Patent Grant
8179348
1. Technical Field
The present invention relates to a method for driving various kinds of display devices and a circuit for driving various kinds of display devices. In addition, the present invention relates to an electro-optical device that uses such a driving method or is provided with such a driving circuit and further relates to an electronic apparatus that is provided with such an electro-optical device. An example of a variety of display devices to which the invention is directed is a liquid crystal display device, though not limited thereto. A non-limiting example of a variety of electronic apparatuses to which the invention is directed is a liquid crystal projector.
2. Related Art
In the technical field to which the present invention pertains, a field-sequential driving scheme has been proposed so far as one known method for driving various kinds of display devices such as a liquid crystal display device or the like. In a typical field-sequential drive operation, a backlight (e.g., backlight illumination device) emits red light, green light, and blue light in a periodic manner so as to display images in full color (i.e., full-color display). In such a periodic light-emission operation, the backlight emits light for each color (e.g., color tone or hue) independently of others. For this reason, such a typical field-sequential display is susceptible to color mixture. In an effort to provide a technical solution to such a color-mixture image problem, a method for effectively preventing or reducing the occurrence of color mixture has been proposed in the related art.
As one example thereof, JP-A-11-237606 discloses a technique for realizing uniform luminance distribution on the display screen of a liquid crystal panel at the start of writing operation, which is achieved by providing a reset time interval.
However, if the related-art technique described in JP-A-11-237606 is adopted, it is necessary to display black on the screen during the reset time interval, resulting in the prolonged liquid-crystal response time during the subsequent driving operation of liquid crystal, which follows the reset time interval. For this reason, as one specific example of technical disadvantages thereof, the responding state/behavior of the liquid crystal is not at a sufficiently transmissive level during the light emission time period of the backlight. As a result thereof, the brightness/luminance level of actual display is unsatisfactorily low.
An advantage of some aspects of the invention is to provide a method for driving various kinds of display devices such as a liquid crystal device, though not limited thereto, which makes it possible for the display device to display images with high brightness and to represent correct color. In addition, the invention provides, as an advantage of some aspects thereof, a circuit for driving a variety of display devices that makes it possible for the display device to display images with high brightness and to represent correct color. Moreover, the invention provides, as an advantage of some aspects thereof, an electro-optical device that uses such a driving method or is provided with such a driving circuit. Furthermore, the invention provides, as an advantage of some aspects thereof, an electronic apparatus that is provided with such an electro-optical device. Note that the term “brightness” used in this paragraph as well as in the recitation of appended claims includes the meaning of “luminance” without any limitation thereto.
In order to address the above-identified problem without any limitation thereto, the invention provides, as a first aspect thereof, a method for driving a display device that includes: irradiating a plurality of light beams toward a display area in a time-divided manner, each of the plurality of light beams having an individual and/or own color that differs from those of others, the display area having a plurality of pixel units; converting display data that is to be supplied to the plurality of pixel units on the basis of at least one predetermined conversion rule for each of a plurality of fields, the plurality of fields being determined so as to correspond to respective light emission time periods of the plurality of light beams, the plurality of fields following one after another in a successive manner on a time axis, the predetermined conversion rule having been prepared so as to achieve an actual value that is close to a desired value for at least either one of brightness and color (hue) obtained when an image is displayed in the display area; and supplying the converted display data to the plurality of pixel units in a sequential manner for each of the plurality of fields.
In the method for driving a display device according to the first aspect of the invention described above, a plurality of light beams is emitted toward a display area in a time-divided manner. Each of the plurality of light beams has an individual and/or own color that differs from those of others. The display area has a plurality of pixel units. Herein, the term “pixel units” is used to encompass the meaning of pixel portions, pixel regions, pixel areas, or pixels, without any limitation thereto. That is, the plurality of light beams is irradiated toward the display area by means of a field-sequential driving scheme on an independent basis, that is, independently of one another. The irradiation of the plurality of light beams is performed in a frequency of, for example, 60 Hz or so (i.e., in a periodic manner). The plurality of light beams may be emitted from a plurality of light sources. For example, the plurality of light beams may be irradiated from a plurality of light-emitting diodes (LED) each of which has an individual and/or own color that differs from those of others. Or, alternatively, the plurality of light beams may be emitted from not plural light sources but a single light source. For example, the plurality of light beams may be emitted from a white light source that irradiates light having a plurality of color components. If a plurality of light sources is used, a (combined) light beam that changes its color at every moment of time enters each of the plurality of pixels of an electro-optical device as an incident projection light-source light beam or as an incident backlight beam. More specifically, each of the plurality of light beams that is irradiated from the plurality of light sources enters a color-combining optical unit such as a color-combination prism or the like. As a result thereof, as explained above, a “combined” light beam that changes its color at every moment of time propagates on the same single optical path to enter each of the plurality of pixels of an electro-optical device. On the other hand, if a single light source is used, a rotary color filter is provided on the optical path, although other alternative coloring (e.g., color-separating) scheme may be used. A light beam that is emitted from the single light source passes through the rotary color filter. As a result thereof, as explained above, a light beam that changes its color at every moment of time propagates on the single optical path to enter each of the plurality of pixels of an electro-optical device.
