WO2019004072A1

WO2019004072A1 - Field-sequential image display apparatus and image display method

Info

Publication number: WO2019004072A1
Application number: PCT/JP2018/023769
Authority: WO
Inventors: 正益小林
Original assignee: シャープ株式会社
Priority date: 2017-06-29
Filing date: 2018-06-22
Publication date: 2019-01-03

Abstract

The present invention provides a field-sequential image display apparatus that is capable of reducing saturation degradation or hue deviation caused by a mixed color even when a display device having a fast optical response is not used. In the field-sequential image display apparatus in which each frame period includes sub-frame periods of green, red, white, and blue: the allocation ratio to the white sub-frame period is set as 50% and input image data of red, green, and blue is converted into driving image data of red, green, blue, and white; and a liquid crystal panel is driven on the basis of the driving image data. A backlight is driven so that light sources (G-LED) and (R-LED) are both lit only in the latter halves of the green and red sub-frame periods (Tg, Tr), that, in the white sub-frame period (Tw), the light source (R-LED) corresponding to an immediately-preceding sub-frame period is lit in the first/latter half and (G-LED) and (B-LED) are lit only in the latter half, and that (B-LED) is lit in first/latter half of the blue sub-frame period (Tb) immediately after.

Description

Field sequential type image display apparatus and image display method

The present invention relates to an image display apparatus, and more particularly, to a field sequential image display apparatus and an image display method.

2. Description of the Related Art Conventionally, there has been known a field sequential image display apparatus that displays a plurality of subframes in one frame period. For example, a typical field sequential image display apparatus includes backlights including red, green and blue light sources, and displays red, green and blue subframes in one frame period. When displaying a red sub-frame, the display panel is driven based on red image data, and a red light source emits light. Subsequently, the green and blue subframes are displayed in a similar manner. The three subframes displayed in time division are synthesized by the afterimage phenomenon on the retina of the observer and are recognized as one color image by the observer.

In the field sequential image display apparatus, when the line of sight of the observer moves in the display screen, the color of each subframe may be seen separately by the observer (this phenomenon is called "color breakup". ). Therefore, there is known an image display device that displays white subframes in addition to red, green, and blue subframes in order to suppress color breakup.

In each sub-frame period, when the light source of the color corresponding to the sub-frame period starts lighting before the writing of the pixel data representing the image to be displayed to the display device (for example, liquid crystal panel) is completed, the next sub A color corresponding to the frame period will be mixed in the display image (hereinafter, this phenomenon is referred to as “mixed color due to pixel data write timing”). When a display device with a slow optical response is used as in a liquid crystal display device, lighting of a light source of a color corresponding to the subframe period is started until the response is completed in each subframe period. The color corresponding to the next sub-frame period will be mixed in the display image (hereinafter, this phenomenon is referred to as “color mixing due to optical response”). In this way, when the corresponding colors are mixed in the subframe periods adjacent to each other, the saturation falls or the hue shifts in the display image.

In relation to the present invention, Patent Document 1 describes that in a time division color display device (field sequential type image display device), an image signal is written from the upper part of the screen by line sequential writing to a liquid crystal panel. A driving method is described in which the light source corresponding to the color of the written image signal is turned on after blanking for the response time of the liquid crystal after writing up to the point (see paragraph [0060] of the same document, FIG. 8). .

Japanese Patent Application Laid-Open No. 2002-191055

In the above time-division color display device (hereinafter referred to as "image display device of Patent Document 1") described in Patent Document 1, writing of pixel data and the corresponding liquid crystal panel are performed in each subfield period (each subframe period). After the response is completed, the lighting of the light source of the color corresponding to the sub-field period (the sub-frame period) is started, so that the reduction in saturation and the hue shift in the display image are improved.

However, even in the image display device of Patent Document 1, color mixing due to the optical response may not be avoided depending on the response characteristic of the display device (liquid crystal panel). Further, in the image display device of Patent Document 1, since a period which can be used for writing pixel data in a sub-frame period is short, a configuration for writing pixel data at high speed is required.

Therefore, it is possible to provide a field sequential type image display device capable of suppressing saturation reduction and hue shift due to color mixing even when the display device with fast optical response is not used and the configuration without the configuration for writing pixel data at high speed is not provided. It is desired.

According to some embodiments of the present invention, field sequential image display in which each frame period includes a plurality of subframe periods each including a plurality of primary color subframe periods corresponding to a plurality of primary colors and a common color subframe period. A device,
A light source unit including a plurality of light sources emitting light in the plurality of primary colors;
A light modulation unit that transmits or reflects light from the light source unit;
A light source unit driving circuit for driving the light source unit such that light of a corresponding color is emitted to the light modulation unit in each subframe period;
A light modulation unit driving circuit for controlling the transmittance or the reflectance of the light modulation unit so that an image of a corresponding color is displayed in each subframe period;
The light source unit drive circuit is configured to start lighting the light source of the first primary color corresponding to the preceding subframe period which is the immediately preceding subframe period in the common color subframe period from the start point of the common color subframe period And the time from the start of the subsequent subframe period which is a subframe period immediately after the common color subframe period to the time when the light source of the corresponding second primary color starts lighting in the subsequent subframe period Of at least one of the plurality of primary colors from a start point of a primary color sub-frame period corresponding to another primary color other than the first and second primary colors to a time point when the light source starts lighting in the primary color The light source unit is driven to be shorter than time.

Preferred configurations of the above embodiments receive substantially the input light data corresponding to a plurality of primary colors, and substantially change in transmittance or reflectance in the light modulation section when switching from the preceding subframe period to the common color subframe period. From the input image data so that the transmittance or the reflectance in the light modulation section does not substantially change or increase when switching from the common color subframe period to the subsequent subframe period. The light modulation unit driving circuit further displays an image of a corresponding color in each subframe period based on the driving image data. Control the transmittance or reflectance of the light modulation unit.

Another embodiment of the present invention is an image display device including a light source unit including a plurality of light sources emitting light of a plurality of primary colors, and a light modulation unit transmitting or reflecting light from the light source unit. An image display method for displaying a color image according to a field sequential method in which each frame period includes a plurality of sub-frame periods consisting of a plurality of primary color sub-frame periods and a common color sub-frame period respectively corresponding to the plurality of primary colors. ,
A light source unit driving step of driving the light source unit such that light of a corresponding color is irradiated to the light modulation unit in each subframe period;
And d) a light modulation unit driving step of controlling the transmittance or reflectance of the light modulation unit so that an image of a corresponding color is displayed in each subframe period.
In the light source unit driving step, when the light source of the first primary color corresponding to the preceding subframe period which is the immediately preceding subframe period in the common color subframe period from the start point of the common color subframe period starts lighting And the time from the start of the subsequent subframe period which is a subframe period immediately after the common color subframe period to the time when the light source of the corresponding second primary color starts lighting in the subsequent subframe period Of at least one of the plurality of primary colors from a start point of a primary color sub-frame period corresponding to another primary color other than the first and second primary colors to a time point when the light source starts lighting in the primary color The light source unit is driven to be shorter than time.

According to the above embodiments of the present invention, lighting of the light source of the first primary color corresponding to the preceding subframe period (the primary color subframe period immediately before the common color subframe period) from the start of the common color subframe period The time from the start time to the start time of the light source of the second primary color corresponding to the subsequent subframe period from the start of the subsequent subframe period (the primary color subframe period immediately after the common color subframe period) And at least one of a plurality of primary colors for image display from a start point of a primary color subframe period corresponding to another primary color other than the first and second primary colors to a lighting start time point of the light source in the primary color subframe period Less than time. As a result, in the field sequential type image display device, it is possible to improve the display luminance by reducing the time gap for light emission while suppressing the saturation decrease and the hue shift due to the delay of the optical response of the light modulation unit.

According to a preferable configuration of the above-described some embodiments of the present invention, when switching from the preceding subframe period to the common color subframe period, the response of the light modulation unit becomes a decay response. Even if the light source of the first primary color (the light source of the primary color corresponding to the preceding subframe period) is turned on, problems such as saturation reduction and hue shift do not occur. Also, when switching from the common color sub-frame period to the subsequent sub-frame period, the optical response of the light modulation unit becomes a rise response, so the light source of the second primary color in the subsequent sub-frame period Even if the light source of the primary color is turned on, color mixing does not occur. Therefore, the luminance of each color can be improved without causing problems such as saturation reduction and hue shift.

It is a block diagram showing composition of an image display device concerning a 1st embodiment. It is a figure for demonstrating the parameter in the image display apparatus which concerns on the said 1st Embodiment. It is a flowchart of the image data conversion process of the image display apparatus which concerns on the said 1st Embodiment. It is a figure which shows the range of the distribution ratio to the saturation and the white sub-frame in the image display apparatus which concerns on the said 1st Embodiment. It is a block diagram which shows the structure of the backlight drive circuit in the said 1st Embodiment. It is a timing chart for explaining the operation of the back light in the conventional image display device. It is a timing chart for demonstrating the operation | movement of the backlight in the said 1st Embodiment. A timing chart and waveform diagram (A) for explaining the operation of the image display apparatus as a first conventional example for comparison with the image display apparatus according to the first embodiment, and a diagram showing the lighting time of each light source B). They are a timing chart and waveform diagram (A) for demonstrating operation | movement of the image display apparatus which concerns on the said 1st Embodiment, and a figure (B) which shows the lighting time and light-emission quantity of each light source. It is a figure for demonstrating the display operation at the time of changing the color (target color) which should be displayed in the image display apparatus which concerns on the said 1st Embodiment. It is a figure which shows the graph of 1st distribution ratio WRs1 in the said 1st Embodiment. It is a figure for demonstrating the determination method of the function which calculates | requires 2nd distribution ratio WRsv2 in the image display apparatus which concerns on the said 1st Embodiment. It is a figure for demonstrating the compensation method of the shift | offset | difference of the color mixing hue in the said 1st Embodiment. Timing chart and waveform diagram (A) for explaining the operation of the image display apparatus as the second prior art for comparison with the image display apparatus according to the first modification of the first embodiment and lighting of each light source It is a figure (B) which shows time. They are a timing chart and waveform diagram (A) for demonstrating operation | movement of the image display apparatus which concerns on the 1st modification of the said 1st Embodiment, and a figure (B) which shows lighting time and light-emission quantity of each light source. Timing chart and waveform diagram (A) for explaining the operation of the image display apparatus as the third prior art for comparison with the image display apparatus according to the second modification of the first embodiment and lighting of each light source It is a figure (B) which shows time. They are a timing chart and waveform diagram (A) for demonstrating operation | movement of the image display apparatus which concerns on the 2nd modification of said 1st Embodiment, and a figure (B) which shows lighting time and light emission amount of each light source. A timing chart and a waveform diagram (A) for explaining the operation of the image display apparatus as a first conventional example for comparison with the image display apparatus according to the second embodiment and a diagram showing the lighting time of each light source (B ). They are a timing chart and waveform diagram (A) for demonstrating operation | movement of the image display apparatus which concerns on the said 2nd Embodiment, and a figure (B) which shows the lighting time and light-emission quantity of each light source. They are a timing chart and waveform diagram (A) for demonstrating operation | movement of the image display apparatus which concerns on the 1st modification of the said 2nd Embodiment, and a figure (B) which shows lighting time and light-emission quantity of each light source. They are a timing chart and waveform diagram (A) for demonstrating the operation | movement of the image display apparatus which concerns on the 2nd modification of the said 2nd Embodiment, and a figure (B) which shows lighting time and luminescence amount of each light source. A timing chart and a waveform diagram (A) for explaining the operation of the image display apparatus as the first conventional example for comparison with the image display apparatus according to the third embodiment and a diagram showing the lighting time of each light source (B ). They are a timing chart and waveform diagram (A) for demonstrating operation | movement of the image display apparatus which concerns on the said 3rd Embodiment, and a figure (B) which shows the lighting time and light-emission quantity of each light source. They are a timing chart and waveform diagram (A) for demonstrating the operation | movement of the image display apparatus which concerns on the 1st modification of the said 3rd Embodiment, and a figure (B) which shows lighting time and luminescence amount of each light source. A timing chart and a waveform diagram (A) for explaining the operation of the image display apparatus as a first conventional example for comparison with the image display apparatus according to the fourth embodiment and a diagram showing the lighting time of each light source (B ). They are a timing chart and waveform chart (A) for demonstrating operation | movement of the image display apparatus which concerns on the said 4th Embodiment, and a figure (B) which shows the lighting time and light-emission quantity of each light source. They are a timing chart and waveform diagram (A) for demonstrating operation | movement of the image display apparatus which concerns on the 1st modification of the said 4th Embodiment, and a figure (B) which shows lighting time and light-emission quantity of each light source. They are a timing chart and waveform chart (A) for demonstrating operation | movement of the image display apparatus which concerns on the 2nd modification of the said 4th Embodiment, and a figure (B) which shows the light source lighting time and light emission amount of each primary color. They are a timing chart and waveform diagram (A) for demonstrating operation | movement of the image display apparatus which concerns on the 3rd modification of the said 4th Embodiment, and a figure (B) which shows lighting time and light-emission quantity of each light source.

Hereinafter, an image display device and an image display method according to each embodiment will be described with reference to the drawings. In addition to "calculate the calculation result using an arithmetic unit" in "calculation" included in the following description, "calculate the calculation result in advance by storing the calculation result in a table, and draw the table." It is pointed out in advance that "to ask" is included.

