Display device and projector

Since green is expressed by the first sub-pixels and the second sub-pixels, and at the same time, red is expressed by the third sub-pixels using the yellow illumination light, and green is expressed by the first sub-pixels and the second sub-pixels, and at the same time, blue is expressed by the third sub-pixels using the cyan illumination light, the display device can assure the apparent resolution and the brightness using the first and second sub-pixels with greenish color. It should be noted that red and blue can be expressed by the third sub-pixels with magenta color.

BACKGROUND

1. Technical Field

The present invention relates to a display device capable of displaying a color image and a projector using the display device.

2. Related Art

As a projector provided with a display device, there has been a device of projecting color image light, which is displayed on a color liquid crystal panel color-coded with an interference color filter, on a screen using a lens in an enlarged manner (see FIG. 7 of JP-A-2000-35569 (Document 1)).

Further, there has been a device of making illumination light enter a color switch to thereby sequentially output a red light beam, a green light beam, and a blue light beam, then illuminating a reflective liquid crystal display element with these light beams via a polarization beam splitter, and then taking out picture light beam due to branching in the polarization beam splitter (see FIG. 3 of JP-A-2002-341439 (Document 2)).

However, the color liquid crystal panel used in the projector of Document 1 is color-coded with the color filter into red, blue, and green, and is required to have the number of pixels more than three times of the required resolution. Therefore, the panel problematically grows in size, or the aperture ratio is problematically lowered.

Further, such a projector as described in Document 2 has high request level to the response speed, and in particular in the case of using the liquid crystal panel, it becomes difficult to keep the response speed proper, and a device is required in the way of scanning of scan lines.

It should be noted that in a color liquid crystal panel incorporating a color filter, there exists a method called a Bayer method for reducing the number of sub-pixels. In this method, the ratio of the sub-pixel numbers of green, red, and blue is set to 2:1:1, and the sub-pixel number of green is made coincide with the resolution. In this case, there is used the fact that by making the sub-pixel number of green coincide with the resolution, the apparent feeling of resolution is not damaged even if the sub-pixel number of red or blue is reduced to half, and there is an advantage that the total sub-pixel number is suppressed to two times of the resolution.

SUMMARY

An advantage of some aspects of the invention is to provide a display device capable of preventing the sub-pixel number from increasing while keeping the response speed, and a projector using the display device.

An aspect of the invention is directed to a display device including (a) a light modulation element having at least one first sub-pixel with green color, at least one second sub-pixel including green color, and at least one third sub-pixel with magenta color, and (b) a light source capable of illuminating the light modulation element with yellow illumination light and cyan illumination light, (c) green is expressed by the first sub-pixel and the second sub-pixel, and red is expressed by the third sub-pixel using the yellow illumination light, and (d) green is expressed by the first sub-pixel and the second sub-pixel, and blue is expressed by the third sub-pixel using the cyan illumination light.

Since in the display device described above, green is expressed by the first sub-pixel and the second sub-pixel, and at the same time red is expressed by the third sub-pixel using the yellow illumination light, and green is expressed by the first sub-pixel and the second sub-pixel, and at the same time, blue is expressed by the third sub-pixel using the cyan illumination light, the display device can assure the apparent resolution and the brightness using the first and second sub-pixels with greenish color. It should be noted that red and blue can be expressed by the third sub-pixel with magenta color.

In a specific aspect of the invention, a ratio of the total number of the first and second sub-pixels and the number of the third sub-pixel(s) is 2:1. In this case, the apparent resolution can be assured by the first and second sub-pixels with greenish color, namely two-thirds of the total sub-pixels.

According to another aspect of the invention, in the display device described above, the second sub-pixel is a white sub-pixel. In this case, it is possible to improve the resolution and the brightness while restraining the luminance of green color to keep the color balance.

According to still another aspect of the invention, the light source illuminates the light modulation element while switching between the yellow illumination light and the cyan illumination light in a time-sharing manner. In this case, the color image can be displayed by operating the single light modulation element while switching between the display states thereof.

