JP2013041158A - Projector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent burn-in of a liquid crystal panel time-division driven in a two-plate type projector.SOLUTION: A projector 1 comprises: an R color light source 11 for emitting light of R color; a B color light source 13 for emitting light of B color; a G color light source 21 for emitting light of G color; a first liquid crystal panel 100 to which the light of the R color light source 11 and the light of the B color light source 13 are made incident and an image signal Vr of R color and an image signal Vb of B color are supplied; and a second liquid crystal panel 200 to which the light of the G color light source 21 is made incident and an image signal Vg of G color is supplied. In a second unit period of odd-numbered frames and a first unit period of even-numbered frames, a polarity of a data signal is reversed. In a second unit period of the even-numbered frames and a first unit period of the odd-numbered frames, the polarity of the data signal is reversed.

Description

  The present invention relates to a projector provided with two light valves.

In recent years, projectors have become widespread as projection display devices that display a large screen on a screen. Some projectors include light sources and liquid crystal panels corresponding to R, B, and G colors, respectively. Furthermore, a two-plate projector is known that includes a liquid crystal panel corresponding to a G color light source, a R color light source and a B color light source that emit light in a time-sharing manner, and a liquid crystal panel corresponding to these. reference).
The two-plate projector has an advantage that the number of liquid crystal panels can be reduced.

JP-A-2-123344

By the way, the transmittance of each pixel in the liquid crystal panel changes depending on the voltage applied to the liquid crystal, but when a DC voltage is applied to the liquid crystal, so-called burn-in occurs, and the original image remains even if the image is rewritten. There is. For this reason, the driving of the liquid crystal panel is generally AC driving in which the voltage applied to the liquid crystal is inverted at a predetermined period.
The above-mentioned prior art document shows that an R color image and a B color image are written to the liquid crystal panel in a time-division manner in one frame period. How to realize AC driving. Is not disclosed. On the other hand, in a liquid crystal television or the like, double speed driving is known in which an image is written twice in one frame in order to reduce an afterimage due to motion. In this case, the polarity of the voltage written in the liquid crystal panel in the first half of one frame and the voltage written in the liquid crystal panel in the second half may be reversed.
However, when an R color image and a B color image are written to the liquid crystal panel in a time-division manner during a period of one frame, the R color image and the B color image have no correlation. Even if the technology is applied, AC drive cannot be realized, and there is a problem that burn-in occurs.
The present invention has been made in view of the above-described circumstances, and an object of the present invention is to reduce afterimages due to image sticking in a two-plate projector.

  In order to solve this problem, a projector according to the present invention includes a first color light source that emits light of a first color, a second color light source that emits light of a second color, and a third color light. A third color light source that emits light, a plurality of scanning lines, a plurality of data lines, and a data signal provided corresponding to the intersection of the scanning lines and the data lines, and supplied via the data lines A plurality of pixels whose transmittance is controlled in accordance with a voltage between a pixel electrode and a common electrode to which light is supplied, and light from the light source of the first color and light from the light source of the second color are An incident first liquid crystal panel; first driving means for driving the first liquid crystal panel; a second liquid crystal panel in which light from the third color light source is incident on a plurality of pixels whose transmittance is controlled; Second driving means for driving the second liquid crystal panel; light transmitted through the first liquid crystal panel; and the second liquid crystal. Optical means for combining and outputting the light transmitted through the light channel, light emission control means for controlling light emission of the light source of the first color and the light source of the second color, and one frame for displaying an image of one screen, The first liquid crystal panel is divided into a first unit period and a second unit period, which are units for driving the first liquid crystal panel in a time-sharing manner, and the brightness of each pixel of the first color is shown in part or all of the first unit period. An image signal of one color is supplied to the first driving unit, and an image signal of the second color indicating the luminance of each pixel of the second color is supplied to the first driving unit during part or all of the second unit period. Image control means for supplying, the first drive means for outputting the data signal to the plurality of data lines based on the image signal of the first color or the image signal of the second color, The first unit period and the first unit period of an even frame; Reverses the polarity of the data signal with reference to the potential of the common electrode, and the polarity of the data signal with respect to the potential of the common electrode in the second unit period of the odd frame and the second unit period of the even frame. Is inverted.

  According to the present invention, one frame is divided into a first unit period and a second unit period, and the first liquid crystal panel displays an image of the first color in the first unit period and the second color in the second unit period. Time-division driving for displaying the image is performed. In this case, the first color data signal is written to each pixel of the first liquid crystal panel in the first unit period. In this writing, the polarity of the data signal is determined based on the potential of the common electrode in the odd and even frames. Inverted. On the other hand, in the second unit period, the data signal of the second color is written to each pixel of the first liquid crystal panel. In this writing, the polarity of the data signal is inverted with reference to the potential of the common electrode in the odd and even frames. The That is, when writing data signals of the first color and the second color in a time-sharing manner, the polarity of the data signal of the same color is reversed, so that the liquid crystal can be driven with alternating current and the burn-in of the first liquid crystal panel is prevented. can do.

  In the projector described above, the light emission control unit may be configured such that, in the first half of the first unit period, the light source of the first color is written until the writing of the data signal of the first color of one screen to the first liquid crystal panel is completed. And the second color light source is controlled to emit no light, and in the second half of the first unit period after the writing is finished, the first color light source emits light and the second color light source emits light. In the first half of the second unit period, the light source of the first color and the light source of the first color are written until the writing of the data signal of the second color of one screen to the first liquid crystal panel is completed in the first half of the second unit period. The second color light source is controlled so as not to emit light, and the second color light source emits light and the second color light source does not emit light in the second half of the second unit period after the writing is completed. Control to be Preferred.

