JP2009164987A - Electro-optical device, driving method thereof and projector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress generation of scroll noise without changing a drive frequency of a light source. <P>SOLUTION: An electro-optical device includes: a display panel which includes a plurality of pixels and in which an AC drive light source is irradiated with light; a memory which accumulates display data to be supplied and from which the relevant display data are read; a drive circuit to which display data read from the memory are supplied, and which scans and drives the display panel in such a way that a term in scanning is constituted of a scan term during which the plurality of pixels are driven in accordance with the relevant display data, and a fly-back term from the relevant scan term to start of the next scan; and a control circuit which controls the drive circuit so as to change the fly-back term within a predetermined time range at an interval of one or multiple times of scanning while fixing the scan term relating to drive due to the drive circuit, reads out display data accumulated in the memory synchronously with the relevant control, and supplies the read display data to the drive circuit. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a technique for improving display quality in an electro-optical device such as a projector.

There is a projector that generates a reduced image using a light valve such as a liquid crystal panel, and enlarges and projects the reduced image using an optical system. As a light source used in such a projector, a high-pressure discharge lamp or the like is used, and AC driving using a pulse or a triangular wave is performed in order to extend its life (see Patent Document 1). As a result, the amount of light of the light source increases immediately after the polarity is switched, and thus the light source flickers at a frequency twice the driving frequency. On the other hand, the liquid crystal panel is driven at a constant frequency, for example, 50 Hz in the PAL system and 100 Hz in the double speed driving system, and flickers according to the driving frequency.

Here, depending on the relationship between the driving frequency of the light source and the driving frequency of the liquid crystal panel, the flickering components may interfere with each other to generate a low-frequency component, resulting in flickering or scrolling bands (scrolling noise). Display quality may be deteriorated. In order to improve this, a technology is disclosed in which the driving frequency of the light source is set to a frequency at which scroll noise is difficult to see with respect to the driving frequency of the liquid crystal panel (see Patent Document 2). Further, a technique for changing the driving frequency of the light source is disclosed irrespective of driving of the liquid crystal panel so that the interference component does not have regularity (see Patent Document 3).
JP 2003-36992 A JP 2003-156798 A JP 2006-72196 A

Here, in the technique of Patent Document 2, depending on the driving frequency of the liquid crystal panel, the driving frequency of the light source for reducing scroll noise may be a frequency that adversely affects the lifetime. In the technique of Patent Document 3, depending on the mode of changing the driving frequency of the light source, scroll noise may occur if the changed driving pulse is similar for each video frame. In order to achieve this, it is necessary to frequently change the drive frequency, which increases the circuit load.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an electro-optical device, a driving method thereof, and a projector that can suppress the generation of scroll noise without changing the driving frequency of a light source. And

In order to solve the above-described problems, the present invention includes a display panel having a plurality of pixels and irradiating light to an AC-driven light source, a memory for storing supplied display data, and reading the display data. The display data read from the memory is supplied, the period in one scan is a scan period for driving the plurality of pixels in accordance with the display data, and the next scan is started after the scan period. A driving circuit that scans and drives the display panel, and a scanning period that is driven by the driving circuit is constant,
Alternatively, the drive circuit is controlled so that the blanking period is changed within a predetermined time range for each of a plurality of scans, and the display data stored in the memory is read out and supplied to the drive circuit in synchronization with the control. An electro-optical device is provided. According to this electro-optical device, the time of the blanking period can be changed for each frame, and the timing of blinking of the light source and the timing of starting scanning can be irregularly changed. Can be suppressed.

In another preferred embodiment, the control circuit is supplied with a synchronizing signal synchronized with display data supplied to the memory at a predetermined cycle, and supplies a timing signal for defining a start timing of the scanning period to the driving circuit. And adjusting the output timing of the timing signal with reference to the synchronization signal to control the drive circuit to change the blanking period, and in synchronization with the output of the timing signal, the memory It is also possible to read the display data stored in and supply it to the drive circuit. In this way, the blanking period can be changed by adjusting the output timing of the timing signal that defines the start timing of the scanning period.

