Abstract:
In a handheld computing device that includes a backlit display having a variable-intensity backlight, a method for controlling the intensity of light produced by the backlight involves the following steps. The computing device also includes user data input means, and data processing means coupled to the user data input means and the backlit display. The data processing means includes at least one software application that is configured to display information on the display. The method involves the steps of (1) setting the intensity to a first intensity level and activating one of the software applications; and (2) setting the intensity to a minimum intensity level, less than the first intensity level, after expiry of a predetermined elapsed time of non-activity from the user data input means. The predetermined elapsed time is based on the activated software application.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This patent application is a continuation of U.S. patent application Ser. No. 10/858,060, entitled “Backlight Control For a Handheld Computing Device”, filed Jun. 2, 2004 now U.S. Pat. No. 7,144,136. 
    
    
     FIELD OF THE INVENTION 
     The invention described herein relates to a mechanism for enhancing the ease of use of a handheld computing device. In particular, the invention described herein relates to a method and system for enhancing the clarity of information presented on a backlit display of a handheld computing device. 
     BACKGROUND OF THE INVENTION 
     The conventional handheld computing device, such as a PDA, or a wireless telephone, includes a LCD display for presenting information to the user, and a keyboard or keypad for facilitating data entry by the user. Typically, the LCD display comprises a transmissive LCD panel, and a backlight for enhancing the visibility of the information presented on the LCD panel. The intensity of the light produced by the LCD backlight is set by the manufacturer such that the information presented on the LCD panel is clear at moderate ambient light levels. However, this factory setting often renders the LCD panel difficult to read in dim light (because the backlight is too bright) and strong ambient light (because the backlight is too dim). 
     In some implementations, instead of a transmissive LCD panel, the LCD display comprises a transreflective LCD panel, and a backlight for enhancing the visibility of the information presented on the LCD panel. Due to the reflective nature of the LCD panel, the clarity of the information presented on the LCD panel is clearest in strong ambient light. Further, the intensity of the light produced by the LCD backlight is set by the manufacturer such that the information presented on the LCD panel is clear at moderate ambient light levels. However, this factory setting often renders the LCD panel difficult to read in dim ambient light (because the backlight is too bright). 
     SUMMARY OF THE INVENTION 
     According to the invention described herein, in a handheld computing device that includes a variable-intensity backlight, the intensity of light produced by the backlight is based on the activity of the user of the handheld computing device. 
     According to a first aspect of the invention, in a handheld computing device that includes a backlit display having a variable-intensity backlight, there is provided a method for controlling an intensity of light produced by the backlight. The computing device also includes user data input means, and data processing means coupled to the user data input means and the backlit display. The data processing means includes at least one software application that is configured to display information on the display. The method involves (1) setting the intensity to a first intensity level and activating one of the software applications; and (2) then setting the intensity to a minimum intensity level, less than the first intensity level, after expiry of a predetermined elapsed time of non-activity from the user data input means. The predetermined elapsed time is based on the activated software application. 
     According to a second aspect of the invention described herein, there is provided a handheld computing device that includes user data input means, a backlit display having a variable-intensity backlight, and data processing means coupled to the user data input means and the backlit display. The data processing means includes at least one software application that is configured to display information on the display. The data processing means is configured to perform the steps of (1) activating one of the software applications and setting the intensity to a first intensity level; and (2) setting the intensity to a minimum intensity level, less than the first intensity level, after expiry of a predetermined elapsed time of non-activity from the user data input means. The predetermined elapsed time is based on the activated software application. 
