JP2002215106A - Electro-optical device, electronic equipment, and projective display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To compensate for variation in a gradation characteristic caused by a leak current of pixel transistors in an electro-optical device such as a liquid crystal panel. SOLUTION: In the same process as that of the pixel transistors, a plurality of transistors 302,..., 302 for measurement are formed, and these are connected in parallel. Since a leak current Id1 approximately proportional to the leak current of the pixel transistors can be obtained from this parallel circuit, the gradation characteristic (a voltage to be applied to the pixel transistors) is corrected by a leakage correction circuit 314 based on the leak current Id1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electro-optical device, an electronic apparatus, and a projection display device suitable for displaying image information.

[0002]

2. Description of the Related Art Electro-optical devices, for example, liquid crystal display devices using liquid crystal as an electro-optical material, are widely used as display devices in place of cathode ray tubes (CRTs) for display sections of various information processing equipment and liquid crystal televisions. I have. Here, the conventional electro-optical device is configured as follows, for example. That is, a conventional electro-optical device includes an element substrate provided with pixel electrodes arranged in a matrix and a switching element such as a TFT (Thin Film Transistor) connected to the pixel electrodes;
A counter substrate on which a counter electrode facing the pixel electrode is formed,
A liquid crystal, which is an electro-optical material, is filled between these two substrates.

In such a configuration, when a scanning signal is applied to a switching element via a scanning line, the switching element becomes conductive. In this conductive state, when an image signal of a voltage corresponding to the gradation is applied to the pixel electrode via the data line, a charge corresponding to the voltage of the image signal is applied to the liquid crystal layer between the pixel electrode and the counter electrode. Stored. After the charge storage, even if the switching element is turned off, the charge storage in the liquid crystal layer is maintained by the capacitance of the liquid crystal layer itself, the storage capacitance, and the like. As described above, when the switching elements are driven and the amount of charge to be stored is controlled in accordance with the gradation, the alignment state of the liquid crystal changes for each pixel, so that light is modulated for each pixel and the displayed density changes. become. Therefore, it is possible to display gradation.

At this time, since it is sufficient that the charge is stored in the liquid crystal layer of each pixel in a part of the period for displaying one screen, first, the scanning line driving circuit uses
Each scanning line is sequentially selected, and during the selection period of the scanning line, secondly, the data lines are sequentially selected by the data line driving circuit, and thirdly, the selected data line is selected according to the gradation. The configuration for sampling the voltage image signal enables time-division multiplex driving in which the scanning lines and the data lines are shared by a plurality of pixels.

Thus, when attention is paid to each pixel, the voltage applied to the liquid crystal layer ideally becomes a square wave having a half cycle of a frame cycle necessary for displaying one screen. However, actually, since a leak current occurs in the TFT, the voltage applied to the liquid crystal layer does not form a perfect square wave, and its absolute value gradually decreases within a frame period.
For this reason, it is general that the voltage applied to the liquid crystal layer is corrected in advance in consideration of the influence of the leak current.

[0006]

However, since the leak current greatly varies depending on the illuminance of the light applied to the liquid crystal layer, and also varies with the aging of the TFT, the leak current is uniformly corrected. It is difficult. In particular, in a liquid crystal projector or the like, the illuminance on the liquid crystal panel is strong,
In addition, the brightness of the lamp changes according to the lamp temperature and the continuous lighting time, and the illuminance differs for each device.
Since the irradiation energy to the TFT is different for each color B (because the wavelength of light is different), the magnitude of the leak current of the TFT is different. Adjusting the tone characteristics in response to such various situations has been extremely complicated. A technique for automatically measuring the luminance of a lamp of a liquid crystal projector and correcting gradation characteristics is known (Japanese Patent Laid-Open No. 10-55030), but such a technique has a problem that it cannot cope with aging of a TFT or the like. . The present invention has been made in view of the above-described circumstances, and provides an electro-optical device, an electronic device, and a projection display device that can automatically correct gradation characteristics with respect to leakage current of a switching element such as a TFT. The purpose is.

[0007]