<1. First embodiment>
<1.1 Overall Configuration>
FIG. 1 is a block diagram showing the configuration of the image display apparatus according to the first embodiment. The image display device 1 shown in FIG. 1 includes an image data conversion unit 10 and a display unit 20. The image data conversion unit 10 includes a parameter storage unit 11, a statistical value / saturation operation unit 12, a distribution ratio / coefficient operation unit 13, and a drive image data operation unit 33. The display unit 20 includes a liquid crystal panel 24 as a light modulation unit, a backlight 25 as a light source unit, a timing control circuit 21, a panel drive circuit 22 as a light modulation unit drive circuit, and a backlight drive as a light source unit drive circuit. A circuit 23 is included.

The image display device 1 is a field sequential liquid crystal display device. The image display device 1 divides one frame period into a plurality of subframe periods, and displays subframes of different colors in each subframe period. Hereinafter, the image display device 1 divides one frame period into four subframe periods, and displays green, red, white, and blue subframes respectively in the first to fourth subframe periods (see FIG. See FIG. 7 below). In the image display device 1, the white subframes become the common color subframes. The “color” in each sub-frame refers to the light source color, and the display unit 20 of the image display device 1 uses “red”, “green”, and “blue” as light source drive data for driving the backlight 25. It is assumed that "white" which is a desired color temperature can be displayed when 1 "(maximum value) is given (the same applies to other embodiments described later).

Input image data D1 including image data of red, green, and blue is input to the image display device 1. The image data conversion unit 10 obtains driving image data D2 corresponding to the green, red, white, and blue sub-frames based on the input image data D1. Hereinafter, this process is referred to as “image data conversion process”, and the drive image data D2 corresponding to the green, red, white, and blue sub-frames are “green, red, and so on included in the drive image data D2, respectively. It is called "white and blue image data". The display unit 20 displays green, red, white, and blue sub-frames in one frame period based on the driving image data D2.

The timing control circuit 21 outputs a timing control signal TC to the panel drive circuit 22 and the backlight drive circuit 23. The panel drive circuit 22 drives the liquid crystal panel 24 based on the timing control signal TC and the drive image data D2. The backlight drive circuit 23 drives the backlight 25 based on the timing control signal TC and a parameter WBR, which will be described later, from the parameter storage unit 11. The liquid crystal panel 24 includes a plurality of pixels 26 arranged in a two-dimensional manner. The backlight 25 includes a red light source 27r, a green light source 27g, and a blue light source 27b (in the following, these

light sources

27r, 27g, and 27b are also referred to as "three primary color light sources". It is also called "). The backlight 25 may include a white light source. For the light source 27, for example, an LED (Light Emitting Diode) is used.

In the first sub-frame period (hereinafter also referred to as “green sub-frame period Tg”), panel drive circuit 22 drives liquid crystal panel 24 based on green image data included in drive image data D2, and backlight drive circuit 23 The green light source 27g is made to emit light. Thus, the green sub-frame is displayed.

In the second sub-frame period (hereinafter also referred to as “red sub-frame period Tr”), panel drive circuit 22 drives liquid crystal panel 24 based on red image data included in drive image data D2, and backlight drive circuit 23 The red light source 27r is made to emit light. Thereby, a red sub-frame is displayed.

In the third sub-frame period (hereinafter also referred to as "white sub-frame period Tw"), panel drive circuit 22 drives liquid crystal panel 24 based on the white image data included in drive image data D2, and backlight drive circuit 23 The red light source 27r, the green light source 27g, and the blue light source 27b are made to emit light. Thereby, a white sub-frame is displayed. When the backlight 25 includes a white light source, the backlight drive circuit 23 may cause the white light source to emit light in the third subframe period.

In the fourth sub-frame period (hereinafter also referred to as “blue sub-frame period Tb”), panel drive circuit 22 drives liquid crystal panel 24 based on blue image data included in drive image data D2, and backlight drive circuit 23 The blue light source 27b is made to emit light. This causes blue sub-frames to be displayed.

<1.2 Details of Image Data Converter>
Hereinafter, the details of the image data conversion unit 10 will be described. The image data of red, green, and blue as primary color components included in the input image data D1 is luminance data normalized to a value of 0 or more and 1 or less. When the three color image data are equal, the pixel 26 is achromatic. The white, red, green, and blue image data included in the driving image data D2 are also luminance data normalized to a value of 0 or more and 1 or less. The image data conversion unit 10 uses, for example, a microcomputer (hereinafter abbreviated as a "microcomputer") including a CPU (central processing unit) and a memory, and the microcomputer executes a predetermined program corresponding to FIG. 3 described later. It can be realized by software. Instead of this, it is also possible to realize part or all of the image data conversion unit 10 as dedicated hardware (typically, an application specific integrated circuit designed specifically for exclusive use).

In the image data conversion process, the blue, green, and red values of each pixel of the image (input image) represented by the input image data D1 (hereinafter referred to as "the BGR pixel data value of the input image") are coefficients to be multiplied. While performing amplification compression processing using the adjustment coefficient Ks, the BGR pixel data values of the input image subjected to the amplification compression processing are pixel data values of white, red, green, and blue subframes (hereinafter referred to as “driving Color component conversion processing (hereinafter referred to as equations (5a) to (5d)). In this image data conversion process, white image data (values distributed to the common color sub-frames) included in the drive image data D2 is determined in the range of 0 or more and 1 or less. Further, in this image data conversion processing, for each pixel of the input image, a ratio of the display light amount to be emitted in the white subframe period Tw to the display light amount of the white component to be emitted in one frame period to display the pixel (“ The distribution ratio WRs of white subframes or “common color distribution ratio WRs” or simply “distribution ratio WRs” is determined first, and WGBR pixel data values for driving white image data etc. based on the distribution ratio WRs. Is required. For example, when the red image data contained in the input image data D1 is 0.5, and the green and blue image data is 1, the adjustment factor Ks is set to 1 and the distribution ratio WRs is set to 0.6. The white image data contained in the image data D2 is 0.3.

The parameter storage unit 11 stores parameters WRX, RA, RB, and WBR used in image data conversion processing. The statistical value / saturation calculation unit 12 obtains the maximum value Dmax, the minimum value Dmin, and the saturation S for each pixel based on the input image data D1. The distribution ratio / coefficient calculation unit 13 obtains the distribution ratio WRs and the adjustment coefficient (hereinafter, also simply referred to as “coefficient”) Ks based on the maximum value Dmax and the saturation S and the parameters WRX, RA, RB, WBR (Details Is mentioned later). The drive image data calculation unit 33 obtains the drive image data D2 based on the input image data D1, the minimum value Dmin, the distribution ratio WRs, the coefficient Ks, and the parameter WBR.

The parameters stored in the parameter storage unit 11 will be described below. The parameter WRX is a parameter according to the response characteristic of the pixel 26 included in the display unit 20. The parameter WRX is included in the formula for determining the distribution ratio WRs. The parameter WBR specifies the luminance of the light source 27 included in the backlight 25 when displaying a white subframe, and takes a value within the range of 0 ≦ WBR ≦ 1. In the present embodiment, according to the parameter WBR, the luminance of the light source 27 when displaying a white subframe is controlled to WBR times the luminance of the light source 27 when displaying another subframe. Therefore, the parameter WBR indicates the ratio of the luminance of each light source 27x in the white subframe period Tw as the common color subframe period to the luminance of the light source 27x in the subframe period Tx corresponding to the light source 27x (x = r , G, b).

The minimum value in one frame period of the driving image data D2 is DDmin, and the maximum value is DDmax. The distribution ratio / coefficient operation unit 13 obtains the coefficient Ks so as to satisfy the following equation (1) according to the parameters RA and RB stored in the parameter storage unit 11.
DDmax ≦ RA · DDmin + RB (1)
For example, in the case of RB = 1-RA, the range satisfying the equation (1) is the hatched portion shown in FIG. Thus, the parameters RA and RB designate the range of the maximum value DDmax according to the minimum value DDmin. As shown in the equation (1), one frame period is determined by determining the range of the maximum value in one frame period of the drive image data in accordance with the minimum value in one frame period of the drive image data. It is possible to suppress the change of the image data after conversion and improve the color reproducibility.

FIG. 3 is a flowchart of the image data conversion process. The process shown in FIG. 3 is performed on the data of each pixel included in the input image data D1. Hereinafter, the red, green and blue image data (BGR pixel data value of the input image) of a certain pixel included in the input image data D1 are respectively included in Ri, Gi, Bi, and the drive image data D2 Let Wd, Bd, Gd, and Rd be the white, blue, green, and red image data (WBGR pixel data values for driving), respectively, and the process for the three-color image data Ri, Gi, and Bi will be described.

As shown in FIG. 3, image data Ri, Gi, Bi of three colors are input to the image data conversion unit 10 (step S101). Next, the statistical value / saturation calculation unit 12 obtains the maximum value Dmax and the minimum value Dmin for the image data Ri, Gi, Bi of three colors (step S102). Next, the statistical value / saturation calculating unit 12 obtains the saturation S according to the following equation (2) based on the maximum value Dmax and the minimum value Dmin (step S103).
S = (Dmax-Dmin) / Dmax (2)
However, in the equation (2), when Dmax = 0, S = 0.

Next, the distribution ratio / coefficient calculation unit 13 obtains the distribution ratio WRs of the white subframe based on the parameter WRX (step S104). In this embodiment, the parameter WBR for determining the luminance of the light source 27 in the white subframe period Tw is assumed to be 1, and the distribution ratio WRs = WRX and WRX = 0.5 will be mainly described. The WRs is not limited to this, and may be a value near 0.5. More generally, the distribution ratio WRs may be WBR / (1 + WBR) or a value in the vicinity thereof (the details will be described later).

Next, the distribution ratio / coefficient calculating unit 13 obtains the coefficient Ks according to a calculation formula described later based on the saturation S and the parameters WRX, RA, RB, and WBR (step S105). When calculating the coefficient Ks in step S105 after calculating the distribution ratio WRs in step S104, the distribution ratio / coefficient calculation unit 13 uses the distribution ratio WRs and uses the maximum value Dmax of the input image data D1 as the input image data D1. Under the condition that the possible maximum value is 1, the maximum value (or the value below the maximum value) that the coefficient Ks can take is determined. The adjustment coefficient Ks does not have to be necessarily introduced. In the case where the adjustment coefficient Ks is not introduced, the present embodiment is configured to set Ks = 1 in the following.

Next, based on the image data Ri, Gi, Bi of three colors, the minimum value Dmin, the distribution ratio WRs, the coefficient Ks, and the parameter WBR, the drive image data calculation unit 33 performs the following equations (5a) to (5d) Image data Wd, Bd, Gd, Rd of four colors are obtained according to the above (step S106).
Wd = WRs · Dmin · Ks · PP / WBR (5a)
Bd = (Bi−WRs · Dmin) Ks · PP (5b)
Gd = (Gi-WRs.Dmin) Ks.PP (5c)
Rd = (Ri-WRs-Dmin) Ks-PP (5d)
However, in the equations (5a) to (5d), PP is a value (= P / Pmax) obtained by dividing the maximum value P for tone limitation by the maximum value Pmax of tone. In the following description, it is assumed that PP = 1.

As described above, the image data conversion unit 10 uses the parameters RA, RB, WRX, and WBR to generate data (data of BGR pixel data of the input image) Ri, Gi, and Bi of each pixel included in the input image data D1. The driving image data D2 is generated by obtaining white, blue, green and red image data (WBGR pixel data values for driving) Wd, Bd, Gd and Rd of the pixel.

<About 1.3 distribution ratio WRs>
As described above, the parameter WBR for determining the luminance of the light source 27 in the white subframe period Tw is 1 (the luminance of the light source 27 emitting light in the white subframe period Tw is 1 for the light source 27 emitting in other than the white subframe period Tw). Under the condition that it is the same as the luminance), the distribution ratio WRs is set to 50% (step S104) or a value in the vicinity thereof. More generally, the distribution ratio WRs in the present embodiment is set as follows.

The maximum value of the blue, green and red image data Bd, Gd, Rd included in the driving image data D2 is Ddmax, and the minimum value is Ddmin. When PP = 1, Wd, Ddmax, and Ddmin are given by the following equations (6a) to (6c), respectively.
Wd = WRs · Dmin · Ks / WBR (6a)
Ddmax = (Dmax−WRs · Dmin) Ks (6b)
Ddmin = (Dmin-WRs · Dmin) Ks (6c)
Here, if the distribution ratio WRs is determined such that Wd <Ddmin, the transmittance of the liquid crystal decreases when switching from the other subframe period to the white subframe period Tw, and from the white subframe period Tw to the other subframes It rises when switching to a period. As described later, in the present embodiment, this point is used to prevent color mixing due to the optical response. If Wd <Ddmin is solved using equations (6a) and (6c), the following equation is obtained.
WRs <WBRo
However, it is WBRo = WBR / (1 + WBR). On the other hand, in order to reduce color breakup, it is preferable to increase the distribution ratio WRs. Therefore, in the present embodiment, the distribution ratio WRs is set to WBRo = WBR / (1 + WBR) or a value in the vicinity thereof in consideration of both prevention of color mixing due to the optical response and reduction of color breakup.

<1.4 Regarding the adjustment coefficient Ks>
Hereinafter, the adjustment coefficient Ks will be described (step S105 in FIG. 3).

The saturation S and the distribution ratio WRs take values of 0 or more and 1 or less. The maximum value Ddmax and the minimum value Ddmin of the white image data Wd included in the drive image data D2 and the blue, green and red image data Bd, Gd, Rd included in the drive image data D2 are respectively And the above equations (6a) to (6c) (where PP = 1).

