Abstract:
An electro-optical apparatus is provided that has a plurality of scanning lines, a plurality of signal lines, and electro-optical devices that are each being placed at an intersection of each of the scanning lines and each of the signal lines. The electro-optical apparatus is driven according to the amount of drive current supplied to the electro-optical devices. The electro-optical apparatus includes a lighting time measuring unit to measure a lighting time of the electro-optical devices, a lighting time storage unit to store the lighting time obtained by the lighting time measuring unit, and a drive current amount adjusting unit to adjust the amount of drive current based on the lighting time stored in the lighting time storage unit so as to correct the brightness of the electro-optical devices.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of Invention 
   The present invention relates to an electro-optical apparatus, a driving method thereof, and an electronic device. 
   2. Description of Related Art 
   In related art organic EL display apparatuses, for example, the degradation of the luminous brightness of organic EL devices of the organic EL display apparatuses over time is much more rapid than that of inorganic EL display apparatuses. That is, as the lighting time accumulates, the reduction in brightness becomes noticeable. As an example, in the organic EL display apparatuses, the lighting time with a luminance of, for example, 300 cd/m 2  is up to approximately 10,000 hours. 
   Accordingly, this drawback can be overcome by enhancing the manufacturing process so that the reduction in brightness is prevented, as disclosed in Japanese Unexamined Patent Application Publication No. 11-154596, and Japanese Unexamined Patent Application Publication No. 11-214157. 
   SUMMARY OF THE INVENTION 
   In reality, however, with the approach of enhancing the manufacturing process, it is difficult to completely prevent the reduction in brightness. The present invention addresses or overcomes this and/or other problems, and provides a technique for compensating for a change in brightness over time by use of an approach involving circuit technology. 
   The present invention provides a first electro-optical apparatus having a plurality of electro-optical devices, whose brightness is defined according to the amount of drive power supplied to the plurality of electro-optical devices. The electro-optical apparatus includes a lighting time measuring unit to measure a lighting time of the electro-optical devices; a lighting time storage unit to store the lighting time measured by the lighting time measuring unit; and a drive power amount adjusting unit to adjust the amount of drive power based on the lighting time stored in the lighting time storage unit. 
   The present invention also provides a second electro-optical apparatus having a plurality of scanning lines, a plurality of signal lines, and electro-optical devices placed at intersections of the plurality of scanning lines and the plurality of signal lines, whose brightness is defined according to data signals supplied via the plurality of signal lines. The electro-optical apparatus includes a data signal measuring unit to measure the amount of data signals supplied via the plurality of signal lines; a data signal amount storage unit to store the data signal measured by the data signal measuring unit; and a drive power amount adjusting unit to adjust the amount of drive power based on the amount of data signals stored in the data signal amount storage unit. 
   In the above-described electro-optical apparatus, the electro-optical devices may include three types of electro-optical devices for R, G, and B (red, green, and blue); the data signal amount measuring unit may measure the amount of data signals for each of the three types of electro-optical devices; the data signal amount storage unit may store the amount of data signals for each of the three types of electro-optical devices measured by the data signal amount measuring unit; and the drive current amount adjusting unit may adjust the amount of drive power based on the amount of data signals stored for each of the three types of electro-optical devices in the data signal storage unit. 
   In the above-noted electro-optical apparatus, specifically, the drive power amount adjusting unit may be, for example, a data correction circuit to modify digital data or analog data according to the accumulated lighting time or the accumulated amount of data signals, or a drive voltage control circuit to adjust a drive voltage applied to the electro-optical devices. The drive power amount adjusting unit may also be a circuit to generate a reference voltage of a DAC to generate analog data supplied to the electro-optical devices. 
   An electronic device of the present invention includes the above-noted electro-optical apparatus. 
   The present invention also provides a first driving method of an electro-optical apparatus having an electro-optical device. The driving method includes: measuring a lighting time of the electro-optical device; storing the measured lighting time; and adjusting the amount of drive power supplied to the electro-optical device based on the stored lighting time. 