Means for Solving the Problems In order to solve the above problems, the present invention is characterized by having the following constitution. Note that the contents in parentheses are examples. In the configuration according to the first aspect, the plurality of pixel electrodes (118) disposed on the element substrate (101) and to which the pixel voltage is applied are brought into a conductive state during a selection period to reduce the pixel voltage. A switching element (116) for applying the voltage to the pixel electrode to be in a non-conductive state during a non-selection period, thereby holding the pixel voltage on the pixel electrode; and a switching element (116).
And a correction circuit (secondary gamma correction circuit 202) for correcting the pixel voltage according to the current flowing through the current source. In the configuration according to claim 2, the pixel voltage is applied to the pixel electrode by being placed on the element substrate and being in a conductive state during a selection period with the plurality of pixel electrodes to which the pixel voltage is applied. A switching element (116) for holding the pixel voltage on the pixel electrode by applying a non-conductive state during the non-selection period, a light shielding film (data line 114) for shielding the switching element from light irradiation,
A current source including a dummy element (302) of the switching element, and a correction circuit (secondary gamma correction circuit 202) that corrects the pixel voltage according to a current flowing through the current source. Furthermore, the configuration according to claim 3 is the electro-optical device according to claim 2, further comprising a light-shielding film (light-shielding line 382) that shields the dummy element from light irradiation. Claim 4
In the configuration described above, in the electro-optical device according to any one of claims 1 to 4, the current source includes a plurality of the dummy elements connected in parallel. Further, according to a fifth aspect of the present invention, in the electro-optical device according to the first to fourth aspects, the switching element comprises a TFT. Further, according to a sixth aspect of the present invention, in the electro-optical device according to the first to fifth aspects, the dummy element is manufactured in the same process as the switching element. Furthermore, in the configuration according to claim 7, in the electro-optical device according to claims 1 to 6, the current source is connected to a first line (360) provided on the element substrate (101). , A second line (36) disposed substantially parallel to the first line (360).
4), a third line (362) interposed between the first and second lines, and a plurality of dummy elements (302) formed on the third line (362). The first
Alternatively, one of the second lines and the third line (36
2), and a second lead (368,..., 368) connecting the first line (360) to the input terminals of the plurality of dummy elements.
And third lead wires (374,...) Connecting the second line (360) and the output terminals of the plurality of dummy elements.
, 374). An eighth aspect of the invention is characterized by including the electro-optical device according to any one of the first to seventh aspects. Also,
In a configuration according to claim 9, a light source (1431);
An optical modulator (100R, 1) for modulating light from the light source
00G, 100B) and a projection display device (1430) having a projection lens (1437) for projecting light modulated by the light modulation device, the light modulation device is disposed on an element substrate (101); A plurality of pixel electrodes (118) to which a pixel voltage is applied and a conductive state during a selection period, whereby the pixel voltage is applied to the pixel electrode;
The non-conductive state during the non-selection period causes the switching element (11) that holds the pixel voltage to the pixel electrode.
6), a light-shielding film (data line 114) for shielding the switching element from light irradiation, a current source including a dummy element (302) of the switching element, and a pixel voltage according to a current flowing through the current source. And a correction circuit (secondary gamma correction circuit 202) for performing correction.
Further, according to a tenth aspect of the invention, in the projection type display device according to the ninth aspect, a light shielding film (light shielding line 382) for shielding the dummy element from light irradiation is provided. Further, in the configuration according to claim 11, in the projection type display device according to claim 9 or 10, the current source has a plurality of the dummy elements connected in parallel. According to a twelfth aspect of the present invention, in the projection display device according to the tenth to eleventh aspects, the switching element is formed of a TFT. According to a thirteenth aspect of the present invention, in the projection display device according to the ninth to twelfth aspects, the dummy element is manufactured in the same step as the switching element. Further, claim 1
In the configuration according to the fourth aspect, in the projection type display device according to the ninth to thirteenth aspects, the current source is connected to the element substrate (1).
01) a first line (360) disposed thereon, a second line (364) disposed substantially parallel to the first line (360), and the first and second lines. And a third line (362) inserted between the third line (3)
62) a plurality of dummy elements (302) formed thereon;
A first lead wire (380) for connecting either the first or second line to the third line;
.., 368 connecting the lines of the plurality of dummy elements to the input terminals of the plurality of dummy elements.
, And third lead wires (374,..., 374) connecting the output terminals of the plurality of dummy elements.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Configuration of embodiment 1.1. Next, the configuration of an electro-optical device according to an embodiment of the present invention will be described.
This will be described with reference to FIG. FIG. 2 mainly shows electricity.
FIG. 1 mainly shows a portion mounted on an element substrate of an optical device.
Circuit block mounted separately from the element substrate
FIG. In FIG. 1, an electro-optical device includes
8-bit video data from the unit and its vertical synchronization signal
Vsync, horizontal synchronization signal Hsync, pixel clock C
LK and I ^TwoSupplied with C BUS (registered trademark) control signal
Is done. Reference numeral 202 denotes a secondary gamma correction circuit,
Corrects the gradation characteristics of the data and uses a 9-bit bus width to
The corrected corrected video data is output.

Reference numeral 204 denotes a multi-phase expansion circuit, which performs multi-phase expansion (here, 6-layer expansion) of the corrected video data. That is, the duration of the pixel value of each dot in the corrected video data is extended six times, and these timings are corrected so that the pixel values of 6 dots can be latched simultaneously. Next, a data inversion / non-inversion selection circuit 206 inverts some of these pixel values so that the polarity of the pixel values is inverted every dot. 208 is a digital / analog (D
/ A) A converter that converts the pixel values output from the data inversion / non-inversion selection circuit 206 into multi-phase video data VID1 to VID6, which are analog signals, and outputs the same. The polyphase video data VID1 to VID6 are supplied to the video amplifier 210-1.
６6.

[0010] 212 is ^{I 2} C ^{controller, I} 2 C
Each part in the electro-optical device is controlled based on the BUS control signal. An LCD timing generation circuit 214 generates various timing signals based on the horizontal synchronization signal Hsync and the vertical synchronization signal Vsync. The main ones among these timing signals will be described. FIG. 8 shows waveform examples of these timing signals.

First, CLX is a clock signal for display of the electro-optical device, has a clock cycle of the number of phases of the pixel clock CLK (here, six times), and has a duty ratio of 50.
% Signal. / CLX is its inverted signal (in this specification, the inverted signal is prefixed with "/"). DX is a line start pulse, which rises at the head of each line in the electro-optical device. NRG is a precharge signal, which rises slightly earlier than the timing at which precharge is to be performed, that is, the line start pulse DX. ENB1, EN
B2 is a latch enable signal, which rises to the H level alternately at the timing when the multi-phase video data VID1 to VID6 are stabilized. CLY is a line clock signal of the electro-optical device, has a predetermined line clock cycle, and has a duty ratio of 50%. DY is a frame start pulse, which rises at the beginning of each frame in the electro-optical device. BIASO and B
IASE is an odd dot polarity signal and an even dot polarity signal, and is a signal indicating the polarity of the voltage applied to the liquid crystal layer for the corresponding pixel (in other words, the polarity of the corresponding video data VID1 to VID6). That is, the polarity of the applied voltage indicates a positive polarity when these signals are at the L level and a negative polarity when these signals are at the H level.

Reference numeral 216 denotes a D / A converter, which is I ² C
A necessary analog signal is generated from the BUS control signal.
Sub Brightness is a brightness adjustment signal, and is a signal indicating a brightness adjustment command based on a user's panel operation or the like. Bias_C
OM is a reference potential signal of the brightness adjustment signal Sub Brightness. NRSH is a precharge potential maximum value signal, NRSL
Is a precharge potential minimum value signal, which indicates the maximum value and the minimum value of the precharge potential, respectively. LCCOM is a counter electrode potential and is applied to the counter electrode.