As shown in FIG. 4, the range of (S, WRs) indicated by the saturation S and the distribution ratio WRs is a first area where Ddmin <Wd <Ddmax, a second area where Ddmax <Wd, and Wd < It is divided into the 3rd area which becomes Ddmin. In the present embodiment, WBRo shown in FIG. 4 is given by the following equation.
WBRo = WBR / (1 + WBR)

If (S, WRs) is in the first area, then DDmin = Ddmin and DDmax = Ddmax. Taking equation (6a) and (6b) into consideration, substituting equation (1) by substituting Dmin = Dmax (1-S) into equation (1) leads to the following equation (20).
Ks ≦ RB / (Dmax × [1- {WRs (1-RA) + RA} (1-S))] (20)
The coefficient Ks is determined as in the following equation (21) so that the equation (20) holds even when the maximum value Dmax is 1 (the maximum value that the input image data D1 can take). Expression (21) indicates the maximum value that the coefficient Ks can take under the condition of Dmax = 1 when (S, WRs) is in the first area.
Ks = RB / [1- {WRs (1-RA) + RA} (1-S)] (21)
The maximum value Dmax is the lightness Vi of the input image data D1. The lightness Vi = Dmax = max (Ri, Gi, Bi) may be hereinafter referred to as “input lightness Vi” in order to distinguish it from the lightness V = Ks · Dmax after amplification and compression processing described later.

When the distribution ratio WRs is determined such that (S, WRs) falls within the first area, Ddmin <Wd <Ddmax is established, and the four-color image data Wd, Bd, contained in the drive image data D2 is established. The difference between Gd and Rd is minimized (at most (Ddmax−Ddmin)). In this case, the maximum value that the coefficient Ks can take under the condition of using the distribution ratio WRs and Dmax = 1 is given by the equation (21).

When (S, WRs) is in the third area, DDmin = Wd and DDmax = Ddmax. Considering these equations and equations (6a), (6b) and Dmin = Dmax (1-S), the following equation (24) is derived from the above equation (1).
Ks ≦ WBR · RB / [Dmax {WBR− (WBR + RA) WRs (1-S)}] (24)
The coefficient Ks is determined as in the following equation (25) so that the equation (24) holds even when the maximum value Dmax indicating the input brightness Vi is 1 (the maximum value that the input image data D1 can take). Equation (24) shows the maximum value that the coefficient Ks can take under the condition of Dmax = 1 when (S, WRs) is in the third area.
Ks = WBR.RB / {WBR- (WBR + RA) WRs (1-S)} (25)

<1.5 Details of backlight driving>
Next, with reference to FIG. 5 to FIG. 7, details of driving of the backlight 25 as the light source unit will be described. In the following, the backlight 25 is configured using a light emitting diode (LED), but the configuration of the backlight is not limited to this (the same applies to other embodiments).

FIG. 5 is a block diagram showing the configuration of the backlight drive circuit 23 as a light source drive circuit. The backlight drive circuit 23 includes a lighting control circuit 230 and a backlight power circuit 232. As shown in FIG. 5, the lighting control circuit 230 includes an LED control circuit 231, a red light source switch 23r, a green light source switch 23g, and a blue light source switch 23b. The LED control circuit 231 generates a red light source control signal CswR, a green light source control signal CswG, and a blue light source control signal CswB based on the timing control signal TC from the timing control circuit 21, and switches the red light source switch 23r for the green light source. The switch 23g and the blue light source switch 23b are respectively provided. The red light source switch 23r is in the on state when the red light source control signal CswR is at the high level (H level), and is in the off state when the red light source control signal CswR is at the low level (L level). The green light source switch 23g is in the on state when the green light source control signal CswG is at the H level, and is in the off state when the green light source control signal CswG is at the L level. The blue light source switch 23b is on when the blue light source control signal CswB is at the H level, and is off when the blue light source control signal CswB is at the L level.

The red light source 27r, the green light source 27g, and the blue light source 27b in the backlight 25 are connected to the backlight power circuit 232 via the red light source switch 23r, the green light source switch 23g, and the blue light source switch 23b. As a result, the red light source drive signal SdvR, the green light source drive signal SdvG, and the blue light source drive signal SdvB are supplied as drive signals to the red light source 27r, the green light source 27g, and the blue light source 27b. Therefore, the red light source 27r is on when the red light source control signal CswR is H level and off when L level, and the green light source 27g is on when the green light source control signal CswG is H level and off when L level In the state, the blue light source 27b is in the on state when the blue light source control signal CswB is at the H level, and in the off state when the blue light source control signal CswB is at the L level.

In order to make it possible to adjust the light emission intensity of each light source 27 x (x = r, g, b) by pulse width modulation, the LED control circuit 231 outputs each light source control signal CswX (X = R, G, B). Instead of setting the H level, it is configured to output a pulse signal of a duty ratio according to a desired light emission intensity.

6 shows a conventional field sequential liquid crystal display device (hereinafter referred to as “conventional image display device” or “first method”) having a backlight drive circuit similar to the backlight drive circuit 23 configured as shown in FIG. It is a timing chart for explaining the driving of the backlight in the “conventional example”. Before describing driving of the backlight in the present embodiment, driving of the backlight in the first conventional example will be described as a comparative example. In the following, in the configuration of the first conventional example, the same or corresponding parts as in the image display device according to the present embodiment are given the same reference numerals.

As shown in FIG. 6, in the first prior art example, the first half of each subframe period Tg, Tr, Tw, Tb is a turn-off period Toff during which light is not irradiated from the backlight 25 to the liquid crystal panel 24. The second half is a backlight 25 is a lighting period Ton during which light is emitted to the liquid crystal panel 24. The symbol "Cft" in FIG. 6 indicates a subframe indication signal included in the timing control signal TC supplied from the timing control circuit 21 to the LED control circuit 231 (the same applies to FIG. 7). The panel drive circuit 22 scans the liquid crystal panel 24 in the scanning period Tsc included in the extinguishing period Toff of each subframe period Tx (x = g, r, w, b) to form driving image data D 2. Pixel data is sequentially written to the liquid crystal panel 24. The backlight drive circuit 23 selectively drives the red light source 27r, the green light source 27g, and the blue light source 27b in the backlight 25 in accordance with the red light source control signal CswR, the green light source control signal CswG, and the blue light source control signal CswB. As can be seen from the waveforms of the light source control signals CswR, CswG, CswB shown in FIG. 6, in the green subframe period Tg as the first subframe period, only the green light source 27g serves as the red subframe period Tr as the second subframe period. Then, only the red light source 27r is turned on, and only the blue light source 27b is turned on in the blue sub-frame period Tb as the fourth sub-frame period, and the red light source 27r and the green light source are turned on in the white sub-frame period Tw as the third sub-frame period. 27 g and the blue light source 27 b are simultaneously turned on. Thus, green light, red light, white light and blue light are respectively irradiated to the back surface of the liquid crystal panel 24 in the green subframe period Tg, the red subframe period Tr, the white subframe period Tw and the blue subframe period Tb. . In the example shown in FIG. 6, the green light source control signal CswG is a pulse width modulated signal so that the green light source 27g lights up with a desired light emission intensity.

By driving the backlight 25 together with driving of the liquid crystal panel 24 (writing of pixel data to each pixel formation unit 30) in this manner, a green image is generated in the green subframe period Tg based on the input signal Din. A red image is displayed in the red subframe period Tr, a white image is displayed in the white subframe period Tw, and a blue image is displayed in the blue subframe period Tb, and a color image by additive color mixture over time is displayed on the liquid crystal panel 24. Be done. The details of the display operation in such a first conventional example will be described later (see FIG. 8).

FIG. 7 is a timing chart for explaining the driving of the backlight 25 in the present embodiment. The first half of the primary color sub-frame periods Tg, Tr excluding the blue sub-frame period Tb which is a primary color sub-frame period (hereinafter referred to as “following sub-frame period”) immediately after the white sub-frame period Tw as a common color sub-frame period The light-off period Toff during which light is not emitted from the light 25 to the liquid crystal panel 24 is a lighting period Ton during which light is emitted from the backlight 25 to the liquid crystal panel 24 in the second half. In the white subframe period Tw as the common color subframe period and the blue subframe period Tb as the subsequent subframe period, the corresponding light sources are lit in both the first half and the second half. The panel drive circuit 22 scans the liquid crystal panel 24 in the scanning period Tsc included in the first half of each sub-frame period Tx (x = g, r, w, b) as in the first conventional example, and generates driving image data. The respective pixel data constituting D 2 are sequentially written to the liquid crystal panel 24. The backlight drive circuit 23 selectively drives the red light source 27r, the green light source 27g, and the blue light source 27b in the backlight 25 in accordance with the red light source control signal CswR, the green light source control signal CswG, and the blue light source control signal CswB. As can be seen from the waveforms of the light source control signals CswR, CswG, and CswB shown in FIG. 7, only the green light source 27g is used in the green subframe period Tg as the first subframe period, and the red subframe period Tr as the second subframe period. Then, only the red light source 27r is turned on, and only the blue light source 27b is turned on in the blue sub-frame period Tb as the fourth sub-frame period, and in the white sub-frame period Tw as the third sub-frame period The light source 27r is turned on, and the red light source 27r, the green light source 27g, and the blue light source 27b are simultaneously turned on in the second half period. Thus, green light, red light, white light and blue light are respectively irradiated to the back surface of the liquid crystal panel 24 in the green subframe period Tg, the red subframe period Tr, the white subframe period Tw and the blue subframe period Tb. . However, in the white subframe period Tw, the light emission color of the backlight 25 is slightly shifted in the red direction from white (hereinafter referred to as “white in white display”) displayed when the input image data D1 for white display is given. (Details will be described later).

Thus, in the present embodiment as well, driving of the liquid crystal panel 24 (writing of pixel data to each pixel formation unit 30) and driving of the backlight 25 allow the green sub-frame period Tg based on the input signal Din. The green image is displayed in the red subframe period Tr, the white image is displayed in the white subframe period Tw, and the blue image is displayed in the blue subframe period Tb. Is displayed on the liquid crystal panel 24. Details of the display operation in this embodiment will be described later (see FIG. 9). In the following, a red light emitting diode (hereinafter referred to as "R-LED") as red light source 27r, a green light emitting diode (hereinafter referred to as "G-LED") as green light source 27g, and a blue light emitting diode as blue light source 27b It is assumed that each (hereinafter referred to as "B-LED") is used (the same applies to other embodiments).

<1.6 Display operation>
FIG. 8A is a timing chart and waveform diagram for explaining the display operation of the first conventional example in which the backlight 25 is driven as shown in FIG. 6, and FIG. 8B shows the first example. It is a figure which shows the lighting time of each light source (R-LED, G-LED, B-LED) in a prior art example. Here, for convenience of explanation, it is assumed that the luminance of the light source 27 emitting in the white subframe period Tw is the same as the luminance of the light source 27 emitting in the period other than the white subframe period Tw, that is, WBR = 1. The timing chart in FIG. 8A shows sub-frame periods Tx (x = g, r, w) of the R-LED as the red light source 27r, the G-LED as the green light source 27g, and the B-LED as the blue light source 27b. , And b), and the two waveform diagrams in the lower part of FIG. 8A indicate the response of the liquid crystal in each liquid crystal panel 24 when displaying white and displaying red. It shows with the state. In the two waveform diagrams in FIG. 8A, the response of liquid crystal (temporal change in transmittance) is indicated by a thick dotted line. In FIG. 8B, three primary color light sources (red light source (R-LED), green light source (G-LED), blue light source (B-) in the primary color sub-frame period (RGB-SF) in one frame period Tfr. LED) Length of each lighting time, lighting time of each of three primary color light sources (R-LED, G-LED, B-LED) in white subframe period Tw (W-SF) as common color subframe period And the length of lighting time of each of the three primary color light sources (R-LED, G-LED, B-LED) in one frame period Tfr (TOTAL). Here, the lighting time is shown as a relative value (duty ratio) in which the length of one frame period Tfr is "1", and the "primary color subframe period" means a red subframe period Tr, a green subframe period. It is a generic term for Tg and blue subframe period Tb. The above expression method in FIG. 8 is also adopted in FIGS. 9 and 14 to 29.

In the first conventional example, the ratio of the lighting time of three primary color light sources (R-LED, G-LED, B-LED) in one frame period (that is, the ratio of the duty ratio) is 1: 2/3: 1 ( Each light source (R-) is set such that the ratio of the lighting time (ratio of duty ratio) of the three primary color light sources for white balance is 1: 2/3: 1 (see “TOTAL” in FIG. 8B). It is assumed that current values at the time of lighting of the LED, G-LED, and B-LED are set in advance. Furthermore, the central time of each sub-frame period (the time corresponding to 50% of one sub-frame period) is preset as the light emission control reference time point tecr, and in the first conventional example, the light source is turned on in each sub-frame period When it does, lighting is started from this light emission control reference time point tecr. The period (first half period) before the light emission control reference time point tecr in each subframe period includes the period in which the response of the liquid crystal is in the transition state (transition state), and light emission from the start point in each subframe period Until the control reference time point tecr is the time to suppress the lighting of the light source. In addition, although it is preferable to set the light emission control reference time point tecr to an end time point of time in which the light emission of the light source is to be suppressed from the viewpoint of the response characteristic of the liquid crystal in each sub-frame period, it is not limited thereto. When the light emission control reference time point tecr is set to the end time of the time to suppress the light emission of the light source, the time from the light emission control reference time point tecr to the end point in the subframe period corresponds to the maximum light source lighting time. The maximum light source lighting time corresponds to the maximum lighting time that can be secured in each sub-frame period while avoiding the color mixing hue shift due to the response characteristic of the liquid crystal. Also in the following embodiments, it is assumed that the light emission control reference time point tecr is set from such a viewpoint. Also in the following, the central time of each subframe period (the time corresponding to 50% of one subframe period) is used as the light emission control reference time point tecr, but the light emission control reference time point tecr is limited to this. However, it should be determined in consideration of the response characteristics of the liquid crystal, the writing speed of the pixel data to the liquid crystal panel 24, and the like.

