Abstract:
This invention discloses a display apparatus capable of adjusting gamma and brightness based on ambient light and its display adjustment method. The display apparatus is adjusted to display an image output signal based on an image input signal and the correlated color temperature and brightness of an ambient light. The display apparatus includes a plurality of light sensing circuits, a memory unit, an image processing module, and a display module. The light sensing circuit senses the ambient light to produce a digital ambient color temperature index value. The memory unit stores a lookup table of brightness expression rates and gamma adjustment parameters corresponding to different color temperature index values. The image processing module produces a gamma adjustment parameter by a lookup table based on the color temperature index value and generates the gamma expression rate of the image input signal. The image processing module adjusts the image input signal to generate the image output signal based on the gamma adjustment parameter. The display module displays the image output signal.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a display apparatus of adjusting gamma and brightness and its display adjustment method, and more particularly to a display apparatus that employs an ambient light sensor having color and brightness detection functions and gamma and brightness adjustment method thereof. 
         [0003]    2. Description of the Related Art 
         [0004]    Referring to  FIG. 1  for a schematic diagram illustrates a conventional display apparatus capable of adjusting a backlight brightness, the display apparatus  100  includes a light sensing circuit  110 , an analog-to-digital converter  115 , an image processing module  120 , a digital-to-analog converter  125 , a memory unit  130 , a backlight module  140  and a display module  145 . 
         [0005]    The light sensing circuit  110  is provided for sensing an ambient light level to generate an ambient light signal SA, and the analog-to-digital converter  115  converts the analog ambient light signal SA into a digital ambient light signal SDA. The memory unit  130  is provided for storing a lookup table  135 , and the lookup table  135  provides a plurality of brightness expression rates and a plurality of backlight adjustment parameters corresponding to different digital ambient light signals SDA. The image processing module  120  receives the digital ambient light signal SDA and an image input signal  101 , and the image processing module  120  has an image format conversion function for converting the image input signal  101  into an image output signal  102 , and the image output signal  102  can be displayed on a display module  145 . The image processing module  120  also has a backlight brightness control function, and the lookup table  135  stored in the memory unit  130  provides a digital backlight adjustment parameter based on the digital ambient light signal SDA and the brightness expression rate required by the desired displaying screen, and the digital-to-analog converter  125  converts a digital backlight adjustment parameter into an analog backlight adjustment parameter, and the backlight module  140  adjusts the backlight brightness based on the analog backlight adjustment parameter. In the aforementioned conventional display apparatus, the backlight module  140  can only adjust the backlight brightness based on the brightness of the ambient light. 
         [0006]    However, the foregoing conventional display apparatus just provides an automatic adjustment mechanism for backlight brightness, but not an automatic adjustment mechanism for gamma and brightness or backlight color temperature contrast. Since the ambient color temperature tends to be a warm color in an illumination environment of incandescent light bulbs, therefore the displayed color should be adjusted to a cold color or higher color temperature value to enhance the image contrast between the environment and the displaying screen. In some applications like the web camera, the gamma correction factors and the white balance point of the image is corrected based on the ambient light color temperature information. For example, in an illumination environment of fluorescent light bulbs or in a dark rainy environment, the ambient light color temperature tends to be a cold color, and thus the gamma correction factors of red, green and blue color space (R, G, B) should be adjusted to a warmer color to improve the image contrast between the environment and the displaying screen. Further, the screen display should be adjusted to high color temperature contrast and high brightness for an outdoor environment in order to achieve a vivid image viewing level. In other words, the conventional display apparatus cannot adjust both gamma and brightness automatically based on different ambient lighting environments. In view of the foregoing shortcomings of the prior art, the proposed color display system is to provide a display apparatus with an ambient light sensor having color and brightness detection functions and its display adjustment method, thereby overcoming the shortcomings of the prior art. 
       SUMMARY OF THE INVENTION 
       [0007]    It is a primary objective of the present invention to provide a display apparatus with an ambient light sensor having color and brightness detection functions and its display adjustment method for adjusting gamma and brightness. A gamma expression rate and a brightness contrast expression rate of an input image are generated to provide an output image with enhanced the color contrast. 