   The present invention also provides a second driving method of an electro-optical apparatus having a plurality of scanning lines, a plurality of signal lines, and electro-optical devices each being placed at an intersection of each of the scanning lines and each of the signal lines, the electro-optical apparatus being driven according to the amount of drive power and image data supplied to the electro-optical devices. The driving method includes: measuring the amount of image data supplied to the electro-optical devices; storing the measured amount of image data; and adjacent the amount of drive power based on the stored amount of image data. 
   In the above-noted driving method, the amount of image data may be measured for each of three colors, R, G, and B (red, green, and blue); the amount of image data measured for each of R, G, and B may be stored, and the amount of drive power may be adjusted based on the stored amount of image data for each of R, G, and B. 
   In the present invention, pixel colors are not limited to three colors, R, G, and B (red, green, and blue), and any other color may be used. 
   Other features of the present invention will become apparent from the accompanying drawings and the following description. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIGS. 1(   a ) and  1 ( b ) are schematics of an organic EL display apparatus according to a first exemplary embodiment of the present invention, where  FIG. 1(   a ) is a schematic of the control of the overall apparatus, and  FIG. 1(   b ) is a schematic of the control of a drive current control circuit  40 ; 
       FIG. 2  is a flowchart showing the operation of a sequence control circuit  10  of the organic EL display apparatus according to the first exemplary embodiment of the present invention; 
       FIG. 3  is a graph of luminance with respect to the driver drive current in the organic EL display apparatus according to an exemplary embodiment of the present invention; 
       FIG. 4  is a schematic of the control of an organic EL display apparatus according to a second exemplary embodiment of the present invention; 
       FIG. 5  is a flowchart showing the operation of a sequence control circuit  10  of the organic EL display apparatus according to the second exemplary embodiment of the present invention; 
       FIG. 6  is a schematic of the control of an organic EL display apparatus according to a third exemplary embodiment of the present invention; 
       FIG. 7  is a flowchart showing the operation of a sequence control circuit  10  of the organic EL display apparatus according to the third exemplary embodiment of the present invention; 
       FIG. 8  is a luminance life characteristic graph of an organic EL display apparatus of the related art; 
       FIG. 9  is a luminance life characteristic graph of an organic EL display apparatus according to an exemplary embodiment of the present invention; 
       FIGS. 10(   a ) and  10 ( b ) are schematics of an organic EL display apparatus according to a first application of the present invention, wherein  FIG. 10(   a ) is a schematic of the control of the overall apparatus, and  FIG. 10(   b ) is a schematic of the control of a drive voltage control circuit  70 ; 
       FIGS. 11(   a ) and  11 ( b ) are schematics of an organic EL display apparatus according to a second application of the present invention, where  FIG. 11(   a ) is a schematic of the control of the overall apparatus; and  FIG. 11(   b ) is a schematic of a data correction circuit  80 ; 
       FIG. 12  is a schematic perspective view showing an example in which an electro-optical apparatus of the present invention is applied to a mobile personal computer; 
       FIG. 13  is a schematic perspective view showing an example in which an electro-optical apparatus of the present invention is applied to a display unit of a cellular phone; 
       FIG. 14  is a schematic perspective view of a digital still camera having a finder that is implemented by an electro-optical apparatus of the present invention. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   An exemplary embodiment of the present invention is described below. In this exemplary embodiment, an electro-optical apparatus implemented as a display apparatus (hereinafter “an organic EL display apparatus”) which employs organic electroluminescent devices (hereinafter “organic EL devices”), and a driving method thereof are described, by way of example. 
   First, the organic EL display apparatus is briefly described. As is well known in the art, an organic EL panel constituting the organic EL display apparatus is formed of a matrix of unit pixels including organic EL devices. The circuit structure and operation of the unit pixels are such that, for example, as described in a book titled “ELECTRONIC DISPLAYS” (Shoichi Matsumoto, published by Ohmsha on Jun. 20, 1996) (mainly, page 137), a drive current is supplied to each of the unit pixels to write a predetermined voltage to an analog memory formed of two transistors and a capacitor so as to control lighting (illumination) of the organic EL devices. 
   In the exemplary embodiments according to the present invention, the lighting time of the organic EL display apparatus is directly or indirectly measured to adjust the value of a current supplied to the organic EL devices according to the accumulated lighting time. 
