JP2010101926A - Image display device and method for driving the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To lessen deterioration in image quality caused by abnormal pixels, by applying this to an image display device that uses an organic EL element. <P>SOLUTION: The image display device 21 has a display part 2 in which pixels are arranged in a matrix form, and a drive part which drives the pixels arranged in the display part 2, according to the image data for displaying a desired image on the display part. The drive part has a luminance-adjusting part for adjusting the luminance of abnormal light-emitting pixels and successively corrects the image data input, to correct the luminance of the abnormal light emitting pixel by the luminance-adjusting part. The luminance of the abnormal light emitting pixels is made closer to the light-emitting luminance of normal pixels. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image display device and a method for driving the image display device, and can be applied to an image display device using an organic EL (Electro Luminescence) element, for example. The present invention reduces image quality deterioration due to abnormal light emission pixels by correcting the light emission luminance of abnormal light emission pixels to approximate the light emission luminance of normal pixels.

  In recent years, image display devices using organic EL elements have been actively developed. Here, as shown in FIG. 6, in this type of image display device 1, the display unit 2 is formed by arranging pixels in a matrix. The image display device 1 drives the display unit 2 by the drive circuit 3 in accordance with the sequentially input image data D1, and displays a desired image on the display unit 2.

  Image display devices using organic EL elements are roughly classified into a passive matrix type and an active matrix type. Here, as shown in FIG. 7, the passive matrix type image display device 5 has the display unit 2 in which pixels by the organic EL elements OLED (1, 1), OLED (1, 2),. Is formed. The image display device 5 sequentially and cyclically selects the scanning lines SCAN (1), SCAN (2),... By the switch circuit 6 provided in the drive circuit 3. The image display device 5 distributes the sequentially input image data D1 to the current drive circuits 7 (1), 7 (2),..., And the current drive circuits 7 (1), 7 (2),. Drive currents Isig (1), Isig (2),... Corresponding to the data D1 are generated and output to the corresponding signal lines SIG (1), SIG (2),. Thus, the image display device 5 displays the desired image by sequentially emitting the organic EL elements OLED (1, 1), OLED (1, 2),. Accordingly, the image display device 5 sets the gradation of each pixel by current driving through the signal lines SIG (1), SIG (2),.

  As shown in FIG. 8, the active matrix type image display device 11 drives the organic EL element OLED and the organic EL element OLED constituting the pixels PIX (1,1), PIX (1,2),. The display unit 2 is formed by arranging the pixel circuits 16 including the driving circuits in a matrix. Here, the pixel circuit 16 includes, for example, both ends of a series circuit of a P-channel transistor Tr2 and the organic EL element OLED connected to the power sources Vdd and Vss, and the driving transistor Tr1 drives the organic EL element with a driving current according to the gate-source voltage. Drive the OLED. The pixel circuit 16 is provided with a holding capacitor Cs that holds the gate-source voltage of the driving transistor Tr1 between the gate and source of the driving transistor Tr1. In the pixel circuit 16, the terminal voltage of the storage capacitor Cs is sequentially set via the signal lines SIG (1), SIG (2),... Under the control of the write transistor Tr2 via the scanning line SCAN. As a result, the pixel circuit 16 sets the gate-source voltage of the drive transistor Tr1 via the signal lines SIG (1), SIG (2),... To set the gradation of each pixel. The organic EL element OLED is current-driven with a driving current corresponding to the gate-source voltage.

  The drive circuit 3 distributes the sequentially input image data D1 to the respective signal lines SIG (1), SIG (2),..., And performs digital-analog conversion processing on the respective signal lines SIG (1), SIG (2). ,... Are set to drive voltages Vsig (1), Vsig (2),. Further, the drive circuit 3 controls the write transistor Tr2 on the scanning lines SCAN (1), SCAN (2),... Corresponding to the setting of the drive voltages Vsig (1), Vsig (2),. Is output.

  In addition, the image display device using the organic EL element can change the drive current of the organic EL element shown in FIG. 6 and FIG. 7 to express the gradation, and can also change the light emission time of the organic EL element to change the gradation. There are proposed a method (time modulation method) for expressing the tone, a method (area modulation method) for expressing gradation by changing the light emitting area of the organic EL element, and the like.

Regarding an active matrix type image display device using an organic EL element, Japanese Patent Application Laid-Open No. 2007-310311 discloses a method of forming a pixel circuit using two transistors. Therefore, according to the method disclosed in Japanese Patent Application Laid-Open No. 2007-310311, the configuration can be simplified. Japanese Patent Laid-Open No. 2007-310311 discloses a configuration for correcting variations in threshold voltage and mobility in driving transistors that drive organic EL elements. Therefore, according to the configuration disclosed in Japanese Patent Application Laid-Open No. 2007-310311, it is possible to prevent image quality deterioration due to variations in threshold voltage and mobility in driving transistors.
JP 2007-310311 A

  By the way, the organic EL element image display device generates abnormal light-emitting pixels whose light emission luminance is remarkably different from that of normal pixels due to various factors.

