Display device

A display device includes: a display panel including a display region in which display pixels are two-dimensionally arranged, and a non-display region in which first dummy pixels and second dummy pixels are arranged; a first drive section allowing each of the first dummy pixels to emit light by applying signal voltages having different magnitudes to each of the first dummy pixels; a second drive section allowing each of the second dummy pixels to emit light by flowing constant currents having different magnitudes to each of the second dummy pixels; a current measurement section detection currents flowing through each of the first dummy pixels to output current information thereof; a light reception section detecting light emitted from each of the second dummy pixels to output luminance information thereof; and a calculation section deriving a current deterioration function using the current information, and deriving an efficiency deterioration function using the luminance information.

BACKGROUND OF THE PRESENT INVENTION

1. Field of the Present Invention

The present invention relates to a display device in which a light emitting element is provided in a display panel.

2. Description of the Related Art

In recent years, in the field of a display device displaying an image, a display device using, as a light emitting element of a pixel, a current drive type optical element, for example, an organic EL (electro luminescence) element, in which light emission luminance is varied according to the value of a flowing current has been developed, and progressively commercialized. Unlike a liquid crystal element or the like, the organic EL element is a self-luminous element. Thus, in a display device using the organic EL element (organic EL display device), since a light source (backlight) is not necessary, thinning and high luminance are realized in comparison with a liquid crystal display device in which the light source is necessary. In particular, in the case where the active matrix method is used as a driving method, it may be possible to light and hold each pixel, and this enables low power consumption. Therefore, the organic EL display device is expected to become the mainstream of a flat panel display in the next generation.

However, in the organic EL element, an element is deteriorated in accordance with the amount of a flowing current, and there is an issue that the luminance is reduced. Thus, in the case where the organic EL element is used as a pixel in the display device, the state of deterioration may be varied for each pixel. For example, in the case where information such as a time and a display channel is displayed with a high luminance in the same place for a long time, deterioration of only the pixels in that section is accelerated. As a result, in the case where a video having a high luminance is displayed in the section including the pixels whose deterioration is accelerated, a phenomenon called “seizure” is generated such that only the section of the pixels whose deterioration is accelerated is darkly displayed. Since the seizure is irreversible, when the seizure is once generated, it is not eliminated.

A great number of methods for preventing the seizure have been proposed so far. For example, in Japanese Unexamined Patent Publication No. 2002-351403, the method in which a dummy pixel is provided in a region other than a display region, and the deterioration degree of the dummy pixel is estimated by detecting a terminal voltage when the dummy pixel emits light, thereby correcting a video signal by utilizing that estimation is disclosed. Further, for example, in Japanese Unexamined Patent Publication No. 2008-58446 and International Publication WO 2006/046196, the methods in which an optical sensor is disposed in each display pixel, and a video signal is corrected by utilizing a light reception signal output from the optical sensor are disclosed.

SUMMARY OF THE PRESENT INVENTION

However, in the method of Japanese Unexamined Patent Publication No. 2002-351403, since the deterioration degree of the pixel is not estimated based on light emission information of a pixel in the display region, and it is difficult to accurately correct the video signal, there is an issue that the seizure is difficult to be prevented. Further, in the methods of Japanese Unexamined Patent Publication No. 2008-58446 and International Publication WO 2006/046196, since the photoelectric conversion efficiency of the optical sensor in each pixel is varied, for example, the intensity of the light reception signal may be varied in two pixels performing a display with the same luminance. As a result, there is an issue that it is difficult to accurately prevent the seizure.

In view of the foregoing, it is desirable to provide a display device capable of accurately preventing a seizure.

According to an embodiment of the present invention, there is provided a display device including: a display panel including a display region in which a plurality of display pixels are two-dimensionally arranged, and a non-display region in which a plurality of first dummy pixels and a plurality of second dummy pixels are arranged. Also, the display device includes a first drive section allowing each of the first dummy pixels to emit light by applying signal voltages having magnitudes different from each other to each of the first dummy pixels; and a second drive section allowing each of the second dummy pixels to emit light by flowing constant currents having magnitudes different from each other to each of the second dummy pixels. Further, the display device includes a current measurement section outputting current information of each of the first dummy pixels by detecting currents flowing through each of the first dummy pixels; a light reception section outputting luminance information of each of the second dummy pixels by detecting light emitted from each of the second dummy pixels; and a calculation section deriving a current deterioration function by using the current information, and deriving an efficiency deterioration function by using the luminance information.

In the display device according to the embodiment of the present invention, the signal voltages having the magnitudes different from each other are applied to each of the first dummy pixels provided in the non-display region of the display panel, each of the first dummy pixels emits the light with the luminance in accordance with the magnitude of the signal voltage, the currents flowing through each of the first dummy pixels are detected by the current measurement section, and the current information of each of the first dummy pixels is output from the current measurement section. Further, constant currents having the magnitudes different from each other are flown to each of the second dummy pixels provided in the non-display region of the display panel, each of the second dummy pixels emits light with luminance in accordance with the magnitude of the constant currents, the light emitted from each of the second dummy pixels is detected by the light reception section, and the luminance information of each of the second dummy pixels is output from the light reception section. Thereafter, the current deterioration function is derived by using the current information, and the efficiency deterioration function is derived by using the luminance information. Thereby, for example, from the current deterioration function, and a history of the video signal of each of the display pixels, the current deterioration ratio of each of the display pixels may be predicted. Further, from the efficiency deterioration function, and the history of the video signal of each of the display pixels, the efficiency deterioration ratio of each of the display pixels may be predicted.

Here, in the display device according to the embodiment of the present invention, a cycle in which the current deterioration function is derived is preferably set to be shorter than a cycle in which the efficiency deterioration function is derived. In this case, it may be possible to correct the efficiency deterioration in the state where the current is corrected.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. The description will be made in the following order.1. Embodiment (FIGS. 1 to 24)2. Modifications (no illustrations)Example where each dummy pixel16in which an initial current Siis low is composed of a plurality of dummy pixelsExample where each dummy pixel18in which an initial luminance Yiis low is composed of a plurality of dummy pixelsExample where another dummy pixel16is newly set as a reference pixel, in the case where a failure occurs in a reference pixelExample where another dummy pixel ˜is newly set as the reference pixel, in the case where a failure occurs in the reference pixelExample where a sampling period ΔT1is set to be variableExample where a sampling period ΔT2is set to be variableExample where a power coefficient n (Si, Ss) is derived only with four arithmetic operationsExample where a power coefficient n (Yi, Ys) is derived only with the four arithmetic operations3. Application examples (FIGS. 25 to 29)
1. Embodiment

(Schematic Structure of Display Device1)

FIG. 1illustrates the schematic structure of a display device1according to an embodiment of the present invention. The display device1includes a display panel10, and a drive circuit20driving the display panel10.

The display panel10includes a display region12in which a plurality of organic EL elements11R,11G, and11B are two-dimensionally arranged. In this embodiment, the three organic EL elements11R,11G, and11B adjacent to each other constitute one pixel (display pixel13). Hereinafter, “organic EL element11” is appropriately used as a general term for the organic EL elements11R,11G, and11B. The display panel10also includes a non-display region15in which a plurality of organic EL elements14R,14G, and14B are two-dimensionally arranged. In this embodiment, the three organic EL elements14R,14G, and14B adjacent to each other constitute one pixel (dummy pixel16). Hereinafter “organic EL element14” is appropriately used as a general term for the organic EL elements14R,14G, and14B.