  According to the present invention, since the color displayed on the first liquid crystal panel is different between the first unit period of the current frame and the second unit period of the immediately preceding frame, the pixel is held in the first half of the first unit period. A data signal having a color different from that of the existing data signal is written. In such a period, control is performed so that both the first color light source and the second color light source emit no light, and thus color mixing can be prevented.

  Next, a projector according to the present invention includes a first color light source that emits light of a first color, a second color light source that emits light of a second color, and a third light source that emits light of a third color. Color light source, a plurality of scanning lines, a plurality of data lines, and pixels provided corresponding to the intersections of the scanning lines and the data lines, and supplied with data signals supplied via the data lines A first liquid crystal comprising a plurality of pixels whose transmittance is controlled according to a voltage between the electrode and the common electrode, and the light from the light source of the first color and the light from the light source of the second color are incident thereon A panel, first driving means for driving the first liquid crystal panel, a second liquid crystal panel in which light of the third color light source is incident on a plurality of pixels whose transmittance is controlled, and the second liquid crystal panel. Second driving means for driving; light transmitted through the first liquid crystal panel; and light transmitted through the second liquid crystal panel; The optical means for combining and outputting, the light emission control means for controlling the light emission of the light source of the first color and the light source of the second color, and one frame for displaying an image of one screen are connected to the first liquid crystal panel. A first color image that is divided into a first unit period and a second unit period, which are units driven by division, and indicates the luminance of each pixel of the first color in part or all of the first unit period of an odd frame. A signal is supplied to the first driving unit, and an image signal of the second color indicating the luminance of each pixel of the second color is supplied to the first driving unit in part or all of the second unit period of the odd frame. Then, the first color image signal is supplied to the first driving means in a part or all of the first unit period of the even frame, and the first unit is supplied in part or all of the second unit period of the even frame. Supply color image signal to the first drive means Image control means, wherein the first driving means outputs the data signal to the plurality of data lines based on the first color image signal or the second color image signal, In the second unit period and the first unit period of the even frame, the polarity of the data signal is inverted with reference to the potential of the common electrode, and the second unit period of the even frame and the first unit period of the odd frame. Then, the polarity of the data signal is inverted with reference to the potential of the common electrode.

  According to this invention, one frame is divided into a first unit period and a second unit period, a second color is assigned to the second unit period of the odd frame and the first unit period of the even frame, and the second unit of the even frame. The first color is assigned to the period and the first unit period of the odd frame, and the first liquid crystal panel is driven in a time division manner. In this case, in the second unit period of the odd frame and the first unit period of the even frame, the second color data signal is written to each pixel of the first liquid crystal panel. The polarity of the data signal is inverted with reference to the potential of the common electrode. On the other hand, in the second unit period of the even frame and the first unit period of the odd frame, the data signal of the first color is written to each pixel of the first liquid crystal panel. In this writing, the common electrode is used in the odd frame and the even frame. The polarity of the data signal is inverted with reference to the potential of. That is, when writing data signals of the first color and the second color in a time-sharing manner, the polarity of the data signal of the same color is reversed, so that the liquid crystal can be driven with alternating current and the burn-in of the first liquid crystal panel is prevented. can do.

  In the projector described above, the light emission control unit may perform the first emission until writing of the second color data signal of one screen to the first liquid crystal panel is completed in the first half of the second unit period of odd frames. The color light source and the light source of the second color are controlled so as not to emit light, and from the latter half of the second unit period after the writing is completed until the first unit period of the even frame is completed. Control is performed so that the light source of the second color emits light and the light source of the first color does not emit light. In the first half of the second unit period of the even-numbered frame, the first liquid crystal panel has one screen on the first liquid crystal panel. Until the writing of the color data signal is completed, the light source of the first color and the light source of the second color are controlled to emit no light, and from the second half of the second unit period after the writing is finished. The odd number Until the first unit period of over arm ends, it is preferable that the first color light source emits light and the second color light source is controlled to be no light.

  According to the present invention, in the first half of the second unit period of the odd-numbered frame, the light source of the second color emits during the period in which the first unit period of the even-numbered frame ends after the writing of the second color data signal is completed. In the first half of the second unit period of the even frame, the light source of the first color emits light during the period of the end of the first unit period of the odd frame after the writing of the first color data signal is completed. Control to do. That is, since the data signal of the same color is written to each pixel in successive unit periods, the period during which the first color light source and the second color light source do not emit light can be shortened in order to avoid color mixing. For this reason, the light emission period of the light source of the first color and the light source of the second color can be lengthened, and the luminance of the image displayed by the projector can be improved.

