1. Field of the Invention
The present invention relates to display devices, such as organic electroluminescence display devices, which include a display panel comprising an arrangement of a plurality of pixels.
2. Description of Related Art
Progress has been made in developing organic electroluminescence displays (hereinafter referred to as “organic LED displays”) in recent years. Use of organic LED displays, for example, in portable telephones is under study.
The methods of driving such organic LED displays include the passive matrix driving method wherein the scanning electrodes and the data electrodes are used for time division driving, and the active matrix driving method wherein each pixel is held luminescent for one vertical scanning period. Furthermore, the methods of driving the organic LED display devices of the active matrix driving method include the display devices of the analog drive type wherein current of a magnitude corresponding to the data voltage is supplied to an organic EL element to turn on the EL element with a brightness corresponding to the data voltage, and the display devices of the digital drive type in which a multi-level gradation is produced by supplying to an organic EL element a pulse current having a duty ratio in accordance with the data voltage (e.g., JP-A No.312173/1998).
The present applicants have proposed the organic LED display devices of the digital drive type having a display panel comprising an arrangement of pixels 31 having a circuit structure shown in
With the organic LED display device, one field period is divided into a first half scanning period and a second half luminescence period as shown in
However, the organic LED display device described has the problem that the organic EL characteristics are shifted due to change with temperature and time of the organic EL element, as shown in
Incidentally, a light emission device is proposed for obtaining a constant luminance, which the device corrects the voltage for a pixel portion so that a drive current to be passed through a light emission element for the entire pixel portion is a reference value calculated from data of a video signal (JP-A No.311898/2002).
An object of the present invention is to provide a display device which is adapted to produce a constant luminance despite change with temperature and time of a display element, such as an organic EL element.
The present invention provides a first display device comprising a display panel having an arrangement of a plurality of pixels and a control unit for supplying data voltage or data current corresponding to a video signal fed from the outside to each pixel of the display panel, each pixel of the display panel comprising a display element operable to luminesce when supplied with current and drive means for supplying to the display element a drive current corresponding to the data voltage or the data current from the control unit. The control unit comprises:
deriving means for deriving the sum of currents to be passed through each pixel of the display panel based on values of the video signals for each pixel of the display panel,
current measuring means for measuring the total quantity of currents to have been passed through the pixels of the display panel, and
calculation processing means for correcting the video signals for each pixel of the display panel based on a derived value obtained by the deriving means and a measurement value obtained by the current measuring means.
With the first display device of the present invention, the calculation processing means corrects the video signals for each pixel. At this time, current variations due to change with temperature and time of the display element can be indicated by the difference between the sum of currents theoretically derived by the deriving means based on the value of the video data and the total quantity of currents actually measured by the current measuring means. Accordingly the video signals are corrected by the calculation processing means in accordance with the change with temperature and time. Thus the video signals are corrected for each pixel in accordance with the change with temperature and time, the data voltage or the data current corresponding to the corrected video signal is fed to each pixel, and the drive current corresponding to the data voltage or the data current is fed to the display element. Consequently the display element luminesces with a constant luminance despite the change with temperature and time.
Stated specifically, the deriving means comprises accumulating means for accumulating the values of the video signals for each pixel of the display panel, and conversion means for converting an accumulated value obtained by the accumulating means into the sum of currents to be passed through each pixel of the display panel. The calculation processing means corrects the video signals based on the conversion value obtained by the conversion means and the measurement value obtained by the current measuring means. The calculation processing means comprises correction coefficient calculating means for calculating a correction coefficient based on the conversion value and the measurement value and correcting means for correcting the video signals with use of the calculated correction coefficient.
Stated specifically, the correcting means varies the calculated correction coefficient depending on a position of the pixel.
The display element is more prone to temperature increase in a central portion of a display area of the display panel than in a peripheral portion, and is more rapidly deteriorated thereof. Therefore current variations due to the change with temperature and time of the display element in the central portion are greater than in the peripheral portion. The correcting means varies the correction quantity by varying the correction coefficient depending on a position of the pixel, whereby a suitable correction in accordance with the change with temperature and time can be made to the video signals despite the position of the pixel.