     According to a third aspect of the invention described herein, there is provided a computer-readable medium that includes computer processing instructions for a handheld computing device. The handheld computing device includes user data input means, a backlit display having a variable-intensity backlight, and data processing means coupled to the user data input means and the backlit display. The data processing means includes at least one software application that is configured to display information on the display. The computer processing instructions, when executed by the data processing means, causes the handheld computing device to perform the steps of (1) activating one of the software applications and setting the intensity to a first intensity level; and (2) setting the intensity to a minimum intensity level, less than the first intensity level, after expiry of a predetermined elapsed time of non-activity from the user data input means. The predetermined elapsed time is based on the activated software application. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be described, by way of example only, with reference to the accompanying drawings, in which: 
         FIG. 1  is a front plan view of a handheld computing device, according the invention described herein; 
         FIG. 2  is a schematic view depicting the communication pathways existing between the data processing means, the LCD display, the function key and the data input means of the handheld computing device depicted in  FIG. 1 ; 
         FIG. 3  is a schematic view depicting functional details of the handheld computing device 
         FIG. 4  is a flowchart depicting, by way of overview, the method of backlight control implemented in the handheld computing device; and 
         FIGS. 5   a  and  5   b  together comprise a flowchart depicting, in detail, the method of backlight control implemented in the handheld computing device. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to  FIG. 1 , there is shown a handheld computing device, denoted generally as  100 , provided according to one aspect of the invention. The handheld computing device  100  includes a display  122 , a function key  146 , and data processing means  102  (not shown) disposed within a common housing. The display  122  comprises a backlit display having a variable-intensity backlight. 
     In one embodiment, the backlit display  122  comprises a transmissive LCD display, and the function key  146  operates as a power on/off switch. Alternately, in another embodiment, the backlit display  122  comprises a reflective or trans-reflective LCD display, and the function key  146  operates as a backlight switch. 
     As shown in  FIG. 2 , the data processing means  102  of the handheld computing device  100  is in communication with the display  122  and the function key  146 . As will be described, the data processing means comprises a microprocessor  138 , and a memory  124 ,  126  (disposed within the housing). The memory  124 ,  126  carries computer processing instructions which, when accessed from the memory  124 ,  126  and executed by the microprocessor  138 , cause the data processing means to perform the method which will be described in further detail below. 
     In addition to the display  122  and the function key  146 , the handheld computing device  100  includes user data input means for inputting data to the data processing means. Further, the data processing means  102  is in communication with the user data input means. As shown in  FIG. 1 , preferably the user data input means includes a keyboard  132 , a thumbwheel  148  and an escape key  160 . Preferably, the keyboard  132  comprises a backlit keyboard. Further, preferably the backlight for the keyboard  132  is operable independently of the backlight for the display  122 . 
     Typically, the handheld computing device  100  is a two-way wireless communication device having at least voice and data communication capabilities. Further, preferably the handheld computing device  100  has the capability to communicate with other computer systems on the Internet. Depending on the exact functionality provided, the wireless handheld computing device  100  may be referred to as a data messaging device, a two-way pager, a wireless e-mail device, a cellular telephone with data messaging capabilities, a wireless Internet appliance, or a data communication device, as examples. 
       FIG. 3  depicts functional details of the handheld computing device  100 . Where the handheld computing device  100  is enabled for two-way communication, it will incorporate a communication subsystem  111 , including both a receiver  112  and a transmitter  114 , as well as associated components such as one or more, preferably embedded or internal, antenna elements  116  and  118 , local oscillators (LOs)  113 , and a processing module such as a digital signal processor (DSP)  120 . As will be apparent to those skilled in the field of communications, the particular design of the communication subsystem  111  will be dependent upon the communication network in which the device is intended to operate. For example, the handheld computing device  100  may include a communication subsystem  111  designed to operate within the Mobitex™ mobile communication system, the DataTAC™ mobile communication system, GPRS network, UMTS network, EDGE network or CDMA network. 
