Abstract:
A portable terminal device including display means  40  for indicating characters and figures, light-emitting means  31  and  32  for emitting exposing light to be used as backlight of the display means, drive means  21  and  22  for activating the light-emitting means, and control means  11  for controlling the drive means, wherein the light-emitting means emits exposed light rays having at least two wavelengths; the control means controls the drive means according to the content of the information to be transmitted to the user in such a way that the wavelength of the exposing light originating from the light-emitting means are changed, thereby enabling the color of backlight of the display means to be changed according to the content of the information to be transmitted. Since a user can ascertain information by means of backlight color, operations required to read characters and figures indicated on the display means can be simplified. This function produces a great effect particularly in darkness.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a portable terminal device having display means such as a liquid crystal display (LCD), and more particularly, to transmission of various types of information items to a user by utilization of backlight colors of display means. 
     As represented by a portable telephone, recent portable terminal devices have been designed in pursuit of a compact, lightweight, and high-performance portable device. The majority of recent portable telephones employ an LCD module. Further, many of the LCD modules are provided with backlight so that characters or figures indicated on display means can be viewed in darkness, and an LED or EL (electroluminescence) is used as the light source for backlight. 
     As shown in FIG. 7, a conventional portable terminal having a backlight function comprises display means  40  for indicating characters or figures, light-emitting means  30  which serves as the light source for backlight, drive means  20  for actuating the light-emitting means  30 , and control means  10  for controlling the drive means  20 . The light-emitting means  30  comprises a first light-emitting diode  301  and a second light-emitting diode  302 , which emits light of identical wavelength. The drive means  20  comprises a first resistor  201  for limiting an electric current flowing to the first light-emitting diode  301 , a second resistor  202  for limiting the electric current flowing to the second light-emitting diode  302 , and a transistor  300  which applies a drive voltage and shuts off the supply of drive voltage. 
     When the user presses any key of the portable terminal device, the control means  10  is activated, and an electric current is supplied to the first light-emitting diode  301  and the second light-emitting diode  302  of the light-emitting means  30 . The first light-emitting diode  301  and the second light-emitting diode  302  emit light rays  501  and  502  of the same wavelength. As a result, characters or figures indicated on the display means  40  become sharply visible. 
     Some portable devices are configured in such a way that the light-emitting means is activated when the control means  10  detects darkness. 
     However, as the conventional portable terminal device becomes compact and lightweight, the effective area of a display screen of the display means  40  is also reduced, thus limiting the number of characters or the size of figure which can be displayed. As a result, it becomes necessary for the user to perform operations according to complicated procedures in order to obtain required information, or it becomes difficult for the user to see display characters or figures which are reduced in size. These problems make it difficult for children or the aged to use a portable terminal device. 
     SUMMARY OF THE INVENTION 
     The present invention has been conceived to solve the problems in the conventional portable terminal device, and the object of the present invention is to provide a portable terminal device capable of instantaneously transmitting various information items to the user by utilization of backlight of the display means. 
     A portable terminal device according to the present invention is capable of changing the color of backlight of the display means according to the contents of information to be transmitted. 
     To this end, the user can instantaneously ascertain information by means of the color of backlight of the display means without reading characters or figures indicated on the display means. Accordingly, information becomes easily understandable even for children and the aged, thereby enabling correct understanding of information even in darkness. 
     According to a first aspect of the present invention, there is provided a portable terminal device having backlight display means, wherein the color of backlight of the display means can be changed according to the content of information to be transmitted, thereby enabling a user to instantaneously understand the information from the backlight color. 
     According to a second aspect of the present invention, there is provided a portable terminal device including display means for indicating characters and figures, light-emitting means for emitting exposing light to be used as backlight of the display means, drive means for activating the light-emitting means, and control means for controlling the drive means, wherein 
     the light-emitting means emits exposed light rays having at least two wavelengths; 
     the control means controls the drive means according to the content of the information to be transmitted to the user in such a way that the wavelength of the exposing light originating from the light-emitting means is changed, thereby enabling the color of backlight of the display means to be changed according to the content of the information to be transmitted. 