According to another specific construction, a display area of the display panel can be divided into a plurality of areas. The correction coefficient can be calculated for each of the areas. The plurality of areas are each set to a correction coefficient calculating area one after another. The control unit comprises video signal setting means for performing an operation for setting the values of the video signals for the pixels in areas except the correction coefficient calculating area to a predetermined value such that the magnitude of the drive current to be fed to the display elements of the pixels is zero. When the video signal setting means performs a setting operation, the accumulating means performs the accumulating operation, and the current measuring means performs the measuring operation. Then the correction coefficient calculating means of the calculation processing means calculates the correction coefficient for each of the areas. The correcting means corrects the video signals for the pixels in each of the areas with use of the correction coefficient for each of the areas.
According to the specific construction, the display area of the display panel is divided into the plurality of areas, and the correction coefficient is calculated for each of the areas. First, one area out of the plurality of areas is set to the correction coefficient calculating area. The values of the video signals for the pixels in areas except the correction coefficient calculating area are set to a predetermined value such that the magnitude of the drive current to be fed to the display elements of the pixels is zero, which predetermined value is zero, for example. As a result, the drive current is fed to the display elements of the pixels only in the correction coefficient calculating area to display the video image only in the correction coefficient calculating area. At this time, the accumulating means performs the accumulating operation, and thereafter the conversion means performs a conversion operation, to obtain the sum of currents to be passed through each pixel in the correction coefficient calculating area. Furthermore, the current measuring means performs the measurement operation, to obtain the total quantity of currents to have been passed through the pixels in the correction coefficient calculating area. The current variations due to the change with temperature and time of the pixels arranged in the correction coefficient calculating area can be indicated by the difference between the conversion value obtained by the conversion means and the measurement value obtained by the current measuring means, as described above. The correction coefficient calculating means calculates the correction coefficient for the area based on the conversion value and the measurement value. As in the same manner, the correction coefficients for other areas are each calculated one after another. The correction coefficient for each of the areas is thus calculated, and the video signals for the pixels in each of the areas are corrected with the correction coefficient for each of the areas. According to the specific construction, the suitable correction in accordance with the change with temperature and time can be made to the video signals despite the position of the pixel.
Stated further specifically, the correction coefficient can be calculated for each color of the three primary colors. The three primary colors are each set to a correction coefficient calculating color one after another. The video signal setting means sets to said predetermined value the values of the video signals for the pixels of the two colors except the correction coefficient calculating color, among the pixels in the correction coefficient calculating area. The correction coefficient calculating means of the calculation processing means calculates the correction coefficient for each color. The correcting means corrects the video signals for each color pixel with use of the correction coefficient for each color.
According to the construction described, the correction coefficient is calculated for each of the areas and for each color of the three primary colors. As described above, the values of the video signals for the pixels in the areas except the correction coefficient calculating area are set to said predetermined value. One of the three primary colors is set to the correction coefficient calculating color. The values of the video signals for the pixels except the pixels of the correction coefficient calculating color and among the pixels in the correction coefficient calculating area are set to said predetermined value. As a result, the drive current is fed to the display elements of the pixels of the correction coefficient calculating color and among the pixels in the correction coefficient calculating area to display the video image only in said area only with said pixels of said color. At this time the accumulating means performs an accumulating operation, and thereafter the conversion means performs a conversion operation, to obtain the sum of currents to be passed through each pixel of the correction coefficient calculating color and among the pixels in the correction coefficient calculating area. The current measuring means further performs a measurement operation to obtain the total quantity of currents to have been passed through the pixels of the correction coefficient calculating color among the pixels in the correction coefficient calculating area. Incidentally the current variations due to the change with temperature and time of the pixels of the correction coefficient calculating color and among the pixels in the correction coefficient calculating area can be indicated by the difference between the conversion value obtained by the conversion means and the measurement value obtained by the current measuring means, as described above. Thus the correction coefficient calculating means calculates the correction coefficient for said color based on the conversion value and the measurement value. As in the same manner, the correction coefficients for the other two colors are each calculated one after another. Thus the correction coefficient for each color in each of the areas is calculated to correct the video signals for each color pixel in each of the areas with use of each correction coefficient.