     Network access requirements will also vary depending upon the type of network  119 . For example, in the Mobitex and DataTAC networks, the handheld computing device  100  is registered on the network using a unique identification number associated with each handheld computing device. In UMTS and GPRS networks, and in some CDMA networks, however, network access is associated with a subscriber or user of the handheld computing device  100 . A GPRS handheld computing device therefore requires a subscriber identity module (SIM) card in order to operate on a GPRS network, and a RUIM in order to operate on some CDMA networks. Without a valid SIM/RUIM card, a GPRS/UMTS/CDMA handheld computing device may not be fully functional. Local or non-network communication functions, as well as legally required functions (if any) such as “911” emergency calling, may be available, but the handheld computing device  100  will be unable to carry out any other functions involving communications over the network. The SIM/RUIM interface  144  is normally similar to a card-slot into which a SIM/RUIM card can be inserted and ejected like a diskette or PCMCIA card. The SIM/RUIM card can have approximately 64K of memory and hold many key configuration  151 , and other information  153  such as identification, and subscriber related information. 
     When required network registration or activation methods have been completed, the handheld computing device  100  may send and receive communication signals over the network  119 . Signals received by antenna  116  through communication network  119  are input to receiver  112 , which may perform such common receiver functions as signal amplification, frequency down conversion, filtering, channel selection and the like, and in the example system shown in  FIG. 3 , analog to digital (A/D) conversion. A/D conversion of a received signal allows more complex communication functions such as demodulation and decoding to be performed in the DSP  120 . In a similar manner, signals to be transmitted are processed, including modulation and encoding for example, by DSP  120  and input to transmitter  114  for digital to analog conversion, frequency up conversion, filtering, amplification and transmission over the communication network  119  via antenna  118 . DSP  120  not only processes communication signals, but also provides for receiver and transmitter control. For example, the gains applied to communication signals in receiver  112  and transmitter  114  may be adaptively controlled through automatic gain control algorithms implemented in DSP  120 . 
     The handheld computing device  100  preferably includes a microprocessor  138  which controls the overall operation of the device. Communication functions, including at least data and voice communications, are performed through communication subsystem  111 . Microprocessor  138  also interacts with further device subsystems such as the display  122 , flash memory  124 , random access memory (RAM)  126 , auxiliary input/output (I/O) subsystems  128 , serial port  130 , keyboard  132 , speaker  134 , microphone  136 , a short-range communications subsystem  140  and any other device subsystems generally designated as  142 . 
     Some of the subsystems shown in  FIG. 3  perform communication-related functions, whereas other subsystems may provide “resident” or on-device functions. Notably, some subsystems, such as keyboard  132  and display  122 , for example, may be used for both communication-related functions, such as entering a text message for transmission over a communication network, and device-resident functions such as a calculator or task list. 
     Operating system software used by the microprocessor  138  is preferably stored in a persistent store such as flash memory  124 , which may instead be a read-only memory (ROM) or similar storage element (not shown). Those skilled in the art will appreciate that the operating system, specific device applications, or parts thereof, may be temporarily loaded into a volatile memory such as RAM  126 . The operating system software comprises computer processing instructions which, when accessed from the flash memory  124  and the RAM  126  and executed by the microprocessor  138 , define the aforementioned data processing means  102 . Received communication signals may also be stored in RAM  126 . 
     As shown, the flash memory  124  can be segregated into different areas for both computer programs  158  and program data storage  150 ,  152 ,  154  and  156 . These different storage types indicate that each program can allocate a portion of flash memory  124  for their own data storage requirements. Microprocessor  138 , in addition to its operating system functions, preferably enables execution of software applications on the handheld computing device. A predetermined set of applications that control basic operations, including at least data and voice communication applications for example, will normally be installed on the handheld computing device  100  during manufacturing. A preferred software application may be a personal information manager (PIM) application having the ability to organize and manage data items relating to the user of the handheld computing device such as, but not limited to, e-mail, calendar events, voice mails, appointments, and task items. Naturally, one or more memory stores would be available on the handheld computing device to facilitate storage of PIM data items. Such PIM application would preferably have the ability to send and receive data items, via the wireless network  119 . In a preferred embodiment, the PIM data items are seamlessly integrated, synchronized and updated, via the wireless network  119 , with the user&#39;s corresponding data items stored or associated with a host computer system. Further applications may also be loaded onto the handheld computing device  100  through the network  119 , an auxiliary I/O subsystem  128 , serial port  130 , short-range communications subsystem  140  or any other suitable subsystem  142 , and installed by a user in the RAM  126  or preferably a non-volatile store (not shown) for execution by the microprocessor  138 . Such flexibility in application installation increases the functionality of the device and may provide enhanced on-device functions, communication-related functions, or both. For example, secure communication applications may enable electronic commerce functions and other such financial transactions to be performed using the handheld computing device  100 . 