FIG. 9A is a timing chart and a waveform diagram for explaining the display operation in the present embodiment in which the backlight 25 is driven as shown in FIG. 7, and FIG. It is a figure which shows the lighting time and light-emission quantity of each primary color light source (R-LED, G-LED, B-LED). In the present embodiment, the ratio of the lighting time of the three primary color light sources (R-LED, G-LED, B-LED) in one frame period Tfr is 1.5: 1: 1.5 (see FIG. 9B). Lighting of each light source (R-LED, G-LED, B-LED) so that the ratio of lighting time of three primary color light sources for white balance is 1: 1.5: 1 (see “TOTAL”) The hour current value is preset. In this embodiment, the backlight 25 is driven according to the red light source control signal CswR, the green light source control signal CswG, and the blue light source control signal CswB shown in FIG. 7, and the panel is driven based on the drive image data D2 described above. As the liquid crystal panel 24 is driven by the circuit 22, as shown in FIG. 9A, the

light sources

27r, 27g and 27b in the backlight 25 are turned on, and the liquid crystal in the liquid crystal panel 24 responds.

The bar graph in the lower part of FIG. 9B shows the light emission amount of each of the three primary color light sources (R-LED, G-LED, B-LED) in the white subframe period Tw (W-SF) in one frame period Tfr. , And the amount of light emission of each of the three primary color light sources in one frame period Tfr (TOTAL). (Such an expression method is shown in FIG. 15, FIG. 17, FIG. 19, FIG. 20, FIG. 21, FIG. 23, FIG. 26, 27, 28 and 29). Since the current values at the time of lighting each of the three primary color light sources (R-LED, G-LED, B-LED) of the backlight 25 are set as described above (see the bar graph on the lower right of FIG. 9B) When the input image data D1 showing white display in the present embodiment is given, white is displayed on the liquid crystal panel 24. However, red, green, and blue corresponding to ratios of 1, 0.5, and 0.5, which are ratios of lighting times of three primary color light sources (R-LED, G-LED, B-LED) in the white subframe period Tw, respectively. The amount of light emission increases in the order of blue, red, and green based on the above setting of the current value at the time of lighting of each light source (LED) (see the bar graph on the lower left of FIG. 9B). As a result, the light emission color of the backlight 25 in the white subframe period Tw shifts from white in the white display to the red direction.

In the present embodiment, when the input image data D1 indicating red display is given, the red light source 27r is turned on in the first half of the white sub-frame period Tw, as shown in the waveform diagram in the lower part of FIG. The amount of light emitted per light source (LED) is increased more than in the first conventional example while suppressing the hue shift.

<1.7 Action and Effect>
FIG. 10 is a diagram showing a display operation when the color to be displayed (hereinafter referred to as “target color”) is changed in the image display device according to the present embodiment. In FIG. 10, white (W), mixed color of white and cyan (W + C), mixed color of white and red (W + R), cyan (C), red (R), green (G), yellow (Y), blue (B) The input image data D1 and the driving image data D2 in the present embodiment for nine cases (hereinafter referred to as “case (1)” to “case (9)”) in which magenta (M) is the target color, respectively. And a display operation (a response state of a liquid crystal and an operation state of an LED as a light source), and a white color is set as a target color in a conventional image display device having a distribution ratio WRs of 100% as a comparative example. The drive image data and display operation (hereinafter referred to as "case (10)") are also shown. In FIG. 10, thick dotted lines in the waveform diagram showing display operation indicate the response of liquid crystal (temporal change of transmittance).

In the present embodiment, the four-color image data Wd, Bd, and Gd in the driving image data D2 are set such that the distribution ratio WRs becomes WBRo = WBR / (1 + WBR) (50% when WBR = 1). , Rd are obtained (step S104 in FIG. 3), and Wd ≦ Ddmin. Therefore, the value of the white image data Wd as driving image data in the white subframe period Tw is a red subframe which is a primary color subframe period (hereinafter referred to as “preceding subframe period”) immediately before the white subframe period. The primary color sub-frame period (following sub-frame period) which is the same as or smaller than the value of the red image data Rd as driving image data of the period Tr and immediately after the white sub-frame period The value is the same as or smaller than the value of the blue image data Bd as driving image data of the blue subframe period Tb. As a result, in each pixel 26 of the liquid crystal panel 24, the transmittance of the liquid crystal is reduced when switching from the red subframe period Tr as the preceding subframe period to the white subframe period Tw as the common color subframe period. When switching from the white sub-frame period Tw as the common color sub-frame period to the blue sub-frame period Tb as the subsequent sub-frame period, the transmittance of the liquid crystal increases. That is, as shown in the waveform diagrams of cases (1) to (9) in FIG. 10, the liquid crystal response (optical response of the liquid crystal panel 24) in this embodiment is white from the red subframe period (preceding subframe period) Tr. Whenever it switches to a subframe period (common color subframe period) Tw, it becomes a decay response, and when it switches from a white subframe period (common color subframe period) Tw to a blue subframe period (following subframe period) Tb, it always becomes a rise response. Become.

In the present embodiment, as shown in FIG. 9A, a red light source which is a light source of a color corresponding to a red subframe period Tr as a preceding subframe period in the white subframe period Tw as a common color subframe period. The relative time (the time based on the start point t3 of the white subframe period) at which the 27r (R-LED) starts lighting is a green subframe that is a primary color subframe period other than the preceding subframe period and the subsequent subframe period. It is earlier than the relative time (lighting start time tecr with reference to the start point t1 in the green subframe period Tg) that the light source 27g (G-LED) starts lighting in the period Tg. Further, as shown in FIG. 9A, the relative time (light source point in the blue subframe period t4) at which the light source 27b (B-LED) starts lighting in the blue subframe period Tb as the subsequent subframe period is used as a reference. Time) is a relative time (lighting start time in the green subframe period Tg) at which the light source 27g (G-LED) starts lighting in the green subframe period Tg which is a primary color subframe period other than the preceding subframe period and the subsequent subframe period It is earlier than the lighting start time tecr) based on t1.

According to the above configuration in the present embodiment, when switching from the red subframe period Tr (preceding subframe period) to the white subframe period Tw (common color subframe period), the response of the liquid crystal becomes a decay response. Even if the red light source (R-LED) is turned on in the first half of the period Tw, problems such as saturation reduction and hue shift do not occur. Also, when switching from the white subframe period Tw (common color subframe period) to the blue subframe period Tb (following subframe period), the response of the liquid crystal is a rise response, so the blue light source Even if the B-LED) lights up, color mixing does not occur. Therefore, according to the present embodiment, it is possible to improve the luminance of each color without causing problems such as saturation reduction and hue shift. In addition, since the time gap between light sources of the respective colors (each color LED) is not lighted, that is, the time gap for light emission from the backlight 25 is reduced, the display brightness can be improved without increasing the number of light sources (LEDs).

<1.8 Modification Example Regarding Distribution Ratio>
In the first embodiment, the ratio of the amount of display light to be emitted in the white subframe period Tw to the amount of display light of the white component to be emitted in one frame period Tfr for displaying each pixel of the input image, that is, the distribution ratio WRs is It is determined by the value of the parameter WRX and is 50% (see step S104 in FIG. 3). However, the parameter WBR for determining the luminance of the light source 27 in the white subframe period is assumed to be 1. More generally, the value to be set as the distribution ratio WRs is WBR / (1 + WBR). The distribution ratio WRs may be set to a fixed value near 50% (more generally, a fixed value near WBR / (1 + WBR)) by setting the parameter WRX. If the distribution ratio WRs is within a predetermined range near 50%, the response of the liquid crystal is substantially a decay response when switching from the preceding subframe period (red subframe period Tr) to the common color subframe period (white subframe period Tw) Even if the red light source (R-LED) is turned on in the first half of the common color sub-frame period (white sub-frame period Tw) and a color shift occurs, it is within the human visual tolerance. When switching from the common color subframe period (white subframe period Tw) to the subsequent subframe period (blue subframe period Tb), the response of the liquid crystal substantially becomes a rise response, and in the first half of the subsequent subframe period (blue subframe period Tb) This is because even if a blue light source (B-LED) is turned on and a color shift occurs, it is within the human visual tolerance.

The distribution ratio WRs is within a predetermined range around 50% where color shift can be tolerated by human vision (more generally, within a predetermined range near WBR / (1 + WBR)). It may change according to the saturation or the lightness. Hereinafter, an example in which the configuration related to the distribution ratio WRs in the first embodiment is modified as described above will be described.

The image display apparatus according to the present modification is provided with the distribution ratio WRs not as a fixed value (WRX ≒ 50%) but as a function that changes according to the saturation S or the lightness, but the other configuration is the first embodiment. It is similar to the form, and has a configuration as shown in FIG. In the following, in the configuration of the image display device according to the present modification, the same reference numerals are given to portions that are the same as or correspond to the configuration of the image display device according to the first embodiment.

First, the distribution ratio WRs as a function of the saturation S will be described as a first example. Hereinafter, in order to distinguish the distribution ratio of the first example from the distribution ratio of another example, it is also referred to as “first distribution ratio WRs1”.

The saturation S and the distribution ratio WRs take values of 0 or more and 1 or less. The maximum value of the blue, green and red image data Bd, Gd, Rd included in the driving image data D2 is Ddmax, and the minimum value is Ddmin. When PP = 1, Wd, Ddmax, and Ddmin are given by the following equations (6a) to (6c), respectively.
Wd = WRs · Dmin · Ks / WBR (6a)
Ddmax = (Dmax−WRs · Dmin) Ks (6b)
Ddmin = (Dmin-WRs · Dmin) Ks (6c)
When Wd <Ddmax is solved in consideration of Dmax = Dmin / (1-S), the following equation (7a) is derived. The following equation (7b) is derived by solving Wd> Ddmin.
WRs <WBRo / (1-S) (7a)
WRs> WBRo ... (7b)
However, in the present modification, it is assumed that the parameter WBR for determining the luminance of the light source 27 in the white subframe period Tw is one. For this reason, in the equations (7a) and (7b), WBRo = 1/2.

As the distribution ratio WRs satisfying the above formulas (7a) and (7b), for example, a first distribution ratio WRs1 defined by the following formulas (8a) to (8c) can be adopted.
a) When WRX ≧ Ts and 1−S <WBRx WRs1 = WRX−WRX (1−S) ² / (3 · WBRx ² ) (8a)
b) When WRX ≧ Ts and 1−S ≧ WBRx WRs1 = WBRo / (1-S) (8b)
c) When WRX <Ts WRs1 = (WBRo-WRX) (1-S) ² + WRX (8c)
However, in the formulas (8a) to (8c), WBRo = 1/2, Ts = 3/4, and WBRx = 3 / (4WRX).

FIG. 11 is a graph showing the first distribution ratio WRs1. The function for obtaining the first distribution ratio WRs1 when WRX <Ts (= 3/4) takes the value WBRo (= 1/2) when S = 0 and takes the maximum value WRX when S = 1 It is a quadratic function. The function for obtaining the first distribution ratio WRs1 when WRX ≧ Ts is the fractional function WRs1 = 1 / {2 (1-S)} when 1−S ≧ WBRx, and when S = 1 when 1−S <WBRx Is a quadratic function that takes the maximum value WRX. The latter function is determined such that the graph of the former function and the graph of the latter function are in contact at a point (WBRx, WBRo / (1-WBRx)). The graph shown in FIG. 11 is always in the first area shown in FIG. By using such a first distribution ratio WRs1 as the distribution ratio WRs of the white subframe, the difference between the four color image data Wd, Bd, Gd, and Rd can be minimized.

In the configuration using such a first distribution ratio WRs1, when the response speed of the pixel 26 is slower as the display tone is lower, the parameter WRX is set to a value closer to 1, and the pixel 26 is higher as the display tone is higher. When the response speed of is slow, the parameter WRX is set to a value close to 0.5. Thereby, the color reproducibility of the image display device 1 can be enhanced. However, in this modification, in order to set the distribution ratio WRs to a value close to 50% so that the color shift is within the visual tolerance of human, according to FIG. Set to a degree.

Next, a distribution ratio WRs, which is a function of lightness after amplification and compression, will be described as a second example. Hereinafter, in order to distinguish the distribution ratio of the second example from the distribution ratio of another example, it is also referred to as “second distribution ratio WRsv2”. In the following description, calculation is performed in consideration of V = Dmax · Ks and Dmin = Dmax (1-S). Here, Dmax indicates the input lightness Vi, and V indicates the lightness after the amplification and compression processing (hereinafter also referred to as “adjusted lightness”). Furthermore, in the following, the parameter storage unit 11 stores the parameter WRZ in addition to the parameters RA, RB, WRX, and WBR described above, and the statistical value / saturation calculation unit 12 calculates the first distribution ratio WRs1. And the second distribution ratio WRsv2 is calculated using the parameter WRZ.