Stated further specifically, the control unit comprises relationship means for defining for each color the relationships between the accumulated value of the video signals and the sum of currents. The conversion means converts the accumulated value of the video signals into the sum of currents according to the relationship for the correction coefficient calculating color and among the relationships defined in the relationship means.
According to the specific construction described, the accumulated value of the video signals is converted into the sum of currents according to the relationship for the correction coefficient calculating color and among the three relationships defined in the relationship means, so that an accurate conversion value in accordance with luminous efficiency of the pixels of said color can be obtained. Therefore a suitable correction in accordance with the change with temperature and time can be made to the video signals despite the color of the pixel.
According to another specific construction, a display area of the display panel is divided into a plurality of areas, and the correction coefficient can be calculated for each of the areas. The plurality of areas are each set to the correction coefficient calculating area one after another. The control unit comprises video signal setting means for performing an operation for setting the values of the video signals for the pixels in said area to a value such that the magnitude of the drive current to be fed to the display elements of said pixels is zero or a given predetermined value. When the video signal setting means performs a setting operation or ceases a setting operation, the accumulating means performs the accumulation operation while the current measuring means performs the measurement operation. The calculation processing means further comprises:
first subtraction means for subtracting a conversion value obtained when the video signal setting means performs a setting operation from a conversion value obtained when the video signal setting means ceases a setting operation, and
second subtraction means for subtracting a measurement value obtained when the video signal setting means performs a setting operation from a measurement value obtained when the video signal setting means ceases a setting operation. The correction coefficient calculating means calculates a correction coefficient for each of the areas based on the subtraction result obtained by the first subtraction means and the subtraction result obtained by the second subtraction means. The correcting means corrects the videos signals for the pixels in each of the areas with use of the correction coefficient for each of the areas.
According to the specific construction, the display area of the display panel is divided into a plurality of areas, and the correction coefficient is calculated for each of the areas. First, one area among the plurality of areas is set to the correction coefficient calculating area. The values of the video signals for the pixels in said area are set to a value such that the magnitude of the drive current to be fed to the display elements of said pixels is zero, for example. As a result, the drive current is fed to the display elements of the pixels arranged in the areas except the correction coefficient calculating area, to display the video image in the areas except the correction coefficient calculating area. At this time, the accumulating means performs an accumulating operation, and thereafter the conversion means performs a conversion operation to obtain the sum of currents to be passed through each pixel in the areas except the correction coefficient calculating area. Furthermore, the current measuring means performs a measurement operation to obtain the total quantity of currents to have been passed through the pixels in the areas except the correction coefficient calculating area.
Furthermore, when the video signal setting means ceases the setting operation described, the accumulating means performs an accumulating operation, and thereafter the conversion means performs a conversion operation to obtain the sum of currents to be passed through each pixel in all of the areas of the display panel. Further, the current measuring means performs a measurement operation to obtain the quantity of currents to have been passed through the pixels in all of the areas of the display panel.
The sum of currents to be passed through each pixel in the correction coefficient calculating area can be indicated by the difference between the conversion value obtained when the video signal setting means ceases a setting operation and the conversion value when performs a setting operation as described above. Further the total quantity of currents to have been passed through the pixels in the correction coefficient calculating area can be indicated by the difference between the measurement value obtained when the video signal setting means ceases a setting operation and the measurement value obtained when performs a setting operation as described above. The first subtraction means calculates the sum of currents to be passed through each pixel in the correction coefficient calculating area. The second subtraction means calculates the total quantity of currents to have been passed through the pixels in the correction coefficient calculating area. In this case, the current variations due to the change with temperature and time of the pixels arranged in the correction coefficient calculating area can be indicated by the difference between the subtraction result obtained by the first subtraction means and the subtraction result obtained by the second subtraction means. Thus the correction coefficient calculating means calculates the correction coefficient for said area based on the subtraction results. As in the same manner, the correction coefficients for the other areas are each calculated one after another. The correction coefficient for each of the areas is thus calculated to correct the video signals for the pixels in each of the areas with use of the correction coefficient for each of the areas. According to the specific construction described, a suitable correction in accordance with the change with temperature and time can be made to the video signals despite the position of the pixel.