In the non-display region15, further, a plurality of organic EL elements17R,17G, and17B are two-dimensionally arranged. In this embodiment, the three organic EL elements17R,17G, and17B adjacent to each other constitute one pixel (dummy pixel18). Hereinafter, “organic EL element17” is appropriately used as a general term for the organic EL elements17R,17G, and17B. In the non-display region15, a light receiving element group19(light reception section) receiving light which is emitted from the organic EL elements17R,17G, and17B is provided. Although not illustrated in the figure, the light receiving element group19is, for example, composed of a plurality of light receiving elements. The plurality of light receiving elements are, for example, two-dimensionally arranged, while being paired with the individual organic EL elements17. Each light emitting element detects light (emitted light) emitted from each dummy pixel18(each organic EL element17), and outputs a light reception signal19A (luminance information) of each dummy pixel18. Each light receiving element is, for example, a photodiode.

The drive circuit20includes a timing generation circuit21, a video signal processing circuit22, a signal line drive circuit23, a scanning line drive circuit24, a dummy pixel drive circuit25, a current measurement circuit26, a measurement signal processing circuit27, and a storage circuit28.

FIG. 2illustrates an example of a circuit structure in the display region12. In the display region12, a plurality of pixel circuits31are two-dimensionally arranged, while being paired with the individual organic EL elements11. Each pixel circuit31is, for example, composed of a drive transistor Tr1, a write transistor Tr2, and a retention capacity Cs, and has the circuit structure of 2Tr1C. The drive transistor Tr1and the write transistor Tr2are, for example, formed of an n-channel MOS thin film transistor (TFT). The drive transistor Tr1or the write transistor Tr2may be a p-channel MOS TFT.

In the display region12, a plurality of signal lines DTL are arranged in the column direction, and a plurality of scanning lines WSL and a plurality of power source lines Vcc are arranged in the row direction, respectively. In the vicinity of each intersection of each signal line DTL and each scanning line WSL, one of the organic EL elements11R,11G, and11B (sub-pixel) is provided. Each signal line DTL is connected to an output terminal (not illustrated in the figure) of the signal line drive circuit23, and a drain electrode (not illustrated in the figure) of the write transistor Tr2. Each scanning line WSL is connected to an output terminal (not illustrated in the figure) of the scanning line drive circuit24, and a gate electrode (not illustrated in the figure) of the write transistor Tr2. Each power source line Vcc is connected to an output terminal (not illustrated in the figure) of a power source, and a drain electrode (not illustrated in the figure) of the drive transistor Tr1. A source electrode (not illustrated in the figure) of the write transistor Tr2is connected to a gate electrode (not illustrated in the figure) of the drive transistor Tr1, and one end of the retention capacity C. A source electrode (not illustrated in the figure) of the drive transistor Tr1, and the other end of the retention capacity Csare connected to an anode electrode (not illustrate in the figure) of the organic EL element11. A cathode electrode (not illustrated in the figure) of the organic EL element11is, for example, connected to a ground line GND.

FIG. 3illustrates an example of the circuit structure in the non-display region15. In the non-display region15, a plurality of pixel circuits32having the same structure as the pixel circuits31are two-dimensionally arranged, while being paired with the individual organic EL elements14. Each pixel circuit32is, for example, composed of a drive transistor Tr1′, a write transistor Tr2′, and a retention capacity Cs′, and has the circuit structure of 2Tr1C. The drive transistor Tr1′ and the write transistor Tr2′ are, for example, formed of an n-channel MOS TFT. The drive transistor Tr1′ or the write transistor Tr2′ may be a p-channel MOS TFT.

Also in the non-display region15, a plurality of signal lines DTL′ are arranged in the column direction, and a plurality of scanning lines WSL′ and a plurality of power source lines Vcc′ are arranged in the row direction, respectively. In the vicinity of each intersection of each signal line DTL′ and each scanning line WSL′, one of the organic EL elements14R,14G, and14B (sub-pixel) is provided. Each signal line DTL′ is connected to an output terminal (not illustrated in the figure) of a dummy pixel drive circuit25, and a drain electrode (not illustrated in the figure) of the write transistor Tr2′. Each scanning line WSL′ is connected to an output terminal (not illustrated in the figure) of the dummy pixel drive circuit25, and a gate electrode (not illustrated in the figure) of the write transistor Tr2′. Each power source line Vcc′ is connected to an output terminal (not illustrated in the figure) of the power source, and a drain electrode (not illustrated in the figure) of the drive transistor Tr1′. A source electrode (not illustrated in the figure) of the write transistor Tr2′ is connected to a gate electrode (not illustrated in the figure) of the drive transistor Tr1′, and one end of the retention capacity Cs′. A source electrode (not illustrated in the figure) of the drive transistor Tr1′, and the other end of the retention capacity Cs′ are connected to an anode electrode (not illustrate in the figure) of the organic EL element14. A cathode electrode (not illustrated in the figure) of the organic EL element14is, for example, connected to the ground line GND.

(Top Face Structure of Display Panel10)

FIG. 4illustrates an example of the top face structure of the display panel10. The display panel10has, for example, the structure in which a drive panel30and a sealing panel40are bonded through a sealing layer (not illustrated in the figure).

Although not illustrated inFIG. 4, the drive panel30includes the plurality of organic EL elements11two-dimensionally arranged, and the plurality of pixel circuits31arranged adjacent to each organic EL element11in the display region12. Further, although not illustrated inFIG. 4, the drive panel30includes a plurality of organic EL elements14and17two-dimensionally arranged, and a plurality of light receiving elements arranged adjacent to each organic EL element17in the non-display region15.

On one side (long side) of the drive panel30, for example, as illustrated inFIG. 4, a plurality of video signal suppliers TAB51, a control signal supplier TCP54, and a measurement signal output TCP55are installed. On the other side (short side) of the drive panel30, for example, scanning signal suppliers TAB52are installed. Further, on one side (long side) of the drive panel30but different from the side of the video signal supplier TAB51, for example, power source suppliers TCP53are installed. The video signal supplier TAB51is formed by aerially wiring an IC in which the signal line drive circuit23is integrated, to an aperture of a film-shaped wiring substrate. The scanning signal supplier TAB52is formed by aerially wiring an IC in which the scanning line drive circuit24is integrated, to an aperture of a film-shaped wiring substrate. The power source supplier TCP53is formed by forming a plurality of wirings which electrically connect an external power source, and the power source lines Vcc and Vcc′ each other on a film. The control signal supplier TCP54is formed by forming a plurality of wirings which electrically connect the external dummy pixel drive circuit25, and the dummy pixels16and18and the light receiving element group19each other on a film. The measurement signal output TCP55is formed by forming a plurality of wirings which electrically connect the external measurement signal processing circuit27and the light receiving element group19each other on a film. In addition, the signal line drive circuit23and the scanning line drive circuit24may not be formed in the TABs, and may be formed, for example, on the drive panel30.