In another preferable aspect, the memory can store the supplied display data up to a predetermined amount of data, and the control circuit sets the output timing of the timing signal after the timing when the synchronization signal is supplied. You may make it adjust within the period before the data amount of the display data accumulate | stored in memory reaches the said predetermined data amount. In this way, the adjustment range of the output timing of the timing signal can be defined by the data amount of the display data stored in the memory.

In another preferred aspect, the memory can store the supplied display data up to a predetermined amount of data, and the control circuit sets the output timing of the timing signal after the timing when the synchronization signal is supplied. Then, adjustment may be made within a period from the end of the scanning period related to the last output timing signal to before the amount of display data stored in the memory reaches the predetermined data amount. In this way, it is possible to prevent the scanning period related to the timing signal output immediately before from being included in the adjustment range of the output timing of the timing signal, and to prevent the timing signal from being output in the scanning period. it can.

Note that the present invention can be conceptualized not only as an electro-optical device, but also as a driving method of the electro-optical device and a projector having the electro-optical device.

  Embodiments of the present invention will be described below with reference to the drawings.

<Embodiment>
FIG. 1 is a plan view showing a configuration of a projector to which an electro-optical device according to an embodiment of the invention is applied. As shown in FIG. 1, a projector 2100 is provided with a lamp 2102 made of a white light source such as a halogen lamp driven by alternating current.

The projection light emitted from the lamp 2102 is composed of three mirrors 2106 disposed inside.
And two dichroic mirrors 2108, 3 for R (red), G (green), and B (blue).
The light is separated into primary colors and led to display panels 100R, 100G, and 100B corresponding to the primary colors. Note that the B-color light has an incident lens 2122, a relay lens 2123, and an exit lens 21 in order to prevent loss due to a long optical path compared to other R colors and G colors.
It is guided through a relay lens system 2121 comprising 24.

As will be described later, the display panels 100R, 100G, and 100B are each driven by display data corresponding to each color of R, G, and B, whereby a reduced image of each color is formed.
Reduced images formed by the display panels 100R, 100G, and 100B, that is, modulated light, enters the dichroic prism 2112 from three directions. In the dichroic prism 2112, the R and B light is refracted at 90 degrees,
G light goes straight. Therefore, after the images of the respective colors are combined, a color image is projected onto the screen 2120 by the projection lens 2114.

The display panels 100R, 100G, and 100B include a dichroic mirror 21.
Since the light corresponding to the primary colors of R, G, and B is incident by 08, there is no need to provide a color filter. In addition, the transmission images of the display panels 100R and 100B are projected after being reflected by the dichroic prism 2112, whereas the transmission images of the display panel 100G are projected as they are, so that the reduced images formed by the display panels 100R and 100B. And the reduced image formed by the display panel 100G are in a horizontally reversed relationship.

Next, an electro-optical device with control of the display panels 100R, 100G, and 100B will be described.

FIG. 2 is a diagram illustrating a configuration of the electro-optical device 10. As shown in FIG. 2, the electro-optical device 1
0 includes a control circuit 12, a memory 13, display panels 100R, 100G, and 100B.
Among these, the display panels 100R, 100G, and 100B are driven by the drive circuits 14R, 14G, and 14B, respectively, corresponding to the primary colors of R, G, and B, respectively.

FIG. 3 is a diagram showing the configuration of the display panel 100R and the drive circuit 14R. In FIG. 3, the display panel 100R is described as an example, but the display panels 100R, 100G, 1
The configurations of 00B are the same. Therefore, the following description of the display panel 100R is similarly applied to the display panels 100G and 100B.
, 100B and the reduced image formed by the display panel 100G are in a horizontally reversed relationship as described above.

As shown in FIG. 3, in the display panel 100R, 1080 scanning lines 112 are arranged in the horizontal direction (X
The data lines 114 of 1920 columns are extended in the vertical direction (Y direction).
Each of the plurality of pixels 110 forming the reduced image has these scanning lines 112 and data lines 114.
Are arranged corresponding to each intersection. As described above, in the present embodiment, the pixels 110 are arranged in a matrix of 1080 vertical rows by 1920 horizontal columns, but the present invention is not limited to this arrangement, and the intersection of a plurality of scanning lines and a plurality of data lines. Any arrangement may be used as long as it is provided corresponding to.