     According to a third aspect of the present invention, the light-emitting means has at least two light-emitting elements which emit light rays of different wavelengths, and the control means controls the drive means to thereby switch on or off a single light-emitting element which emits light of a single wavelength or to thereby cause a plurality of light-emitting elements to simultaneously emit a plurality of light rays of different wavelengths. More specifically, the control means switches on or off a light-emitting element which emits light having a single color or causes a plurality of light-emitting elements to simultaneously emit light, thereby giving out a mixed light ray. As a result, the color of backlight is changed. 
     According to a fourth aspect of the present invention, the portable terminal device further comprises detection means for detecting the voltage level of a drive battery of the portable terminal device and setting means for setting a threshold value for the voltage level of the battery. When the voltage level detected by the detection means reaches the threshold value, the control means controls the drive means, thereby switching the wavelength of the light originating from the light-emitting means. The user can instantaneously ascertain a drop in the voltage level of the drive battery from the change of backlight color of the display means from ordinary color. 
     According to a fifth aspect of the present invention, the portable terminal device further comprises reading means for reading from a received signal a signal for specifying the color of backlight of the display means. On the basis of the signal which is read by the reading means and specifies backlight color, the control means controls the drive means, thereby changing the wavelength of the light originating from the light-emitting means. If a calling party using another portable terminal device originates a call while specifying backlight color, the backlight of the display means of the portable terminal device of the called party assumes the specified color. Therefore, if the user makes a prior arrangement with supposed calling parties regarding designation of backlight color, from the backlight color the called party can realize an incoming call is from a specific calling party. 
     According to a sixth aspect of the present invention, the portable terminal device further comprises 
     reading means for reading from a received signal the phone number of the calling party; 
     storage means for storing at least one phone number; and 
     comparison means for comparing the phone number of the calling party read by the reading means with the phone numbers stored in the storage means. On the basis of the result of the comparison performed by the comparison means, the control means controls the drive means, thereby switching the wavelength of the light originating from the light-emitting means. Upon receipt of an incoming call from the calling party registered in the storage means, the called party can identify the calling party from the color of backlight of the display means. 
     According to a seventh aspect of the present invention, the portable terminal device further comprises 
     measurement means for measuring the electric field level of a received signal; and 
     setting means for setting a threshold value for the electric field. 
     When the electric field level measured by the measurement means reaches the threshold value, the control means controls the drive means, thereby switching the wavelength of the light originating from the light-emitting means. From the color of the backlight of the display means, the user of the portable terminal device becomes aware that he is outside of a normally-receivable range. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram showing the configuration of a portable terminal device according to a first embodiment of the present invention; 
     FIG. 2 is a block diagram showing the configuration of a portable terminal device according to a second embodiment of the present invention; 
     FIG. 3 is a block diagram showing the configuration of a portable terminal device according to a third embodiment of the present invention; 
     FIG. 4 is a block diagram showing the configuration of a portable terminal device according to a fourth embodiment of the present invention; 
     FIG. 5 is a block diagram showing the configuration of a portable terminal device according to a fifth embodiment of the present invention; 
     FIG. 6 is an illustration showing specific operations of the portable terminal device according to the present invention; and 
     FIG. 7 is a block diagram showing the configuration of a conventional portable terminal device. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Preferred embodiments of the present invention will now be described by reference to FIGS. 1 through 6. 
     First Embodiment 
     A portable terminal device according to a first embodiment transmits information by means of the color of backlight of the display means. 
     As shown in FIG. 1, the terminal device comprises display means  40  for indicating characters and figures; first light-emitting means  31  for emitting a light ray  51  of a first wavelength as the backlight of the display means  40 ; second light-emitting means  32  for emitting a light ray  52  of a second wavelength as the backlight of the display means  40 ; first drive means  21  for driving the first light-emitting means  31 ; second drive means  22  for driving the second light-emitting means  32 ; and control means  11  for controlling the first drive means  21  and the second drive means  22 . 