The sealing panel40includes, for example, a sealing substrate (not illustrated in the figure) which seals the organic EL elements11,14, and17, and a color filter (not illustrated in the figure). The color filter is, for example, provided in a region where light of the organic EL element11transmits on the surface of the sealing substrate. The color filter includes, for example, a filter for red, a filter for green, and a filter for blue (not illustrated in the figure), corresponding to each of the organic EL elements11R,11G, and11B. Further, the sealing panel40includes, for example, a light reflecting section (not illustrated in the figure). The light reflecting section is intended to reflect light emitted from the organic EL element17, thereby allowing the light to enter the light receiving element group19. For example, the light reflecting section is provided in a region where the light of the organic EL element17transmits on the surface of the sealing substrate.

Next, each circuit in the drive circuit20will be described with reference toFIG. 1. The timing generation circuit21controls the video signal processing circuit22, the signal line drive circuit23, the scanning line drive circuit24, the dummy pixel drive circuit25, the current measurement circuit26, and the measurement signal processing circuit27, thereby allowing them to operate in conjugation with each other.

The timing generation circuit21outputs, for example, a control signal21A to each of the above-described circuits in response to (in synchronization with) a synchronization signal20B input from outside. The timing generation circuit21is formed, for example, together with the video signal processing circuit22, the dummy pixel drive circuit25, the current measurement circuit26, the measurement signal processing circuit27, the storage circuit28, and the like, for example, on a control circuit substrate (not illustrated in the figure) provided separately from the display panel10.

The video signal processing circuit22corrects, for example, a digital video signal20A input from outside in response to (in synchronization with) an input of the control signal21A, and converts the corrected video signal into an analogue signal to output the analogue signal to the signal line drive circuit23. In this embodiment, the video signal processing circuit22corrects the video signal20A by using a correction information27A (will be described later) read from the storage circuit28. For example, the video signal processing circuit22reads, as the correction information27A, a correction amount (a current correction amount RI, and an efficiency correction amount Ry) (will be described later) of each display pixel13of one line from the storage circuit28for each horizontal period, and corrects the video signal20A by using the read correction amount (the current correction amount RI, and the efficiency correction amount Ry) to output a corrected video signal22A to the signal line drive circuit23.

The signal line drive circuit23outputs the analogue video signal22A input from the video signal processing circuit22to each signal line DTL in response to (in synchronization with) the input of the control signal21A. As illustrated inFIG. 4, for example, the signal line drive circuit23is provided in the video signal supplier TAB51installed on one side (long side) of the drive panel30. The scanning line drive circuit24sequentially selects one scanning line WSL from the plurality of scanning lines WSL in response to (in synchronization with) the input of the control signal21A. As illustrated inFIG. 4, for example, the scanning line drive circuit24is provided in the scanning signal supplier TAB52installed on the other side (short side) of the drive panel30.

The measurement signal processing circuit27derives the correction information27A based on the light reception signal19A input from the light receiving element group19, and outputs the derived correction information27A to the storage circuit28in response to (in synchronization with) the input of the control signal21A.

In addition, the deriving method of the correction information27A will be described later. The storage circuit28stores the correction information27A input from the measurement signal processing circuit27, so that the video signal processing circuit22may read the correction information27A stored in the storage circuit28.

The dummy pixel drive circuit25applies signal voltages Vsigi(constant value) whose magnitudes are different from each other to the signal lines DTL′ connected to each dummy pixel16in response to (in synchronization with) the input of the control signal21A, and thereby allowing each dummy pixel16to emit light with gray scales different from each other. For example, in the case where the number of the dummy pixels16is n, the dummy pixel drive circuit25allows a constant current to flow through the first dummy pixel16so that an initial current is SI, allows a constant current to flow through the second dummy pixel16so that an initial current is S2(>S1), allows a constant current to flow through the ithdummy pixel16so that an initial current is Si(>Si-1), and allows a constant current to flow through the nthdummy pixel16so that an initial current is Sn(>Sn-1). The dummy pixel drive circuit25measures, for example, the time during each dummy pixel16emitting light.

In addition, even in the case where the signal voltages Vsigihaving the constant value are continued to be applied to the signal lines DTL′ which are connected to each dummy pixel16, the luminance of each dummy pixel16is gradually reduced with the passage of time, for example, as illustrated inFIG. 5. This is because a semiconductor element such as the drive transistor Tr1′ included in the pixel circuit32which is connected to each dummy pixel16has a property to deteriorate in accordance with the current application time (current application accumulation time), and the current becomes difficult to flow in accordance with the progress of the deterioration. In addition, “Ss” inFIG. 5represents an initial current flowing through the organic EL element14in the pixel set as a reference pixel (will be described later) in each dummy pixel16.

The change of the deterioration ratio (current deterioration ratio) of the current flowing through the organic EL element14in each dummy pixel16is not uniform. For example, as illustrated inFIG. 6, when the current deterioration ratio of the pixel (dummy pixel16) set as the reference pixel is indicated on the abscissa axis, it can be seen that the change of the current deterioration ratio of the dummy pixel16having the initial current smaller than the initial current SSof the reference pixel is more gradual than the change of the current deterioration of the reference pixel at the beginning. On the other hand, it can be seen that the change of the current deterioration ratio of the dummy pixel16having the initial current larger than the initial current SSof the reference pixel is steeper than the change of the current deterioration of the reference pixel at the beginning. The change of the current deterioration ratio of each dummy pixel16exemplified inFIG. 6is represented by the following equation.
Dsi=Dssn(Si,Ss)Equation 1

In the Equation 1, Dsirepresents the current deterioration ratio of the ithdummy pixel16. Dssrepresents the current deterioration ratio of the reference pixel. n (Si, Ss) represents a power coefficient of the current of the ithdummy pixel16to the current of the reference pixel. The power coefficient n (Si, Ss) is, for example, derived by dividing (Log (Si(Tk))−Log (Si(Tk-1)) by (Log (Ss(Tk))−Log (Ss(Tk-1)), for example, as indicated in the following equation.

In the Equation 2, Log (Ss(Tk)) represents a logarithm of Ss(Tk), Log (Ss(Tk-1)) represents a logarithm of Ss(Tk-1), Log (Si(Tk)) represents a logarithm of Si(Tk), and Log (Si(Tk-1)) represents a logarithm of Si(Tk-1).

In the Equation 2, Ss(Tk) represents a current signal26A (current information) of the reference pixel at the time Tk, and corresponds to the latest current information in the current information of the reference pixel. Ss(Tk) represents the current signal26A (current information) of the reference pixel at the time Tk-1(<time Tk), and corresponds to the non-latest current information in the current information of the reference pixel. Si(Tk) represents the current signal26A (current information) of the ithdummy pixel16at the time Tk, and corresponds to the latest current information in the current information of the dummy pixel16(non-reference pixel). Si(Tk-1) represents the current signal26A (current information) of the ithdummy pixel16at the time Tk-1, and corresponds to the non-latest current information in the current information of the ithdummy pixel16(non-reference pixel). The relationship between the time Tk-1and the time Tkis, for example, represented by the following equation.
Tk=Tk-1+ΔT1Equation 3

In the Equation 3, ΔT1represents a sampling period. Here, the sampling period ΔT1indicates, for example, a cycle in which the measurement signal processing circuit27derives the value of the denominator and the value of the numerator on the right side of the Equation 2. The sampling period ΔT1is preferably set to be shorter than a sampling period ΔT2which will be described later. The measurement signal processing circuit27sets the sampling period ΔT1to be constant at any time.

