Automatic gamma correction system for displays

• US 6,593,934 B1
• Filed: 11/16/2000
• Issued: 07/15/2003
• Est. Priority Date: 11/16/2000
• Status: Active Grant

• Current Assignee: InnoLux Corporation
• Original Assignee: Industrial Technology Research Institute
• Inventors: Shen, Yuh-Ren, Liaw, Ming-Jiun, Yang, Ho-Hsin
• Primary Examiner(s): Luu, Matthew
• Application Number:
  US09/714,473
• Time in Patent Office: 971 Days
• Field of Search: 345/589, 345/590, 345/88, 345/89, 345/100, 345/101, 348/674
• US Class Current: 345/590
• 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 2320/029 by monitoring one or more pixels in the display panel, e.g. by monitoring a fixed reference pixel
• CPC Class Codes: G09G 2320/041 Temperature compensation
• 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 2320/08 Arrangements within a display terminal for setting, manually or automatically, display parameters of the display terminal
• CPC Class Codes: G09G 3/2092 Details of a display terminals using a flat panel, the details relating to the control arrangement of the display terminal and to the interfaces thereto suitable for both CRT and flat panel G09G5/003; specific for a CRT G09G1/165
• CPC Class Codes: H04N 5/202 Gamma control circuits for controlling camera response irrespective of the scene brightness H04N23/82
• CPC Class Codes: H04N 5/66 Transforming electric information into light information scanning details H04N3/00
• CPC Class Codes: H04N 9/12 Picture reproducers H04N9/11 takes precedence
• CPC Class Codes: H04N 9/3147 Multi-projection systems displays in general H04N9/12; video walls G06F3/1446, G09G2300/026

Abstract

This invention is related to an automatic Gamma correction system in which a novel display driving circuitry is designed with a digital/analog converter (DAC), wherein the Gamma reference voltages as well as the corresponding gray-scale values are adjustable. Therefore, the present invention provides a greater degree of freedom for the realization of the correction of Gamma parameters so as to fit the curve representing the transfer function of the destination gray-scale values and the voltages required by the display driving circuitry.

Claims

1. An automatic Gamma parameter correction system for displays, comprising:

a plurality of sensors, disposed inside said display or outside said display for obtaining a voltage-to-luminance curve so as to evaluate a set of Gamma reference voltages;

a main controller, connected to said sensors to serve as a main control circuit for said system, and further including a central process unit (CPU) and a memory for parameter calculation and data storage;

a programmable Gamma voltage generating means, connected to said main controller and generating said set of Gamma reference voltages output into the input terminals of a set of programmable switches according to said Gamma reference voltages evaluated by a central process unit in said main controller, therefor said Gamma reference voltages are adjustable;

a set of programmable switches, connected to said programmable Gamma voltage generating means so as to receive an output voltage and also connected to a switch control unit so as to interconnect the output terminals of said programmable switches and a voltage dividing circuit with a set of corresponding gray-scale values according to gray-scale signals with respect to a switch control unit;

a switch control unit, having an input terminal connected to said main controller and the output terminals connected to said programmable switches, so that said switch control unit interconnects the output terminals of said programmable switches and said voltage dividing circuit having a series divided voltage points and then applies said Gamma reference voltages to the corresponding divided voltage points according to said corresponding gray-scale signals delivered from said central process unit, therefor said corresponding gray-scale signals are adjustable; and

a voltage dividing circuit, implemented by using a digital-to-analog converter (DAC), having an input terminal connected to the output terminals of said programmable switches;

wherein for an N-gray-scale system, said voltage dividing circuit output at least 2^N divided voltages, and then said voltages are further connected to a series of output buffers;

wherein during Gamma parameter correction operation, the parameters related to said system are determined;

a voltage-to-luminance curve of said display is then evaluated by using said sensors according to said driving voltage range determined by the parameters;

later, a destination function of said gray-scale-to-voltage transfer curve is determined by said main controller, and said transfer curve is further implemented by said voltage dividing circuit;

then, said Gamma reference voltages required by said voltage dividing circuit as well as said corresponding gray-scale values are evaluated, that is both the Gamma reference voltages and the corresponding gray-scale values are adjustable by CPU evaluating;

further, said Gamma reference voltages and said corresponding gray-scale values are interconnected by said programmable switches and said switch control unit, so as to build up a gray-scale-to-voltage curve; and

said voltage dividing circuit outputs corresponding voltages to said output buffers according to said input gray-scale values of the image.

