Patent Application
20090102853
The present invention relates to a display apparatus and an active matrix apparatus which arrange pixels or pixel circuits which have electro-optical elements in a matrix.
Recently, display units and the like which use electro-optical elements attract attention as next-generation display units. Here, an organic electroluminescence (EL) element which is a current control type light emitting element in which emission luminance is controlled by a current which flows into the element will be cited as an example, and will be described.
In an organic EL display apparatus including a peripheral circuit, thin-film transistors (TFTs) are used not only in a display region but also in the peripheral circuit. Image display panels which use EL elements which are such self-emission type optical elements for image display elements, and which use TFTs in a display region and a peripheral circuit are known by U.S. Pat. No. 7,126,565 and U.S. Patent Laid-Open No. 2004-0183752.
Video signals input into the above-mentioned image display panels are analog video signals into which digital color video signals of three colors of red (R), green (G), and blue (B) are converted by digital-to-analog converters (DACs). Alternatively, after converting a digital luminance signal and digital color difference signals into digital color video signals in three colors of RGB, they are analog video signals converted by digital-to-analog converters (DACs).
In this case, although three DACs are needed, and the DACs are made into an integrated circuit using single-crystal silicon, the three DACs have characteristic dispersion.
The present inventor found out that there was a possibility that this characteristic dispersion among DACs might have display non-uniformity of a pattern fixed in a display panel, and might be visualized.
An object of the present invention is to provide a color display apparatus and an active matrix apparatus which can decrease the display non-uniformity by the characteristic dispersion of DACs.
The gist of the present invention is a color display apparatus comprising:
a display unit comprising electro-optical elements which are arranged in a matrix in a row direction and a column direction and classified by color of emitted light, scanning lines which are provided in respective rows of the electro-optical elements arranged in a matrix, and select respective rows in a time sharing manner, and data lines which are equally provided in respective columns and supply data signals to electro-optical elements in the rows which the scanning lines select;
conversion circuits into which video signals for each color which classify the electro-optical elements are input, and convert and output the input video signals to other video signals;
a first dispersion circuit for changing sequence of the converted video signals outputted from the conversion circuits, and for outputting the converted video signals to the same number of bus lines;
column drive circuits which sample the signals in the bus lines in the time sharing manner, and generate and output the data signals; and
a second dispersion circuit for returning the sequence of the converted video signals changed by the first dispersion circuit into an original sequence, in relation to the outputs of the column drive circuits, and for outputting to the data lines the converted video signals of which sequence is returned.
The second gist of the present invention is an active matrix apparatus which has a matrix unit in which a plurality of pixel circuits is arranged in a matrix, a plurality of data lines connected to the matrix unit commonly every column, and a plurality of column drive circuits which is provided with corresponding to columns of the matrix unit, and which outputs data signals supplied to the pixel circuits for every row, to the plurality of data lines, characterized by having:
a first dispersion circuit for selecting the column drive circuits used as output destinations of analog video signals for each color obtained by DA converting digital video signals for every color;
a second dispersion circuit for selecting the data lines used as output destinations of the data signals from the column drive circuits; and
control lines which control the first and second dispersion circuits so as to sequentially change the drive circuits used as output destinations of the analog video signals for each color, and the data lines used as output destinations of the data signals, for every scanning period.
The present invention has such construction of supplying outputs to pixels or pixel circuits with sequentially changing data lines of output destinations of column drive circuits. In this way, it can be performed to average temporally dispersion of values of currents supplied to pixels or pixel circuits, and in other words, to disperse them spatially. Therefore, it can be performed to reduce non-uniformity of a display image such as a vertical line, which appears on a screen, visually. In addition, it can be performed to reduce visually the non-uniformity of a display image with a fixed pattern each predetermined row caused by the characteristic dispersion among DACs, by the dispersion circuit which changes output destinations from the DACs. Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Reference numeral 14 denotes a plurality (3N lines) of data lines which is connected to the pixel circuits 2 commonly for every column and is provided, reference numeral 20 denotes a plurality (M lines) of row selection lines provided for every row. The peripheral circuit is equipped with column drive circuits 1, column shift registers 3, row shift registers 5, a gate circuit 4, and second dispersion circuits 34. Digital video data Video is processed by a signal processing circuit 32, and is supplied to DACs in the signal processing circuit. Analog video signals for each color from DACs are input into column drive circuits 1 through a first dispersion circuit 13 in this signal processing circuit.
Each transistor in each circuit of the display panel 100 is constructed of a TFT which has an active layer of a non-monocrystalline semiconductor, such as a polysilicon. In addition, each transistor in the signal processing circuit 32 and a control circuit 35 is constructed of a transistor whose active layer is a monocrystalline semiconductor, such as single-crystal silicon.