     In a data communication mode, a received signal such as a text message or web page download will be processed by the communication subsystem  111  and input to the microprocessor  138 , which preferably further processes the received signal for output to the display  122 , or alternatively to an auxiliary I/O device  128 . A user of the handheld computing device  100  may also compose data items such as email messages for example, using the keyboard  132 , which is preferably a complete alphanumeric keyboard or telephone-type keypad, in conjunction with the display  122  and possibly an auxiliary I/O device  128 . Such composed items may then be transmitted over a communication network through the communication subsystem  111 . 
     For voice communications, overall operation of the handheld computing device  100  is similar, except that received signals would preferably be output to a speaker  134  and signals for transmission would be generated by a microphone  136 . Alternative voice or audio I/O subsystems, such as a voice message recording subsystem, may also be implemented on the handheld computing device  100 . Although voice or audio signal output is preferably accomplished primarily through the speaker  134 , display  122  may also be used to provide an indication of the identity of a calling party, the duration of a voice call, or other voice call related information for example. 
     Serial port  130  in  FIG. 3 , would normally be implemented in a personal digital assistant (PDA)-type handheld computing device for which synchronization with a user&#39;s desktop computer (not shown) may be desirable, but is an optional device component. Such a port  130  would enable a user to set preferences through an external device or software application and would extend the capabilities of the handheld computing device  100  by providing for information or software downloads to the handheld computing device  100  other than through a wireless communication network. The alternate download path may for example be used to load an encryption key onto the device through a direct and thus reliable and trusted connection to thereby enable secure device communication. 
     Other communications subsystems  140 , such as a short-range communications subsystem, is a further optional component which may provide for communication between the handheld computing device  100  and different systems or devices, which need not necessarily be similar devices. For example, the subsystem  140  may include an infrared device and associated circuits and components or a Bluetooth™ communication module to provide for communication with similarly enabled systems and devices. 
       FIG. 4  is a flow chart that depicts, by way of overview, the sequence of steps performed by the data processing means  102  according the invention. Initially, at step  400 , the handheld computing device  100  is in an inactive state, and the backlight is at a minimum/off intensity. 
     When the data processing means  102  exits from the inactive state, at step  402  the data processing means  102  sets the intensity of the backlight to a first intensity level that is sufficient for viewing information on the display under first ambient lighting conditions. Subsequently, if the user of the handheld computing device  100  activates the function key, at step  404  the data processing means  102  sets the intensity of the backlight to a second intensity level that is sufficient for viewing information on the backlit display under second ambient lighting conditions that are different than the first ambient lighting conditions. 
     In one embodiment, the backlit display  122  is a transmissive LCD display, and the function key  146  is a power on/off switch. The backlight is set to a maximum intensity level so as to allow the user to view the information on the backlit display  122  under normal lighting conditions. Typically, the backlight is set to the maximum intensity level when the handheld computing device  100  exits the inactive state. However, if the user is operating the handheld computing device  100  under low light conditions, the user activates the power on/off switch  146 , which causes the backlight to be set to a lower intensity so as to allow the user to view the information on the backlit display  122  under the low light conditions. 