  The projector control method according to the present invention includes a first color light source that emits light of a first color, a second color light source that emits light of a second color, and a third light source that emits light of a third color. Color light source, a plurality of scanning lines, a plurality of data lines, and pixels provided corresponding to the intersections of the scanning lines and the data lines, and supplied with data signals supplied via the data lines A first liquid crystal comprising a plurality of pixels whose transmittance is controlled according to a voltage between the electrode and the common electrode, and the light from the light source of the first color and the light from the light source of the second color are incident thereon A panel, a second liquid crystal panel in which light from the light source of the third color is incident on a plurality of pixels whose transmittance is controlled, light transmitted through the first liquid crystal panel, and light transmitted through the second liquid crystal panel For controlling a projector having optical means for combining and outputting One frame for displaying the first liquid crystal panel is divided into a first unit period and a second unit period, which are units for driving the first liquid crystal panel in a time-sharing manner, and the first color of the first color is displayed in part or all of the first unit period. The data signal of the first color indicating the luminance of each pixel is written to each pixel of the first liquid crystal panel, and the second color indicating the luminance of each pixel of the second color in part or all of the second unit period. The data signal is written to each pixel of the first liquid crystal panel, and the polarity of the data signal is inverted with respect to the potential of the common electrode in the first unit period of the odd frame and the first unit period of the even frame. In the second unit period of the odd frame and the second unit period of the even frame, the polarity of the data signal is inverted with reference to the potential of the common electrode.

  According to the present invention, the data signal of the first color is written to each pixel of the first liquid crystal panel in the first unit period. In this writing, the data signal of the data signal is referenced with respect to the potential of the common electrode in the odd and even frames. The polarity is reversed. On the other hand, in the second unit period, the data signal of the second color is written to each pixel of the first liquid crystal panel. In this writing, the polarity of the data signal is inverted with reference to the potential of the common electrode in the odd and even frames. The That is, when writing data signals of the first color and the second color in a time-sharing manner, the polarity of the data signal of the same color is reversed, so that the liquid crystal can be driven with alternating current and the burn-in of the first liquid crystal panel is prevented. can do.

  Next, the projector control method according to the present invention emits the first color light source that emits the first color light, the second color light source that emits the second color light, and the third color light. A third color light source, a plurality of scanning lines, a plurality of data lines, and a data signal supplied via the data lines provided corresponding to the intersection of the scanning lines and the data lines. A plurality of pixels whose transmittance is controlled in accordance with a voltage between the pixel electrode and the common electrode, and light from the light source of the first color and light from the light source of the second color are incident A first liquid crystal panel; a second liquid crystal panel in which light from the third color light source is incident on a plurality of pixels whose transmittance is controlled; and light transmitted through the first liquid crystal panel and transmitted through the second liquid crystal panel. For controlling a projector having optical means for combining and outputting the combined light. One frame for displaying the image is divided into a first unit period and a second unit period, which are units for driving the first liquid crystal panel in a time-sharing manner, and the first unit period is partially or entirely included in the first unit period. The data signal of the first color indicating the luminance of each pixel of the color is written into each pixel of the first liquid crystal panel, and the first color signal indicating the luminance of each pixel of the second color in part or all of the second unit period. The data signals of two colors are written to the respective pixels of the first liquid crystal panel, and the polarity of the data signal is based on the potential of the common electrode in the first unit period of the odd frame and the first unit period of the even frame. The polarity of the data signal is inverted with respect to the potential of the common electrode in the second unit period of the odd frame and the second unit period of the even frame.

  According to the present invention, in the second unit period of the odd frame and the first unit period of the even frame, the data signal of the second color is written to each pixel of the first liquid crystal panel. In the frame, the polarity of the data signal is inverted with reference to the potential of the common electrode. On the other hand, in the second unit period of the even frame and the first unit period of the odd frame, the data signal of the first color is written to each pixel of the first liquid crystal panel. In this writing, the common electrode is used in the odd frame and the even frame. The polarity of the data signal is inverted with reference to the potential of. That is, when writing data signals of the first color and the second color in a time-sharing manner, the polarity of the data signal of the same color is reversed, so that the liquid crystal can be driven with alternating current and the burn-in of the first liquid crystal panel is prevented. can do.

It is a block diagram which shows the mechanical structure of the projector which concerns on embodiment. It is a block diagram which shows the electric structure of the projector which concerns on embodiment. It is a block diagram which shows the electrical structure of a 1st liquid crystal panel. It is a circuit diagram which shows the structure of a pixel. It is a flowchart which shows operation | movement of the projector which concerns on 1st Embodiment. It is a flowchart which shows operation | movement of the projector which concerns on 2nd Embodiment. It is a flowchart which shows operation | movement of the projector which concerns on 3rd Embodiment.

Embodiments of the present invention will be described below with reference to the drawings.
<1. First Embodiment>
<1-1: Projector configuration>
FIG. 1 is a block diagram showing a mechanical configuration of the projector according to the first embodiment. As shown in this figure, the projector 1 includes a first liquid crystal panel 100 on which R color (red) light and B color (blue) light are incident in a time division manner, and a second liquid crystal on which G color (green) light is incident. The optical system 30 which synthesize | combines the light which permeate | transmitted the panel 200 and the 1st liquid crystal panel 100, and the light which permeate | transmitted the 2nd liquid crystal panel 200, and irradiates the screen S is provided.

  The R color light source 11 emits R color light. The field lens 12 converts the light from the R color light source 11 into parallel light and guides it to the dichroic prism 15. On the other hand, the B-color light source 13 emits B-color light. The field lens 14 converts the light from the B color light source 13 into parallel light and guides it to the dichroic prism 15. The R color light source 11 and the B color light source 13 can be configured by LEDs, for example. The dichroic prism 15 irradiates the first liquid crystal panel 100 with light obtained by transmitting R light and reflecting B light. In the first liquid crystal panel 100, the light modulation is controlled in synchronization with the switching between the R color light and the B color light so that the transmittance according to the luminance of the R color and the luminance of the B color is obtained.