         [0008]    To achieve the foregoing objective, the present invention provides a display apparatus for receiving and displaying an image input signal, and the display apparatus comprises a red light sensing circuit, a green light sensing circuit, a blue light sensing circuit, a memory unit, an image processing module, and a display module. 
         [0009]    The red light sensing circuit is provided for sensing a red light brightness of the ambient light to generate a red light brightness signal, and the green light sensing circuit is provided for sensing a green light brightness of the ambient light to generate a green light brightness signal, and the blue light sensing circuit is provided for sensing a blue light brightness of the ambient light to generate a blue light brightness signal. The memory unit is provided for storing a lookup table, and the lookup table provides a plurality of gamma coefficient and a plurality of gamma adjustment parameters corresponding to different ambient light correlated color temperature conditions. The change of the RGB gamma affects the input image and enhances the image contrast of the display and the ambient light condition. The image processing module is provided for receiving an image input signal from the any image sources such as a web camera, a TV, a digital camera or a digital picture frame, and coupled to the red light sensing circuit, the green light sensing circuit and the blue light sensing circuit so as to receive the red light brightness signal, the green light brightness signal and the blue light brightness signal respectively. The image processing module executes a numeric operation of the red light brightness signal, the green light brightness signal and the blue light brightness signal to generate an ambient color temperature index value (CCT ambient ). The image processing module is further coupled to the memory unit and uses the lookup tables to process the image input signal. The image processing module obtains the gamma adjustment parameters from the lookup table based on the ambient color temperature index (CCT ambient ) value and generate the gamma correction expression rate of the image input signal. The image processing module adjusts the gamma correction expression rate of the image input signal based on the gamma adjustment parameters to generate the image output signal. The display module is coupled to the image processing module to display the image output signal. 
         [0010]    The present invention further provides a gamma and brightness adjustment method for adjusting a display apparatus to display an image output signal based on an image input signal and correlated color temperature and brightness value of an ambient light, and the gamma and brightness adjustment method comprises: setting a lookup table to provide a lookup table of a plurality of gamma correction adjustment parameters corresponding to different ambient color temperature index value (CCT ambient ) values, sensing an ambient light correlated color temperature value, executing a signal analysis of the image input signal based on gamma correction adjustment parameters from the lookup table, and using the gamma correction adjustment parameters to adjust the gamma correction expression rate of the image input signal to generate the image output signal. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  shows a conventional display apparatus capable of adjusting backlight brightness; 
           [0012]      FIG. 2  is a schematic block diagram of a display apparatus having a color and brightness detection function in accordance with a first preferred embodiment of the present invention; 
           [0013]      FIG. 3  is a schematic block diagram of a display apparatus having a color and brightness detection function in accordance with a second preferred embodiment of the present invention; 
           [0014]      FIG. 4  is a schematic block diagram of a display apparatus having a color and brightness detection functions in accordance with a third preferred embodiment of the present invention; and 
           [0015]      FIG. 5  is a flow chart of a gamma correction and brightness adjustment method applied to a display apparatus in accordance with the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0016]    To make it easier for our examiner to understand the technical characteristics and performance of the present invention, we use preferred embodiments together with the attached drawings for the detailed description of the invention. However, these preferred embodiments are provided for the illustration of the present invention only, and not intended to limit the scope of the invention. 
         [0017]    Referring to  FIG. 2  for a schematic block diagram of a display apparatus having color and brightness detection functions in accordance with a first embodiment of the present invention, the display apparatus  200  comprises a color and brightness sensing circuit  210 , an analog-to-digital converter  215 , an image processing module  220 , a digital-to-analog converter  225 , a memory unit  230 , a backlight module  240  and a display module  245 . 