   FIRST EXEMPLARY EMBODIMENT 
   In the first exemplary embodiment, a frame synchronizing signal FCLK described below is counted in order to measure the accumulated lighting time of the organic EL display apparatus. 
   Specifically, as shown in  FIG. 1(   a ), the organic EL display apparatus according to the first exemplary embodiment includes a sequence control circuit  10 , a non-volatile memory  20 , such as a flash memory, an FCLK counter  30 , a drive current control circuit  40 , a driver  50  formed of a well-known DAC (D/A converter) and a constant-current driving circuit, and an organic EL panel  60 . As shown in  FIG. 1(   b ), the drive current control circuit  40  includes an output correction table  40   a , a selector  40   b , and a DAC (D/A converter)  40   c.    
   The operation of the sequence control circuit  10  is described below. As shown in schematics of  FIGS. 1(   a ) and  1 ( b ), the sequence control circuit  10  reads an accumulated lighting time a stored in the non-volatile memory  20  (this operation corresponds to step S 10  in the flowchart of  FIG. 2) . Typically, the accumulated lighting time a is preferably the time starting from initial use immediately after shipment of the apparatus. The sequence control circuit  10  outputs a readout signal b 1 , which is “H”, to the non-volatile memory  20  to enable readout of the accumulated lighting time a. 
   Then, the sequence control circuit  10  outputs a select signal c corresponding to the accumulated lighting time a to the drive current control circuit  40 . The selector  40   b  receives the select signal c from the sequence control circuit  10 , and outputs a signal d to the DAC  40   c  with reference to the output correction table  40   a  in order to adjust the brightness based on the accumulated lighting time. In response to the output signal d, based on a central voltage Vcen, the DAC  40   c  outputs a reference voltage Vref, which becomes the central voltage of the DAC included in the driver  50 , to the driver  50  (this operation corresponds to step S 20  shown in  FIG. 2 ). Preferably, the central voltage Vcen is preset at the manufacturing or shipment time of the apparatus. 
   Then, the sequence control circuit  10  transfers the accumulated lighting time a of the non-volatile memory  20  to the FCLK counter  30  (this operation corresponds to step S 30  shown in  FIG. 2 ), before outputting a display-enable signal (f=“H”) and a frame synchronizing signal g to the FCLK counter  30  (this operation corresponds to step S 40  shown in  FIG. 2 ). Then, the sequence control circuit  10  is designed such that digital data h for Red, Green, and Blue (hereinafter “RGB data”) are input from the sequence control circuit  10  to the DAC included in the driver  50  (this operation corresponds to step S 50  shown in  FIG. 2 ). The digital data h is subjected to digital-to-analog conversion in the driver  50  based on at least the above-described reference voltage Vref, which is obtained based on the accumulated lighting time a, immediately after supply of the digital data h starts, and analog data e corresponding to the digital data h is supplied to the organic EL panel  60 . That is, if the same digital data is input to the driver  50 , the analog data e which has been corrected based on the accumulated lighting time a is supplied to the organic EL panel  60 . The analog data e may be either a voltage signal or a current signal. 
   During output of the digital data h, the predetermined analog data e is supplied to the organic EL panel  60  via the driver  50  to display an image on the organic EL panel  60 , and the frame synchronizing signal g is counted by the FCLK counter  30 . The FCLK counter  30  adds the count value of the frame synchronizing signal g to the previously read accumulated lighting time a to generate count data i. 
   Then, the sequence control circuit  10  stops outputting the RGB data so that the organic EL panel  60  is made to enter a non-display state, thus outputting a display-disable signal (f=“L”) to the FCLK counter  30 , and also stops outputting the frame synchronizing signal g (this operation corresponds to step S 60  shown in  FIG. 2 ). Thus, counting of the frame synchronizing signal g terminates. Then, the count data i obtained by the FCLK counter  30  is written to the non-volatile memory  20  (this operation corresponds to step S 70  shown in  FIG. 2 ). The sequence control circuit  10  outputs a non-volatile memory writing signal b 2 , which is “H”, to the non-volatile memory  20  to enable writing of the count data i. The written count data i serves as a new accumulated lighting time a. 
