Apparatus and method for adjusting brightness via controlling backlight

The invention discloses an apparatus for adjusting an output back light relative to the ith image frame among N image frames of an image sequence inputted to a display system. The apparatus includes an optical sensing module, a memory unit, an image processing module, and a back light module. The optical sensing module is used for sensing a current environmental light. The memory unit is used for storing a look-up table in which a plurality of environmental light values, a plurality of brightness ratios, and a plurality of back light adjusting parameters are recorded. Each of the environmental light values corresponds to the brightness ratios and the back light adjusting parameters, and each of the back light adjusting parameters corresponds to one of the brightness ratios. The image processing module is used for calculating a current brightness ratio relative to the ith image frame and for further determining the back light parameter in accordance with the current environmental light, the current brightness ratio, and the look-up table. The back light module is used for adjusting the output back light in accordance with the back light adjusting parameter.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This present invention relates to an adjusting brightness apparatus and an adjusting brightness method, and more particularly, to an adjusting brightness apparatus and an adjusting brightness method for adjusting the output back light relative to an image sequence inputted to a display system.

2. Description of the Prior Art

The brightness of a liquid crystal display (LCD) is provided by a back light module in general. By controlling the distortion of the liquid crystal, the transmittance of the back light can be changed to determine the image brightness. Currently, LCD displaying is mostly performed via a cold cathode fluorescent lamp (CCFL). When a user watches an image via LCD under a dark environment, his eyes will feel uncomfortable due to the glaring light of the LCD. When watching a dark image via LCD, the contrast of the whole image decreases because the intensity of the back light is constant

In the prior art, there are already some LCDs using a light sensor for sensing the environmental light, so as to adjust the back light according to the change of the environmental light. However, said prior art only adjusts the back light according to the environmental light and not according to the image brightness. When the environmental light is darker, and the image is also dark, the contrast still decreases, thus affecting the effect of the image display.

Accordingly, a scope of the present invention provides an adjusting brightness apparatus and an adjusting brightness method for adjusting the output back light to solve the problem mentioned above.

SUMMARY OF THE INVENTION

A scope of the present invention provides an adjusting brightness apparatus and an adjusting brightness method for adjusting the output back light. The adjusting brightness apparatus adjusts the output back light relative to the image frame according to both the change of the environmental light and the brightness of the image frame. Therefore, the quality of the image is improved.

According to a preferred embodiment of the present invention, an adjusting brightness apparatus adjusts the output back light relative to the ith image frame among N image frames of an image sequence inputted to a display system, wherein N is a natural number, and i is a integer index ranging from 1 to N. The adjusting brightness apparatus includes an optical sensing module, a memory unit, an image processing module, and a back light module.

According to the preferred embodiment, the optical sensing module senses a current environmental light. The memory unit is used for storing a look-up table, in which a plurality of environmental light values, a plurality of brightness ratios, and a plurality of back light adjusting parameters are recorded. Each of the environmental light values corresponding to the brightness ratios and the back light adjusting parameters. Each of the back light adjusting parameters corresponding to one of the brightness ratios. The image processing module receives the current environmental light, calculates a current brightness ratio of the ith image frame, and according to the current environmental light, the current brightness ratio, and the look-up table, determines the back light adjusting parameters corresponding to the current brightness ratio. The back light module receives the back light adjusting parameters corresponding to the current brightness ratio and adjusts the output back light of the ith image frame according to the current brightness ratio.

Accordingly, the adjusting brightness apparatus of the present invention adjusts the output back light relative to the image frame according to both the change of the environmental light and the brightness of the image frame, so as to effectively enhance the contrast when both the environmental light and the image frame are dark. Therefore, the quality of the image is improved.

DETAILED DESCRIPTION OF THE INVENTION

Referring toFIG. 1,FIG. 1is a function block diagram of an adjusting brightness apparatus1according to a preferred embodiment of the invention. According to the preferred embodiment, the adjusting brightness apparatus1adjusts an output back light relative to the ith image frame among N image frames of an image sequence10inputted to a display system (not shown inFIG. 1), wherein N is a natural number, and i is a integer index ranging from 1 to N. The image frames of the image sequence10are in RGB color space.

