JP2000352701A - Image display method in liquid crystal device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To reduce blur interference and color breakup without requiring a complicated circuit or the like. SOLUTION: In each subfield in which R, G, and B light emission is sequentially performed, a period for turning on all of R, G, and B is provided. As a result, since a white image is created in the combined image of the entire field, a complicated circuit or the like for creating new image data is not required, and blur interference and color breakup can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for displaying a color image on a liquid crystal device.
The liquid crystal element is sequentially irradiated with each of the R, G, and B color lights, and light is switched in the liquid crystal element in synchronization with the light, so that the R, G, and B images are sequentially displayed. The present invention relates to an image display method in a liquid crystal device for displaying an image.

[0002]

2. Description of the Related Art Conventionally, a color image display is performed by a liquid crystal device. As a method of displaying a color image, two methods described below are known.

A method of continuously irradiating a liquid crystal element provided with a color filter with white light. Only one color of the color filter (one of R, G, and B colors) corresponds to each pixel of the liquid crystal element. Each pixel is divided and arranged (space division) so as to be indistinguishable by the eyes, and the R, G, and B color lights from these pixels are mixed using juxtaposed additive color mixing and recognized as a color image.

The method will be described with reference to FIG. FIG.
FIG. 1 is a schematic diagram showing an example of a conventional liquid crystal device that performs image display by the method. The liquid crystal device includes a light source 1 that emits R, G, and B color lights, a liquid crystal element 3, and an image switching unit 2 provided in the liquid crystal element 3. When displaying an image, the light source 1 irradiates the R, G, and B color lights to the liquid crystal element 3 sequentially (in a time-division manner), and synchronizes with the irradiation of each color light by the image switching means 2. At 3, light switching is performed. The R, G, and B color lights from the liquid crystal element 3 are mixed using successive additive color mixing, and are recognized as a color image. This method is known from Japanese Patent Publication No. 63-41078.

[0005] Among the above methods, one pixel of the liquid crystal element can display three colors of R, G, and B, so that a high-definition image can be displayed.

[0006]

A. Problem to be Solved by the Invention However, the above method has the following problems.

(A) There is a problem of blurring. The problem will be described with reference to FIG. FIG. 4A is a diagram illustrating blurring disturbance. As shown in FIG.
It is assumed that the image G has moved rightward on the drawing sheet from time to time n + 1. When the image G is followed by the eyes, blur occurs at both ends (hatched portions in the drawing) of the moved image G due to the afterimage phenomenon of the eyes. In this manner, blurring of a moving image due to the detected eye speed is referred to as blurring obstruction. (Note that this problem also occurs when the above method is adopted).

[0008] For example, this problem can be solved by the IEICE Transaction '85
/ 12 Vol.J68-B No.12, "Motion blurring in hold-type image display" has been pointed out. Will be done. "

[0009] Recently, a quantitative evaluation of blurring interference has also been made. For example, IEICE Technical Report EID96-4 (1996-0
In 6), "Study on Moving Picture Quality of Hold Light Emitting Display Using 8x CRT" states that "in the case of the hold type, the evaluation is below the permissible limit at a speed of 13.6 deg / sec."

(B) There is a problem of color breakup. The problem will be described with reference to FIG. FIG. 4B is a diagram illustrating color breakage. As shown in FIG. 4B, it is assumed that the image G has moved rightward on the drawing from time n to time n + 1. When this image G is visually followed, the moved image G
At both ends (shaded portions in the figure), the color displayed before the movement remains due to the afterimage phenomenon of the eyes, and this is mixed with the color displayed after the movement, resulting in a blurred state. Is recognized. Such a problem is referred to as color breakup (this problem occurs only when the above method is employed).

This color breakup is also a problem caused by the detected eye speed of a moving image. This problem is discussed in
No. 41023, JP-A-8-248381, JP-A-8-248
317380, JP-A-8-101672, JP-A-9
No.-90916 and the like (in some of these documents, "color break" is referred to as "color shift", but both are synonymous).

B. Various solutions have been devised to solve the above-mentioned problems, but each involves another problem as described below.

(I) Japanese Patent Publication No. 7-41023 proposes a detection device using an electric circuit as a countermeasure for color breakage, but it requires a complicated circuit and is not suitable for high-speed moving image processing. There is a problem that is.