In the method for driving a display device according to the first aspect of the invention described above, display data that is to be supplied to the plurality of pixel units is converted for each of a plurality of fields. The “plurality of fields” is a set of time periods that are determined so as to correspond to the respective light emission time periods of the plurality of light beams. That is, each of the plurality of fields is associated with the light-emitting time period of the corresponding light beam. The plurality of fields follows one after another in a successive manner on a time axis. As a typical non-limiting example thereof, the plurality of fields is preset (i.e., predetermined) in such a manner that each of the plurality of fields is in synchronization with the light-emitting time period of the corresponding light beam. Or, as another non-limiting typical example thereof, the plurality of fields is preset in such a manner that each of the plurality of fields has a special/particular relation to the light-emitting time period of the corresponding light beam. Or, alternatively, the plurality of fields may not be predetermined but be determined in a variable manner on a real-time basis in accordance with the light emission time period or in accordance with the display data. That is, the plurality of fields may be variably set on a real-time basis as one parameter that is used to improve display quality.
Since display data is converted for each of the plurality of fields in the method for driving a display device according to the first aspect of the invention described above, it is possible to achieve adequate data conversion for the corresponding light emission time period. Or, in other words, because display data is converted for each of the plurality of fields in the driving method according to the first aspect of the invention described above, it is possible to achieve adequate data conversion for the corresponding color of a plurality of light beams (i.e., the corresponding one of a plurality of color tones or hues). It should be particularly noted that, in the driving method according to the first aspect of the invention described above as well as other aspects thereof, the effects of display-data conversion that is performed in each of the plurality of fields that is associated with the light-emitting time period of the corresponding light beam are not always limited to the brightness and color (hue) for the above-mentioned (one) light-emitting time period. That is, in the driving method according to the first aspect of the invention described above as well as other aspects thereof, display-data conversion that is performed in each of the plurality of fields that is associated with the light-emitting time period of the corresponding light beam could have effects on the brightness and color (hue) not only for the above-mentioned light-emitting time period but also for other light-emitting time periods corresponding to other fields such as the preceding field and the next field.
In the method for driving a display device according to the first aspect of the invention described above, data conversion is performed on the basis of at least one predetermined conversion rule. The “predetermined conversion rule” has been prepared either theoretically or empirically so as to achieve an actual value that is close to a desired value for at least either one of brightness and color (hue) obtained when an image is displayed in the display area. That is, display data is converted in such a manner that actual brightness and/or color approximates desired brightness and/or color. Such data conversion can be performed, typically, by means of a conversion table that is prepared on the basis of a conversion rule for each field.
After the data conversion, the display data is supplied to the plurality of pixel units for each of the plurality of fields, and thus in a field-sequential manner. That is, the converted display data is supplied to the plurality of pixel units at timing corresponding to the light emission time periods of the plurality of light beams. Therefore, it is possible to display images having actual brightness and/or color close to desired brightness and/or color at the display area of a display device.
As explained above, in the method for driving a display device according to the first aspect of the invention, display data is converted for each of a plurality of fields; and therefore, it is possible to display images having actual brightness and/or color close to desired brightness and/or color at the display area of a display device.
It is preferable that the method for driving a display device according to the first aspect of the invention described above should further include: setting the plurality of fields in such a manner that the plurality of fields correspond to the respective light emission time periods of the plurality of light beams and that the plurality of fields follow one after another in a successive manner on a time axis, wherein the above-mentioned conversion of the display data is performed so as to convert the display data for each of the plurality of set fields.
In the preferred method for driving a display device according to the first aspect of the invention described above, the plurality of fields is set in such a manner that they (i.e., the plurality of fields) correspond to the respective light emission time periods of the plurality of light beams and further that they (i.e., the plurality of fields) follow one after another in a successive manner on a time axis That is, the length of a time period of each of the plurality of fields and/or the starting point in time thereof (and/or other similar time-related factor(s)) is set in association with the corresponding one of the light emission time periods of the plurality of light beams. Therefore, it is possible to convert the display data for each of the plurality of fields and then supply the converted data to the pixel units in a field-sequential manner. Therefore, it is possible to display, with increased reliability, images having actual brightness and/or color close to desired brightness and/or color at the display area of a display device.
It is preferable that the method for driving a display device according to the first aspect of the invention described above should further include: setting the plurality of fields in accordance with the display data so as to achieve an actual value that is close to a desired value for at least either one of brightness and color obtained when an image is displayed in the display area, wherein the above-mentioned conversion of the display data is performed so as to convert the display data for each of the plurality of set fields.
In the preferred method for driving a display device according to the first aspect of the invention described above, the plurality of fields is set in accordance with the display data so as to achieve an actual value that is close to a desired value for at least either one of brightness and color obtained when an image is displayed in the display area. That is, the plurality of fields is set in accordance with the display data so that data conversion can be performed for each of the plurality of fields in a more desirable manner. As a typical operation thereof, either the length of a time period of each of the plurality of fields or the starting point in time thereof is variably set on a real time basis, which is dependent on the display data. By this means, it is possible to perform the conversion of the display data in a more desirable manner. Therefore, it is possible to display images having actual brightness and/or color further closer to desired brightness and/or color at the display area of a display device.
