Flat panel display screen with programmable gamma functionality

• US 6,359,389 B1
• Filed: 06/09/2000
• Issued: 03/19/2002
• Est. Priority Date: 06/09/2000
• Status: Expired due to Term

• Current Assignee: RPX Corporation
• Original Assignee: Silicon Graphics Incorporated (Graphics Properties Holdings, Inc.)
• Inventors: Medina, Oscar I., Mendelson, Jonathan D., Evanicky, Daniel E.
• Primary Examiner(s): Wong, Don
• Assistant Examiner(s): Vu, Jimmy T.
• Application Number:
  US09/590,887
• Time in Patent Office: 648 Days
• Field of Search: 315/169.1, 315/169.3, 315/169.4, 345/58, 345/60
• US Class Current: 315/169.1
• CPC Class Codes: G09G 2310/027 Details of drivers for data electrodes, the drivers handling digital grey scale data, e.g. use of D/A converters
• CPC Class Codes: G09G 2320/0276 for the purpose of adaptation to the characteristics of a display device, i.e. gamma correction
• CPC Class Codes: G09G 2320/0606 Manual adjustment
• CPC Class Codes: G09G 2320/0673 for control of gamma adjustment, e.g. selecting another gamma curve
• CPC Class Codes: G09G 3/2011 by amplitude modulation
• CPC Class Codes: G09G 3/3688 suitable for active matrices only
• CPC Class Codes: G09G 3/3696 Generation of voltages supplied to electrode drivers

Abstract

A flat panel display having a programmable gamma without incidental loss in gray scale resolution. In one embodiment, the flat panel display is a liquid crystal display (LCD). The invention includes applying and adjusting a set of gamma controlling voltages to the DC reference circuit (a.k.a. ladder voltages) of an LCD module producing a change in the gamma response (or profile) of the LCD module without incidental loss of gray scale resolution. An adjustable ladder circuit (ALC) is thereby realized. Separate ALCs can be provided for red, green and blue primaries. By adjusting, in a predetermined fashion, the reference voltages applied to the row and column drivers of an LCD display, the gamma response of the LCD can be changed to a different value. Because the input digital signals are not affected, the same color resolution and dynamic range are maintained. The DC reference circuit can be a multi-node voltage divider. These voltage nodes are applied to the row and column drivers of the LCD module to control the ON/OFF states of each red, green and blue sub-pixel. The input digital signals provided by the host'"'"'s graphic source or software application modulate these voltage nodes to produce the desired gray scale value applying across the LCD sub-pixel a percentage of DC reference voltages.

Claims

1. A monitor comprising:

a) a flat panel display comprising;

a matrix of pixels;

row drivers coupled to said matrix; and

column drivers coupled to said matrix, said row and column drivers for converting digital color data into voltages for application to said matrix;

b) a timing controller circuit operable to produce timing signals for sequencing digital data to said row and column drivers;

c) a reference voltage circuit for providing a plurality of discrete analog reference voltages;

d) an adjustment circuit coupled to said reference voltage circuit and operable to produce a plurality of adjusted discrete analog reference voltages supplied to said row and column drivers, said adjustment circuit operable to alter the gamma profile of said flat panel display without degrading its gray scale resolution; and

e) a controller device for generating control signals, said control signals for controlling said adjustment circuit to selectively implement a desired gamma profile of said flat panel display and wherein said controller device is a software controller device.

2. A monitor as described in claim 1 wherein said reference voltage circuit and said adjustment circuit are an adjustable ladder circuit.

3. A monitor as described in claim 2 wherein said adjustable ladder circuit comprises a plurality of serially coupled voltage stages, each stage comprising a programmable summing amplifier and each stage operable to generate a respective adjusted discrete analog reference voltage.

4. A monitor as described in claim 1 wherein said flat panel display screen is a liquid crystal display (LCD) device.

5. A display device comprising:

a) a flat panel display comprising;

a matrix of liquid crystal display (LCD) elements;

row drivers coupled to said matrix; and

column drivers coupled to said matrix, said row and column drivers for converting digital color data into voltages for application to said matrix;

b) a timing controller circuit operable to produce timing signals for sequencing digital data through said row and column drivers;

c) a reference voltage circuit for providing a plurality of discrete analog reference voltages;

d) an adjustment circuit coupled to said reference voltage circuit and operable to produce a plurality of adjusted discrete analog reference voltages supplied to said row and column drivers, said adjustment circuit operable to alter the gamma profile of said flat panel display without degrading its gray scale resolution; and

e) a controller device for generating control signals, said control signals for controlling said adjustment circuit to implement a desired gamma profile of said flat panel display and wherein said controller device is a software controller device.

