Patent Publication Number: US-2010117927-A1

Title: Dual-Display Computer

Description:
PRIORITY CLAIM 
     The present application claims benefit of priority under 35 U.S.C. §§120, 365 to the previously filed Japanese Patent Application No. JP2008-290939 entitled, “Dual Display Computer” with a priority date of Nov. 13, 2008, which is incorporated by reference herein. 
     BACKGROUND 
     1. Technical Field 
     The present invention relates to portable computers in general, and in particular to a portable computer equipped with two displays. 
     2. Description of Related Art 
     A notebook personal computer (notebook PC) has excellent portability because of its light weight and small size. A notebook PC is also able to realize functions equivalent to a desktop computer via a function extending apparatus such as a docking station or a port replicator. 
     Since a notebook PC is equipped with only one display, in order to use two or more displays, it is necessary to connect an external display thereto via a function extending apparatus or connect the external display to an external terminal. When the user works with many windows concurrently opened on one display, the user may have to resize the various overlapping windows in order to view all the windows at once. 
     SUMMARY 
     In order to improve work efficiency, it would be desirable for a notebook PC display to distribute and display the various windows on multiple displays. In addition, since the display luminance of the notebook PC is adjustable by a user according to the place of use, it would be desirable to be able to adjust the luminance with a simple manipulation when multiple displays are mounted on the notebook PC. 
     In accordance with a preferred embodiment, a notebook PC includes a to primary display and a secondary display. The notebook PC also includes a step value storage device for storing a set of manipulation step values for simultaneously controlling the luminance of the primary and secondary displays. The notebook PC further includes a first luminance table and a second luminance table. The first luminance table stores a set of first control step values that corresponds to a luminance value to be set to the primary display for each of the manipulation step values. The second luminance table stores a set of second control step values that corresponds to a luminance value to be set to the secondary display for each of the manipulation step values so that the luminance values set for the secondary display becomes substantially identical to the luminance values set for the primary display within a range of a predetermined number of consecutive manipulation step values. 
     All features and advantages of the present invention will become apparent in the following detailed written description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention itself, as well as a preferred mode of use, further objects, and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein: 
         FIGS. 1A and 1B  are perspective views of an outer appearance of a notebook PC in accordance with a preferred embodiment; 
         FIG. 2  is a block diagram of a notebook PC, in accordance with a preferred embodiment; 
         FIG. 3  is a block diagram illustrating the connection between a graphic processing unit mounted on a graphics card and a primary display as well as a secondary display; 
         FIG. 4  is a block diagram illustrating the configuration of the software and hardware components mounted on the notebook PC from  FIG. 2 , for performing a luminance adjustment; 
         FIG. 5A and 5B  are views for describing the data structure of a luminance table; 
         FIGS. 6A and 6B  are graphs illustrating the relationship between the manipulation step values and the luminance values of the luminance table as a luminance curve; and 
         FIG. 7  is a high-level logic flow diagram of a method for simultaneously controlling the luminance values of the primary display and the secondary display of the notebook computer from  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
     Referring now to the drawings and in particular to  FIGS. 1A to 1D , there are depicted the outer appearances of a notebook PC  10  in accordance with a preferred embodiment. The notebook PC  10  includes a display casing  11  and a system casing  13 . The display casing  11  is coupled to the system casing  13  via a hinge. The notebook PC  10  also includes a primary display  15  and a secondary display  21 , both being integrated within the display casing  11 .  FIG. 1A  illustrates a state where only the primary display  15  is being used, and  FIG. 1B  illustrates a state where the secondary display  21  is exposed, and both the primary display  15  and the secondary display  21  are being used simultaneously. 
     The display casing  11  accommodates therein the primary display  15  so that a displaying surface faces the front side when the display casing  11  is opened from the system casing  13 , and at the same time, the secondary display  21  is drawably accommodated on a backside. When the secondary display  21  is needed, the secondary display  21  can be drawn out of the display casing  11 , and the displaying surface of the secondary display  21  is set to face the same direction as the primary display  15 . The system casing  13  accommodates therein various types of functional devices. A keyboard  17  and a pointing device  19  are mounted on the system casing  13 . 