     In another embodiment, the backlit display  122  is a reflective or trans-reflective LCD display, and the function key  146  is a backlight switch. The backlight is set to a low intensity level so as to allow the user to view the information on the backlit display  122  under normal lighting conditions. Typically, the backlight is set to the low intensity level when the handheld computing device  100  exits the inactive state. However, if the user is operating the handheld computing device  100  under low light conditions, the user activates the backlight switch  146 , which causes the backlight to be set to a maximum intensity so as to allow the user to view the information on the backlit display  122  under the low light conditions. 
       FIG. 5  is a flow chart that depicts, in detail, the sequence of steps performed by the data processing means  102 . Initially, at step  500 , the handheld computing device  100  is in an inactive state, such as a sleep state; and the backlight is at a minimum intensity, such as off. 
     If the user of the handheld computing device  100  presses a key on the keyboard  132 , depresses the function key  146 , rotates the thumbwheel  148  or depresses the escape key  160 , at step  502  the data processing means  102  exits the inactive state. Alternately, in one variation, the data processing means  102  exits the inactive state in response to activity occurring on one of the computer programs  158 . For instance, the data processing means  102  may exit the inactive state when an e-mail message or a telephone call is received on the handheld computing device  100 . 
     Then, at step  504 , the data processing means  102  sets the intensity of the backlight to a first intensity level. If the backlit display  122  is a transmissive LCD display, the first intensity level is the maximum backlight intensity. However, if the backlit display  122  is a reflective or trans-reflective LCD display, the first intensity level is an intensity lower than the maximum backlight intensity, but greater than the minimal/off intensity level. Both of these first intensity levels allow the user to view the information on the respective backlit displays  122  under normal lighting conditions. 
     Typically, at step  504 , the data processing means  102  rapidly increases the intensity of the backlight from the minimum/off intensity level to the first intensity level so that the change in intensity appears substantially instantaneous to the user of the handheld computing device. However, in one variation, the data processing means  102  slowly increases the intensity of the backlight from the minimum/off intensity level to the first intensity level. This variation is advantageous since, if the user is operating the handheld computing device  100  in a dim environment, a rapid change in backlight intensity would hurt the user&#39;s eyes. Further, the user of the handheld computing device  100  may interrupt the transition from the minimum/off intensity level to the first intensity level by depressing the function key  146 , thereby setting the intensity of the backlight to the level subsisting at the instant the function key  146  was depressed. 
     While the backlight is set at its first intensity level, at step  506  the data processing means  102  determines whether a maximum predetermined period of time has elapsed during which the data processing means  102  has not detected any further activity from the user (eg. the user has not depressed a key on the keyboard  132 , depressed the function key  146 , rotated the thumbwheel  148  or depressed the escape key  160 ). The maximum predetermined period of time may be fixed, or may be based on activity detected in one of the computer programs  158 . For instance, the data processing means  102  may use one predetermined period if the user is reviewing an e-mail message, but may use a different predetermined period if the user is receiving a telephone call on the handheld computing device  100 . 
     If the data processing means  102  determines at step  506  that the maximum predetermined time period has elapsed without any activity from the user being detected, at step  508  the data input means  102  sets the intensity of the backlight back to the minimum/off intensity level. Typically, at step  508 , the data input means  102  rapidly decreases the intensity of the backlight from the first intensity level back to the minimum/off intensity level so that the change in intensity appears substantially instantaneous to the user of the handheld computing device. However, in one variation, the data processing means  102  slowly decreases the intensity of the backlight from the first intensity level to the minimum/off intensity level. This variation is advantageous since, if the user is reviewing a lengthy message on the handheld computing device  100 , the user is given notification to activate the data input means  102  to maintain the backlight on. 
     If, at step  506 , the data processing means  102  detected user activity within the maximum predetermined time period, at step  510  the data processing means  102  determines whether the user depressed and released the function key  146  within the maximum predetermined time period. If the data processing means  102  determined at step  510  that the user depressed and released the function key  146  within the maximum predetermined time period, at step  512  the data processing means  102  sets the intensity of the backlight to a second intensity level. 