Further stated specifically, the correction coefficient can be calculated for each color of the three primary colors. The three primary colors are each set to the correction coefficient calculating color one after another. The video signal setting means sets the values of the video signals for the pixels of said color and among pixels in the correction coefficient calculating area to a value such that the magnitude of the drive current to be fed to the display element of said pixels is zero or a given predetermined value. The correction coefficient calculating means of the calculation processing means calculates a correction coefficient for each color. The correcting means corrects the video signals for each color pixel with use of the correction coefficient for each color.
According to the specific construction, the correction coefficient is calculated for each of the areas and for each color of the three primary colors. Owing to a subtraction operation of the first subtraction means, the sum of currents to be passed through each pixel of the correction coefficient calculating color and among the pixels in the correction coefficient calculating area. Furthermore, owing to a subtraction operation of the second subtraction means, the total quantity of currents to have been passed through the pixels of the correction coefficient calculating color and among the pixels in the correction coefficient calculating area. In this case the current variations due to the change with temperature and time of the pixels of the correction coefficient calculating color and among the pixels in the correction coefficient area can be indicated by the difference between the subtraction result obtained by the first subtracting means and the subtraction result obtained by the second subtracting means. The correction coefficient calculating means calculates the correction coefficient for said color based on the subtraction results.
Stated further specifically, the control unit comprises relationship means for defining for each color the relationships between the accumulated value of the video signals and the sum of currents. The accumulating means accumulates, for each color, the values of the video signals. The conversion means converts, for each color, the accumulated value of the video signals into the sum of currents according to the relationships defined in the relationship means.
According to the specific construction described, the accumulated value of the video signals is converted, for each color, into the sum of currents according to the relationship defined in the relationship means, so that an accurate conversion value can be obtained for each color in accordance with luminous efficiency of the pixel. Therefore, a suitable correction in accordance with the change with temperature and time can be made to the video signals despite the color of the pixel.
Still further specifically, the video signal setting means performs the setting operation at a longer cycle than a frame cycle of the video signal.
Because the change with temperature and time of the display element is slow, a new correction coefficient need not be calculated at the same cycle as the frame cycle of the video signal. The suitable correction in accordance with the change with temperature and time can be made to the video signals by the use of the correction coefficient calculated at a longer cycle than the frame cycle. According to the specific construction described, the cycle of the setting operation of the video signal setting means is set to the cycle described. This can suppress a flicker in the screen.
The present invention provides a second display device comprising a display panel having an arrangement of a plurality of pixels and a control unit for supplying data voltage or data current corresponding to a video signal fed from the outside to each pixel of the display panel, each pixel of the display panel comprising a display element operable to luminesce when supplied with current and drive means for supplying to the display element drive current corresponding to the data voltage or the data current from the control unit. The control unit comprises:
deriving means for deriving the sum of currents to be passed through each pixel of the display panel based on values of the video signals for each pixel of the display panel,
current measuring means for measuring the total quantity of currents to have been passed through pixels of the display panel,
control means for preparing and outputting a control signal based on a derived value obtained by the deriving means and a measurement value obtained by the current measuring means, and
data voltage/current supplying means for changing the relationship between the video signal and the data voltage or the data current according to the control signal output from the control unit, and supplying to each pixel of the display panel the data voltage or the data current corresponding to the video signal from the outside based on the changed relationship.