       FIG. 2  is a block diagram of the notebook PC  10 . A computer processing unit (CPU)  51  is an arithmetic processing device performing the central function of the notebook PC  10 , which includes the execution of an operating system (OS), various device drivers and various application programs. The CPU  51  is connected to a memory controller hub (MCH)  53 . The MCH  53  is a device that processes high-speed data transfer within the notebook PC  10 . The MCH  52  has a memory controller for controlling an operation of accessing a main memory  55 , a data buffer for absorbing a difference in a data transfer rate between the CPU  51  and other devices. The MCH  51  is equipped with a PCI Express x16 port for connecting a graphics card  57  thereto. 
     The main memory  55  is a volatile random access memory (RAM) that is used as a read area of programs executed by the CPU  51  and a work area to which processed data are written. The graphics card  57  is connected to the MCH  53  and is provided with a graphic processing unit (GPU), a video BIOS, and a video memory (VRAM), and is configured to receive a drawing command from the CPU  51  to produce images of image files and write the images in the VRAM and to output images read out of the VRAM at predetermined timing to the primary display  15  and the secondary display  21 . The GPU is a special processor exclusively for writing images to the VRAM in accordance with the drawing command received from the CPU  51  and is also referred to as a graphics accelerator. The graphics card  57  is connected to the primary display  15  and a protocol converter  59 . The protocol converter  59  is connected to the secondary display  21 . 
       FIG. 3  is a block diagram illustrating the connection between a GPU  71  mounted on the graphics card  57  and the primary display  15  along with the secondary display  21 . The GPU  71  is capable of outputting image data of two systems: one of a primary system associated to the primary display  15 ; and the other of a secondary system associated to the secondary display  21 . The GPU  71  receives, from the CPU  51 , a first control step value for controlling the luminance of the primary display  15 , and a second control step value for controlling the luminance of the secondary display  21 . The detailed description of the control step values will be described below. The primary system is configured to output an image signal compliant with the low voltage differential signaling (LVDS) format and a PWM signal for controlling a backlight  111  to the primary display  15 . The duty ratio of the PWM signal corresponds to the first control step value. The secondary system is configured to output an image signal compliant with the digital visual interface (DVI) format. However, for the present embodiment, the format of the image signal output by the GPU  71  is not limited to LVDS or DVI. 
     The protocol converter  59  is configured to convert the image signal compliant with the DVI format received from the GPU  71  into an image signal compliant with the LVDS format and output the converted image signal to the secondary display  21 . The GPU  71  is also configured to transfer the second control step value received from the CPU  51  to the protocol converter  59  via a DDC channel, which is a portion of a DVI signal line. The protocol converter  59  is configured to generate a PWM signal having a duty ratio that corresponds to the second control step value and to output the PWM signal to the secondary display  21 , thereby controlling the backlight  211 . 
     The primary display  15  and the secondary display  21  have substantially the same structure; i.e., they are configured to include liquid crystal panels  107  and  207 , backlights  111  and  211 , data line-driving circuits  105  and  205 , a scanning line-driving circuits  103  and  203 , liquid crystal panel control circuits  101  and  201 , and backlight control circuits  109  and  209 , respectively. The liquid crystal panels  107  and  207  employ an active matrix mode, in which each cell of a liquid crystal array constituting each pixel includes a thin film transistor (TFT), a pixel capacitor, and a storage capacitor. 
