Method For Driving Quad-Subpixel Display

• US 20120256938A1
• Filed: 04/07/2011
• Published: 10/11/2012
• Est. Priority Date: 04/07/2011
• Status: Active Grant

• Current Assignee: Universal Display Corporation
• Original Assignee: Universal Display Corporation
• Inventors: So, Woo-Young
• Granted Patent: US 8,902,245 B2
• Time in Patent Office: Days
• US Class Current: 345/589
• CPC Class Codes: G09G 2300/0443 with several sub-pixels for the same colour in a pixel, not specifically used to display gradations G09G3/364 takes precedence
• CPC Class Codes: G09G 2300/0452 Details of colour pixel setup, e.g. pixel composed of a red, a blue and two green components
• CPC Class Codes: G09G 2320/046 Dealing with screen burn-in prevention or compensation of the effects thereof
• CPC Class Codes: G09G 2320/0693 Calibration of display systems
• CPC Class Codes: G09G 2340/06 Colour space transformation
• CPC Class Codes: G09G 3/3208 organic, e.g. using organic light-emitting diodes [OLED]

Abstract

A device that may be used as a multi-color pixel is provided. The device has a first organic light emitting device, a second organic light emitting device, a third organic light emitting device, and a fourth organic light emitting device. The device may be a pixel of a display having four sub-pixels. The first device may emit red light, the second device may emit green light, the third device may emit light blue light and the fourth device may emit deep blue light. A method of displaying an image on such a display is also provided, where the image signal may be in a format designed for use with a three sub-pixel architecture, and the method involves conversion to a format usable with the four sub-pixel architecture.

Claims

1. A method of displaying an image on a display, comprising:

receiving a display signal that defines an image, wherein

a display color gamut is defined by three sets of CIE coordinates (x_RI, y_RI), (x_GI, y_GI), (x_BI, y_BI)

the display signal is defined for a plurality of pixels;

for each pixel, the display signal comprises a desired chromaticity and luminance defined by three components R_I, G_I and B_I that correspond to luminances for three sub-pixels having CIE coordinates (x_RI, y_RI), (x_GI, y_GI), and (x_BI, y_BI), respectively, that render the desired chromaticity and luminance;

wherein the display comprises a plurality of pixels, each pixel including an R sub-pixel, a G sub-pixel, a B1 sub-pixel and a B2 sub-pixel, wherein;

each R sub-pixel comprises a first organic light emitting device that emits light having a peak wavelength in the visible spectrum of 580-700 nm, further comprising a first emissive layer having a first emitting material;

each G sub-pixel comprises a second organic light emitting device that emits light having a peak wavelength in the visible spectrum of 500-580 nm, further comprising a second emissive layer having a second emitting material;

each B1 sub-pixel comprises a third organic light emitting device that emits light having a peak wavelength in the visible spectrum of 400-500 nm, further comprising a third emissive layer having a third emitting material;

each B2 sub-pixel comprises a fourth organic light emitting device that emits light having a peak wavelength in the visible spectrum of 400 to 500 nm, further comprising a fourth emissive layer having a fourth emitting material;

the third emitting material is different from the fourth emitting material; and

the peak wavelength in the visible spectrum of light emitted by the fourth organic light emitting device is at least 4 nm less than the peak wavelength in the visible spectrum of light emitted by the third organic light emitting device;

wherein each of the R, G, B1 and B2 sub-pixels has CIE coordinates (x_R,y_R), (x_G,y_G), (x_B1,y_B1) and (x_B2,y_B2), respectively;

wherein each of the R, G, B1 and B2 sub-pixels has a maximum luminance Y_R, Y_G, Y_B1 and Y_B2, respectively, and a signal component R_C, G_C B1_C and B2_C, respectively;

wherein a plurality of color spaces are defined, each color space being defined by the CIE coordinates of three of the R, G, B1 and B2 sub-pixels,

wherein every chromaticity of the display gamut is located within at least one of the plurality of color spaces;

wherein at least one of the color spaces is defined by the R, G and B1 sub-pixels;

wherein the color spaces are calibrated by using a calibration chromaticity and luminance having a CIE coordinate (x_C, y_C) located in the color space defined by the R, G and B1 sub-pixels, such that;

a maximum luminance is defined for each of the R, G, B1 and B2 sub-pixels,

for each color space, for chromaticities located within the color space, a linear transformation is defined that transforms the three components R_I, G_I and B_I into luminances for the each of the three sub-pixels having CIE coordinates that define the color space that will render the desired chromaticity and luminance defined by the three components R_I, G_I and B_I;

displaying the image by, for each pixel;

choosing one of the plurality of color spaces that includes the desired chromaticity of the pixel;

transforming the R_I, G_I and B_I components of the signal for the pixel into luminances for the three sub-pixels having CIE coordinates that define the chosen color space;

emitting light from the pixel having the desired chromaticity and luminance using the luminances resulting from the transformation of the R_I, G_I and B_I components.