  That is, an organic EL element applied to this type of image display apparatus sandwiches an organic EL layer between a cathode and an anode held so as to face each other at a minute interval, and this minute interval is several [μm] to 10 [μm]. Set to In the image display device, the film thickness, film quality, and the like of the organic EL layer may locally change due to minute dust, contamination, and the like. In this case, the driving voltage (voltage / current characteristics) of the organic EL element, the light emission efficiency, and the like locally change, and an abnormal light emitting pixel is generated.

  In an active matrix image display device, characteristics of TFTs (Thin Film Transistors) constituting a pixel circuit are locally changed due to minute dust, contamination, or the like, and as a result, abnormal luminescent pixels may be generated. In the active matrix image display device, abnormal light emitting pixels are also generated when a storage capacitor and a leak current are locally generated due to minute dust, contamination, or the like.

  These abnormal light-emitting pixels are visually recognized in the same manner as the dark spots when the light emission luminance is significantly lower than the surrounding normal pixels. On the other hand, when the emission luminance is remarkably higher than that of surrounding normal pixels, it is visually recognized in the same manner as a bright spot. Here, the dark spot is a defective pixel that does not emit light, and the bright spot is a defective pixel that always emits light at a luminance level of 100%. As a result, these abnormal light-emitting pixels have a problem of remarkably degrading the image quality as well as dark spots and bright spots, although they can express gradation.

  The present invention has been made in consideration of the above points, and proposes an image display device and an image display device driving method capable of reducing image quality degradation due to abnormal light emitting pixels whose light emission luminance is significantly different from that of normal pixels. It is something to try.

  In order to solve the above problems, the invention of claim 1 drives a display unit in which pixels are arranged in a matrix and the pixels arranged in the display unit in accordance with image data, and displays a desired image on the display unit. The present invention is applied to an image display device having a driving unit. The drive unit includes a luminance adjustment unit that corrects the luminance of the abnormal light emitting pixel, corrects the image data sequentially input by the luminance adjustment unit to correct the luminance of the abnormal light emitting pixel, and the luminance adjustment unit The abnormal light emission luminance is made difficult to visually recognize as compared with the case where the luminance of the abnormal light emission pixel is not corrected.

  The invention of claim 7 includes a display unit in which pixels are arranged in a matrix, and a drive unit that drives the pixels arranged in the display unit in accordance with image data and displays a desired image on the display unit. This is applied to the driving method of the image display device. The luminance of abnormal light emitting pixels is corrected by correcting sequentially input image data, and the abnormal light emission luminance is made difficult to visually recognize compared with the case where the luminance of abnormal light emitting pixels is not corrected.

  According to the configuration of claim 1 or claim 7, the luminance of abnormal light emitting pixels is corrected by correcting sequentially input image data, and the abnormal light emitting luminance is increased as compared with the case where the luminance of abnormal light emitting pixels is not corrected. By making it difficult to visually recognize, it is possible to make it difficult to recognize abnormal luminescent pixels as dark spots and bright spots, and as a result, it is possible to reduce image quality deterioration due to abnormal luminescent pixels.

  According to the present invention, it is possible to reduce image quality deterioration due to abnormal light emitting pixels whose light emission luminance is significantly different from that of normal pixels.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate. The description will be given in the following order.
1. First Embodiment 2. FIG. Second Embodiment 3. FIG. Third embodiment 4. 4. Fourth embodiment Fifth Embodiment Sixth Embodiment Modification <First Embodiment>
[Configuration of the embodiment]
FIG. 1 is a block diagram showing an image display apparatus according to the first embodiment of the present invention in comparison with FIG. In the image display device 21, the configuration of FIG. 7 or FIG. 8 is applied to the display unit 2. The drive circuit 22 corrects the sequentially input image data D1 by the luminance adjustment calculation circuit 23, and then generates a drive current or drive voltage by the configuration of the drive circuit 3 described above with reference to FIG. 7 or FIG. To drive.

  The pixel brightness adjustment information unit 24 is configured by a memory, and stores and holds address information and brightness adjustment amount information that are position information of abnormal light emitting pixels. The luminance adjustment calculation circuit 23 corrects the image data D1 based on the information stored in the pixel luminance adjustment information unit 24, and corrects the light emission luminance of the abnormal light emission pixel. The pixel brightness adjustment information unit 24 is set with information on the address and the brightness adjustment amount in the final adjustment process in the manufacturing process.

