JP3952067B2 - Display device, electro-optical device driving method, and electronic apparatus - Google Patents

Description

  The present invention relates to a display device having an electro-optical device such as a liquid crystal device whose transmittance (reflectance) changes according to an applied voltage.

  As an electronic device using this type of display device, for example, three liquid crystal devices (LCD) that light-modulate each color light of R (red), G (green), and B (blue) are light valves (L / V). The projection type display apparatus used as can be mentioned. FIG. 16 shows an applied voltage (V) -transmittance (T) characteristic specific to each liquid crystal device for modulating R, G, B color light (when twisted nematic liquid crystal is used). In FIG. 16, the voltage application range to the liquid crystal can be from 0 V to 6 V, but the white level region where the transmittance is almost 100% and the black level region where the transmittance is almost 0% are both saturated. Therefore, the amplitude of the voltage applied to the liquid crystal is limited to about 3.8 V so that the white level and the black level are not saturated. That is, the direct current bias (DC bias) of the video signal is adjusted so that a voltage that does not saturate the white level and the black level is applied to each liquid crystal, and this is called brightness adjustment. Further, the VT characteristics of the R, G, and B colors shown in FIG. 17 have different slopes, and there are variations in voltages that saturate at the white level and the black level. In order to reduce the variation, the gain of the video signal is adjusted, which is referred to as gain adjustment. Note that in a liquid crystal device (LCD), the transmittance is defined by the ratio of the amount of light transmitted through a liquid crystal panel that sandwiches liquid crystal between a pair of substrates and a polarizing plate disposed on at least one surface thereof. Note that the transmittance is applied in place of the reflectance in the reflection type electro-optical device.

  FIG. 17 shows the relationship between the gradation value and the transmittance of the digital input signal after the brightness adjustment and gain adjustment. In FIG. 17, there is little change in the transmittance with respect to the change in the gradation value especially in the black level region, and a sufficient resolution cannot be obtained.

  In order to obtain the ideal gamma characteristic (ideal γ characteristic) shown in FIG. 17, the digital video signal is corrected using the gamma correction characteristic shown in FIG. When the liquid crystal device is driven based on a signal that has been gamma-corrected according to the characteristics shown in FIG. 18, characteristics close to the ideal gamma characteristics in FIG. 17 can be obtained as shown in FIG.

  As described above, conventionally, brightness adjustment and gain adjustment have been indispensable in order to obtain gamma correction characteristics.

  Therefore, a display device using a conventional liquid crystal device needs a circuit configuration as shown in FIG. In FIG. 15, an image signal is converted into a digital image signal by an analog-digital (A / D) converter 10 and signal processing including gamma correction and digital-analog (D / A) conversion is performed by an image signal processing circuit 20. Is made. The video signal processing circuit 20 includes an ASIC 22 including a gamma correction circuit and a D / A converter 24. The analog video signal is gain-adjusted by the amplifier 30, further subjected to DC bias adjustment (brightness adjustment) by the bias adjustment circuit 40, and supplied to the liquid crystal device 50.

The CPU 60 shown in FIG. 15 manages the control of this display device. The CPU 60 controls the gamma correction as follows. First, the VT characteristic specific to the liquid crystal device 50 shown in FIG. 16 is actually measured. Next, the CPU 60 controls the gain adjustment of the amplifier 30 via the gain control unit 80, and also controls the DC bias in the bias adjustment circuit 40 via the brightness control unit 90, and the VT characteristics shown in FIG. obtain. The VT characteristics, gain adjustment data at that time, and brightness adjustment data are stored in the EEPROM 70. The CPU 60 obtains a gamma correction characteristic shown in FIG. 18 by calculation based on the VT characteristic shown in FIG. 17 stored in the EEPROM 70 and a preset ideal gamma characteristic. This gamma correction characteristic is set by the CPU 60 in the gamma correction circuit in the ASIC 22 as table information, for example. Therefore, the video signal input from the A / D converter 10 is corrected according to the table information, and the amplifier 30 and the bias adjustment circuit 40 perform gain correction and brightness correction according to the gain adjustment data and brightness adjustment data stored in the EEPROM 70. Thus, the VT characteristics as shown in FIG.
JP-A-7-72832 JP-A-2-271389

  According to the above-described conventional apparatus, the above-described gain adjustment and brightness adjustment are indispensable before determining the gamma correction characteristics shown in FIG. 18 in the gamma correction circuit in the ASIC 20. Since the gain adjustment and the brightness adjustment are different for each liquid crystal device, it is an extremely troublesome work, and if there is an adjustment failure, it immediately affects the image quality, so that it is necessary to make a strict adjustment. In particular, in a projection display device that synthesizes and projects color light modulated by a plurality of liquid crystal devices, mutual adjustment is required between the liquid crystal devices, and gamma correction requires a very complicated operation.

  Further, in the conventional display device, since the brightness adjustment is performed, the range of transmittance in the liquid crystal device is narrowed, which causes a decrease in contrast and a dark screen. That is, as a result of the conventional brightness adjustment and gain adjustment, the liquid crystal device has a transmittance of, for example, 3% as a black level and a transmittance of, for example, 97% as a white level. As described above, the contrast was lowered and the screen was darker than that using the range.

  Accordingly, an object of the present invention is to provide a display device and an electronic apparatus that can bring the brightness and contrast of the electro-optical device closer to the maximum characteristics of the electro-optical device.

  Another object of the present invention is to provide a display device and an electronic apparatus that do not require gain adjustment and brightness adjustment.

  Still another object of the present invention is to provide a display device and an electronic apparatus that can reproduce ideal input-output characteristics with respect to gamma correction and color temperature.

A display device according to the present invention includes an electro-optical device whose light transmittance changes based on a voltage applied to an electro-optical material,
A digital gamma correction circuit for gamma correcting a digital video signal;
A digital-analog conversion circuit for converting the digital video signal corrected by the digital gamma correction circuit into an analog video signal;
An amplifier for amplifying the analog video signal,
Applying a voltage to the electro-optic material based on the output of the amplifier;
The digital gamma correction circuit converts the n-bit digital video signal into an N (N ≧ n + 2) bit digital signal based on a gamma correction characteristic predetermined according to an applied voltage-transmittance characteristic unique to the electro-optical device. It converts into a video signal, It is characterized by the above-mentioned.