For example, as illustrated inFIG. 7, when the abscissa axis indicates the ratio (Si/ Ss) of the initial current Siof each dummy pixel16to the initial current Ssof the reference pixel, the power coefficient n (Si, Ss) derived in the manner described above draws a rightward rising curve which increases with an increase of the initial current Si, at the time Tk. In addition, as can be obviously seen from the Equation 2, the power coefficient n (Si, Ss) is 1 in Ss/Ss.

Next, with reference toFIGS. 8 to 14, the deriving method of the current correction amount R1used for correcting the video signal20A will be described.

First, the initial setting will be described. The measurement signal processing circuit27sets one pixel in the plurality of dummy pixels16as the reference pixel. In this embodiment, the reference pixel is not changed to another dummy pixel16(non-reference pixel), and the same dummy pixel16is always set as the reference pixel.

Next, from the current measurement circuit26, the measurement signal processing circuit27obtains the current signal26A at the times T1and T2. Specifically, from the current measurement circuit26, the measurement signal processing circuit27obtains the current signal26A of the reference pixel as being one pixel in the plurality of dummy pixels16, at the times T1and T2. Further, from the current measurement circuit26, the measurement signal processing circuit27obtains the current signal26A of the plurality of non-reference pixels as being all the pixels except the reference pixel in the plurality of dummy pixels16, at the the times T1and T2. Next, the measurement signal processing circuit27derives, from the current information of the reference pixel, the current deterioration information (Log (Ss(T2))−Log (Ss(T1))) of the reference pixel, and derives, from the current information of each non-reference pixel, the current deterioration information (Log (Si(T2))−Log (Si(T1))) of each non-reference pixel.

Next, from the current deterioration information of the reference pixel, and the current deterioration information of each non-reference pixel, the measurement signal processing circuit27derives the power coefficient n (Si, Ss) of the current information of each non-reference pixel to the current information of the reference pixel at the time T2. Next, from the current information of the reference pixel, the measurement signal processing circuit27derives a current deterioration function Is(t) representing the temporal change of the current of the reference pixel at the time T2. Further, from the current deterioration function Is(t) and the power coefficient n (Si, Ss), the measurement signal processing circuit27derives a current deterioration function Ii(t) representing the temporal change of the current of each non-reference pixel at the time T2. In this manner, the measurement signal processing circuit27derives the current deterioration functions Is(t), and Ii(t) at the time T2by using the initial current information.

Next, the data update will be described. From the current measurement circuit26, the measurement signal processing circuit27obtains the current signal26A of the reference pixel, and the current signal26A of the plurality of non-reference pixels at the times Tk-1and Tk. The value (measurement value) of the current signal26A of the reference pixel at this time is regarded as Ss1(refer toFIG. 8). Next, from the current deterioration function Is(t) at the time Tk-1, the measurement signal processing circuit27predicts the current information of the reference pixel at the time Tk. The prediction value at this time is regarded as Ss2(refer toFIG. 8). Next, from the comparison between the measurement value Ss1and the prediction value Ss2, the measurement signal processing circuit27determines whether or not the measurement value Ss1and the prediction value Ss2are coincident with each other. As a result, for example, in the case where the measurement value Ss1and the prediction value Ss2are coincident with each other, the measurement signal processing circuit27regards the current deterioration function Is(t) at the time Tk-1as the current deterioration function Is(t) at the time Tk. On the other hand, for example, in the case where the measurement signal processing circuit27determines that the measurement value Ss1is different from the prediction value Ss2based on the comparison between the measurement value Ss1and the prediction value Ss2, the measurement signal processing circuit27derives the current deterioration function Is(t) at the time Tk, from the current information of the reference pixel.

Next, from the current information of the reference pixel, the measurement signal processing circuit27derives the current deterioration information (Log (Ss(Tk))−Log (Ss(Tk-1))) of the reference pixel. Further, from the current information of the plurality of non-reference pixels, the measurement signal processing circuit27derives the current deterioration information (Log (Si(Tk))−Log (Si(Tk-1))) of each non-reference pixel. Next, from the current deterioration information of the reference pixel, and the current deterioration information of each non-reference pixel, the measurement signal processing circuit27derives the power coefficient n (Si, Ss) at the time Tk.

Next, the measurement signal processing circuit27updates parameters (for example, p1, p2, . . . , pm) of the current deterioration function Is(t) at the time Tk-1to parameters (for example, p1′, p2′, . . . , pm′) of the current deterioration function Is(t) at the time Tk(refer toFIG. 9). In other words, the measurement signal processing circuit27updates the parameters of the current deterioration function Is(t) in accordance with the latest current information (Ss(Tk)) in the current information of the reference pixel, and the non-latest current information (Ss(Tk-1)) in the current information of the reference pixel. The measurement signal processing circuit27stores, for example, the parameters of the newly-obtained current deterioration function Is(t) in the storage circuit28.

Next, from the current deterioration function Is(t) at the time Tk(refer toFIG. 10), and the power coefficient n (Si, Ss) (refer toFIG. 11), the measurement signal processing circuit27derives the current deterioration function Ii(t) at the time Tk(refer toFIG. 12). Specifically, the measurement signal processing circuit27derives the current deterioration function Ii(t) at the time Tkby using the following equation.
Ii(t)=Is(t)n(Si, Ss)Equation 4

Next, the measurement signal processing circuit27updates the parameter of the current deterioration function Ii(t) of each non-reference pixel at the time Tk-1to the parameters of the current deterioration function Ii(t) of each non-reference pixel at the time Tk. The measurement signal processing circuit27stores, for example, the parameters of the newly-obtained current deterioration function Ii(t) in the storage circuit28.

(Prediction of Current Deterioration Ratio)

Next, the measurement signal processing circuit27predicts the current deterioration ratio of each display pixel13during the time until the next sampling period comes. Specifically, from the current deterioration function Is(t), the current deterioration function Ii(t), and a history of the video signal20A of each display pixel13, the measurement signal processing circuit27derives a light emission accumulation time Txyof each display pixel13at the reference current. The measurement signal processing circuit27obtains, for example, the light emission accumulation time Txyof each display pixel13at the reference current as will be described below.

FIG. 13schematically illustrates the deriving process of the light emission accumulation time Txyof each display pixel13at the reference luminance. For example, as illustrated inFIG. 13, it is assumed that the luminance of a certain display pixel13is changed as the certain display pixel13emits light with the initial current S1(initial luminance Y1) during the time T=0 to t1, emits light with the initial current S2(initial luminance Y2) during the time T=t1to t2, and emits light with the initial current Sn(initial luminance Yn) during the time T=t2to t3. At this time, in a narrow sense, the luminance of this display pixel13is deteriorated along the deterioration curve of the initial current S1during the time T=0 to t1, deteriorated along the deterioration curve of the initial current S2during the time T=t1to t2, and deteriorated along the deterioration curve of the initial current Snduring the time T=t2to t3. As a result, it is assumed that the luminance of this display pixel13is deteriorated to 48%, for example, as illustrated inFIG. 13. Therefore, by obtaining the time when the deterioration ratio in the current deterioration curve (Is(t)) of the reference pixel becomes 48%, it may be possible to obtain the light emission accumulation time Txyof each display pixel13at the reference luminance. In this manner, by tracking the current deterioration curve in each gray scale in accordance with the intensity (gray scale) of the input signal, it may be possible to obtain the light emission accumulation time Txyof each display pixel13at the reference luminance, and the current deterioration ratio of each display pixel13.

