Gamma curve compensating method, gamma curve compensating circuit and display system using the same

1. A gamma curve compensating circuit used in a display system, comprising:

an image generating circuit, generating an original output image signal according to an input image signal received by the display system;

a grey-scale insertion determining circuit, determining a plurality of grey-scale luminance of a grey-scale image to be inserted according to the input image signal and outputting the grey-scale image;

a multiplexer, having a first input terminal electrically coupled to the grey-scale insertion determining circuit and a second input terminal electrically coupled to the image generating circuit, and the multiplexer being used for providing an original display signal comprising the grey-scale image and the original output image signal; and

a looking up and compensating circuit, electrically coupled to the multiplexer for receiving the original display signal, the looking up and compensating circuit providing a plurality of look-up tables, selecting a specific look-up table from the look-up tables according to the grey-scale luminance of the grey-scale image, and performing a gamma-curve compensating on the original display signal based on the specific look-up table;

wherein, the grey-scale image comprises a plurality of divisions, each one of the divisions corresponds to one of the plurality of grey-scale luminance, and the grey-scale luminance of each one of the divisions is determined according to the grey-scale luminance of another adjacent division of the plurality of divisions.

2. The gamma curve compensating circuit as claimed in claim 1 , further comprising:

a backlight module control circuit, electrically coupled to the multiplexer and controlling a backlight module driving signal for driving a backlight module of the display system according to the grey-scale luminance of the original display signal outputted from the multiplexer.

3. The gamma curve compensating circuit as claimed in claim 1 , wherein the grey-scale insertion determining circuit comprises:

a color space transforming module, transforming the input image signal received by the display system into a color space distributing data;

an analyzing module, electrically coupled to the color space transforming module for receiving the color space distributing data, and analyzing distribution of the color space distributing data to output a corresponding analyzing signal;

a grey-scale insertion limiting module, storing a grey-scale limiting parameter and limiting a varying range of the grey-scale luminance of two adjacent divisions; and

a grey-scale generating module, electrically coupled to the analyzing module and the grey-scale insertion limiting module, determining the grey-scale luminance of the grey-scale image to be inserted according to the analyzing signal and the grey-scale limiting parameter, and outputting the grey-scale image.

4. The gamma curve compensating circuit as claimed in claim 1 , wherein the display system comprises a liquid crystal display.

5. A display system comprising:

a power supply, providing electric power to the display system for operating;

an image receiving terminal, receiving an input image signal;

a gamma curve compensating circuit comprising:

an image generating circuit, generating an original output image signal according to the input image signal;

a grey-scale insertion determining circuit, determining a plurality of grey-scale luminance of a grey-scale image to be inserted according to the input image signal and outputting the grey-scale image;

a multiplexer, having a first input terminal electrically coupled to the grey-scale insertion determining circuit and a second input terminal electrically coupled to the image generating circuit, and the multiplexer being used for selecting one of the grey-scale image and the original output image signal as an original display signal; and

a looking up and compensating circuit, electrically coupled to the multiplexer for receiving the original display signal, the looking up and compensating circuit providing a plurality of look-up tables, selecting a specific look-up table from the look-up tables according to the grey-scale luminance of the grey-scale image, and performing gamma-curve compensation on the original display signal based on the specific look-up table to generate a gamma compensating result; and

a display screen, displaying the gamma compensating result;

wherein the grey-scale image comprises a plurality of divisions, each one of the divisions corresponds to one of the plurality of grey-scale luminance, and the grey-scale luminance of each one of the divisions is determined according to the grey-scale luminance of another adjacent division of the plurality of divisions.

6. The display system as claimed in claim 5 , further comprising:

a backlight module, providing backlight for the display screen.

7. The display system as claimed in claim 6 , further comprising:

a backlight module control circuit, electrically coupled to the multiplexer and controlling a backlight module driving signal for driving a backlight module according to the grey-scale luminance of the grey-scale image outputted from the multiplexer.

8. The display system as claimed in claim 5 , wherein the grey-scale insertion determining circuit comprises:

a color space transforming module, transforming the input image signal received by the display system into a color space distributing data;

an analyzing module, electrically coupled to the color space transforming module for receiving the color space distributing data, and analyzing distribution of the color space distributing data to output a corresponding analyzing signal;

a grey-scale insertion limiting module, storing a grey-scale limiting parameter and limiting a varying range of the grey-scale luminance of two adjacent divisions; and

a grey-scale generating module, electrically coupled to the analyzing module and the grey-scale insertion limiting module, determining the grey-scale luminance of the grey-scale image to be inserted according to the analyzing signal and the grey-scale limiting parameter, and outputting the determined grey-scale image.

9. A gamma curve compensating method, comprising:

selecting a plurality of grey-scales according to a grey-scale limiting parameter and an analyzing signal generated by an input image signal, and generating grey-scale images according to the generated grey-scales;

providing a plurality of look-up tables for the plurality of grey-scales;

selecting a plurality of specific grey-scales from the plurality of grey-scales of an inserted grey-scale image;

generating an original display signal according to the inserted grey-scale image and an original output image generated by the input image;

selecting, from the plurality of look-up tables, a specific look-up table corresponding to the specific grey-scale;

performing a gamma-curve compensation based on the specific look-up table to keep a gamma curve of a related display system invariable in a displaying process; and adjusting a light source of the display system to keep a luminance of the display system invariable in the displaying process;

wherein the grey-scale image comprises a plurality of divisions, each one of the divisions corresponds to one of the plurality of grey-scale luminance, and the grey-scale luminance of each one of the divisions is determined according to the grey-scale luminance of another adjacent division of the plurality of divisions.

10. The gamma curve compensating method as claimed in claim 9 , further comprising:

turning off the light source of the display system in a certain period of time in the displaying process.

11. The gamma curve compensating method as claimed in claim 9 , wherein the analyzing signal is to denote a pre-inserting grey-scale determined by a histogram analyzing method, a minimum grey insertion method or a threshold method.

12. The gamma curve compensating method as claimed in claim 9 , wherein the grey-scale limiting parameter is used to limit a varying range of the grey-scale luminance of two adjacent divisions.

13. The gamma curve compensating method as claimed in claim 9 , wherein the luminance of the display system is adjusted by a pulse width modulation signal, and the pulse width modulation signal with a wider pulse width is used to map upward a grey-scale luminance curve of the grey-scale image with a lower inserted grey-scale.

14. The gamma curve compensating method as claimed in claim 9 , wherein each of the plurality of gray-scale images depends on a division as a unit, and each division is a line of image with a same grey-scale.