The gamma correction method according to the present invention is a gamma correction method for correcting an applied voltage-transmittance characteristic specific to an electro-optical device in which light transmittance changes based on a voltage applied to an electro-optical material.
Gamma correction of digital video signal,
The gamma-corrected digital video signal is converted into an analog video signal,
Amplifying the analog video signal;
Applying a voltage to the electro-optic material based on the amplified analog video signal,
When the gamma correction is performed, the digital image signal of n bits is converted into N (N ≧ n + 2) bits based on a gamma correction characteristic predetermined according to an applied voltage-transmittance characteristic unique to the electro-optical device. It is characterized in that it is converted into a digital video signal.

  Here, in the inherent applied voltage-transmittance characteristics of the electro-optical device, in the normally black mode, a saturation state where the change in transmittance is small with respect to the change in applied voltage on the black level side where the transmittance is 0%. (See FIG. 3). Therefore, the gamma correction characteristic for compensating for this is a steep characteristic on the black level side, and a large amount of gradation data is consumed for correcting the area (see FIG. 4). In the normally white mode, on the contrary, the white level side with a transmittance of 100% is saturated, so that a large amount of gradation data is consumed for correcting the area. That is, in any display mode, the change in the VT characteristic is small when the transmittance is near 0% or 100%, so that the display gradation is changed at a uniform level by performing gamma correction on this region. In addition, the transmittance is changed more linearly by reducing the voltage change of the video signal in this region. In order to finely change the voltage change of the video signal, more gradation data of the digital video signal must be used for this region.

  As a result, the amount of gradation data allocated to an area including a halftone having a luminance of 10% to 90% is reduced. In fact, when the number of input bits to the digital gamma correction circuit is n bits (e.g., 8 bits), even if the number of output bits is n or n + 1 bits, the data is originally about 200 tones with a luminance of 10% to 90%. It has been found that a sufficient amount of gradation data cannot be assigned to an area including a halftone having a value (see the case of 9-bit output in FIG. 4). The present invention solves the above problem by setting the number of output bits of the digital gamma correction circuit to n + 2 bits or more (see the case of 10-bit output in FIG. 4).

  As described above, according to the present invention, the number of bits of the digital video signal assigned to the halftone area can be ensured even when an area having a small change rate in the applied voltage-transmittance characteristic specific to the electro-optical device is used. Therefore, when the present invention is used, the range of use of the applied voltage-transmittance characteristic specific to the electro-optical device is expanded. For this reason, a bright and high-contrast image can be provided.

  In the present invention, for the reasons described above, the gamma correction characteristic can be determined in accordance with the applied voltage-transmittance characteristic unique to the electro-optical device in the entire range of transmittance of 0% to 100%. As a result, the conventional brightness adjustment and gain adjustment described above are completely unnecessary.

  In order to eliminate the need for conventional brightness adjustment and gain adjustment, the digital gamma correction circuit performs at least one (preferably both) bias adjustment and gain adjustment of the video signal to convert the digital video signal. As a result, the amplifier does not have to have a variable resistor serving as a bias adjusting unit and a gain adjusting unit.

  In the present invention, a video signal is output from the amplifier so as to invert the polarity of a voltage applied to the electro-optic material at a predetermined period, and the digital video signal output from the digital gamma correction circuit is output from the amplifier. A digital polarity reversing circuit for digitally reversing the polarity every predetermined period, or the analog video signal output from the digital-analog converter is converted to an analog polarity every predetermined period An analog polarity inverting circuit for inverting is provided.

  In the present invention, a voltage having the first polarity and the second polarity can be applied to the electro-optic material at a predetermined cycle. For this purpose, it is possible to provide a digital polarity inversion circuit that digitally inverts the digital video signal from the digital gamma correction circuit every predetermined period. Alternatively, it is possible to provide an analog polarity inversion circuit for analogly inverting the analog video signal from the digital-analog converter every predetermined period.

  When performing such polarity reversal, the voltage output from the amplifier when the electro-optical device achieves one of the maximum and minimum transmittances is set to the first and second polarities. It is preferable that both voltages be substantially equal when the voltage is applied, and this equal voltage is the center potential of the voltage amplitude from the amplifier. Here, as described above, when the use range of the applied voltage-transmittance characteristic specific to the electro-optical device is expanded, the output amplitude from the amplifier also increases. However, the voltage amplitude can be minimized by sharing the center potential of the output amplitude from the amplifier as, for example, the white level potential during the first and second polarity driving.

The electronic apparatus according to the present invention includes a plurality of electro-optical devices whose light transmittance changes based on a voltage applied to the electro-optical material, and combines and displays the light modulated by the plurality of electro-optical devices. Equipment,
Each of the electro-optical devices is
A digital gamma correction circuit for gamma correcting a digital video signal;
A digital-analog conversion circuit for converting the digital video signal corrected by the digital gamma correction circuit into an analog video signal;
An amplifier for amplifying the analog video signal,
A voltage is applied to the electro-optic material based on the output of the amplifier,
Each digital gamma correction circuit converts the n-bit digital video signal into N (N ≧ n + 2) bits based on a gamma correction characteristic predetermined according to an applied voltage-transmittance characteristic specific to each electro-optical device. Respectively converted into digital video signals.

  If the present invention is used, the range of use of the applied voltage-transmittance characteristic specific to each electro-optical device is expanded. For this reason, if each of the images formed by a plurality of electro-optical devices becomes a bright and high-contrast image, the R (red), G (green), and B (blue) color lights are modulated by the plurality of electro-optical devices. In a projection display apparatus that combines the modulated color light and forms an image on the screen to display an image, the display image is brighter and the contrast is higher.

  In addition, if the color lights modulated by the electro-optical devices are combined, if the input grayscale data is the same, the transmittance of the VT characteristics of the electro-optical device is proportional to the ratio (level). If the transmittance with respect to the tone data is the same or the transmittance ratio is not the same even if the gradation changes, the color balance of the composite image will be lost as the gradation changes. In the present invention, the digital gamma correction circuit has a characteristic curve of the gradation data and the corresponding transmittance of the electro-optical device that is substantially the same among the plurality of electro-optical devices, or has a similar shape to each other. Thus, since the digital video signal is converted, the color balance can be stabilized regardless of the gradation level.

  The digital gamma correction circuit converts at least one of a bias adjustment and a gain adjustment of a video signal applied to the electro-optic material into a digital video signal. Thereby, the amplifier can have no variable resistance as a bias adjusting means and a gain adjusting means.