  That is, the image display device 21 is driven with a constant drive current or drive voltage in the final adjustment step, and the light emission luminance of each pixel is measured. In addition, the abnormal emission pixel is detected by determining the measured emission luminance with a predetermined threshold value. This abnormal light emitting pixel may be detected only at a specific gradation or may be detected at a plurality of gradations. Here, when detecting only with a specific gradation, for example, an abnormal light emitting pixel is detected by causing each pixel to emit light with an intermediate gradation that is relatively easy to visually recognize as a dark spot and a bright spot. In addition, in the case of detecting with a plurality of gradations, for example, after detecting each pixel by emitting light at a high luminance level at which abnormally luminescent pixels are easily visible as dark spots, the low luminance that is more likely to be visually recognized as abnormal luminescent pixels. Each level is detected by causing each pixel to emit light.

  Here, when one specific pixel on the display screen is darker than the peripheral pixel by a certain value or more, the human eye recognizes this specific pixel almost equivalent to a dark spot. On the other hand, when a specific pixel on the display screen is brighter than a peripheral pixel by a certain value, the specific pixel is recognized almost equally as a bright spot. It can be said that this constant value is approximately 30% of the light emission luminance of the normal pixel due to the characteristics of the human eye. Accordingly, when the light emission luminance of a normal pixel is set to value 1, a pixel whose light emission luminance is in the range of 0.7 to 1.3 is not recognized as a dark spot or a bright spot.

  Therefore, in this final adjustment step, when the light emission luminance of the normal pixel is set to the value 1, at least a pixel whose light emission luminance does not fall within the value range of 0.7 to 1.3 is detected as an abnormal light emission pixel. Note that the light emission luminance of the normal pixel is obtained by, for example, detecting the average value of the light emission luminance by causing a plurality of pixels to emit light based on the light emission luminance at the time of detecting the abnormal pixel.

  In the final adjustment step, the detected address of the abnormal light emitting pixel is stored in the pixel luminance adjustment information unit 24. Also, information on the brightness adjustment amount is created from the light emission luminance of the abnormal light emitting pixel detected at the time of detecting the abnormal light emitting pixel, and stored in the pixel luminance adjustment information unit 24.

  Here, the luminance of the abnormal light emitting pixel when the luminance adjustment arithmetic circuit 23 does not adjust the luminance is L (before adjustment), and the luminance of the abnormal light emitting pixel when the luminance adjustment arithmetic circuit 23 adjusts the luminance is L (after adjustment). . The luminance of normal pixels is L (normal). Here, the ratio of the emission luminance of the abnormal pixel to the emission luminance of the normal pixel is α (before adjustment) and α (when adjustment is not performed by the luminance adjustment calculation circuit 23 and when luminance adjustment is performed by the luminance adjustment calculation circuit 23, respectively. After adjustment). In this case, the following relational expression is established.

  Here, by adjusting the light emission luminance of the abnormal pixel so that α (after adjustment) = 1, the light emission luminance of the abnormal light emission pixel can be set to be completely the same as the light emission luminance of the normal pixel. However, in order to adjust the luminance by the luminance adjustment arithmetic circuit 23 so that α (after adjustment) = 1 at all gradations, the processing of the image data D1 in the luminance adjustment arithmetic circuit 23 becomes extremely complicated.

  On the other hand, as shown by the following equation, if the light emission luminance of the abnormal light emission pixel is corrected so as to approach the light emission luminance of the normal pixel, the dark spot and the bright point can be made less conspicuous than before the adjustment. A certain adjustment effect can be obtained.

  However, even if it is set so as to satisfy the relational expression (2), it may still be visually recognized as a dark spot or a bright spot. Therefore, in this embodiment, it is set so as to further satisfy the following relational expression.

  The human eye is set so as to satisfy the following relational expression because the visibility of green is the highest among the three primary colors of the color image. Here, α (after adjustment: GREEN), α (after adjustment: RED), and α (after adjustment: BLUE) are the emission luminances of abnormal pixels relative to the emission luminances of normal pixels in green, red, and blue sub-pixels, respectively. This is the ratio after the brightness adjustment.

  More specifically, in this embodiment, for the green sub-pixel, the image display device 21 emits the luminance L (before adjustment) of the abnormal light-emitting pixel detected when detecting the abnormal light-emitting pixel and the corresponding normal pixel. Is calculated from (emission luminance L (normal) −emission luminance L (before adjustment)) / emission luminance L (before adjustment). Thereby, the image display device 21 uses the light emission luminance L (before adjustment) as a reference for the light emission luminance correction amount for setting the adjusted ratio α (after adjustment) to the value 1 in the gradation at the time of detecting the abnormal light emission pixel. Detected. In the image display device 21, the light emission luminance correction amount is stored in the pixel luminance adjustment information unit 24 as a luminance adjustment amount. In this case, when detecting abnormal light emission pixels with a plurality of gradations, the light emission luminance correction amount having the largest correction amount from the light emission luminance correction amounts detected at each gradation is stored in the pixel luminance adjustment information unit 24. In the case where the average value is calculated and stored in the pixel luminance adjustment information unit 24, various setting methods can be applied as necessary.