In the method for driving a display device according to the first aspect of the invention described above, it is preferable that the plurality of pixel units should contain, without any limitation thereto, liquid crystal; and the plurality of fields should be determined on the basis of the response time of the liquid crystal.
In the preferred method for driving a display device according to the first aspect of the invention described above, the plurality of pixel units contains, without any limitation thereto, liquid crystal. In a case where the pixel units contain liquid crystal, it takes some time from a point in time at which display data is supplied to the pixel units to a point in time at which an image is displayed (i.e., display becomes available) on the basis of the supplied display data. That is, liquid crystal requires some time for transition into an image-display state. In the description of this specification as well as in the recitation of appended claim, the liquid crystal state transition time period from the supplying of display data to the displaying of an image is referred to as the “response time” thereof.
In the preferred method for driving a display device according to the first aspect of the invention described above, the plurality of fields is determined on the basis of the response time of the liquid crystal. That is, the length of a time period of each of the plurality of fields and/or the starting point in time thereof (and/or other similar time-related factor(s)) differs/changes depending on the response time of the liquid crystal. Therefore, it is possible to convert the display data and supply the converted display data on the basis of the response time of the liquid crystal. Note that the response time of the liquid crystal is unique to each individual display device. That is, the response time of the liquid crystal is a known value as long as the display device is known. Therefore, it is possible to preset the plurality of fields (e.g., the length of a time period of each of the plurality of fields and/or the starting point in time thereof) on the basis thereof.
Since it is possible to convert the display data and to supply the converted display data on the basis of (i.e., in accordance with) the response time of the liquid crystal, it is further possible to avoid low brightness because of the delayed response of the liquid crystal. In addition, because it is possible to convert the display data and to supply the converted display data in accordance with (i.e., on the basis of) the response time of the liquid crystal, it is further possible to avoid failure in representing a correct color (e.g., color tone or hue). Therefore, it is possible to display, in a more preferable manner, images having actual brightness and/or color close to desired brightness and/or color at the display area of a display device.
In the method for driving a display device according to the first aspect of the invention described above, it is preferable that the plurality of pixel units should contain, without any limitation thereto, liquid crystal; and the conversion rule should be set on the basis of the response time of the liquid crystal.
In the preferred method for driving a display device according to the first aspect of the invention described above, the plurality of pixel units contains, without any limitation thereto, liquid crystal. Therefore, as has already been explained above, it takes some time from a point in time at which display data is supplied to the pixel units to a point in time at which an image is displayed on the basis of the supplied display data. That is, liquid crystal requires the above-defined response time for transition into an image-display state.
In the preferred method for driving a display device according to the first aspect of the invention described above, the conversion rule is set on the basis of the response time of the liquid crystal. That is, the conversion rule is set in accordance with the response time of the liquid crystal so as to realize more preferable data conversion. Since it is possible to convert the display data on the basis of (i.e., in accordance with) the response time of the liquid crystal, it is further possible to avoid low brightness because of the delayed response of the liquid crystal. In addition, because it is possible to convert the display data in accordance with (i.e., on the basis of) the response time of the liquid crystal, it is further possible to avoid failure in representing a correct color. Therefore, it is possible to display, in a more preferable manner, images having actual brightness and/or color close to desired brightness and/or color at the display area of a display device.
In the method for driving a display device according to the first aspect of the invention described above, it is preferable that the plurality of pixel units should contain, without any limitation thereto, liquid crystal; and the liquid crystal should be twisted nematic liquid crystal.
In the preferred method for driving a display device according to the first aspect of the invention described above, the pixel units of the display area contain, without any limitation thereto, twisted nematic liquid crystal, which may be hereafter referred to as “TN liquid crystal”. Generally speaking, the response time of TN liquid crystal is longer than that of VA (Vertical Alignment) liquid crystal or IPS (In-Place Switching, or In-Plane Switching) liquid crystal, though not limited thereto.
As explained above, in the preferred method for driving a display device according to the first aspect of the invention, display data is converted for each of a plurality of fields; and therefore, it is possible to display images having actual brightness and/or color close to desired brightness and/or color at the display area of a display device. More specifically, it is possible to avoid low brightness because of the delayed response of the liquid crystal. In addition, it is further possible to avoid failure in representing a correct color. The advantageous effects of the method for driving a display device according to the first aspect of the invention described above are more remarkable if the response time of the liquid crystal is longer.
In this respect, in the preferred method for driving a display device according to the first aspect of the invention described above, the pixel units of the display area contain, without any limitation thereto, the TN liquid crystal, which means that the liquid crystal response time thereof is relatively long. Therefore, the advantageous effects of the preferred method for driving a display device according to the first aspect of the invention described above are more remarkable because the response time of the TN liquid crystal is relatively long. That is, the preferred method for driving a display device according to the first aspect of the invention described above makes it possible to display images having actual brightness and/or color close to desired brightness and/or color at the display area of a display device with more remarkable effects.