Reference numeral 222 denotes a differential amplifier, which is a luminance adjustment signal.
Video amplifier 210 that amplifies the difference between Sub Brightness and reference potential signal Bias_COM, and outputs the result as a gain signal to output video data VID1, 3, 5 of odd-numbered dots.
-1, 3 and 5. Similarly, the differential amplifier 224 is
Brightness adjustment signal Sub Brightness and reference potential signal Bias_C
The difference of OM is amplified, and the result is given as a gain to video amplifiers 210-2, 4, 6 that output video data VID2, 4, 6 of even-numbered dots.

Reference numerals 218 and 220 denote switching circuits, which are a luminance adjustment signal Sub Brightness and a reference potential signal Bi.
As_COM is supplied to the differential amplifiers 222 and 224 through straight connection or cross connection. Switching circuit 21
8, 220 connection state (straight or cross)
Complementary switching is performed according to the polarity signals BIASO and BIASE. Thereby, the video amplifiers 210-1 and 210-1,
Gain signals having different polarities and equal absolute values are supplied to the video amplifiers 3 and 5 and the video amplifiers 210-2, 4 and 6, respectively.

Next, reference numerals 230 and 232 denote differential amplifiers which amplify the difference between the precharge potential maximum value signal NRSH and the precharge potential minimum value signal NRSL, respectively, and odd-numbered dot precharge potential NRS1 and even-numbered dot precharge potential, respectively. Outputs NRS2. Reference numerals 226 and 228 denote switching circuits.
As in the case of 20, the connection state (straight or cross) is switched complementarily in accordance with the polarity signals BIASO and BIASE to change the precharge potential maximum value signal NRSH and the precharge potential minimum value signal NRSL to the differential amplifier 230,
232. Thereby, the precharge potential NR
S1 and NRS2 have different polarities and equal potentials.

Next, in FIG. 2, in the display area 101a on the element substrate, a plurality of scanning lines 112 are formed extending in the X (row) direction in the figure. Further, a plurality of data lines 114 are formed extending along the Y (column) direction. The pixel 110 is connected to the scanning line 11
2 is provided corresponding to each intersection of the data line 114 and
They are arranged in a matrix. Here, for convenience of explanation, in this embodiment, the total number of the scanning lines 112 is m and the total number of the data lines 114 is n (m and n are integers of 2 or more), and m rows × n columns Will be described as a matrix type display device.

1.2. Configuration of Pixel As a specific configuration of the pixel 110, for example, FIG.
Examples shown in (a) are given. In this configuration, the gate end of the transistor (MOS type FET) 116 is connected to the scanning line 112, the source end is connected to the data line 114, the drain end is connected to the pixel electrode 118, and the pixel electrode 118 and the counter electrode 108 are connected to each other. A liquid crystal 105, which is an electro-optical material, is sandwiched therebetween to form a liquid crystal layer. Here, the opposing electrode 108 is a transparent electrode formed on one surface of the opposing substrate so as to actually face the pixel electrode 118 as described later. Further, the pixel electrode 118 is connected to one end of the storage capacitor 119, and predetermined voltages VSSX and VSSY are applied to the other end of the storage capacitor 119 to prevent leakage of electric charges stored in the liquid crystal layer. In this embodiment, the storage capacitor 119 is connected to the pixel electrode 118 and the predetermined voltage VS.
SX and VSSY, but between the pixel electrode 118 and the counter electrode 108, and between the pixel electrode 118 and the ground potential GND.
It may be formed between pixels or between the pixel electrode 118 and the gate line.

Here, in the configuration shown in FIG.
Since only one channel type is used as the transistor 116, an offset voltage is required. However, as shown in FIG. 3B, a P-channel transistor and an N-channel transistor are complementarily combined. With such a configuration, the influence of the offset voltage can be canceled. However, in this complementary configuration, it is necessary to supply mutually exclusive levels as scanning signals, so that the scanning lines 112a, 112
Two scanning lines b are required.

1.3. Configuration of Secondary Gamma Correction Circuit 202 Next, a detailed configuration of the secondary gamma correction circuit 202 will be described with reference to FIG.
The principle of illuminance measurement using a type FET) will be described. The gate end and drain end (or source end may be connected) of the transistor are connected, and between 0.3 and 2 [V]
When a voltage of about VDD is applied, almost no current flows to the drain end. However, when the transistor is irradiated with light, a leak current corresponding to the illuminance flows to the drain end.

Although the magnitude of the current varies depending on the transistor generation process and the like, in the example of the transistor formed by the polysilicon process, 500 [lx] equals 20.
Leakage current of about 20 [pA] occurs at [fA], 500 [klx], and about 150 [pA] occurs at 1 [Mlx]. Therefore, it is possible to measure the illuminance by measuring the drain current.
However, since the leakage current per transistor is extremely low, it is preferable to measure several hundred to several thousand transistors in parallel to measure the leakage current.

In FIG. 5, 302,..., 302 are measurement transistors formed in the element substrate in the same process as the pixel drive transistors 116, and are connected in parallel in the order of hundreds to thousands. Therefore, when the element substrate is irradiated with light, a leak current Idl flows in a parallel circuit of these measurement transistors. 304 and 306 are resistors, and 308 is an operational amplifier, which forms an amplifier. That is, the amplifier outputs a voltage of “−Idl · R2” with respect to the leak current Idl.

