Abstract:
An apparatus for controlling the supply of electric power to mobile equipment has a battery checker that checks a remaining battery-level of at least one of plural batteries including main battery. The main battery is installed in a body, and the other batteries are installed in an auxiliary electric power source accessory that is detachably mounted on the body. The apparatus further has a battery-level indicator that indicates a mark so as to represent a remaining battery-level based on a plurality of grades and indicates a common mark in each grade, and a battery selector that selectively uses one of the plural batteries. When the remaining battery-level shifts over a boundary battery-level positioned between grades adjacent to each other, the battery selector selects one of the plural batteries, the remaining battery-level of which is greatest.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to mobile equipment with a battery, such as a camera, PDA, and so on. Especially, it relates to an electric power control in accordance with a remaining battery level.  
         [0003]     2. Description of the Related Art  
         [0004]     In an SLR type camera, an auxiliary battery, a so called “battery grip”, is detachably mounted on a camera body. A main battery in the camera body or the auxiliary battery is selectively utilized, thus the number of captures increases remarkably, and the battery life can be extended. A remaining battery-level is displayed based on two or three grades on an LCD on the camera, and a symbol mark is displayed in accordance with a grade, in which the remaining battery-level is included. The displayed remaining battery-level corresponds to the battery that is current, namely, a remaining battery-level that the user can confirm is a battery-level associated with one of the main battery and the auxiliary battery.  
       SUMMARY OF THE INVENTION  
       [0005]     An object of the present invention is to provide a camera or mobile equipment with at least two batteries that is capable of displaying a total remaining battery-level by selectively using one of the batteries.  
         [0006]     A camera system according to the present invention has a camera body, and an auxiliary electric power source accessory detachably mounted on the camera body. A first battery is installed in the camera body, whereas a second battery is installed in the auxiliary electric power source accessory. The camera system also has a battery checker, a battery-level indicator, and a battery selector. The battery checker checks the remaining battery-level of at least one of the first and second batteries. The battery-level indicator indicates a mark so as to represent a remaining battery-level based on a plurality of grades. For example, the battery-level indicator indicates the remaining battery-level based on 4 grades. Then, the battery-level indicator indicates a common mark in each grade. The battery selector selectively uses one of the first and second batteries. When the remaining battery-level shifts over a boundary battery-level positioned between grades adjacent to each other, the battery selector selects one of the first and second batteries, the remaining battery-level of which is greater than that of the other battery.  
         [0007]     As the battery having more voltage is usually selected, the indicator mark corresponding to the next grade is not displayed unless both voltages shift over the boundary voltage. Consequently, the user confirms the total remaining battery-level by viewing the displayed indicator mark.  
         [0008]     The camera system may have an electric power source situation detector that detects whether the electric power supply situation has changed, for example, if the accessory is mounted on the camera while the main electric power source of the camera is tuned ON. In this case, the battery checker may check the remaining battery-level of the first and second batteries when the electric power supply situation changes.  
         [0009]     To efficiently check the remaining battery-level, the battery checker may check only the battery being used, so long as the remaining battery-level does not shift over the boundary battery-level. The battery checker checks the first and second batteries when the remaining battery-level shifts over the boundary battery-level.  