According to yet another aspect of the invention, when illuminating the first sub-pixel with green color, the second sub-pixel with white color, and the third sub-pixel with magenta color with the yellow illumination light, the third sub-pixel with magenta color is operated by a red signal, and the first sub-pixel with green color and the second sub-pixel with white color are operated by a green signal, and when illuminating the first sub-pixel with green color, the second sub-pixel with white color, and the third sub-pixel with magenta color with the cyan illumination light, the third sub-pixel with magenta color is operated by a blue signal, and the first sub-pixel with green color and the second sub-pixel with white color are operated by a green signal. In this case, it results that yellow and cyan are expressed by the second sub-pixel with white color, and as a result, original green color is expressed in a reinforcing manner using green added with white.

According to still yet another aspect of the invention, the light source includes a green light emitting element, a red light emitting element, and a blue light emitting element, lights the green light emitting element and the red light emitting element when illuminating the light modulation element with the yellow illumination light, and lights the green light emitting element and the blue light emitting element when illuminating the light modulation element with the cyan illumination light. In this case, yellow color and cyan color can easily be formed using the combination of the light emitting elements.

According to further another aspect of the invention, the light modulation element is a liquid crystal display device. In this case, even if the response speed of display is low, the quality of display can be improved by decreasing the frequency of rewriting of the light modulation element.

Still further another aspect of the invention is directed to a projector including (a) the display device described above, and (b) a projection lens adapted to project an image formed by the display device.

According to the display device described above, a high-quality image can be projected using the high-resolution bright display device.

DESCRIPTION OF AN EXEMPLARY EMBODIMENT

As shown inFIG. 1, the projector100is provided with an optical system part10and a circuit device20.

The optical system part10is provided with a light source11for illumination, a lens12for light beam adjustment, a liquid crystal display device14as a light modulation element, and a projection lens15for enlarged projection.

As schematically shown also inFIG. 2A, the light source11is provided with a light emitting section11afor emitting illumination light IL for illuminating the liquid crystal display device14shown inFIG. 1, and a concave mirror11bfor light collection for controlling the emission state of the illumination light IL. In this case, the light emitting section11aincorporates three light emitting elements EG, ER, and EB. The first light emitting element EG generates green illumination light, the second light emitting element ER generates red illumination light, and the third light emitting element EB generates blue illumination light. These light emitting elements EG, ER, and EB are each formed of, for example, an LED, and can be made to emit light at an individual timing. In a specific operation, by lighting the green light emitting element EG and the red light emitting element ER at the same time, first illumination light L1with yellow color can be emitted from the light emitting section11a, and by lighting the green light emitting element EG and the blue light emitting element EB at the same time, second illumination light L2with cyan color can be emitted from the light emitting section11a. It should be noted that the emission luminance can be made equal between the light emitting elements EG, ER, and EB of the respective colors, or can be provided with an appropriate luminance difference between the colors to thereby adjust the color balance of the illumination light IL to a desired state.

Returning toFIG. 1, the liquid crystal display device14is for spatially modulating the illumination light IL from the light source11, and is provided with a liquid crystal panel14ahaving a structure of sandwiching a liquid crystal layer with a pair of substrates each provided with a transparent electrode and so on, and a pair of polarization plates (not shown) disposed so as to sandwich the liquid crystal panel14afrom the both sides along the optical axis OA. The liquid crystal display device14modulates the illumination light IL having entered from the light source11via the lens12to thereby form image light GL.

As schematically shown inFIG. 2B, the sub-pixels PE constituting the liquid crystal panel14aare obtained by segmentalizing the color display pixels (so called pixels), evenly arranged two-dimensionally in vertical and horizontal directions, and sectioned into first sub-pixels PG with green color, second sub-pixels PW with white color, and third sub-pixels PM with magenta color. Firstly, the first sub-pixels PG (G) with green color are tightly arranged in a lateral line in an X direction. The second sub-pixels PW (W) with white color are tightly arranged in a lateral line in the X direction so as to be adjacent to a −Y side of the first sub-pixels PG with green color. The third sub-pixels PM (Mz) with magenta color are tightly arranged in a lateral line in the X direction so as to be adjacent to a −Y side of the second sub-pixels PW with white color. Further, the first sub-pixels PG (G) with green color are tightly arranged in a lateral line in the X direction so as to be adjacent to a −Y side of the third sub-pixels PM with magenta color. As described above, in the case of the present embodiment, the sub-pixels PE with the same color are arranged in the lateral X direction, and the sub-pixels PE with green color, the white color, and the magenta color are periodically arranged in the vertical Y direction. Here, regarding the first sub-pixels PG with green color and the third sub-pixels PM with magenta color, the color filters with the colors corresponding respectively thereto are formed so as to cover the apertures of the respective sub-pixels PE. Regarding the second sub-pixels PW with white color, no color filter with the color corresponding thereto is provided. It should be noted that a transparent film or the like for equalizing the cell thickness can be provided instead of the color filter. It should be noted that although the explanation is omitted for the sake of simplification, black matrix can be disposed on the boundaries between the sub-pixels PG, PW, and PM in order to prevent color mixture between the sub-pixels PG, PW, and PM.