An analog / digital (A / D) converter 310 outputs a measured value of the leak current Idl as a digital value based on the amplification result. Reference numeral 312 denotes a look-up table which stores gradation correction characteristics of video data in a state where the leak current Idl is assumed to be a predetermined reference value. That is, since the transmittance of the liquid crystal changes non-linearly according to the applied voltage as shown in FIG. 7A (in the case of normally white), as shown in FIG. The voltage command value to be applied to the liquid crystal layer corresponding to the gradation of the video data is set in the lookup table 3 so that the transmittance changes linearly in response to the gradation.
12 is stored. However, the characteristic of FIG. 3A changes as shown in FIG. 3C according to the increase of the leak current. That is, when the leak current increases, it becomes necessary to apply a higher voltage to obtain the same transmittance. In FIG. 5, reference numeral 314 denotes a leak correction circuit which corrects the voltage command value based on the measured value of the leak current Idl and supplies the result to the multiphase expansion circuit 204. This correction specifically changes the amplification factor of the voltage applied to the liquid crystal, and can be performed by digital calculation. FIG.
In the above, an example using digital calculation has been described, but correction can also be made by analog amplification using the voltage value from the operational amplifier 308. However, the advantage of digital calculation is that nonlinear calculation is possible, finer adjustment is possible in consideration of the nonlinear characteristics of liquid crystal, and calculation data can be easily changed even when the liquid crystal material is changed. Having.

1.4. The description of the configuration of the driver and the like is returned to FIG. Reference numerals 252 and 254 denote Y drivers, each of which includes m latch circuits (the number of scanning lines 112). In the Y drivers 252 and 254,
Frame start pulse D supplied at the beginning of a frame
Y is sequentially transferred to each latch circuit in synchronization with the rising and falling timings of the line clock signal CLY,
The latched result is applied to each of the scan lines 112 by the scan signal G1,
, Gm are sequentially and exclusively supplied. In addition,
The Y drivers 252 and 254 have exactly the same scanning signals G1 and G
2, G3,..., Gm are supplied from both ends of the scanning line 112 in order to minimize the influence of impedance, parasitic capacitance, and the like on the scanning line 112.

Reference numeral 250 denotes an X driver, which comprises k (the number of data lines 114/6) latch circuits (not shown). In the X driver 250, the line start pulse DX supplied at the beginning of each line is sequentially transferred to each latch circuit in synchronization with the rising and falling timings of the clock signal CLX, and the latched result is output as signals P1, P2, .., Pk. As shown in FIG. 8, the signals P1, P2, P3,..., Pk overlap each other by a half cycle of the clock signal CLX.

Reference numerals 258-1 to 258-k denote AND circuits. When the subscript i of the signal Pi (where i = 1, 2, 3,..., K) is an odd number, a signal between the signal Pi and the latch enable signal ENB1 is obtained. While the logical product is output as the latch signal Qi, when the subscript i is an even number, the signal Pi and the latch enable signal EN are output.
The logical product with B2 is output as a latch signal Qi. As a result, the latch signals Qi are sequentially and exclusively output.

Reference numeral 256 denotes a sample and hold circuit, which is constituted by transistors provided for each data line 114. .., Qk are applied to the gate terminals of the transistors forming each group. The latch signals Q1, Q2,. Thus, the video data VID1 to VID6 at that time are applied to the corresponding six data lines 114. Reference numeral 260 denotes a precharge circuit, which includes a plurality of transistors provided for each data line 114. When a precharge signal NRG is applied to the gate terminals of these transistors, an odd dot precharge potential NRS1 is applied to the data line 114 corresponding to the odd dot, and an even dot precharge potential is applied to the data line 114 corresponding to the even dot. N
RS2 is applied simultaneously.

1.5. Next, the structure of the above-described electro-optical device will be described with reference to FIG.
This will be described with reference to (a) and (b). Here, FIG. 1A is a plan view showing the configuration of the electro-optical device 100, and FIG.
FIG. 2 is a sectional view taken along the line AA ′ in FIG. In these figures, reference numeral 101 denotes an element substrate on which a pixel electrode 118 and the like are formed. Reference numeral 102 denotes a counter substrate on which a counter electrode 108 is formed. The element substrate 101 and the counter electrode 108 are mutually
The liquid crystal 105 serving as an electro-optical material is sandwiched in this gap by keeping a certain gap. Actually, the sealing material 104 has a cutout portion, and after the liquid crystal 105 is sealed through the cutout portion, it is sealed with a sealing material, but is omitted in these drawings. Here, the element substrate 101 and the counter substrate 102 are amorphous substrates such as glass and quartz. The pixel electrodes 118 and the like are formed by TFTs formed by depositing a semiconductor thin film on the element substrate 101. That is, the electro-optical device 100 is used as a transmission type.

On the element substrate 101, various circuits are formed inside the sealant 104 and outside the display area 101a. That is, the display area 1 on the drawing
Y drivers 252 and 254 are formed on the left and right of 01a, a precharge circuit 260 is formed above, and an X driver 250 is formed below. Further, an area 302a in the upper right, upper left, lower right, lower left directions of the display area 101a
, A large number of measurement transistors 302,.
302 is formed.

In the element substrate 101, the sealing material 1 is located outside the region where the X driver 250 is formed.
A plurality of connection terminals are formed in an area 107 separated from the area 04, from which a control signal and a power supply voltage from the outside are input. On the other hand, the counter electrode 108 of the counter substrate 102 is connected to a conductive material (not shown) provided in at least one of four corners of the substrate bonding portion and a connection terminal provided in the region 107. The potential LCCOM is applied to the counter electrode 108.

In addition, depending on the application of the electro-optical device 100, first, for example, in the case of a direct-view type, first, a color filter arranged in a stripe shape, a mosaic shape, a triangle shape, or the like is provided on the counter substrate 102. Second, a light-shielding film (black matrix) made of, for example, a metal material or a resin is provided. In the case of color light modulation, for example, when used as a light valve of a projector described later, no color filter is formed. In the case of a direct-view type, a backlight for irradiating the electro-optical device 100 with light from the element substrate 101 side is provided as necessary.

Further, the element substrate 101 and the opposing substrate 1
An alignment film (not shown) rubbed in a predetermined direction is provided on the electrode forming surface of No. 02 to define the alignment direction of the liquid crystal molecules when no voltage is applied.
On the side of the counter substrate 102, a polarizer (not shown) corresponding to the orientation direction is provided. However, if a polymer-dispersed liquid crystal in which fine particles are dispersed in a polymer is used as the liquid crystal 105, the above-described alignment film, polarizer, and the like become unnecessary.
Since the light use efficiency is increased, it is effective in terms of high luminance and low power consumption.