Next, from the obtained light emission accumulation time Txy(or the predicted current deterioration ratio of each display pixel13), and the gamma characteristic of the display panel10, the measurement signal processing circuit27derives the correction amount to the video signal. The measurement signal processing circuit27obtains the correction amount to the video signal, for example, as will be described below.

FIG. 14illustrates an example of the relationship between the gray scale (value of the video signal20A) and the luminance at T=0, and Txy. The gray scale-luminance characteristic at T=0 is a so-called gamma characteristic. The gray scale-luminance characteristic at T=Txyis obtained by attenuating the luminance for all the gray scales to 48% with respect to the gamma characteristic. Here, in a certain display pixel13, when the value of the video signal20A is Sxy, it can be seen that the luminance of this display pixel13has a value corresponding to a white circle in the figure in the initial state. In other words, when the light emission accumulation time Txyis passed from the initial state, it is predictable that the luminance of this display pixel13has a value obtained by attenuating the luminance in the initial state to 48%.

Thus, the measurement signal processing circuit27derives the current correction amount R1to be subjected to the video signal20A so that the luminance when the light emission accumulation time Txyis passed from the initial state is identical to the luminance in the initial state. Specifically, the measurement signal processing circuit27derives the current correction amount R1by using the following equation.

In the Equation 5,GIrepresents a current correction gain, and it is 1/0.48 in the example above. “r” represents an index number (gamma value) of the gamma characteristic.

Finally, the measurement signal processing circuit27stores the current correction amount R1as the correction information27A in the storage circuit28. In this manner, the measurement signal processing circuit27corrects the efficiency deterioration caused by deterioration of the semiconductor element such as the drive transistor Tr1′ included in the pixel circuit32.

Further, the dummy pixel drive circuit25allows the constant currents having magnitudes different each other to flow through each dummy pixel18in response to (in synchronization with) the input of the control signal21A, thereby allowing each dummy pixel18to emit light. For example, in the case where the number of the dummy pixels18is n, the dummy pixel drive circuit25allows a constant current to flow through the first dummy pixel18so that the initial luminance is Y1, allows a constant current to flow through the second dummy pixel18so that the initial luminance is Y2(>Y1), allows a constant current to flow through the ithdummy pixel18so that the initial luminance is Yi(>Yi-1), and allows a constant current to flow through the nthdummy pixel18so that the initial luminance is Yn(>Yn-1). The dummy pixel drive circuit25measures, for example, the time during the current is passed through each dummy pixel18.

In addition, even in the case where the constant current is continued to be flown through each dummy pixel18, the luminance of each dummy pixel18is gradually reduced with the passage of the time, for example, as illustrated inFIG. 15. This is because the organic EL element17included in each dummy pixel18has a property to deteriorate in accordance with the current application time (light emission accumulation time), and the light emission efficiency is deteriorated in accordance with the progress of the deterioration. In addition, YsinFIG. 15represents the initial luminance of the pixel set as the reference pixel (will be described later) in each dummy pixel18.

The change of the efficiency deterioration ratio of each dummy pixel18is not uniform. For example, as illustrated inFIG. 16, when the efficiency deterioration ratio of the pixel (dummy pixel18) set as the reference pixel is indicated on the abscissa axis, it can be seen that the change of the efficiency deterioration ratio of the dummy pixel18having the initial luminance smaller than the initial luminance YSof the reference pixel is more gradual than the change of the efficiency deterioration of the reference pixel at the beginning. On the other hand, it can be seen that the change of the efficiency deterioration ratio of the dummy pixel18having the initial luminance larger than the initial luminance YSof the reference pixel is steeper than the change of the efficiency deterioration of the reference pixel at the beginning. The change of the efficiency deterioration ratio of each dummy pixel18exemplified inFIG. 16is represented by the following equation.
Di=Dsn(Yi,Ys)Equation 6

In the Equation 6, Direpresents the efficiency deterioration ratio of the ithdummy pixel18. Dsrepresents the efficiency deterioration ratio of the reference pixel. n (Yi, Ys) represents a power coefficient of the luminance of the ithdummy pixel18to the luminance of the reference pixel. The power coefficient n (Yi, Ys) is, for example, derived by dividing (Log (Yi(Tk))−Log (Yi(Tk-1)) by (Log (Ys(Tk))−Log (Ys(Tk-1)), for example, as indicated in the following equation.

In the Equation 7, Log (Ys(Tk)) represents a logarithm of Ys(Tk), Log (Ys(Tk-1)) represents a logarithm of Ys(Tk-1), Log (Yi(Tk)) represents a logarithm of Yi(Tk), and Log (Yi(Tk-1)) represents a logarithm of Yi(Tk-1).

In the Equation 7, Ys(Tk) represents the light reception signal19A (luminance information) of the reference pixel at the time Tk, and corresponds to the latest luminance information in the luminance information of the reference pixel. Ys(Tk-1) represents the light reception signal19A (luminance information) of the reference pixel at the time Tk-1(<time Tk), and corresponds to the non-latest luminance information in the luminance information of the reference pixel. Yi(Tk) represents the light reception signal19A (luminance information) of the ithdummy pixel18at the time Tk, and corresponds to the latest luminance information in the luminance information of the ithdummy pixel18(non-reference pixel). Yi(Tk-1) represents the light reception signal19A (luminance information) of the ithdummy pixel18at the time Tk-1, and corresponds to the non-latest luminance information in the luminance information of the ithdummy pixel18(non-reference pixel). The relationship between the time Tk-1and the time Tkis, for example, represented by the following equation.
Tk=Tk-1+ΔT2Equation 8

In the Equation 8, ΔT2represents a sampling period. Here, the sampling period ΔT2indicates, for example, a cycle in which the measurement signal processing circuit27derives the value of the denominator and the value of the numerator on the right side of the Equation 7. The measurement signal processing circuit27sets the sampling period ΔT2to be constant at any time.

For example, as illustrated inFIG. 17, when the abscissa axis indicates the ratio (Yi/Ys) of the initial luminance Yiof each dummy pixel16to the initial current Ysof the reference pixel, the power coefficient n (Yi, Ys) derived in the manner described above draws a rightward rising curve which increases with an increase of the initial luminance Yi, at the time Tk. In addition, as can be obviously seen from the Equation 7, the power coefficient n (Yi, Ys) is 1 in Ys/Ys.

Next, with reference toFIGS. 18 to 24, the deriving method of the efficiency correction amount Ryused for correcting the video signal20A will be described.

First, the initial setting will be described. The measurement signal processing circuit27sets one pixel in the plurality of dummy pixels18as the reference pixel. In this embodiment, the reference pixel is not change to another dummy pixel18(non-reference pixel), and the same dummy pixel18is always set as the reference pixel.

