JP2006071940A - Electrooptical device, projection type display device and electronic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrooptical device which displays a high quality image by appropriately setting a precharge potential in accordance with the image signals to be displayed, and also to provide a projection type display device and electronic equipment. <P>SOLUTION: The electrooptical device displays inputted image signals on a display section which is constituted, for example, of a liquid crystal device. As the image signals, AV system image signals inputted from an AV equipment such as a DVD player, for example and data system image signals such as PC displayed images are inputted. The display section of the liquid crystal device or the like is constituted so as to display image signals by precharging a signal line for every one line of the image signals, wherein the precharge potential is determined according to the inputted image signals. In other words, the precharge potential can be changed in both cases that AV system image signals are inptted and that data system image signals are inputted. Thus, an appropriate precharge potential is applied in accordance with properties of the inputted image signals, and a high quality image is displayed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electro-optical device such as a liquid crystal device that performs precharging during image display.

  In an active matrix liquid crystal device or the like, an operation of writing data to a liquid crystal layer of each pixel is performed by dot sequential driving through switching elements such as TFTs (thin film transistors) connected to a plurality of scanning signal lines. In addition, in order to eliminate display unevenness due to voltage deviation of the liquid crystal and prevent deterioration of the liquid crystal due to direct current applied to the liquid crystal, polarity inversion driving is performed to invert the polarity of the voltage applied to the liquid crystal at a predetermined timing. Yes. The polarity inversion driving is a driving method in which a voltage having a different polarity (positive or negative polarity) is applied to one end of the liquid crystal with reference to a potential applied to the other end of the liquid crystal.

  In the liquid crystal device as described above, a method of performing a precharge by writing a predetermined potential (hereinafter referred to as a “precharge potential”) to a signal line prior to data writing during a horizontal scanning period of an image signal. Are known. For example, Patent Document 1 describes a method of suppressing potential fluctuation of a video line by writing an arbitrary intermediate potential as a precharge potential. Patent Document 2 describes a method of correcting vertical crosstalk and the like by writing a predetermined potential as a precharge potential.

JP-A-4-295521 JP 2003-202847 A

  It is an object of the present invention to provide an electro-optical device, a projection display device, and an electronic apparatus that can display a high-quality image by appropriately setting a precharge potential according to an image signal to be displayed. .

  In one aspect of the present invention, an electro-optical device includes: an input unit that receives an image signal; a precharge potential setting unit that sets a precharge potential before applying the image signal based on the image signal; A display unit that precharges the signal line with the precharge potential for each line of the image signal and displays an image corresponding to the image signal, and the input unit receives an AV image signal. And a second input unit to which a data system image signal is input. The precharge potential setting unit has the image signal input to the first input unit. Sometimes, the precharge potential is set to a first precharge potential, and the precharge potential is set to a second precharge potential when the image signal is input to the second input portion.

  The electro-optical device displays an input image signal on a display unit configured by, for example, a liquid crystal device. As the image signal, for example, an AV image signal input from an AV device such as a DVD player and a data image signal such as a display image of a PC are input. A display unit such as a liquid crystal device is configured to display an image signal by precharging a signal line for each line of the image signal. Here, the precharge potential is determined based on the input image signal. That is, the precharge potential is changed when an AV image signal is input and when a data image signal is input. Since the input unit to which the AV system image signal is input and the input unit to which the data system image signal is input are provided independently, by detecting the presence or absence of the physical input of the image signal to each input unit Which image signal is input can be determined, and the precharge potential can be set according to the result. As a result, an appropriate precharge potential can be applied according to the nature of the input image signal, and high-quality image display is possible.

  Another aspect of the electro-optical device includes a frame memory that stores an image input to the input unit, and a variation amount calculation unit that calculates a variation amount of the image signal stored in the frame memory. The precharge potential setting unit sets the precharge potential to a first precharge potential when the variation amount exceeds a predetermined amount, and the precharge potential when the variation amount is equal to or less than the predetermined amount. Is set to the second precharge potential.

  In this aspect, the input image signal is temporarily stored in the frame memory, and the contents thereof are analyzed. Specifically, the fluctuation amount of the image signal temporarily stored in the frame memory is calculated, and it is determined whether or not the fluctuation amount is a predetermined amount or less. If the fluctuation amount is equal to or less than the predetermined amount, the image can be determined to be an image with little motion, such as an image when an application is executed on the PC, and the second precharge potential is set. On the other hand, if the fluctuation amount is larger than the predetermined amount, it can be determined that the image is a large motion image such as a natural image or a moving image, and therefore the first precharge potential is set. In this way, an appropriate precharge potential can be set based on the contents and properties of the input image.