         [0018]    The color and brightness sensing circuit  210  is provided for sensing the color and brightness of an ambient light to produce an ambient color and brightness signal SAc, and the analog-to-digital converter  215  converts the analog ambient color and brightness signal SAc into a digital color and brightness signal SDAc. The memory unit  230  is provided for storing a first lookup table  235  and a second lookup table  236 . The first lookup table  235  provides a lookup table of a plurality of brightness expression rates and a plurality of backlight brightness adjustment parameters corresponding to the component of the brightness value of different digital digital color and brightness signals SDAc. The second lookup table  236  provides a lookup table of a plurality of gamma adjustment parameters corresponding to the ambient light of different digital color and brightness signal SDAc. The image processing module  220  receives the digital color and brightness signal SDAc and an image input signal  201 , and the image processing module  220  has image format conversion function for converting the image input signal  201  into an image output signal  202 , and the image output signal  202  can be displayed on the display module  245 . 
         [0019]    The image processing module  220  has backlight brightness control function and gamma adjustment functions. From a first lookup table  235 , a digital backlight brightness adjustment parameter Sdb is obtained based on the component of the brightness value of the digital color and brightness signal SDAc and the brightness expression rate required by the image input signal  201 . The image processing module  220  then executes a signal process to produce the digital backlight adjustment parameter Sdb based on the component of the brightness value of the digital color and brightness signal SDAc and the brightness expression rate of the image input signal  201  together with the data in the first lookup table  235 , and the digital-to-analog converter  225  converts the digital backlight brightness adjustment parameter Sdb into an analog backlight adjustment parameter Sb, and the backlight module  240  adjusts the backlight brightness based on the analog backlight adjustment parameter Sb. In addition, the image processing module  220  can execute a signal process to produce the ambient color temperature index values based on the component of the color value of the digital color and brightness signal SDAc. The image processing module  220  obtains gamma adjustment parameters from the second lookup table  236 , based on the ambient color temperature index value and generates the gamma expression rate required by the image output signal  202 . The image processing module  220  then adjusts the gamma correction expression rate of the image input signal  201  to generate the image output signal  202  based on the digital gamma adjustment parameter. 
         [0020]    Please referring to  FIG. 3  for a schematic block diagram of a display apparatus having color and brightness detection functions in accordance with a second embodiment of the present invention, the display apparatus  300  comprises a color and brightness sensing circuit  310 , a plurality of analog-to-digital converters  315 ,  316  and  317 , an image processing module  320 , a digital-to-analog converter  325 , a memory unit  330 , a backlight module  340  and a display module  345 . 
         [0021]    The color and brightness sensing circuit  310  comprises a red light sensing circuit  311 , a green light sensing circuit  312  and a blue light sensing circuit  313 . The red light sensing circuit  311  is provided for sensing a red light brightness of an ambient light to generate a red light brightness signal SAr, and the green light sensing circuit  312  senses a green light brightness of an ambient light to generate a green light brightness signal SAg, and a blue light sensing circuit  313  is provided for sensing a blue light brightness of an ambient light to generate a blue light brightness signal SAb. The analog-to-digital converter  315  converts an analog red light brightness signal SAr into a digital red light brightness signal SDAr, and the analog-to-digital converter  316  converts a green light brightness signal Sag into a digital green light brightness signal SDAg, and the analog-to-digital converter  317  converts an analog blue light brightness signal SAb into a digital blue light brightness signal SDAb. 
         [0022]    The image processing module  320  receives the digital red light brightness signal SDAr, the digital green light brightness signal SDAg, the digital blue light brightness signal SDAb and an image input signal  301 . The image processing module  320  has image format conversion function for converting the image input signal  301  into an image output signal  302 , so that the image output signal  302  can be displayed on the display module  345 . The image processing module  320  comprises a brightness processing unit  321  and a gamma processing unit  322 , and the brightness processing unit  321  executes a numeric operation of the digital red light brightness signal SDAr, the digital green light brightness signal SDAg and the digital blue light brightness signal SDAb to produce a digital brightness value, and the gamma processing unit  322  executes a numeric operation of the digital red light brightness signal SDAr, the digital green light brightness signal SDAg and the digital blue light brightness signal SDAb to produce a digital color temperature index value. 