Next, from the light receiving element group19, the measurement signal processing circuit27obtains the light reception signal19A at the times T1and T2. Specifically, from the light receiving element group19, the measurement signal processing circuit27obtains the light reception signal19A of the reference pixel as being one pixel in the plurality of dummy pixels18, at the times T1and T2. Further, from the light receiving element group19, the measurement signal processing circuit27obtains the light reception signal19A of the plurality of non-reference pixels as being all the pixels except the reference pixel in the plurality of dummy pixels18, at the times T1and T2. Next, the measurement signal processing circuit27derives, from the luminance information of the reference pixel, the efficiency deterioration information (Log (Ys(T2))−Log (Ys(Ti))) of the reference pixel, and derives, from the luminance information of each non-reference pixel, the efficiency deterioration information (Log (Yi(T2))−Log (Yi(T1))) of each non-reference pixel.

Next, from the efficiency deterioration information of the reference pixel, and the efficiency deterioration information of each non-reference pixel, the measurement signal processing circuit27derives the power coefficient n (Y1, Ys) of the luminance information of each non-reference pixel to the luminance information of the reference pixel at the time T2. Next, from the luminance information of the reference pixel, the measurement signal processing circuit27derives an efficiency deterioration function Fs(t) representing the temporal change of the luminance of the reference pixel at the time T2. Further, from the efficiency deterioration function Fs(t) and the power coefficient n (Y1, Ys), the measurement signal processing circuit27derives an efficiency deterioration function Fi(t) representing the temporal change of the luminance of each non-reference pixel, at the time T2. In this manner, the measurement signal processing circuit27derives the efficiency deterioration functions Fs(t), and Fi(t) at the time T2by using the initial luminance information.

Next, the data update will be described. From the light receiving element group19, the measurement signal processing circuit27obtains the light reception signal19A of the reference pixel, and the light reception signal19A of the plurality of non-reference pixels at the times Tk-1and Tk. The value (measurement value) of the light reception signal19A of the reference pixel at this time is regarded as Ys1(refer toFIG. 18). Next, from the efficiency deterioration function Fs(t) at the time Tk-1, the measurement signal processing circuit27predicts the luminance information of the reference pixel at the time Tk. The prediction value at this time is regarded as Ys2(refer toFIG. 18). Next, from the comparison between the measurement value Ys1and the prediction value Ys2, the measurement signal processing circuit27determines whether or not the measurement value Ys1and the prediction value Ys2are coincident with each other. As a result, for example, in the case where the measurement value Ys1and the prediction value Ys2are coincident with each other, the measurement signal processing circuit27regards the efficiency deterioration function Fs(t) at the time Tk-1as the efficiency deterioration function Fs(t) at the time Tk. On the other hand, for example, in the case where the measurement signal processing circuit27determines that the measurement value Ys1is different from the prediction value Ys2based on the comparison between the measurement value Ys1and the prediction value Ys2, the measurement signal processing circuit27derives the efficiency deterioration function Fs(t) at the time Tkfrom the luminance information of the reference pixel.

Next, from the luminance information of the reference pixel, the measurement signal processing circuit27derives the efficiency deterioration information (Log (Ys(Tk))−Log (Ys(Tk-1))) of the reference pixel. Further, from the luminance information of the plurality of non-reference pixels, the measurement signal processing circuit27derives the efficiency deterioration information (Log (Yi(Tk))−Log (Yi(Tk-1))) of each non-reference pixel. Next, from the efficiency deterioration information of the reference pixel, and the efficiency deterioration information of each non-reference pixel, the measurement signal processing circuit27derives the power coefficient n (Yi, Ys) at the time Tk.

Next, the measurement signal processing circuit27updates the parameters (for example, p1, p2, . . . , pm) of the efficiency deterioration function Fs(t) at the time Tk-1to parameters (for example, p1′, p2′, . . . , pm′) of the efficiency deterioration function Fs(t) at the time Tk(refer toFIG. 19). In other words, the measurement signal processing circuit27updates the parameters of the efficiency deterioration function Fs(t) in accordance with the latest luminance information (Ys(Tk)) in the luminance information of the reference pixel, and the non-latest luminance information (Ys(Tk-1)) in the luminance information of the reference pixel. The measurement signal processing circuit27stores, for example, the parameters of the newly-obtained efficiency deterioration function Fs(t) in the storage circuit28.

Next, from the efficiency deterioration function Fs(t) at the time Tk(refer toFIG. 20), and the power coefficient n (Yi, Ys) (refer toFIG. 21), the measurement signal processing circuit27derives the efficiency deterioration function Fi(t) at the time Tk(refer toFIG. 22). Specifically, the measurement signal processing circuit27derives the efficiency deterioration function Fi(t) at the time Tkby using the following equation.
Fi(t)=Fs(t)n(Yi,Ys)Equation 9

Next, the measurement signal processing circuit27updates the parameters of the efficiency deterioration function Fi(t) of each non-reference pixel at the time Tk-1to the parameters of the efficiency deterioration function Fi(t) of each non-reference pixel at the time Tk. The measurement signal processing circuit27stores, for example, the parameters of the newly-obtained efficiency deterioration function Fi(t) in the storage circuit28.

(Prediction of Efficiency Deterioration Ratio)

Next, the measurement signal processing circuit27predicts the efficiency deterioration ratio of each display pixel13during the time until the next sampling period comes. Specifically, from the efficiency deterioration function Fs(t), the efficiency deterioration function Fi(t), and the history of the video signal20A of each display pixel13, the measurement signal processing circuit27derives the light emission accumulation time Txyof each display pixel13at the reference luminance. The measurement signal processing circuit27obtains, for example, the light emission accumulation time Txyof each display pixel13at the reference luminance as will be described below.

FIG. 23schematically illustrates the deriving process of the light emission accumulation time Txyof each display pixel13at the reference luminance. For example, as illustrated inFIG. 23, it is assumed that the luminance of a certain display pixel13is changed as the certain display pixel13emits light with the initial luminance Y1during the time T=0 to t1, emits light with the initial luminance Y2during the time T =t1to t2, and emits light with the initial luminance Ynduring the time T=t2to t3. At this time, in a narrow sense, the luminance of this display pixel13is deteriorated along the deterioration curve of the initial luminance Y1during the time T=0 to t1, deteriorated along the deterioration curve of the initial luminance Y2during the time T=t1to t2, and deteriorated along the deterioration curve of the initial luminance Ynduring the time T=t2to t3. As a result, it is assumed that the luminance of this display pixel13is deteriorated to 48%, for example, as illustrated inFIG. 23. Therefore, by obtaining the time when the deterioration ratio in the efficiency deterioration curve (Fs(t)) of the reference pixel becomes 48%, it may be possible to obtain the light emission accumulation time Txyof each display pixel13at the reference luminance. In this manner, by tracking the efficiency deterioration curve in each gray scale in accordance with the intensity (gray scale) of the input signal, it may be possible to obtain the light emission accumulation time Txyof each display pixel13at the reference luminance, and the efficiency deterioration ratio of each display pixel13.