  Further, the plurality of electro-optical devices modulate different color lights, and the digital gamma correction circuit corresponding to the plurality of electro-optical devices has a color temperature indicated by the combined light of the color lights modulated by the electro-optical devices. Make corrections. More specifically, the digital gamma correction circuit corresponding to the plurality of electro-optical devices adjusts the slope of the transmittance characteristic curve of the electro-optical device corresponding to gradation data between the plurality of electro-optical devices. By doing so, the color temperature is corrected. That is, the color temperature of the synthesized color can be made different by mutually adjusting the slope of the VT characteristic curve of each electro-optical device between the color lights. It is possible to perform correction in consideration of color temperature correction of colors.

  In the present invention, the video signal is treated as equivalent to the image signal. The transmittance means the light reflectance in the reflection type electro-optical device.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
(Configuration of the entire device)
FIG. 1 shows a schematic block diagram of a liquid crystal display device as an example of a display device using an electro-optical device. FIG. 2 is a block diagram showing a part of FIG. 1 in detail.

  1, the liquid crystal display device includes an analog-digital (hereinafter abbreviated as A / D) converter 100 that converts an input analog video signal into an 8-bit digital video signal, a signal processing circuit 200, It has an amplification block 300 and a liquid crystal device 400 which is an example of an electro-optical device. The signal processing circuit 200 includes an ASIC 210 and a digital-analog (hereinafter abbreviated as D / A) conversion block 260. The CPU 500 of this liquid crystal display device is responsible for overall control of the liquid crystal display device. In the present embodiment, the CPU 500 will be described later in the ASIC 210 based on data stored in a storage unit such as a nonvolatile EEPROM 600. This is used to determine the gamma correction characteristic of the digital gamma correction circuit 220.

  As shown in FIG. 2, the ASIC 210 includes a digital gamma correction circuit 220 that performs gamma correction on the digital video signal output from the D / A converter 100, and six digital video signals that have been subjected to gamma correction. A phase expansion circuit (serial-parallel conversion circuit) 230 that performs parallel conversion into parallel digital video signals D1 to D6 and a digital polarity inversion circuit 240 that performs digital polarity inversion processing on the digital video signals transmitted in parallel are provided. ing. The D / A conversion block 260 is provided with first to sixth D / A converters 261 to 266 for converting the digital video signals D1 to D6 into analog video signals, respectively. Further, the amplification block 300 is provided with first to sixth operational amplifiers 301 to 306 for each parallel video signal.

  The first to sixth operational amplifiers 301 to 306 receive the polarity inversion bias signal 307 at their negative terminals, and the force lines of the first to sixth D / A converters 261 to 266 are at the positive terminals. It is connected.

  Gain setting resistors R1 and R2 are connected to the first to sixth operational amplifiers 301 to 306, respectively. Here, assuming that the input to the plus terminal of the operational amplifier is Vin and the input to the minus terminal is Vbias, the output Vout of the operational amplifier is given by the following equation (1).

Vout = (1 + R2 / R1) · Vin + (R2 / R1) · Vbias
... (1)
The first to sixth operational amplifiers 301 to 306 periodically invert the polarity of the voltage of the analog video signal based on the polarity inversion bias signal 307.

  The liquid crystal device 400 includes a liquid crystal pixel portion 410, and a scanning circuit 420 and a data driving circuit 430 for driving the display. The liquid crystal pixel portion 410 is formed by enclosing a twisted nematic liquid crystal, which is an electro-optic material, between a pair of substrates. One substrate is, for example, an active matrix substrate, and a plurality of scanning lines and a plurality of data lines are formed, and switching elements such as transistors controlled by the scanning lines in the vicinity of the respective intersections, and the conductive switching elements And a pixel electrode to which a video signal is applied from the data line. Then, by applying a voltage between the pixel electrode and a common electrode (formed on the active matrix substrate or the other substrate facing the common electrode) opposed to each other with the liquid crystal in between, the arrangement of liquid crystal molecules according to the voltage The direction changes, and the polarization axis of light is rotationally controlled according to the voltage applied to the pixel electrode of each pixel. This is called light modulation. In the liquid crystal device, polarizing means such as a polarizing plate that transmits only light of a predetermined polarization axis is disposed on one side or both sides of a pair of substrates, and light whose polarization axis is rotated and transmitted through the liquid crystal is The polarized light is transmitted. The ratio of the amount of light transmitted through the polarizing means is the light transmittance, and an image can be displayed by changing the light transmittance according to the gradation level represented by the video signal.

  The video signal voltages V1 to V6 output from the amplifiers 301 to 306 are supplied in parallel to the data driving circuit 430, and the voltages V1 to V6 are simultaneously supplied to the six data lines. On the other hand, the scanning lines are sequentially selected by the scanning circuit 420, and a video signal voltage is applied from the data line to the pixel electrode via a switching element connected to the selected scanning line.

  Note that in the liquid crystal device 400, the scanning circuit 420 and the data driving circuit 430 may be formed in the peripheral portion of the active matrix substrate constituting the liquid crystal pixel portion 410.

  As described above, in the present embodiment, one liquid crystal device 400 has been described as an example, but a plurality of such liquid crystal devices may be provided.

In a projection display device that projects light in which R (red), G (green), and B (blue) color lights are individually modulated and combines three color lights, the liquid crystal device is used as a light valve for light modulation. Use three. In such a projection display device, the display device shown in FIG. 1 and the block shown in FIG. 2 are provided for each color of R (red), G (green), and B (blue), and the video signal of each color light. Are each A / D converted by the A / D converter 100, gamma corrected by the ASIC 210, D / A converted by the D / A converter 260, and an analog video signal is generated by the amplification block 300, In response to this, each liquid crystal device 400 is driven to modulate each color light. The modulated RGB color lights are then combined and projected to form a color image on the projection surface.
(Description of operation of digital gamma correction circuit)
Next, the gamma correction performed by the digital gamma correction circuit 220 shown in FIG. 1 will be described.

  The digital gamma correction circuit 220 applies an n-bit, for example, 8-bit digital signal (256 gradations) output from the A / D converter 100 to an applied voltage unique to the liquid crystal device 410 within a transmittance range of 0% to 100%. -Gamma correction based on predetermined storage information in accordance with transmittance characteristics (hereinafter also referred to as VT characteristics), and conversion into a digital signal of N (N≥n + 2) bits, for example, 10 bits.