In a case where a driving frequency is heightened by means of the VA liquid crystal or by means of the IPS liquid crystal, the response of the liquid crystal is relatively slow even with the use of such liquid crystal. Therefore, the preferred method for driving a display device according to the first aspect of the invention described above produces very advantageous effects.
In the method for driving a display device according to the first aspect of the invention described above, it is preferable that the plurality of fields should be determined depending on the respective positions of the pixel units of (i.e., in) the display area.
In the preferred method for driving a display device according to the first aspect of the invention described above, the plurality of fields is determined depending on the respective positions of the pixel units of the display area. Therefore, the length of a time period of each of the plurality of fields and/or the starting point in time thereof differs/changes depending on the respective positions of the pixel units of the display area. Herein, it should be noted that the meaning of “the respective positions of the pixel units” is not limited to the respective positions of the pixels (i.e., single pixel). For example, “the respective positions of the pixel units” encompasses the meaning of the respective positions of pixel blocks each of which is made up of a plurality of pixels. Or, as another non-limiting example, “the respective positions of the pixel units” may be the respective positions of pixel rows each of which is made up of a plurality of pixels or the respective positions of pixel columns each of which is made up of a plurality of pixels. Regardless of whether the field is determined depending on the position of a single pixel, a pixel block that is made up of a plurality of pixels, a pixel row that is made up of a plurality of pixels, or a pixel column that is made up of a plurality of pixels, the length of a time period of each of the plurality of fields and/or the starting point in time thereof that is suitable for the corresponding position of the pixel unit is a known value as long as the display device is known. Therefore, it is possible to preset the plurality of fields (e.g., the length of a time period of each of the plurality of fields and/or the starting point in time thereof) on the basis thereof. As a typical non-limiting example of field determination, the length of a time period of each of the plurality of fields and/or the starting point in time thereof corresponds to the sequential order of scanning operation that is performed in a display area. For example, in a case where display data is supplied through vertical-scan operation, the lengths of time periods of the plurality of fields and/or the starting points in time thereof differ/vary from one another depending on respective vertical positions on the display area.
In the preferred method for driving a display device according to the first aspect of the invention described above, the plurality of fields is determined depending on the respective positions of the pixel units of the display area as has already been explained above. Therefore, for example, in a case where the pixel units are subjected to sequential scanning operation for image display, it is possible to perform such data conversion that makes it possible to correct a shift in the timing of display-data supply that is attributable to a difference in the respective positions of the pixel units of the display area. Therefore, it is possible to display, in a more preferable manner, images having actual brightness and/or color close to desired brightness and/or color at the display area of a display device.
In the method for driving a display device according to the first aspect of the invention described above, it is preferable that the conversion rules should be set depending on the respective positions of the pixel units of (i.e., in) the display area.
In the preferred method for driving a display device according to the first aspect of the invention described above, since the conversion rules are set depending on the respective positions of the pixel units of the display area, display data is converted by means of, that is, on the basis of different (sets of) conversion rules that depend on the respective positions of the pixel units of the display area. In the preferred method for driving a display device according to the first aspect of the invention described above, the conversion rules are set depending on the respective positions of the pixel units of the display area as has already been explained above. Therefore, for example, in a case where the pixel units are subjected to sequential scanning operation for image display, it is possible to perform such data conversion that makes it possible to correct a shift in the timing of display-data supply that is attributable to a difference in the respective positions of the pixel units of the display area. Therefore, it is possible to display, in a more preferable manner, images having actual brightness and/or color close to desired brightness and/or color at the display area of a display device.
In the method for driving a display device according to the first aspect of the invention described above, it is preferable that each of the light emission time periods of the plurality of light beams should be shorter than the corresponding one of the plurality of fields.
In the preferred method for driving a display device according to the first aspect of the invention described above, each of the light-emitting time periods of the plurality of light beams is shorter than the corresponding one of the plurality of fields, which means that each of the plurality of fields has a non-light-emitting time period other than the corresponding light-emitting time period. No light is irradiated during the non-light-emitting time period. As a typical non-limiting example of field determination, the ending position (e.g., ending point in time, though not limited thereto) of each light emission time period is synchronized with the ending position (e.g., ending point in time, though not limited thereto) of the corresponding field.
The display contribution ratio of each non-light-emitting time period, which is the percentage of contribution to image display attributable to each non-irradiation time period, is relatively small in comparison with that of the corresponding light-emitting time period. That is, the contribution of each non-light-emitting time period to the brightness of a display image or the color thereof is comparatively small percentage-wise. Or, in other words, overall display performance will be high as long as transmission performance during each light-emitting time period is high regardless of whether transmission performance during each non-light-emitting time period is high or not. Therefore, for example, in a case where the pixel units contain liquid crystal, it is possible to put the liquid crystal in a fully responsive state prior to the start of the target light-emission time period if the liquid crystal is “pre-driven” during other time period. Therefore, it is possible to display, in a more preferable manner, images having actual brightness and/or color close to desired brightness and/or color at the display area of a display device.
As explained above, in the preferred method for driving a display device according to the first aspect of the invention, each of the light-emitting time periods of the plurality of light beams is shorter than the corresponding one of the plurality of fields, which means that each of the plurality of fields has a non-light-emitting time period other than the corresponding light-emitting time period; and therefore, it is possible to display, in a more preferable manner, images having actual brightness and/or color close to desired brightness and/or color at the display area of a display device.