         [0010]     An apparatus for controlling the supply of electric power to mobile equipment according to another aspect of the present invention has a battery checker that checks the remaining battery-level of at least one of plural batteries including a main battery. The first battery is installed in a body, and the other battery is installed in an auxiliary electric power source accessory that is detachably mounted on the body. The apparatus further has a battery-level indicator that indicates a mark so as to represent a remaining battery-level based on a plurality of grades, and indicates a common mark in each grade, and a battery selector that selectively uses one of the plural batteries. When the remaining battery-level shifts over a boundary battery-level positioned between grades adjacent to each other, the battery selector selects one of the plural batteries, the remaining battery-level of which is greatest. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]     The present invention will be better understood from the description of the preferred embodiment of the invention set fourth below together with the accompanying drawings, in which:  
         [0012]      FIG. 1  is a schematic view of a digital camera according to a present embodiment;  
         [0013]      FIG. 2  is a block diagram of the digital camera;  
         [0014]      FIG. 3  is a view showing an electric power source circuit  14 ;  
         [0015]      FIG. 4  is a view showing a flowchart of a photograph motion process;  
         [0016]      FIG. 5  is a view showing a subroutine of Step S 102  in  FIG. 4 ;  
         [0017]      FIG. 6  is a view showing a subroutine of Step S 212  in  FIG. 5 ;  
         [0018]      FIGS. 7A  to  7 D are views showing an indicator mark corresponding to each grade;  
         [0019]      FIG. 8  is a view showing a range of a remaining battery voltage in each grade;  
         [0020]      FIG. 9  is a view showing a subroutine of Step S 105  in  FIG. 4 ;  
         [0021]      FIG. 10  is a view showing a subroutine of Step S 108  in  FIG. 4 ; and  
         [0022]      FIG. 11  is a view showing a subroutine of Step S 110  in  FIG. 4 . 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0023]     Hereinafter, the preferred embodiments of the present invention are described with reference to the attached drawings.  
         [0024]      FIG. 1  is a schematic view of a digital camera according to the present embodiment.  FIG. 2  is a block diagram of the digital camera.  
         [0025]     The digital camera  10  is an SLR type digital still camera capable of recording and displaying images. A battery grip  11  is detachably mounted on a bottom surface  10 P of the camera  10  as an auxiliary electric power source. A battery  23 A is installed in a battery chamber (not shown) formed in the camera body  10 B, while a battery  23 B is installed in a battery chamber (not shown) formed in the battery grip  11 .  
         [0026]     When an electric power dial  13  is operated by the user, a main switch S 1  shown in  FIG. 2  is turned ON, and electric power is supplied from an electric power source circuit  14  to each circuit shown in  FIG. 2 . The remaining battery-level or exposure values, and so on, are displayed on an LCD  52 . When mounting the battery grip  11  on the camera body  10 B, a connecting terminal  17  is contacted with the camera body  10 B, and the battery grip  11  is fixed to the camera body  10 B by an urge member (not shown). Further, a grip switch S 4  is tuned ON by the connection of a pin  21 , thus the installment of the battery grip  11  is detected.  
         [0027]     When a release button  19  is depressed halfway, a metering switch S 2  is turned ON. Thus, a brightness of a subject is detected by a metering controller  42 , and exposure values such as a shutter speed and F number are calculated. When the release button  19  is depressed fully and a release switch S 3  is turned ON, a shutter (not shown) opens and closes based on a shutter driver  48 . A subject image is formed on a CCD  32  by light passing through a lens  47 , so that image-pixel signals corresponding to the subject image are read from the CCD  32 .  
         [0028]     The image-pixel signals are subjected to various processes in a signal processing circuit  34 , and compressed image data is recorded in a memory card (not shown). When a playback mode is selected by operating a mode dial  15  provided on the camera body  10 B, the photographed image is displayed on an LCD  38  on the back surface of the camera  10 .  
         [0029]     A system control circuit  12  controls the camera  10 , and has a CPU  41 , a ROM  43 , and a RAM  45 . a program for controlling a photograph motion and electric power supply is stored in the ROM  43  in advance. Various data generated by a given process is temporarily stored in the RAM 45 . The system control circuit  12  outputs control signals to a CCD driver  34 , a LCD driver  40 , the metering controller  42 , a focus adjustment controller  44 , lens driver  46 , a pulse generator  50 , and so on. The LCD  52  is driven by another LCD driver (not shown in  FIG. 2 ). The literal information or character information displayed on the LCD panel  52  is changed by a situation of other switches S 4 .  
         [0030]      FIG. 3  is a view showing an electric power source circuit  14 .  
         [0031]     As for the electric power supply, the battery  23 A in the camera body  10 B, the battery  23 B in the battery grip  11 , or outside commercial electric power source is available to supply electric power to the camera. The electric power source circuit  14  selects one from the above three electric power sources, and supplies the electric power.  