   The sequence control circuit  10 , the FCLK counter  30 , the output correction table  40   a , the selector  40   b , and the DAC  40   c  can be implemented by software or hardware, as required. The driver  50  can be implemented by either a current driving circuit or a voltage driving circuit. 
   A brightness correcting method according to the present invention is described below in the context that the analog data e represents a current signal.  FIG. 3  is a characteristic graph of the brightness with respect to the driver driving current supplied to the organic EL panel  60 . In  FIG. 3 , the characteristic graph showing accumulated lighting time t 1  at initial use exhibits luminance L 1  with respect to current level Ia. However, the characteristic graph showing accumulated lighting time t 10 , where the characteristic changes due to degradation over time, exhibits luminance L 10  with respect to the same current level Ia, resulting in lower luminance than that of the accumulated lighting time t 1 . Thus, in order to obtain a luminance equivalent to luminance L 1  in the graph of the accumulated lighting time t 1  at initial use, the current level is corrected based on the above-described accumulated lighting time a and output correction table  40   a  shown in  FIG. 1  to obtain a resulting value Ib. 
   SECOND EXEMPLARY EMBODIMENT 
   In the second exemplary embodiment, the total sum of image data described below is counted to estimate the accumulated luminance of the organic EL display apparatus, thereby defining the central voltage of the DAC included in the driver  50 . Other portions than this portion are common to those in the aforementioned first embodiment, and therefore the difference therebetween is primarily described below. 
   Specifically, as shown in  FIG. 4 , the organic EL display apparatus according to the second exemplary embodiment includes an RGB counter  31  in place of the FCLK counter  30  shown in  FIGS. 1(   a ) and  1 ( b ). The RGB counter  31  may measure, as the accumulated luminance, the amount of data for at least one of R, G, and B types of electro-optical devices. In the second exemplary embodiment, the RGB counter  31  measures, as the accumulated luminance, the amount of data for all R, G, and B. 
   The operation of the sequence control circuit is described below. As shown in the schematic of  FIG. 4 , the sequence control circuit  10  reads accumulated luminance j stored in the non-volatile memory  20  (this operation corresponds to step S 10  in the flowchart of  FIG. 5 ). The sequence control circuit  10  outputs a readout signal b 1 , which is “H”, to the non-volatile memory  20  to enable readout of the accumulated luminance j. Then, the sequence control circuit  10  outputs a select signal c corresponding to the accumulated luminance j to the drive current control circuit  40 . The drive current control circuit  40  has a similar structure to that shown in  FIG. 1(   b ). The selector  40   b  receives the select signal c from the sequence control circuit  10 , and outputs a predetermined signal to the DAC  40   c  with reference to the output correction table  40   a  in order to adjust the brightness based on the accumulated luminance. In response to this output signal, the DAC  40   c  outputs a reference voltage Vref obtained based on a central voltage Vcen to the driver  50  (this operation corresponds to step S 20  shown in  FIG. 5) . 
   Then, the sequence control circuit  10  transfers the accumulated luminance j of the non-volatile memory  20  to the RGB counter  31  (this operation corresponds to step S 30  shown in  FIG. 5 ), before outputting a display-enable signal (f=“H”) and a frame synchronizing signal g (for example, a synchronization clock to transfer one pixel data rather than a clock for each frame) to the RGB counter  31  (this operation corresponds to step S 40  shown in  FIG. 5 ). Then, the sequence control circuit  10  supplies digital data (hereinafter referred to as RGB data) h for R, G, and B to the driver  50 , and also outputs it to the RGB counter  31  (this operation corresponds to step S 50  shown in  FIG. 5 ). During output of the RGB data h, the RGB data h is converted into analog data e by the driver  50  based on the reference voltage Vref defined for the accumulated luminance j, and the analog data e is supplied to the organic EL panel  60 . 
   After supply of the RGB data h starts, the total sum of the RGB data h is counted by the RGB counter  31 . The RGB counter  31  adds the count value of the total sum of each RGB data h to the previously read accumulated luminance j to generate count data k. 