  For the red and blue sub-pixels, after detecting the emission luminance correction amount in the same manner as the green sub-pixel, a predetermined weighting coefficient W (0 <W <) is satisfied so as to satisfy the relational expression (4). Weighted by 1) and stored in the pixel brightness adjustment information section 24.

  The luminance adjustment calculation circuit 23 calculates the correction amount by multiplying the image data D1 corresponding to the address stored in the pixel luminance adjustment information unit 24 by the corresponding luminance adjustment amount among the sequentially input image data D1. Then, the calculated correction amount is added to output the image data D1. The other image data D1 is output without any correction.

[Operation of the embodiment]
In the above configuration, the image data D1 sequentially input in the image display device 21 is converted into a drive current or drive voltage in the drive circuit 22, and the display unit 2 using the organic EL element is converted by the drive current or drive voltage. Driven. Accordingly, the image display device 21 can display an image based on the image data D1 on the display unit 2.

  However, in an organic EL element image display device, an abnormal light emitting pixel having a significantly different light emission luminance from a normal pixel is generated due to various factors. That is, the organic EL element locally changes the film thickness, film quality, etc. of the organic EL layer due to minute dust, contamination, etc. As a result, the driving voltage (voltage-current characteristics), luminous efficiency, etc. of the organic EL element are locally changed. May change. In the organic EL element, the light emission luminance L is expressed by L = Φ · I using the drive current I and the light emission efficiency Φ.

  Therefore, if the light emission efficiency changes locally, the light emission luminance changes locally, and if this change is significant, abnormal light emitting pixels are generated.

  Further, in the organic EL element, when the drive voltage (voltage / current characteristics) changes, the drive current changes and the light emission luminance changes. 7 and 8, since the organic EL element is driven at a constant current, it seems that the light emission luminance does not change depending on the change in the voltage-current characteristics of the organic EL element. However, in the pixel circuit 16 of FIG. 8, for example, the terminal voltage of the organic EL element changes due to the load fluctuation (voltage-current characteristic fluctuation) of the organic EL element, and the change in the drive current cannot be avoided in response to the change in the terminal voltage. . Accordingly, it can be said that the pixel circuit 16 does not have a sufficient constant current characteristic. In the constant current driving in the case where the pixel circuit 16 does not have a sufficient constant current characteristic, light emission is caused by a change in the voltage current characteristic of the organic EL element. The brightness changes. Accordingly, also in this case, abnormal light emission pixels are generated when the change in the light emission luminance is significant.

  In the pixel circuit 16 of FIG. 8, the drive current Ioled of the organic EL element is expressed by the following equation. Here, Vth is the threshold voltage of the drive transistor Tr1, μ is the mobility of the drive transistor Tr1, and W and L are the gate width and gate length of the drive transistor Tr1. Cox is a gate capacitance per unit area of the driving transistor Tr1.

  Accordingly, when the threshold voltage Vth and mobility μ of the driving transistor change due to minute dust, contamination, etc., the light emission luminance of the organic EL element also changes in this case. Accordingly, also in this case, abnormal light emission pixels are generated when the change in the light emission luminance is significant.

  Further, in the pixel circuit 16, when a leakage current is generated in the writing transistor Tr2 and the storage capacitor Cs due to minute dust and contamination, it becomes difficult to correctly set and hold the drive voltage Vsig in the storage capacitor Cs. The light emission luminance will change. Accordingly, also in this case, abnormal light emission pixels are generated when the change in the light emission luminance is significant.

  As described above, the abnormal light emitting pixel whose light emission luminance is remarkably different from that of the normal pixel is generally visually recognized in the same manner as the dark spot and the bright point, and the image quality is remarkably deteriorated.

  Therefore, in this image display device 21, abnormal light-emitting pixels that are recognized as dark spots and bright spots are detected in the manufacturing process. Further, information on the abnormal light emitting pixel address and the luminance adjustment amount for adjusting the light emission luminance of the abnormal light emitting pixel are stored in the pixel luminance adjustment information section 24. In the image display device 21, the image data D1 of the abnormal light emission pixel is detected from the image data D1 that is sequentially input according to the address stored in the pixel luminance adjustment information section 24. Further, the detected image data D1 of the abnormal light emission pixel is corrected by the corresponding luminance adjustment amount stored in the pixel luminance adjustment information unit 24, and thereby the light emission luminance of the abnormal light emission pixel is corrected.

  In the image display device 21, the correction of the light emission luminance of the abnormal light emission pixel is executed so as to approach the light emission luminance of the normal pixel (Equation (2)), thereby reducing image quality deterioration due to the abnormal light emission pixel.

