Liquid crystal display device, image displaying method thereof, and backlight control device for local dimming

An image displaying method of a liquid crystal display device, wherein the liquid crystal display device comprises a backlight module, a backlight control device, and a liquid crystal display panel, the backlight control device is disposed between the backlight module and the liquid crystal display panel, and the method comprises following steps:

• the backlight module outputting a first optical signal;
• the backlight control device receiving an image signal and the first optical signal, dividing an image into a plurality of pixel units (j, i), analyzing pixel information of the pixel units (j, i) to correspondingly output a plurality of dimming coefficients, and adjusting the first optical signal according to the dimming coefficients to output a plurality of second optical signals;
• and
• the liquid crystal display panel receiving the second optical signals to display the image corresponding to the image signal;
• wherein each of the pixel units (j, i) comprises at least one pixel, each of the pixel units (j, i) corresponds to each of the dimming coefficients, j represents a row where the pixel unit (j, i) is located, and i represents a column where the pixel unit (j, i) is located,
• wherein the backlight control device comprises a processor and a plurality of backlight control units, the processor receives the image signal, divides the image into the plurality of pixel units (j, i), and analyzes the pixel information of the pixel units (j, i) to correspondingly output the plurality of dimming coefficients, and each of the backlight control units adjusts the first optical signal according to each of the dimming coefficients to correspondingly output each of the second optical signals, and
• wherein the processor comprises a first dimming coefficient output unit used to receive the image signal, to divide the image into the plurality of pixel units (j, i), to calculate a maximum grayscale value Ymax and an average brightness value Yav of each of the pixel units (j, i), and then to calculate a first dimming coefficient L(j, i) corresponding to each of the pixel units (j, i) according to a following formula (1):
• L(i,i)=(1−α)×Yav+αYmax (1),
• wherein α is a weighting coefficient, when a value of Ymax is less than or equal to a first threshold, α is 0;
• when the value of Ymax is greater than or equal to a second threshold, α is 1;
• and when the value of Ymax is greater than the first threshold and less than the second threshold, α=kYmax, wherein k is a constant greater than 0;
• and
• the first dimming coefficient L(j, i) is the dimming coefficient corresponding to each of the pixel units (j, i).

A backlight control device, used to receive an image signal and a first optical signal, to divide an image into a plurality of pixel units (j, i), to analyze pixel information of the pixel units (j, i) to correspondingly output a plurality of dimming coefficients, and to adjust the first optical signal according to the dimming coefficients to output a plurality of second optical signals;

• wherein each of the pixel units (j, i) comprises at least one pixel, each of the pixel units (j, i) corresponds to each of the dimming coefficients, j represents a row where the pixel unit (j, i) is located, and i represents a column where the pixel unit (j, i) is located,
• wherein the backlight control device comprises a processor and a plurality of backlight control units, wherein the processor is used to receive the image signal, to divide the image into the plurality of pixel units (j, i), and to analyze the pixel information of the pixel units (j, i) to correspondingly output the plurality of dimming coefficients, and each of the backlight control units is used to adjust the first optical signal according to each of the dimming coefficients to correspondingly output each of the second optical signals, and
• wherein the processor comprises a first dimming coefficient output unit used to receive the image signal, to divide the image into the plurality of pixel units (j, i), to calculate a maximum grayscale value Ymax and an average brightness value Yav of each of the pixel units (j, i), and then to calculate a first dimming coefficient L(j, i) corresponding to each of the pixel units (j, i) according to a following formula (1):
• L(j,i)=(1−α)×Yav+αYmax (1),
• wherein α is a weighting coefficient, when a value of Ymax is less than or equal to a first threshold, α is 0;
• when the value of Ymax is greater than or equal to a second threshold, α is 1;
• and when the value of Ymax is greater than the first threshold and less than the second threshold, α=kYmax, wherein k is a constant greater than 0;
• and
• the first dimming coefficient L(j, i) is the dimming coefficient corresponding to each of the pixel units (j, i).