With the second display device of the present invention, the control means prepares the control signal for the data voltage/current supplying means. Current variations due to the change with temperature and time of the display element can be indicated by the difference between the sum of currents theoretically derived by the deriving means from the value of the video signal, and the quantity of currents actually measured by the current measuring means. Accordingly the control means prepares the control signal in accordance with the change with temperature and time. The control signal thus prepared is supplied to the data voltage/current supplying means, to change the relationship between the video signal and the data voltage or data current, supplying to each pixel the data voltage or the data current corresponding to the video signal in accordance with the changed relationship, to supply to the display element the drive current corresponding to said data voltage or said data current. Consequently, the display element luminesces with a constant luminance despite the change with temperature and time.
As stated above, with the first and the second display devices of the present invention, a constant luminance can be achieved despite the change with temperature and time of the display element.
a) and
a) to (c) are diagrams showing another example of screens displayed on the organic LED display for the calculation of the correction gain;
With reference to the drawings, the present invention will be described below as embodied into organic LED display devices based on two embodiments.
The organic LED display device of the present embodiment is adapted to divide a display area of the organic LED display 3 into a plurality of areas as indicated in a broken line in
First, among input data of one frame, the video data for the pixels in the areas except a first area and the video data for the pixels of G and B in the first area are each changed to the value of zero, with the result that currents are passed only through the pixels of R among pixels arranged in the first area of the organic LED display 3 to display video image only in the first area only with the pixels of R, as shown in
Current flowing to a connector (not shown) through each pixel of the organic LED display 3 shown in
Furthermore, the video data of RGB having a value changed by the comparing/calculating unit 1 as described above is fed to a video signal accumulator 6. The video data of RGB is fed to an R video accumulator 61, G video accumulator 63, and B video accumulator 65, respectively, as shown in
Current variations due to change with temperature and time of the organic EL element can be indicated by the difference between total quantity of currents actually measured by the current monitor unit 4 and the sum of currents theoretically derived by the video signal accumulator 6 based on the accumulated value of the video data, as described above. In the comparing/calculating unit 1, the conversion result B of the video signal accumulator 6 is divided by the calculation result A of the current monitor unit 4 to thereby calculate a correction gain (B/A). Thereafter the input data is multiplied by the correction gain to thereby make a correction to the input data.
For example, when the organic EL element rises in temperature, the calculation result A of the current monitor unit 4 exceeds the conversion result B of the video accumulator 6 as shown in
Accordingly the input data is corrected in accordance with the change with temperature and time of the organic EL element to feed the corrected data to the drive IC 2. Thus the data voltage corresponding to the data is fed to the pixels of the organic LED display 3, to feed the drive current corresponding to the data voltage to the organic EL elements. Consequently the organic EL element luminesces with a constant luminance despite the change with temperature and time.
The correction gain described is calculated when the frame video images as shown in
With the organic LED display device of the present embodiment, as described above, the video data for each pixel is corrected in accordance with the change with temperature and time of the organic EL element to thereby achieve a constant luminance despite the change with temperature and time.
Whereas the display area of the organic LED display 3 is divided into a plurality of areas to calculate the correction gain for each color in each area in the embodiment described above, it is also possible to calculate the correction gain for each color not by dividing the display area of the organic LED display 3 into a plurality of areas.
Furthermore, the construction to be described below is also available: the correction gain (B/A) for each color is calculated not by dividing the display area of the organic LED display 3 into a plurality of areas, the video data for the pixels in a central portion which have a great temperature change is multiplied by the correction gain (B/A) while the video data for the pixels in a peripheral portion which have a small temperature change is multiplied by a new correction gain obtained by multiplying the correction gain (B/A) by a coefficient α (α>1) as shown in
Furthermore, when the sum of currents to be passed through each pixel is to be derived based on the accumulated value of the video data, taking into account of the voltage drop due to the wiring resistance generates a derived value with high accuracy.
Further, the correction gain can be varied smoothly in the vicinity of the boundary of two adjacent areas by weighting the correction gain calculated for each area with use of a weighted coefficient. This prevents the occurrence of luminance difference in the boundary between two adjacent areas.