         [0032]     The electric power source circuit  14  has four switches  64 ,  66 ,  68 ,  70 , diodes D 1  to D 4 , an outside power source detector  62 , AND circuits  73 ,  76 , and OR circuits  72 ,  74 . The OR circuits  72 ,  74  respectively output a High/Low level signal in accordance with an input signal sent from the system control circuit  12  to a terminal G 1 . The AND circuit  73  outputs a High/Low level signal in accordance with an input signal of a terminal G 2 , while the AND circuit  76  outputs a High/Low level signal in accordance with an input signal of a terminal G 3 .  
         [0033]     When the power is supplied by the battery  23 A in the camera body  10 B, the system control circuit  12  outputs control signals to the terminals G 1 , G 2  respectively so as to make the OR circuits  72 ,  74  output exchange signals for turning ON the switches  64 ,  68 , and so as to make the AND circuit  73  output an exchange signal for turning ON the switch  66 . On the other hand, the system control circuit  12  outputs a control signal to the terminal G 3  so as to make the AND circuit  76  output a signal for maintaining the switch OFF.  
         [0034]     When the power is supplied by the auxiliary battery  23 B in the battery grip  11 , the system control circuit  12  outputs control signals to the terminals G 1 , G 3  so as to make the OR circuits  72 ,  74  output exchange signals for turning ON the switches  64 ,  68 , and make the AND circuit  76  output an exchange signal for turning ON the switch  70 . On the other hand, the system control circuit  12  outputs a control signal to the terminal G 2  so as to make the AND circuit  73  output an exchange signal for maintaining the switch  66  OFF.  
         [0035]     The outside power source detector  62  detects whether the AC/DC adapter  25  is connected to the camera  10 , namely, whether the commercial electric power source is used. When the AC/DC adapter  25  is connected to the camera  10 , a detecting signal is output to the system control circuit  12  via a terminal G 4 . The system control circuit  12  outputs control signals to the terminals G 2 , G 3  so as to make the AND circuits  73 ,  76  exchange output signals for turning the switches  66 ,  70  OFF. Note, the terminal G 1  is maintained in the ON situation to allow the battery grip  11  to be detached and mounted.  
         [0036]     With reference to FIGS.  4  to  11 , power source controlling process and a remaining battery level indicating process are explained.  
         [0037]      FIG. 4  is a view showing a flowchart of a photograph motion process performed by the system control circuit  12 . The process starts when the electric power source is turned ON.  
         [0038]     In Step S 101 , the initial setting process, such as a register initial setting, data reading process in the RAM  43 , and so on, is performed. In Step S 102 , an initial battery check process is performed.  
         [0039]      FIG. 5  is a view showing a subroutine of Step S 102  in  FIG. 4 , or the initial battery check process in  FIG. 4 .  
         [0040]     In Step S 201 , it is determined whether the outside commercial power source is supplied to the camera  10  via the AC/DC adapter  25 . When it is determined that an outside commercial power source is supplied to the camera  10 , control signals are output from the system control circuit  12  to the electric power source circuit  14  so as not to use the batteries  23 A and  23 B. On the other hand, when it is determined that an outside commercial power source is not supplied to the camera  10 , the process goes to Step  5202 .  
         [0041]     In Step S 202 , to perform the battery-check process for the battery  23 A in the camera  10 , a control signal is fed from the system control circuit  12  to the electric power source circuit  14  such that the electric power (voltage) according to the battery  23 A is input to the electric power source circuit  14 . In Step S 203 , a voltage “V b ”of the battery  23 A is detected to check the remaining battery-level.  