As shown inFIG. 1, the adjusting brightness apparatus1includes an optical sensing module12, an analog-to-digital converter (A/D converter)14, a memory unit16, an image processing module18, a digital-to-analog converter (D/A converter)20, a back light module22, and a display module24.

According to the preferred embodiment, the optical sensing module12senses a current environmental light. Because the optical sensing module12senses the current environmental light in analog signal, the A/D converter14is used to convert the detected current environmental light from an analog signal to a digital signal.

Referring toFIG. 2,FIG. 2is a portion of a look-up table160inFIG. 1. The memory unit16is used for storing the look-up table160, in which a plurality of environmental light values, EL#, a plurality of brightness ratios, BR#, and a plurality of back light adjusting parameters, P#, are recorded. Each of the environmental light values, EL#, corresponds to a plurality of brightness ratios, BR#, and a plurality of back light adjusting parameters, P#. Each of the back light adjusting parameters, P#, corresponds to one of the brightness ratios, BR#. As shown inFIG. 2, environmental light values, EL1to EL16, are recorded in the look-up table160. Each of the environmental light values, EL1to EL16, corresponds to six of the brightness ratios, BR1to BR6, and six of the back light adjusting parameters, P11to P16, P21to P26, . . . , P161to P166.

The image processing module18receives the current environmental light converted by the A/D converter14. The image processing module18calculates a current brightness ratio of the ith image frame of the image sequence10, and according to the current environmental light, the current brightness ratio, and the look-up table160, the image processing module18determines the back light adjusting parameter corresponding to the current brightness ratio. Because the back light adjusting parameter determined by the image processing module18is a digital signal, the D/A converter20converts the back light adjusting parameter from a digital signal to an analog signal. The back light module22receives the back light adjusting parameter, which is converted by the D/A convert20and is corresponding to the current brightness ratio, and the back light module22adjusts the back light relative to the ith image frame according to the back light adjusting parameter corresponding to the current brightness ratio. Finally, the display module24displays the ith image frame of the image sequence10according to the adjusted output back light.

For example, when the current environmental light sensed by the optical sensing module12is EL2, and the current brightness ratio of the ith image is BR4, the image processing module18determines the back light adjusting parameter P24corresponding to the current brightness ratio BR4according to the current environmental light EL2, the current brightness ratio BR4, and the look-up table160. Then, the back light module22adjusts the output back light relative to the ith image frame according to the back light adjusting parameter P24. Finally, the display module24displays the ith image frame of the image sequence10according to the adjusted output back light. Therefore, the adjusting brightness apparatus1of the present invention adjusts the output back light relative to the image frame according to both the change of the environmental light and the brightness of the image frame, so as to effectively enhance the contrast when both the environmental light and the image frame are dark.

For some display systems, the image frames of the image sequence10will be converted with a gamma conversion26to enhance the image contrast before displayed by the display module24.

ReferringFIG. 3,FIG. 3is a flow chart of the adjusting brightness method according to the preferred embodiment of the present invention. Referring toFIG. 1andFIG. 2together withFIG. 3, the adjusting brightness method is used for adjusting an output back light relative to the ith image frame of an image sequence inputted to a display system. According to the preferred embodiment, the adjusting brightness method of the invention includes the steps of:

step S100: sensing a current environmental light;

step S102: calculating a current brightness ratio of the ith image frame, and determining the back light adjusting parameter corresponding to the current brightness ratio in accordance with the current environmental light, the current brightness ratio, and the look-up table;

step S104: adjusting the output back light relative to the ith image frame in accordance with the back light adjusting parameter corresponding to the current brightness ratio; and

step S106: displaying the ith image frame of the image sequence in accordance with the adjusted output back light.

Comparing with the prior art, the adjusting brightness apparatus of the present invention adjusts the output back light relative to the image frame according to both the change of the environmental light and the brightness of the image frame, so as to effectively enhance the contrast when both the environmental light and the image frame are dark. Therefore, the quality of the image is improved.