Next, from the obtained light emission accumulation time Txy(or the predicted efficiency deterioration ratio of each display pixel13), and the gamma characteristic of the display panel10, the measurement signal processing circuit27derives the correction amount to the video signal. The measurement signal processing circuit27obtains the correction amount to the video signal, for example, as will be described below.

FIG. 24illustrates an example of the relationship between the gray scale (value of the video signal20A), and the luminance at T=0, and Txy. The gray scale-luminance characteristic at T=0 is a so-called gamma characteristic. The gray scale-luminance characteristic at T=Txyis obtained by attenuating the luminance to 48% for all the gray scales with respect to the gamma characteristic. Here, in a certain display pixel13, when the value of the video signal20A is Sxy, it can be seen that the luminance of this display pixel13has a value corresponding to a white circle in the figure in the initial state. In other words, when the light emission accumulation time Txyis passed from the initial state, it is predictable that the luminance of this display pixel13has a value obtained by attenuating the luminance in the initial state to 48%.

Thus, the measurement signal processing circuit27derives the efficiency correction amount Ryto be subjected to the video signal20A so that the luminance when the light emission accumulation time Txyis passed from the initial state is identical to the luminance in the initial state. Specifically, the measurement signal processing circuit27derives the efficiency correction amount Ryby using the following equation.

In the Equation 10, Gyrepresents a luminance correction gain, and it is 1/0.48 in the example above.

Finally, the measurement signal processing circuit27stores the efficiency correction amount Ryas the correction information27A in the storage circuit28. In this manner, the measurement signal processing circuit27corrects the deterioration of the light emission efficiency caused by the deterioration of the organic EL element17included in each dummy pixel18.

Next, operations and effects of the display deice1of this embodiment will be described. The video signal20A and the synchronization signal20B are input to the display device1. Then, each display pixel13is driven by the signal line drive circuit23and the scanning line drive circuit24, and a video in response to the video signal20A of each display pixel13is displayed on the display region12. Meanwhile, signal voltages Vsigi(constant value) having magnitudes different from each other are applied to the signal lines DTL′ connected to each dummy pixel16by the dummy pixel drive circuit25, and each dummy pixel16emits light with gray scales different from each other. As a result, the current signal26A corresponding to the current value flowing through the organic EL element14of each dummy pixel16is output from the current measurement circuit26. Further, when each dummy pixel18is driven by the dummy pixel drive circuit25, the light receiving element group19is also driven at the same time. Therefore, the constant currents having magnitudes different from each other are allowed to flow through each dummy pixel18, each dummy pixel18emits light with the luminance according to the magnitude of the constant current, and the light emitted from each dummy pixel18is detected in the light receiving element group19. As a result, the light reception signal19A corresponding to the light emitted from each dummy pixel18is output from the light receiving element group19. Next, the following process is performed by the measurement signal processing circuit27.

In other words, the power coefficient n (Si, Ss) of the current signal26A (current information) of the non-reference pixel to the current signal26A (current information) of the reference pixel is derived from the current signal26A. Next, the current deterioration function Is(t) of the reference pixel is derived from the current information of the reference pixel, and the current deterioration function Ii(t) of the non-reference pixel is derived from the current deterioration function Is(t) and the power coefficient n (Si, Ss). Next, by utilizing the current deterioration function Is(t), the current deterioration function Ii(t), and the history of the video signal20A of each display pixel13, the light emission accumulation time Txyof each display pixel13at the reference current, and the current deterioration ratio of each display pixel13are predicted. Next, the current correction amount RIis applied to the video signal20A of each display pixel13so that the luminance when the light emission accumulation time Txyis passed from the initial state is identical to the luminance in the initial state.

Further, the power coefficient n (Yi, Ys) of the light reception signal19A (luminance information) of the non-reference pixel to the light reception signal19A (luminance information) of the reference pixel is derived from the light reception signal19A. Next, the efficiency deterioration function Fs(t) of the reference pixel is derived from the luminance information of the reference pixel, and the efficiency deterioration function Fi(t) of the non-reference pixel is derived from the efficiency deterioration function Fs(t) and the power coefficient n (Yi, Ys). Next, by utilizing the efficiency deterioration function Fs(t), the efficiency deterioration function Fi(t), and the history of the video signal20A of each display pixel13, the light emission accumulation time Txyof each display pixel13at the reference current, and the efficiency deterioration ratio of each display pixel13are predicted. Next, the efficiency correction amount Ryis applied to the video signal20A of each display pixel13so that the luminance when the light emission accumulation time Txyis passed from the initial state is identical to the luminance in the initial state.

In this manner, in this embodiment, by utilizing the current deterioration function Is(t), the current deterioration function Ii(t) obtained from the current deterioration function Is(t) and the power coefficient n (Si, Ss), and the history of the video signal20A of each display pixel13, the current deterioration ratio of each display pixel13is predicted. Further, by utilizing the efficiency deterioration function Fs(t), the efficiency deterioration function Fi(t) obtained from the efficiency deterioration function Fs(t) and the power coefficient n (Yi, Ys), and the history of the video signal20A of each display pixel13, the efficiency deterioration ratio of each display pixel13is predicted. Thereby, it may be possible to predict the efficiency deterioration of each display pixel13with a high accuracy, and thus it may be possible to apply the appropriate correction amount (the current correction amount R1and the efficiency correction amount Ry) to the video signal20A of each display pixel13so that the luminance of each display pixel13is identical to the luminance in the initial state. As a result, it may be possible to accurately prevent seizure.

Further, in this embodiment, it may be possible to predict the current deterioration ratio and the efficiency deterioration ratio of each display pixel13by using the data (Ss(Tk), Ss(Tk-1), Ys(Tk), and Ys(Tk-1)) at the time of observation. Therefore, it may be possible to predict the efficiency deterioration of each display pixel with a high accuracy without an observation for a long time. Therefore, the predicting method of this embodiment is extremely practical. Further, in this embodiment, since it may be possible to predict the efficiency deterioration ratio of each display pixel13by using the data at the time of observation, it may be possible to suppress and reduce the memory amount and the calculation amount which are necessary for the update.

In the foregoing embodiment, although the correction by using both the current correction amount RIand the efficiency correction amount Ryis performed on the video signal20A of each display pixel13, the correction by using only one of the current correction amount RIand the efficiency correction amount Rymay be performed.

Further, in the foregoing embodiment, although all the dummy pixels16of the initial currents S1to Snare composed of a single pixel of a set of organic EL elements14R,14G and14B, each dummy pixel16(low-current pixel) in which the initial current Siis low may be composed of a plurality of dummy pixels (second dummy pixels) (not illustrated in the figure). In this case, from the average value of the currents flowing through the organic EL elements14which are connected to the plurality of second dummy pixels, the measurement signal processing circuit27may derive the denominator or the numerator on the right side of the Equation 2. Therefore, it may be possible to make a measurement error small in the dummy pixel16having the low luminance. Thus, it may be possible to predict the efficiency deterioration of the display pixel13having the low luminance with a high accuracy. As a result, it may be possible to more accurately prevent the seizure.