(Ii) In Japanese Unexamined Patent Publication No. Hei 8-248381, the temporal order of color signals in a field is changed. In particular, the color of the last color signal in one cycle is the same as the color of the first color signal in the next cycle. It has been proposed to. However, other color data has a problem that the frame frequency becomes longer and flickers appear.

(Iii) In JP-A-8-317380,
It has been proposed that 3: 1 interlaced scanning be performed, and that colors be different at the same scanning line position. However, there is a problem that the circuit system becomes complicated by using a special scanning method.

(Iv) In Japanese Patent Application Laid-Open No. 8-101672, RGB
Although it has been proposed to generate and use an achromatic signal calculated from a signal, it is necessary to create new image data, and there is a problem that a circuit becomes complicated.

(V) In Japanese Patent Application Laid-Open No. 9-90916, RGB
It has been proposed to form a subfield of the same period of white or intermediate color in addition to the field, but it is necessary to create new image data, which complicates the circuit and creates a newly created subfield. The data of the subfield has a problem that the characteristics of the image are deteriorated.

C. Of the above-described devices (i) to (V), (iv) and (v) for inserting a white image or the like can be used for high-speed moving image processing, and furthermore, there is no flicker or the like, and special scanning is performed. Although it is excellent in that it does not need to use a method, it is necessary to create new image data relating to a white image or the like, and there is still a problem in that the circuit becomes complicated.

In view of the above circumstances, it is an object of the present invention to provide an image display method in a liquid crystal device that does not require a complicated circuit or the like and can reduce blurring and color breakup.

[0020]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a light source for illuminating first, second, and third color lights, which are three primary colors of light, and a liquid crystal for switching light received from the light source. A first step of turning on the first color light, a second step of turning on the second color light, and a third step of turning on the third color light by the light source using a liquid crystal device including the element. Are sequentially performed, and the liquid crystal element performs light switching in synchronization with the first, second, and third steps, so that an image of a first color is formed in the first step. In the image display method, an image of the second color is displayed at the time of the second step, and an image of the third color is displayed at the time of the third step, wherein the first step turns on only the first color light. And simultaneously lighting all the other second and third color lights together with the first color light The second step includes a step of lighting only the second color light, and a step of simultaneously lighting all of the other first and third color lights together with the second color light. The method comprises the steps of: lighting only the third color light; and simultaneously lighting all of the other first and second color lights together with the third color light. is there.

The ratio of the period for performing the step of simultaneously irradiating all of the first to third color lights in the period for performing the first, second, and third steps is 1/10 or less. And 1/50 or more.

Further, according to the above arrangement, the liquid crystal element is irradiated with white light by simultaneously irradiating all of the first to third color lights. That is, the colors mixed in the light emission in the first to third steps are a composite color of white, first color, white, second color, white, and third color.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. It is assumed that the basic configuration of the liquid crystal device used in the embodiment of the present invention is substantially the same as the basic configuration of the liquid crystal device shown in FIG. 3 described in “Prior Art”.

FIG. 1 is a timing chart relating to irradiation of light from a light source. In FIG. 1, one field is a period during which one frame of image is displayed.
A field is divided into three equal parts, and a first SF (subfield), a second SF (subfield), and a third SF (subfield) are set. That is, when an image is displayed using a plurality of fields, the first SF, the second SF, and the third SF are sequentially repeated.

When a color image is displayed by this liquid crystal device, the light source 1 irradiates the liquid crystal element 3 with red light (R) in the first SF and irradiates green light (G) in the second SF. In the third SF, blue light (B) is applied. Here, red (R), green (G), and blue (B) are the three primary colors of light. On the other hand, in synchronization with each SF, light is switched in the liquid crystal element 3 by the image switching means 2. As a result, a red image is displayed in the first SF, a green image is displayed in the second SF, and a blue image is displayed in the third SF. The images of these colors are mixed by successive additive colors, and a full-color image is formed as a whole of one field. Will be recognized as

In the first SF, in addition to the step of irradiating only red light, a step of simultaneously irradiating all of red, green, and blue lights is performed so as to be interposed in the middle of the step. In the second SF, in addition to performing the step of irradiating only green light, so as to intervene in the middle of the step,
A step of simultaneously irradiating all of red, green, and blue light is performed. In the third SF, in addition to performing the step of irradiating only blue light, a step of simultaneously irradiating all of red, green, and blue light is performed so as to be interposed in the middle of the step.