  The G light source 21 emits G light. The field lens 22 converts the light from the G color light source 21 into parallel light and irradiates the second liquid crystal panel 200. The light modulation of the second liquid crystal panel 200 is controlled so as to have a transmittance corresponding to the G color luminance.

  In the optical system 30, the light transmitted through the first liquid crystal panel 100 and the light transmitted through the second liquid crystal panel 200 are incident on the dichroic prism 31, and the combined light is output to the projection lens 32. The projection lens 32 projects the combined light onto the screen S.

  FIG. 2 is a block diagram illustrating an electrical configuration of the projector according to the embodiment. The projector 1 is supplied with image data Dr indicating the luminance of the R color, image data Db indicating the luminance of the B color, and image data Dg indicating the luminance of the G color from the outside. The image processing circuit 40 performs image processing such as gamma correction on the image data Dr, Db, Dg and outputs the processed image data to the control circuit 50.

  The control circuit 50 functions as a control center that controls the entire projector 1. Specifically, the control circuit 50 supplies a light source control signal LC for controlling each light source to the light source driving circuit 60, and outputs a control signal and an image signal to the first liquid crystal panel 100 and the second liquid crystal panel 200. Supply.

  The first image signal V1 supplied to the first liquid crystal panel 100 is a signal obtained by time-division multiplexing the R color image signal Vr and the B color image signal Vb, and is supplied to the second liquid crystal panel 200. The two image signal V2 is a G color image signal Vg. In order to prevent burn-in of the first liquid crystal panel 100 and the second liquid crystal panel 200, the control circuit 50 applies the voltages of the image signals Vr, Vb, and Vg to the common potential LCcom supplied to the common electrode 108 described later. As a reference (see FIG. 4), inversion is performed according to a predetermined rule. When the high potential is positive and the low potential is negative with respect to the common potential LCcom, the control circuit 50 uses the first polarity signal Z1 and the second polarity signal Z1 that specify the polarity of the first image signal V1 (Vr, Vb). A second polarity signal Z2 for designating the polarity of the image signal V2 (Vg) is internally generated (see FIG. 5), and the polarity of the image signal is controlled based on this.

  The scanning line driving circuit and the data line driving circuit formed on the first liquid crystal panel 100 function as a first driving circuit that drives the first liquid crystal panel 100, and the scanning line driving circuit formed on the second liquid crystal panel 200 The data line driving circuit functions as a second driving circuit. The first drive circuit and the second drive circuit may be provided outside the first liquid crystal panel 100 and the second liquid crystal panel 200.

  The light source drive circuit 60 generates light emission control signals Lr, Lb, and Lg for controlling the R color light source 11, the B color light source 13, and the G color light source 21 based on the light source control signal LC. The R color light source 11, the B color light source 13, and the G color light source 21 emit light at a luminance corresponding to the level of each light emission control signal Lb, Lr, and Lg. In this example, the light emission control signals Lb, Lr, and Lg are binary values of a high level and a low level, each light source emits light (lights) during a period when the light emission control signal is high level, and a period when the light emission control signal is low level. Each light source does not emit light (turns off).

FIG. 3 shows an electrical configuration of the first liquid crystal panel 100. The second liquid crystal panel 200 is similarly configured. In the first liquid crystal panel 100, a plurality of scanning lines 112 are extended in the row direction (X direction), while a plurality of data lines 114 are extended in the column direction (Y direction) in the drawing. The pixels 110 are provided so as to correspond to the intersections of the scanning lines 112 and the data lines 114, respectively.
In the present embodiment, the number of scanning lines 112 (number of rows) is n, and the number of data lines 114 (number of columns) is m. The scanning line driving circuit 120 sequentially selects the n scanning lines 112 and supplies the scanning signals Y1 to Yn to the scanning lines 112. The data line driving circuit 130 converts the supplied first image signal V1 into line-sequential data signals Vd1 to Vdm and supplies them to the data line 114.

Next, the pixel 110 will be described. As shown in FIG. 3, in the pixel 110, the source of the n-channel TFT 116 is connected to the data line 114, the drain is connected to the pixel electrode 118, and the gate is connected to the scanning line 112. Yes. In addition, the common electrode 108 is provided in common to all the pixels so as to face the pixel electrode 118 and is maintained at a constant common potential LCcom. A liquid crystal layer 105 is sandwiched between the pixel electrode 118 and the common electrode 108. Therefore, a liquid crystal capacitor composed of the pixel electrode 118, the common electrode 108, and the liquid crystal layer 105 is formed for each pixel.
In addition, a storage capacitor 109 is formed for each pixel in order to make it difficult for charge to leak in the liquid crystal capacitor. One end of the storage capacitor 109 is connected to the pixel electrode 118, and the other end is commonly grounded across all pixels. Note that the TFT 116 in the pixel 110 is formed by a manufacturing process common to the constituent elements of the scanning line driving circuit 120 and the data line driving circuit 130.
Further, in order to AC drive the voltage applied to the liquid crystal layer 105, the data signals Vd1 to Vdm are supplied so that the polarity of the voltage of the pixel electrode 118 is inverted at a predetermined cycle with the common potential LCcom as a reference.