It is preferable that the method for driving a display device according to the first aspect of the invention described above should further include: temporarily storing the converted display data, wherein the above-mentioned supplying of the converted display data is performed (i.e., the converted display data is supplied) in such a manner that the temporarily stored display data is read out and then supplied to the pixel units in a sequential manner.
In the preferred method for driving a display device according to the first aspect of the invention described above, the display data that has been subjected to conversion on the basis of the predetermined conversion rule is temporarily stored. That is, the converted display data is temporarily stored into a memory device such as a frame buffer memory without any limitation thereto. Thereafter, the display data is read out of the memory and then send to the pixel units. The frame buffer memory can store the display data for each single frame or each set of plural frames. Note that it is not necessary for all of the converted display data to be stored into the memory. That is, some of the converted display data may be directly supplied to the pixel units without being temporarily stored into the memory whereas other converted display data is temporarily stored into the memory.
In the preferred method for driving a display device according to the first aspect of the invention described above, the converted display data is temporarily stored into the memory; and therefore, it is possible to supply the readout display data to the pixel units in a sequential manner at timing corresponding to, for example, the respective light emission time periods of the plurality of light beams. That is, it is possible to supply the display data to the pixel units at a desired timing. Therefore, it is possible to display, in a more preferable manner, images having actual brightness and/or color close to desired brightness and/or color at the display area of a display device.
In order to address the above-identified problem without any limitation thereto, the invention provides, as a second aspect thereof, a circuit for driving a display device, the driving circuit including: a light irradiating section that emits a plurality of light beams toward a display area in a time-divided manner, each of the plurality of light beams having an individual and/or own color that differs from those of others, the display area having a plurality of pixel units; a data converting section that converts display data that is to be supplied to the plurality of pixel units on the basis of at least one predetermined conversion rule for each of a plurality of fields, the plurality of fields being determined so as to correspond to respective light emission time periods of the plurality of light beams, the plurality of fields following one after another in a successive manner on a time axis, the predetermined conversion rule having been prepared so as to achieve an actual value that is close to a desired value for at least either one of brightness and color obtained when an image is displayed in the display area; and a data supplying section that supplies the converted display data to the plurality of pixel units in a sequential manner for each of the plurality of fields.
With such a configuration of a circuit for driving a display device according to the second aspect of the invention, it is possible to produce the same advantageous effects as those offered by the method for driving a display device according to the first aspect of the invention explained above. That is, in the configuration of a driving circuit according to the second aspect of the invention described above, display data is converted for each of a plurality of fields; and therefore, it is possible to display images having actual brightness and/or color close to desired brightness and/or color at the display area of a display device.
Any of the preferred modes of the invention described above, which add restrictive features to the fundamental features of the driving method according to the first aspect of the invention, may be applied to the driving circuit according to the second aspect of the invention. If so applied, the driving circuit according to the second aspect of the invention that features any of the preferred modes of the invention offers the same operation/working effects as those of the preferred method for driving a display device according to the first aspect of the invention explained above.
In order to address the above-identified problem without any limitation thereto, the invention provides, as a third aspect thereof, an electro-optical device that is provided with the circuit for driving a display device according to the second aspect of the invention.
Since an electro-optical device according to the third aspect of the invention is provided with the circuit for driving a display device according to the second aspect of the invention described above, it is possible to display images having actual brightness and/or color close to desired brightness and/or color at the display area of a display device.
In order to address the above-identified problem without any limitation thereto, the invention provides, as a fourth aspect thereof, an electronic apparatus that is provided with the electro-optical device according to the third aspect of the invention.
According to an electronic apparatus of this aspect of the invention, it is possible to embody various kinds of electronic devices that are capable of displaying images having actual brightness and/or color close to desired brightness and/or color at the display area of a display device, including but not limited to, a projection-type display device, a television, a mobile phone, an electronic personal organizer, a word processor, a viewfinder-type video tape recorder, a direct-monitor-view-type video tape recorder, a workstation, a videophone, a POS terminal, a touch-panel device, and so forth, because the electronic apparatus of this aspect of the invention is provided with the electro-optical device according to the above-described aspect of the invention. In addition, as another non-limiting application example thereof, an electronic apparatus of this aspect of the invention may be also embodied as an electrophoresis apparatus such as a sheet of electronic paper.
These and other features, operations, and advantages of the present invention will be fully understood by referring to the following detailed description of exemplary embodiments in conjunction with the accompanying drawings.
The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements.
With reference to the accompanying drawings, exemplary embodiments of the present invention are described below.