1.6. Next, the structure of the transistor 116 for a pixel on the element substrate 101 will be described with reference to FIG. In FIG. 6A, the data lines 114 are provided to extend in the vertical direction, and the scanning lines 112 are provided to extend in the horizontal direction while being insulated from the data lines 114. A transistor 116 is formed above the scanning line 112 at the intersection of the two, and at the same time, the gate end of the transistor 116 is
2 are connected. Further, a contact 352 is formed on the data line 114 near the intersection, and a lead 354 is formed upward from the contact 352 to the upper side of the transistor 116.
6 is connected to the source end.

A contact 356 is also formed in the pixel electrode 118, and a lead 358 which is bent from the contact 356 on the way to the data line 114 and extends upward from the transistor 116 is formed. The tip of the lead wire 358 is connected to the drain of the transistor 116. When the electro-optical device 100 is used as a light valve of a projector described later, light is emitted from the element substrate 101 side. Therefore, the data line 114
Also functions as a light-shielding film that attenuates light applied to the transistor 116 and reduces leakage current.

Next, the measuring transistors 302,.
The structure of 302 will be described with reference to FIG. In the figure, 360 is a source line, 362 is a gate line, 364
Is a drain line, which is formed to extend in parallel. Contacts 376 and 378 are formed at the ends of the gate line 362 and the drain line 364, respectively.
Both lines are connected via a lead 380. On the gate line 362, measuring transistors 302,..., 302 are formed at substantially equal intervals.

These measuring transistors 302,...
The source line 360 and the drain line 364 have contacts 366,.
, 366 and 372, ..., 372 are formed. And contacts 366,..., 366 and 3
72,..., 372 to the measuring transistor 302,.
, 302, lead wires 368,.
, 374 and 374 are formed.
, 368 are connected to the source ends of the measuring transistors 302,..., 302, and the ends of the leads 374,..., 374 are connected to the drain ends of these transistors.

The source line 360 has the voltage VD
D is applied, and the measuring transistor 30 shown in FIG.
,..., 302 are realized. Also,
, 382 are formed below the measuring transistors 302,..., 302 in a direction orthogonal to the gate lines 362 and the like. The light shielding lines 382,..., 382 are provided in place of the data lines 114 in FIG. It becomes possible to give a substantially linear proportional relationship with the leak current characteristic.

2. Next, the operation of the electro-optical device according to the above-described embodiment will be described. FIG. 8 is a timing chart for explaining the operation of the electro-optical device. First, when the frame start pulse DY is supplied to the Y drivers 252 and 254, the scanning signals G1, G2, G3,..., Gm are sequentially and exclusively output within one frame by the transfer according to the clock signal CLY. .

The scanning signals G1, G2, G3,..., Gm each have a pulse width corresponding to a half cycle of the clock signal CLY, and correspond to the first scanning line 112 counted from the top. After the start pulse DY is supplied and the clock signal CLY rises for the first time,
The output is delayed at least by a half cycle of the clock signal CLY. When the scanning signals G1, G2, G3,..., Gm rise, the precharge signal NRG and the line start pulse DX rise sequentially.

First, when the scanning signal G1 is supplied to the first scanning line 112 from the top, all the transistors 116 in the first stage pixels 110 in the display area 101a are turned on. Are in a high impedance state, so that the storage capacitor 119 and the pixel electrode 1
The potential of 18 does not change. Here, the precharge signal NR
When G rises, all the transistors in the precharge circuit 260 are turned on. As a result, the odd-numbered dot precharge potential NRS1 is simultaneously applied to the data lines 114 corresponding to the odd-numbered dots, and the even-numbered dot precharge potential NRS2 is simultaneously applied to the data lines 114 corresponding to the even-numbered dots. Therefore, the precharge potential NRS1 or NRS2 is written to all the pixels 110 in the first stage.

Next, when the line start pulse DX is supplied to the X driver 250, the line start pulse DX is shifted in the X driver 250 in synchronization with the clock signal CLX. Then, the clock signal CLX 1
Signals P1, P2, P3,...
Pk are sequentially output based on the shifted line start pulse DX. On the other hand, latch enable signal ENB output from LCD timing generation circuit 214
1, ENB2 alternately rises to the H level at the timing when the multi-phase video data VID1 to VID6 are stabilized.

In the AND circuits 258-1 to 258-k, when the subscript i of the signal Pi (where i = 1, 2, 3,..., K) is an odd number, the signal Pi and the latch enable signal EN
While outputting the logical product with B1 as a latch signal Qi,
If the subscript i is an even number, the logical product of the signal Pi and the latch enable signal ENB2 is output as the latch signal Qi. As a result, the latch signal Qi becomes the video data VID
During the period when 1 to 6 are stabilized, they are sequentially and exclusively output.

The operation during the period when the scanning signal G1 rises and the signal P1 rises will be described in more detail. Some time after the rise of the signal P1, the latch enable signal ENB1 rises, and in synchronization with this, the latch signal Q1 rises. As a result, FIG.
, The leftmost or sixth transistor from the left in the sample hold circuit 256 is turned on, and the video data VID1 to 6 are the first to sixth data lines 1 from the left.
14 is applied.

At this time, since an H-level voltage is applied to the first scanning line 112 from the top, the scanning line 112
Via the six transistors 116 corresponding to the intersections of the first and sixth data lines 114 from the left with respect to the storage capacitor 119 and the pixel electrode 118.
-6, that is, a voltage is applied, and the storage capacitor 119 and the pixel electrode 118 are charged. The first scanning line 11
2 and the transistor 116 corresponding to the intersection of the seventh and subsequent data lines 114 from the left are also turned on. However, since these data lines 114 are in a high impedance state, the potentials of the storage capacitor 119 and the pixel electrode 118 are changed. Does not change.