  In another aspect of the electro-optical device, a memory capable of storing at least one line of the image signal input to the input unit, and a fluctuation amount of the image signal for one line stored in the memory are stored. A fluctuation amount calculation unit for calculating, and when the fluctuation amount exceeds a predetermined amount, the precharge potential setting unit sets the precharge potential for the one line to a first precharge potential, and the fluctuation When the amount is equal to or less than the predetermined amount, the precharge potential for the one line is set to the second precharge potential.

  In this aspect, the input image signal is temporarily stored in a memory capable of storing an image signal for at least one line such as a frame memory or a line memory, and the contents thereof are analyzed. Specifically, the fluctuation amount of the image signal for one line temporarily stored in the frame memory is calculated, and it is determined whether or not the fluctuation amount is a predetermined amount or less. If the fluctuation amount is equal to or smaller than the predetermined amount, it can be determined that the image of the line is an image with little motion, such as an image when the application on the PC is executed. Set the charge potential. On the other hand, if the fluctuation amount is larger than the predetermined amount, it can be determined that the image of the line is a large-motion image such as a natural image or a moving image, and therefore the first precharge potential is applied to the line. Set. In this way, an appropriate precharge potential can be set for each line based on the contents, properties, etc. of the input image.

  In another aspect of the electro-optical device, the fluctuation amount calculation unit calculates, for each pixel constituting the image signal, a fluctuation amount in a pixel unit with respect to a pixel adjacent to the pixel, and the fluctuation in the pixel unit. The amount of variation is calculated based on the amount. In this aspect, the amount of spatial variation of the image signal is calculated, and an image with a large amount of variation can be determined as a natural image, a moving image, or the like with a large change in image content in one frame image.

  In another aspect of the electro-optical device, the fluctuation amount calculation unit calculates, for each pixel constituting the image signal, a fluctuation amount in units of pixels with respect to a pixel corresponding to the pixel in the preceding and following frames, and The amount of variation is calculated based on the amount of variation in pixel units. In this aspect, the temporal variation amount of the image signal is calculated, and an image having a large variation amount, that is, an image having a large motion can be determined as a moving image or the like.

  In a preferred embodiment, the first precharge potential can be a predetermined potential between a minimum potential and a maximum potential applied to the signal line during image display. As a result, the AV image signal can be displayed with high quality.

  In another preferred embodiment, the second precharge potential is closer to the minimum potential than an intermediate potential between a minimum potential and a maximum positive potential when a positive potential is applied to the signal line during the image display. When a negative potential is applied to the signal line, the potential can be made closer to the negative maximum potential between the minimum potential and the negative maximum potential. As a result, the influence of crosstalk can be removed and the data system image signal can be displayed with high quality.

  According to the present invention, there is provided a projection display device comprising a light source, the electro-optical device that modulates the light emitted from the light source, and a projection unit that projects the light modulated by the electro-optical device. can do. In addition, an electronic apparatus including an image signal acquisition unit that acquires the image signal from the outside and the above-described electro-optical device that displays the image signal so as to be visible can be configured.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

[Image display device]
FIG. 1 shows a schematic configuration of an image display device which is an embodiment of the electro-optical device of the invention. In FIG. 1, an image display device 10 is a device that receives an image signal from an external AV signal source 12 or a data signal source 14 and displays it. Examples of the AV signal source 12 include a DVD player and a hard disk player that output digital image signals. Examples of the data signal source 14 include a personal computer (PC) capable of displaying and browsing a moving image signal. An AV system image signal Sa is input from the AV system signal source 12 to the image display apparatus 10, and a data system image signal Sd is supplied from the data system signal source 14 to the image display apparatus 10.

  The image display device 10 includes a controller 16 and a liquid crystal display device 20. The liquid crystal display device 20 functions as a display unit that displays an image signal supplied from the AV signal source 12 or the data signal source 14. In addition, “display” here refers to, for example, a case where an image signal is displayed in a state that the user can visually recognize, such as a display, or a user directly such as a light valve inside a projection projector. This includes the case where an image signal is displayed as a means for modulating the projection light instead of being visible.

  The controller 16 supplies the image signal Sa or Sb supplied from the outside to the liquid crystal display device 20 as the display image signal S. Further, the controller 16 generates a potential instruction signal Sc indicating a precharge potential for precharging performed when displaying an image on the liquid crystal display device 20 based on the image signal Sa or Sb supplied from the outside. 20 is supplied. Thereby, although details will be described later, the controller 16 determines a precharge potential suitable for the image signal Sa or Sb input from the outside, and the liquid crystal display device 20 inputs the input based on the precharge potential determined by the controller 16. By performing precharging at a precharge potential suitable for the image signal Sa or Sb to be performed, high-quality image display can be performed.