Driving Method and Driving Circuit
In the following description, a method/circuit for driving a display device according to an exemplary embodiment of the invention is explained while referring to
First of all, an example of the configuration of a driving circuit according to an exemplary embodiment of the invention is explained with reference to
As illustrated in
The light source is made up of, for example, a plurality of light-emitting diodes (LED). The plurality of light-emitting diodes emits light corresponding to three primary color components, that is, red (R), green (G), and blue (B). Each of the plurality of light-emitting diodes emits light of the corresponding primary color component at a periodic interval in such a manner that their light-emitting time periods do not overlap one another. Thus, there occurs no time conflict during the light-emitting operation thereof. Each of red, green, and blue light emitted from the corresponding one of the plurality of light-emitting diodes enters a color-combining optical unit such as a color-combination prism or the like as an incident light beam. As a result of combination thereof, a “combined” light beam is emitted from the color-combining unit toward a liquid crystal panel 200 illustrated in
The conversion unit 120 is provided with an arithmetic circuit and a memory circuit/device, though not limited thereto. Having such data-converting circuitry, the conversion unit 120 converts input display data (i.e., “to-be-displayed” data), which corresponds to each of three primary color components of R, G, and B, on the basis of a predetermined conversion rule. Then, the conversion unit 120 outputs the converted display data to the controller 130. Specifically, in the configuration of a driving circuit according to the present embodiment of the invention, the conversion unit 120 has at least one conversion table 120a. The conversion table(s) 120a stored in the conversion unit 120 was prepared in accordance with a predetermined conversion rule(s).
The controller 130 is provided with, for example, a logical operation circuit such as a CPU (Central Processing Unit), without any limitation thereto. The controller 130 temporarily stores the converted display data that is supplied from the conversion unit 120 into the frame memory 140. Then, the controller 130 reads the stored display data out of the frame memory 140 in a sequential manner so as to supply the readout display data to the liquid crystal panel 200. While outputting the readout display data to the liquid crystal panel 200, the controller 130 outputs a light-emission timing control signal to the light source 110. In addition to the functional operation described above, the controller 130 may control the entire operation of a driving circuit according to the present embodiment of the invention. The controller 130 may further control the entire operation of a display device. In the foregoing description of an exemplary configuration of a driving circuit according to the present embodiment of the invention, the conversion unit 120 and the controller 130 are provided as discrete units, which are separated from each other. However, the scope of the invention is not limited to such an exemplary configuration. As a non-limiting modification example thereof, the controller 130 may include the conversion unit 120 so that the conversion unit 120 functions as an internal component unit of the controller 130.
Next, a method for driving a display device according to an exemplary embodiment of the invention is explained while referring to
In the comparative-example graph of
However, as shown by a solid line in the comparative-example graph of
The number of the conversion table 120a may not be one. That is, if it is possible to represent (i.e., display) the same/similar color tone by means of a plurality of (sets of) conversion rules that differ from each other or one another, not a single but plural conversion tables 120a may be set so as to correspond to the plural (sets of) conversion rules. In such a case, the plural conversion tables 120a can be selectively used. The plurality of conversion tables may be set so as to correspond to more than one position on the liquid crystal panel 200. More detailed explanation thereof will be given later.
The conversion unit 120 converts the display data as explained above. As a result thereof, in the specific example of the present embodiment of the invention, the panel transmission factor for the first field is set at a value of 10. The panel transmission factor for the second field is set at a value of 255. The panel transmission factor for the third field is set at a value of 0. Although the first field according to an exemplary embodiment of the invention corresponds to the R field of the comparative example explained above, the technical property thereof differs from each other. In like manner, although the second and third fields according to an exemplary embodiment of the invention correspond to the G and B fields of the comparative example explained above, respectively, the technical nature thereof differs from each other. The R field of the comparative example is dedicated to the display of the red color component. The G and B fields of the comparative example are dedicated to the display of the green and blue color components, respectively. In contrast, each of the first, second, and third fields according to an exemplary embodiment of the invention is not dedicated to the display of only one of these three primary color components. That is, each of the first, second, and third fields according to an exemplary embodiment of the invention could contribute to the display of any one or more of R, G, and B. For example, the control of liquid crystal that is performed in the first field, which includes an R light emission time period (i.e., light-emitting time period), could contribute to the display of the green color component. The length of the time period of each field and/or the starting position (e.g., starting point in time, though not limited thereto) thereof may be determined (e.g., predetermined, without any limitation thereto) on the basis of, for example, the response time of liquid crystal or other alternative time-dependent factor(s). Or, alternatively, the length of the time period of each field and/or the starting position thereof may be variably determined on a real time basis, which is dependent on, for example, display data that is supplied thereto.
Referring back to
As shown in
If the configuration of a driving circuit according to the present embodiment of the invention (a method for driving a display device according to the present embodiment of the invention) is adopted, the liquid crystal panel 200 “undesirably” transmits some amount of R light, though it is not so large, because the panel transmission factor is raised not only in the second field that corresponds to the G light emission time period but also in the first field that corresponds to the R light emission time period. Since the R light, which is not the transmission target G light (that is to be displayed) according to the specific example described herein, is also transmitted (i.e., also passes) through the liquid crystal panel 200, a color-mixture phenomenon occurs in a theoretical sense and in an exact sense. Despite the fact that a color-mixture phenomenon occurs in a theoretical sense and in an exact sense due to the transmission of the non-target R light through the liquid crystal panel 200, a user perceives almost no adverse effects of the mixture of R and G when viewed with the naked eye in actual and practical implementation of the invention. This is because the panel transmission factor for the target G light drastically improves as explained above. In addition, it is possible to reduce the adverse effects of the mixture of R and G if the conversion table 120a stored in the conversion unit 120 is prepared so as to effectively mitigate the adverse effects of the color-mixture phenomenon, which ensures further enhanced display performance.