The pixel 110 includes a liquid crystal element and a switching transistor (hereinafter referred to as a TFT) that is turned on or off between one end of the liquid crystal element and the data line. this house,
The liquid crystal element is a kind of capacitance in which liquid crystal is sandwiched between one end and the other end maintained at a constant potential, and has a transmittance according to the effective value of the holding voltage. The TFT is turned on when the scanning line 112 is selected and connects one end of the liquid crystal element to the data line 114.

The drive circuit 14R is divided into a Y driver 142 that drives the scanning line 112 and an X driver 144 that drives the data line 114. Of these, the Y driver 142 is 1, 2, 3,.
Scan signals Y1, Y2, Y3,..., Y1080 are supplied to the scan line 112 in the 1080th row.
Specifically, in this embodiment, the Y driver 142 sets the scanning line 112 to 1, 2, 3,.
In the order of the 80th row, the scanning signal to the selected scanning line is set to a level for turning on the TFT, and the scanning signal to the other scanning line is set to a level for turning off the TFT. This is controlled by a scanning control signal Cry output from the control circuit 12 described later. On the other hand, the X driver 144 sends a data signal X to the data line 114 in the 1, 2, 3,.
1, X2, X3,..., X1920 are supplied. Specifically, the X driver 144 outputs a voltage data signal corresponding to the gradation value of the pixel (the gradation value specified by the display data Dr) to the pixel 110 located on the selected scanning line 112. The data line 114 is supplied.

As a result, the liquid crystal element in the pixel holds a voltage corresponding to the gradation and has a transmittance corresponding to the holding voltage. In addition, since a liquid crystal may be deteriorated when a direct current component is applied, the drive of the liquid crystal element is basically an alternating current drive. Therefore, X driver 14
4 supplies the voltage of the data signal supplied to the same liquid crystal element by alternately switching the voltage at the other end of the liquid crystal element between the high-order side (positive polarity) and the low-order side (negative polarity).

Here, in the present embodiment, a period from when the scanning line 112 is sequentially selected from the first row to the 1080th row by the drive circuit 14R and the voltage is supplied to all the pixels 110 is referred to as the scanning period Fa. That's it. A period after the scanning period until the next scanning is started, that is, until the next scanning line 112 is selected is referred to as a blanking period Fb. Thereby, the period in one scanning is comprised by the scanning period Fa and the blanking period Fb.

Returning to FIG. 2, the description will be continued. The control circuit 12 controls the operation of each part of the electro-optical device 10. Specifically, the control circuit 12 receives a synchronization signal Sync from a higher-level device (not shown).
The display data Vd supplied in synchronization with is temporarily transferred to and stored in the memory 13, and then the display data Vd is read out from the memory 13 in synchronization with scanning of the display panels 100R, 100G, and 100B. Of the display data Vd, the control circuit 12 supplies the R component display data Dr to the drive circuit 14R, the G component display data Dg to the drive circuit 14G, and the B component display data Db to the drive circuit 14B. . The memory 13 is a FIFO (First-I
n First-Out) type memory.

Further, the control circuit 12 drives the drive circuits 14R and 14G so as to be synchronized with these supply operations.
, 14B are controlled by scanning control signals Cry, Cgy, Cby, respectively. The scanning control signals Cry, Cgy, and Cby are configured by a timing signal DY that defines the start timing of the scanning period Fa and a clock signal CLY that defines the scanning period Fa, respectively. The control circuit 12 in the present embodiment adjusts the output timing of the timing signal DY for each scan while keeping the scan period constant so that the blanking period Fb is changed within a predetermined time range. 14R, 14G, and 14B are controlled. Note that the blanking period Fb may be changed for each of a plurality of scans.

The lighting circuit 20 outputs a driving signal Fla having a predetermined frequency, so that the lamp 210
2 is AC driven. Here, when the polarity of the drive signal Fla switches, the lamp 210
The shape of the pulse of the drive signal Fla is adjusted (not shown in the figure) for the purpose of extending the service life of 2.
As a result, the lamp 2102 has a large amount of light immediately after the polarity is switched.
Flashing is repeated at twice the frequency of the drive signal Fla.