     The backlight  111  is a side-edge type backlight that uses a cold cathode fluorescent lamp (CCFL) as a light source, and the backlight  211  is a side-edge type backlight that uses a light-emitting diode (LED) as a light source. The side-edge type backlight can make a liquid crystal display thinner than a direct-type backlight, and the secondary display  21  can achieve a much thinner display because it uses LEDs as a light source. The backlight control circuit  109  is configured to control a voltage applied to the backlight  111 , with the duty ratio of the PWM signal received from the GPU  71 , so as to control the luminance of the liquid crystal panel  107 . The backlight control circuit  209  is configured to control a current applied to the backlight  211 , with the duty ratio of the PWM signal received from the protocol converter  59 , so as to control the luminance of the liquid crystal panel  207 . The GPU  71  and the protocol converter  59  are configured to set a duty ratio of 0 to 100% in order to correspond to the 256 values of the first or second control step values. 
     The liquid crystal panel control circuits  101  and  201  are configured to receive, from the GPU  71 , image data of red, green, and blue for displaying images on the liquid crystal panels  107  and  207 , respectively, to generate and output image data that are serial by the time axis to the data line-driving circuits  105  and  205  and the scanning line-driving circuits  103  and  203 , respectively. The data line-driving circuits  105  and  205  and the scanning line-driving circuits  103  and  203  are configured to perform a line-sequential scanning of the TFTs of the liquid crystal array every one-frame period to sequentially write serial image data to pixel capacitors, thereby displaying two-dimensional images on the liquid crystal panels  107  and  207 , respectively. 
     Referring back to  FIG. 2 , an I/O controller hub (ICH)  61  is connected to the MCH  53  in order to process a data transfer to/from peripheral input/output devices. The ICH  61  is provided with ports for a Universal Serial Bus (USB), a serial ATA (AT Attachment), a Serial Peripheral Interface (SPI) bus, a Peripheral Component Interconnect (PCI) bus, a PCI-Express bus, a Low Pin Count (LPC), and the like, and is connected to devices corresponding thereto. In  FIG. 2 , only an HDD  63  connected to a serial ATA port of the ICH  61  is illustrated, and other devices are not illustrated. 
     The ICH  61  is also connected via an LPC bus  65  to legacy devices, which in the past have been used in notebook PCs  10 , or devices which do not require high-speed data transfer. In  FIG. 2 , only an embedded controller (EC)  67  and a flash ROM  69  are illustrated as the devices connected to the LPC bus  65 . The EC  67  is a microcomputer configured by an 8- to 16-bit CPU, a ROM, a RAM, and the like, and is further provided with an multi-channel A/D input terminal, a multi-channel D/A output terminal, a timer, and a digital input/output terminal. The EC  67  controls the electric power supplied to the devices mounted on the notebook PC  10 . The EC  67  mounts thereon a keyboard controller function and is connected to the keyboard  17  and the pointing device  19 . 
     The flash ROM  69  is a non-volatile memory in which the stored contents are electrically rewritable, and which stores therein a device driver for controlling the input/output device, a system BIOS for managing power, the temperature of the system casing  13 , or the like, so as to comply with the Advanced Configuration and Power Interface (ACPI) specifications, a Power-On Self Test (POST) for performing tests or initialization of hardware components during activation of the notebook PC  10 , and the like. 
       FIG. 4  is a block diagram illustrating the configuration of the software and hardware components mounted on the notebook PC  10 , for performing a luminance adjustment in accordance with a preferred embodiment. A utility program  301  is an application program that runs on the OS  308 , and performs processing related to the adjustment of the luminance of the displays. The utility program  301  includes a luminance table  303  for the primary display  15 , a luminance table  305  for the secondary display  21 , and a control step storage portion  307 . The luminance tables  303  and  305  may be combined in one table. The control step storage portion  307  stores therein  16  manipulation step values, from  0  to  15 , for controlling the luminance of the primary display  15  and the secondary display  21 . 
