Solid state color display system and light emitting diode pixels therefor

• US 5,184,114 A
• Filed: 03/15/1990
• Issued: 02/02/1993
• Est. Priority Date: 11/04/1982
• Status: Expired due to Fees

• Current Assignee: General Electric Company
• Original Assignee: Integrate Systems Engineering Limited
• Inventors: Brown, Brent W.
• Primary Examiner(s): Brier, Jeffery A.
• Application Number:
  US07/495,006
• Time in Patent Office: 1,055 Days
• Field of Search: 340/793, 340/767, 340/701, 340/703, 340/762, 340/782, 340/815.1, 340/815.03, 340/815.01, 313/500
• US Class Current: 345/83
• CPC Class Codes: G09F 9/33 being semiconductor devices, e.g. diodes
• CPC Class Codes: G09G 2310/0259 with use of an analog or digital ramp generator in the column driver or in the pixel circuit
• CPC Class Codes: G09G 2320/0285 using tables for spatial correction of display data
• CPC Class Codes: G09G 3/2014 by modulation of the duration of a single pulse during which the logic level remains constant
• CPC Class Codes: G09G 3/32 semiconductive, e.g. using light-emitting diodes [LED]

Abstract

Wide color range display systems comprising integrated, phase modulated light from three light emitting diode (LED) pixels. Each pixel comprises a large number of LED chips arranged compactly to provide a discrete element light source of sufficient output to be viewed as a point source of light from a substantial distance. The arrays of pixels are placed in a matrix of a type typically used in scoreboards, message centers and other large display systems, although the various combinations, subcombinations, and elements are not limited to such uses. Each pixel is mounted in a molded package which may include a transparent lens covering and sufficient number of connecting leads to provide for the number of colors of LEDs contained in the pixel array. Each pixel is placed in a mounting fixture which also accommodates the necessary electrical connections to multiplexed driving circuitry. The light emitted is determined by the type of LED used in the array, preferably an array of red, green and blue, although amber, green and other color combinations may be used. Using three colors, blue, red, green that are controlled by separate driving circuitry provides the capacity to create any color in the spectrum.

Claims

1. A large matrix display system comprising:

an array comprising a large number of juxtaposed multi-color solid state integrated pixels and means arranging the pixels in a close matrix pattern;

each pixel comprising an exposed face comprising a plurality of differently colored separate LEDs and means compactly arranging the LEDs so that each pixel is an apparent point composite color light source to an observer of the array;

a plurality of separate conductor means forming a part of each pixel, one separate conductor means for the LEDs of each color, means by which each conductor means electrically communicates only with all of the LEDs of one color of the pixel whereby a coordinated series of different signals is respectively communicated to the LEDs of each color to sequentially visually create at each pixel A succession of composite colors one after another ranging across a large number of color combinations;

means comprising a source of separate but coordinated series of signals for the LEDs of the same color for each pixel of the matrix display;

means controlling and delivering said coordinated series of signals separately but simultaneously respectively to the LEDs of same color of each pixel of the matrix display in such a manner that each pixel will, at any point in time, display only one composite color from within said large number of color combinations comprising a visual integration of the period of illumination of each LED of each pixel produced by each of the plurality of coordinated signals delivered to the differently colored LEDs of each pixel and said one composite color of each pixel will sequentally change from time to time as said plurality of coordinated signals from said source means and controlling and delivering means change whereby images of composite colors, which vary with time across the spectrum of a large number of color combinations, are successively visually illuminated on the matrix display.

2. A matrix display comprising:

a plurality of multi-color solid state LED pixels;

each multi-color pixel comprising a plurality of differently colored electrically independent sets of LEDs and means arranging the LEDs of each pixel in a closely spaced pattern;

each set of differently colored LEDs of each pixel being electrically interconnected by separate conductor means;

means electrically separating the conductor means to the LEDs of one color at each pixel from the conductor means to the other LEDs at each pixel;

source means of separate but coordinated series of separate signals collectively representative of the desired mixed color intensity to be visually obtained at each point in time from each pixel of the display;

a plurality of separate means, one for each LED color at each pixel, by which said series of separate signals are simultaneously communicated respectively to each set of LEDs of each color of each pixel whereby (a) the resulting color mix at each pixel displayed to an observer at each point in time is a composite integration of the separate color intensity level signals simultaneously but separately delivered to the respective LEDs of each color of the pixel, (b) the composite color displayed to an observer of all pixels of the display will at each point in time comprise an integrated image comprising many colors across a large number of color combinations, and (c) the image and many colors thereof will change from time to time as the color intensity level signals of the series changes.

3. The display according to claim 2 wherein the plurality of separate means comprise drive circuit means which systematically, sequentially and separately drive the LEDs of each color of each pixel of the display via the series of signals.