<1-2: Projector operation>
Next, the operation of the projector will be described. One frame for displaying an image of one screen is divided into a plurality of unit periods which are units for driving the first liquid crystal panel 100 by time division. In the present embodiment, one frame is divided into a first unit period Ta and a second unit period Tb.
The first unit period Ta includes a first period T1 and a second period T2, and the second unit period Tb includes a third period T3 and a fourth period T4.
The control circuit 50 controls the first liquid crystal panel 100 to display the B color in the first unit period Ta and the R color in the second unit period Tb as shown in FIG.

  In each frame, in the first period T1 of the first unit period Ta, the scanning signals Y1 to Yn are sequentially activated, and the B-color image signal Vb is converted into line-sequential data signals Vd1 to Vdm. Is written in each of the pixels 110. The written image signal Vb is held in the second period T2. Next, in the third period T3 of the second unit period Tb, the scanning signals Y1 to Yn are sequentially activated, and the R color image signal Vr is converted into line-sequential data signals Vd1 to Vdm. It is written in each pixel 110. The written image signal Vr is held in the fourth period T4.

  Here, the first polarity signal Z1 becomes a high level designating positive polarity in odd frames and a low level designating negative polarity in even frames. Therefore, the polarity of the B-color image signal Vb1 written in the first unit period Ta of the first frame F1 (odd number frame) is positive (+), and is written in the first unit period Ta of the second frame (even number frame). The polarity of the B-color image signal Vb2 is negative (−). The polarity of the R-color image signal Vr1 written in the second unit period Tb of the first frame F1 (odd frame) is positive (+), and is written in the second unit period Tb of the second frame (even frame). The polarity of the R color image signal Vr2 is negative (−).

  Therefore, the voltage applied to the liquid crystal layer 105 is canceled out by the positive B color image signal Vb1 and the negative B color image signal Vb2, and the positive R color image signal Vr1 and the negative R signal. It cancels out with the color image signal Vr2. Therefore, an alternating voltage is applied to the liquid crystal layer 105, and image sticking can be prevented.

Next, the light emission control signal Lb becomes high level with a delay of time ΔT from the start of the second period T2, and becomes low level at the end of the third period T3. In addition, the light emission control signal Lr becomes high level with a delay of time ΔT from the start of the third period T3, and becomes low level at the end of the fourth period T4.
Therefore, in the first half of the first unit period Ta (first period T1), until the writing of the B-color data signal Vd for one screen to the first liquid crystal panel 100 is completed, the R-color light source 11 and the B-color light source 13 In the latter half of the first unit period Ta after the writing is finished, the B color light source 13 is controlled to emit light and the R color light source 11 is controlled to emit no light.
In addition, in the first half of the second unit period Tb (third period T3), the R color light source 11 and the B color light source 13 remain until the writing of the R color data signal Vd for one screen to the first liquid crystal panel 100 is completed. In the second half of the second unit period Tb after the writing is finished, the R color light source 11 is controlled to emit light and the B color light source 13 is controlled to emit no light.

  Incidentally, at the end of the first period T1, the writing of the B-color image signal Vb has been completed. The reason why the B-color light source 13 is delayed by the time ΔT from the end of the first period T1 is because the response characteristic of the liquid crystal is taken into consideration. Although the transmittance of the liquid crystal changes depending on the applied voltage, the transmittance does not change immediately even when the applied voltage changes, but the transmittance of the liquid crystal changes after the change of the applied voltage. In the first period T1, the first liquid crystal panel 100 rewrites the red image written in the fourth period T4 of the immediately preceding frame into a blue image. For this reason, at the end of the first period T1, the change in transmittance does not follow the change in the applied voltage for the pixels 110 in the vicinity of the nth row. For this reason, when the B-color light source 13 is caused to emit light from the start of the second period T2, color mixing may occur. Therefore, in this embodiment, the B color light source 13 is caused to emit light with a delay of time ΔT. This is also true for the R color light source 11. Therefore, the time ΔT may be determined in consideration of the response characteristics of the liquid crystal. For example, when the applied voltage is changed, it may be time for the liquid crystal transmittance to be converted from 10% to 90%.

  The control circuit 50 writes the G-color image signal Vg for one screen in the second liquid crystal panel 200 in each of the first unit period Ta and the second unit period Tb. That is, writing is executed twice in one frame.

  Here, the second polarity signal Z2 becomes a high level designating the positive polarity in the first unit period Ta of each frame, and becomes the low level designating the negative polarity in the second unit period Tb of each frame. Therefore, the polarity of the G color image signal Vg written in the first unit period Ta of each frame is positive (+), and the polarity of the G color image signal Vg written in the second unit period Tb of each frame is negative. The voltage applied to the liquid crystal layer 105 is canceled out. Therefore, an alternating voltage is applied to the liquid crystal layer 105, and image sticking can be prevented.

  Further, since the light emission control signal Lg is always at a high level, the G color light source 21 always emits light. Since only the G color image is displayed on the second liquid crystal panel 100, even if the G color light source 21 always emits light, no color mixing occurs.

As described above, according to the first embodiment, one frame is divided into the first unit period Ta and the second unit period Tb, and the B-color image signal Vb is divided into the second unit period Ta during the first unit period Ta. The R color image signal Vr is supplied to the first liquid crystal panel 100 in the period Tb. Then, by inverting the polarity of the B-color image signal Vb between the first unit period Ta of the odd frame and the first unit period Ta of the even frame, the data signal Vd whose polarity is inverted is written to each pixel 110. An alternating voltage was applied to the liquid crystal layer 105. Further, by inverting the polarity of the R color image signal Vr in the second unit period Tb of the odd frame and the second unit period Tb of the even frame, the data signal Vd having the inverted polarity is written to each pixel 110. An alternating voltage was applied to the liquid crystal layer 105.
As a result, the voltage applied to the liquid crystal layer 105 between the data signals Vd of the same color over two frames can be offset, and burn-in can be prevented.