  More specifically, the luminance adjustment amount is set so that the light emission luminance of the abnormal light emission pixel at the time of expressing the specific gradation matches the light emission luminance of the corresponding normal pixel so as to satisfy the relational expression (3). In addition, the light emission luminance of the abnormal light emission pixel is adjusted. Thereby, in the image display device 21, abnormal light emitting pixels can be prevented from being visually recognized as dark spots and bright spots, and image quality deterioration due to abnormal light emitting pixels can be reduced.

  Further, by reducing the luminance adjustment amount in the red and blue sub-pixels compared to the green sub-pixel, it is possible to effectively use human visual characteristics and reduce image quality degradation due to abnormal light-emitting pixels.

[Effect of the first embodiment]
According to the above configuration, it is possible to reduce image quality deterioration due to abnormal light emission pixels by correcting the light emission luminance of abnormal light emission pixels so as to approach the light emission luminance of normal pixels. Therefore, the yield of the image display device can be improved and the image quality can be improved.

  More specifically, when the emission luminance corresponding to the normal pixel is set to the value 1, the abnormal emission pixel is destroyed by setting the emission luminance of the abnormal emission pixel to be within the range of 0.7 to 1.3. It is possible to prevent the image from being visually recognized as a point or a bright point, and to reduce image quality deterioration due to an abnormal light emitting pixel.

  Further, by reducing the luminance adjustment amount in the red and blue sub-pixels compared to the green sub-pixel, it is possible to effectively use human visual characteristics and reduce image quality degradation due to abnormal light-emitting pixels.

<Second Embodiment>
FIG. 2 is a connection diagram showing a pixel circuit applied to the image display device according to the second embodiment of the present invention. The image display device of this embodiment is configured in the same manner as the image display device of FIG. 1 except that the configuration relating to the pixel circuit 36 is different.

  Here, in the pixel circuit 36, the cathode of the organic EL element OLED is held at a predetermined voltage Vss1, and the anode of the organic EL element OLED is connected to the source of the drive transistor Tr1. The driving transistor Tr1 has a drain connected to the scanning line, and a driving signal VSCAN2 (i) is supplied through the scanning line. Note that the transistor Tr1 is an N-channel transistor. Coled is a capacity of the organic EL element OLED, and Csub is an additional capacity in parallel with the capacity Coled of the organic EL element OLED. As a result, the pixel circuit 36 current-drives the organic EL element OLED with a drive current corresponding to the gate-source voltage of the drive transistor Tr1 by supplying power according to the drive signal VSCAN2 (i).

  In the pixel circuit 36, a holding capacitor Cs that holds a gate-source voltage of the driving transistor Tr1 is connected to a gate and a source of the driving transistor Tr1. Thereby, as shown in FIG. 3, the pixel circuit 36 supplies power to the drive transistor Tr1 by the drive signal VSCAN2 (i) during the light emission period in which the organic EL element OLED emits light (indicated by “light emission” in FIG. 3). Vddv2 is supplied (FIG. 3B), and the organic EL element OLED is driven by the drive transistor Tr1 with a drive current according to the voltage across the storage capacitor Cs (FIGS. 3D to 3F).

  In the pixel circuit 36, the gate-side end of the storage capacitor Cs is connected to the signal line via the write transistor Tr2 that is turned on / off by the write signal VSCAN1 (i) supplied via the scanning line. Note that the write transistor Tr2 is an N-channel transistor. The pixel circuit 36 alternately outputs a predetermined fixed voltage Vofs and a driving voltage Vsig (= Vofs + Vdata) (FIG. 3C).

  In the pixel circuit 36, the transistor Tr2 is kept off in the light emission period (FIG. 3A). In the pixel circuit 36, when the light emission period ends and the non-light emission period starts, the drive signal VSCAN2 (i) is set to the predetermined voltage Vssv2. Here, the voltage Vssv2 is a voltage that is sufficiently low to cause the source of the driving transistor Tr1 to function as a drain. Thus, when the non-light emission period starts, the pixel circuit 36 discharges the accumulated charge of the organic EL element OLED via the driving transistor Tr1, the anode voltage of the organic EL element OLED falls, and the organic EL element OLED stops emitting light. (FIGS. 3D and 3E). Further, the source side end of the storage capacitor Cs is set to the voltage Vssv2 and is set to a sufficiently low voltage.

  Subsequently, in the pixel circuit 36, the writing transistor Tr2 is set to the on state and the voltage at the gate side end of the storage capacitor Cs is set to the voltage Vofs during the period in which the signal line is set to the voltage Vofs (FIG. 5). 3 (A)). Thereby, in the pixel circuit 36, the voltage across the storage capacitor Cs is set to the voltage Vofs−Vssv2. Here, in the pixel circuit 36, the voltages Vofs and Vssv2 are set so that the voltage Vofs−Vssv2 is sufficiently larger than the threshold voltage Vth of the driving transistor Tr1 (FIGS. 3D and 3E). ).