     If the backlit display  122  is a reflective or trans-reflective LCD display, the second intensity level is the maximum backlight intensity. However, if the backlit display  122  is a transmissive LCD display, the second intensity level is an intensity lower than the maximum backlight intensity, but greater than the minimal/off intensity level. Both of these second intensity levels allow the user to view the information on the respective backlit displays  122  under dim lighting conditions. 
     Typically, at step  512 , the data input means  102  rapidly changes the intensity of the backlight from the first intensity level to the second intensity level so that the change in intensity appears substantially instantaneous to the user of the handheld computing device. However, in one variation, the data processing means  102  slowly changes the intensity of the backlight from the first intensity level to the second intensity level. Further, the user of the handheld computing device  100  may interrupt the transition from the first intensity level to the second intensity level by depressing the function key  146 , thereby setting the intensity of the backlight to the level subsisting at the instant the function key  146  was depressed. 
     Alternately, at step  514  the data processing means  102  determines whether the user has depressed/held the function key  146  while rotating the thumbwheel  148  within the maximum predetermined time period. If the data processing means  102  determined at step  514  that the user depressed/held the function key  146  while rotating the thumbwheel  148  within the maximum predetermined time period, at step  516  the data input means  102  sets the intensity of the backlight to an intermediate intensity level that is less than the first intensity level, based on the extent of angular rotation of the thumbwheel  148 . Otherwise, the data processing means  102  maintains the intensity of the backlight at the first intensity level. 
     While the backlight is set at the second intensity level, at step  518  the data processing means  102  determines whether the maximum predetermined time period has elapsed during which the data processing means  102  has not detected any further activity from the user (eg. the user has not depressed a key on the keyboard  132 , depressed the function key  146 , rotated the thumbwheel  148  or depressed the escape key  160 ). As discussed above, the maximum predetermined period of time may be fixed, or may be based on activity detected in one of the computer programs  158 . 
     If the data processing means  102  determines at step  518  that the maximum predetermined time period has elapsed without any further activity from the user being detected, at step  520  the data input means  102  sets the intensity of the backlight back to the minimum/off intensity level. 
     Typically, at step  520 , the data input means  102  rapidly decreases the intensity of the display backlight from the second intensity level back to the minimum/off intensity level so that the change in intensity appears substantially instantaneous to the user of the handheld computing device. However, in one variation, the data processing means  102  slowly decreases the intensity of the backlight from the second intensity level to the minimum/off intensity level as a warning to the user, as discussed above. 
     If, at step  518 , the data processing means  102  detected user activity within the maximum predetermined time period, at step  522  the data processing means  102  determines whether the user depressed and released the function key  146  within the maximum predetermined time period. If the data processing means  102  determined at step  522  that the user depressed and released the function key  146  within the maximum predetermined time period, at step  524  the data input means  102  sets the intensity of the backlight back to the minimum/off intensity level. 
     Alternately, at step  526  the data processing means  102  determines whether the user has depressed/held the function key  146  while rotating the thumbwheel  148  within the maximum predetermined time period. If the data processing means  102  determined at step  526  that the user depressed/held the function key  146  while rotating the thumbwheel  148  within the maximum predetermined time period, at step  528  the data input means  102  sets the intensity of the backlight to an intensity level that is less than the second intensity level, based on the extent of angular rotation of the thumbwheel  148 . 
     Otherwise, the data processing means  102  maintains the intensity of the backlight at the second intensity level. Further, in one variation, if the data processing means  102  determined at this step that the user had depressed a key on the keyboard  132 , preferably the data processing means  102  also turns the backlit keyboard  132  on. 
     The present invention is defined by the claims appended hereto, with the foregoing description being merely illustrative of a preferred embodiment of the invention. Those of ordinary skill may envisage certain modifications to the foregoing embodiments which, although not explicitly discussed herein, do not depart from the scope of the invention, as defined by the appended claims.