   Then, the sequence control circuit  10  stops outputting the RGB data h so that the organic EL panel  60  is made to enter a non-display state, thus outputting a display-disable signal (f=“L”) to the RGB counter  31 , and also stops outputting the frame synchronizing signal g (this operation corresponds to step S 60  shown in  FIG. 5 ). Thus, counting of the total sum of the RGB data h terminates. Then, the count data k obtained by the RGB counter  31  is written to the non-volatile memory  20  (this operation corresponds to step S 70  shown in  FIG. 5 ). The sequence control circuit  10  outputs a non-volatile memory writing signal b 2 , which is “H”, to the non-volatile memory  20  to enable writing of the count data k. The written count data k serves as a new accumulated luminance j. 
   The sequence control circuit  10 , the RGB counter  31 , the output correction table  40   a , the selector  40   b , and the DAC  40   c  can be implemented by software or hardware, as required. The driver  50  can be implemented by either a current driving circuit or a voltage driving circuit. A brightness correcting method according to the second exemplary embodiment is similar to that described above in the first exemplary embodiment. 
   THIRD EXEMPLARY EMBODIMENT 
   In the third exemplary embodiment, image data described below is counted for each of R, G, and B to estimate an accumulated luminance of the organic EL display apparatus. This allows accurate estimation of the accumulated luminance. Other portions than this portion are common to those in the above-described second embodiment, and therefore the difference therebetween is primarily described below. 
   Specifically, as shown in  FIG. 6 , in the organic EL display apparatus of the third exemplary embodiment, the non-volatile memory  20  shown in  FIG. 4  is formed of a non-volatile memory  20   a  for R, a non-volatile memory  20   b  for G, and a non-volatile memory  20   c  for B, and the RGB counter  31  shown in  FIG. 4  is formed of a counter  31   a  for R, a counter  31   b  for G, and a counter  31   c  for B. Furthermore, the drive current control circuit  40  shown in  FIG. 4  is formed of a circuit  41  for R, a circuit  42  for G, and a circuit  43  for B. 
   The operation of the sequence control circuit is described below. As shown in the schematic of  FIG. 6 , the sequence control circuit  10  reads accumulated luminances j 1  for R, j 2  for G, and j 3  for B stored in the non-volatile memories  20   a ,  20   b , and  20   c , respectively (this operation corresponds to step S 10  in the flowchart of  FIG. 7 ). The sequence control circuit  10  outputs a readout signal b 1 , which is “H”, to the non-volatile memory  20  to enable readout of the accumulated luminances j 1  for R, j 2  for G, and j 3  for B. Then, the sequence control circuit  10  outputs select signals c 1 , c 2 , and c 3  corresponding to the accumulated luminances j 1 , j 2 , and j 3 , respectively, to the drive current control circuits  41 ,  42 , and  43 , respectively. Each of the drive current control circuits  41 ,  42 , and  43  has a similar structure to that shown in  FIG. 1(   b ). The selectors  40   b  of the drive current control circuits  41 ,  42 , and  43  receive the respective select signals c 1 , c 2 , and c 3  from the sequence control circuit  10 , and output predetermined signals to the DACs  40   c  with reference to the output correction tables  40   a  in order to adjust the brightness based on the accumulated luminances for R, G, and B. In response to the output signals, the DACs  40   c  output to the driver  50  reference voltages VrefR, VrefG, and VrefB obtained for R, G, and B based on a central voltage Vcen (this operation corresponds to step S 20  shown in  FIG. 7) . 
   Then, the sequence control circuit  10  transfers the accumulated luminances a 1 , a 2 , and a 3  of the non-volatile memories  20   a ,  20   b , and  20   c  to the RGB counters  31   a ,  31   b , and  31   c , respectively (this operation corresponds to step S 30  shown in  FIG. 7 ), before outputting a display-enable signal (f=“H”) and a frame synchronizing signal g (in this exemplary embodiment, a synchronization clock to transfer one pixel data rather than a clock for each frame) to each of the R, G, and B counters  31   a ,  31   b , and  31   c  (this operation corresponds to step S 40  shown in  FIG. 7 ). Then, the sequence control circuit  10  outputs to the driver  50  image data (hereinafter “RGB data”) h 1 , h 2 , and h 3  for Red, Green, and Blue, and also outputs them to the R, G, and B counters  31   a ,  31   b , and  31   c , respectively (this operation corresponds to step S 50  shown in  FIG. 7 ). 