In the case described hereinabove, the proportions of the green first sub-pixels PG, the second sub-pixels PW with white color, and the third sub-pixels PM with magenta color are equal to each other, namely 1:1:1. In other words, the ratio of the total number of the first and second sub-pixels PG, PW and the number of the third sub-pixels PM is 2:1.

Returning toFIG. 1, the projection lens15projects the image light GL, which is modulated by the liquid crystal display device14, on a screen not shown as an enlarged color image.

The circuit device20is provided with an image processing section81to which an external image signal such as a video signal is input, a display drive section82for driving the liquid crystal display device14provided to the optical system part10based on the output of the image processing section81, a light source drive section83for driving the light source11provided to the optical system part10based on the output of the image processing section81, and a main control section88for performing overall control of the operations of these circuit parts81,82,83, and so on.

The image processing section81is provided with a color tone correction section81afor converting the external image signal input thereto into the image signal including the tones of the respective colors. The color tone correction section81amakes it possible to make the light modulation operation by the sub-pixels PE constituting the liquid crystal panel14aof the liquid crystal display device14appropriate. It should be noted that it is also possible for the image processing section81to perform various image processing such as distortion correction or color correction on the external image signal.

The display drive section82can drive the liquid crystal display device14based on the image signal output from the image processing section81to thereby make the liquid crystal display device14form the image corresponding to the image signal. In other words, the display drive section82individually operates the sub-pixels PE (the sub-pixels PG, PW, and PM of the respective colors) provided to the liquid crystal panel14aof the liquid crystal display device14based on the image signal from the image processing section81. Specifically, the display drive section82outputs a drive signal for appropriately varying the light transmission in each of the sub-pixels PE of the liquid crystal panel14ato the liquid crystal panel14ato thereby make the liquid crystal panel14aperiodically perform rewriting of the pixel drive signal in each of the sub-pixels PE.

The light source drive section83can drive the light source11based on a lighting signal output from the image processing section81to thereby make the light source11perform lighting in a state corresponding to the lighting signal. In other words, the light source drive section83can individually light the light emitting elements EG, ER, and EB included in the light source11. In the case of the present embodiment, the green light emitting element EG and the red light emitting element ER in the light source11are lighted at the same time at a first timing to thereby emit the first illumination light L1with yellow color from the light emitting section11a. Further, the green light emitting element EG and the blue light emitting element EB in the light source11are lighted at the same time at a second timing to thereby emit the second illumination light L2with cyan color from the light emitting section11a.

In the projector100described above, a part composed of the light source11, the lens12, and the liquid crystal display device14out of the optical system part10and the circuit device20constitutes a display device200, and forms a part capable of displaying an image by itself.

FIGS. 3Aand BE are conceptual diagrams for explaining a basic operation of the optical system part10and so on.