Next, the display data Vd described above will be described. The display data Vd is supplied at a constant supply speed in synchronization with the synchronization signal Sync supplied at a constant cycle. The display data Vd is
As shown in FIG. 4, the period f of one frame includes an input scanning period fa and an input blanking period fb. In this input scanning period fa, the display data Vd is from 1 row 1 column to
1 row 1920 column, 2 rows 1 column to 2 rows 1920 columns, 3 rows 1 column to 3 rows 1920 columns, ..., 1080
The pixels are supplied in the order of pixels of row 1 column to 1080 row 1920 column. On the other hand, the input blanking period fb
In this case, nothing is supplied as the display data Vd. The same applies to the next frame, and this supply is repeated thereafter.

Next, the operation of the electro-optical device 10 according to the present embodiment will be described with reference to FIGS. 5 and 6 in comparison with the conventional technique in which the output timing of the timing signal DY is not adjusted for each scan.

FIG. 5 is a diagram showing the relationship between the operation of the lamp 2102 and the display panel 100 in the prior art. The horizontal axis in FIG. 5 indicates the progress of time. In the prior art, as shown in FIG. 5, the synchronization signal Sync is supplied in synchronization with the display data Vd. And the drive circuit 14R,
14G and 14B are supplied with the display data Dr, Dg and Db in synchronization with the timing signal DY, and the scanning period of the display panels 100R, 100G and 100B is the scanning period F.
It drives so that it may become a and the blanking period Fb. At this time, the clock signal CLY is controlled so that the input scanning period fa and the scanning period Fa related to the display data Vd are the same time.
Further, the timing signal DY is output from the synchronization signal Sy without adjusting its output timing.
Since it is output in the same cycle as nc, the input blanking period fb and the blanking period F related to the display data Vd
b is the same time. Q1, Q2,... Indicate display data corresponding to each scan.

Here, the timing at which the polarity of the drive signal Fla switches within the scanning period of each scan is such that the relative relationship within that scanning period is shifted by a certain amount for each scan, as indicated by the dashed arrows in the figure. To go. As a result, the timing at which the light amount of the lamp 2102 increases and the position of the scanning line selected at that timing are gradually shifted and recognized as scroll noise. At this time, the closer the relationship between the period of one scan and the period of an integral multiple of the period corresponding to half of the drive signal Fla is, the easier it is to be visually recognized because the relative relationship shifts slowly. The effect of scroll noise is increased.

FIG. 6 is a diagram illustrating a relationship between operations of the lamp 2102 and the display panel 100 of the electro-optical device 10 according to the present embodiment. The horizontal axis of FIG. 6 shows the progress of time. Q1, Q2,
... Shows display data corresponding to each scan as in FIG. As described above, the control circuit 12 adjusts the output timing of the timing signal DY with respect to the synchronization signal Sync for each scanning while keeping the scanning period constant, so that the blanking period Fb is within a predetermined time range. The drive circuits 14R, 14G, and 14B are controlled so as to be changed at The memory 13 can store a predetermined amount of data, and in this embodiment, the amount of data that can be stored is the amount of data corresponding to the time of the input blanking period fb related to the display data Vd. To do.

The control circuit 12 adjusts the output timing of the timing signal DY. That is, it is not output in the same cycle as that of the supplied synchronization signal Sync, but in a period after the timing when the synchronization signal Sync is supplied and before the time of the input blanking period fb related to the display data Vd. Output at a randomly selected timing.

The supplied display data Vd is accumulated in the memory 13 until the timing signal DY is output. At this time, the display data Dr, Dg, and Db are not read out.
As shown in the data amount in the memory of FIG. 6, the data amount of the display data Vd stored in the memory 13 increases. Here, as described above, the memory 13 can accumulate a data amount corresponding to the time of the input blanking period fb. Therefore, the memory 13 stores the synchronization signal Sy
The timing signal DY is output by the control circuit 12 from the start of accumulation of the display data Vd together with the supply of nc to before the accumulated display data Vd reaches the maximum accumulation amount (corresponding to max in the drawing). Therefore, the accumulated display data Vd is displayed as display data Dr, D
It is read as g and Db.