  Here, the characteristic VT characteristic of the liquid crystal device 400 is shown in FIG. FIG. 3 shows VT characteristics of a liquid crystal device using twisted nematic liquid crystal as a liquid crystal and setting a pair of polarizing plates sandwiching a liquid crystal panel in a normally black mode. The horizontal axis in FIG. 3 represents the voltage (V) applied to the liquid crystal during positive polarity driving (the voltage applied between the pixel electrode and the common electrode, not the voltage of the video signal itself), and the vertical axis represents the liquid crystal device 400. The transmittance (%) of light that passes through is shown. FIG. 3 shows VT characteristic curves of three liquid crystal devices 400 that respectively modulate R (red), G (green), and B (blue) color lights in the projection display device described above. FIG. 4 shows the relationship between the input video signal and the output after the gamma correction in the digital gamma correction circuit 220 shown in FIG. 2 provided for each liquid crystal device 400 for R, G, and B. . The horizontal axis of FIG. 4 indicates 255 gradation level input data (DATA IN) represented by an 8-bit video signal, and the vertical axis indicates the output after receiving this input and the gamma correction from the digital gamma correction circuit 220. Are output data (DATA OUT) of a video signal when output is performed with a 9-bit video signal (left axis) and when output is performed with a 10-bit video signal (right axis). FIG. 5 shows characteristics indicating the relationship between input data (DATA IN) after gamma correction according to the characteristics shown in FIG. 3 and the transmittances of the three liquid crystal devices.

  In FIG. 3, the VT characteristic (broken line) of the R light modulation liquid crystal device, the VT characteristic (solid line) of the G light modulation liquid crystal device, and the VT characteristic (one point) of the B light modulation liquid crystal device. 4 and 5 also show the characteristics of the digital gamma correction circuit 220 for each of the liquid crystal devices for R, G, and B, as in FIG. The G line is a solid line, and the B line is an alternate long and short dash line.

  In FIG. 3, the VT characteristic of each color light modulation liquid crystal device has a transmittance variation for each color according to the wavelength-transmittance property, or has a manufacturing variation in the manufacturing process of the liquid crystal device. Each rate characteristic is different. The point common to the VT characteristics of the liquid crystal devices for R, G, and B is that in the black level region where the transmittance is low, there is little change in the transmittance with respect to the change in the applied voltage V, and the resolution in this region is low. It is falling.

On the other hand, the ideal curve (dotted line) in FIG. 3 is an ideal VT characteristic after gamma correction. In order to obtain this ideal VT characteristic, the input (V) in the digital gamma correction circuit 220 is The relationship with the output (Ix) is as shown in the following equation (2).

  Here, the value of γ is γ = 2.2 in the case of the NTSC signal, and γ = 2.2 to 2.8 in the case of the output of the personal computer. In order to obtain a characteristic close to the ideal VT characteristic, the digital gamma correction circuit 230 in FIG. 2 applies the input data (DATA IN) to each liquid crystal device according to the gamma correction characteristic shown in FIG. Gamma correction for compensating the VT characteristic is performed to convert the output data (DATA OUT).

  If the digital video signal input to the digital gamma correction circuit 220 shown in FIG. 2 is gamma-corrected according to the gamma correction characteristics shown in FIG. 4 and the liquid crystal device 400 is driven based on the output, as shown in FIG. In addition, a gamma characteristic close to the ideal gamma curve in FIG. 3 can be obtained in each of the R, G, and B liquid crystal devices.

  Here, FIG. 4 shows both a 9-bit output with 512 output gradations (DATA OUT) and a 10-bit output with 1024 gradations. As described above, the digital gamma correction circuit 220 according to the present embodiment employs a 10-bit output that is 2 bits more than an 8-bit video signal input, and the 9-bit output is illustrated as a comparative example.

  The gamma correction characteristic of FIG. 4 compensates for the VT characteristic in the entire range (transmittance 0% to 100%) of the voltage amplitude shown in FIG. Therefore, for both 9-bit output and 10-bit output, in order to compensate for the characteristics of the black level region with luminance of 0% to 10%, the number of gradations for the black level region is approximately 44% of the total number of gradations. Will be assigned.

  Here, in an area including a halftone display area having a luminance of 10% to 90%, only about 160 gradations are assigned in the case of 9-bit output. Considering about 160 gradations in terms of the number of colors, the combination of the number of gradations of the three color lights is equivalent to about 4 million color display, and this cannot express all 16.7 million colors of actual video data. Become.

  On the other hand, in the case of 10-bit output, about 320 gradations, which is twice that in the case of 9-bit output, can be assigned to an area including a halftone display area with luminance of 10% to 90%. Considering about 320 gradations in terms of the number of colors, it is equivalent to about 32.768 million color display, and all colors of actual video data can be sufficiently expressed. Therefore, according to the present embodiment, the color reproducibility in the display image can be sufficiently ensured.

  Further, in the present embodiment, since the VT characteristic in the entire range of the voltage amplitude shown in FIG. 3 is 5 V is compensated, the characteristic shown in FIG. 16 is conventionally adjusted as shown in FIG. Brightness (bias) adjustment and gain adjustment are unnecessary. For this reason, in this embodiment, as is clear from the comparison between FIG. 2 and FIG. 15, a configuration (variable resistor connected to the amplifier) for brightness adjustment and gain adjustment becomes unnecessary. In addition, strict brightness adjustment and gain adjustment in a factory that previously required time of 25H / 1000 units are not required. Further, the storage unit 600 of FIG. 1 does not need to store brightness adjustment data and gain adjustment data as in the prior art, and it is only necessary to store the gamma correction characteristics of FIG. 4 as a conversion table.

  In particular, the projection display device has the configuration shown in FIGS. 1 and 2 for each of the three color lights. Conventionally, the brightness adjustment and gain adjustment are performed manually between the liquid crystal devices, so that work is very difficult. It was annoying. In addition, since adjustment means such as an adjustment variable resistor and a bias adjustment circuit are provided for each color light, the number of parts is increased. However, according to the present invention, such a variable resistor for adjustment and adjusting means are unnecessary, and the cost is reduced.

  Further, conventionally, it has been necessary to store the brightness adjustment data and the gain adjustment data in the storage unit. However, the storage of these data can be made unnecessary, and the storage area of the storage unit is effectively used. be able to. The storage unit may store a conversion table of gamma correction characteristics as shown in FIG. In the conversion table, a video signal is input as address data, data (DATA OUT) corresponding to the video signal input (DARTA IN) is stored in the storage area of the address, and this is read out according to the address input and gamma This is a configuration for converting into a corrected digital video signal.

  Furthermore, since the entire operation region of the transmittance 0% to 100% in the liquid crystal device 400 is used, the liquid crystal screen becomes brighter and the contrast is improved. In particular, in a projection display device, if each liquid crystal device can be used in a transmittance range of 0% to 100%, a projected image obtained by combining the color lights becomes brighter and the number of display colors increases.