As described above, in each SF,
When all the red, green, and blue lights are simultaneously irradiated, the light source 1 irradiates the liquid crystal element 3 with white light. That is, 1
In the field, a white image is displayed while a red image is being displayed, a white image is being displayed while a green image is being displayed, and a white image is being displayed while a blue image is being displayed. For example, as shown in FIG. 1, one field is a composite color of white, red, white, green, white, and blue.

By the way, as described in "Problems to be Solved by the Invention", it is known that it is effective to insert a white image in order to reduce blurring or color breakup caused by movement of the line of sight. Has become. That is, in the present embodiment, as described above, by creating a white image in a composite image in one field, blur interference and color breakup can be effectively reduced.

In the present embodiment, it is not necessary to create data for a white image to be displayed on the liquid crystal element 3 separately from data for each color image of red, green and blue. This eliminates the need to separately create data for a white image unlike the related art, and does not require a complicated circuit.

[0030]

Embodiments of the present invention will be described below. In this embodiment, the light source 1 is a Ne gas discharge tube as a red single wavelength tube, a cold cathode fluorescent tube using a SrAl ₂ O ₄ : Eu ²⁺ phosphor as a green single wavelength tube, and a BaMgAl ₁₆ O as a blue single wavelength tube. ₂₇ :
A cold cathode fluorescent tube using Eu ²⁺ phosphor was used. The main characteristics of the light source 1 are shown in Table 1 below.

[0031]

[Table 1] FIG. 2 is a CIE chromaticity diagram, in which a is a “prior art”.
The color reproducibility of a TFT liquid crystal device that displays a color image by the method described in (1), b is the color of the liquid crystal device that displays a color image by the method described in “Prior Art” (no white image is inserted). The reproducibility is shown. As is clear from the figure, the color reproducibility b is superior to the color reproducibility a. When displaying a color image by the method, the color filter formed on the liquid crystal element must be designed to match the spectral transmittance characteristics of the light source, whereas the color image by the method must be designed. This is because, in the case where is displayed, it is possible to select a single-wavelength light source having high purity, for example, because only the color design of the light source is required. The color reproducibility b can be represented by the following equation.

The optical characteristics of the R, G, and B light emitting portions of the light source are represented by R light emitting portions: (x _R , y _R , Y _R ), G
Light emitting unit: (x _G , y _G , Y _G ), B light emitting unit: (x _B , y
_B , Y _B ), the first, second, and
When the third SF is equally divided, D _R = D _G = D _B = 1 /
Therefore, in the case of the present embodiment relating to the image display method of the present invention, the total lighting duty of R, G, B is set to n (0 <n
If <1>, the R light emitting portion: (x _R , y _R , Y _R × (1
+ 2n) / 3), G light-emitting portion: (x _G , y _G , Y _G × (1
+ 2n) / 3), B light emitting _{portion: (x B, y B,} Y B × (1
+ 2n) / 3).

Accordingly, the optical characteristics of additive color mixture can be expressed as follows.

X = x _R × (Y _R × (1 + 2n) / 3) / y _R + x _G × (Y _G × (1 + 2n) / 3) / y _G + x _B × (Y _B × (1 + 2n) / 3 / _{y B) / ((Y R} × (1 + 2 n) / 3) / y R + (Y G × (1 + 2n) / 3) / y G + (Y B × (1 + 2n) / 3 / y B) ...... formula _{1 y = ((Y R ×} (1 + 2n) / 3) + (Y G × (1 + 2n) / 3) + (Y B × (1 + 2n) / 3)) / ((Y R × (1 + 2n) / 3) / y _R + (Y _G × (1 + 2n) / 3) / y _G + (Y _B × (1 + 2n) / 3 / y _B ) Formula 2 Y = (Y _R × (1 + 2n) / 3) + (Y _{G × (1 + 2n) /} 3) + (Y B × (1 + 2n) / 3) ...... equation 3 the way, blur interference or color breakup of a moving image as described above becomes conspicuous white image is relatively in black background When moving at high speed, The case where the data was white was verified.

Since a white image is displayed, the liquid crystal element is turned on (transmitted) for the entire period.
It becomes the optical characteristics of the liquid crystal device as it is. That is, in the case of a white image, the chromaticity did not change from Expressions 1 and 2, and the luminance was (1 + 2n) times from Expression 3.