Furthermore, whereas the present invention is embodied into the organic LED display device wherein the data voltage is fed from the drive IC 2 to the organic LED display 3 according to the embodiment described above, the invention can also be embodied into an organic LED display device wherein the data current is fed thereof.
Furthermore, according to the embodiment described above, when, for example, the correction gain for the pixels of R in the first area is to be calculated, video image is displayed only in the first area only with the pixels of R as shown in
With the organic LED display device of the first embodiment, the video data is corrected corresponding to the change with temperature and time. With the organic LED display device of the present embodiment, the relationship between the video data and the data voltage is changed.
With the organic LED display device of the present embodiment, the comparing/calculating unit 10 performs a data changing operation to be described below for preparing a control signal for the drive IC 20.
First, among input data of one frame, data for the pixels of G and B is changed to the value of zero, with the result that current is passed only through the pixels of R of the organic LED display 3 to display video image only with the pixels of R. Subsequently among input data of one frame, data for the pixels of R and B is changed to the value of zero, with the result that current is passed only through the pixel of G of the organic LED display 3 to display video image only with the pixel of G. Subsequently among input data of one frame, the video data for the pixels of R and G is changed to the value of zero, with the result that current is passed only through the pixel of B of the organic LED display 3 to display video image only with the pixels of B. Thereafter video image is displayed only with the pixels of R again. Accordingly the video image is repeatedly displayed with each pixel of RGB. Frame cycle of the video signal is set, for example, to 1/60 second. The comparing/calculating unit 10 performs the data changing operation described at a cycle of one second which is longer than the frame cycle.
Current flowing to a connector (not shown) through each pixel of the organic LED display 3 is fed to a current monitor unit 4 housing A/D converter (not shown). The sum of currents to have been passed through each pixel is calculated in the current monitor unit 4, and the calculation result is fed to the comparing/calculating unit 10.
Furthermore, the video data of RGB output from the comparing/calculating unit 10 as described above is fed to a video signal accumulator 60. The video data of RGB is fed to an R video accumulator 67, G video accumulator 68, and B video accumulator 69, respectively, as shown in
Current variations due to change with temperature and time of the organic EL element can be indicated by the difference between total quantity of currents actually measured by the current monitor unit 4 and the sum of currents theoretically derived by the video signal accumulator 60 from the accumulated value of the video data, as described above.
In the comparing/calculating unit 10, the conversion result B of the video signal accumulator 60 is divided by the calculation result A of the current monitor unit 4 to thereby calculate a coefficient (B/A). Thereafter a reference voltage Re at that time, i.e., a data voltage when the value of the video data is the maximum value 255, is multiplied by the coefficient to obtain a value [Re·(B/A)]. Then a control signal to the effect that the value [Re·(B/A)] thus obtained is a new reference voltage is prepared and fed to the drive IC 20.
The drive IC 20 comprises a D/A conversion circuit 21 for each of the RGB three primary colors and having a construction shown in
Accordingly, the relationship between the video data and the data voltage is changed in accordance with change with temperature and time. The data voltage corresponding to the video data in accordance with the changed relationship is applied to the pixels of the organic LED display to feed a drive current corresponding to the data voltage to the organic EL element. Thus the organic EL element luminesces with a constant luminance despite the change with temperature and time.