In this embodiment, the D / A converter is increased in cost due to the 10-bit output. However, by including this, the ASIC 210 is made into a dedicated IC as one package, thereby preventing an increase in cost.
(Gamma correction characteristics including color temperature correction)
Next, color temperature management in a projection display device that uses the liquid crystal device 400 of the previous embodiment for RGB color light modulation will be considered.

The color temperature of the R, G, B mixed color obtained by combining the three color lights of R, G, B is determined by the x, y coordinates on the chromaticity diagram of the mixed light. Further, the x, y coordinates are (xR, yR), (xG, yG) (xB, yB) for the R, G, B, respectively, and the luminance (transmittance) of each color is YR, Assuming YG and YB, the following formula (3) is established.

  In this case, if the ratio of YR, YG, YB existing in the denominator is constant, the values of x, y are constant.

  Therefore, at the time of calculating the gamma correction characteristics as described above, the x, y coordinate data of the R, G, B monochromatic light and the target x, y coordinates are added as parameters. Then, YR, YG, and YB values for the input are determined from the respective data based on the above-described gamma correction calculation and Expression (3). Thereby, the color temperature required for all gradations can be reproduced.

  The color temperature adjustment based on the color temperature management can be performed as follows. That is, as described above, if the x, y coordinates of R, G, B are constant, the color temperature is determined by the mixture ratio of R, G, B regardless of the value of the luminance. That is, in order to achieve the function of changing the color temperature, the display color obtained by mixing R, G, and B becomes the target color temperature (target (x, y) point on the chromaticity diagram). An ideal γ characteristic curve as shown in FIG. 6 obtained by multiplying any one or a plurality of gamma correction calculation ideal γ characteristic curves (see FIG. 3) among three liquid crystal devices (light valves) by a constant. To decide. In FIG. 6, G and B are multiplied by different constants to shift the slopes of the G and B ideal γ characteristic curves. Thereafter, instead of the ideal γ characteristic curve of FIG. 3 used for the above-described calculation of the gamma correction characteristic, the ideal γ characteristic curve adjusted between the liquid crystal devices for R, G, B color light modulation as shown in FIG. May be used to perform gamma correction calculation.

  That is, as shown in FIG. 6, when the slopes of the VT characteristic curves are different between the liquid crystal devices, the video signal (DATA IN) of the same gradation data is input to the digital gamma correction circuit 220 and The video signal is subjected to gamma correction, the corrected video signal is supplied to the liquid crystal device 400, and the transmittance obtained therefrom is different from each other. Since the R, G, and B modulated color lights are synthesized and projected, the color balance can be adjusted by adjusting the slope of the VT characteristic curve. The adjustment of the inclination of the VT characteristic curve is performed for each color light in the digital gamma correction circuit 220 of FIG. 2 in the liquid crystal device for each color light, so that the color temperature of the display image is also corrected. Can do.

This color temperature correction is also due to the gamma correction of the digital video signal so that the bit number of the digital video signal is 10 bits output with respect to the input 8 bits. This is because the VT characteristic curve with a transmittance of 0% to 100% can be finely corrected and the characteristic curve inclination as shown in FIG. 6 can be set in detail.
(Explanation of signal processing circuit operation after gamma correction)
Next, signal processing performed in each liquid crystal device will be described.

  In the phase expansion circuit 230 shown in FIG. 2, as shown in FIG. 7, the 10-bit serial digital video signal D subjected to gamma correction is phase-expanded (serial-parallel conversion) into parallel digital video signals D1 to D6. Is. This phase expansion will be described with reference to FIG.

  As schematically shown in FIG. 7, the 10-bit serial video signal data D includes serial video signal data D1, D2,... Transferred according to a reference clock CLK of 40 MHz, for example. The video signal data D1, D2,... Are 10-bit data representing the gradation level of each pixel. In the phase expansion circuit, the video signal data D1, D2,... Are expanded by the shift register and the latch circuit so that the data cycle is 6 times the original, and the phase expanded 10-bit video signal data D1, D1. D2,... D6 are output in parallel.

  The method of FIG. 14 is called six-phase development and is used in the case of SVGA having a low pixel density. The writing frequency at this time is 6.7 MHz. On the other hand, in the case of XGA having a high pixel density, 12-phase expansion is used, and the writing frequency at this time is 5.4 MHz.

  Next, operations of polarity inversion, D / A conversion, and amplification will be described with reference to FIGS.

  FIG. 8A schematically shows, for example, a digital video signal D1, and shows a signal whose gradation value changes stepwise from 00h to FFh in each horizontal scanning period. In FIG. 8A, for convenience of explanation, gradation values are illustrated in an analog manner.

  The digital video signal D 1 shown in FIG. 8A is digitally inverted in polarity by the polarity inversion circuit 240. Here, the polarity of the digital video signal D1 is inverted every horizontal scanning period. On the other hand, the polarity of digital video signals D2 to D6 (not shown) is similarly inverted every horizontal scanning period. Accordingly, the liquid crystal pixel unit 410 of the liquid crystal device 400 performs “line inversion driving” in which the polarity of the voltage applied to the liquid crystal of the pixel is inverted every horizontal scanning period (each scanning line).

  A signal D1 'obtained by digitally inverting the digital video signal D1 every horizontal scanning period is as shown in FIG. In FIG. 8B, the polarity of the signal in the mth horizontal scanning period is not inverted, and the polarity of the signal in the (m + 1) th horizontal scanning period is inverted.

  The term “polarity” as used herein refers to the direction of the electric field applied to the liquid crystal between the pixel electrode and the common electrode in the pixel of the liquid crystal pixel unit 410. Inverting the polarity of the signal applies to the liquid crystal of the pixel. This means that the signal phase is changed so as to reverse the direction of the electric field.

  Here, as the digital polarity inversion method, for example, the following two methods can be cited. One of them is to invert the logic of a digital value, for example, to change 2-bit data (1, 1) to (0, 0). The other is to take the 2's complement of a digital value that is a binary number, for example, to change 2-bit data (1, 1) to (0, 1). Thus, the digital video signal D1 shown in FIG. 8A is converted into a digital video signal D1 'shown in FIG. 8B.

  In the case where the liquid crystal pixel unit 410 is an active matrix driving method and the switching element is formed of a thin film transistor, the polarity of the voltage applied to the liquid crystal is inverted with reference to the potential of the counter (common) electrode. Is done. When the switching element is a thin film diode (metal-insulation-metal), the polarity of the voltage applied to the liquid crystal is inverted with reference to the intermediate potential of the amplitude of the analog video signal output from the amplifiers 301 to 306. .