  Next, the internal configuration and precharge of the liquid crystal display device 20 will be described. FIG. 2 is a schematic block diagram showing the internal configuration of the liquid crystal display device 20. The liquid crystal display device 20 shown in FIG. 1 is an active matrix system, and includes gate lines 2 arranged in the row direction and signal lines 5 arranged in the column direction. At each intersection of the gate line 2 and the signal line 5, a thin film transistor (hereinafter referred to as "TFT") 6 which is a switching element, and a liquid crystal pixel 7 composed of a liquid crystal layer and a pixel electrode are provided. The source electrode of the TFT 6 is connected to the corresponding signal line 5, the gate electrode is connected to the corresponding gate line 2, and the drain electrode is connected to the corresponding liquid crystal pixel 7.

  Each gate line 2 is connected to a V driver 1 as a vertical scanning circuit. The V driver 1 supplies selection pulses VS1 to VSn to each gate line 2 based on a predetermined clock VCLK and a vertical start pulse VST. As a result, the gate lines 2 are sequentially scanned, and one line (one row) of liquid crystal pixels 7 are selected every horizontal period.

  Each signal line 5 is connected to the video potential line 8 via the sampling switching 9. A video output signal VI is input from the signal driver 3 to the video potential line 8. Note that the video signal S is input from the controller 16 to the signal driver 3.

  In addition, the H driver 4 performs switching control of each sampling switch 9 by supplying switching signals HS1 to HSn based on a predetermined clock signal HCLK and a horizontal start signal HST. That is, the H driver 4 sequentially transfers the horizontal start pulse HST in synchronization with the clock signal HCLK, outputs the switching signals HS1 to HSn, and opens and closes the sampling switch 9. The H driver 4 and the sampling switch 9 constitute a horizontal scanning circuit. The sampling switch 9 samples the video output signal VI for each signal line 5, and outputs the video output signal VI to the liquid crystal pixels 7 for one line selected within one horizontal period via the TFT 6 in a conductive state. Write.

  The liquid crystal display device 20 includes a precharge circuit 30 and supplies a predetermined precharge signal VP to each signal line 2 immediately before writing the video output signal VI to the liquid crystal pixels 7 for one line. The precharge circuit 30 supplies each precharge by supplying a signal source 31 for generating a precharge signal VP, a plurality of precharge switches 33 connected to the ends of the signal lines 5, and switching signals PS1 to PSn. And a controller 32 that applies the precharge signal VP to each signal line 5 by opening and closing the switches 33 all at once. The signal source 31 generates a precharge signal VP having an appropriate precharge potential based on the potential instruction signal Sc supplied from the controller 16. In the example shown in FIG. 2, the precharge circuit 30 is provided independently of the horizontal scanning circuit, but the precharge circuit 30 may be configured as a part of the horizontal scanning circuit.

  Next, the operation of the liquid crystal display device 20 will be described with reference to FIG. The vertical clock signal VCLK (not shown) input to the V driver 1 has a pulse width corresponding to one horizontal period (1 line: 1H), and the vertical start pulse VST indicates the start of one vertical period. The horizontal start pulse HST input to the H driver 4 indicates the start of one horizontal period. As shown in FIG. 3, there are n horizontal periods (that is, n lines) as indicated by the horizontal start pulse HST within one vertical period indicated by the vertical start pulse VST.

  On the other hand, the switching signal PS supplied from the control unit 32 in the precharge circuit 30 is used in the ineffective period before the horizontal start pulse HST, for example, in the horizontal block so that the writing of the precharge potential does not affect the display image. Output within the ranking period. Thereby, before the video output signal VI corresponding to each line is written in the liquid crystal pixel 7, the precharge potential is written in the signal line 5 in units of lines.

  The video output signal VI output from the signal driver 3 via the video potential line 8 is inverted in polarity every horizontal period, and is AC driven. Accordingly, the polarity of the precharge signal VP output from the signal source 31 is inverted every horizontal period, so that the polarity matches that of the video output signal VI.