For example, when the organic EL element rises in temperature, the calculation result A of the current monitor unit 4 exceeds the conversion result B of the video accumulator 60 as shown in
The above-mentioned control signal fed to the drive IC 20 is prepared when the video image is displayed on the organic LED display 3 only with the pixels of R, when the video image is displayed on the organic LED display 3 only with the pixels of G, and when the video image is displayed on the organic LED display 3 only with the pixels of B. When the video image is displayed on the organic LED display 3 only with the pixels of R, the sum of currents to be passed through each pixel of R is obtained from the video signal accumulator 60, and the sum of currents to have been passed through each pixel of R is obtained from the current monitor unit 4. In this case current variations due to the change with temperature and time of the pixels of R can be indicated by the difference between the value obtained from the current monitor unit 4 and the value obtained from the video signal accumulator 60, as described above. Accordingly in the comparing/calculating unit 10, a value to be set as the reference voltage for the pixels of R is calculated, and a control signal to the effect that the calculated value is a new reference voltage for the pixels of R is prepared. Thereafter when the video image is displayed on the organic LED display 3 only with the pixels of G, a value to be set as the reference voltage for the pixels of G is calculated, and a control signal to the effect that the calculated value is a new reference voltage for the pixels of G is prepared. Furthermore when the video image is displayed on the organic LED display 3 only with the pixels of B, a value to be set as the reference voltage for the pixels of B is calculated, and a control signal to the effect that the calculated value is a new reference voltage for the pixels of B is prepared. The control signals for each color which are thus obtained are fed to the drive IC 21 to change the reference voltages for each color.
With the organic LED display device of the present embodiment, as described above, the reference voltage is changed in accordance with the change with temperature and time of the organic EL element to thereby achieve a constant luminance despite the change with temperature and time.
According to the embodiment described, as shown in
Further according to the embodiment described, the present invention is embodied into the organic LED display device for feeding the data voltage from the drive IC 20 to the organic LED display 3. However, the invention can also be embodied into the organic LED display device for feeding the data current thereof. In this case, in the drive IC 20, the relationship between the video data and the data current is changed depending on the change with temperature and time of the organic EL element.
Still furthermore, according to the above embodiment, when, for example, a control signal for the pixels of R is to be prepared, video image is displayed on the organic LED display 3 only with the pixels of R to calculate the sum A of currents to have been passed through each pixel of R and to derive the sum B of currents to be passed through each pixel of R based on the accumulated value of the video data. It is also possible to obtain these values A, B with a method to be described below. That is, when the video image is displayed on the organic LED display 3 with the RGB pixels, the sum A0 of currents to have been passed through each pixel of RGB is calculated, and the sum B0 of currents to be passed through each pixel of RGB is derived based on the accumulated value of the video data. Thereafter, the video data for the pixels of R is changed to the value of zero to thereby display the video image with the pixels of G and B, to calculate the sum A1 of currents to have been passed through each pixel of G and B, and to derive the sum B1 of currents to be passed through each pixel of G and B based on the accumulated value of the video data. Thereafter the sum A1 of currents to have been passed through each pixel of G and B is subtracted from the sum A0 of currents to have been passed through each pixel of RGB. Thus obtained is the sum A (A=A0−A1) of currents to have been passed through each pixel of R when the video image is displayed with the RGB pixels. Furthermore, the sum B1 of currents to be passed through each pixel of G and B is subtracted from the sum B0 of the currents to be passed through each pixel of RGB. Thus obtained is the sum B (B=B0−B1) of currents to be passed through each pixel of R when the video image is displayed with the RGB pixels. According to the specific construction described, for example, in the preparation of the control signal for the pixels of R, the video data for the pixels of R is changed to the value of zero, but it is also possible to use the arrangement wherein the video data is changed to a given predetermined value.
Furthermore, according to the First and Second embodiments, the present invention is embodied into the organic LED display device, but can be embodied into known various display devices which comprise a display element wherein the passage of current is changed due to the temperature change and the deterioration with time and which is adapted to measure a current to be passed through the display element.
Number | Date | Country | Kind |
---|---|---|---|
2003-338897 | Sep 2003 | JP | national |
Number | Name | Date | Kind |
---|---|---|---|
6710548 | Kimura | Mar 2004 | B2 |
6911781 | Yamazaki et al. | Jun 2005 | B2 |
7088052 | Kimura | Aug 2006 | B2 |
7218297 | Inukai et al. | May 2007 | B2 |
Number | Date | Country |
---|---|---|
10-312173 | Nov 1998 | JP |
2002-311898 | Oct 2002 | JP |
Number | Date | Country | |
---|---|---|---|
20050110786 A1 | May 2005 | US |