     The first light-emitting means  31  comprises a light-emitting diode  311  for emitting the light ray  51  of the first wavelength, and the second light-emitting means  32  comprises a light-emitting diode  312  for emitting the light ray  52  of the second wavelength. The first drive means  21  comprises a first resistor  211  for limiting an electric current flowing to the light-emitting diode  311  and a first transistor  210  for applying a drive voltage or shutting off the supply of drive voltage. The second drive means  22  comprises a second resistor  221  for limiting an electric current flowing to the light-emitting diode  312  and a second transistor  220  for applying a drive voltage or shutting off the supply of drive voltage. 
     The operation of the portable terminal device will now be described. 
     When the portable terminal device is in a first operation state, the control means  11  activate a first control signal  111 . As a result, the transistor  210  of the first drive means  21  is turned on, and a voltage is applied to the light-emitting diode  311 . The light-emitting diode  311  emits the light ray  51  having the first wavelength. 
     When the portable terminal device is in a second operation state, the control means  11  activates a second control signal  112 . As a result, the transistor  220  of the second drive means  22  is turned on, and a voltage is applied to the light-emitting diode  321 . The light-emitting diode  321  emits the light ray  52  having the second wavelength. 
     When the portable terminal device is in the first operation state., the backlight of the display means  40  assumes light having the first wavelength. When the portable terminal device is in the second operation state, the backlight of the display means  40  assumes light having the second wavelength. Accordingly, the user can instantaneously ascertain the operation status of the portable terminal device from the color of backlight of the display means  40 . 
     Thus, the user of the portable terminal device according to the first embodiment can ascertain the operation status of the portable terminal device from only the color of backlight of the display means  40  without reading characters and figures indicated on the display means  40 . This function produces a great effect, particularly in darkness. 
     Second Embodiment 
     A portable terminal device according to a second embodiment of the present invention reports to the user whether or not the voltage level of the battery can still ensure normal operation, by means of backlight color of the display means. 
     As shown in FIG. 2, the portable terminal device comprises detection means  65  for detecting the voltage level of a drive battery  64  of the portable terminal device; setting means  66  for setting the reference voltage level; and control means  11  for controlling the first drive means  21  and the second drive means  22  on the basis of the result of comparison between the detected voltage level of the battery  64  and the reference voltage level. In other respects, the portable terminal according to the present embodiment is identical in configuration to that according to the first embodiment (shown in FIG.  1 ). 
     The operation of the portable terminal device will now be described. 
     The voltage level of the battery  64  at which normal operation of the portable terminal device is ensured is taken as a first voltage level, and the voltage level of the same at which normal operation of the portable terminal device cannot be ensured is taken as a second voltage level. The setting means  66  sets a first threshold value for transition from the first voltage level to the second voltage level and a second threshold value for transition from the second voltage level to the first voltage level. 
     When the portable terminal device is in use, the control means  11  compares the voltage level of the battery  64  detected by the detection means  65  with the first threshold value set by the setting means  66 . If the voltage level of the battery  64  exceeds the first threshold value, the control means  11  activates the first control signal  111 . At this time, as previously mentioned in connection with the first embodiment, the light-emitting diode  311  emits the light ray  51  having the first wavelength. 
     When the voltage level of the battery  64  is lower than the first threshold value, the control means  11  activates the second control signal  112 . As previously described in connection with the first embodiment, the light-emitting diode  321  emits the light ray  52  having the second wavelength. 
     Accordingly, the user of the portable terminal device can ascertain, from a-change in backlight color, that the voltage level of the battery  64  has dropped to the level at which the portable terminal device cannot ensure normal operation. 
     When the battery  64  of the portable terminal device is recharged, the control means  11  compares the voltage level of the battery  64  detected by the detection means  65  with the second threshold value set by the setting means  66 . If the voltage level of the battery  64  is lower than the second threshold value, the control means  11  activates the second control signal  112 . In contrast, if the voltage level of the battery  64  is higher than the threshold value, the control means  11  activates the first control signal 
     Therefore, the user can ascertain from a change in backlight color that the battery  64  has been recharged to a normal voltage level. 
