1. A method of performing gamma correction for LCD panels, comprising: Step A 1 : dividing the display area of a LCD panel to form n sub-areas of the display area, where n is a positive integer equivalent to or larger than 2; Step A 2 : dividing all grey-scale images into n sets to form n sets of grey-scale images, where each set of grey-scale images, comprising a plurality of grey-scale images, corresponds to one specific sub-area; Step A 3 : displaying a first chosen grey-scale image of each set of grey-scale images on the corresponding sub-area of n sub-areas concurrently, where the first chosen grey-scale image is any one of the grey-scale images in the set of grey-scale images; Step A 4 : detecting the brightness of the first chosen grey-scale image with a photosensor installed on the sub-area; Step A 5 : examining if there is grey-scale image pending for detection in the set of grey scale images, wherein the image pending for detection was not the first chosen grey-scale image; if there is grey-scale image pending for detection, then replace the first chosen grey-scale image with the grey-scale image pending for detection in the set of grey-scale images, and continue with step A 3 ; if there is no grey-scale image pending for detection, then continue with step A 6 ; Step A 6 : extracting a gamma curve of the LCD panel based on the grey scale and brightness of the first chosen grey-scale images; and Step A 7 : correcting the gamma curve of the LCD panel based on a pre-defined gamma curve; wherein the step A 3 comprises: displaying the first chosen grey-scale image of the set of grey-scale images from images at the highest grey scale level to the lowest grey scale level, or from images at the lowest grey scale level to the highest grey scale level on the corresponding sub-area; and the step A 4 comprises: Step A 41 : installing a photosensor in the middle of the sub-area and sticking the light-receiving surface of the photosensor on the sub-area; Step A 42 : detecting an analog signal of the brightness of the first chosen grey-scale image with the photosensor; and Step A 43 : converting the analog signal of the brightness of the first chosen grey-scale image into a digital signal of the brightness of the first chosen grey-scale image.