         [0042]     In Step S 204 , to perform the battery-check process for the battery  23 B in the battery grip  11 , a control signal is fed from the system control circuit  12  to the electric power source circuit  14  such that the electric power (voltage) according to the battery  23 B is input to the electric power source circuit  14 . In Step S 205 , a voltage “V g ” of the battery  23 B is detected to check the remaining battery level. In Step S 206 , it is determined whether the voltage “V b ” of the battery  23 A is smaller than the voltage “V g ” of the battery  23 B in order to compare the remaining battery-level of the battery  23 A with the remaining battery-level of the battery  23 B. In this embodiment, one battery, the remaining battery-level of which is more than that of the other battery, is selected and used.  
         [0043]     When it is determined that the voltage “V b ” of the battery  23 A is smaller than the voltage “V g ” of the battery  23 B in Step S 206 , the process goes to Step S 207 , wherein it is decided that the electric power is supplied to the camera  10  by using the battery  23 B in the battery grip  11 , and a remaining battery voltage “V C ” is set to the voltage “V g ”. The remaining battery voltage “V C ” indicates a voltage of the remaining battery-level of the used battery. The remaining battery-level is determined in accordance with the remaining battery voltage “V C ”. After Step S 207  is performed, the process goes to Step S 208 .  
         [0044]     In Step S 208 , it is determined whether the battery grip  11  is mounted on the camera  10 . When it is determined that the battery grip  11  is not mounted to the camera  10 , the process goes to Step S 209 , wherein a warning display process is performed as described later. On the other hand, when it is determined that the battery grip  11  is mounted to the camera  10 , the process goes to. Step S 212 .  
         [0045]     On the other hand, when it is determined that the voltage “V b ” of the battery  23 A is not smaller than the voltage “V g ” of the battery  23 B in Step S 206 , the process goes to Step S 210 . In Step S 210 , it is decided that the electric power is supplied to the camera  10  by using the battery  23 A in the camera body  10 B, and the remaining battery voltage “V C ” is set to the voltage “V b ”.  
         [0046]     In Step S 211 , since the voltage “V g ” is input to the electric power source circuit  14  by the performance of Step S 205 , a control signal is output from the system control circuit  12  to the electric power source circuit  14  so as to supply the electric power by using the battery  23 A. After Step S 211  is performed, the process goes to Step S 212 , wherein an indicator mark setting process for indicating the remaining battery-level by a mark is performed.  
         [0047]      FIG. 6  is a view showing a subroutine of Step S 212  in  FIG. 5 .  FIGS. 7A  to  7 D are views showing an indicator mark corresponding to each grade.  FIG. 8  is a view showing a range of the remaining battery voltage “V C ” in each grade.  
         [0048]     As shown in  FIG. 8 , a total range of the remaining battery level is divided into four grades, or four stages “A” “B” “C”, and “D”. Herein, the range from the maximum voltage “V max ” to a half voltage “V H ” indicating the half battery-level is set to “A grade”, the range from the half voltage “V H ” to a small voltage “V E ” indicating a little voltage, which indicates a alight battery-level, is set to “B grade”, the range from the small voltage “V E ” to a limited voltage “V N ” indicating the necessity for the battery-exchange is set to “C grade”, and the range equal to or less than the limited voltage “V N ”, is set to “D grade”.  
         [0049]     As shown in  FIGS. 7A  to  7 D, while the camera  10  is used, a remaining battery-level mark NB is displayed on the LCD  52  in accordance with the four grades A to D shown in  FIG. 6 . The remaining battery-level mark “NB” is constructed of three parts F 1 , F 2 , and F 3 . The part F 3  represents a frame, the part F 1  represents a rectangular-area with hatched-lines, which is the half of the area in the part F 3 , and the part F 2  represents the remaining rectangular-area.  
         [0050]     The Four types of indicator mark are prepared and one type is selectively displayed. When the remaining battery voltage “V C ” is in the “A” grade, the parts F 1  to F 3  are displayed on the LCD  52 , whereas, when the remaining battery voltage “V C ” is in the “B” stage, the parts F 1  and F 3  are displayed on the LCD  52 . When the remaining battery voltage “V C ” is in the “C” grade, only the mark F 3  is displayed on the LCD  52 . Then, when the remaining battery voltage “V C ” is in the “D” grade, the mark F 3  is displayed while blinking. Note, when the electric power cannot be supplied to the camera due to any reason and the photograph motion cannot be performed, the remaining battery-level mark NB corresponding to the “D” grade shown in  FIG. 7D  is displayed. Also, when using the commercial electric power, the remaining battery-level mark NB is not displayed.  