4. The display according to claim 3 wherein the driver circuit means comprise memory means for temporarily storing said signals and means selectively outputting the stored signals to the LEDs in a scan format.

5. The display according to claim 4 wherein the driver circuit means comprise digital data signal generating means.

6. The display according to claim 4 wherein the driver circuit means comprise analog or digital pulse width modulated signal generating means by which period of illumination is controlled.

7. The display according to claim 3 wherein the driver circuit means comprise means for the refreshing the color of the LEDs of each pixel during the time interval of each image by recommunicating the current series of data from storage to the LEDs.

8. The display of claim 2 wherein each of the plurality of separate means comprise means which demultiplexes the signals and routes the demultiplexed signals in a row-by-row format to driver circuit means.

9. The display according to claim 8 wherein the drive circuit means comprise time share memory means for storing the demultiplexed signals and control logic means for outputting said signals from the memory means.

10. The display according to claim 9 wherein the control logic means causes the demultiplexed signals to be output to scan means from which each series of signals are repeatedly communicated on a sequential basis to the LED pixels.

11. The display according to claim 2 wherein said source means comprises video digitizer means.

12. The display according to claim 2 wherein said source means comprises computer means.

13. The display according to claim 2 wherein said source means comprises means issuing NTSC, PAL, or SECAM television signals.

14. The display according to claim 2 wherein sample and hold means are interposed between standardized value means and the means communicating each output signal to retain the period of illumination of each color of each LED for each pixel for extended periods of time.

15. The display according to claim 2 comprising pulse width modification means which determine the period of illumination of each LED of each pixel in association with each of the plurality of separate means by which image flicker is minimized.

16. The display according to claim 2 wherein the pixels and the plurality of separate means are arranged so that the signals occur in a row and column format.

17. A matrix display comprising:

a plurality of tri-color solid state LED pixels;

each tri-color pixel comprising three differently colored electrically independent sets of LEDs and means arranging the LEDs of each pixel in a closely spaced pattern;

each set of tri-colored LEDs of each pixel being electrically interconnected by separate conductor means;

means electrically separating the conductor means to the LEDs of one color at each pixel from the conductor means to the other LEDs at each pixel;

source means of three separate but coordinated series of signals collectively representative of the desired mixed color intensity to be visually obtained at each point in time from each pixel of the display;

three separate means, one for each LED color at each pixel, simultaneously communicating said three series of separate signals respectively to each set of LEDs of each color of each pixel whereby (a) the resultant color mix at each pixel displayed to an observer at each point in time is a blended integration of the colors illuminated at each set of LEDs which corresponds to the period of LED illumination signals simultaneously but independently delivered to each of the respective LEDs of each color of the pixel, (b) the composite color displayed to an observer of all pixels of the display collectively will at each point in time comprise an integrated image comprising a large number of color combinations across a color spectrum, and (c) the image and many colors thereof of the display will change from time to time as the signals representing the color intensity level of each set of LEDs of each pixel changes.

18. A matrix display according to claim 17 wherein the three sets of LEDs per pixel comprise red, green and blue LEDs, respectively.

19. A matrix display according to claim 17 wherein the source means comprise means by which data signals are derived and the source means further comprise means issuing a plurality of data bits for the three differently colored sets of LEDs of the pixels respectively by which the number of available composite color visual outputs is exponentially increased.

20. A matrix display according to claim 17 wherein the source means comprise means by which data signals are derived and further comprising means by which the data signals are respectively delivered to the sets of LEDs is in a refreshing modulated scan data format, means controlling the rate there of so that it substantially exceeds the rate at which data signals are issued from the source.

21. A matrix display according to claim 17 wherein each of the three separate means of each pixel connect respectively to anode means of the associated set of LEDs.

22. A method of presenting successive visual images on a matrix display comprising;

providing a plurality of tri-color solid state LED pixels arranged in a pattern;

connecting the LEDs of each tri-color pixel to comprise three differently colored sets of LEDs;

causing each set of tri-colored LEDs of each pixel to be electrically interconnected by separate conductor means;

issuing three separate but coordinated series of signals per pixel from a source, the signals collectively representative of the desired hue and intensity to be obtained at each point in time from each set of differently colored LEDs of each pixel of the display;

simultaneously communicating said three separate signals per pixel separately to each set of differently colored LEDs of each pixel whereby (a) the color mix displayed at each pixel to an observer at each point in time is a single color comprising a blended integration of the color illuminated at each set of LEDs which corresponds to the duration of illumination determined by signals simultaneously but separately delivered to each of the three sets of LEDs of each pixel, (b) the composite color displayed to an observer of all pixels of the display collectively will at each point in time comprise an intelligible integrated image comprising many hues across the color spectrum, and (c) the image and many hues of the display will change from time to time as the signals representing the intensity level of each set of LEDs of each pixel change.