  Next, the precharge potential will be described. In FIG. 3, the precharge signal VPa shown in the middle stage is a case where the image signal to be displayed is an image signal supplied from the AV signal source 12, or a natural image or an image with relatively large fluctuation such as a moving image. Is a first precharge potential (hereinafter referred to as an “AV system precharge potential”), and is set to an intermediate potential between the maximum potential and the minimum potential applied to the signal line 5 during image display. Specifically, in the case of normally white display, the center potential VC corresponds to the minimum potential corresponding to the white level in the positive video potential period, and the upper potential VH in the figure corresponds to the maximum corresponding to the black level. Corresponds to the potential. In this case, the AV precharge signal VPa is set to a predetermined intermediate potential VPap between the minimum potential VC corresponding to the white level and the maximum potential VH corresponding to the black level. On the other hand, in the negative video potential period, the central potential VC corresponds to the minimum potential corresponding to the white level, and the lower potential VH in the drawing corresponds to the maximum potential corresponding to the black level. In this case, the AV precharge signal VPa is set to a predetermined intermediate potential Vpan between the minimum potential VC corresponding to the white level and the maximum potential VL corresponding to the black level.

  As described above, by writing the intermediate potential between the white level potential and the black level potential as the precharge potential before writing the signal of each line, the potential change when the output video signal VI is written to the individual signal lines 5 thereafter. Becomes smaller and the charge / discharge amount becomes smaller. Therefore, the potential fluctuation of the video potential line 8 and the like can be suppressed, and AV image signals such as natural images and moving images can be displayed with high quality.

  On the other hand, in FIG. 3, the lower precharge signal VPd is a second precharge potential (hereinafter referred to as “data”) used when the image signal to be displayed is an image signal supplied from the data signal source 14. Called system precharge potential). The data system precharge potential VPd is set to a potential VPdp closer to the minimum potential VC than the intermediate potential between the minimum potential VC and the positive maximum potential VH when a positive potential is applied to the signal line 5 during the positive video potential period. In the side video potential period, that is, when a negative potential is applied to the signal line 5, the potential VPdn is set closer to the negative maximum potential VL than the intermediate potential between the minimum potential VC and the negative maximum potential VL.

  The reason for setting the data system precharge potential in this way will be described. In a liquid crystal device that performs liquid crystal display using light from a light source, for example, a projection type liquid crystal device such as a projector, optical crosstalk becomes a problem. Optical crosstalk means that carriers are generated by light in a switching element formed on a substrate, for example, a TFT, and charge accumulated in a pixel connected to the TFT leaks, and the signal line connected to the TFT leaks. This is a phenomenon in which the charge accumulated in the pixel fluctuates due to the potential. Degradation of image quality occurs due to this optical crosstalk. In particular, image quality degradation due to optical crosstalk is significant when a negative voltage is applied. The reason is that when a negative voltage is applied, the voltage charged to the pixel always fluctuates unilaterally in the positive polarity direction, that is, on the white side on the display. This is because a display gradation difference is generated between the two pixels to be subjected to the tone display.

  In contrast, in the present embodiment, as shown in the lower part of FIG. 3, the precharge potential VPdn in the negative video potential period is set near the maximum potential VL regardless of the gradation level of the pixel connected to the signal line. The precharge potential VPdp in the positive video potential period is set near the minimum potential. As a result, even if an optical crosstalk occurs due to the switching element of the pixel when a negative charge voltage is charged for the halftone display in the pixel, the signal line to which the pixel is connected is charged. The precharge potential VPdn lower than the charged voltage is periodically applied, and the positive precharge potential VPdp and the signal potential higher than the charged charge voltage are periodically applied. The potential can be prevented from fluctuating unilaterally and image quality deterioration can be suppressed.

[Precharge potential determination method]
Next, a method for determining a precharge potential, which is a feature of the present invention, will be described.

(First embodiment)
FIG. 4 is a flowchart showing the process of the controller 16 of the liquid crystal display device 20 according to the first embodiment. The process shown in FIG. 4 can be executed by, for example, a CPU (not shown) in the controller 16 shown in FIG. First, the image signal Sa or Sd is input to the controller 16 from either the AV signal source 12 or the data signal source 14 (step S1). The controller 16 is provided with connector terminals for receiving image signal inputs from the AV signal source 12 and the data signal source 14, respectively. In general, an image signal input connector terminal from an AV signal source 12 such as a DVD player uses an S video terminal or PIN terminal, and an image signal input connector from a data signal source 14 such as a PC. As the terminal, a DVI terminal, an analog D-Sub terminal, or the like is used. Therefore, the controller 16 detects to which terminal the image signal is input, thereby determining whether the input image signal is the AV image signal Sa or the data image signal Sd. Determine (step S2).

  When the input image signal is the data system image signal Sd (step S2; Yes), the controller 16 determines to use the data system precharge potential (step S3), and the potential instruction signal Sc indicating that fact is used. The data system image signal Sd is supplied to the liquid crystal display device 20 (step S5).