         [0023]    The memory unit  330  is provided for storing a first lookup table  335 , a second lookup table  336  and a third lookup table  337 . The first lookup table  335  provides a lookup table of a plurality of brightness expression rates and a plurality of backlight brightness adjustment parameters corresponding to different digital brightness values. The second lookup table  336  provides a lookup table of a plurality of gamma correction adjustment parameters corresponding to different digital color temperature index values. The third lookup table  337  provides a lookup table of a plurality of contrast expression rates and a plurality of contrast adjustment parameters corresponding to different digital brightness values. 
         [0024]    The image processing module  320  has backlight brightness control function, gamma adjustment function and contrast adjustment function, such that a digital backlight brightness adjustment parameter Sdb can be obtained from the first lookup table  335  based on the digital brightness value and the brightness expression rate required by the image input signal  301 , wherein the image processing module  320  executes a signal process to produce the digital backlight brightness adjustment parameter Sdb based on the digital brightness value and the brightness expression rate required by the image input signal  301  together with the data of the first lookup table  335 , and the digital-to-analog converter  325  converts the digital backlight adjustment parameter Sdb into an analog backlight adjustment parameter Sb, and the backlight module  340  adjusts a backlight brightness based on the analog backlight adjustment parameter Sb. 
         [0025]    Further, the image processing module  320  uses the second lookup table  336  to obtain a digital gamma correction adjustment parameter based on the digital ambient color temperature index value. The image processing module  320  executes a signal process to produce the digital gamma correction express rate based on the digital gamma correction adjustment parameter required by the image input signal  301  together with the data of the second lookup table  336 , and the image processing module  320  adjusts the gamma correction expression rate of the image input signal  301  to generate the image output signal  302 . For example, in a preferred embodiment of the signal process, the following formula is used for calculating the digital gamma correction adjustment parameter: 
         [0000]        CCT   ambient =( SDAr −param — 1× SDAb )/ SDAg    
         [0026]    where CCT ambient  is the estimated Ambient Color temperature index of the ambient light. 
         [0027]    Digital gamma correction adjustment parameter=param — 2+param — 3×CCT ambient  Preferably, the param — 2 is an offset parameter, and the param — 3 is a gain parameter. The param — 1, param — 2 and param — 3 can be stored second lookup table  336 . 
         [0028]    In addition, the image processing module  320  uses the third lookup table  337  to obtain a digital contrast adjustment parameter based on the digital brightness value and the contrast expression rate required by the image input signal  301 . The image processing module  320  then executes a signal process to produce the digital contrast adjustment parameter based on the digital brightness value and the contrast expression rate required by the image input signal  301  together with the data of the third lookup table  337 , and the image processing module  320  adjusts the contrast expression rate of the image input signal  301  to generate the image output signal  302  based on the digital contrast adjustment parameter. 
         [0029]    Please referring to  FIG. 4  for a schematic block diagram of a display apparatus having gamma and brightness detection functions in accordance with a third embodiment of the present invention, the display apparatus  400  comprises a color and brightness sensing circuit  410 , a plurality of analog-to-digital converters  415 ,  416  and  417 , an image processing module  420 , a pulse width modulation (PWM) generation circuit  425 , a memory unit  430 , a backlight module  440 , a display module  445 , a brightness distribution processing circuit  490  and a plurality of duty cycle modulation units  426 ,  427 ,  428 ,  429 . The pulse width modulation generation circuit  425  produces a pulse width modulation signal Spwm to be inputted to the plurality of duty cycle modulation units  426 ,  427 ,  428 ,  429 . 
         [0030]    The color and brightness sensing circuit  410  comprises a red light sensing circuit  411 , a green light sensing circuit  412 , a blue light sensing circuit  413  and a radiometric reference sensing module  414 . The red light sensing circuit  411  is provided for sensing a red light brightness of an ambient light to generate a red light brightness signal SAr, and the green light sensing circuit  412  is provided for sensing a green light brightness of an ambient light to generate a green light brightness signal SAg, and the blue light sensing circuit  413  is provided for sensing a blue light brightness of an ambient light to generate a blue light brightness signal SAb. The radiometric reference sensing module  414  is provided for sensing the radiometric reference of the display module  445  at different positions and different directions to generate a plurality of signals. The brightness distribution processing circuit  490  generates a digital distribution signal SDD based on the brightness signals, and the digital distribution signal SDD is used for displaying the uneven ambient light distribution situation of an ambient light on the display module  445 . For example, if the digital distribution signal SDD is a 4-bit digital signal, then 0000 represents an even distribution situation, and 0001 represents a distribution of an ambient light concentrated at the upper left corner, 0010 represents a distribution of an ambient light concentrated at the upper right corner, 0100 represents a distribution of an ambient light concentrated at the lower left corner, and 1000 represents a distribution of an ambient light concentrated at the lower right corner, and so forth. 