     As mentioned above, the user of the portable terminal device according to the second embodiment can ascertain the condition of the battery  64  from only the color of backlight of the display means  40  without reading characters and figures indicated on the display means  40 . This function produces a great effect, particularly in darkness. 
     Third Embodiment 
     A portable terminal device according to a third embodiment enables the calling party to specify the color of backlight of the display means of the portable terminal of the called party. 
     As shown in FIG. 3, the portable terminal device comprises receiving means  60  for receiving a signal waveform transmitted from another portable terminal device; reading means  61  for reading, from the received signal, a signal for specifying the color of backlight of the display means  40 ; and the control means  11  for controlling the first drive means  21  or the second drive means  22  on the basis of the result of the reading operation performed by the reading means  61 . In other respects, the portable terminal device according to the third embodiment is identical in configuration with that according to the first embodiment (shown in FIG.  1 ). 
     The operation of the portable terminal device will now be described. 
     When the calling party of another portable terminal device originates a call while specifying a first color designation signal, the reading means  61  reads the first color designation signal from the signal received by the receiving means  60  and sends the thus-read signal to the control means  11 . Upon receipt of the first color designation signal, the control means  11  activates the first control signal  111 . At this time, as previously described in connection with the first embodiment, the light-emitting diode  311  emits the light ray  51  having the first wavelength. 
     When the calling party of another portable terminal device originates a call while specifying a second color designation signal, the reading means  61  reads the second color designation signal from the signal received by the receiving means  60  and sends the thus-read signal to the control means  11 . Upon receipt of the second color designation signal, the control means  11  activates the second control signal  112 . At this time, as previously described in connection with the first embodiment, the light-emitting diode  312  emits the light ray  52  having the, second wavelength. 
     As mentioned above, the portable terminal device according to the third embodiment enables the calling party to specify the color of backlight of the display device  40  which indicates an incoming call. Accordingly, if the user makes a prior arrangement with conceivable calling parties regarding the rule of designation of backlight color, the user of the portable terminal device can identify the calling party of the incoming call. 
     Fourth Embodiment 
     A portable terminal device according to a fourth embodiment of the present invention can indicate an incoming call from a specific calling party through use of the color of backlight of the display means. 
     As shown in FIG. 4, the terminal device comprises receiving means  60  for receiving a signal waveform transmitted from another portable terminal device; reading means  61  for reading the phone number of the calling party from the received signal; comparison means  63  for comparing the phone number of the calling party read by the reading means  61  with the phone numbers stored in the storage means  62 ; and the control means  11  for driving the first drive means  21  or the second drive means  22  on the basis of result of the comparison performed by the comparison means  63 . In other respects, the portable terminal device according to the fourth embodiment is identical in configuration with that according to the first embodiment (shown in FIG. 1) 
     The operation of the portable terminal device will now be described. 
     The reading means  61  reads the phone number of the calling party from the incoming signal received by the receiving means  60  and outputs the thus-read phone number to the comparison means  63 . The comparison means  63  compares the phone number of the calling party with the phone numbers registered in the storage means  62  and outputs the result of such comparison to the control means  11 . 
     When the comparison means  63  detects a match between the compared phone numbers, the control means  11  activates the first control signal  111 . At this time, as previously described in connection with the first embodiment, the light-emitting diode  311  emits the light ray  51  having the first wavelength. In contrast, when the comparison means  63  detects a discrepancy between the compared phone numbers, the control means  11  activates the second control signal  112 . At this time, as previously described in connection with the first embodiment, the light-emitting diode  321  emits the light ray  52  having the second wavelength. 
     Accordingly, when the portable terminal device receives an incoming call from a calling party whose phone number is registered in the storage means  62 , the backlight of the display means  40  assumes the color of the first wavelength. If the portable terminal device receives an incoming call from a calling party who is not registered, the backlight of the display means  40  assumes the color of the second wavelength. Therefore, the user of the portable terminal device can identify the calling party of the incoming call. 
     As mentioned previously, the user of the portable terminal device according to the fourth embodiment can identify an incoming call from a specific calling party from only the color of backlight of the display means  40  without reading characters and figures indicated on the display means  40 . This function can produce a great effect, particularly in darkness. 