As will be described later, in the period from the output of the timing signal DY to the end of the input scanning period fa of the display data Vd, that is, the period in which the scanning period Fa and the input scanning period fa overlap each other, as will be described later. Since the display data Vd supply speed to the memory and the display data Dr, Dg, Db read from the memory 13 are controlled to be the same, the amount of data stored in the memory 13 does not vary. In the input blanking period fb related to the display data Vd, the display data Vd is not supplied to the memory 13 but only read out, that is, in the period in which the input blanking period fb and the scanning period Fa overlap. , Memory 13
The amount of data stored in is reduced.

The drive circuits 14R, 14G, and 14B are supplied with display data Dr, Dg, and Db in synchronization with the timing signal DY output in this manner, and display panels 100R, 100G, and 1B are supplied.
One scanning period at 00B is a scanning period Fa and a blanking period Fb (Fb1, Fb2,.
・ ・) Drive to become. At this time, the control circuit 12 controls the clock signal CLY so that the input scanning period fa and the scanning period Fa related to the display data Vd are the same time.
That is, the supply speed of the display data Vd to the memory 13 and the reading speed of the display data Dr, Dg, Db are the same. On the other hand, since the output timing of the timing signal DY is adjusted, the time from the start of each scanning period Fa to the start of the next scanning, that is, the blanking period Fb is Fb1, Fb2,.・ Changed.

Here, the timing at which the polarity of the drive signal Fla switches within the scanning period Fa of each scan is irregular for each scan, as indicated by the dashed arrows in the figure, in the relative relationship within the scanning period Fa. To change. As a result, even when the light amount of the lamp 2102 increases and the position of the scanning line selected at that timing changes, this shift mode is irregularly changed, so that it is not recognized as scroll noise.

Thus, in the electro-optical device 10 according to the present embodiment, the output timing of the timing signal DY is adjusted for each scan to change the blanking period Fb, so that the scroll noise is not changed without changing the driving frequency of the light source. Can be suppressed. Therefore, even if the lamp 2102 using the drive signal Fla of any drive frequency is used, the generation of scroll noise can be suppressed.

As mentioned above, although embodiment of this invention was described, this invention can be implemented in various aspects as follows.

<Modification 1>
In the above-described embodiment, the control circuit 12 changes the output period of the timing signal DY from the timing at which the synchronization signal Sync is supplied in order to change the return period Fb for each scan. In the period before the time of the period fb elapses, the output is performed at a randomly selected timing, but it may not be random.
For example, the control circuit 12 defines a candidate timing as an adjustment time from the timing at which the synchronization signal Sync is supplied to the output timing of the timing signal DY, and a plurality of adjustment times are stored, and a candidate is selected for each scan. The timing signal DY may be output corresponding to the adjustment time selected randomly or by a predetermined algorithm.

Note that the predetermined algorithm may be any algorithm as long as it defines the order of adjustment times to be selected for each scan. The candidate timing may be defined not as the adjustment time but as the amount of data stored in the memory 13. In this case, after the storage of display data in the memory 13 is started, the timing signal DY may be output when the specified data amount is reached. Then, the specified data amount may be changed for each scan.

<Modification 2>
In the embodiment described above, the control circuit 12 performs control so that the adjustment of the output timing of the timing signal DY is performed in a period from the timing at which the synchronization signal Sync is supplied until the time of the input retrace period fb elapses. Thus, the control circuit 12 controls to change the blanking period Fb within a predetermined time range for each scanning while keeping the scanning period Fa constant. However, the control circuit 12 may be controlled in any way. For example, if the memory 13 can store a larger amount of data, the amount of data in the memory 13 becomes the maximum data amount that can be stored even at the timing after the time of the input blanking period fb. In this period, the timing signal DY can be output. That is, the control circuit 12 determines the output timing of the timing signal DY.
Display data Vd accumulated in the memory 13 after the timing when the synchronization signal Sync is supplied.
Adjust within the period until the amount of data reaches the maximum storage amount.