  In the pixel circuit 36, the drive signal VSCAN2 (i) is then set to the power supply voltage Vddv2 (FIG. 3B). Thus, in the pixel circuit 36, the current corresponding to the voltage across the holding capacitor Cs flows into the organic EL element OLED via the driving transistor Tr1 in a state where the gate side end of the holding capacitor Cs is held at the voltage Vofs. As a result, the pixel circuit 36 gradually decreases the voltage across the storage capacitor Cs due to this current, and when the voltage across the storage capacitor Cs reaches the threshold voltage Vth of the drive transistor Tr1, the current from the drive transistor Tr1. Inflow stops, and the decrease of the voltage across the storage capacitor Cs stops (FIGS. 3E and 3F).

  As a result, in the pixel circuit 36, the voltage across the storage capacitor Cs is discharged via the drive transistor Tr1, and the voltage across the storage capacitor Cs is set to the threshold voltage Vth of the drive transistor Tr1. As a result, the pixel circuit 36 executes processing for preventing image quality degradation due to variations in threshold voltage of the drive transistor Tr1. This process is indicated by “Vt complement” in FIG. In addition, after the start of the non-light-emission period, a preparation process for executing this “Vt complement” process is executed during a period until the drive signal VSCAN2 (i) is raised to the power supply voltage Vddv2. This preparation process is indicated by “preparation” in FIG.

  Subsequently, in the pixel circuit 36, after the writing transistor Tr2 is set to the off state, the writing transistor Tr2 is set to the on state for a predetermined period in a period in which the signal line is set to the drive voltage Vsig. . Here, the drive voltage Vsig is a voltage obtained by adding the voltage Vofs to the voltage Vdata obtained by subjecting the corresponding image data D1 to digital-analog conversion processing. As a result, the pixel circuit 36 sets the light emission luminance of the organic EL element OLED as indicated by “write” in FIG.

  In the pixel circuit 36, when a certain time elapses, the writing transistor Tr2 is set to an off state (FIG. 3A). As a result, the pixel circuit 36 discharges the voltage across the storage capacitor Cs by the current of the drive transistor Tr1 for a fixed time in a state where the voltage at the gate side end of the storage capacitor Cs is held at the drive voltage Vsig. Here, the discharge rate of the voltage across the storage capacitor Cs increases as the mobility of the drive transistor Tr1 increases. Thus, the pixel circuit 36 corrects the variation in mobility of the drive transistor Tr1 as indicated by “μ complement” in FIG.

  The pixel circuit 36 starts a light emission period when the writing transistor Tr2 is set to an off state for correcting the mobility, and functions as a so-called bootstrap circuit to increase the gate voltage Vg and the source voltage Vs of the driving transistor Tr1. (FIGS. 3E and 3F).

  In this image display device, each pixel circuit 36 can correct variations in threshold voltage and mobility in the drive transistor Tr1. Therefore, it is possible to prevent image quality deterioration due to variations in threshold voltage and mobility.

  However, in this image display device, in each pixel circuit 36, the gray level of the organic EL element OLED is set by setting the voltage across the storage capacitor Cs using the capacitance Coled of the organic EL element OLED. Therefore, in this image display apparatus, in addition to the factors described above with respect to the first embodiment, abnormal light emitting pixels are also generated due to a leakage current of the organic EL element OLED, a change in the capacitance Ccoled, and the like.

  Therefore, in this image display device, the address and brightness adjustment amount information is stored in the pixel brightness adjustment information section 24 in the same manner as the image display device of the first embodiment, and the abnormal light emitting pixel is determined by the address and brightness adjustment amount information. The light emission luminance of the abnormal light emitting pixel is corrected by correcting the image data D1.

  In this embodiment, even when the gradation is set by using the capacitance of the organic EL element, and even when the threshold voltage variation and mobility variation of the driving transistor are corrected, the first embodiment is performed. The same effect as the form can be obtained.

<Third Embodiment>
In the image display device according to the third embodiment, the organic EL element is driven at a constant voltage, and the light emission time of the organic EL element is varied by a time modulation method to express gradation. Therefore, the pixel circuit of the image display device according to this embodiment includes a storage capacitor that holds the drive voltage set in the signal line, and a control that controls the light emission time of the organic EL element in accordance with the terminal voltage set in the storage capacitor. It is composed of a circuit or the like. The control circuit includes an integration circuit that reduces the terminal voltage set in the storage capacitor at a constant rate, a comparison circuit that determines the terminal voltage of the storage capacitor and controls driving of the organic EL element, and the like.