         [0051]     In Step S 301  shown in  FIG. 6 , it is determined whether the remaining battery voltage “V C ” is equal to or less than the limited voltage “V N ”. When it is determined that the remaining battery voltage “V C ” is equal to or less than the limited voltage “V N ”, the process goes to Step S 302 , wherein a flag for displaying the remaining battery level-mark NB. corresponding to the “D” grade, is set.  
         [0052]     On the other hand, when it is determined that the remaining battery voltage “V C ” is not equal to or less than the limited voltage “V N ” in Step S 301 , the process goes to Step S 303 , wherein it is determined whether the remaining battery voltage “V C ” is equal to or less than the small voltage “V E ”. When it is determined that the remaining battery voltage “V C ” is equal to or less than the small voltage “V E ”, the process goes to Step S 304 , wherein a flag for displaying the remaining battery level mark NB, corresponding to the “C” grade, is set.  
         [0053]     On the other hand, when it is determined that the remaining battery voltage “V C ” is not equal to or less than the small voltage “V E ” in Step S 303 , the process goes to Step S 305 , wherein it is determined whether the remaining battery voltage “V C ”, is equal to or less than the half voltage “V H ”. When it is determined that the remaining battery voltage “V C ” is equal to or less than the half voltage “V H ”, the process goes to Step S 306 , wherein a flag for displaying the remaining battery level mark NB, corresponding to the “B” grade, is set. On the other hand, when it is determined that the remaining battery voltage “V C ” is not equal to or less than the half voltage “V H ”, the process goes to Step S 307 , wherein a flag for displaying the remaining battery level mark NB, corresponding to the “A” grade, is set.  
         [0054]     After step S 307  is performed, the indicator mark setting process of subroutine is terminated. When Step S 209  or S 212  in  FIG. 5  is performed, the process returns to Step S 103  in  FIG. 4 .  
         [0055]     In Step S 103 , it is determined whether the operation for turning the electric power source OFF has been performed by the user. When it is determined that the operation for turning the electric power source OFF has been performed, the process goes to Step S 104 , wherein the process for turning the power OFF is performed. On the other hand, when it is determined that the operation for turning the electric power source OFF has not yet been performed, the process goes to Step S 105 , wherein the power source check process is performed.  
         [0056]      FIG. 9  is a view showing a subroutine of Step S 105  in  FIG. 4 .  
         [0057]     In Step S 401 , it is determined whether the AC/DC adapter  25  is connected to the camera  10 , to use the outside commercial electric power. When it is determined that the AC/DC adapter  25  is connected to the camera  10 , the process goes to Step S 405 , wherein a control signal for using the commercial electric power is output to the electric power source circuit  14 . On the other hand, when it is determined that the AC/DC adapter  25  is not connected to the camera  10 , the process goes to Step S 402 .  
         [0058]     In Step S 402 , it is determined whether the AC/DC adapter is detached from the camera  10  when using the commercial electric power. When it is determined that the AC/DC adapter is detached from the camera  10  when using the commercial electric power, the process goes to Step S 406 , wherein the initial battery check process shown in  FIGS. 5 and 6  is performed. On the other hand, when it is determined that the AC/DC adapter is not detached from the camera  10  when using the commercial electric power, the process goes to Step S 403 , wherein it is determined whether the battery grip  11  is mounted on the camera  10 .  