<2. Second Embodiment>
The projector according to the second embodiment is configured in the same manner as the projector according to the first embodiment except for the inversion timing of the first polarity signal Z1 and the polarities of the B-color image signal Vb and the R-color image signal Vr. .

  FIG. 6 shows a timing chart of the projector according to the second embodiment. The first polarity signal Z1 becomes a high level designating positive polarity in the first unit period Ta of the odd frame and the second unit period Tb of the even frame, and the second unit period Tb of the odd frame and the first unit of the even frame. It becomes a low level designating negative polarity in the period Ta. Therefore, the polarity of the B-color image signal Vb1 written in the first unit period Ta of the first frame F1 (odd number frame) is positive (+), and is written in the first unit period Ta of the second frame (even number frame). The polarity of the B-color image signal Vb2 is negative (−). Further, the polarity of the R color image signal Vr1 written in the second unit period Tb of the first frame F1 (odd number frame) is negative (−), and writing is performed in the second unit period Tb of the second frame (even number frame). The polarity of the R-color image signal Vr2 is positive (+). That is, in the first unit period Ta of the odd frame and the first unit period Tb of the even frame, the polarity of the data signal Vd is inverted with reference to the common potential LCcom, and the second unit period Tb of the odd frame and the second unit period of the even frame. In the unit period Tb, the polarity of the data signal Vd is inverted with respect to the common potential LCcom.

  Therefore, the voltage applied to the liquid crystal layer 105 is canceled out by the positive B color image signal Vb1 and the negative B color image signal Vb2, and the positive R color image signal Vr1 and the negative R signal. It cancels out with the color image signal Vr2. Therefore, an alternating voltage is applied to the liquid crystal layer 105, and image sticking can be prevented.

<3. Third Embodiment>
In the projectors according to the first and second embodiments, a B color image is displayed on the first liquid crystal panel 100 in the first unit period Ta of each frame, and an R color image is displayed in the first liquid crystal panel in the second unit period Tb. Displayed on panel 100. On the other hand, in the projector of the third embodiment, the first liquid crystal panel 100 displays an R color image in the second unit period Tb of the odd frame and the first unit period Ta of the even frame, A B-color image is displayed in the second unit period Tb and the first unit period Ta of the odd frame.

  In the projector according to the third embodiment, the inversion timing of the first polarity signal Z1, the relationship between the B color image signal Vb and the R color image signal Vr assigned to each frame, the B color image signal Vb and the R color image. Except for the polarity of the signal Vr and the timings of the light emission control signals Lr and Lb, the configuration is the same as that of the projector according to the first embodiment.

  FIG. 7 shows a timing chart of the projector according to the third embodiment. As shown in this figure, a B-color image is assigned to the first unit period Ta of the odd frame, and an R-color image is assigned to the second unit period Tb. Also, an R color image is assigned to the first unit period Ta of the even frame, and a B color image is assigned to the second unit period Tb. Therefore, the same color is assigned across the frames.

  The first polarity signal Z1 becomes a high level designating positive polarity in the first unit period Ta of each frame, and becomes a low level designating negative polarity in the second unit period Tb. Therefore, the R color image signal Vr1 in the second unit period Tb of the first frame (odd frame) is negative (−), and the R color image signal in the first unit period Ta of the second frame (even frame). Vr2 is positive (+). In addition, the B color image signal Vb2 in the second unit period Tb of the second frame (even number frame) has a negative polarity (−), and the B color image signal Vb3 in the first unit period Ta of the third frame (odd number frame). Becomes negative (-).

  That is, the polarity of the data signal Vd is inverted with respect to the common potential LCcom in the second unit period Tb of the odd frame and the first unit period Ta of the even frame. As a result, the voltage applied to the liquid crystal layer 105 is canceled out between the negative-polarity R-color image signal Vr and the positive-polarity R-color image signal Vr. Further, the polarity of the data signal Vd is inverted with respect to the common potential LCcom in the second unit period Tb of the even frame and the first unit period Ta of the odd frame. As a result, the voltage applied to the liquid crystal layer 105 is canceled out by the negative B-color image signal Vb and the positive B-color image signal Vb. Therefore, an alternating voltage is applied to the liquid crystal layer 105, and image sticking can be prevented.

Next, in the third period T3 of the second unit period Tb of the first frame (odd frame), the R color light source 11 is written until the writing of the R color data signal Vd for one screen to the first liquid crystal panel 100 is completed. The R color light source 11 emits light until the first unit period Ta of the second frame (even frame) ends from the second half of the second unit period Tb after the writing ends. In addition, the B-color light source 13 does not emit light.
In addition, in the third period T3 of the second unit period Tb of the second frame (even frame), until the writing of the B-color data signal Vd for one screen to the first liquid crystal panel 100 is completed, the R color light source 11 and The B-color light source 13 emits light until the first unit period Ta of the third frame (odd frame) ends from the second half of the second unit period Tb after the writing ends. In addition, the R color light source 11 does not emit light.