   In a period in which the RGB data h 1 , h 2 , and h 3  are output to the driver  50 , according to the above-noted process, the DAC included in the driver  50  converts the R data h 1 , the G data h 2 , and the B data h 3  into analog data e based on the reference voltage Vref obtained for each of R, G, and B, and supplies the analog data e to the organic EL panel  60 . An image is displayed on the organic EL panel  60 , and the RGB data are counted in each of the R, G, and B counters  31   a ,  31   b , and  31   c . The R, G, and B counters  31   a ,  31   b , and  31   c  add the count values of the R, G, and B data h 1 , h 2 , and h 3  to the previously read R, G, and B accumulated luminances j 1 , j 2 , and j 3  to generate count data k 1 , k 2 , and k 3  for R, G, and B, respectively. 
   The sequence control circuit  10  stops outputting the RGB data h 1 , h 2 , and h 3  so that the organic EL panel  60  is made to enter a non-display state, thus outputting a display-disable signal (f=“L”) to the RGB counter  31 , and also stops outputting the frame synchronizing signal g (this operation corresponds to step S 60  shown in  FIG. 7 ). Thus, counting of the RGB data h 1 , h 2 , and h 3  terminates. Then, the count data k 1 , k 2 , and k 3  for R, G, and B obtained by the RGB counters  31   a ,  31   b , and  31   c , respectively, are written to the non-volatile memory  20  (this operation corresponds to step S 70  shown in  FIG. 7 ). The sequence control circuit  10  outputs a non-volatile memory writing signal b 2 , which is “H”, to the non-volatile memory  20  to enable writing of the count data k 1 , k 2 , and k 3 . The written count data k 1 , k 2 , and k 3  serve as new accumulated luminances j 1 , j 2 , and j 3 . 
   The sequence control circuit  10 , the Red counter  31   a , the Green counter  31   b , the Blue counter  31   c , the output correction tables  40   a , the selectors  40   b , and the DACs  40   c  can be implemented by software or hardware, as required. The driver  50  can be implemented by either a current driving circuit or a voltage driving circuit. 
   The advantage of brightness correction according to the third exemplary embodiment is described below with reference to luminance life characteristic graphs of  FIGS. 8 and 9 . In  FIGS. 8 and 9 , the luminance indicates a luminance of predetermined RGB data which is input to the driver  50 . 
   As depicted in the graph of  FIG. 8 , in a typical organic EL display apparatus which is not subjected to brightness correction, when all R, G, and B pixels are illuminated, the luminance for W (white), G, and B is reduced over time by approximately 50% compared to the early stages of use. In the present exemplary embodiment, however, as depicted in  FIG. 9 , the reduction in brightness can be greatly suppressed. In particular, the luminance for white is reduced only by approximately 20%. The same advantage applies to both the above-described first and second exemplary embodiments. 
   In the foregoing description of Exemplary Embodiments 1 through 3, the reference voltage Vref supplied to the DAC included in the driver is adjusted to adjust the brightness; however, this is merely an example. Various modifications in design may be made, if necessary, including adjustment of the power supply voltage applied to the organic EL devices and modification of data. 
   As an example, as shown in  FIGS. 10(   a ) and  10 ( b ), a drive voltage Voel may be defined according to the accumulated lighting time a. In this case, a select signal c is input to a selector  70   b  of a drive voltage control circuit  70 , and the selector  70   b  refers to an output correction table  70   a  and outputs a signal d to a power supply circuit  70   c  having a DAC function. The drive voltage Voel is defined based on the signal d, and the drive voltage Voel is output from the power supply circuit  70   c  to the organic EL panel  60 . 
   As another example, as shown in  FIGS. 11(   a ) and  11 ( b ), the digital data itself may be modified according to the accumulated lighting time a. In this case, a select signal is input to a selector  80   b  of a data correction circuit  80 , and the selector  80   b  refers to an output correction table  80   a  and outputs a signal d to a digital-to-digital converter DDC  80   c  to define a central value based on which the digital data h is corrected by the DDC  80   c . Digital data h′ obtained by correction in the DDC  80   c  is input to the driver  50  for conversion into analog data e, and the analog data e is supplied to the organic EL panel. 