     A user is able to select one of the manipulation step values by sequentially increasing or decreasing them through keyboard manipulations while visually checking the results of selecting operations on the display. In the present embodiment, a user selects the manipulation step value by manipulating a special key on the keyboard  17 , thereby being able to simultaneously control the luminance of the primary display  15  and the secondary display  21  by one step each time. The special key may be configured by a combination of Fn key and Home key, which can be simultaneously depressed to achieve a luminance increase, along with a combination of Fn key and End key, which can be simultaneously depressed to achieve a luminance decrease. Whatever the special key on the keyboard  17  is depressed once, the present manipulation step value of the control step storage portion  307  is increased or decreased by one step. A keyboard driver  309  is configured to set the parameters to the keyboard controller of the EC  67  or transfer a scan code to the CPU  51 . 
     A video driver  311  is configured to set the parameters to the graphics card  57  or transfer the drawing command from the CPU  51  to the GPU  71 . 
       FIGS. 5A and 5B  are views for describing the data structures of the luminance tables  303  and  305 .  FIGS. 6A and 6B  are graphs illustrating the relationship between the manipulation step values and the luminance values of the luminance tables  303  and  305  as a luminance curve. The luminance tables  303  and  305  are mapping tables that correlate (map) the manipulation step values and the control step values with each other. In other words, the luminance tables  303  and  305  can be said to map the manipulation step values into luminance values via the control step values. The luminance tables  303  and  305  store therein the first control step values and the second control step values corresponding to 16 manipulation step values from 0 to 15, respectively. The first control step values and the second control step values are constructed by  256  control information data from 0 to 255, respectively. The first control step values are control information data that determine the duty ratio of the PWM signal supplied to the backlight control circuit  109  and correspond to the luminance of the liquid crystal panel  107 . The second control step values are the control information data that determine the duty ratio of the PWM signal supplied to the backlight control circuit  209  and correspond to the luminance of the liquid crystal panel  207 . 
     The backlight  111  and the backlight  211  control the luminance of the liquid crystal panels  107  and  207  based on the duty ratio of the voltage or current corresponding to the PWM signal output from the backlight control circuits  109  and  209 , respectively. The luminance of the liquid crystal panels  107  and  207  becomes 0 when the duty ratio of the backlight control circuits  109  and  209  is 0%, and, when the duty ratio is 100%, the luminance becomes the maximum that is determined based on the performance of the backlights  111  and  211 . In the luminance tables  303  and  305 , the first control step value is set to  14  and the second control step value is set to  22  so that the respective displays have the minimum luminance where the respective displays can display images with a predetermined luminance even when the manipulation step value is set to the minimum, namely 0. Moreover, in the luminance tables  303  and  305 , the first control step value and the second control step value are set such that, when the manipulation step value is set to the maximum, namely 15, the respective displays have the maximum luminance under the 100% duty ratio of the PWM signal. 
     The line  401  in  FIG. 6A  represents a luminance curve of the primary display  15 , formed by luminance values corresponding to respective manipulation step values when the manipulation step values from 0 to 15 and the first control step values from 0 to 255 were evenly mapped. Moreover, the line  405  represents a luminance curve of the secondary display  21 , formed by luminance values corresponding to respective manipulation step values when the manipulation step values of 0 to 15 and the second control step values of 0 to 255 were evenly mapped. When the manipulation step values and the control step values were evenly mapped, the luminance values of both the primary display  15  and the secondary display  21  increase substantially linearly with an increase in the manipulation step value. In other words, since the control step value is proportional to the duty ratio of the PWM signal, it can be said that the luminance values are also proportional to the duty ratio. However, in the present embodiment, when the luminance tables  303  and  305  are generated, the luminance values corresponding to the respective manipulation step values are determined in advance and the control step values are set so as to correspond to the luminance values. Therefore, it is not necessary that the duty ratio of the PWM signal and the luminance values are proportional to each other or in a specific relation. 