FIG. 3Ashows a first display state by the optical system part10, wherein the light source11lights the green light emitting element EG and the red light emitting element ER at the same time as the first timing to thereby emit the first illumination light L1with yellow color from the light emitting section11a. As a result of this operation, the liquid crystal display device14or the liquid crystal panel14ais illuminated with the yellow illumination light LY, and the image PP projected by the projection lens15includes sub-display pixels Pg1corresponding to the first sub-pixels PG with green color, sub-display pixels Py1corresponding to the second sub-pixels PW with white color, and sub-display pixels Pr1corresponding to the third sub-pixels PM with magenta color. These sub-display pixels Pg1, Py1, and Pr1are arranged in respective lines in the lateral direction and at the same time repeatedly disposed in series in the vertical direction in accordance with the sub-pixel arrangement of the liquid crystal panel14a. Here, the first sub-pixels PG with green color are illuminated with the yellow illumination light LY of the first illumination light L1, but perform green display as a result since the red component is eliminated by the color filter. In other words, the sub-display pixels Pg1are observed as green display. Then, the second sub-pixels PW with white color are illuminated with the yellow illumination light LY of the first illumination light L1, and perform yellow display since no extinction is performed by the color filter. In other words, the sub-display pixels Py1are observed as yellow display. Finally, the third sub-pixels PM with magenta color are illuminated with the yellow illumination light LY of the first illumination light L1, but perform red display as a result since the complementary color of magenta, namely the green component, is eliminated by the color filter. In other words, the sub-display pixels Pr1are observed as red display.

FIG. 3Bshows a second display state by the optical system part10, wherein the light source11lights the green light emitting element EG and the blue light emitting element EB at the same time as the second timing to thereby emit the second illumination light L2with cyan color from the light emitting section11a. As a result of this operation, the liquid crystal display device14or the liquid crystal panel14ais illuminated with the cyan illumination light LC, and the image PP projected by the projection lens15includes sub-display pixels Pg2corresponding to the first sub-pixels PG with green color, sub-display pixels Pc2corresponding to the second sub-pixels PW with white color, and sub-display pixels Pb2corresponding to the third sub-pixels PM with magenta color. These sub-display pixels Pg2, Pc2, and Pb2are arranged in respective lines in the lateral direction and at the same time repeatedly disposed in series in the vertical direction in accordance with the sub-pixel arrangement of the liquid crystal panel14a. Here, the first sub-pixels PG with green color are illuminated with the cyan illumination light LC of the second illumination light L2, but perform green display as a result since the blue component is eliminated by the color filter. In other words, the sub-display pixels Pg2are observed as green display. Then, the second sub-pixels PW with white color are illuminated with the cyan illumination light LC of the second illumination light L2, and perform cyan display since no extinction is performed by the color filter. In other words, the sub-display pixels Pc2are observed as cyan display. Finally, the third sub-pixels PM with magenta color are illuminated with the cyan illumination light LC of the second illumination light L2, but perform blue display as a result since the complementary color of magenta, namely the green component, is eliminated by the color filter. In other words, the sub-display pixels Pb2are observed as blue display.

The display state of a specific pixel (a specific color display pixel or a specific block pixel) PX in the image PP projected by the projection lens15will be explained with reference toFIG. 4. In the case of the illumination by the first illumination light L1corresponding toFIG. 3A, namely when performing the illumination with the yellow illumination light LY obtained by lighting the green light emitting element EG and the red light emitting element ER in combination, the specific pixel PX is observed by the eyes EY of the observer as a first pixel (the block pixel) PX1having the sub-display pixels Pg1, Py1, and Pr1combined with each other. On the other hand, in the case of the illumination by the second illumination light L2corresponding toFIG. 3B, namely when performing the illumination with the cyan illumination light LC obtained by lighting the green light emitting element EG and the blue light emitting element EB in combination, the specific pixel PX is observed by the eyes EY of the observer as a second pixel (the block pixel) PX2having the sub-display pixels Pg2, Pc2, and Pb2combined with each other. In other words, in the case of the yellow illumination (the first display state) by the first illumination light L1, the display is performed as the first pixel PX1having the three sub-display pixels Pg1, Py1, and Pr1composed of green, yellow, and red as a set, and in the case of the cyan illumination (the second display state) by the second illumination light L2, the display is performed as the second pixel PX2having the three sub-display pixels Pg2, Pc2, and Pb2composed of green, cyan, and blue as a set. Further, since the first pixel PX1and the second pixel PX2are switched in, for example, the time half as long as two frames, it results that the combination of the both pixels PX1, PX2represents the color pixel (the pixel block) of a specific point in the image. In other words, the image signal of the specific point in the image to be projected corresponds to the combination of the signals corresponding to the both pixels PX1, PX2.