When (S, WRs1) is in the first area shown in FIG. 4, DDmin = Ddmin and DDmax = Ddmax. Therefore, from Ddmax ≦ RA · Ddmin + RB, the minimum value WRsva of the second distribution ratio WRsv2 in this case is given by the following expression (27a). When (S, WRs1) is in the second area shown in FIG. 4, DDmin = Ddmin and DDmax = Wd. Therefore, from Wd ≦ RA · Ddmin + RB, the maximum value WRsvb of the second distribution ratio WRsv2 in this case is given by the following equation (27b). When (S, WRs1) is in the third area shown in FIG. 4, DDmin = Wd and DDmax = Ddmax. Therefore, from Ddmax ≦ RA · Wd + RB, the minimum value WRsvc of the second distribution ratio WRsv2 in this case is given by the following equation (27c).
WRsva = RA / (RA-1) + (RB-V) / {(RA-1) V (1-S)} (27a)
WRsvb = WBR.RA / (1 + WBR.RA) + WBR.RB / {(1 + WBR.RA) V (1-S)} (27b)
WRsvc = WBR (V-RB) / {(WBR + RA) V (1-S)} (27 c)

When the second distribution ratio WRsv2 is obtained, if (S, WRs1) is in the first area shown in FIG. 4, the second distribution ratio WRsv2 is set to the value WRsva or more shown in the equation (27a). When (S, WRs1) is in the second area shown in FIG. 4, the second distribution ratio WRsv2 is set to the value WRsvb or less shown in the equation (27b). If (S, WRs1) is in the third area shown in FIG. 4, the second distribution ratio WRsv2 is set to the value WRsvc or more shown in the equation (27c). Considering that the second distribution ratio WRsv2 takes a value in the range of 0 ≦ WRsv2 ≦ 1, the second distribution ratio WRsv2 is determined to satisfy the following equation (28).
max (0, WRsva, WRsvc) WR WRsv 2 min min (1, WRsvb) (28)

FIG. 12 is a diagram for describing a method of determining a function for obtaining the second distribution ratio WRsv2. A curve indicated by a solid line in FIG. 12 indicates the second distribution ratio WRsv2 when S = 0.5. Here, RA = 0.25, RB = 0.75, WBR = 0.5, and WRX = 0.75. The distribution ratio / coefficient calculation unit 13 calculates the first distribution ratio WRs1 according to the equations (8a) to (8c), and calculates the coefficient Ks according to the equation (21).

A portion surrounded by a thick broken line in FIG. 12 indicates the range of the adjusted brightness (brightness after amplification and compression processing) V and the second distribution ratio WRsv2 that satisfy Expression (28). The function for obtaining the second distribution ratio WRsv2 is determined such that the graph of the function is in the range surrounded by the thick broken line shown in FIG.

For example, a function for obtaining the second distribution ratio WRsv2 when the coefficient Ks is less than the predetermined value Tsv is a quadratic function that takes the maximum value WRZ when V = 0 and takes the value WRs1 when V = Ks. Further, a function for obtaining the second distribution ratio WRsv2 when the coefficient Ks is equal to or more than the predetermined value Tsv is a quadratic function that takes the maximum value WRZ when V <Tsv and V = 0. WRsv2 = A / when V ≧ Tsv It can be expressed as V + B, and is a fraction function taking the value WRs1 when V = Ks (however, A = WBR · RB / {(1 + WBR / RA) (1-S)}). The following equations (29) and (30a) to (30c) can be derived by determining two functions so that the graphs of two functions are in contact when V = Tsv (where WRZ ≦ WRs1) WRsv2 = WRs1).
Tsv = 3 · Ks · WBRb / [2 {Ks (1-S) (WRZ−WRs1) + WBRb}] (29)
a) When Ks ≧ Tsv and V ≧ Tsv WRsv2 = WRs1 + WBRb (Ks−V) / {Ks (1-S) V} (30a)
b) When Ks ≧ Tsv and V <Tsv WRsv2 = WRZ−WBRb · V ² / {2 (1-S) Tsv ³ } (30b)
c) Ks <when Tsv WRsv2 = WRZ- (WRZ-WRs1 ) V 2 / Ks 2 ... (30c)
However, in the equations (29) and (30a) to (30c), WBRb = WBR · RB / (1 + WBR · RA), and V = Dmax · Ks. The parameter WRZ takes a value within the range of WRs ≦ WRZ ≦ 1. V is adjusted brightness (brightness after amplification and compression processing).

As shown in FIG. 12, the second distribution ratio WRsv2 is larger as the adjustment brightness V is smaller. Therefore, in the second example in which the second distribution ratio WRsv2 is set to the distribution ratio WRs to the white subframe, the distribution ratio / coefficient calculating unit 13 obtains a larger distribution ratio WRs as the adjustment brightness V decreases. Therefore, when the adjustment brightness V is small, the color break reduction effect can be increased. The parameter WRZ is set to a value closer to the first distribution ratio WRs1 as the response speed of the pixel 26 is slower, and the parameter WRZ is set to a value closer to 1 as the response speed of the pixel 26 is faster. As a result, it is possible to obtain a suitable distribution ratio WRs according to the response speed of the pixel 26, and to suppress color breakup. However, in the present modification, in order to set the distribution ratio WRs to a value near 50% (more generally, a value near WBR / (1 + WBR)) so that the color shift is within the visual tolerance of human beings, From FIG. 12, the parameter WRZ is set to a predetermined value near the first distribution ratio WRs1, for example.

<1.9 Other Configurations and the Like in the First Embodiment>
According to the present embodiment, the lighting time of the red light source (R-LED) in the white subframe period Tw as the common color subframe period is the time from the light emission control reference time point tecr in the white subframe period Tw to the end point t4 Since the time corresponding to the second half period, ie, the time Ton that can be regarded as the conventional maximum light source lighting time, is longer, the light source 27b in the blue subframe period Tb as the subsequent subframe period is It is preferable to increase the lighting time of In the present embodiment, as described above, the light source 27b (B-LED) is lit in the blue subframe period Tb, not only in the second half period (tecr to t5) but also in the first half period (t4 to tecr). The configuration from the viewpoint of maintaining the white balance is already included (see FIG. 9A).

Further, as described above, the lighting time of the red light source 27r (R-LED) is longer in the white subframe period Tw and the lighting time of the blue light source 27b (B-LED) is longer in the blue subframe period Tb. From the viewpoint of maintaining balance, it is preferable to increase the lighting time in each sub-frame period of the light source of primary colors other than red and blue, that is, the green light source 27g (G-LED) according to these increments. According to such a configuration, the white balance is maintained only by controlling the duty ratio of the light source control signal CswX (X = R, G, B) for driving each of the

light sources

27r, 27g, 27b. The color reproduction range can be expanded by suppressing the reduction in color and the hue shift, and the all display color luminance can be improved.

Whether the liquid crystal response becomes a decay response or a rise response when switching from the blue subframe period Tb to the green subframe period Tg depends on the input image data D1. Therefore, in the green subframe period Tg, unlike the white subframe period Tw and the blue subframe period Tb, the light source 27g (G-LED) is not lit in the first half period (before the light emission control reference time point tecr). It is done. Therefore, as described above, in the present embodiment, before the light emission control reference time point tecr in the green subframe period Tg which is the primary color subframe period other than the preceding subframe period and the subsequent subframe period (based on the optical response characteristic of liquid crystal Each light source (each LED) is preset with a current to be supplied at the time of lighting so that white balance can be secured without lighting the light source 27g (during a period in which light should not be turned on) (see FIG. 9B) . However, even if the current setting for each light source (R-LED, G-LED, B-LED) is as in the past, if the deviation from the white balance is within the visual range of human vision, such FIG. The current setting corresponding to the lighting time of each light source shown in (B) is not necessarily required.

FIG. 13 is a diagram for explaining the method of compensating for the deviation of the mixed color hue in the present embodiment, and the circle in FIG. 13 shows the color wheel. In this color wheel, the hue changes in the circumferential direction, and "R", "G" and "B" indicate angular positions corresponding to red, green and blue, respectively, and "C" and "M" , “Y” indicate angular positions corresponding to cyan, magenta and yellow, respectively. Further, in this color wheel, the saturation changes in the radial direction, and the center thereof corresponds to saturation = 0 (achromatic). In FIG. 13, the positions in the color wheel of the target color of the cases (1) to (9) shown in FIG. 10 are indicated by “(1)” to “(9)”.

In the present embodiment, as described above, the luminance of each color can be improved while suppressing the saturation decrease and the hue shift, but as can be seen from the waveform diagram (waveform of thick dotted line) showing the display operation in FIG. Due to the response characteristics of the liquid crystal, a slight shift occurs in saturation and hue from the target colors of cases (1) to (9). Arrows attached in the vicinity of “(1)” to “(9)” in FIG. 13 indicate the directions of these deviations, that is, the display colors corresponding to the respective target colors of cases (1) to (9) are relevant. It indicates the direction of movement from the chromaticity point of the target color. In FIG. 13, the arrows in the cases (2), (4), and (7) point in the circumferential direction, which means that the mixed hue as the display color deviates from the hue of the target color and the color balance is lost. (See the waveform diagram showing the display operation for cases (2), (4) and (7) in FIG. 10). Therefore, it is preferable to set in advance the spectrum of each of the

light sources

27r, 27g, 27b (R-LED, G-LED, B-LED) so that such hue shift is compensated. However, when trying to compensate for the above-mentioned hue shift by setting of such an LED spectrum, there is a possibility that the white balance can not be maintained. However, in this case, the duty ratio (ratio of lighting time in one frame period) of each of the

light sources

27r, 27g, 27b in the primary color subframe period (RGB-SF) and the white subframe period (W-SF) is adjusted. Can maintain the white balance. In the cases other than the above cases (2), (4) and (7), there may be a case where a shift in saturation occurs in the display color (when an arrow in the radial direction is shown in FIG. 13). There is no deviation. If the movement of the chromaticity point as shown by the arrow in FIG. 13 is within the visual tolerance of human beings, it is not always necessary to perform spectrum setting for compensation of such hue shift for each light source. Absent.

In the first embodiment, in the green sub-frame period Tg which is a primary color sub-frame period other than the sub-frame periods (preceding and subsequent sub-frame periods) immediately before and after the common color sub-frame period (white sub-frame period Tw). The light source starts to light at the light emission control reference time point tecr. This means that the light source turns on after the end of the transient state of the liquid crystal response. On the other hand, in the white subframe period Tw as the common color subframe period and the blue subframe period Tb as the subsequent subframe period, the light emission control reference time point tecr (before conventionally, light emission is suppressed from the viewpoint of liquid crystal response characteristics) The lighting of the light source is started within the expected time, which is the feature of the first embodiment.

In each subframe period, the end time of the light emission suppression period from the viewpoint of the response characteristic of the liquid crystal is set so that the maximum light source lighting time is from the light emission control reference time point tecr to the end point of the subframe period. Although it is preferable to set as the light emission control reference time point tecr, it may be different from such a setting if the color shift and the decrease of the average light emission amount are within the visual range of human vision.

<1.10 First Modification of First Embodiment>
In the first embodiment, the light source 27b (B-LED) is before the light emission control reference time point tecr in the blue subframe period Tb which is a subsequent subframe period of the white subframe period Tw as the common color subframe period. Lighting (not only in the second half period but also in the first half period) (see FIGS. 7 and 9), but instead, at the light emission control reference time point tecr in the blue subframe period Tb, the light source 27b (B -LED) may start lighting (it will be in the lighting state only in the second half period). Hereinafter, an image display apparatus having such a configuration will be described as a first modified example of the first embodiment.

In the present modification, as described above, the light source starts lighting at the light emission control reference time point tecr in the blue sub-frame period Tb, but the other configuration is the same as that of the first embodiment. Therefore, in the configuration of the image display device according to the present modification, the same reference numerals as those in the configuration of the image display device according to the first embodiment denote the same or corresponding parts. 1, 3 and 5).

FIG. 15A is a timing chart and waveform chart for explaining the display operation in this modification, and FIG. 15B is a three primary color light source (R-LED, G-LED, B in this modification). -LED) It is a figure which shows each lighting time and light-emission quantity. FIG. 14 (A) is a timing chart and a waveform diagram for describing a display operation in a conventional example (hereinafter referred to as “second conventional example”) corresponding to the present modification, and FIG. 14 (B) FIG. 8 is a diagram showing the lighting time of each of the three primary color light sources (R-LED, G-LED, B-LED) in the conventional example 2; In this second conventional example, the ratio of the lighting time of the three primary color light sources (R-LED, G-LED, B-LED) in one frame period Tfr (TOTAL) is 1: 2 in proportion to the ratio of this modification. The third embodiment differs from the first conventional example in which the ratio is 1: 2/3: 1 in that it is 3: 2/3, but the other points are the same as the first conventional example.

In this modification, as shown in FIG. 15A, since the light source 27b (B-LED) is turned on only in the second half period (tecr to t5) in the blue subframe period Tb, each

light source

27r, 27g , 27b (R-LED, G-LED, B-LED) are slightly different from the light emission pattern of the first embodiment. However, the display operation (liquid crystal response and LED operation) is substantially the same as in the first embodiment, and in the white subframe period Tw as the common color subframe period, the light source 27r of the primary color corresponding to the preceding subframe period Tr. (R-LED) starts to light up before the light emission control reference time point tecr (lights up not only in the second half period of the white subframe period Tw but also in the first half period) (FIG. 9A, FIG. See A).

In this modification, as shown in FIG. 15B, the ratio of the lighting time of the three primary color light sources (R-LED, G-LED, B-LED) for achieving white balance is 1.5: 1: 1. The current values at the time of lighting each of the three primary color light sources are set in advance so that According to such current setting, as understood from the bar graph in FIG. 15B, the emission color of the backlight 25 is slightly shifted from white to red in the white subframe period Tw.

According to the above modification, compared to the first embodiment, since the emission color in the white subframe period Tw is different, the effect of reducing the color breakup is different. The same effect as the form can be obtained.

<1.11 Second Modification of First Embodiment>
In the first embodiment, in the white subframe period Tw as the common color subframe period, the red light source 27r (R-LED) corresponding to the preceding subframe period starts lighting before the light emission control reference time point tecr. (Refer to FIG. 7 and FIG. 9), but instead, in the white subframe period Tw, the red light source 27r corresponding to the preceding subframe period Tr (R -The LED) may start lighting at the light emission control reference time point tecr (it will be in the lighting state only in the second half period). Hereinafter, an image display apparatus having such a configuration will be described as a second modification of the first embodiment.