         [0059]     When it is determined that the battery grip  11  is mounted on the camera  10 , the process goes to Step S 406 , wherein the initial battery check process is performed. Namely, the battery-check is performed for both batteries  23 A and  23 B since the electric power supply situation is changed. On the other hand, when it is determined that the battery grip  11  is not mounted on the camera  10 , the process goes to Step S 404 , wherein it is determined whether the battery grip  11  is detached form the camera  10 , when using the battery  23 B. When it is determined that the battery grip  11  is detached form the camera  10  when using the battery  23 B, the process goes to Step S 406 , wherein the initial battery check process is performed since the electric power supply situation is changed. On the other hand, when it is determined that the battery grip  11  is not detached form the camera  10  when using the battery the subroutine is terminated. Also, after Step S 405  or S 406  is performed, the process returns to Step S 106  in  FIG. 4 .  
         [0060]     In Step S 106 , the remaining battery-level mark NB is displayed on the LCD  52  on the basis of the flag, which is set by Step S 302 , S 304 , S 306 , or S 307  in  FIG. 6 . Namely, one type of indicator mark NB, which corresponds to the selected grade encompassing the detected remaining voltage “V C ”, is selected from the four types of indicator marks shown in  FIGS. 7A  to  7 D.  
         [0061]     In Step S 107 , it is determined whether the metering switch S 2  is tuned ON by depressing the release button  19  halfway. When it is determined that the metering switch S 2  is tuned ON, the process goes to Step S 108 , wherein the battery check process is performed. The battery check process is a process that changes the type of the indicator mark (the remaining battery-level mark) NB in accordance with the decrease of the detected remaining battery voltage “V C ”.  
         [0062]      FIG. 10  is a view showing a subroutine of Step S 108  in  FIG. 4 .  
         [0063]     In Step S 501 , the flag, which has been set in Step S 302 , S 304 , S 306 , or S 307 , is read or extracted from the RAM  43  temporarily. Namely, the type of the indicator mark NB displayed on the LCD is detected. In Step S 502 , it is determined whether the AC/DC adapter  25  is connected to the camera  10 . When it is determined that the AC/DC adapter  25  is connected to the camera  10 , the process is directly terminated. On the other hand, when it is determined that the AC/DC adapter  25  is not connected to the camera  10 , the process goes to Step S 503 , wherein it is determined whether the battery grip  11  is mounted on the camera  10 .  
         [0064]     When it is determined that the battery grip  11  is not mounted on the camera  10  in Step S 503 , the process goes to Step S 507 , a control signal is output to the electric power source circuit  14  so as to input the voltage of the battery  23 A to the electric power source circuit  14 . Then, in Step S 508 , the present voltage “V b ” of the battery  23 A is detected. In Step S 509 , the detected voltage “V b ” is set to the remaining battery voltage “V C ”. After Step S 509  is performed, the process goes to Step S 510 .  
         [0065]     On the other and, when it is determined that the battery grip  11  is mounted on the camera  10 , the process goes to Step S 504 . In Step S 504 , a control signal is output to the electric power source circuit  14  so as to allow the electric power source circuit  14  to detect the voltage of the selected battery in Step S 207  and S 210  shown in  FIG. 5 . In Step S 505 , the present voltage, namely the voltage “V b ” of the battery  23 A or the voltage “V g ” of the battery  23 B is detected. In Step S 506 , the detected voltage V b /V g  is set to the remaining voltage “V C ”. While the type of the indicator mark NB is not changed, the battery-check is performed on only the selected and used battery. After Step S 506  is performed, the process goes to Step S 510 .  
         [0066]     In Step S 510 , it is determined whether the type of the remaining battery level mark NB, corresponding to the remaining voltage “V C ” set by Step S 506  or S 509 , coincides with the type of the remaining battery level mark NB corresponding to the flag extracted by Step S 501 . Namely, it is determined whether the type of the indicator mark NB should be changed since the remaining battery voltage “V C ” shifts from the “A” grade to “B” grade, “B” grade to “C” grade, or “C” grade to “D” grade due to the exhaustion of the used battery.  