  The D / A converter 261 shown in FIG. 2 receives the digital video signal D1 'schematically shown in FIG. 8B, and performs digital-analog conversion on the digital video signal D1'. Note that the analog signal A1 output from the D / A converter 261 may be considered to be substantially similar to the digital signal D1 'schematically illustrated in FIG. Similarly, in the D / A converters 262 to 266, a video signal in which the signal phase is inverted every horizontal scanning period as shown in FIG. 8B is obtained. Even if the analog video signals output from the D / A converters 261 to 266 are inverted in signal phase every horizontal scanning period, the maximum amplitude and the minimum amplitude are constant, and are constant in any converter.

  In the operational amplifier 301 shown in FIG. 2, the amplitude-adjusted analog signal A1 is input to the plus terminal, the bias signal 307 whose potential level is inverted every horizontal scanning period is input to the minus terminal, and is amplified according to the equation (1). The signal V1 is output. This signal V1 is shown in FIG. The bias signal 307 is a reference for amplifying the analog video signals (A1 to A6) in FIG. 8B around the reference potential as shown in FIG. Is a signal.

  As shown in FIG. 8C, for example, when the liquid crystal device 400 is in the normally black mode, the signal V1 has a white level of 1V when driven with the first polarity (positive polarity) in the mth horizontal scanning period. The black level is 6V, and the white level is 11V and the black level is 6V when driven with the second polarity (negative polarity) in the (m + 1) th horizontal scanning period. At the time of driving with the first and second polarities, the voltage amplitude is 5 V, which coincides with the voltage amplitude 5 V at the full scale on the horizontal axis in FIG.

  In order to achieve the black level (transmittance 0%) in the first and second polarity driving, the output voltages from the amplifiers are the same at 6V. In the present embodiment, a voltage amplitude (5V) larger than the conventional voltage amplitude (about 3.8V) is used, but 6V is black level in the first and second polarity driving as described above. Therefore, the total voltage amplitude in the first and second polarity driving can be stopped to a minimum of 10V (1V to 11V).

  On the other hand, in the normally black mode, the output voltages from the amplifiers coincide with each other at 6V in order to realize the black level (transmittance 0%) in the first and second polarity driving, respectively.

  The VT characteristics in the embodiment of the present invention are described on the assumption of the normally black mode. However, when the liquid crystal device 400 is in the normally white mode, the relationship between the voltage and the transmittance is described above. Is reversed, and can be considered in the same manner as the normally black mode.

  Here, in this embodiment, it is not necessary to adjust the gain of the amplifier, as is apparent from the comparison between FIG. 1 and FIG. In the present embodiment, this adjustment is also unnecessary by minimizing the gain error of the operational amplifiers 301 to 306 itself.

  Here, as is clear from the above equation (1), the gain for the analog signal A1 is (1 + R2 / R1), and the gain for the bias signal 307 is (R2 / R1). Therefore, it can be seen that the gain of the operational amplifier 301 depends only on the resistance ratio (R2 / R1) regardless of the absolute values of the resistance values R1 and R2. Therefore, if the resistance ratio (R2 / R1) is constant in the operational amplifiers 301 to 306, the gain of the operational amplifiers 301 to 306 can be made constant.

  In this embodiment, the operational amplifiers 301 to 306 are formed so that the resistance ratio (R2 / R1) is constant, and the resistance values R1 and R2 are not variable but fixed.

  For this reason, the resistance values R1 and R2 to be paired are formed, for example, on the same substrate using the same thin film manufacturing process. In this way, each resistance layer for securing the resistance values R1 and R2 is formed of the same material with substantially the same thickness, and the width and length can be secured with high accuracy depending on the mask accuracy. For this reason, the accuracy of the resistance ratio (R2 / R1) is increased. As a result, the resistance ratio (R2 / R1) of each set of gain setting resistors connected to the operational amplifiers 301 to 306 can be made substantially equal.

  Here, the technique established in the semiconductor manufacturing process can be used for the thin film manufacturing process of the gain setting resistor. For example, a polysilicon layer is formed on a substrate having at least an insulating surface, and a resistance layer is formed by ion doping. After that, a resistor having a resistance ratio (R2 / R1) can be manufactured by performing a lithography process and performing resist coating, exposure, development, and etching for patterning.

In addition, in this embodiment, brightness adjustment is not necessary as described above, and thus it is not necessary to adjust various bias potentials of the polarity inversion bias signal 307.
(Modification of polarity inversion circuit)
The liquid crystal display device shown in FIG. 14 has an analog polarity inversion circuit 250 instead of the digital polarity inversion circuit 240 of FIG. Other configurations are the same as those of the embodiments described above.

In this case, the signals A1 ′ to A6 ′ output from the D / A converters 261 to 266 are analog video signals before polarity inversion. The analog polarity inversion circuit 250 receives analog video signals A1 ′ to A6 ′, and outputs analog video signals A1 to A6 that are inverted with a positive and negative polarity with respect to a reference potential in a predetermined cycle.
The analog video signals A1 to A6 are the same as those schematically shown in FIG. Thus, in the present invention, polarity inversion may be performed either digitally or analogly.

Furthermore, in the above-described embodiment, phase expansion is performed on a digital signal, but it may be performed on an analog signal after D / A conversion.
(Description of electronic equipment)
An electronic device configured using the above-described liquid crystal device includes a display information output source 1000, a display information processing circuit 1002, a display driving circuit 1004, a display panel 1006 such as a liquid crystal display device, a clock generation circuit 1008, and a power source illustrated in FIG. A circuit 1010 is included. The display information output source 1000 includes a memory such as a ROM and a RAM, a tuning circuit that tunes and outputs a television signal, and outputs display information such as a video signal based on a clock from the clock generation circuit 1008. To do. The display information processing circuit 1002 processes display information based on the clock from the clock generation circuit 1008 and outputs it. The display information processing circuit 1002 is a generic name including the A / D converter 100, the video signal processing circuit 200, and the amplifier 300 of FIG. The display driving circuit 1004 includes the scanning circuit 420 and the data driving circuit 430 shown in FIG. 2, and drives the liquid crystal panel 1006 for display. The power supply circuit 1010 supplies power to each of the circuits described above.