Here, when the timing signal DY is output at a timing after the time of the input blanking period fb has elapsed from the timing at which the synchronization signal Sync is supplied, the timing signal DY
The next synchronization signal Sync is supplied before the end of the scanning period Fa. In this case,
The control circuit 12 displays the output timing of the timing signal DY after the timing when the synchronization signal Sync is supplied and after the end of the scanning period Fa related to the last output timing signal DY. Adjustment may be made within a period before the data amount of the data Vd reaches the maximum storage amount.

<Modification 3>
In the embodiment described above, the electro-optical device 10 includes the display panels 100R, 100G,
Although 100B uses a transmissive liquid crystal panel, it may be a reflective type. Also,
In the embodiment described above, the case where the electro-optical device 10 is applied to a projector has been described. However, the electro-optical device 10 may be used for a direct-view display having a backlight which is an AC-driven light source.

It is a top view which shows the structure of the projector which concerns on embodiment of this invention. 1 is a block diagram illustrating a configuration of an electro-optical device according to an embodiment of the invention. FIG. It is a figure which shows the structure of the display panel which concerns on embodiment of this invention. It is a block diagram which shows the display data which concern on embodiment of this invention. It is a figure which shows operation | movement of the conventional electro-optical apparatus. FIG. 6 is a diagram illustrating an operation of the electro-optical device according to the embodiment of the invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Electro-optical device, 12 ... Control circuit, 13 ... Memory, 14R, 14G, 14B ... Drive circuit, 20 ... Lighting circuit, 100R, 100G, 100B ... Display panel, 110 ... Pixel, 21
00 ... Projector

Claims (6)

A display panel having a plurality of pixels and irradiating light to a light source driven by alternating current;
A memory for accumulating display data to be supplied and reading the display data;
Display data read from the memory is supplied, and a period in one scan is a scan period for driving the plurality of pixels according to the display data, and after the scan period until the next scan is started A drive circuit that scans and drives the display panel so as to be configured by a blanking period of:
The drive circuit is controlled so as to change the blanking period within a predetermined time range for each one or a plurality of scans while keeping the scan period related to driving by the drive circuit constant, and in synchronization with the control, And a control circuit that reads display data stored in a memory and supplies the display data to the driving circuit. The control circuit includes:
A synchronization signal synchronized with the display data supplied to the memory is supplied at a predetermined cycle,
Outputting a timing signal defining the start timing of the scanning period to the drive circuit;
Control the drive circuit to change the blanking period by adjusting the output timing of the timing signal with reference to the synchronization signal,
2. The electro-optical device according to claim 1, wherein display data stored in the memory is read and supplied to the driving circuit in synchronization with an output of the timing signal. The memory can store the supplied display data up to a predetermined amount of data,
The control circuit adjusts the output timing of the timing signal within a period after the timing when the synchronization signal is supplied and before the amount of display data stored in the memory reaches the predetermined data amount. The electro-optical device according to claim 2. The memory can store the supplied display data up to a predetermined amount of data,
The control circuit sets the output timing of the timing signal to the display data stored in the memory after the timing when the synchronization signal is supplied and after the end of the scanning period related to the last output timing signal. The electro-optical device according to claim 2, wherein the amount is adjusted within a period before the amount reaches the predetermined data amount. An electro-optical device according to any one of claims 1 to 4,
A projector comprising: a projection lens that projects modulated light obtained by irradiating the display panel with light emitted from the light source. A driving method of an electro-optical device including a display panel having a plurality of pixels and irradiated with light to a light source that is AC driven,
After storing the supplied display data in the memory, the display data is read at a predetermined timing,
A period in one scan is configured by a scan period for driving the plurality of pixels in accordance with display data read from the memory, and a blanking period from the start of the scan period to the start of the next scan. And scanning and driving the display panel,
Controlling the driving of the display panel so as to change the blanking period within a predetermined time range for each of one or a plurality of scans while keeping the scanning period for driving the display panel constant,
The timing for reading the display data stored in the memory is synchronized with the drive control of the display panel.

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