     Fifth Embodiment 
     A portable terminal device according to a fifth embodiment indicates whether or not the receiving electric field level reaches a level at which the portable terminal device can operate normally, by means of backlight color of the display means. 
     As shown in FIG. 5 the portable terminal device comprises receiving means  60  for receiving a signal waveform transmitted from another portable terminal device; measurement means  67  for measuring the electric field level of the signal received by the receiving means  60 ; setting means  68  for setting a reference electric field level; and the control means  11  for activating the first drive means  21  and the second drive means  22  on the basis of the result of comparison between the thus-measured electric field level and the reference electric field level. In other respects, the portable terminal device according to the fourth embodiment is identical in configuration with that according to the first embodiment (shown in FIG.  1 ). 
     The operation of the portable terminal device will now be described. 
     A receiving level at which the portable terminal device can perform a normal receiving operation is taken as a first electric field level, and a receiving level at which the portable terminal device cannot perform a normal receiving operation is taken as a second electric field level (or an out-of-range level). The setting means  66  sets a first threshold value for transition from the first electric field level to the second electric field level and a second threshold value for transition from the second electric field level to the first electric field level. 
     When the portable terminal device is in use, the control means  11  compares the receiving electric field level measured by the measurement means  67  with the first threshold value set by the setting means  66 . If the receiving electric field level exceeds the first threshold value, the control means  11  activates the first control signal  111 . At this time, as previously mentioned in connection with the first embodiment, the light-emitting diode  311  emits the light ray  51  having the first wavelength. Further, if the receiving electric field level becomes lower than the first threshold value from this state, the control means  11  activates the second control signal  112 . At this time, as previously mentioned in connection with the first embodiment, the light-emitting diode  312  emits the light ray having the second wavelength. 
     When the receiving electric field is lower than the second threshold value, the control means  11  compares the receiving electric field level measured by the measurement means  67  with the second threshold value set by the setting means  66 . If the receiving electric field level exceeds the second threshold value, the control means  11  activates the first control signal  111 , thereby causing the light-emitting diode  311  to emit the light ray  51  having the first wavelength. 
     Accordingly, when n the backlight color assumes the color of the first wavelength, the user becomes aware that the receiving electric field is sufficient for ensuring normal operations of the terminal device. When the backlight color assumes the color of the second wavelength, the user becomes aware that the receiving electric field is insufficient for ensuring normal operations of the terminal device. 
     Thus, the user of the portable terminal device according to the fifth embodiment instantaneously becomes aware of a change in the receiving electric field level from only the color of backlight of the display means  40  without reading characters and figures indicated on the display means  40 . This function can produce a great effect, particularly in darkness. 
     The previous embodiments describe that the color of backlight of the display means  40  is switched by illuminating solely the first light-emitting means  31  or the second light-emitting means  32 . However, the backlight may be switched to a mixed light ray consisting of the light ray from the first light-emitting means  31  and the light ray from the second light-emitting means  32 , by simultaneously illuminating the first and second light-emitting means  31  and  32 . In this case, the backlight color can be switched between three colors through use of two light-emitting means. 
     The number of light-emitting means may be changed to a value of three or-more. 
     FIG. 6 shows a specific example in which the color of backlight of the display means is switched between three colors. When the portable terminal device is in the receivable range, the backlight assumes a green color at power-on. However, when the portable terminal device is outside of the receivable range, the backlight assumes a red color. Further, even when the voltage level of the battery is reduced to one-quarter of the maximum voltage level, the backlight assumes a red color. When the portable terminal device receives an incoming call from a specific calling party, the backlight assumes a blue color. 
     As mentioned above, the user of the portable terminal device according to the present invention becomes aware of various conditions of the portable terminal device from only a change in the backlight color. 
     As has been mentioned above, the portable terminal device according to the present invention enables instantaneous transmission of the operating status of the portable terminal device to the user. Therefore, the user can simplify operations required for reading characters and figures indicated on the display means, thereby rendering the operations of the portable terminal device easy for children and the aged. 
     Further, the user can correctly ascertain information even in darkness.