In the present modification, as described above, the red light source 27r starts lighting at the light emission control reference time point tecr in the white subframe period Tw, but the other configuration is the same as that of the first embodiment. Therefore, in the configuration of the image display device according to the present modification, the same reference numerals as those in the configuration of the image display device according to the first embodiment denote the same or corresponding parts. 1, 3 and 5).

FIG. 17A is a timing chart and waveform chart for explaining the display operation in this modification, and FIG. 17B is a three primary color light source (R-LED, G-LED, B in this modification). -LED) It is a figure which shows each lighting time and light-emission quantity. FIG. 16 (A) is a timing chart and waveform chart for explaining the display operation in the conventional example (hereinafter referred to as “third prior art”) corresponding to the present modification, and FIG. FIG. 8 is a diagram showing the lighting time of each of the three primary color light sources (R-LED, G-LED, B-LED) in the conventional example 3; In this third conventional example, the ratio of the lighting time of the three primary color light sources (R-LED, G-LED, B-LED) in one frame period Tfr (TOTAL) is 2/3 in accordance with the ratio of this modified example: The second conventional example differs from the first conventional example in that it is 2/3: 1, but the other points are the same as the first conventional example.

In this modification, as shown in FIG. 17A, since the red light source 27r (R-LED) is turned on only in the second half period (tecr to t4) in the white subframe period Tw, each light source 27r, The light emission pattern of 27 g and 27 b (R-LED, G-LED, B-LED) is slightly different from the light emission pattern of the first embodiment. However, the display operation (liquid crystal response and LED operation) is substantially the same as in the first embodiment, and in the blue subframe period Tb as the subsequent subframe period (subframe period immediately after the white subframe period Tw), The light source 27b (B-LED) starts to light up before the light emission control reference time point tecr (the light is on in the first half period as well as the second half period of the blue subframe period Tb) (FIG. 9A, FIG. 17 (A)).

In this modification, as shown in FIG. 17B, the ratio of the lighting time of the three primary color light sources (R-LED, G-LED, B-LED) for achieving white balance is 1: 1: 1.5. The current values at the time of lighting each of the three primary color light sources are set in advance so that According to such current setting, as understood from the bar graph in FIG. 17B, the emission color of the backlight 25 is slightly shifted from white to yellow in the white subframe period Tw.

<2. Second embodiment>
Next, an image display apparatus according to the second embodiment will be described.
FIG. 19A is a timing chart and waveform chart for explaining the display operation in the present embodiment, and FIG. 19B is a three primary color light source (R-LED, G-LED, B in the present embodiment). -LED) It is a figure which shows each lighting time and light-emission quantity. FIG. 18A is a timing chart and waveform chart for explaining the display operation in the conventional example corresponding to the present embodiment, and FIG. 19B is a three primary color light source (R-LED in this conventional example). , G-LED, B-LED) is a diagram showing the lighting time of each. This prior art example is the same as the first prior art example shown in FIG.

In the first embodiment, in the white subframe period Tw as the common color subframe period, the red light source 27r (R-LED) corresponding to the preceding subframe period starts lighting before the light emission control reference time point tecr. (Not only in the second half period but also in the first half period) (see FIGS. 7 and 9). On the other hand, in the present embodiment, as shown in FIG. 19A, in the white subframe period Tw, the red light source 27r (R-LED) corresponding to the preceding subframe period Tr lights up at the light emission control reference time point tecr. Start (become lit only in the second half period).

In the first embodiment, the lighting time of the red light source (R-LED) in the white subframe period Tw is the time from the light emission control reference time point tecr in the white subframe period Tw to the end point t4 (white subframe period Length of lighting time of other light source (green light source or blue light source) other than red light source at Tw, or length of lighting time of red light source at white subframe period Tw in the conventional example), The lighting time of the blue light source 27b (B-LED) in the subsequent subframe period Tb has a length corresponding to the lighting time of the red light source in the white subframe period Tw (FIGS. 8 and 9). reference). Furthermore, in the first embodiment, the lighting time in each subframe period of the green light source 27g (G-LED) corresponding to the primary color subframe period Tg other than the preceding and succeeding subframe periods is white based on the time difference. The length corresponds to the lighting time of the red light source 27r in the subframe period Tw (see FIGS. 8 and 9). On the other hand, in the present embodiment, the lighting time of the blue light source 27b (B-LED) and the green light source 27g (G-LED) does not increase as described above, and the lighting time of these is similar to that of the conventional example (see FIG. 18, see FIG. 19).

The backlight drive circuit 23 in the present embodiment is configured such that the three primary color light sources (R-LED, G-LED, B-LED) of the backlight 25 operate as described above, but other components in the present embodiment The configuration of is the same as that of the first embodiment. Therefore, in the configuration of the image display device according to the present embodiment, the same reference numerals as those in the configuration of the image display device according to the first embodiment denote the same or corresponding parts. 1, 3 and 5).

As shown in FIG. 19B, in this embodiment, the ratio of the lighting time of the three primary color light sources (R-LED, G-LED, B-LED) in one frame period Tfr (TOTAL) for achieving white balance The current value at the time of lighting of each of the three primary color light sources is preset so that 1: 2/3: 1. According to such current setting, as understood from the bar graph in FIG. 19B, the emission color of the backlight 25 is slightly shifted from white to red in the white subframe period Tw.

As shown in FIG. 19A, in the present embodiment, the red light source 27r (R-LED) is turned on only in the second half period (tecr to t4) in the white subframe period Tw, and the green light source in one frame period Tfr. The lighting time of (G-LED) does not increase and is the same as the first conventional example (see FIG. 18). Further, in the blue subframe period Tb which is a subsequent subframe period, the light source 27b (B-LED) is not lit at the start point of the blue subframe period Tb, but is lit at time t41 earlier than the light emission control reference time point tecr. Is started (t4 <t41 <tecr), and the light is turned on from this time t41 to the end point of the blue subframe period Tb. However, the lighting time of the blue light source (B-LED) in one frame period Tfr does not increase and is the same as in the first conventional example (see FIG. 18).

Further, as shown in FIG. 19A, in the present embodiment, the green light source 27g (G-LED) is continuously driven in the lighting period (tecr to t2) in the green subframe period Tg, and the white subframe period is In the lighting period (tecr to t4) at Tw, driving is performed by the pulse width modulation method. The blue light source 27b (B-LED) is also driven continuously in the lighting period (t41 to t5) in the blue subframe period Tb, and driven by the pulse width modulation method in the lighting period (tecr to t4) in the white subframe period Tw. Be done. Therefore, for the green light source 27g (G-LED), the time during which the green sub-frame period Tg is on is longer than the time during which the white sub-frame period Tw is on, and the blue light source 27b (B-LED) Also, the lighting time in the blue subframe period Tb is longer than the lighting time in the white subframe period Tw. That is, in the present embodiment, the lighting time in the corresponding primary color subframe period Tx of the light sources 27x other than the red light source 27r (R-LED) corresponding to the preceding subframe period (red subframe period Tr) is the common color subframe period It is longer than the lighting time of the light source 27x in the (white subframe period Tw) (x = g, b).

According to the present embodiment, compared to the first embodiment, the single-color luminance can be improved without changing the white luminance, so that the white luminance in the image represented by the input image data D1 is set to the single-color luminance. It is suitable when it becomes large with respect to. On the other hand, although the light emission pattern of each

light source

27r, 27g, 27b (R-LED, G-LED, B-LED) is different from the light emission pattern of the first embodiment, the display operation (liquid crystal response and LED operation) Is similar to that of the first embodiment, and basically the same effect as that of the first embodiment can be obtained.

<2.1 First Modification of Second Embodiment>
In the second embodiment, the three primary color light sources (R-LED, G-LED, B-LED) are lit in the entire second half period (tecr to t4) in the white subframe period Tw as the common color subframe period. It is in the state. However, the green light source (G-LED) and the blue light source (B-LED) are driven by the pulse width modulation method in the second half period (tecr to t4) so that the lighting time in one frame period Tfr does not increase ( 19 (A)).

On the other hand, in this modification, the three primary color light sources (R-LED, G-LED, B-LED) of the backlight 25 are driven as shown in FIG. FIG. 20A is a timing chart and waveform chart for explaining the display operation in this modification, and FIG. 20B is a three primary color light source (R-LED, G-LED, B in this modification). -LED) It is a figure which shows each lighting time and light-emission quantity. The configuration other than the configuration relating to driving of the backlight 25 in the present modification is the same as that of the first and second embodiments. Therefore, in the configuration of the image display device according to the present modification, the same or corresponding parts as those in the configuration of the image display device according to the first and second embodiments are given the same reference numerals, It abbreviates (refer to Drawing 1, Drawing 3, and Drawing 5).

As shown in FIG. 20 (B), in the present modification, the lighting time of the green light source (G-LED) in one frame period Tfr does not increase as in the second embodiment (the conventional example shown in FIG. As well). However, as shown in FIG. 20A, in this modification, unlike the second embodiment, the green light source 27g (G-LED) and the blue light source 27b (B-LED) are in the white subframe period Tw. Instead of being driven by the pulse width modulation method, the white subframe period Tw is continuously driven in a predetermined period in contact with the end point t4 of the white subframe period Tw. That is, in the white sub-frame period Tw, the green light source 27g and the blue light source 27b start lighting at time t31 after the light emission control reference time point tecr, and continuously from time t31 to the end point t4 of the white sub-frame period Tw. It lights up. The other operations of the three primary color light sources (R-LED, G-LED, B-LED) are the same as in the second embodiment.

According to such a modification, it is possible to further improve single-color luminance while achieving the same effect as that of the second embodiment.

<2.2 Second Modification of Second Embodiment>
In the second embodiment, the three primary color light sources (R-LED, G-LED, B-LED) are lit in the entire second half period (tecr to t4) in the white subframe period Tw as the common color subframe period. It is in the state.

On the other hand, in this modification, the three primary color light sources (R-LED, G-LED, B-LED) of the backlight 25 are driven as shown in FIG. FIG. 21A is a timing chart and waveform chart for explaining the display operation in this modification, and FIG. 21B is a three primary color light source (R-LED, G-LED, B in this modification). -LED) It is a figure which shows each lighting time and light-emission quantity. The configuration other than the configuration relating to driving of the backlight 25 in the present modification is the same as that of the first and second embodiments. Therefore, in the configuration of the image display device according to the present modification, the same or corresponding parts as those in the configuration of the image display device according to the first and second embodiments are given the same reference numerals, It abbreviates (refer to Drawing 1, Drawing 3, and Drawing 5).

As shown in FIG. 21B, in the present modification, as in the second embodiment, the lighting time of the green light source (G-LED) in one frame period Tfr does not increase (the conventional example shown in FIG. 18 and the prior art) As well). However, as shown in FIG. 21A, in this modification, unlike the second embodiment, the green light source 27g (G-LED) and the blue light source 27b (B-LED) are in the white subframe period Tw. Instead of being driven by the pulse width modulation method, the white subframe period Tw is continuously driven in a predetermined period in contact with the end point t4 of the white subframe period Tw. In this respect, the present modification is the same as the first modification of the second embodiment (see FIG. 20). However, as shown in FIG. 21 (A), in this modification, unlike the second embodiment and the first modification, the red light source 27r (R-LED) is on in the white subframe period Tw. A certain period is divided into a first period (t3 to t31) and a second period (t32 to t4) respectively contacting the start point t3 and the end point t4 of the white subframe period Tw. The red light source 27r is astigmatic from the end point t31 of the first period to the start point t32 of the second period. The other operations of the three primary color light sources (R-LED, G-LED, B-LED) are the same as in the second embodiment.

In this modification, the lighting of the red light source 27r in the white subframe period Tw is performed so that the white color contributing to the reduction of color break in the luminescent color obtained in the white subframe period Tw does not change with respect to white in white display. The periods can be separated into a first period and a second period (see the lower bar in FIG. 21B). According to such a modification, while achieving the same effect as the second embodiment, the red luminance (monochromatic luminance) as a primary color corresponding to the red subframe period Tr which is the preceding subframe period is further added. It can be improved.

<3. Third embodiment>
Next, an image display apparatus according to a third embodiment will be described.
FIG. 23A is a timing chart and waveform chart for explaining the display operation in this embodiment, and FIG. 23B is a three primary color light source (R-LED, G-LED, B in this embodiment). -LED) It is a figure which shows each lighting time and light-emission quantity. FIG. 22 (A) is a timing chart and waveform chart for explaining the display operation in the conventional example corresponding to the present embodiment, and FIG. 22 (B) is a three primary color light source (R-LED in this conventional example). , G-LED, B-LED) is a diagram showing the lighting time of each. This prior art example is the same as the first prior art example shown in FIGS.

In the second embodiment, in the white subframe period Tw as the common color subframe period, the red light source 27r (R-LED) corresponding to the preceding subframe period starts lighting at the light emission control reference time point tecr, and From the start point t3 of the white subframe period Tw to the light emission control reference time point tecr (first half period), the light is not lit (see FIG. 19). On the other hand, in the present embodiment, as shown in FIG. 23A, in the white subframe period Tw, the red light source (R-LED) corresponding to the preceding subframe period Tr receives the light emission control reference time from its start point t3. It is in the lighting state up to tecr (first half period), and is in the non-lighting state from the light emission control reference time point tecr to its end point t4. The other operations of the three primary color light sources (R-LED, G-LED, B-LED) of the backlight 25 in the present embodiment are the same as those of the second embodiment, and each light source in one frame period Tfr ( The lighting time of the R-LED, G-LED, and B-LED is the same as that of the conventional example without increasing. The second embodiment is also the same as the second embodiment (see FIGS. 22 and 23). Further, as shown in FIG. 23B, also in this embodiment, as in the second embodiment, three primary color light sources (R-LED, G) in one frame period Tfr (TOTAL) for achieving white balance. The current value at the time of lighting each of the three primary color light sources is preset so that the ratio of the lighting time of the LED and B-LED) is 1: 2/3: 1.