The control circuit 35 may be integrated in the signal processing circuit 32.
In
First, at the time before time t0, a signal in a Low level is input into the scan signal P1 in the pixel circuits 2 of the object row and a signal in a High level is input into P2, and a transistor M2 is OFF, M3 is OFF, and M4 is ON. In these states, I (m−1) corresponding to the one-previous row of current data Idata is not input into the pixel circuits 2 of the m-th row which is the target row.
Subsequently, at time t0, a signal in a High level is input into P1 and a signal in a Low level is input into P2, and, transistors M2 and M3 become ON, and M4 becomes OFF. In these states, I(m) corresponding to the target row of current data Idata is input into the pixel circuits 2 of the m-th row which is the target row. Since M4 is not conductive at this time, a current does not flow in an EL element. A voltage according to the current driving capability of M1 occurs in a capacity C1, which is arranged between a gate terminal of M1, and a power supply potential VCC, by the input Idata. Thus, current-voltage conversion is once performed in the pixel circuit.
In the above explanation, although an active matrix display apparatus is cited and explained as an example, as a display unit (matrix unit) used in the present invention, a passive matrix where electro-optical elements are arranged at intersections of a plurality of data lines and a plurality of row selection lines may be used.
A column drive circuit used in the present invention is illustrated in
This circuit is the same as the column drive circuit described in U.S. Pat. No. 7,126,565. Refer to the above-mentioned document for detailed explanation.
This drive circuit is constructed of a pair of voltage-current conversion circuits, and explains their main operations. A switching transistor M6 is turned off, a switching transistor M10 is turned on, and a drain current of a voltage-current converting transistor M9 is output to an output line idata. At this time, a switching transistor M1 turns on by a sampling signal SPA, and an analog video signal voltage VIDEO is stored as a gate voltage of another voltage-current converting transistor M3. Thereby, the transistor M3 becomes in a state that a predetermined drain current can be flowed.
Next, the switching transistor M6 turns on, the switching transistor M10 turns off, and a drain current of the transistor M3 is output to the output line idata. At this time, a switching transistor M7 turns on by the sampling signal SPA again, and the analog video signal voltage VIDEO which is taken in is stored as a gate voltage of the transistor M9. Thereby, the transistor M9 becomes in a state that a drain current can be flowed.
The above two operations are repeated each row scanning period, and an analog signal current is output to the output line idata one by one. Let a write voltage V of a gate of the transistor M3 and a gate of the transistor M9 by effective amplitude of the analog video signal voltage VIDEO, and drive factors β of the transistors M3 and M9 be A and B, respectively.
A drain current i(M3) of the transistor M3 and a drain current i(M9) of the transistor M9 fulfill the following relations.
i(M3)=A×V2
i(M9)=B×V2
A drive factor of each voltage current conversion circuit is determined by a capacitance split ratio of capacitors C1 (or C3) and C2 (or C4). In addition, at the same time, it is also determined by a gate width to a gate length (W/L) of the voltage-current converting transistor M3 (or M9).
Although a TFT in which a non-monocrystalline semiconductor used in each transistor is used in an active layer has large characteristic dispersion, it is not fundamentally affected by fluctuation of a threshold voltage Vth of the transistor M3 and transistor M6 of each column in the circuit construction of
An analog video signal voltage VIDEO1 input is input into a voltage-current conversion circuit (a pair of voltage-current conversion circuits same as that in
Three output lines of three column drive circuits 1 are input into a distributing switch unit (second dispersion circuit) 34 including three three-input/one-output switches, and are output to an R column, a G column, and a B column, to which they correspond respectively, as data signal currents iR, iG, and iB.
A distributing switch unit 34 changeably selects a data line 14 which becomes an output destination of a data signal from the column drive circuit. Although original video signals are exchanged by the first dispersion circuit mentioned later and are output to bus lines, the second dispersion circuit restores this exchange.
A control signal supplied to a control line Ps2 from the control circuit 35 can determine changeably a connection state of the distributing switch unit 34.
Then, three switches of the distributing switch unit 34 are controlled by the control signal supplied to the control line Ps2 so that they may interlock.
These digital video signals for respective colors are converted into analog video signals for respective colors by digital-to-analog converters DAC1, DAC2, and DAC3, respectively, and are input into the distributing switch unit 13, which is the first dispersion circuit, through a matrix wiring unit.