The specific operations of the liquid crystal display device14and the light source11will be explained based onFIG. 5. Firstly, the green light emitting element EG is always lighted, and the green illumination, namely G illumination, is continuous. Further, the red light emitting element ER is lighted periodically, and the red illumination, namely R illumination, is performed intermittently in the latter half period TR of the basic period T0corresponding to the two frames. The blue light emitting element EB is also lighted periodically, and the blue illumination, namely B illumination, is performed intermittently in the former half period TB of the basic period T0.

Regarding the rewriting of the sub-pixels PG, PW, and PM of the respective colors, the rewriting of the drive signal (the blue signal) corresponding to blue color performed on the third sub-pixels PM with magenta color in the primary period t1of the frame. On this occasion, the red light emitting element ER and the blue light emitting element EB are stopped in order to avoid color mixture. In a period t2subsequent to the period t1, the rewriting of the drive signal (the green signal) corresponding to green color is performed on the first sub-pixels PG with green color. On this occasion, although the blue light emitting element EB is lighted, these sub-pixels do not interfere with each other. In a period t3subsequent to the period t2, the rewriting of the drive signal (the green signal) corresponding to green color is performed on the second sub-pixels PW with white color. On this occasion, the blue light emitting element EB is lighted besides the green light emitting element EG, and the second sub-pixels PW with white color is illuminated with the yellow illumination light LY, namely the first illumination light L1. In a period t4subsequent to the period t3, the rewriting of the drive signal (the red signal) corresponding to red color is performed on the third sub-pixels PM with magenta color. On this occasion, the red light emitting element ER and the blue light emitting element EB are stopped in order to avoid color mixture. In a period t5subsequent to the period t4, the R illumination is started. In a period t6subsequent to the period t5, the rewriting of the drive signal (the green signal) corresponding to green color is performed on the second sub-pixels PW with white color. On this occasion, the red light emitting element ER is lighted besides the green light emitting element EG, and the second sub-pixels PW with white color is illuminated with the cyan illumination light LC, namely the second illumination light L2.

In the operations described hereinabove, it results that the periods t2, t3correspond to the first display state shown inFIG. 3A. Further, it results that the periods t5, t6correspond to the second display state shown inFIG. 3B.

FIGS. 6A through 6Dare diagrams for visually explaining the rewriting of the sub-pixels PG, PW, and PM of the respective colors.FIG. 6Ashows the rewriting or writing of the blue signal to the third sub-pixels PM with magenta color, and illustrates the process during the period t1shown inFIG. 5. Thus, the blue display by the third sub-pixels PM with magenta color is prepared.FIG. 6Bshows the rewriting or writing of the green signal to the first sub-pixels PG with green color, and illustrates the process during the period t2shown inFIG. 5. Thus, the green display by the first sub-pixels PG with green color is gradually updated.FIG. 6Cshows the rewriting or writing of the green signal to the second sub-pixels PW with white color, and illustrates the process during the period t3shown inFIG. 5. Thus, the green display (here, the yellow display) by the second sub-pixels PW with white color is gradually updated.FIG. 6Dshows the rewriting or writing of the red signal to the third sub-pixels PM with magenta color, and illustrates the process during the period t4shown inFIG. 5. Thus, the red display by the third sub-pixels PM with magenta color is prepared.

It should be noted that although in the period t2shown inFIG. 6Bthe first sub-pixels PG with green color are rewritten while keeping the green light emitting element EG in the lighting state, the problem such as color mixture does not arise. Further, although in the period t3shown in FIG.6C the second sub-pixels PW with white color are rewritten while keeping the blue light emitting element EB in the lighting state, the problem such as color mixture does not arise. It should be noted that, although in the period t6not shown the second sub-pixels PW with white color are rewritten in accordance with the green signal while keeping the red light emitting element ER in the lighting state, the problem such as color mixture does not arise. Regarding the second sub-pixels PW described hereinabove, the green display is performed by the whole of the combination of the yellow display in the periods t2, t3and the cyan display in the periods t5, t6.