         [0031]    The analog-to-digital converter  415  converts the analog red light brightness signal SAr into a digital red light brightness signal SDAr, and the analog-to-digital converter  416  converts a green light brightness signal SAg into a digital green light brightness signal SDAg, and the analog-to-digital converter  417  converts an analog blue light brightness signal SAb into a digital blue light brightness signal SDAb. 
         [0032]    The image processing module  420  receives the digital red light brightness signal SDAr, the digital green light brightness signal SDAg, the digital blue light brightness signal SDAb, the digital distribution signal SDD and an image input signal  401 . The image processing module  420  has image format conversion function for converting the image input signal  401  into an image output signal  402 , so that the image output signal  402  can be displayed on the display module  445 . The image processing module  420  comprises a brightness processing unit  421  and a gamma correction processing unit  422 , and the brightness processing unit  421  executes a numeric operation of the digital red light brightness signal SDAr, the digital green light brightness signal SDAg and the digital blue light brightness signal SDAb to produce a digital brightness value, and the gamma correction processing unit  422  executes a numeric operation of the digital red light brightness signal SDAr, the digital green light brightness signal SDAg and the digital blue light brightness signal SDAb to produce a digital color temperature index value. 
         [0033]    The memory unit  430  is provided for storing a first lookup table  435 , a second lookup table  436  and a third lookup table  437 . The first lookup table  435  provides a lookup table of a plurality of brightness expression rates and a plurality of backlight adjustment parameters corresponding to different digital brightness values. The second lookup table  436  provides a lookup table of a plurality of gamma correction adjustment parameters corresponding to different digital color temperature index values. The third lookup table  437  provides a lookup table of a plurality of contrast expression rates and a plurality of contrast adjustment parameters corresponding to different digital brightness values. 
         [0034]    The image processing module  420  has backlight brightness distribution control function, the gamma adjustment function and contrast adjustment function, and uses the first lookup table  435  to obtain an original digital backlight brightness adjustment parameter based on the digital brightness value and the brightness expression rate required by the image output signal  402 , and the image processing module  420  produce a plurality of digital backlight adjustment parameters Sdb 6 , Sdb 7 , Sdb 8 , Sdb 9  based on the original digital backlight adjustment parameter together with the digital distribution signal SDD. The plurality of digital backlight brightness adjustment parameter Sdb 6 , Sdb 7 , Sdb 8 , Sdb 9  are inputted to a plurality of duty cycle modulation units  426 ,  427 ,  428   429  respectively. The plurality of duty cycle modulation units  426 ,  427 ,  428 ,  429  are used to adjust the duty cycle of the pulse width modulation signal Spwm to generate a plurality of backlight brightness driving signals Sb 6 , Sb 7 , Sb 8 , Sb 9  based on the plurality of digital backlight adjustment parameters Sdb 6 , Sdb 7 , Sdb 8 , Sdb 9  respectively. The plurality of backlight brightness driving signals Sb 6 , Sb 7 , Sb 8 , Sb 9  are used to drive the backlight module  440  to produce the required backlight brightness distribution. 
         [0035]    Further, the image processing module  420  uses the second lookup table  436  to obtain a digital gamma correction adjustment parameter based on the digital color temperature index value and generates the gamma correction expression rate required by the image input signal  401 , and the image processing module  420  adjusts the gamma correction expression rate of the image input signal  401  to generate the image output signal  402  based on the digital gamma correction adjustment parameter. In addition, the image processing module  420  uses the third lookup table  437  to obtain a digital contrast adjustment parameter based on the digital brightness value and the contrast expression rate required by the image input signal  401 , and the image processing module  420  adjusts the contrast expression rate of the image input signal  401  to generate the image output signal  402  based on the digital contrast adjustment parameter. 