   In the examples shown in  FIGS. 10(   a )– 11 ( b ), of course, the drive voltage Voel or the digital data h can be adjusted or corrected based on the accumulated luminance, as described above in Exemplary Embodiments 2 and 3. 
   Although the present exemplary embodiment is applied to the reduction in brightness due to the degradation over time, a similar approach can be applied to an increase in brightness due to a change in temperature of the use environment. 
   In a case where there is no need for correction based on the accumulated lighting time from the shipping time of the product or the accumulated luminance, a volatile memory may be substituted for the non-volatile memory. 
   Also, a plurality of corrections may be performed in one-time use. In such a case, in the sequence shown in  FIG. 2  or  5 , a return process from S 70  to S 20  should be performed many times in a predetermined period. 
   The present invention is further applicable to an organic EL device in which light emitted from a common light source for R, G, and B is converted by color conversion layers for R, G, and B to obtain R, G, and B light. In this case, digital data for all R, G, and B may be measured by the RGB counter, or digital data for only one of the R, G, and B may be measured. 
   Some specific examples of the above-described electronic apparatus in which an organic EL display apparatus is used for an electronic device are described below. First, an example in which the organic EL display unit according to this exemplary embodiment is applied to a mobile personal computer is described.  FIG. 12  is a perspective view showing the structure of the mobile personal computer. 
   In  FIG. 12 , a personal computer  1100  includes a main body  1104  having a keyboard  1102 , and a display unit  1106 , and the display unit  1106  includes the above-described organic EL display apparatus. 
     FIG. 13  is a perspective view showing the structure of a cellular phone whose display unit is implemented by the above-described organic EL display apparatus. In  FIG. 13 , a cellular phone  1200  includes a plurality of operation buttons  1202 , an earpiece  1204 , a mouthpiece  1206 , and the above-described electro-optical apparatus  100 . 
     FIG. 14  is a perspective view showing the structure of a digital still camera whose finder is implemented by the above-described organic EL display apparatus  100 . In  FIG. 14 , a connection with an external device is also illustrated in a simple manner. While a typical camera creates an optical image of an object to allow a film to be exposed, a digital still camera  1300  photoelectrically converts an optical image of an object using an imaging device such as a CCD (Charge Coupled Device) to generate an imaging signal. The above-described organic EL display apparatus is placed on a rear surface of a case  1302  of the digital still camera  1300  to perform display based on the imaging signal generated by the CCD, and the organic EL display apparatus functions as a finder for displaying the object. A light-receiving unit  1304  including an optical lens and the CCD is also placed on the viewing side of the case  1302  (in  FIG. 14 , the rear surface). 
   When a photographer views an image of an object displayed on the organic EL display apparatus and presses a shutter button  1306 , the imaging signal of the CCD at this time is transferred and stored in a memory on a circuit board  1308 . In the digital still camera  1300 , a video signal output terminal  1312  and an input/output terminal  1314  for data communication are placed on a side surface of the case  1302 . As shown in  FIG. 14 , a TV monitor  1430  is connected to the former video signal output terminal  1312 , and a personal computer  1430  is connected to the latter input/output terminal  1314  for data communication, if necessary. The imaging signal stored in the memory on the circuit board  1308  is output by a predetermined operation to the TV monitor  1430  or the personal computer  1440 . 
   Examples of electronic devices to which the organic EL display apparatus of the present invention is applicable include, in addition to the personal computer shown in  FIG. 11 , the cellular phone shown in  FIG. 12 , and the digital still camera shown in  FIG. 13 , a television set, a viewfinder-type or direct-view monitor type video tape recorder, a car navigation system, a pager, an electronic organizer, an electronic calculator, a word processor, a workstation, a videophone, a POS terminal, a touch-panel-equipped device, a smart robot, a lighting device having a light control function, and an electronic book, for example. The above-described organic EL display apparatus can be implemented as a display unit of such exemplary electronic devices. 
   The amount of drive current to be supplied to electro-optical devices is controlled, thus enabling a change in brightness to be compensated for.