  More specifically, the light emission control signal Lr becomes high level with a delay of time ΔT from the start of the fourth period T4 located in the second half of the second unit period Tb of the first frame F1 (odd frame), and the second frame F2 At the end of the first unit period Ta of (even frame), the light emission control signal Lr becomes low level. For this reason, compared with 1st and 2nd embodiment, the period which the R color light source 11 light-emits can be lengthened.

In addition, the light emission control signal Lb becomes high level with a delay of time ΔT from the start of the fourth period T4 located in the second half of the second unit period Tb of the second frame F2 (even frame), and the third frame F3 (odd frame). At the end of the first unit period Ta, the light emission control signal Lb becomes low level. For this reason, compared with 1st and 2nd embodiment, the period which B light source 13 light-emits can be lengthened.

  In this way, the period during which the R color light source 11 and the B color light source 13 emit light can be lengthened by assigning images of the same color in the second unit period Tb of the immediately preceding frame and the first unit period Ta of the current frame. Therefore, in order to avoid color mixing, the period during which the R color light source 11 and the B color light source 13 do not emit light simultaneously can be shortened. Thereby, the projector of the third embodiment can display a bright image.

<4. Modification>
The present invention is not limited to the above-described embodiments, and for example, the following modifications are possible.
(1) In each of the above-described embodiments, the data signal of one screen is written into each pixel in the first period T1 of the first unit period Ta and the third period T3 of the second unit period, and the second period T2 and the fourth period T4. However, the present invention is not limited to this, and the data signal for one screen may be written in the second period T2 and the fourth period T4.
That is, writing may be executed in part or all of the first unit period Ta and the second unit period Tb. In this case, the data signal may be written with the polarity according to the first polarity signal Z1 of each of the above-described embodiments. Alternatively, a data signal having a polarity reversed from that of the first period T1 may be written in the second period T2, and a data signal having a polarity reversed from that of the third period T3 may be written in the fourth period T4. In this case, since the polarity inversion period can be shortened, burn-in of the liquid crystal layer 105 can be effectively prevented. Furthermore, a data signal based on the same image signal may be written in the first period T1 and the second period. In this case, even when there is no correlation between frames due to a scene change or the like, a data signal whose polarity is reversed can be written, so that the burn-in of the liquid crystal layer 105 can be effectively prevented.

(2) In each of the above-described embodiments, the second liquid crystal panel 200 that displays G color may be able to write an image of one screen in a period of 1/2 frame, but the first liquid crystal panel 200 has a period of 1/4 frame. It is necessary to write an image of one screen. Therefore, in the first liquid crystal panel 100, the two scanning lines 112 may be simultaneously selected so that the vertical resolution is ½ that of the second liquid crystal panel 200. Even if such control is performed, the human visual sensitivity is not higher in the B color and the R color than in the G color, so that it is possible to display a color image with no sense of incongruity as a whole.

(3) In the embodiment and the modification described above, the time ΔT may be zero. In this case, when the writing of the R color image signal Vr is completed, the R color light source 11 immediately emits light, and when the writing of the B color image signal Vb is completed, the B color light source 13 immediately emits light.

DESCRIPTION OF SYMBOLS 1 ... Projector, 11 ... R color light source, 13 ... B color light source, 21 ... G color light source, 30 ... Optical system, 50 ... Control circuit, 60 ... Light source drive circuit, 100 ... 1st Liquid crystal panel, 110... Pixel, 112... Scan line, 120... Scan line drive circuit, 200... Second liquid crystal panel, Ta... First unit period, Tb.

Claims (6)