  In this image display device, the address and brightness adjustment amount information is stored in the pixel brightness adjustment information section in the same manner as the image display device of the first embodiment, and the image of the abnormal light emitting pixel is determined by the address and brightness adjustment amount information. Correct the data. As a result, this image display apparatus corrects the light emission luminance of the abnormal light emission pixel by correcting the light emission luminance of the abnormal light emission pixel different from the normal pixel by changing the light emission time.

  According to this example, even when the organic EL element is driven by a constant voltage and the gradation is expressed by the time modulation method, the same effect as that of the first embodiment can be obtained.

<Fourth embodiment>
The image display device according to the fourth embodiment stores information on the luminance adjustment amount in the pixel luminance adjustment information unit for all the pixels constituting the display unit, thereby correcting the emission luminance of the abnormal light emitting pixel, and At the same time, the shading is corrected. The image display apparatus according to this embodiment is configured in the same manner as the first to third embodiments except that the configuration relating to the pixel luminance adjustment information unit is different.

  Even if the configuration for correcting the light emission luminance of the abnormal light emitting pixel is also used as the configuration for shading correction as in this embodiment, the same effects as those in the first to third embodiments can be obtained.

<Fifth embodiment>
FIG. 4 is a block diagram showing an image display apparatus according to the fifth embodiment of the present invention. The image display device 41 is an image display according to the first to fourth embodiments except that a pixel brightness adjustment information unit 44 and a drive circuit 42 are provided instead of the pixel brightness adjustment information unit 24 and the drive circuit 22. The same configuration as the device. The drive circuit 42 is configured in the same manner as the drive circuit 22 except that a luminance adjustment calculation circuit 43 is provided instead of the luminance adjustment calculation circuit 23.

  Here, the pixel luminance adjustment information unit 44 detects the luminance adjustment amounts at the luminance levels of 100% and 10% as in the first embodiment, and this luminance adjustment amount for each abnormal light emitting pixel. Is recorded. The luminance adjustment calculation circuit 43 obtains the luminance adjustment amount for the gradation of the abnormal light emitting pixel by linear interpolation using the information on the luminance adjustment amount recorded in the pixel luminance adjustment information unit 44. Further, the light emission luminance of the corresponding abnormal light emitting pixel is corrected by the obtained luminance adjustment amount. Note that various calculation methods can be applied, for example, in the case where the brightness adjustment amount is calculated by an interpolation calculation process using a quadratic function instead of the calculation process by linear interpolation. In this case, as indicated by parentheses, a function used for interpolation calculation processing may be recorded.

  According to this embodiment, the abnormality adjustment is performed more appropriately by calculating the luminance adjustment amount for the gradation of the abnormal light emitting pixel and correcting the light emission luminance by the interpolation process using the luminance adjustment amounts obtained for a plurality of gradations. The light emission luminance of the light emitting pixels can be corrected to further improve the image quality degradation.

  That is, the abnormal light emitting pixel is generated due to the various generation factors described above. Therefore, the characteristics required for correction differ depending on the generation factor. As a result, simply creating a correction value by multiplying the brightness correction amount does not necessarily prevent the occurrence of dark spots and bright spots for abnormal light emitting pixels due to all gradations and all occurrence factors. .

  However, if the luminance adjustment amount is detected and recorded in a plurality of gradations as in this embodiment, and the emission luminance of the abnormal light emitting pixel is corrected by interpolation calculation processing of the luminance adjustment amount, the correction accuracy is further improved. Image quality can be improved.

<Sixth Embodiment>
FIG. 5 is a block diagram showing an image display apparatus according to the sixth embodiment of the present invention. The image display device 51 is the same as the image display device 41 of the fifth embodiment except that a pixel luminance adjustment information unit 54 and a drive circuit 52 are provided instead of the pixel luminance adjustment information unit 44 and the drive circuit 42. Configured identically. The drive circuit 52 is configured in the same manner as the drive circuit 42 except that a brightness adjustment calculation circuit 53 is provided instead of the brightness adjustment calculation circuit 43.

  In this image display device, in the same manner as in the first embodiment, the brightness adjustment amount is detected at each of a plurality of gradations, and the characteristics used for correction based on the detection result of the brightness adjustment amount for each abnormal light emitting pixel. Are classified.

  Specifically, as shown in the equation (5), it is necessary for the abnormal light emitting pixel due to the variation in the threshold voltage Vth of the driving transistor Tr1 to calculate the correction amount based on the characteristic of the quadratic function. On the other hand, an abnormal light emitting pixel due to variation in mobility μ needs to calculate a correction amount based on a characteristic of a linear function. In the image display device 51, the characteristics used for correction are detected and classified from the brightness adjustment amounts detected at a plurality of gradations of the abnormal light emitting pixels, and the correction mode is set. The correction mode is stored in the pixel luminance adjustment information unit 54 together with information on the luminance adjustment amount at the specific light emission luminance. The correction function for each correction mode is stored in the pixel luminance adjustment information section 54.