2. The automatic Gamma parameter correction system as recited in claim 1, wherein said sensors can be light sensors, temperature sensors, pixel voltage sensors, or a pixel charging/discharging current sensors used for measuring at least one parameter so as to evaluate said voltage-to-luminance curve or said Gamma voltage as well as said corresponding digital gray-scale value required to establish a gray-scale-to-voltage destination curve for driving displays during said operation of said system.

3. The automatic Gamma parameter correction system as recited in claim 1, wherein said memory of said main controller can store at least one gray-scale-to-luminance destination curve and said a set of Gamma reference voltages evaluated by said central process unit as well as said corresponding gray-scale values.

4. The automatic Gamma parameter correction system as recited in claim 1, wherein said central process unit includes an operation of loading said voltage-to-luminance curve and said gray-scale-to-luminance destination curve and determining said Gamma reference voltage range according to luminance, contrast and color temperature, so as to fit said curve representing said transfer function of said destination gray-scale values and said voltages required to drive the working displays properly.

5. The automatic Gamma parameter correction system as recited in claim 1, wherein said central process unit includes an operation of optimizing by using programs to evaluate said Gamma reference voltages and said corresponding gray-scale values of said desired gray-scale-to-luminance destination curve.

6. The automatic Gamma parameter correction system as recited in claim 1, wherein said programmable Gamma voltage generating means is composed of a digital-to-analog converter (DAC) connected to a plurality of buffers, so as to output said Gamma reference voltages by adjusting said received destination function of said Gamma voltage outputs by said main controller.

7. The automatic Gamma parameter correction system as recited in claim 1, wherein the number of said programmable switches is smaller than of the number of said output voltages of said voltage dividing circuit.

8. The automatic Gamma parameter correction system as recited in claim 1, wherein said voltage dividing circuit is composed of a plurality of resistors.

9. The automatic Gamma parameter correction system as recited in claim 1, wherein said voltage dividing circuit is composed of a plurality of capacitors.

10. The automatic Gamma parameter correction system as recited in claim 1, wherein said voltage dividing circuit is composed of a plurality of resistors and capacitors.

11. The automatic Gamma parameter correction system as recited in claim 1, wherein said voltage dividing circuit is further connected to a plurality of buffers so as to improve the drivability for a next stage.

12. A method for measuring the voltage-to-luminance curve for automatic Gamma parameter correction for displays, comprising the steps of:

(a) determining related parameters for said displays;

(b) determining a driving voltage range according to said Gamma parameters;

(c) measuring a voltage-to-luminance curve of said displays;

(d) determining a destination function of gray-scale-to-voltage transfer curve;

(e) evaluating a set of Gamma reference voltages required by a voltage dividing circuit as well as a set of corresponding gray-scale values;

(f) interconnecting said Gamma reference voltages and said corresponding gray-scale values by using a set of programmable switches and a switch control unit, so as to build up a gray-scale-to-voltage curve; and

(g) outputting corresponding voltages to a series of output buffers by using said voltage dividing circuit according to a set of input gray-scale values of the image.

13. A method for measuring the operating related parameter (temperature or/and luminance) for automatic Gamma parameters correction for displays, comprising the steps of:

(a) measuring an operating related parameter (temperature or/and luminance) of said displays;

(b) determining a voltage-to-luminance curve of said displays by using table-checking;

(c) determining a destination function of a gray-scale-to-voltage transfer curve;

(d) evaluating a set of Gamma reference voltages required by a voltage dividing circuit as well as a set of corresponding gray-scale values;

(e) interconnecting said Gamma reference. voltages and said corresponding gray-scale values by using a set of programmable switches and a switch control unit, so as to build up a gray-scale-to-voltage curve; and

(f) outputting corresponding voltages to a series of output buffers by using said voltage dividing circuit according to a set of input gray-scale values of the image.

14. A method for measuring the operating related parameter (temperature or/and luminance) for automatic Gamma parameter correction for displays, comprising the steps of:

(a) measuring an operating related parameter (temperature or/and luminance) of said displays;

(b) determining a set of Gamma reference voltages required by said voltage dividing circuit as well as a set of corresponding gray-scale values by using table-checking;

(c) interconnecting said Gamma reference voltages and said corresponding gray-scale values by using a set of programmable switches and a switch control unit, so as to build up a gray-scale-to-voltage curve; and

(d) outputting corresponding voltages to a series of output buffers by using said voltage dividing circuit according to a set of input gray-scale values of the image.