     The line  403  represent a luminance curve of the primary display  15  that is based on the first control step values corresponding to the respective manipulation step values. In the case of the line  403 , the luminance values are increasing exponentially with an increase in the manipulation step value. The shape of the line  403  is determined such that a change in luminance with a change of one step value, detected by the user becomes as even as possible from an ergonomic perspective based on the relationship between the change in luminance detected by the user and the absolute value of the luminance or such that the luminance for each step is determined or optimized from the viewpoint of a balance between the luminance and the power consumption. 
     In  FIG. 6B , the line  407  is a luminance curve of the secondary display  21  which is based on the second control step values corresponding to the respective manipulation step values. In the present embodiment, in place of the line  405 , the line  407  is employed as the luminance curve of the secondary display  21 . In the example of  FIG. 6B , the maximum luminance value  409  of the line  403  is  400 , and the maximum luminance value  411  of the line  407  is  230 . The first control step values corresponding to the luminance values of the line  403  are stored in the luminance table  303 , and the second control step values corresponding to the luminance values of the line  407  are stored in the luminance table  305 . The second control step values are set so that the luminance value of the primary display  15  and the luminance value of the secondary display  21  are as identical as possible within a range of consecutive manipulation step values. Although the luminance values corresponding to the control step values are stored in the luminance tables  303  and  305 , it is not always necessary to store these luminance values since they are not used for controlling the luminance. 
     The relationship between the manipulation step value and the control step value will be described by the luminance curve. In the present embodiment, the second control step values are set so that the luminance curve  403  and the luminance curve  407  are as identical as possible within a range of consecutive manipulation step values. The maximum luminance value  411  of the secondary display  21  at the maximum manipulation step value  15  is smaller than the maximum luminance value  409  of the primary display  15 . Therefore, the second control step values are set so that the luminance curve  407  becomes identical to the luminance curve  403  until the manipulation step value of  13  representing the intermediate luminance value which is substantially the intermediate value of the luminance in the line  403 , and the second control step value is also set so that the luminance curve  407  becomes identical to the line  405  at the manipulation step values of 14 and 15. 
     In  FIGS. 6A and 6B , although the luminance values of the lines  403  and  407  are slightly different within the range of manipulation step values 0 to 13, this difference is small enough to be compared with the quantization error of the control step value when the manipulation step values and the control step values are mapped. Moreover, the difference falls within such a range that the different luminance values are perceived equal by the sensibility of the user. The luminance values of the primary display  15  and the secondary display  21  can be made identical to each other over the entire range of the manipulation step values if the maximum luminance value  409  of the line  403  is identical to the maximum luminance value  411  of the line  405 . Since the primary display  15  and the secondary display  21  mounted on the notebook PC  10  have different purposes of use, the secondary display  21  is typically configured with the smaller maximum luminance value. In this case, therefore, the second control step values are set so that the line  405  of the secondary display  21  becomes identical to the line  403  of the primary display  15  within as wide a range as possible of the manipulation step values. This is because, as described above, the line  403  is set to have the optimum shape from the ergonomic and power-saving perspectives. 
     When the maximum luminance value of the secondary display  21  is larger than the maximum luminance value of the primary display  15 , it is possible to make the luminance value of the secondary display  21  identical to the luminance value of the primary display  15  over the entire range of the manipulation step values. When the maximum luminance value  411  of the line  405  is smaller than the maximum luminance value  409  of the line  403  as in  FIGS. 6A and 6B , both luminance values can be made identical to each other until the luminance value of the line  403  at a certain manipulation step value (in this case, the manipulation step value of  14 ) exceeds the maximum luminance value  411  of the line  405 . 
     Referring now to  FIG. 7 , there is illustrated a high-level logic flow diagram of a method for simultaneously controlling the luminance values of the primary display  15  and the secondary display  21  via the manipulation of a special key. In block  501 , in the luminance table  303  and the luminance table  305 , the first control step values and the second control step values, corresponding to the luminance values of the line  403  from  FIG. 6A  and the line  407  from  FIG. 6B , are stored in advance so as to correspond to the manipulation step values of 0 to 15, respectively. Moreover, the previous manipulation step value immediately before the notebook PC  10  is powered off was held in the control step storage portion  307 . 