  On the other hand, if the input image signal is the AV image signal Sa (step S2; No), the controller 16 decides to use the AV system precharge potential (step S4), and a potential instruction indicating that fact. The signal Sc and the data system image signal Sa are supplied to the liquid crystal display device 20 (step S5).

  As a result, the liquid crystal display device 20 displays an image signal while performing precharge at the corresponding precharge potential. In the above example, the CPU or the like in the controller 16 determines the AV system / data system image signal and determines the precharge potential by software processing, but the controller 16 is configured by a hardware circuit. You can also. For example, the presence / absence of a signal input to each input terminal is detected by a signal potential or the like, and a potential instruction signal Sc indicating either the AV system precharge potential or the data system precharge potential is output to the liquid crystal display device 20 according to the voltage level. A circuit may be used.

(Second embodiment)
Next, a second embodiment of the method for determining the precharge potential will be described. In the first embodiment, the precharge potential is determined based on the presence / absence of a physical signal input to the image signal input terminal. On the other hand, in the second embodiment, the precharge potential is determined based on the characteristics of the input image signal, specifically, whether or not the input image signal has many fluctuation components (motion components).

  The configuration of the image display device 10a in the second embodiment is shown in FIG. In the image display apparatus according to the second embodiment, a CPU 17 and a frame memory 18 are provided in the controller 16 in order to analyze an input image signal. The CPU 17 temporarily stores the image signal Sa or Sd input from the outside in the frame memory 18 by executing a predetermined program, and analyzes the image. Then, based on the analysis result, the precharge potential is determined, and the corresponding potential instruction signal Sc is supplied to the liquid crystal display device 20.

  Specifically, the controller 16 calculates the fluctuation amount of the input image signal. The calculation method of the fluctuation amount is shown in FIGS. 6 (a) and 6 (b). In the first variation amount calculation method, as shown in FIG. 6, after the input image signal is developed in the frame memory 16, the difference between the gradation value of a specific pixel and the gradation values of surrounding pixels. It is determined whether or not is large. That is, the amount of spatial variation is detected. FIG. 6A illustrates the value of a predetermined upper bit of the input image signal (for example, the fifth bit or the sixth bit when the input image signal is 6 bits). By comparing the value of the predetermined bit at the top of each pixel, it is possible to determine whether or not the difference between the gradation values of these pixels is large. For example, when a pixel 42 in FIG. 6 (a) is compared with the value of a predetermined bit at the top of eight pixels 43 located in the vicinity thereof, and the sum of the differences is not less than a predetermined value, the pixel is It can be determined that the fluctuation is large. If the same processing is performed for all the pixels, it is possible to calculate the proportion of pixels with large fluctuations in all the pixels of the frame image. Therefore, when the ratio is larger than the predetermined ratio, it can be determined that the variation amount of the frame image is large.

  FIG. 6B shows a second calculation method of the fluctuation amount. In the first calculation method, the amount of spatial variation between pixels in one frame image is calculated, but in the second calculation method, temporal variation between corresponding pixels between adjacent frame images. The amount (motion amount) is calculated. Specifically, as shown in FIG. 6B, the value of the upper predetermined bit is compared for a certain k-th frame image and the (k + 1) -th frame image, and the difference between the two is equal to or greater than the predetermined value. In this case, it can be determined that the variation between the frame images is large.

  For example, the controller 16 can determine whether or not the fluctuation amount of the input image signal is larger than a predetermined amount by using one or both of the first and second calculation methods. Note that any of the above-described fluctuation amount calculation methods is merely an example, and it is of course possible to apply various motion detection methods known in the field of image processing.

  The processing of the controller 16 in the second embodiment will be described with reference to the flowchart of FIG. First, the controller 16 receives the image signal Sa or Sd from the AV signal source 12 or the data signal source 14 (step S11).

  Next, the controller 16 calculates the fluctuation amount of the input image signal by the above-described method (step S12), and determines whether or not the fluctuation amount is equal to or less than a predetermined amount (step S13). When the fluctuation amount is larger than the predetermined amount (step S13; No), the controller 16 determines that the image signal is a natural image or a moving image, and determines to use the AV system precharge potential (step S15). On the other hand, when the fluctuation amount is equal to or smaller than the predetermined amount (step S13; Yes), the controller 16 determines that the image signal is an image signal of an application on the PC and determines to use the data system precharge potential. (Step S14).