Further, in the foregoing embodiment, although all the dummy pixels18of the initial luminances Y1to Ynare composed of a single pixel of a set of organic EL elements17R,17G, and17B, each dummy pixel18(low-luminance pixel) in which the initial luminance Yiis low may be composed of a plurality of dummy pixels (third dummy pixels) (not illustrated in the figure). In this case, from the average value of the luminance of the plurality of third dummy pixels, the measurement signal processing circuit27may derive the denominator or the numerator on the right side of the Equation7. Therefore, it may be possible to make a measurement error small in the dummy pixel18having the low luminance. Thus, it may be possible to predict the efficiency deterioration of the display pixel13having the low luminance with a high accuracy. As a result, it may be possible to more accurately prevent the seizure.

In the foregoing embodiment, although the specific dummy pixel16is set as the reference pixel at any time, the dummy pixel16which has been set as the non-reference pixel may be set as the reference pixel, if necessary. For example, when the measurement signal processing circuit27detects that the current flowing through the organic EL element14which is connected to the reference pixel has a value equal to or lower than a predetermined value, the measurement signal processing circuit27excludes the dummy pixel16which has been set as the reference pixel so far, and sets one pixel in the plurality of non-reference pixels as the new reference pixel. Thereafter, the measurement signal processing circuit27derives the denominator and the numerator on the right side of the Equation 2 in the same manner as heretofore. In this case, even in the case where a failure is generated in the reference pixel, it may be possible to continue to predict the efficiency deterioration. Therefore, it may be possible to improve the reliability of the prediction of the efficiency deterioration.

Further, in the foregoing embodiment, although the specific dummy pixel18is set as the reference pixel at any time, the dummy pixel18which has been set as the non-reference pixel may be set as the reference pixel, if necessary. For example, when the measurement signal processing circuit27detects that the luminance of the reference pixel has a value equal to or lower than a predetermined value, the measurement signal processing circuit27excludes the dummy pixel18which has been set as the reference pixel so far, and sets one pixel in the plurality of non-reference pixels as the new reference pixel. Thereafter, the measurement signal processing circuit27derives the denominator and the numerator on the right side of the Equation 7 in the same manner as heretofore. In this case, even in the case where a failure is generated in the reference pixel, it may be possible to continue to predict the efficiency deterioration. Therefore, it may be possible to improve the reliability of the prediction of the efficiency deterioration.

In the foregoing embodiment, although the sampling period ΔT1is constant at any time, it may be variable. For example, the measurement signal processing circuit27may change the sampling period ΔT1according to the light emission accumulation time of the plurality of dummy pixels16. In that case, for example, when the light emission accumulation time Txyis a long time, and the efficiency deterioration is hardly generated, it may be possible to extend the sampling period ΔT1. Therefore, it may be possible to suppress and reduce the calculation amount which is necessary for the update.

In the foregoing embodiment, although the sampling period ΔT2is constant at any time, it may be variable. For example, the measurement signal processing circuit27may change the sampling period ΔT2according to the light emission accumulation time of the plurality of dummy pixels18. In that case, for example, when the light emission accumulation time Txyis a long time, and the efficiency deterioration is hardly generated, it may be possible to extend the sampling period ΔT2. Therefore, it may be possible to suppress and reduce the calculation amount which is necessary for the update.

In the foregoing embodiment, although the power coefficient n (Si, Ss) is derived by using the Equation 2, for example, the power coefficient n (Si, Ss) may be derived by using the following equation.

In the Equation 11, the denominator in the second term on the right side represents the deterioration rate of the reference pixel at the time Tk. The numerator in the second term on the right side represents the deterioration rate of the non-reference pixel at the time Tk. In the Equation 12, the second term on the right side is obtained by dividing the deterioration rate of the reference pixel at the time Tkby the deterioration rate of the non-reference pixel at the time Tk.

In the case where the power coefficient n (Si, Ss) is derived by using the Equation 11 or the Equation 12, it may be possible to derive the power coefficient n (Si, Ss) only with the four arithmetic operations, and calculation of a logarithm like when the Equation 2 is used is not necessary. Therefore, it may be possible to suppress and reduce the calculation amount, in comparison with the case where the power coefficient n (Si, Ss) is derived by using the Equation 2.

In the foregoing embodiment, although the power coefficient n (Yi, Ys) is derived by using the Equation 7, for example, the power coefficient n (Yi, Ys) may be derived by using the following equation.

In the Equation 13, the denominator in the second term on the right side represents the deterioration rate of the reference pixel at the time Tk. The numerator in the second term on the right side represents the deterioration rate of the non-reference pixel at the time Tk. In the Equation 14, the second term on the right side is obtained by dividing the deterioration rate of the reference pixel at the time Tkby the deterioration rate of the non-reference pixel at the time Tk.

In the case where the power coefficient n (Yi, Ys) is derived by using the Equation 13 or the Equation 14, it may be possible to derive the power coefficient n (Yi, Ys) only with the four arithmetic operations, and calculation of a logarithm like when the Equation 7 is used is not necessary. Therefore, it may be possible to suppress and reduce the calculation amount, in comparison with the case where the power coefficient n (Yi, Ys) is derived by using the Equation 7.

3. Application Examples

Hereinafter, a description will be made on application examples of the display device1described in the foregoing embodiment and its modification. The display device1of the foregoing embodiment and the like is applicable to display devices in electronic appliances in various fields, in which a video signal input from outside, or a video signal generated inside the display device is displayed as an image or a video, such as a television device, a digital camera, a notebook personal computer, a mobile terminal device such as a mobile phone, and a video camera.

First Application Example

FIG. 25illustrates an appearance of a television device to which the display device1of the foregoing embodiment and the like is applied. The television device includes, for example, a video display screen section300including a front panel310and a filter glass320. The video display screen section300is composed of the display device1of the foregoing embodiment and the like.

Second Application Example

FIGS. 26A and 26Billustrate an appearance of a digital camera to which the display device1of the foregoing embodiment and the like is applied. The digital camera includes, for example, a light emitting section410for a flash, a display section420, a menu switch430, and a shutter button440. The display section420is composed of the display device1of the foregoing embodiment and the like.

Third Application Example

FIG. 27illustrates an appearance of a notebook personal computer to which the display device1of the foregoing embodiment and the like is applied. The notebook personal computer includes, for example, a main body510, a keyboard520for operation of inputting characters and the like, and a display section530for displaying an image. The display section530is composed of the display device1of the foregoing embodiment and the like.

Fourth Application Example

FIG. 28illustrates an appearance of a video camera to which the display device1of the foregoing embodiment and the like is applied. The video camera includes, for example, a main body610, a lens620for capturing an object provided on the front side face of the main body610, a start/stop switch in capturing630, and a display section640. The display section640is composed of the display device1of the foregoing embodiment and the like.

Fifth Application Example

FIGS. 29A to 29Gillustrate an appearance of a mobile phone to which the display device1of the foregoing embodiment and the like is applied. In the mobile phone, for example, an upper package710and a lower package720are jointed by a joint section (hinge section)730. The mobile phone includes a display740, a sub-display750, a picture light760, and a camera770. The display740or the sub-display750is composed of the display device1of the foregoing embodiment and the like.

The present application contains subject matter related to that disclosed in Japanese Priority Patent Application JP 2009-217183 filed in the Japanese Patent Office on Sep. 18, 2009, the entire contents of which is hereby incorporated by reference.