Here, the display with the second sub-pixels PW with white color will be explained in further detail. In the first display state shown inFIG. 3A, the yellow sub-display pixels Py1are formed on the screen by the second sub-pixels PW with white color. Meanwhile, in the second display state shown inFIG. 3B, the cyan sub-display pixels Pc2are formed on the screen by the second sub-pixels PW with white color. These processes correspond respectively to the periods t5, t6(seeFIG. 5) corresponding to the R illumination at the first timing and the periods t2, t3(seeFIG. 5) corresponding to the B illumination at the second timing, and are periodically repeated at a high rate, and therefore, the cyan sub-display pixels Pc2and the yellow sub-display pixels Py1are visually recognized as being combined with each other (see, for example,FIG. 4). Specifically, it results that the observer observes the color obtained by adding yellow and cyan to each other, namely the color obtained by adding white to green. Here, since roughly 80% of the luminance of white is derived from the green component, and white has a property of making the observer feel green if white is added to green, by adding white, it is possible to enhance the apparent brightness without changing the color tone. Further, by the second sub-pixels PW with white color in addition to the first sub-pixels PG with green color, the resolution of the projected image can be improved to be two times of the resolution obtained by the first sub-pixels PG with green color alone. Here, since the red sub-display pixels Pr1and the blue sub-pixels Pb2are formed by the third sub-pixels PM with magenta color, the resolution is formally degraded with respect to red color and blue color, but the apparent resolution is kept high due to the first sub-pixels PG with green color and the second sub-pixels PW with white color.

As described above, according to the projector100of the present embodiment, since green is expressed by the first sub-pixels PG and the second sub-pixels PW, and at the same time, red is expressed by the third sub-pixels PM using the yellow illumination light LY, and green is expressed by the first sub-pixels PG and the second sub-pixels PW, and at the same time, blue is expressed by the third sub-pixels PM using the cyan illumination light LC, the apparent resolution and the brightness can be assured due to the first and second sub-pixels PG, PW with greenish color. It should be noted that red and blue can be expressed by the third sub-pixels PM with magenta color. In the present embodiment, it results that the field sequential display is performed with respect to red and blue colors, and the continuous display is performed with respect to green color. Therefore, the color break-up can be made inconspicuous.

The invention is not limited to the embodiment described above, but can be put into practice in various forms within the scope of the invention.

For example, the second sub-pixels PW with white color can be changed to green sub-pixels added with a green color filter. Also in this case, it is possible to improve the resolution and the brightness of the image by increasing the sub-pixel density of green color. Further, the second sub-pixels PW with white color can be changed to yellow sub-pixels added with a yellow color filter. In other words, regarding the second sub-pixels PW, the color can arbitrarily be selected in accordance with the luminance of the light source, the color balance, and so on providing the color includes green color.

Further, the arrangement and the density of the sub-pixels PG, PW, and PM in the liquid crystal panel14aare not limited to those shown inFIG. 2B, but can be set to, for example, the Bayer type. In this case, the two pixels out of the set of four pixels (i.e., the block pixels) can be assigned to either one of green, white, and magenta.

Although in the embodiment described above it is assumed that the light emitting elements EG, ER, and EB of the light source11are each formed of the LED, the light emitting elements EG, ER, and BB can also be formed of other light emitting elements.

Although in the embodiment described above, the illumination light IL from the light source11is used without modulation, it is also possible to align the polarization direction of the illumination light IL to a specific direction.

The liquid crystal panel14ais not limited to the transmissive type, but can be set to the reflective type. It should be noted here that “transmissive type” denotes that the liquid crystal panel is a type of transmitting the light, and “reflective type” denotes that the liquid crystal panel is a type of reflecting the light.

As the projector, a front projector performing image projection form a direction of observing the projection screen and a rear projector performing image projection from the opposite direction of observing the projection screen can be cited, and the configuration of the projector shown inFIG. 1and so on can be applied to either of the types of the projectors.

It is also possible to use the digital micromirror device or the like having micromirrors each provided with a color filter as the sub-pixels as the light modulation element instead of the liquid crystal panel14a.

The entire disclosure of Japanese Patent Application No. 2011-062563, filed Mar. 22, 2011 is expressly incorporated by reference herein.