         [0067]     When it is determined that the type of the indicator mark NB should be changed since the remaining battery voltage “V C ” shifts over a boundary voltage, which is positioned at boundary level between the adjacent grades, the process goes to Step S 511 , wherein the initial battery check process shown in  FIG. 5  is performed. Namely, the battery check is performed for the batteries  23 A and  23 B, and one battery, the remaining battery voltage of which is more than the other battery, is selected. On the other hand, when it is determined that the type of indicator mark NB should be maintained since the remaining battery voltage has not shifted to the boundary voltage, the process goes to Step S 512 , wherein the battery check is not performed, instead the indicator mark setting process shown in  FIG. 6  is performed. After Step S 511  or S 512  is performed, the process goes to Step S 109  in  FIG. 4 .  
         [0068]     In Step S 109 , it is determined whether the photograph motion is impossible as the remaining battery voltage “V C ” is in the D grade. When it is determined that the photograph motion is impossible, the process returns to Step S 105 . On the other hand, when it is determined that the photograph motion is possible, the process goes to Step S 110 , wherein the photograph motion is performed.  
         [0069]      FIG. 11  is a view showing a subroutine of Step S 110  in  FIG. 4 .  
         [0070]     In Step S 601 , a time count process starts to measure a loop-interval of the photograph motion. Herein, timer-interval, which is a multiple of  128  [ms], is checked as a loop-interval. In Step S 602 , the power source check process shown in  FIG. 9  is performed. In Step S 603 , it is determined whether the release button  19  cannot be depressed fully, for any reason. When it is determined that the release button  19  cannot be depressed fully, the process is terminated. On the other hand, when it is determined that the release button  19  can be depressed fully, the process goes to Step S 604 .  
         [0071]     In Step S 604 , exposure values such as shutter speed and F. number are calculated on the basis of the detected brightness of the subject, and the lens is driven to focus the subject. In Step S 605 , it is determined whether the release switch S 3  is tuned ON by depressing the release button  19  fully. When it is determined that the release switch S 3  is tuned ON, the process skips to Step S 609 . On the other hand, when it is determined that the release switch S 3  is not tuned ON, the process goes to Step S 606 , wherein the battery check process shown in  FIG. 10  is performed. In Step S 607 , it is determined whether the photograph motion cannot be performed since the remaining battery voltage “V C ” is small. When it is determined that the photograph motion cannot be performed, the process skips to Step S 609 . On the other hand, when it is determined that the photograph motion can be performed, the process goes to Step S 608 , the photograph motion is performed to record the subject image.  
         [0072]     In Step S 609 , the time is counted to check time-interval. In Step S 610 , it is determined whether the photograph motion process should be terminated after passing the time-interval. When it is determined that the time has not passed the time-interval, the process returns to Step S 602 . On the other hand, when it is determined that the photograph motion process should be terminated, the photograph motion process is terminated.  
         [0073]     In this way, in this embodiment, one of the battery  23 A in the camera body  10 B and the battery  23 B in the battery grip  11  is selectively used, namely, the battery, which has a greater remaining voltage compared to that of the other, is used. On the other hand, one of the four types of indicator marks NB is displayed on the LCD  52 . When the remaining battery voltage shifts over the boundary voltage level “V H ” “V E ” or “V N ”, the remaining voltages of the batteries  23 A and  23 B are checked, the battery having a greater remaining voltage is selected and used. Thus, the total remaining battery-level of the batteries  23 A and  23 B is displayed by the four types of indicator mark NB, and the indicator mark NB is displayed step by step.  
         [0074]     The number of batteries may be set to three or another number. The number of indicator mark types may be different to the number in the above embodiment. The electric power supply control described above may be applied to mobile equipment with a main battery and an auxiliary battery, such a cellar-phone, PDA, and so on. Further, The electric power supply control described above may be applied to mobile equipment with plural batteries (for example, three or four batteries).  
         [0075]     Finally, it will be understood by those skilled in the art that the foregoing description is of preferred embodiments of the device, and that various changes and modifications may be made to the present invention without departing from the spirit and scope thereof.  
         [0076]     The present disclosure relates to subject matters contained in Japanese Patent Application No. 2004-177990 (filed on Jun. 16, 2004), which is expressly incorporated herein, by reference, in its entirety.