         [0036]    Referring to  FIG. 5  for a flow chart of a gamma and brightness adjustment method used in a display apparatus in accordance with the present invention, the gamma and brightness adjustment method adjusts the backlight brightness and distribution, the gamma correction expression rate of an image, and the contrast expression rate of an image of the display apparatus to display an image signal based on the brightness, ambient correlated color temperature, and uneven ambient light distribution information of an environment, and the gamma and brightness adjustment method comprises the following steps: 
         [0037]    Step S 501 : Set a first lookup table to provide a lookup table of a plurality of brightness expression rates and a plurality of backlight brightness adjustment parameters corresponding to different digital brightness values. 
         [0038]    Step S 502 : Set a second lookup table to provide a lookup table of a plurality of gamma correction adjustment parameters corresponding to different digital color temperature index values. 
         [0039]    Step S 503 : Set a third lookup table to provide a lookup table of a plurality of contrast expression rates and a plurality of contrast adjustment parameters corresponding to different digital brightness values. 
         [0040]    Step S 504 : Sense a brightness value, an ambient correlated temperature value, and an uneven ambient light distribution value of the environment. 
         [0041]    Step S 505 : Execute a signal analysis of the brightness value and the ambient color temperature value to produce a digital brightness value and a digital color temperature value respectively; 
         [0042]    Step S 506 : Execute a signal analysis of the ambient light distribution value to generate a digital distribution signal. 
         [0043]    Step S 507 : Execute a signal analysis of an image signal to produce a brightness expression rate, a gamma correction expression rate and a contrast expression rate. 
         [0044]    Step S 508 : Obtain an original digital backlight adjustment parameter from a first lookup table based on the digital brightness value and the brightness expression rate required by the image signal. 
         [0045]    Step S 509 : Obtain a digital gamma correction adjustment parameter from a second lookup table based on the digital ambient color temperature value and generate the gamma correction expression rate required by the image signal. 
         [0046]    Step S 510 : Obtain a digital contrast adjustment parameter from a third lookup table based on the digital brightness value and the contrast expression rate required by the image signal. 
         [0047]    Step S 511 : Integrate the original digital backlight adjustment parameter and the digital distribution signal to generate a plurality of backlight brightness driving signals. 
         [0048]    Step S 512 : Use the plurality of backlight brightness driving signals to produce a required backlight brightness distribution, and use the digital gamma correction adjustment parameter and the digital contrast adjustment parameter to adjust the gamma correction expression rate and contrast expression rate of the image signal. In Step S 508 , an original digital backlight adjustment parameter obtained from a first lookup table based on the digital brightness value and the brightness expression rate of the image signal can be generated from the digital brightness value and the brightness expression rate of an image signal together with the data of the first lookup table to execute a signal process to produce the original digital backlight adjustment parameter. In Step S 509 , a digital gamma correction adjustment parameter obtained from a second lookup table based on the digital color temperature index value and generates the gamma correction expression rate of an image signal. In Step S 510 , a digital contrast adjustment parameter obtained from a third lookup table based on the digital brightness value and the contrast expression rate of an image signal can be generated from the digital brightness value and the contrast expression rate of the image signal together with the data of the third lookup table to execute a signal process to produce the digital contrast adjustment parameter. 
         [0049]    In summation of the description above, when the display apparatus having color and brightness detection functions in accordance with the present invention executes display function, the backlight brightness and distribution, and the gamma correction expression rate and the contrast expression rate of an image can be used to adjust the display apparatus based on the brightness, ambient correlated color temperature and uneven ambient light distribution in order to provide a display with vivid video or digital image for viewing. 
         [0050]    While the invention has been described by way of examples and in terms of preferred embodiments, it is to be understood that the invention is not limited thereto. To the contrary, it is intended to cover various modifications and similar arrangements and procedures, and the scope of the appended claims therefore should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements and procedures.