2. The method of claim 1, wherein:

two color spaces are defined;

a first color space defined by the CIE coordinates of the R, G and B1 sub-pixels, and a second color space defined by the CIE coordinates of the R, G and B2 sub-pixels.

3. The method of claim 2, wherein:

the first color space is chosen for pixels having a desired chromaticity located within the first color space; and

the second color space is chosen for pixels having a desired chromaticity located within a subset of the second color space defined by the R, B1 and B2 sub-pixels.

4. The method of claim 3, wherein the color spaces are calibrated by using a calibration chromaticity and luminance having a CIE coordinate (x_C, y_C) located in the color space defined by the R, G and B1 sub-pixels by:

defining maximum luminances (Y′

_R, Y′

_G and Y′

_B1) for the color space defined by the R, G and B1 sub-pixels, such that emitting luminances Y′

_R, Y′

_G and Y′

_B1 from the R, G and B1 sub-pixels, respectively, renders the calibration chromaticity and luminance;

defining maximum luminances (Y″

_R, Y″

_G and Y″

_B2) for the color space defined by the R, G and B2 sub-pixels, such that emitting luminances Y″

_R, Y″

_G and Y″

_B2 from the R, G and B2 sub-pixels, respectively, renders the calibration chromaticity and luminance;

defining maximum luminances (Y_R, Y_G, Y_B1 and Y_B2) for the display, such that Y_R=max (Y_R′

, Y_R″

), Y_G=max (Y_G′

, Y_G″

), Y_B1=Y′

_B1, and Y_B2 Y″

_B2;

5. The method of claim 4, wherein:

the linear transformation for the first color space is a scaling that transforms R_I into R_C, G_I into G_C, and B_I into B1_C; and

the linear transformation for the second color space is a scaling that transforms R_I into R_C, G_I into G_C, and B_I into B2_C.

6. The method of claim 2, wherein the CIE coordinates of the B1 sub-pixel are located outside the second color space.

7. The method of claim 1, wherein:

two color spaces are defined;

a first color space defined by the CIE coordinates of the R, G and B1 sub-pixels, and a second color space defined by the CIE coordinates of the R, B1 and B2 sub-pixels.

8. The method of claim 7, wherein:

the first color space is chosen for pixels having a desired chromaticity located within the first color space; and

the second color space is chosen for pixels having a desired chromaticity located within the second color space.

9. The method of claim 7, wherein the CIE coordinates of the B1 sub-pixel are located outside the second color space.

10. The method of claim 1, wherein:

the CIE coordinates of the B1 sub-pixel are located inside a color space defined by the CIE coordinates of the R, G and B2 sub-pixels;

three color spaces are defined;

a first color space defined by the CIE coordinates of the R, G and B1 sub-pixels;

a second color space defined by the CIE coordinates of the G, B2 and B1 sub-pixels; and

a third color space defined by the CIE coordinates of the B2, R and B1 sub-pixels.

11. The method of claim 10, wherein:

the first color space is chosen for pixels having a desired chromaticity located within the first color space; and

the second color space is chosen for pixels having a desired chromaticity located within the second color space; and

the third color space is chosen for pixels having a desired chromaticity located within the third color space.

12. The method of claim 1, wherein the CIE coordinates are 1931 CIE coordinates.

13. The method of claim 1, wherein the calibration color has a CIE coordinate (x_C, y_C) such that 0.25<

x_C<

0.4 and 0.25<

y_C<

0.4.

14. The method of claim 1, wherein the CIE coordinate of the B1 sub-pixel is located outside the triangle defined by the R, G and B2 CIE coordinates.

15. The method of claim 1, wherein the CIE coordinate of the B1 sub-pixel is located inside the triangle defined by the R, G and B2 CIE coordinates.

16. The method of claim 1, wherein the first, second and third emitting materials are phosphorescent emissive materials, and the fourth emitting material is a fluorescent emitting material.