  For each correction mode stored in the pixel brightness adjustment information unit 54, the brightness adjustment calculation circuit 53 corrects the light emission brightness of the abnormal light emission pixel by a calculation process using a corresponding correction function.

According to this embodiment, characteristics to be used for luminance correction are classified and recorded, and a correction function is selected for each classification to correct the emission luminance of the abnormal light emitting pixel, thereby further appropriately emitting light from the abnormal light emitting pixel. Luminance can be corrected to further improve image quality degradation.
<Modification>
In the above-described embodiment, the case where the luminance of the abnormal light emitting pixel is corrected so as to satisfy the relational expressions (3) and (4) has been described. However, the present invention is not limited to this, and when a practically sufficient image quality can be ensured, the relational expression (1) is simply satisfied, or the relational expression (3) is satisfied. May be set.

  In the above-described embodiment, the case where the present invention is applied to an active matrix image display device using an organic EL element has been described. However, the present invention is not limited to this, and can be widely applied to a passive matrix type image display apparatus using organic EL elements, an image display apparatus using light emitting elements other than organic EL elements, and the like.

  The present invention can be applied to an image display device using an organic EL element.

1 is a block diagram illustrating an image display device according to a first embodiment of the present invention. It is a connection diagram which shows the pixel circuit applied to the image display apparatus of the 2nd Embodiment of this invention. 3 is a time chart for explaining the operation of the pixel circuit of FIG. 2. It is a block diagram which shows the image display apparatus of the 5th Embodiment of this invention. It is a block diagram which shows the image display apparatus of the 6th Embodiment of this invention. It is a block diagram which shows the conventional image display apparatus. It is a connection diagram showing a passive matrix type image display device. It is a connection diagram showing an active matrix type image display device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 5, 11, 21, 41, 51 ... Image display apparatus, 2 ... Display part, 3, 22, 42, 52 ... Drive circuit, 16, 36 ... Pixel circuit, 23, 43, 53 ... Luminance adjustment arithmetic circuit, 24, 44, 54... Pixel luminance adjustment information section, Cs... Holding capacitor, Tr1, Tr2.

Claims (7)

A display unit in which pixels are arranged in a matrix, and
Driving the pixels arranged in the display unit according to image data, and displaying a desired image on the display unit,
The drive unit is
It has a brightness adjustment unit that corrects the brightness of abnormal light emitting pixels,
The luminance data is sequentially input by the luminance adjusting unit to correct the luminance of the abnormal light emitting pixels, and the abnormal light emitting luminance is visually recognized as compared with the case where the luminance adjusting unit does not correct the luminance of the abnormal light emitting pixels. Image display device to make difficult. The brightness adjusting unit is
The image display device according to claim 1, wherein the luminance of the abnormal pixel is corrected to a luminance in a range of a value of 1.3 to a value of 0.7 when a luminance of a normal pixel having a corresponding gradation is set to a value of 1. A pixel luminance information section for holding at least position information of the abnormal light emitting pixel and information on a correction amount for correcting the luminance of the abnormal light emitting pixel;
The brightness adjusting unit is
The image display device according to claim 2, wherein luminance of the abnormal light emitting pixel is corrected based on the position information and the correction amount information. The information on the correction amount is information on the correction luminance amount of the abnormal light emitting pixel in a specific gradation,
The brightness adjusting unit is
The image display device according to claim 3, wherein a correction amount in a gradation of the abnormal light emitting pixel is obtained based on the information on the correction luminance amount, and the luminance of the abnormal light emitting pixel is corrected. The information on the correction luminance amount is information on the correction amount detected at a plurality of gradations of the abnormal light emitting pixel,
The brightness adjusting unit is
The image display apparatus according to claim 4, wherein a correction amount in luminance of a corresponding abnormal light emitting pixel is obtained from correction amounts detected in the plurality of gradations, and the luminance of the abnormal light emitting pixel is corrected. The information on the correction amount is information on the correction luminance amount of the abnormal light emitting pixel in a specific gradation and information on a correction mode that defines a function used for calculating the correction amount.
The brightness adjusting unit is
The image display device according to claim 3, wherein a correction amount in the luminance of the corresponding abnormal light emitting pixel is obtained from information on the correction luminance amount using a function corresponding to the correction mode, and the luminance of the abnormal light emitting pixel is corrected. . A display unit in which pixels are arranged in a matrix, and
In a driving method of an image display device having a drive unit that drives pixels arranged in the display unit according to image data and displays a desired image on the display unit,
A method for driving an image display device, wherein image data that is sequentially input is corrected to correct the luminance of abnormal light emitting pixels, and the abnormal light emitting luminance is less visible than when the abnormal light emitting pixels are not corrected.

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