  When the precharge potential to be used is determined in this way, the controller 16 outputs the image signal and the potential instruction signal Sc indicating the determined precharge potential to the liquid crystal display device 20 (step S16). Thus, the determination of the precharge potential is completed. Thereafter, the liquid crystal display device 20 displays an image signal by performing precharge at a precharge potential corresponding to the potential instruction signal Sc.

  As described above, in the second embodiment, an appropriate precharge potential is determined based on the characteristics of the input image signal, specifically, whether or not the fluctuation amount is large, so that it can be more accurately adapted to the content of the image signal. It is possible to perform precharge. For example, even if an image signal is output from a data system signal source such as a PC, the image signal has a large amount of fluctuation when an application for reproducing moving images such as MPEG is operating on the PC, and the AV system precharge In some cases, it is preferable to perform precharging at a potential. According to the second embodiment, in such a case, appropriate precharge can be performed according to the characteristics of the image signal, and high-quality image display can be performed.

(Third embodiment)
The second embodiment is a combination of the first embodiment and the second embodiment. First, similarly to the first embodiment, the presence or absence of a physical image signal input is detected at an input terminal or the like, and the AV When a system image signal is input, an AV system precharge potential is used. On the other hand, as described above, the data system image signal may actually include a moving image such as MPEG or a natural image taken by a digital still camera. The signal is analyzed, and an appropriate AV system precharge potential or data system precharge potential is determined according to the amount of variation. In the third embodiment, the image display device 10a shown in FIG. 5 is used as in the second embodiment.

  Next, the processing of the controller 16 in the third embodiment will be described with reference to the flowchart of FIG. First, the image signal Sa or Sd is input to the controller 16 from either the AV signal source 12 or the data signal source 14 (step S20). The controller 16 determines which terminal the image signal is input to, thereby determining whether the input image signal is the AV image signal Sa or the data image signal Sd. (Step S21). As in the first embodiment, this is performed by detecting the presence or absence of a physical signal input via a connector terminal or the like.

  If the input image signal is not a data system image signal (step S21; No), the controller 16 determines that the image signal is an AV system image signal such as a natural image or a moving image, and uses the AV system precharge potential. It is decided to do (step S25).

  On the other hand, when the input image signal is a data system image signal (step S21; Yes), the controller 16 calculates the amount of fluctuation of the input image signal by the same method as in the second embodiment (step S22). Then, it is determined whether or not the fluctuation amount is larger than the predetermined amount (step S23). When the fluctuation amount is larger than the predetermined amount (step S23; No), the controller 16 determines that the data system image signal is a natural image or a moving image and determines to use the AV system precharge potential (step S25). . On the other hand, when the fluctuation amount is equal to or smaller than the predetermined amount (step S23; Yes), the controller 16 determines that the data system image signal is an image signal of an application on the PC and uses the data system precharge potential. Is determined (step S24).

  When the precharge potential to be used is determined, the controller 16 outputs the image signal and the potential instruction signal Sc indicating the determined precharge potential to the liquid crystal display device 20 (step S26). Thus, the determination of the precharge potential is completed. Thereafter, the liquid crystal display device 20 displays an image signal by performing precharge at a precharge potential corresponding to the potential instruction signal Sc.

  As described above, in the third embodiment, first, the presence / absence of a physical signal input to the connector terminal or the like is detected, and the AV system precharge potential is set for the AV system image signal. On the other hand, when the input image signal is a data system image signal, the fluctuation amount is calculated to determine whether the image is a natural image or a moving image, or an image of an application on a PC. Based on this, a precharge potential is set. Therefore, the precharge potential is immediately determined for the AV image signal, and an appropriate precharge potential can be determined for the data image signal according to the content thereof.

(Fourth embodiment)
In the first to third embodiments, the unit for determining the precharge potential is one frame. That is, any precharge potential determined according to the presence / absence of physical input of an image signal and / or the amount of fluctuation of the image signal is effective for one frame image. However, as described above, since precharging is performed in units of one line, the precharge potential can be changed for each line. Therefore, in the fourth embodiment, the precharge potential is determined for each line, and the precharge is performed using the determined precharge potential.

  FIG. 9 is an explanatory diagram of a precharge potential determination method in the fourth embodiment. FIG. 9 shows an example of a display screen for image signals output from a PC or the like. In this example, a part of the display screen on the monitor has a still image captured by a digital still camera or an application for reproducing MPEG or other moving images (generally called “Viewer”). In many cases, natural images or moving images are displayed in the display range 52 corresponding to the application.