  As an electronic apparatus having such a configuration, a liquid crystal projection display device shown in FIG. 10, a personal computer (PC) and engineering work station (EWS) corresponding to multimedia shown in FIG. 11, a pager shown in FIG. , A word processor, a television, a viewfinder type or a monitor direct-view type video tape recorder, an electronic notebook, an electronic desk calculator, a car navigation device, a POS terminal, and a device equipped with a touch panel.

  The projection display device shown in FIG. 10 is a projection projection display device using a transmissive liquid crystal device as a light valve, and uses, for example, a prism synthesis type optical system. In FIG. 10, in the projection display apparatus 1100, the projection light emitted from the lamp unit 1102 of the white light source is converted into R, G, and B by a plurality of mirrors 1106 and two dichroic mirrors 1108 inside the light guide 1104. It is divided into primary colors and led to three liquid crystal devices 1110R, 1110G and 1110B which display images of the respective colors. Each liquid crystal device has a circuit block as shown in FIGS. The light modulated by the respective liquid crystal devices 1110R, 1110G, and 1110B is incident on the dichroic prism 1112 from three directions. In the dichroic prism 1112, the red R and blue B lights are bent by 90 °, and the green G light travels straight, so that the images of the respective colors are synthesized and a color image is projected onto a screen or the like through the projection lens 1114.

  A personal computer 1200 shown in FIG. 11 includes a main body 1204 provided with a keyboard 1202 and a liquid crystal display screen 1206.

  12 includes a liquid crystal panel substrate 1304, a light guide 1306 provided with a backlight 1306a, a circuit substrate 1308, first and second shield plates 1310 and 1312, and two elastic conductors. It has a body 1314, 1316 and a film carrier tape 1318. Two elastic conductors 1314 and 1316 and a film carrier tape 1318 connect the liquid crystal panel substrate 1304 and the circuit substrate 1308.

  Here, the liquid crystal panel substrate 1304 is obtained by enclosing liquid crystal between two transparent substrates 1304a and 1304b, thereby constituting at least a dot matrix type liquid crystal device. A driving circuit 1004 shown in FIG. 9 or a display information processing circuit 1002 can be formed on one transparent substrate. A circuit that is not mounted on the liquid crystal panel substrate 1304 is an external circuit of the liquid crystal panel substrate, and can be mounted on the circuit substrate 1308 in the case of FIG.

  FIG. 12 shows the configuration of the pager. Therefore, a circuit board 1308 is necessary in addition to the liquid crystal panel board 1304. In the case where a liquid crystal display device is used as one component for electronic equipment, When a display drive circuit or the like is mounted, the minimum unit of the liquid crystal display device is a liquid crystal panel substrate 1304. Or what fixed the liquid crystal panel board | substrate 1304 to the metal frame 1302 as a housing | casing can also be used as a liquid crystal display device which is one component for electronic devices. Further, in the case of the backlight type, a liquid crystal display device can be configured by incorporating a liquid crystal panel substrate 1304 and a light guide 1306 provided with a backlight 1306a in a metal frame 1302. Instead of these, as shown in FIG. 13, a TCP in which an IC chip 1324 is mounted on a polyimide tape 1322 having a metal conductive film formed on one of two transparent substrates 1304a and 1304b constituting a liquid crystal panel substrate 1304. (Tape Carrier Package) 1320 can be connected to be used as a liquid crystal display device which is one component for electronic equipment.

  As described above, the liquid crystal device as an example of the electro-optical device described in the embodiment of the present invention can be used in various electronic devices as a liquid crystal display device or a light valve.

  In addition, this invention is not limited to the said Example, A various deformation | transformation implementation is possible within the range of the summary of this invention. For example, the electro-optical device according to the present invention is not limited to the above-described liquid crystal device, but can be applied to various electro-optical devices such as electroluminescence, plasma display, and FED.

1 is a block diagram of a liquid crystal display device according to an embodiment of an electro-optical device according to the invention. FIG. 2 is a block diagram illustrating details of a signal processing circuit, an amplification block, and a liquid crystal device in FIG. 1. FIG. 3 is a characteristic diagram showing an applied voltage-characteristic specific to the liquid crystal device shown in FIG. 2. FIG. 3 is a characteristic diagram showing the relationship between the gradation value of the video signal input to the digital gamma correction circuit shown in FIG. 2 and the gradation value of the video signal after gamma correction. FIG. 4 is a characteristic diagram illustrating a relationship between a gradation value and a transmittance of a video signal after being gamma-corrected according to the characteristic illustrated in FIG. 3. FIG. 6 is a characteristic diagram illustrating an ideal gamma characteristic obtained after color temperature correction is simultaneously performed during gamma correction with respect to the characteristic of FIG. 5. It is a figure which shows a phase expansion | deployment (parallel-serial conversion) typically. (A)-(C) are figures which show typically a phase-expanded digital video signal, a polarity inversion signal, and an amplified analog video signal. 1 is a block diagram of a liquid crystal display device which is an example of an electro-optical device according to the invention. It is a schematic explanatory drawing of the projection type display apparatus which is an example of the electronic device which concerns on this invention. It is a schematic perspective view of the personal computer which is an example of the electronic device which concerns on this invention. It is a disassembled perspective view of the pager which is an example of the electronic device which concerns on this invention. It is a schematic perspective view which shows the example which mounted the video signal processing circuit in TCP. It is a block diagram of a liquid crystal display device using an analog polarity inversion circuit. It is a block diagram of the conventional liquid crystal display device. FIG. 16 is a characteristic diagram illustrating a relationship of applied voltage (V) −transmittance (T) unique to the liquid crystal device (LCD) illustrated in FIG. 15. FIG. 16 is a characteristic diagram illustrating a relationship between a gradation value and transmittance of a digital video signal after brightness adjustment and gain adjustment in the liquid crystal device illustrated in FIG. 15. FIG. 16 is a characteristic diagram showing a relationship between a gradation value of a digital video signal before gamma correction used in the liquid crystal device of FIG. 15 and a gamma correction characteristic. FIG. 19 is a characteristic diagram showing a relationship between a gradation value and a transmittance of a digital video signal after gamma correction according to the characteristic of FIG. 18.