     When the notebook PC  10  is started in block  503 , the software illustrated in  FIG. 4  is loaded into the main memory  55  from the HDD  63 . In block  505 , the utility program  301  refers to the luminance tables  303  and  305  and the present manipulation step value stored in the control step storage portion  307  to acquire the first control step value of the primary display  15  and the second control step value of the secondary display  21  corresponding to the present manipulation step value, respectively. 
     The utility program  301  sets the first control step value and the second control step value to the GPU  71  through intervention of the OS  308  and the video driver  311 . The GPU  71  generates a PWM signal of a duty ratio corresponding to the first control step value to control the output voltage of the backlight control circuit  109 . The backlight  111  performs lighting with a luminance corresponding to the duty ratio of the PWM signal under the control of the backlight control circuit  109 . Moreover, the GPU  71  sets the second control step value of the secondary display  21  to the protocol converter  59  using the DDC channel of the DVI signal. The protocol converter  59  generates a PWM signal of the duty ratio corresponding to the second control step value to control the output current of the backlight control circuit  209 . The backlight  211  performs lighting with a luminance corresponding to the duty ratio of the PWM signal under the control of the backlight control circuit  209 . 
     In block  507 , when a user presses the special key on the keyboard  17 , corresponding scan codes are generated by the EC  67  and the keyboard driver  309  interrupts the CPU  51  to transfer the scan codes. In block  509 , the CPU  51  analyzes the scan codes and executes the utility program  301 , whereby the manipulation step value stored in the control step storage portion  307  is increased or decreased by one step each time by an amount corresponding to the number of key depressions. In block  511 , whenever the present manipulation step value stored in the control step storage portion  307  is selected, the utility program  301  refers to the luminance tables  303  and  305  to acquire and transfer to the GPU  71 , the first control step value and the second control step value corresponding to the newly selected manipulation step value. When the notebook PC  10  is powered off in block  513 , since the state of the control step storage portion  307  immediately before powering-off is stored in the HDD  63 , at the next powering-on time, the display will initially display with a luminance based on the stored manipulation step value. 
     Thereafter, by the same procedures as shown in block  505 , the backlight  111  and the backlight  211  will perform lighting with the luminance corresponding to the changed manipulation step value. Here, when the present manipulation step value is changed, the utility program  301  may display the present step value after a change in the primary display  15 . In accordance with the present embodiment, it is possible to simultaneously control the luminance of the primary display  15  and the secondary display  21  by a common key manipulation, and the luminance values of both displays are substantially identical to each other in a predetermined range of the luminance curves  403  and  407 . 
     Although the notebook PC of the present embodiment is able to simultaneously control two displays by a common key manipulation, according to the results of a sample test conducted to estimate the luminance of mass-produced notebook 
     PCs, the respective displays showed variations in their initial luminance and different rates of decrease in the luminance with time. Therefore, verification needs to be made as to whether the typical values of the first control step value and the second control step value, which are set to the primary display  15  and the secondary display  21 , respectively, are commonly applicable to all the mass-produced notebook PCs. The notebook PC provides a different display luminance when the luminance is sensed by the user within the range of viewing angles. In accordance with the present embodiment, it was confirmed that no particular discomfort was caused because the difference in the luminance of the two displays is small enough to be allowable within the range of viewing angles even when the luminance values are simultaneously controlled by a common manipulation, and because the difference falls within the range of variations of the luminance when the display was used to its usable limit life. 
     As has been described, the present invention provides a portable computer having a primary display and a secondary display, and a method for simultaneously controlling the luminance values of the primary display and the secondary display of the portable computer. 
     It is also important to note that although the present invention has been described in the context of a computer system, those skilled in the art will appreciate that the method of the present invention is capable of being distributed as a computer program product via a computer readable medium such as a compact disc. 
     While the invention has been particularly shown and described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.