23. A method of displaying images of varying colors within the spectrum on a matrix display comprising:

providing an array comprising a large number of juxtaposed multi-color solid state integrated LED pixels arranged in a close matrix pattern, each pixel comprising sets of differently colored compactly arranged LEDs so that each pixel is an apparent composite point color light source to an observer of the array;

controlling and selectively and separately electrical communicating from a source of video or computer signals several separate but coordinated series of signals respectively to each set of LEDs at each pixel;

producing multi-color illumination at many if not all of the pixels at any point in time which visually comprise only one composite color at each pixel of a large number of color combinations resulting from selective illumination of the sets of differently colored LEDs of the pixel respectively which corresponds to the plurality of coordinated signals separately delivered to each set of LEDs of each pixel;

changing said one composite color at each pixel from time to time as said plurality of coordinated signals changes whereby successive integrated images each comprising varying array of composite colors across the spectrum are sequentially visually illuminated on the matrix display.

24. A method by which composite color images are successively displayed on a matrix display comprising:

presenting a plurality of multi-color solid state LED pixels arranged in a pattern for visual observation;

constructing each multi-color pixel so that it comprises a plurality of differently colored sets of LEDs;

electrically interconnecting each set of differently colored LEDs of each pixel by separate conductor means;

issuing separate but coordinated signals along said separate conductor means respectively, the signals being representative of the desired color and intensity to be obtained at each point in time from each set of differently colored LEDs of each pixel of the display;

communicating said signals separately along said separate conductor means respectively to each set of differently colored LEDs of each pixel;

obtaining a single composite visual color at least many of the pixels at each point in time comprising a blended integration of the colors independently displayed at each set of LEDs forming the pixel which corresponds to the separate illumination duration determining signals simultaneously delivered to the differently colored sets of LEDs of each pixel;

displaying an integrated matrix image of many colors over a large number of color combination across the spectrum comprising a visual integration of the single composite visual color being displayed at said pixels at each point in time; and

changing the images and colors, across said large number of color combinations, of said display from time to time as the intensity level signals to the respective sets of LEDs of each pixel change.

25. A method of sequentially presenting different images each comprising a different arrangement of many colors from a wide range of colors comprising the steps of:

simultaneously issuing separate signals from a source;

separately communicating the separate signals respectively to electrically independent sets of LEDs of each of many pixels of a matrix display which signals collectively represent many colors of the large number of color combinations;

controlling the period of illumination and intensity of each set of LEDs at each pixel with said signals to exactly and simultaneously produce (a) an LED color mix at each pixel visually comprising a single desired color from the large number of color combinations, and (b) a large readable display image comprising an image integration of the single mixed colors at each pixel; and

repeating said issuing, separately communicating and controlling steps to change the single composite color visually displayed at selected pixels and the integrated visual image of the display to another desired pattern of many colors.

26. LED illumination apparatus adapted to a large LED matrix display system which provides a large number of color combinations, said LED illumination apparatus comprising:

signal source means which provide an independent signal for each primary color;

LED pixel means wherein each pixel comprises a plurality of LEDs comprising different primary colors, said LED pixel means providing one apparent source of light in the large matrix display, said light comprising an integral sum of the light from said LEDs to provide one color at any one point in time of a large number of color combinations;

LED means interconnected in series and parallel diode matrices which provide X-Y addressing means without non-LED integrated circuits in said LED matrix;

pulse wave modulation means comprising;

LED addressing and exciting means which address and excite each LED of each pixel to illumination at the same instant;

LED illumination extinguishing means which extinguish each LED independently at a variable time after the LEDs of a pixel have been illuminated, providing a duration of LED ON time which is dependent upon the strength of the signal from the signal source means for the color to be emitted by that LED;

pixel addressing means which provide X-Y row, column addressing of pixels which selectively address multiple columns and groups of rows to reduce peak current levels and provide refresh rates which will eliminate apparent flicker;

pixel module means, in combination, providing arrays of apparent point sources of light which provide a picture comprising a large number of color combinations.

27. LED illumination apparatus according to claim 26 wherein pulse wave modulation means comprise PROM memory means which provide a predetermined linear and non-linear conversion of signals from said signal source means to time modulation means which provide corrections for variations in performance of LEDs of different colors across the range of signal strengths as received from the signal source means.

28. LED illumination apparatus according to claim 26 wherein LED pixel means comprise pixel module means which provide serial/parallel arrays of LEDs with at least two LEDs of each color, said pixel module means providing levels of illumination required for large arrays and providing LED redundancy for increased pixel reliability.

29. LED illumination apparatus according to claim 26 wherein pulse wave modulation means comprise refresh means which provide refresh rates which are of a sufficiently high frequency that a viewer does not perceive flicker caused by variable illumination time of the individual LEDs.