Thereafter, similarly, latch signals Q2, Q3,.
As Qk sequentially rises, six video data VID1 to 6 are exclusively supplied to the data line 114, and these video data VID1 to 6 are written to the six transistors 116 in the first stage from the top. go. And
When all writing to the first-stage pixel 110 is completed, the scanning signal G2 is supplied to the second scanning line 112 from the top (H level voltage is applied), and the second-stage pixel 1
For 10, the video data VID1 to VID6 of the second stage are sequentially written. Thereafter, the same operation is repeated until the scanning signal Gm corresponding to the m-th scanning line 112 is output, and video data is written over the entire display area 101a. Furthermore, when the frame start pulse DY is supplied again, video data is written over the entire display area 101a. Hereinafter, the same operation is repeated every time the frame start pulse DY is supplied.

It is ideal that the video data (pixel voltage) written in the pixel 110 is held until it is precharged in the next frame. However, actually, as shown in the lowermost part of FIG. In addition, the absolute value of the pixel voltage decreases due to the leak current. Here, the solid line is the pixel voltage characteristic when the leak current is small, and the dashed line is the pixel voltage characteristic when the leak current is large. In the present embodiment,
The leakage current that is substantially proportional to the leakage current generated in the pixel transistor 116 is measured by the measurement transistors 302,.
Since the signal level is detected through the signal 302 and the signal level is corrected by the leak correction circuit 314 so as to compensate for the shift in gradation, a high-quality image can be obtained even if the leak current increases or decreases. .

3. Specific examples of electronic device 3.1. <Projector> Next, some examples in which the above-described electro-optical device is used in specific electronic devices will be described. First, a projector 1430, which is a projection display device using the electro-optical device according to the above-described embodiment as a light valve, will be described. FIG. 12 is a schematic configuration diagram illustrating a main part of the projection display device. In the figure, 1431 is a light source, 1442 and 1444 are dichroic mirrors, 1443, 1448 and 1449.
Is a reflection mirror, 1445 is an entrance lens, 1446 is a relay lens, 1447 is an exit lens, 100R, 100
G and 100B are liquid crystal light modulators using the electro-optical device, 1451 is a cross dichroic prism, 143
Reference numeral 7 denotes a projection lens. The light source 1431 includes a lamp 1440 such as a metal halide and a reflector 1441 that reflects light from the lamp. The dichroic mirror 1442 that reflects blue light and green light transmits the red light of the light flux from the light source 1431 and reflects the blue light and the green light. The transmitted red light is reflected by the reflection mirror 1443 and is incident on the liquid crystal light modulation device for red light 100R.
On the other hand, among the color lights reflected by the dichroic mirror 42, green light is a dichroic mirror 1444 that reflects green light.
And is incident on the liquid crystal light modulator for green light 100G. On the other hand, the blue light also passes through the second dichroic mirror 1444. For blue light, in order to prevent light loss due to a long optical path, a light guiding means including a relay lens system including an entrance lens 1445, a relay lens 1446, and an exit lens 1447 is provided. Into the liquid crystal light modulation device 100B. The three color lights modulated by the respective light modulators enter the cross dichroic prism 1451. This prism is formed by bonding four right-angle prisms, and a dielectric multilayer film that reflects red light and a dielectric multilayer film that reflects blue light are formed in a cross shape on the inner surface. The three color lights are combined by these dielectric multilayer films to form light representing a color image. The combined light is transmitted through a projection lens 1 as a projection optical system.
The image is projected on the screen 1452 by the 437, and the image is enlarged and displayed.

Next, FIG. 9A is a plan view showing a configuration of a projector using a reflection type electro-optical device according to the embodiment as a light valve. As shown in this figure, inside the projector 1100, the polarized light illumination device 1 is provided.
110 is arranged along the system optical axis PL. In the polarized light illuminating device 1110, the light emitted from the lamp 1112 becomes a substantially parallel light beam due to reflection by the reflector 1114, and enters the first integrator lens 1120. As a result, the light emitted from the lamp 1112 is split into a plurality of intermediate light beams. The split intermediate light beam is converted into one type of polarized light beam (s-polarized light beam) having a substantially uniform polarization direction by a polarization conversion element 1130 having a second integrator lens on the light incident side. From the light source.

Now, the s-polarized light beam emitted from the polarized light illuminating device 1110 is reflected by the s-polarized light beam reflecting surface 1141 of the polarizing beam splitter 1140. Of this reflected light beam, the light beam of blue light (B) is reflected by the blue light reflecting layer of the dichroic mirror 1151, and is modulated by the reflection-type electro-optical device 100B. Further, among the light beams transmitted through the blue light reflecting layer of the dichroic mirror 1151, the light beam of red light (R) is
The light is reflected by the red light reflection layer 52 and is modulated by the reflection-type electro-optical device 100R. On the other hand, of the light flux transmitted through the blue light reflecting layer of the dichroic mirror 1151,
The luminous flux of the green light (G) passes through a dichroic mirror 1152
Of the reflection type electro-optical device 10
Modulated by 0G.

Thus, the electro-optical device 100R,
The red, green, and blue lights, each of which is color-modulated by 100G and 100B, respectively,
2, 1151, and are sequentially synthesized by the polarizing beam splitter 1140, and then projected on the screen 1170 by the projection optical system 1160. Note that the electro-optical devices 100R, 100B, and 100G are provided with dichroic mirrors 1151 and 1152 for R, G,
Since a light beam corresponding to each primary color of B enters, no color filter is required.

3.2. <Mobile Computer> Next, an example in which the electro-optical device is applied to a mobile personal computer will be described. Fig. 9 (b)
FIG. 1 is a front view showing the configuration of this personal computer. In the figure, a mobile computer 1200 is shown.
Is composed of a main body 1204 having a keyboard 1202 and a display unit 1206. The display unit 1206 is configured by adding a backlight behind the electro-optical device 100 described above.