The backlight drive circuit 23 in the present embodiment is configured such that the three primary color light sources (R-LED, G-LED, B-LED) of the backlight 25 operate as described above, but other light sources in the present embodiment The configuration is the same as that of the first and second embodiments. Therefore, in the configuration of the image display device according to the present embodiment, the same reference numerals as those in the configuration of the image display device according to the first and second embodiments denote the same or corresponding parts. It abbreviates (refer to Drawing 1, Drawing 3, and Drawing 5).

As shown in FIG. 23A, in the present embodiment, in the white subframe period Tw as the common color subframe period, the lighting period of the red light source 27r (R-LED) corresponding to the preceding subframe period is the first half period The lighting periods of the green light source 27g (G-LED) and the blue light source 27b (B-LED) are only the second half period (tecr to t4). For this reason, the chromaticity point of the common color contributing to the reduction of the color break is shifted from the white in the white display to the cyan direction.

According to this embodiment, since the lighting periods of the respective light sources (R-LED, G-LED, B-LED) are arranged as described above in the white subframe period Tw, the single-color luminance (red Luminance) can be further improved. Further, as in the second embodiment, compared to the first embodiment, the single-color luminance can be improved without changing the white luminance, so that in the image represented by the input image data D1, the white luminance is the single-color luminance. It is suitable when it becomes large. On the other hand, although the light emission pattern of each

light source

27r, 27g, 27b (R-LED, G-LED, B-LED) is different from the light emission pattern of the first embodiment, the display operation (liquid crystal response and LED operation) Is basically the same as that of the first embodiment, and substantially the same effect as that of the first embodiment can be obtained.

<3.1 First Modification of Third Embodiment>
In the third embodiment, the green light source 27g (G-LED) and the blue light source (B-LED) are turned on in the entire second half period (tecr to t4) in the white subframe period Tw as the common color subframe period. Although it is in the state, it is driven by the pulse width modulation method in the second half period (tecr to t4) so that the lighting time in one frame period Tfr does not increase (see FIG. 23A).

On the other hand, in this modification, the three primary color light sources (R-LED, G-LED, B-LED) of the backlight 25 are driven as shown in FIG. FIG. 24A is a timing chart and waveform chart for explaining the display operation in this modification, and FIG. 24B is a three primary color light source (R-LED, G-LED, B in this modification). -LED) It is a figure which shows each lighting time and light-emission quantity. The configuration other than the configuration relating to driving of the backlight 25 in the present modification is the same as that of the first and second embodiments. Therefore, in the configuration of the image display device according to the present modification, the same or corresponding parts as those in the configuration of the image display device according to the first and second embodiments are given the same reference numerals, It abbreviates (refer to Drawing 1, Drawing 3, and Drawing 5).

As shown in FIG. 24A, in this modification, unlike the third embodiment, the green light source 27g (G-LED) and the blue light source 27b (B-LED) are pulsed in the white subframe period Tw. It is not driven by the width modulation method, but is continuously driven in a predetermined period in contact with the end point t4 of the white subframe period Tw. That is, in the white sub-frame period Tw, the green light source 27g (G-LED) and the blue light source 27b (B-LED) start lighting at time t31 after the light emission control reference time point tecr. The lighting state continues until the end point t4 of the frame period Tw. The other operations of the three primary color light sources (R-LED, G-LED, B-LED) are the same as in the third embodiment.

As shown in FIG. 24A, in the present embodiment, in the white subframe period Tw as the common color subframe period, the lighting period of the red light source 27r (R-LED) corresponding to the preceding subframe period is the first half period ( The lighting period of the green light source 27g (G-LED) and the blue light source 27b (B-LED) is only the period (t31 to t4) close to the end point in the second half period. For this reason, the chromaticity point of the common color contributing to the reduction of the color break is shifted from the white in the white display to the cyan direction.

According to this embodiment, since the lighting periods of the light sources (R-LED, G-LED, B-LED) in the white subframe period Tw are arranged as described above, The single-color luminance can be further improved while achieving the same effect as that of the embodiment.

<4. Fourth embodiment>
Next, an image display apparatus according to a fourth embodiment will be described.
FIG. 26A is a timing chart and waveform chart for explaining the display operation in the present embodiment, and FIG. 26B is a three primary color light source (R-LED, G-LED, B in the present embodiment). -LED) It is a figure which shows each lighting time and light-emission quantity. FIG. 25 (A) is a timing chart and waveform chart for explaining the display operation in the conventional example corresponding to the present modification, and FIG. 25 (B) is a three primary color light source (R-LED in this conventional example). , G-LED, B-LED) is a diagram showing the lighting time of each. This prior art example is the same as the first prior art example shown in FIG. 8, FIG. 18 and FIG.

In the first to third embodiments, in the white subframe period Tw as the common color subframe period, the blue light source 27b (B-LED) corresponding to the subsequent subframe period lights up at the light emission control reference time point tecr. The light emission state is started until the end point t4 of the white subframe period Tw is started (see FIG. 9, FIG. 19, and FIG. 23). On the other hand, in the present embodiment, as shown in FIG. 26A, the blue light source (B-LED) is not turned on in the white subframe period Tw, and only in the blue subframe period Tb which is the subsequent subframe period. It is lit. The other operations of the three primary color light sources (R-LED, G-LED, B-LED) of the backlight 25 in the present embodiment are substantially the same as those in the second embodiment, and one operation is performed in one frame period Tfr. The point of the lighting time of each light source (R-LED, G-LED, B-LED) is the same as that of the conventional example without any increase, which is also the same as the twelfth embodiment (see FIGS. 25 and 26). Further, as shown in FIG. 26B, also in this embodiment, as in the second and third embodiments, three primary color light sources (R−) in one frame period Tfr (TOTAL) for achieving white balance. The current value at the time of lighting of each of the three primary color light sources is preset so that the ratio of the lighting time of LED, G-LED, B-LED) is 1: 2/3: 1.

The backlight drive circuit 23 in the present embodiment is configured such that the three primary color light sources (R-LED, G-LED, B-LED) of the backlight 25 operate as described above, but other light sources in the present embodiment The configuration is the same as that of the first to third embodiments. Therefore, in the configuration of the image display device according to the present embodiment, the same reference numerals as those in the configuration of the image display device according to the first to third embodiments denote the same or corresponding parts. It abbreviates (refer to Drawing 1, Drawing 3, and Drawing 5).

As shown in FIG. 26A, in the present embodiment, the blue light source 27b (B-LED) corresponding to the blue subframe period Tb as a subsequent subframe period is a white subframe period Tw as a common color subframe period. In this case, it does not turn on, but turns on only in the blue subframe period Tb. In the example shown in FIG. 26A, the blue light source 27b is in the lighting state in the entire blue sub-frame period Tb (t4 to t5). Therefore, the emission color of the backlight 25 is shifted from white in white display to orange in the white subframe period Tw.

According to this embodiment, since the lighting periods of the respective light sources (R-LED, G-LED, B-LED) are arranged as described above in each frame period Tfr, the white luminance is changed. It is possible to improve single-color luminance without For this reason, in the case where amplification processing is performed on the input image data D1 using the adjustment coefficient Ks, the present embodiment is particularly effective when the white luminance becomes larger than the single luminance. On the other hand, although the light emission pattern of each

light source

<First Modification of Fourth Embodiment>
In the fourth embodiment, the green light source 27g (G-LED) is lit in the entire second half period (tecr to t4) in the white subframe period Tw as the common color subframe period, but one frame Driving is performed by the pulse width modulation method in the second half period (tecr to t4) so that the lighting time in the period Tfr does not increase (see FIG. 26A).

On the other hand, in this modification, the three primary color light sources (R-LED, G-LED, B-LED) of the backlight 25 are driven as shown in FIG. FIG. 27A is a timing chart and waveform chart for explaining the display operation in this modification, and FIG. 27B is a three primary color light source (R-LED, G-LED, B in this modification). -LED) It is a figure which shows each lighting time and light-emission quantity. The configuration other than the configuration relating to the driving of the backlight 25 in this modification is the same as that of the first to fourth embodiments. Therefore, in the configuration of the image display device according to the present modification, the same or corresponding parts as those in the configuration of the image display device according to the first to fourth embodiments are given the same reference numerals, It abbreviates (refer to Drawing 1, Drawing 3, and Drawing 5).

As shown in FIG. 27A, in this modification, unlike the fourth embodiment, the green light source 27g (G-LED) is driven by the pulse width modulation method in the white subframe period Tw. Instead, the white subframe period Tw is continuously driven in a predetermined period in contact with the end point t4. That is, in the white subframe period Tw, the green light source 27g starts lighting at time t31 after the light emission control reference time point tecr, and is continuously lit from time t31 to the end point t4 of the white subframe period Tw. . The other operations of the three primary color light sources (R-LED, G-LED, B-LED) are the same as in the fourth embodiment.

As shown in FIG. 27A, in this embodiment, in the white subframe period Tw as the common color subframe period, the lighting period of the red light source 27r (R-LED) corresponding to the preceding subframe period is the second half period ( The lighting period of the green light source 27g (G-LED) is only the period (t31 to t4) close to the end point in the second half period. Therefore, in the white subframe period Tw, the light emission color of the backlight 25 is shifted from white in the white display to the orange direction.

According to the present embodiment, since the lighting periods of the light sources (R-LED, G-LED, B-LED) in each frame period Tfr are arranged as described above, the fourth embodiment is preferable. It is possible to further improve single-color luminance while achieving the same effect as that of the embodiment.

4.2 Second Modification of Fourth Embodiment
In the fourth embodiment, in the white subframe period Tw as the common color subframe period, the red light source 27r (R-LED) is in the first half period (t3 to tecr) and in the second half period (tecr to t4) in the non-lighting state. The green light source 27g (G-LED) is also lit only in the second half period (tecr to t4), but the second half period (G-LED) does not increase the lighting time in one frame period Tfr. It is driven by pulse width modulation at tecr to t4) (see FIG. 26A).

On the other hand, in this modification, the three primary color light sources (R-LED, G-LED, B-LED) of the backlight 25 are driven as shown in FIG. FIG. 28A is a timing chart and waveform chart for explaining the display operation in this modification, and FIG. 28B is a three primary color light source (R-LED, G-LED, B in this modification). -LED) It is a figure which shows each lighting time and light-emission quantity. The configuration other than the configuration relating to the driving of the backlight 25 in this modification is the same as that of the first to fourth embodiments. Therefore, in the configuration of the image display device according to the present modification, the same or corresponding parts as those in the configuration of the image display device according to the first to fourth embodiments are given the same reference numerals, It abbreviates (refer to Drawing 1, Drawing 3, and Drawing 5).

As shown in FIG. 28B, in the present modification, the lighting time of the green light source (G-LED) in one frame period Tfr does not increase as in the second to fourth embodiments (FIG. 18, FIG. 25 and so forth). However, as shown in FIG. 28A, in this modification, unlike the fourth embodiment, the green light source 27g (G-LED) is driven by the pulse width modulation method in the white subframe period Tw. Instead, the white subframe period Tw is continuously driven in a predetermined period in contact with the end point t4 of the white subframe period Tw. In this point, the present modification is the same as the first modification of the fourth embodiment (see FIG. 27). However, as shown in FIG. 28A, in this modification, unlike the fourth embodiment and its first modification, the lighting period of the red light source 27r (R-LED) is in the white subframe period Tw. The white subframe period Tw is separated into a first period (t3 to t31) and a second period (t32 to t4) respectively in contact with the start point t3 and the end point t4. The red light source 27r is astigmatic from the end point t31 of the first period to the start point t32 of the second period. From this, the chromaticity point of the common color contributing to the reduction of color break shifts from white to yellow in white display. The other operations of the three primary color light sources (R-LED, G-LED, B-LED) are the same as in the fourth embodiment.

According to such a modification, it is possible to further improve the luminance (monochromatic luminance) of the primary color corresponding to the preceding subframe period Tr while achieving the same effect as that of the fourth embodiment. In this modification, the lighting period of the red light source 27r in the white subframe period Tw is separated into the first period and the second period without shifting the chromaticity point of white obtained as the emission color in the white subframe period Tw. It is also possible to do (see FIG. 28B).

4.3 Third Modification of Fourth Embodiment
In the fourth embodiment, in the white subframe period Tw as the common color subframe period, the red light source 27r (R-LED) is in the first half period (t3 to tecr) and in the second half period (tecr to t4) in the non-lighting state. The green light source 27g (G-LED) is also lit only in the second half period (tecr to t4), but the second half period (G-LED) does not increase the lighting time in one frame period Tfr. It is driven by pulse width modulation at tecr to t4) (see FIG. 26A).

On the other hand, in this modification, the three primary color light sources (R-LED, G-LED, B-LED) of the backlight 25 are driven as shown in FIG. FIG. 29A is a timing chart and waveform chart for explaining the display operation in this modification, and FIG. 29B is a three primary color light source (R-LED, G-LED, B in this modification). -LED) It is a figure which shows each lighting time and light-emission quantity. The configuration other than the configuration relating to the driving of the backlight 25 in this modification is the same as that of the first to fourth embodiments. Therefore, in the configuration of the image display device according to the present modification, the same or corresponding parts as those in the configuration of the image display device according to the first to fourth embodiments are given the same reference numerals, It abbreviates (refer to Drawing 1, Drawing 3, and Drawing 5).