  In this case, in the image of one frame, the line A in FIG. 9 does not include a natural image or a moving image, and therefore it is preferable to perform precharge at the data system precharge potential. On the other hand, since the line B partially includes a natural image / moving image, it is preferable to precharge the entire line B with an AV precharge potential in order to display the portion with high image quality. Therefore, in this embodiment, the content of the image signal is analyzed for each line, and which precharge potential is used is determined.

  The image display apparatus used in the present embodiment has a memory for storing at least one line of image signal in order to calculate the content of the image for each line of the input image signal, more specifically, the amount of fluctuation of the image. It is necessary to have. Therefore, the controller 16 has a configuration having the frame memory 18 as shown in FIG. 5 or a configuration having a line memory instead of the frame memory.

  The calculation of the fluctuation amount in the present embodiment can be basically performed in the same manner as in the second embodiment. That is, one or both of the spatial fluctuation amount between adjacent pixels shown in FIG. 6A and the temporal fluctuation amount between the previous and next frames shown in FIG. It is possible to determine the presence or absence of fluctuation for each line by calculating the fluctuation amount of the line by adding up the fluctuation amount of one line and comparing it with a predetermined reference amount.

  Then, the controller 16 determines that a line whose fluctuation amount is greater than or equal to a predetermined reference amount is an image signal such as a natural image or a moving image, and applies the AV precharge potential. That is, a potential instruction signal Sc indicating an AV precharge potential for the line is supplied to the liquid crystal display device 20. Further, the controller 16 determines that a line having a fluctuation amount smaller than a predetermined reference amount is an image signal for an application on the PC, and applies the data system precharge potential. That is, the potential instruction signal Sc indicating the data system precharge potential for the line is supplied to the liquid crystal display device 20. As a result, an appropriate precharge potential can be applied for each line of the image signal, so that high-quality image display can be executed more finely.

  The processing of the controller 16 in the fourth embodiment will be described with reference to the flowchart of FIG. First, the controller 16 receives the image signal Sa or Sd from the AV signal source 12 or the data signal source 14 (step S41).

  Next, the controller 16 calculates the fluctuation amount of the input image signal in units of lines by the above-described method (step S42), and determines whether or not the fluctuation amount is larger than a predetermined amount (step S43). If the fluctuation amount is larger than the predetermined amount (step S43; No), the controller 16 determines that the image signal of the line is a natural image or a moving image, and determines to use the AV precharge potential (step S45). . On the other hand, when the fluctuation amount is equal to or smaller than the predetermined amount (step S43; Yes), the controller 16 determines that the image signal of the line is an image signal of an application on the PC and uses the data system precharge potential. Is determined (step S44).

  Thus, when the precharge potential to be used is determined, the controller 16 outputs the image signal of the line and the potential instruction signal Sc indicating the determined precharge potential to the liquid crystal display device 20 (step S46). Thus, the determination of the precharge potential is completed. Thereafter, the liquid crystal display device 20 displays an image signal by performing precharge at a precharge potential corresponding to the potential instruction signal Sc.

[Electronics]
An electronic device configured using the above-described image display device includes a display information output source 1000, a display information processing circuit 1002, a display drive circuit 1004, a liquid crystal panel 1006, a clock generation circuit 1008, and a power supply circuit 1010 shown in FIG. Consists of. The display information output source 1000 includes a ROM, RAM, and other memories, a tuning circuit that tunes and outputs a television signal, and the like, and corresponds to the AV signal source 12 and the data signal source 14 described above. The display information output source 1000 outputs display information such as a video signal based on the clock from the clock generation circuit 1008.

  The display information processing circuit 1002 corresponds to the controller 16 described above, and processes and outputs display information based on the clock from the clock generation circuit 1008.

  The drive circuit 1004 includes the above-described V driver 1, H driver 4, precharge circuit 30, and the like, and drives the liquid crystal panel 1006 to display. The power supply circuit 1010 supplies power to each of the circuits described above.

  As an electronic apparatus having such a configuration, the liquid crystal projector shown in FIG. 12, the personal computer (PC) and engineering workstation (EWS), pager, or mobile phone shown in FIG. Examples include a type or 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 liquid crystal projector shown in FIG. 12 is a projection type projector that uses a transmissive liquid crystal panel as a light valve, and uses, for example, a prism synthesis type optical system. In FIG. 12, in the projector 1100, the projection light emitted from the lamp unit 1102 of the white light source is divided into three primary colors of R, G, and B by a plurality of mirrors 1106 and two dichroic mirrors 1108 inside the light guide 1104. The light modulated by the three active matrix liquid crystal panels 1110R, 1110G, and 1110B displaying images of the respective colors enters 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 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. 13 includes a main body 1204 provided with a keyboard 1202 and a liquid crystal display screen 1206.