15. An automatic Gamma parameter correction system accompanied with at least a conventional data driver for displays, comprising:

a plurality of sensors, disposed inside said display for sensing the relative luminance of a series of voltage signals so as to obtain a voltage-to-luminance curve;

a main controller, connected to said sensors to serve as a main control circuit for said system, and further including a central process unit (CPU) and a memory for parameter calculation and data storage;

a programmable Gamma voltage generating means, connected to said main controller and generating a set of Gamma reference voltages output into the input terminals of said data driver according to a set of reference voltages evaluated by said central process unit in said main controller; and

at least a data driver, directly connected to said programmable Gamma voltage generating means and generating image driving signals delivered into said display according to said Gamma reference voltage outputs by said programmable Gamma voltage generating means.

16. The automatic Gamma parameter correction system as recited in claim 15, wherein said sensors can be light sensors, temperature sensors, pixel voltage sensors, or a pixel charging/discharging current sensors used for measuring at least one parameter so as to evaluate said voltage-to-luminance curve or said Gamma voltages required by said data driver during said operation of said system.

17. A method for measuring the voltage-to-luminance curve for automatic Gamma parameter correction for displays, comprising the steps of:

(a) determining related parameters for said displays;

(b) determining a driving voltage range according to said Gamma parameters;

(c) repeating (a) if said determined parameters exceed a driving voltage range for said displays;

(d) measuring a voltage-to-luminance curve of said displays;

(e) determining a destination function of gray-scale-to-voltage transfer curve;

(f) evaluating a set of Gamma reference voltages required by a voltage dividing circuit as well as a set of corresponding gray-scale values;

(g) interconnecting said Gamma reference voltages and said corresponding gray-scale value by using a set of programmable switches and a switch control unit, so as tobuild up a gray-scale-to-voltage curve; and

(h) outputting a set of corresponding voltages according to a set of input gray-scale values of the image.

18. The automatic Gamma parameter correction method as recited in claim 17, wherein said related parameters in said step (a) include at least contrast, luminance, color temperature, and said Gamma values of image.

19. The automatic Gamma parameter correction method as recited in claim 17, wherein said step (b) comprises:

providing a lowest gray-scale voltage and a highest gray-scale voltage (denoted by Vmin and Vmax, respectively) so as to perform voltage adjustment;

recoding Vmin and Vmax and going forwards to the next step if said luminance reaches said determined value;

providing a new lowest gray-scale voltage and a new highest gray-scale voltage and performing voltage adjustment again until said determined value is reached if said luminance does not reach said determined value.

20. The automatic Gamma parameter correction method as recited in claim 17, wherein said step (d) comprises:

providing an original gray-scale-to-voltage transfer curve and outputting a series of gray-scale patterns which are to be measured by a plurality of sensors so as to obtain a gray-scale-to-luminance curve; and

evaluating a voltage-to-luminance curve according to said original gray-scale-to-voltage transfer curve.

21. The automatic Gamma parameter correction method as recited in claim 17, wherein said step (d) comprises:

providing a completely white image frame; and

continuously measuring the luminance of said completely white image frame under different reference voltages and obtaining a voltage-to-luminance curve, wherein

the digital code of a completely white image frame corresponds to the first or the last external reference voltage and thus the external reference voltage range varies continuously.

22. The automatic Gamma parameter correction method as recited in claim 17, wherein said step (d) further comprises:

performing table-checking, to obtain the numerical data of said voltage-to-luminance curve.

23. The automatic Gamma parameter correction method as recited in claim 17, wherein said step (e) comprises:

considering the voltage-to-luminance curve, the Gamma transfer curve for image transmission, and the Gamma value of the image (γ

_image);

determining a voltage-to-luminance curve; and

determining a gray-scale-to-voltage transfer curve according to said voltage-to-luminance curve of said display.

24. The automatic Gamma parameter correction method as recited in claim 17, wherein said step (f) comprises:

optimizing said Gamma reference voltages and said corresponding gray-scale values by using computer software;

loading said optimized result into said displays.

25. The automatic Gamma parameter correction method as recited in claim 17, wherein said step (g) comprises:

performing table-checking, to obtain the numerical data of a set of Gamma reference voltages as well as a set of corresponding gray-scale values.