As shown in FIG. 29 (B), in this modification, the lighting time of the green light source (G-LED) in one frame period Tfr does not increase as in the second to fourth embodiments (FIG. 18, FIG. 25 and so forth). However, as shown in FIG. 29A, in this modification, unlike the fourth embodiment, the green light source 27g (G-LED) is driven by the pulse width modulation method in the white subframe period Tw. Instead, the white subframe period Tw is continuously driven in a predetermined period in contact with the end point t4 of the white subframe period Tw. In this point, the present modification is the same as the first modification of the fourth embodiment (see FIG. 27). However, as shown in FIG. 29A, in this modification, unlike the fourth embodiment and the first modification, the red light source 27r (R-LED) is in the first half in the white subframe period Tw. In the period (t3 to tecr), the light is on, and in the second half period (tecr to t4), the light is off.

According to such a modification, it is possible to further improve the luminance (monochromatic luminance) of the primary color corresponding to the preceding subframe period Tr while achieving the same effect as that of the fourth embodiment.

<5. Other Modifications>
The present invention is not limited to the above-described embodiments and the above-described modifications, and various modifications may be made without departing from the scope of the present invention.

In the above embodiments, the subframe period immediately before the white subframe period Tw (preceding subframe period) as the common color subframe period is the red subframe period Tr, and the immediately following subframe period (following subframe period) Is the blue sub-frame period Tb, and the sub-frame period except immediately before and after the common color sub-frame period is the green sub-frame period Tg (see FIG. 7 and FIG. 9). The order of Tg, Tb and Tw is not limited to this. Different from the above depending on the characteristics of each

light source

27r, 27g, 27b (forward voltage VF and emission spectrum of R-LED, G-LED, B-LED, etc.), type (use of phosphor etc.), current etc. In some cases it may be preferable to take order.

In each of the above embodiments, each frame period is a blue, green, red primary color subframe period and a white subframe period as a common color subframe period (a white subframe which is a blue, green, blue common color) And sub-frame periods of other primary colors and common-color sub-frame periods. In the present specification, the “common color” is basically a color including all the color components of the primary colors corresponding to the primary color sub-frame period in each frame period, and the ratio of these color components is not limited. I assume. However, from the viewpoint of suppressing color breakup by a common color sub-frame, a common color sub-frame corresponding to another color composed of two primary colors instead of the white sub-frame period as a common color sub-frame period A period (eg, a yellow subframe period consisting of red and green) may be used. Also, from the same point of view, any color other than black, such as “yellow-green”, “red” or “red half of brightness” instead of “white” or “yellow” corresponds to the common color subframe period It is also possible to

Further, in each of the above embodiments, the distribution ratio WRs and the adjustment coefficient Ks have been described not only in the case of fixed values but also in the case where the distribution ratio WRs and the adjustment coefficient Ks are obtained according to a specific formula. Calculation formulas for obtaining the coefficient Ks may be other than those described above. For example, a conventionally known calculation formula may be used as a calculation formula for determining the distribution ratio WRs.

Furthermore, in each of the above embodiments, the liquid crystal panel 24 that transmits light from the backlight 25 as a light source unit is used as a display device, and an image is displayed by controlling the transmittance of the liquid crystal panel 24. The present invention is not limited to a field sequential display using a transmissive light modulator such as the liquid crystal panel 24, but can be applied to a field sequential display using a reflective light modulator. . For example, the present invention can be applied to a field sequential type projection display apparatus using a reflective liquid crystal panel called LCOS (Liquid Crystal On Silicon) as a light modulator. The present invention can also be applied to field sequential type image display devices other than liquid crystal display devices, for example, self-luminous type image display devices such as organic EL (ElectroLuminescence) display devices. Furthermore, the present invention can also be applied to a see-through image display device or the like having a function of making the back of the display panel visible.

Although the image display apparatus according to each embodiment and its modification has been described above, various features of the image display apparatus according to these embodiments and its modification may be combined arbitrarily as long as not against the nature thereof. An image display apparatus according to a modification of the above can also be configured.

<6. Other>
The present application is an application for claiming priority based on Japanese Patent Application No. 2017-127361 entitled "Field-sequential type image display device and image display method" filed on June 29, 2017, The content of the national application is included in the present application by reference.

DESCRIPTION OF SYMBOLS 1 ... Image display apparatus 10 ... Image data conversion part 20 ... Display part 11 ... Parameter memory part 12 ... Statistical value / saturation calculating part 13 ... Distribution ratio / coefficient calculating part 33 ... Driving image data calculating part 21 ... Timing control circuit 22 ... panel drive circuit (light modulation unit drive circuit)
23 ... back light drive circuit (light source drive circuit)
24 ... liquid crystal panel (light modulation unit)
25 ... back light (light source part)
26: pixel 27: light source 27r: red light source (R-LED)
27g green light source (G-LED)
27b Blue light source (B-LED)
Ks: Adjustment factor WRs: Distribution ratio of white subframes (common color distribution ratio)
WRs1 ... first distribution ratio WRsv2 ... second distribution ratio

Claims

A field sequential type image display device including a plurality of sub-frame periods each including a plurality of primary color sub-frame periods corresponding to a plurality of primary colors and a common color sub-frame period included in each frame period.
A light source unit including a plurality of light sources emitting light in the plurality of primary colors;
A light modulation unit that transmits or reflects light from the light source unit;
A light source unit driving circuit for driving the light source unit such that light of a corresponding color is emitted to the light modulation unit in each subframe period;
A light modulation unit driving circuit for controlling the transmittance or the reflectance of the light modulation unit so that an image of a corresponding color is displayed in each subframe period;
The light source unit drive circuit is configured to start lighting the light source of the first primary color corresponding to the preceding subframe period which is the immediately preceding subframe period in the common color subframe period from the start point of the common color subframe period And the time from the start of the subsequent subframe period which is a subframe period immediately after the common color subframe period to the time when the light source of the corresponding second primary color starts lighting in the subsequent subframe period Of at least one of the plurality of primary colors from a start point of a primary color sub-frame period corresponding to another primary color other than the first and second primary colors to a time point when the light source starts lighting in the primary color The image display apparatus which drives the said light source part so that it may become shorter than time.
When the input image data corresponding to the plurality of primary colors is received, the transmittance or the reflectance in the light modulation unit does not substantially change or decrease when the preceding subframe period is switched to the common color subframe period, and The plurality of subframe periods from the input image data such that the transmittance or the reflectance in the light modulator does not substantially change or increase when switching from the common color subframe period to the subsequent subframe period. An image data conversion unit for generating driving image data corresponding to
The light modulation unit drive circuit controls the transmittance or the reflectance in the light modulation unit so that an image of a corresponding color is displayed in each subframe period based on the driving image data. Image display device as described.
When the ratio of the luminance of each light source in the common color sub-frame period to the luminance in the primary color sub-frame period of the light source in the common color sub-frame period is WBR, the image data conversion unit The common color distribution ratio defined as the ratio of the display light amount to be emitted in the common color sub-frame period to the display light amount of the common color component to be emitted in one frame period to display the pixel is approximately WBR / (1 + WBR) The image display according to claim 2, wherein driving image data corresponding to the plurality of subframe periods is generated by obtaining pixel data values in each of the plurality of subframe periods from the value of the pixel. apparatus.
The time from the start of the common color sub-frame period to the time when the light source of the first primary color starts lighting in the common color sub-frame period is the start color of the primary color sub-frame period corresponding to the other primary color When the light source in the sub-frame period is shorter than the time until the light source starts lighting, the light modulation unit generates an optical response when the light source of the first primary color starts lighting in the common color sub-frame period. In transient state,
The time from the start of the subsequent sub-frame period to the time when the light source of the second primary color starts lighting in the subsequent sub-frame period is the primary color sub-frame from the start of the primary color sub-frame period corresponding to the other primary color If it is shorter than the time until the light source starts lighting in the period, the light modulation unit enters an optical response transient state when the light source of the second primary color starts lighting in the subsequent subframe period. The image display apparatus according to any one of claims 1 to 3, wherein
The light modulation unit is capable of writing image data, and is configured to transmit or reflect light from the light source unit according to the written image data.
The light modulation unit drive circuit transmits the light modulation unit so that the image of the corresponding color is displayed by writing image data representing the image of the corresponding color in each sub-frame period to the light modulation unit. Control the rate or reflectance,
The light source unit drive circuit is configured to set the other primary color based on a light emission control reference time point preset as a time point after writing of the image data to the light modulation section is completed in each of the plurality of subframe periods. The lighting start time point of the light source in the primary color sub-frame period corresponding to is the light emission control reference time point, and the lighting start time point of the light source of the first primary color in the common color sub-frame period 4. The light source unit according to claim 1, wherein the light source unit is driven such that at least one of the lighting start times of the light source of the second primary color is earlier than the light emission control reference time in the subframe period. Image display device as described.
The light source unit drive circuit causes the light source of the first primary color to start lighting when the light modulation unit is in a transient state of the optical response in the common color subframe period, and the light in the subsequent subframe period. The light source of the second primary color starts to light when the modulator is in the transient state of the optical response, and the transient state of the optical response in the light modulator is ended in the primary color subframe period corresponding to the other primary color The image display apparatus according to claim 5, wherein the light source unit is driven such that the light source starts to light after being turned on.
The light source unit drive circuit is configured such that a first lighting time, which is a time during which the light source of the first primary color is on in the common color sub-frame period, is other than the first primary color in the common color sub-frame period. The image display apparatus according to any one of claims 1 to 5, wherein the light source unit is driven to be longer than another lighting time which is a time during which the light source of the other primary color is on.
The light source unit drive circuit is configured such that a second lighting time, which is a time during which the light source of the second primary color is on in the subsequent subframe period, is a difference between the first lighting time and the other lighting time. The image display apparatus according to claim 7, wherein the light source unit is driven so as to have a length corresponding to the first lighting time based on the above.
The light source unit driving circuit is configured to set the time during which the light source corresponding to the other primary color is on in each subframe period based on the difference between the first or second lighting time and the other lighting time. The image display apparatus according to claim 8, wherein the light source unit is driven to have a length corresponding to the first or second lighting time.
The light source unit drive circuit is configured to achieve the white balance while securing a non-lighting period according to the optical response characteristic of the light modulation unit in the primary color sub-frame period corresponding to the other primary colors. The image display apparatus according to any one of claims 1 to 5, configured to be capable of lighting a light source.
The light source unit drive circuit is configured such that the lighting time of the light source in the primary color sub-frame period corresponding to the other primary color is the maximum time that can avoid the color hue shift due to the optical response characteristic of the light modulation unit. The image display apparatus according to any one of claims 1 to 5, wherein
The light source unit drive circuit is configured such that a lighting time of a light source of a corresponding primary color in a primary color sub-frame period corresponding to a primary color other than the first primary color among the plurality of primary colors is the corresponding primary color in the common color sub-frame period. The image display apparatus according to any one of claims 1 to 5, wherein the light source unit is driven to be longer than a lighting time.
The light source unit drive circuit is configured such that, in the common color sub-frame period, a start time point of a lighting period of a light source of a primary color other than the first primary color is later than a start time of a lighting period of the first light source The image display device according to claim 12, wherein the light source unit is driven such that an end point of a lighting period of a light source of a primary color other than the first primary color coincides with an end point of the common color sub-frame period.
The light source unit driving circuit is configured such that, in the common color sub-frame period, the start time point of the lighting period of the light source of the first primary color coincides with the start point of the common color sub-frame period, and the light source of the first primary color The image display apparatus according to claim 12, wherein the light source unit is driven such that an end point of a lighting period of the light source period is earlier than an end point of the common color sub-frame period.
The image display device according to claim 12, wherein the light source unit drive circuit turns on the second light source only in the subsequent subframe period.
The light source unit drive circuit is configured such that, in the common color sub-frame period, a start time point of a lighting period of a light source of a primary color other than the first primary color is later than a start time of a lighting period of the first light source The image display device according to claim 14, wherein the light source unit is driven such that an end point of a lighting period of a light source of a primary color other than the first primary color coincides with an end point of the common color sub-frame period.
In the light source unit driving circuit, in the common color sub-frame period, the lighting period of the light source of the first primary color includes first and second lighting periods, and the start time point of the first lighting period is the common color The light source unit is driven such that it coincides with the start point of a subframe period, and the end point of the second lighting period coincides with the end point of the common color subframe period. The image display device according to
In an image display device including a light source unit including a plurality of light sources emitting light in a plurality of primary colors and a light modulation unit transmitting or reflecting light from the light source unit, a plurality of primary color subs respectively corresponding to the plurality of primary colors An image display method for displaying a color image according to a field sequential method in which each frame period includes a plurality of subframe periods each including a frame period and a common color subframe period.
A light source unit driving step of driving the light source unit such that light of a corresponding color is irradiated to the light modulation unit in each subframe period;
And d) a light modulation unit driving step of controlling the transmittance or reflectance of the light modulation unit so that an image of a corresponding color is displayed in each subframe period.
In the light source unit driving step, when the light source of the first primary color corresponding to the preceding subframe period which is the immediately preceding subframe period in the common color subframe period from the start point of the common color subframe period starts lighting And the time from the start of the subsequent subframe period which is a subframe period immediately after the common color subframe period to the time when the light source of the corresponding second primary color starts lighting in the subsequent subframe period Of at least one of the plurality of primary colors from a start point of a primary color sub-frame period corresponding to another primary color other than the first and second primary colors to a time point when the light source starts lighting in the primary color The image display method, wherein the light source unit is driven to be shorter than time.
When the input image data corresponding to the plurality of primary colors is received, the transmittance or the reflectance in the light modulation unit does not substantially change or decrease when the preceding subframe period is switched to the common color subframe period, and The plurality of subframe periods from the input image data such that the transmittance or the reflectance in the light modulator does not substantially change or increase when switching from the common color subframe period to the subsequent subframe period. Further comprising an image data conversion step of generating drive image data corresponding to
The light modulation unit driving step controls the transmittance or the reflectance in the light modulation unit so that an image of a corresponding color is displayed in each subframe period based on the driving image data. Image display method described in.