  The present invention is not limited to the above embodiment, and various modifications can be made within the scope of the gist of the present invention. For example, the present invention is not limited to those applied to driving the above-described various liquid crystal panels, but can also be applied to an image display device using electroluminescence, a plasma display device, a CRT, or the like.

1 shows a schematic configuration of an image display device that is an embodiment of an electro-optical device of the invention. 1 shows a circuit configuration of a liquid crystal display device. 6 is a timing chart illustrating precharge of a liquid crystal display device. It is a flowchart of the precharge electric potential determination method by 1st Example. The schematic structure of the image display apparatus by 2nd Example is shown. It is explanatory drawing of the calculation method of the variation | change_quantity of the image signal in 2nd Example. It is a flowchart of the precharge electric potential determination method by 2nd Example. It is a flowchart of the precharge electric potential determination method by 3rd Example. It is explanatory drawing of the precharge electric potential determination method in 4th Example. It is a flowchart of the precharge electric potential determination method by 4th Example. 2 is a circuit configuration example of an electronic apparatus to which the electro-optical device of the invention is applied. 2 is an example of a liquid crystal projector to which the electro-optical device of the invention is applied. 6 is another example of an electronic apparatus to which the electro-optical device of the invention is applied.

Explanation of symbols

1 V driver, 2 gate line, 3 signal driver, 4 H driver, 5 signal line, 6 TFT, 7 liquid crystal pixel, 8 video potential line, 12 AV signal source, 14 data signal source, 16 controller, 20 liquid crystal display Device, 30 precharge circuit, 31 signal source, 32 control unit

Claims (9)

An input unit for receiving an image signal;
A precharge potential setting unit configured to set a precharge potential before applying the image signal based on the image signal;
A display unit that precharges the signal line with the precharge potential for each line of the image signal and displays an image corresponding to the image signal;
The input unit includes a first input unit to which an AV image signal is input, and a second input unit to which a data image signal is input,
The precharge potential setting unit sets the precharge potential to the first precharge potential when the image signal is input to the first input unit, and the image signal is input to the second input unit. An electro-optical device, wherein the precharge potential is set to a second precharge potential when being applied. A frame memory for storing an image input to the input unit;
A fluctuation amount calculation unit that calculates a fluctuation amount of the image signal stored in the frame memory,
The precharge potential setting unit sets the precharge potential to a first precharge potential when the variation amount exceeds a predetermined amount, and sets the precharge potential when the variation amount is equal to or less than the predetermined amount. The electro-optical device according to claim 1, wherein the pre-charge potential is set to 2. A memory capable of storing at least one line of the image signal input to the input unit;
A fluctuation amount calculation unit that calculates a fluctuation amount of the image signal for one line stored in the memory,
The precharge potential setting unit sets the precharge potential for the one line to a first precharge potential when the fluctuation amount exceeds a predetermined amount, and the first value when the fluctuation amount is equal to or less than the predetermined amount. 2. The electro-optical device according to claim 1, wherein the precharge potential for the line is set to a second precharge potential.   The fluctuation amount calculation unit calculates, for each pixel constituting the image signal, a fluctuation amount in a pixel unit with respect to a pixel adjacent to the pixel, and calculates the fluctuation amount based on the fluctuation amount in the pixel unit. The electro-optical device according to claim 2 or 3,   The fluctuation amount calculation unit calculates, for each pixel constituting the image signal, a fluctuation amount in a pixel unit with respect to a pixel corresponding to the pixel in the preceding and following frames, and calculates the fluctuation amount based on the fluctuation amount in the pixel unit. The electro-optical device according to claim 2, wherein the electro-optical device is calculated.   6. The electro-optical device according to claim 1, wherein the first precharge potential is a predetermined potential between a minimum potential and a maximum potential applied to the signal line during image display. apparatus.   The second precharge potential is closer to the minimum potential than an intermediate potential between a minimum potential and a maximum positive potential when a positive potential is applied to the signal line during the image display, and a negative potential is applied to the signal line. 7. The electro-optical device according to claim 1, wherein the potential is closer to the negative maximum potential than an intermediate potential between the minimum potential and the negative maximum potential.   8. A light source, comprising: an electro-optical device according to claim 1 that modulates light emitted from the light source; and a projection unit that projects light modulated by the electro-optical device. A projection display device characterized by the above. An image signal acquisition unit for acquiring the image signal from the outside;
An electronic apparatus comprising: the electro-optic device according to claim 1, wherein the image signal is displayed so as to be visible.

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