3.3. <Cellular Phone> Further, an example in which the electro-optical device is applied to a cellular phone will be described. FIG. 9C is a perspective view showing the configuration of the mobile phone. In the figure, a mobile phone 1300 is shown.
Is a plurality of operation buttons 1302 and an earpiece 130
4. The electro-optical device 100 is provided together with the mouthpiece 1306. The electro-optical device 100 is also provided with a backlight at the rear as necessary.

3.4. <Others> In addition to the electronic devices described above, in addition to those described above, LCD televisions, viewfinders, video tape recorders of the direct-view monitor type, car navigation devices, pagers, electronic notebooks, calculators, word processors, workstations, video phones, Examples include a POS terminal, a device equipped with a touch panel, and the like. It goes without saying that the above-described electro-optical device can be applied to these various electronic devices.

4. Modifications The present invention is not limited to the embodiments described above,
For example, various modifications are possible as follows. (1) In the above embodiment, the measurement transistor 3
02,..., 302, a light-shielding line 382,.
382, and the measuring transistors 302,.
The leak current characteristic of the pixel transistor 2 was made substantially proportional to the characteristic of the pixel transistor 116 (see FIG. 6B). However, if the relationship between the leakage current of the measurement transistors 302,..., 302 and the leakage current of the transistor 116 is known, the light shielding lines 382,.
, 382 may be removed. According to such a configuration, light is directly applied to the measurement transistors 302,..., 302, so that a larger leakage current can be obtained.

(2) The measuring transistor 302,
.., 302 are not limited to the positions shown in FIG. For example, as shown in FIG.
, 302, may be formed in a region outside the precharge circuit 260 and the X driver 250, and the measurement transistors 302,...

(3) The driving circuit of the electro-optical device 100
The driving circuit is not limited to those shown in FIGS. 1 and 2 and various types of driving circuits can be used. One example is shown in FIG. In the figure, a secondary gamma correction circuit 202 is configured similarly to that of the above embodiment. Reference numeral 404 denotes a one-phase / two-phase expansion circuit that expands the video data output from the secondary gamma correction circuit 202 into two-phase video data. 406
Is a data inversion / non-inversion selection circuit, which inverts one of the two-phase video data and sets the other to a non-inversion state.

Reference numerals 408 and 410 denote D / A converters, which convert the two-phase video data output from 406 into analog signals. The converted video data is supplied to the sample and hold circuit 416 via the differential amplifiers 412 and 424. Sample hold circuit 41
6 latches these video data and outputs them as multi-phase video data VID1 to VID6. Also in this modification,
The leak correction circuit 314 corrects the signal level based on the leak current Idl output from the measurement transistors 302,. This signal level correction is performed in the secondary gamma correction 202. As a result, a high-quality image can be obtained even if the leakage current increases or decreases as in the above embodiment.

(4) In the above embodiment, the element substrate 101 constituting the electro-optical device is an amorphous substrate such as glass or quartz.
Although T was formed, the present invention is not limited to this. For example, when the element substrate 101 is formed of an opaque semiconductor substrate, the pixel electrode 118 is formed of a reflective metal such as aluminum, and the counter substrate 102 is formed of glass or the like, the electro-optical device 100 can be used as a reflection type. .

(5) Further, in the above embodiment, an example in which the present invention is applied to an electro-optical device using a liquid crystal has been described. However, other electro-optical devices, in particular, gradations according to a voltage applied to a pixel and the like are described. The present invention is applicable to all electro-optical devices that perform display. Such an electro-optical device includes an electroluminescence (EL) device and a plasma display (PD).
P) Apparatus and the like are conceivable. In particular, in the case of an organic EL, there is no need to perform AC driving like a liquid crystal, and there is no need to perform polarity inversion. In the case of an EL or PDP, strong light is not input from the outside because it is a self-luminous element. However, since the TFT is arranged at a position close to the self-luminous element, light leaks to the switching element (TFT) due to this light. I do. In this case, a light leak detecting element may be provided around the panel as in the previous embodiment, but in order to realize more accurate display, a light leak detecting element is formed for each pixel and controlled. High quality image display without image quality degradation due to light leakage is possible.

(6) In the above embodiment, an example is given in which the scanning lines 112 are selected in order from the top by sequentially and exclusively outputting the scanning signals G1, G2, G3,..., Gm. Is not limited to this. For example, the scanning signals may be expressed as “G1, G11, G21,..., G2, G12, G
22,..., G3, G13, G23,...
2 may be selected. Further, it is not always necessary that the two systems of Y drivers 252 and 254 output the same scanning signal.
The Y driver 254 may alternately output the scanning signals of the even lines.

[0060]

As described above, according to the present invention, the second leak current corresponding to the first leak current is output from the current source provided on the element substrate 101, and the second leak current is output. Since the correction circuit corrects the pixel voltage based on the current, for the first leak current of the switching element,
It is possible to automatically correct the gradation characteristics.

[Brief description of the drawings]

FIG. 1 is a block diagram (1/2) illustrating an electrical configuration of an electro-optical device according to an embodiment of the present invention.

FIG. 2 is a block diagram (2/2) illustrating an electrical configuration of the electro-optical device according to the embodiment of the invention.

FIG. 3 is a diagram showing a configuration example of a pixel in the embodiment.

FIG. 4 is a structural diagram of the electro-optical device according to the embodiment.

FIG. 5 is a block diagram illustrating a detailed configuration of a secondary gamma correction circuit 202.

FIG. 6 is a structural diagram of a pixel transistor 116, measurement transistors 302,..., 302, and peripheral portions thereof.

FIG. 7 is a diagram illustrating the operation of the secondary gamma correction circuit 202.

FIG. 8 is a timing chart of the electro-optical device according to the embodiment.

FIG. 9 is a diagram illustrating examples of various electronic apparatuses to which the electro-optical device is applied.

FIG. 10 is a block diagram of a main part in a modified example of the embodiment.