Explanation of symbols

  100 analog-digital converter, 200 video signal processing circuit, 210 ASIC, 220 digital gamma correction circuit, 230 phase expansion circuit, 240 digital polarity inversion circuit, 250 analog polarity inversion circuit, 260 digital-analog conversion block, 261-266 digital -Analog converter, 300 amplification block, 301-306 operational amplifier, 400 liquid crystal device, 410 liquid crystal pixel unit, 420 scanning circuit, 430 data drive circuit

Claims (12)

An electro-optical device whose light transmittance changes based on a voltage applied to the electro-optical material;
A digital gamma correction circuit for gamma correcting a digital video signal;
A digital polarity inverting circuit for digitally inverting the polarity of the digital video signal output from the digital gamma correction circuit every predetermined period;
A digital-analog conversion circuit for converting a digital video signal from the digital polarity inversion circuit into an analog video signal;
A gain is set by a resistance ratio of a pair of fixed resistors formed on the same substrate by the same manufacturing process, and the voltage applied to the electro-optic material by amplifying the analog video signal at a predetermined cycle An amplifier for reversing the polarity, and
The digital gamma correction circuit converts the n-bit digital video signal into an N (N ≧ n + 2) bit digital signal based on a gamma correction characteristic predetermined according to an applied voltage-transmittance characteristic unique to the electro-optical device. Convert to video signal,
The fixed resistor includes a first resistor connected to the negative input terminal of the amplifier, and a second resistor connected to a negative feedback path between the output terminal of the amplifier and the negative input terminal. Have
The analog video signal from the digital-analog conversion circuit is input to the positive input terminal of the amplifier,
A bias signal whose potential level is inverted every horizontal scanning period is input to the negative input terminal of the amplifier via the first resistor.
When the resistance value of the first resistor is R1 and the resistance value of the second resistor is R2, the gain of the analog video signal input to the positive input terminal is (1 + R2 / R1). A display device, wherein the gain of the bias signal input to the negative input terminal is R2 / R1. In claim 1,
The display device, wherein the gamma correction characteristic of the digital gamma correction circuit is predetermined according to an applied voltage-transmittance characteristic specific to the electro-optical device in the entire range of transmittance of 0% to 100%. In claim 1 or 2,
The display device, wherein the digital gamma correction circuit performs conversion of a digital video signal by performing at least one of bias adjustment and gain adjustment of a video signal applied to the electro-optic material. In any one of Claims 1 thru | or 3,
A voltage having a first polarity and a second polarity is applied to the electro-optic material at the predetermined period,
When realizing either one of the maximum and minimum transmittances in the electro-optical device, the voltage output from the amplifier is substantially the same voltage when the voltages of the first and second polarities are applied. A display device characterized by that. An electro-optical device that corrects an applied voltage-transmittance characteristic unique to an electro-optical device whose light transmittance changes based on a voltage applied to the electro-optical material, and applies a polarity-inverted voltage to the electro-optical material. In the driving method,
Gamma correction of digital video signal,
The gamma-corrected digital video signal is digitally inverted in polarity at predetermined intervals,
Digitally inverted digital video signal is converted to analog video signal,
The analog video signal is amplified by an amplifier whose gain is set by a resistance ratio of a pair of fixed resistors formed on the same substrate by the same manufacturing process,
Applying a voltage to the electro-optic material based on the amplified analog video signal,
When the gamma correction is performed, the digital image signal of n bits is converted into N (N ≧ n + 2) bits based on a gamma correction characteristic predetermined according to an applied voltage-transmittance characteristic unique to the electro-optical device. Convert to digital video signal,
When the amplifier amplifies, as the fixed resistor, a first resistor connected to the negative input terminal of the amplifier, and a negative feedback path between the output terminal and the negative input terminal of the amplifier A second resistor connected to the
The analog video signal from the digital-analog conversion circuit is input to the positive input terminal of the amplifier, and the negative input terminal of the amplifier is connected to each horizontal scanning period via the first resistor. A bias signal whose potential level is inverted is input to
When the resistance value of the first resistor is R1 and the resistance value of the second resistor is R2, the gain of the analog video signal input to the positive input terminal is (1 + R2 / R1). A driving method of an electro-optical device, wherein a gain of a bias signal input to the negative input terminal is R2 / R1. In claim 5,
A method for driving an electro-optical device, wherein when performing the gamma correction, a digital video signal is converted by adjusting a bias and a gain of a video signal applied to the electro-optical material.   An electronic apparatus comprising the display device according to claim 1. An electronic apparatus comprising a plurality of electro-optical devices whose light transmittance changes based on a voltage applied to an electro-optical material, and combining and displaying light modulated by the plurality of electro-optical devices,
Each of the electro-optical devices is
A digital gamma correction circuit for gamma correcting a digital video signal;
A digital polarity inverting circuit for digitally inverting the polarity of the digital video signal output from the digital gamma correction circuit every predetermined period;
A digital-analog conversion circuit for converting a digital video signal from the digital polarity inversion circuit into an analog video signal;
A gain is set by a resistance ratio of a pair of fixed resistors formed on the same substrate by the same manufacturing process, and the voltage applied to the electro-optic material by amplifying the analog video signal at a predetermined cycle An amplifier for reversing the polarity, and
Each digital gamma correction circuit converts the n-bit digital video signal into N (N ≧ n + 2) bits based on a gamma correction characteristic predetermined according to an applied voltage-transmittance characteristic specific to each electro-optical device. Respectively converted into digital video signals
The fixed resistor includes a first resistor connected to the negative input terminal of the amplifier, and a second resistor connected to a negative feedback path between the output terminal of the amplifier and the negative input terminal. Have
The analog video signal from the digital-analog conversion circuit is input to the positive input terminal of the amplifier,
A bias signal whose potential level is inverted every horizontal scanning period is input to the negative input terminal of the amplifier via the first resistor.
When the resistance value of the first resistor is R1 and the resistance value of the second resistor is R2, the gain of the analog video signal input to the positive input terminal is (1 + R2 / R1). A gain of a bias signal input to the negative input terminal is R2 / R1. In claim 8,
The digital gamma correction circuit digitally adjusts the gradation data and the corresponding transmission characteristic curve of the electro-optical device so that the plurality of electro-optical devices are substantially equal to each other or have similar shapes to each other. An electronic device characterized by being converted into a video signal. In claim 8 or 9,
The electronic gamma correction circuit performs at least one of bias adjustment and gain adjustment of a video signal applied to the electro-optic material and converts it into a digital video signal. In claim 8,
The plurality of electro-optical devices modulate different colored lights,
The electronic apparatus according to claim 1, wherein the digital gamma correction circuit corresponding to the plurality of electro-optical devices corrects the color temperature indicated by the combined light of the color lights modulated by the electro-optical devices. In claim 11,
The digital gamma correction circuit corresponding to the plurality of electro-optical devices adjusts the slope of the characteristic curve of the transmittance of the electro-optical device corresponding to gradation data between the plurality of electro-optical devices, so that the color An electronic device characterized by performing temperature correction.

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