A light source of a first color that emits light of a first color;
A light source of a second color that emits light of a second color;
A third color light source emitting a third color light;
A plurality of scanning lines, a plurality of data lines, a pixel electrode and a common electrode provided corresponding to the intersection of the scanning lines and the data lines and supplied with data signals supplied via the data lines; A first liquid crystal panel on which light from the first color light source and light from the second color light source are incident;
First driving means for driving the first liquid crystal panel;
A second liquid crystal panel in which light from the light source of the third color is incident on a plurality of pixels whose transmittance is controlled;
Second driving means for driving the second liquid crystal panel;
Optical means for combining and outputting the light transmitted through the first liquid crystal panel and the light transmitted through the second liquid crystal panel;
Light emission control means for controlling light emission of the light source of the first color and the light source of the second color;
One frame for displaying an image of one screen is divided into a first unit period and a second unit period which are units for driving the first liquid crystal panel in a time-sharing manner, and the frame is partially or entirely in the first unit period. A first color image signal indicating the luminance of each pixel of the first color is supplied to the first driving means, and a second signal indicating the luminance of each pixel of the second color in part or all of the second unit period. Image control means for supplying a color image signal to the first drive means,
The first driving means includes
Outputting the data signal to the plurality of data lines based on the first color image signal or the second color image signal;
In the first unit period of the odd frame and the first unit period of the even frame, the polarity of the data signal is inverted with reference to the potential of the common electrode,
The polarity of the data signal is inverted with respect to the potential of the common electrode between the second unit period of the odd frame and the second unit period of the even frame.
A projector characterized by that. The light emission control means includes
In the first half of the first unit period, the light source of the first color and the light source of the second color are not emitted until the writing of the data signal of the first color of one screen to the first liquid crystal panel is completed. And controlling so that the light source of the first color emits light and the light source of the second color does not emit light in the second half of the first unit period after the writing is finished,
In the first half of the second unit period, the light source of the first color and the light source of the second color are not emitted until the writing of the second color data signal of one screen to the first liquid crystal panel is completed. And controlling so that the light source of the second color emits light and the light source of the second color does not emit light in the second half of the second unit period after the writing is completed.
The projector according to claim 1. A light source of a first color that emits light of a first color;
A light source of a second color that emits light of a second color;
A third color light source emitting a third color light;
A plurality of scanning lines, a plurality of data lines, a pixel electrode and a common electrode provided corresponding to the intersection of the scanning lines and the data lines and supplied with data signals supplied via the data lines; A first liquid crystal panel on which light from the first color light source and light from the second color light source are incident;
First driving means for driving the first liquid crystal panel;
A second liquid crystal panel in which light from the light source of the third color is incident on a plurality of pixels whose transmittance is controlled;
Second driving means for driving the second liquid crystal panel;
Optical means for combining and outputting the light transmitted through the first liquid crystal panel and the light transmitted through the second liquid crystal panel;
Light emission control means for controlling light emission of the light source of the first color and the light source of the second color;
One frame for displaying an image of one screen is divided into a first unit period and a second unit period, which are units for driving the first liquid crystal panel in a time division manner, and a part of the first unit period of an odd frame or A first color image signal indicating the luminance of each pixel of the first color is supplied to the first driving means in all, and each pixel of the second color in part or all of the second unit period of an odd frame. The second color image signal indicating the luminance of the second color is supplied to the first drive means, and the second color image signal is supplied to the first drive means in part or all of the first unit period of the even frame. Image control means for supplying the first color image signal to the first drive means in part or all of the second unit period of even frames,
The first driving means includes
Outputting the data signal to the plurality of data lines based on the first color image signal or the second color image signal;
In the second unit period of the odd frame and the first unit period of the even frame, the polarity of the data signal is inverted with reference to the potential of the common electrode,
In the second unit period of the even frame and the first unit period of the odd frame, the polarity of the data signal is inverted with reference to the potential of the common electrode.
A projector characterized by that. The light emission control means includes
In the first half of the second unit period of the odd-numbered frame, the first color light source and the second color light source remain until the writing of the second color data signal of one screen to the first liquid crystal panel is completed. The light source of the second color emits light from the latter half of the second unit period after the writing is completed until the first unit period of the even-numbered frame is completed and the light is emitted. The first color light source is controlled so as not to emit light,
In the first half of the second unit period of the even frame, the light source of the first color and the light source of the second color are not written until the writing of the first color data signal of one screen to the first liquid crystal panel is completed. The light source of the first color emits light from the latter half of the second unit period after the writing is completed until the first unit period of the odd-numbered frame is finished and the light is emitted. Controlling the second color light source to emit no light,
The projector according to claim 3. A first color light source that emits light of a first color, a second color light source that emits light of a second color, a third color light source that emits light of a third color, and a plurality of scanning lines A voltage between a pixel electrode and a common electrode provided corresponding to a plurality of data lines and an intersection of the scanning line and the data line and supplied with a data signal supplied via the data line; A first liquid crystal panel on which light from the light source of the first color and light from the light source of the second color are incident, and a plurality of pixels whose transmittance is controlled. A second liquid crystal panel in which light from the light source of the third color is incident on the pixel, and optical means for combining and outputting the light transmitted through the first liquid crystal panel and the light transmitted through the second liquid crystal panel A projector control method comprising:
One frame for displaying an image of one screen is divided into a first unit period and a second unit period, which are units for driving the first liquid crystal panel in a time division manner,
Writing the data signal of the first color indicating the luminance of each pixel of the first color to each pixel of the first liquid crystal panel in a part or all of the first unit period;
The data signal of the second color indicating the luminance of each pixel of the second color is written to each pixel of the first liquid crystal panel in part or all of the second unit period,
In the first unit period of the odd frame and the first unit period of the even frame, the polarity of the data signal is inverted with reference to the potential of the common electrode,
In the second unit period of the odd frame and the second unit period of the even frame, the polarity of the data signal is inverted with reference to the potential of the common electrode.
And a projector control method. A first color light source that emits light of a first color, a second color light source that emits light of a second color, a third color light source that emits light of a third color, and a plurality of scanning lines A voltage between a pixel electrode and a common electrode provided corresponding to a plurality of data lines and an intersection of the scanning line and the data line and supplied with a data signal supplied via the data line; A first liquid crystal panel on which light from the light source of the first color and light from the light source of the second color are incident, and a plurality of pixels whose transmittance is controlled. A second liquid crystal panel in which light from the light source of the third color is incident on the pixel, and optical means for combining and outputting the light transmitted through the first liquid crystal panel and the light transmitted through the second liquid crystal panel A projector control method comprising:
One frame for displaying an image of one screen is divided into a first unit period and a second unit period, which are units for driving the first liquid crystal panel in a time division manner,
Writing the data signal of the first color indicating the luminance of each pixel of the first color to each pixel of the first liquid crystal panel in a part or all of the first unit period;
The data signal of the second color indicating the luminance of each pixel of the second color is written to each pixel of the first liquid crystal panel in part or all of the second unit period,
In the first unit period of the odd frame and the first unit period of the even frame, the polarity of the data signal is inverted with reference to the potential of the common electrode,
In the second unit period of the odd frame and the second unit period of the even frame, the polarity of the data signal is inverted with reference to the potential of the common electrode.
And a projector control method.

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