Next, an example of liquid crystal control that is performed at the time of yellow (Y) display is explained below. Note that yellow (Y) is an intermediate color, that is, the color between R and G.
In the comparative-example graph of
However, as shown by a solid line in the comparative-example graph of
If the configuration of a driving circuit according to the present embodiment of the invention (a method for driving a display device according to the present embodiment of the invention) is adopted, the liquid crystal panel 200 transmits some amount of B light, which does not contribute to yellow display at all. This is because the panel transmission factor is raised not only in the first and second fields that respectively correspond to the R and G light emission time periods but also in the third field that corresponds to the B light emission time period. Since the B light, which is not used for yellow display at all, also passes through the liquid crystal panel 200, a color-mixture phenomenon occurs in a theoretical sense and in an exact sense. Despite the fact that a color-mixture phenomenon occurs in a theoretical sense and in an exact sense due to the transmission of the non-contributing B light through the liquid crystal panel 200, a user perceives almost no adverse effects of the mixture thereof when viewed with the naked eye in actual and practical implementation of the invention. This is because the panel transmission factors for the R and G light are improved as explained above. Thus, the driving method (driving circuit) according to the present embodiment of the invention makes it possible to increase the brightness/luminance of images displayed on the liquid crystal panel 200. In addition thereto, the driving method (driving circuit) according to the present embodiment of the invention makes it further possible to achieve an adequate color balance when displaying any immediate color so as to represent the correct color tone thereof.
In the foregoing description of a driving method/circuit according to exemplary embodiments of the invention, it is assumed that liquid crystal control is performed with the supplying of display data at the end of each light emission time period. Notwithstanding the foregoing, however, the timing of display-data supply may be shifted from the end of each light emission time period. For example, in a case where display data is supplied through vertical-scan operation, points in time at which the display data is supplied differ/vary from one another depending on respective vertical positions on the liquid crystal panel 200. In the following description, a modified driving method/circuit according to an exemplary embodiment of the invention that takes a difference in positions on the liquid crystal panel 200 into consideration is explained, taking an example of liquid crystal control that is performed around the center of the liquid crystal panel 200 under the assumption of vertical-scan operation.
When display data is supplied through vertical-scan operation, scanning is performed from the top of the liquid crystal panel 200 toward the bottom thereof in a sequential manner. For this reason, the timing of display-data supply at a certain lower position on the liquid crystal panel 200 is later (in point in time) than the timing of display-data supply at a certain upper position on the liquid crystal panel 200. For example, display data is supplied at the end of each light emission time period at/for the uppermost region (e.g., line) of the liquid crystal panel 200 at which scanning is performed at the earliest point in time (refer to
In the comparative-example graph of
In the foregoing description of the position-based liquid crystal control (i.e., position-based driving method) that uses different (sets of) conversion rules dependent on positions (e.g., scan positions, though not limited thereto) on the liquid crystal panel 200, it is assumed that non-intermediate green display is performed. However, the technical scope of a driving method/circuit according to the present embodiment of the invention is not limited to such a specific example. For example, the same advantageous effects as those offered by a driving method/circuit according to the present embodiment of the invention described above can be obtained when it is applied to the display of any intermediate color such as Y explained above. Thus, the driving method/circuit according to the present embodiment of the invention makes it possible to increase the brightness/luminance of images displayed on the liquid crystal panel 200. In addition thereto, the driving method/circuit according to the present embodiment of the invention makes it further possible to achieve an adequate color balance when displaying any immediate color so as to represent the correct color tone thereof.
The advantageous effects of a driving method/circuit according to an exemplary embodiment of the invention are produced as a result of the setting of a plurality of fields such as the first, second, and third fields explained above, though not limited thereto, and further as a result of the conversion/supply of display data on a field-by-field basis. However, the minimum unit of a time period for sequential operation of a driving method/circuit according to an exemplary embodiment of the invention is not limited to the field explained above. For example, each of the fields may be sub-divided into shorter unit time periods so as to obtain greater advantages of an aspect of the invention. As a non-limiting modification example thereof, each of the fields may be split into a first sub field that does not overlap the corresponding light emission time period and a second sub field that overlaps the corresponding light emission time period. Display data is supplied for each sub-field, that is, on a subfield-by-subfield basis. By this means, it is possible to further enhance the brightness/luminance of images displayed on the liquid crystal panel 200. More specifically, display data is supplied to a plurality of pixel units (e.g., pixel portions, pixel regions, pixel areas, or pixels, though not limited thereto) of the liquid crystal panel 200 every other line in a concurrent manner (i.e., at the same time) in each first sub-field. On the other hand, the display data is supplied to the remaining pixel units of the liquid crystal panel 200 on a line-by-line basis in a non-concurrent manner in each second sub-field. In such a modified driving operation/configuration, the display data is supplied to the pixel units of the liquid crystal panel 200 on a plurality of rows in a concurrent manner, which requires shorter time for the supplying of the display data in comparison with a case where the display data is supplied to the pixel units of the liquid crystal panel 200 on a line-by-line basis in a non-concurrent manner. Therefore, it is possible to make the length of the time period of each second sub-field relatively long, which means that the length of the time period during which light is emitted/irradiated is made relatively long, thereby making it further possible to display images with higher brightness/luminance.