FIG. 11 is a structural diagram of an electro-optical device according to another modification of the embodiment.

FIG. 12 is a schematic configuration diagram of a projector to which the electro-optical device is applied.

[Explanation of symbols]

100 electro-optical device 100R, 100G, 100B liquid crystal light modulator 101 element substrate 101a display area 102 counter substrate 104 sealing material 105 liquid crystal 107 area 108 counter electrode 110 pixel 112 scanning line 114 data line 116 pixel transistor (switching element) 118 pixel electrode 119 storage capacitor 202 secondary gamma correction circuit 204 multi-phase expansion circuit 206 ...... data inversion and non-inversion selection circuit 208 ...... D / A converter 210-1～6 ...... video amplifier 212 ...... ^{I 2} C control circuit 214 ...... LCD timing generator circuit 216 ...... D / A converter 218, 220 ... Switching circuits 222, 224 ... Differential amplifiers 226, 228 ... Switching circuits 230 , 232 Differential amplifier 250 X driver 252, 254 Y driver 256 Sample hold circuit 258-1 to 258-k AND circuit 260 Precharge circuit 302,,, 302 For measurement Transistor (current source) 302a Area 304, 306 Resistor 308 Operational amplifier 310 A / D converter 312 Look-up table 314 Leak correction circuit 352 Contact 354 Lead wire 356 ... Contact 358 Lead wire 360 Source line (first line) 362 Gate line (third line) 364 Drain line (second line) 366, 366, contact 368 , 368,… Lead wire 372,…, 372… Contact 374,… 374 Lead wires 376, 378 Contacts 380 Lead wires 382, 382, Light-shielding lines 406 Data inversion / non-inversion selection circuits 408, 410 D / A converters 412, 424 Differential amplifier 416 Sample hold circuit 1430 Projector 1431 Light source 1437 Projection lens

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G09G 3/20 621 G09G 3/20 621M 5C080 641 641C 642 642C 642P 680 680C H04N 5/66 H04N 5/66 B F-term (reference) 2H088 EA12 HA08 HA13 HA24 HA28 MA13 2H092 JA24 NA25 PA07 PA13 RA05 2H093 NA16 NA31 NA41 NA51 NC23 NC24 NC34 NC51 NC58 ND06 NE06 5C006 AA01 AA16 AC26 AF13 AF46 AF71 AF81 AF83 BB16 BB29 BF31 BF20 BC20 EB05 EC11 FA18 FA21 FA36 FA54 5C058 AA06 AA09 AB06 BA07 BA23 BB25 EA26 5C080 AA10 BB05 DD04 EE19 EE29 FF11 GG07 GG08 JJ02 JJ03 JJ04 JJ05 JJ06

Claims (14)

[Claims] A plurality of pixel electrodes disposed on an element substrate to which a pixel voltage is applied; and a conductive state during a selection period, whereby the pixel voltage is applied to the pixel electrode, and a non-selection period is applied to the pixel electrode. A switching element that holds the pixel voltage in the pixel electrode by being in a conductive state; a current source including a dummy element of the switching element; and a correction circuit that corrects the pixel voltage according to a current flowing through the current source. An electro-optical device comprising: 2. A plurality of pixel electrodes which are arranged on an element substrate and to which a pixel voltage is applied are turned on during a selection period, so that the pixel voltage is applied to the pixel electrode and a non-selection period is applied to the pixel electrode. A switching element that holds the pixel voltage in the pixel electrode by being in a conductive state; a light-shielding film that shields the switching element from light irradiation; a current source including a dummy element of the switching element; A correction circuit for correcting the pixel voltage according to a flowing current. 3. The electro-optical device according to claim 2, further comprising a light-shielding film that shields the dummy element from light irradiation. 4. The device according to claim 1, wherein the current source includes a plurality of the dummy elements connected in parallel.
An electro-optical device according to claim 1. 5. The electro-optical device according to claim 1, wherein the switching element comprises a TFT. 6. The electro-optical device according to claim 1, wherein the dummy element is manufactured in the same process as the switching element. 7. The current source includes: a first line disposed on the element substrate; a second line disposed substantially in parallel with the first line; Connecting a third line interposed between the third line, a plurality of dummy elements formed on the third line, and the third line with one of the first or second line A first lead wire, a second lead wire connecting the first line to an input end of the plurality of dummy elements, and a second lead wire connecting the second line and an output end of the plurality of dummy elements. The electro-optical device according to claim 1, further comprising a third lead wire. 8. An electronic apparatus comprising the electro-optical device according to claim 1. 9. A projection display device comprising: a light source; a light modulation device that modulates light from the light source; and a projection lens that projects light modulated by the light modulation device, wherein the light modulation device comprises: A plurality of pixel electrodes disposed on a substrate and to which a pixel voltage is applied; and being in a conductive state during a selection period, the pixel voltage is applied to the pixel electrode, and being in a non-conductive state during a non-selection period. A switching element that holds the pixel voltage on the pixel electrode, a light-shielding film that shields the switching element from light irradiation, a current source including a dummy element of the switching element, and a current flowing through the current source. And a correction circuit for correcting a pixel voltage. 10. The projection type display device according to claim 9, further comprising a light shielding film for shielding said dummy element from light irradiation. 11. The projection display device according to claim 9, wherein said current source has a plurality of said dummy elements connected in parallel. 12. The projection type display device according to claim 10, wherein said switching element comprises a TFT. 13. The projection display device according to claim 9, wherein the dummy element is manufactured in the same process as the switching element. 14. The current source, comprising: a first line disposed on the element substrate; a second line disposed substantially parallel to the first line; Connecting a third line interposed between the third line, a plurality of dummy elements formed on the third line, and the third line with one of the first or second line A first lead wire, a second lead wire connecting the first line to an input end of the plurality of dummy elements, and a second lead wire connecting the second line and an output end of the plurality of dummy elements. 14. The projection type display device according to claim 9, further comprising a third lead wire.