In the distributing switch unit 13, the analog video signal lines VIDEO1, VIDEO2, and VIDEO3, which are output destinations of respective DACs, are suitably selected by the control signal input into a control line Ps1. That is, the distributing switch unit 13 which constructs the first dispersion circuit exchanges three RGB lines of video signals input from the external, and outputs them to the bus lines (analog video signal line).
The control signal supplied to the control line Ps1 is generated in a control circuit which is not illustrated and is integrated inside the signal processing circuit 32. The control signal in the control line Ps1 can determine a connection state of the first dispersion circuit 13, that is, which of the analog video signal line VIDEO1, VIDEO2, and VIDEO3 becomes an output destination of a DAC. Then, this connection state can be changed.
Then, the first dispersion circuit 13 and the second dispersion circuit 34 are controlled by the control circuit 32 and the control circuit 35 so as to select a suitable connection state, mentioned later, with collaborating.
In the above explanation, a digital video signal for each color is converted into an analog video signal by a D/A-converter. When an original input video signal is analog, an analog amplifier or the like is used instead of a D/A-converter. What is necessary is that it is a circuit for driving bus lines with large capacity, such as a D/A-converter, or an analog amplifier.
Here, in order to make the operations and effects by the embodiments of the present invention easy to understand, a comparative example will be explained first.
A case that the construction illustrated in
Digital video data PIC1, PIC2, and PIC3 which are input are input into the DSP 12. The digital video data PIC1, PIC2, and PIC3 may be RGB data or YUV data. The DSP 12 which performs video signal processing outputs digital video signals Rdat, Gdat, and Bdat for each color corresponding to a display apparatus from the digital video data PIC1, PIC2, and PIC3.
For that purpose, the DSP 12 performs color space transformation (unnecessary when digital video signals input are RGB data) if needed. At least one kind of processing selected from resolution conversion, edge enhancement, noise reduction, gamma correction, white balance, black setting, luminance setting, and the like other than this is performed by digital signal processing in the DSP 12.
The digital video signals Rdat, Gdat, and Bdat for each color are input into the DAC1, DAC2, and DAC3 with a gain k through the distributing switch unit 13, respectively. Then, they are converted into the analog video signals VIDEO1, VIDEO2, and VIDEO3 by the DAC1, DAC2, and DAC3 and are output.
A generating operation of signal currents for corresponding to displaying respective RGB which is performed from the column drive circuit in
Each color data input into each DAC by the distributing switch unit 13 in
On the other hand, the drive factors of the column drive circuit selected by the distributing switch unit 34 in
As mentioned above, since a current output from the column drive circuit in
The figures in the left end of
Nevertheless, there is dispersion among respective gains of digital-to-analog converters DAC1, DAC2, and DAC3 in
As is evident from
One embodiment of the present invention uses construction illustrated in
Color signals output to video signal outputs VIDEO1, VIDEO2, and VIDEO3 by the distributing switch unit 13 in
As is evident from Tables 3 and 2, similarly to a case that the construction in
The figures in the left end of
Therefore, the display non-uniformity of the fixed pattern in every three lines which is caused by the gain dispersion among the DAC1, DAC2, and DAC3 is not generated.
Surely, although white balance shifts by the gain dispersion among the DAC1, DAC2, and DAC3, the white balance can be easily adjusted by a widely known method by digital processing in the DSP 12.
Hence, when the signal processing circuit 32 in
Without providing a first dispersion circuit, on a substrate which has the same insulating surface as that of a display unit, the first dispersion circuit 13 is provided in the signal processing circuit in
As illustrated in
As illustrated in
These first and second dispersion circuits are controlled by the control lines Ps1 and Ps2.
As is evident from Tables 3 and 2, similarly to the first embodiment, data signal currents of desired colors are supplied to the data lines of RGB columns in all the selected states of the distributing switch units 34 and 13.
As illustrated in
Since the distributing switch unit 13 can be arranged over full width of horizontal size of a display screen on a display panel, dispersion among conductive resistances of respective switches in the distributing switch unit 13 can be suppressed as much as possible. Then, it can be performed to balance a sampling operation affected by a sampling time constant in each column drive circuit.
In addition, although one switch for dispersion is provided to one row of data line in
Furthermore, it is needless to say that it can be also performed to prevent the dispersion among the drive factors A1, B2, A3, B1, A2, and B3 of the voltage-current conversion circuits from appearing as much as possible in display image quality similarly to the first embodiment.
This application claims the benefit of Japanese Patent Application No. 2006-097998, filed Mar. 31, 2006 which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-097998 | Mar 2006 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2007/057690 | 3/30/2007 | WO | 00 | 2/8/2008 |