30. An LED matrix display system for large number of color displays, comprising:

message control means which provide a means of providing previously prepared messages for display;

video digitizer means which provide digitized voltage levels of video signals;

mode selection means which select between signals processed through the message control means and video digitizer means;

memory means which provide retrievable storage for digitized voltage levels of video signals;

LED illumination means which illuminate all colors of each pixel at a synchronous rate and time;

pulse wave modulation means which extinguish the light individually from sets of LEDs by color within each pixel at variable times after synchronous illumination to provide a large number of color combinations;

pixel addressing means which provide X-Y row, column addressing of pixels which selectively address multiple columns and groups of rows of LEDs to reduce peak current levels and provide refresh rates which minimize apparent flicker;

pixel module means which provide serial/parallel arrays of primary colored LED means, said pixel module means providing levels of illumination required for large arrays and providing redundancy for increased pixel reliability;

primary colored LED means providing light integrally summing to provide one color of a large number of color combinations;

multiple pixel module means, in combination, providing an array of apparent point sources of light which provide a picture comprising a large number of color combinations.

31. An LED matrix display system for large number of color combination displays according to claim 30 wherein pulse wave modulation means comprise linear and non-linear pulse modulation means which provide a predetermined linear and non-linear conversion of signals from said memory means to time modulation means which provide corrections for variations in performance of LEDs of different colors across the range of signal strengths as received from the memory means.

32. A LED matrix display system for large number of color combinations LED displays according to claim 31 wherein linear and non-linear pulse modulation means comprise PROM means which provide digital patterns which control the time each LED is on for each voltage level delivered from the memory means whereby the corrections for variations in performance of LEDs of different colors across the range of signal strengths as received from the memory means are made.

33. An LED matrix display system for large number of color combinations LED displays according to claim 32 wherein PROM means comprise high frequency operational cycle means by which the PROM means is reread at a higher rate than the rate at which pixels colors are changed to provide improved refresh means to minimize flicker.

34. LED illumination apparatus adapted to a large LED matrix display system which provides an infinite number of color combinations, said LED illumination apparatus comprising:

signal source means which provide an independent signal for each primary color;

color demodulator means which separate a color signal into three color driven analog signals;

pixel module means which comprise primary colored LED pixel means, said pixel module means providing one apparent source of light in the large matrix LED display.

pulse wave modulation means comprising;

LED addressing and exciting means which address and excite each LED of each pixel to illumination at the same instant;

LED illumination extinguishing means which extinguish each LED independently at a variable time after the LEDs of a pixel have been illuminated, providing a duration of LED ON time which is dependent upon the strength of the signal from the signal source means for the color to be emitted by that LED;

pixel addressing means which provide X-Y row, column addressing of pixels which selectively address single columns and rows to reduce peak current levels and operate synchronously with an incoming video signal;

multiple pixel module means, in combination, providing an array of apparent point sources of light which provide a picture comprising an infinite number of color combinations.

35. LED illumination apparatus according to claim 34 wherein pulse wave modulation means comprise analog gating means which use analog signals directly without analog to digital conversion, the analog gating means further comprising:

sample and hold means which receive and hold in analog memory, voltage levels for signals for each LED from the signal source means;

reference waveform means which provide a time varying waveform which provides a repeatable time varying voltage signal which can be used comparatively to provide a time when an LED should be extinguished;

analog time gating means which compare voltage levels held in memory by the sample and hold means and provided by the reference waveform means and which extinguish illumination of an addressed LED at the time the ratio of the two signals cross unity.

36. An LED matrix display system for infinite variety of color combinations LED displays, comprising:

message control means which provide previously prepared messages for display;

video input receiving means which receive signals to be sent to a synchronous separator means;

synchronous separator means which separate incoming video input signals into vertical timing signals, frame timing signals, and signal to be sent to a color demodulator means;

color demodulator means which separate a color signal into three color driven analog signals;

column sample shift register means which provides gate timing means at which time sample and hold circuits are set for each pixel;

pixel addressing means which provide X-Y row addressing of pixels which selectively address single columns and rows;

pulse wave modulation means which extinguish the light individually from sets of LEDs by color within each pixel at variable times after synchronous illumination to provide an infinite number of color combinations;

LED pixel means comprising red, blue, and green LED light emitting means, the output of which integrally sums to provide one color of an infinite number of color combinations;

pixel module means, in combination, providing an array of apparent point sources of light which provide a picture comprising an infinite number of color combinations.

37. An LED matrix display system for infinite variety of color combinations LED displays according to claim 36 wherein pulse modulation means comprise analog sample and hold means and reference wave means which are gated to provide variable time periods which control the time each Led is on for each video signal voltage level.

38. An LED matrix display system for infinite variety of color combinations LED displays according to claim 37 wherein reference wave means comprise a cyclic frequency which is higher than the rate at which pixels colors are changed to provide improved refresh means to minimize flicker.