6. A display device as described in claim 5 wherein said matrix is a color matrix having three or more primary colors (RGB).

7. A display device as described in claim 5 wherein said reference voltage circuit and said adjustment circuit are an adjustable ladder circuit.

8. A display device as described in claim 7 wherein said adjustable ladder circuit comprises a plurality of serially coupled voltage stages, each stage comprising a programmable summing amplifier and each stage operable to generate a respective adjusted discrete analog reference voltage.

9. In a display device, a method of generating an image comprising the steps of:

a) receiving digital color data representing pixels for display;

b) converting said digital color data into voltages for application to a flat panel display screen, wherein said step b) comprises the steps of;

b1) programming a plurality of programmable analog reference voltages of an adjustable ladder circuit in order to obtain a desired gamma profile of said flat panel display screen without degrading its gray scale resolution, wherein said step b1) is performed by a software controller device and further comprising the step of accessing said desired gamma profile from a user input; and

b2) supplying said plurality of programmable analog reference voltages and digital color data to row and column drivers to convert said digital color data into said voltages; and

c) applying said voltages said flat panel display screen, said flat panel display screen having a matrix of pixels comprising rows and columns.

10. A method as described in claim 9 wherein said flat panel display device is a liquid crystal display (LCD) device.

11. A method as described in claim 9 further comprising the step of generating required timing signals for addressing said row and column drivers of said flat panel display screen.

12. A method as described in claim 9 wherein said adjustable ladder circuit comprises a plurality of serially coupled voltage stages, each stage having a programmable summing amplifier and each stage generating a discrete programmable analog reference voltage.

13. A method as described in claim 9 further comprising the step of said display screen automatically responding to an input device to readjust its gamma profile to mach said input device.

14. A method as described in claim 13 wherein said input device is a digital camera system.

15. A monitor comprising:

a) a flat panel display comprising;

a matrix of pixels;

row drivers coupled to said matrix; and

column drivers coupled to said matrix, said row and column drivers for converting digital color data into voltages for application to said matrix;

b) a timing controller circuit operable to produce timing signals for sequencing digital data to said row and column drivers;

c) a reference voltage circuit for providing a plurality of discrete analog reference voltages;

d) an adjustment circuit coupled to said reference voltage circuit and operable to produce a plurality of adjusted discrete analog reference voltages supplied to said row and column drivers, said adjustment circuit operable to alter the gamma profile of said flat panel display without degrading its gray scale resolution; and

e) a controller device for generating control signals, said control signals for controlling said adjustment circuit to selectively implement a desired gamma profile of said flat panel display, and wherein said controller device comprises potentiometer circuits.

16. A monitor as described in claim 15 wherein said reference voltage circuit and said adjustment circuit are an adjustable ladder circuit.

17. A monitor as described in claim 16 wherein said adjustable ladder circuit comprises a plurality of serially coupled voltage stages, each stage comprising a programmable summing amplifier and each stage operable to generate a respective adjusted discrete analog reference voltage.

18. A monitor as described in claim 15 wherein said flat panel display screen is a liquid crystal display (LCD) device.

19. A display device comprising:

a) a flat panel display comprising;

a matrix of liquid crystal display (LCD) elements;

row drivers coupled to said matrix; and

column drivers coupled to said matrix, said row and column drivers for converting digital color data into voltages for application to said matrix;

b) a timing controller circuit operable to produce timing signals for sequencing digital data through said row and column drivers;

c) a reference voltage circuit for providing a plurality of discrete analog reference voltages;

d) an adjustment circuit coupled to said reference voltage circuit and operable to produce a plurality of adjusted discrete analog reference voltages supplied to said row and column drivers, said adjustment circuit operable to alter the gamma profile of said flat panel display without degrading its gray scale resolution; and

e) a controller device for generating control signals, said control signals for controlling said adjustment circuit to implement a desired gamma profile of said flat panel display and wherein said controller device comprises potentiometer circuits.

20. A display device as described in claim 19 wherein said matrix is a color matrix having three or more primary colors (RGB).

21. A display device as described in claim 19 wherein said reference voltage circuit and said adjustment circuit are an adjustable ladder circuit.

22. A display device as described in claim 21 wherein said adjustable ladder circuit comprises a plurality of serially coupled voltage stages, each stage comprising a programmable summing amplifier and each stage operable to generate a respective adjusted discrete analog