As explained above, the driving method/circuit according to the present embodiment of the invention makes it possible to increase the brightness/luminance of images displayed on the liquid crystal panel 200. In addition thereto, the driving method/circuit according to the present embodiment of the invention makes it further possible to achieve an adequate color balance, for example, when displaying any immediate color, so as to represent the correct color tone thereof.
Electro-Optical Device
Next, with reference to
As shown in
The sealant material 52 is made from, for example, an ultraviolet (UV) curable resin, a thermosetting resin, or the like, which functions to paste these substrates together. In the production process of the liquid crystal device according to the present embodiment of the invention, the sealant material 52 is applied onto the TFT array substrate 10 and subsequently hardened through an ultraviolet irradiation treatment, a heat treatment, or any other appropriate treatment. A gap material such as glass fibers, glass beads, or the like, are scattered in the sealant material 52 so as to set the distance (i.e., inter-substrate gap) between the TFT array substrate 10 and the counter substrate 20 at a predetermined gap value.
Inside the sealing area at which the sealant material 52 is provided, and in parallel therewith, a picture frame light-shielding film 53, which has a light-shielding property and defines the picture frame region of the image display area 10a, is provided on the counter substrate 20. Notwithstanding the above, however, a part or a whole of the picture frame light-shielding film 53 may be provided at the TFT-array-substrate (10) side as a built-in light-shielding film.
A data line driving circuit 101 and external circuit connection terminals 102 are provided at a certain peripheral region outside the sealing region at which the sealant material 52 is provided in such a manner that these data line driving circuit 101 and external circuit connection terminals 102 are provided along one of four sides of the TFT array substrate 10. A pair of scanning line driving circuits 104 is provided along two of four sides thereof that are not in parallel with the above-mentioned one side in such a manner that each of the scanning line driving circuits 104 is enclosed by the picture frame light-shielding film 53. In addition to the above, a plurality of electric wirings 105 is provided along the remaining one side of the TFT array substrate 10 that is parallel with the first-mentioned one side thereof. The plurality of electric wirings 105 connects one of the pair of the scanning line driving circuits 104 to the other thereof. The picture frame light-shielding film 53 encloses these electric wirings 105. The pair of the scanning line driving circuits 104 is provided outside the image display region 10a in such a manner that each of these scanning line driving circuits 104 extends along the corresponding one of the second-mentioned two sides thereof.
Inter-substrate conductive terminals 106, which connect the TFT array substrate 10 with the counter substrate 20 by means of inter-substrate conductive material 107, are provided on the TFT array substrate 10 at positions corresponding to four corners of the counter substrate 20, respectively. With such a structure, it is possible to establish electric conduction between the TFT array substrate 10 and the counter substrate 20.
As illustrated in
It should be noted that other functional circuits may also be provided on the TFT array substrate 10 illustrated in
Electronic Apparatus
Next, an explanation is given of an example of the applications of a liquid crystal device described above, which is a non-limiting example of an electro-optical device according to an aspect of the invention, to various kinds of electronic apparatuses.
As illustrated in
The configuration of the liquid crystal panel 200 is the same as or similar/equivalent to that of a liquid crystal device explained above. An image signal processor (e.g., processing circuit) that is not shown in the drawing supplies a driving signal to the liquid crystal panel 200. A light beam that has been subjected to optical modulation at the liquid crystal panel 200 is outputted through a projection lens 400. In this way, a color image is projected on a projection target medium such as a projection screen or the like.
As explained above, the projector 1100, which is a non-limiting application example of an electro-optical device according to an aspect of the invention, is provided with the light-emitting diodes 110R, 110G, and 110B as its internal light-source elements that correspond to three primary colors of R, G, and B, respectively. With such a configuration, it is not necessary to provide any color filter therein. Since it is not necessary to provide any color filter therein, it is possible to achieve cost reduction. In addition thereto, it is possible to achieve high brightness because light does not pass through any color filter.
Among a variety of electronic apparatuses to which the electro-optical device according to an aspect the invention could be embodied are, in addition to the electronic apparatus (projector) explained above with reference to
The present invention should be in no case interpreted to be limited to the specific embodiments described above. The invention may be modified, altered, changed, adapted, and/or improved within a range not departing from the gist and/or spirit of the invention apprehended by a person skilled in the art from explicit and implicit description given herein as well as recitation of appended claims. A method for driving a display device subjected to such modification, alteration, change, adaptation, and/or improvement, a circuit for driving (or a driving circuit of) a display device subjected thereto, an electro-optical device employing such a driving method or having such a driving circuit subjected thereto, and an electronic apparatus that is provided with such an electro-optical device, are also within the technical scope of the invention.
The entire disclosure of Japanese Patent Application No. 2007-246688, filed Sep. 25, 2007 is expressly incorporated by reference herein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2007-246688 | Sep 2007 | JP | national |
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