filing Date Inentor

4019808 Apr., 1977 Scheffer 349/97

4239349 Dec, 1980 Scheffer 349/117

4978952 Dec, 1990 Irwin 345/102

5093652 Mar., 1992 Bull, et al 345/592

5532763 Jul, 1996 Jassen, et al 348/744

5608467 Mar., 1997 Jassen, et al 348/744

6320565 Nov., 2001 Albu, et al 345/98

REFERENCES

U.S. Patent No. 5,847,066 issued on December 8, 1998 with Coy et al. listed as inventors.

"Concept of Field Sequential Color LCD With Flat Backlight Panel", SID 85 Digest, pp. 81-83

"A Frame-Sequential Color-TV Projection Display", SLD 90 Digest, pp. 534-536

Claims

WHAT IS CLAIMED:

1. A display system comprising an active driving image-generating device having pixels capable of having an image of every pixel shown synchronously to achieve a-field-at-a-time.

2. The display system of claim 1, wherein the pixels modulate light to illuminate on or through the active driving image-generating device to show an image.

3. The display system of claim 1, wherein the active driving image-generating device comprises a transmissive display or a reflective display.

4. The display system of claim 1, wherein the active driving image-generating device comprises an active matrix display to update an image on every pixel simultaneously achieving a-field-at-a-time.

5. The display system of claim 3, wherein the transmissive display or the reflective display comprises a black-white display.

6. The display system of claim 3, wherein the reflective image-generating device comprises a reflective LCD, a Liquid Crystal On Silicon (LCOS) display, a Digital Micro-mirror Device (DMD) display, a Micro-Electric Mechanical System (MEMS) display, or a Thin-film Micro-mirror Array (TMA) display.

7. The display system of claim 4, wherein the active driving image-generating device comprises a pixel circuit of at least one active switch and at least one signal memory component.

8. The display system of claim 7, wherein the memory component comprises a capacitor, a flip-flop, a static random access memory (SRAM), a dynamic random access memory (DRAM), or a device holding the signal.

9. The display system of claim 7, wherein the active switch of the pixel circuit comprises two thin film transistors (TFTs), wherein one is a signal control switch, and the other is an image switch.

10. The display system of claim 7, wherein the signal memory component comprises two storage capacitors, wherein one is to hold the signal as a memory, and the other is to extend the holding time of liquid crystal pixel capacitor.

11. The pixel circuits of claim 10, wherein one of the two storage capacitors comprises a conventional storage capacitor built between pixel ITO and scan line to enhance the charge holding time on the pixel, and the other is built between pixel ITO and global bus line to be the signal memory.

12. The pixel circuits of claim 7, wherein one of the at least two TFTs comprises a conventional active matrix scanning switch, the other is an image switch built between pixel ITO and the signal memory storage capacitor.

13. The pixel circuits of claim 7, wherein the active switch comprises a complementary metal oxide semiconductor (CMOS), an inorganic transistor, an organic transistor, a thin film transistor (TFT), an a-Si (amorphous silicon) TFT, a Poly-Si (poly- crystalline silicon) TFT, a μC-Si (micro-crystalline silicon) TFT, a c-Si (crystalline silicon) TFT, an organic TFT, or a compound semiconductor TFT.

14. A color display system comprising: (a) a black-white display system comprising an image-generating device having pixels capable of having an image of every pixel shown synchronously to achieve a-field-at-a-time; and (b) a tri-color light source capable of emitting a single primary color light to illuminate the image-generating device.

15. The color display system of claim 14, wherein the image-generating device comprises a transmissive display.

16. The color display system of claim 14, wherein the image-generating device comprises a black white liquid crystal display (LCD).

17. The color display system of claim 14, wherein the image-generating device comprises an active matrix LCD with image switches controlled by a global bus line to update the image on every pixel synchronously achieving a-field-at-a-time.

18. The color display system of claim 14, wherein the image-generating device comprises a passive matrix but actively addressing LCD with special driving circuits to update the image on every pixel synchronously achieving a-field-at-a-time.

19. The color display system of claim 14, wherein the image-generating device comprises a reflective display, a LCD, a liquid crystal on silicon (LCOS) display, a digital micro-mirror device (DMD) display, a micro-electric mechanical system (MEMS) display, or a Thin-film Micro-mirror Array (TMA) display.

20. The color display system of claim 14, wherein the tri-color light source emits uniform lights.

21. The color display system of claim 14, wherein the tri-color light source emits three primary base colors comprising red, blue and green.

22. The color display system of claim 21, wherein red, blue and green color lights are switchable sequentially.

23. The color display system of claim 14, wherein the tri-color light source is made of an inorganic semiconductor, or organic semiconductor.

24. The color display system of claim 21, wherein the tri-color light source can be three group LEDs which are embedded in a light diffuser and evenly emit red, green and blue uniformly light sequentially.

25. The color display system of claim 14, wherein the tri-color light source illuminates the black- white display with one of three primary base colors in sequence with synchronously updating the corresponding image of every pixel on the black-white display to form a full color display image