Next, as a case of a single color, a case where only the red light in the first SF is in a transmission state was examined. In this case, white light is emitted during the R, G, and B full lighting periods of the first SF, and red light is emitted during the remaining periods, and the above equations 1, 2, and 3 are expressed by the following equations 1 ′, 2 ′, and 3 ′. Become like

[0037] _{x = (x R × Y R} / y R + x G × Y G × n / y G + x B × (Y B × n / y B)) / ((Y R × / y R + (Y G _{× n) / y G + (} Y B × n / y B)) ...... formula _{1 'y = ((Y R} ) + (Y G × n) + (Y B × n) / ((Y R) / _{y R + (Y G × n} ) / y G + (Y B × n) / y B) ...... formula _{2 'Y = (Y R ×} 1/3) + (Y G × n / 3) + (Y _B × n / 3) Equation 3 ′ Equations 1 ′, 2 ′, and 3 ′ represent a change in chromaticity and an improvement in luminance, and how to set the chromaticity change is important. In the present embodiment, a quantitative evaluation was performed by simulation and ergonomic evaluation to determine how long a period in which a white image is displayed in a part of each subfield (SF) should be set in the period of each subfield. The results are shown in Table 2.

[0038]

[Table 2] In Table 2 above, the optical evaluation is a still image, the color breakup evaluation is a moving image, and the moving image is visually evaluated and evaluated on a five-point scale. “○” indicates no problem, “△” indicates acceptable, and “×” indicates Indicates unacceptable. As shown in Table 2, the results of the optical evaluation of the still image and the results of the color breakage of the moving image are in a trade-off relationship, and both are acceptable when n is 1/10 or less and 1/50 or more. Turned out to be the case.

In this embodiment, the field frequency 6
0 Hz (period of one field is about 16.6 msec.), Sub-field frequency of 180 Hz (period of one sub-field is about 5.5 msec.), R, R in one sub-field
When the ratio of the period in which G and B are fully lit is n = 1/10, the total lighting period is 550 μsec. And n = 1/5.
When it was set to 0, the entire lighting period was 111 μsec. This could be handled from the optical response characteristics of the light source shown in Table 1.

[0040]

As described above, according to the present invention,
When all the red, green, and blue lights are simultaneously irradiated, the light source 1 irradiates the liquid crystal element 3 with white light. That is, in each of the first, second, and third steps, a white image is displayed while a red image is displayed, a white image is displayed while a green image is displayed, and a blue image is displayed while a blue image is displayed. Respectively, the white images are displayed, so that a white image is created in the composite image in the first to third steps as a whole. Thereby, blur interference and color breakup can be effectively reduced.

In the present invention, it is not necessary to create data for a white image to be inserted separately from data for red, green, and blue color images. This eliminates the need for a complicated circuit as in the related art.

[Brief description of the drawings]

FIG. 1 is a timing chart illustrating an embodiment of the present invention.

FIG. 2 is a C.I.E.1931xy chromaticity diagram.

FIG. 3 is a schematic diagram illustrating a basic configuration of a liquid crystal device.

FIG. 4 is a conceptual diagram illustrating blurring obstruction and color breakup.

[Explanation of symbols]

n Ratio of all R, G and B lights in each subfield (SF)

Claims (2)

[Claims] 1. A liquid crystal device comprising: a light source for lighting first, second, and third color lights of three primary colors of light; and a liquid crystal element for switching light received from the light source. A first step of turning on the first color light, a second step of turning on the second color light, and a third step of turning on the third color light are sequentially performed. By performing light switching in synchronization with the second and third steps, the first
The image of the first color during the step of
The image of the third color at the time of the third step,
In the image display method for displaying each, the first step is a step of lighting only the first color light;
A step of simultaneously illuminating all of the other second and third color lights together with the first color light, the second step of illuminating only the second color light;
A step of simultaneously lighting all the other first and third color lights together with the second color light, wherein the third step is a step of lighting only the third color light;
An image display method in a liquid crystal device, comprising a step of simultaneously lighting all of the other first and second color lights together with the third color light. 2. A ratio of a period for performing the step of simultaneously lighting all of the first to third color lights in a period for performing the first, second, and third steps to be 1/10 or less. And 1
The image display method in the liquid crystal device according to claim 1, wherein the ratio is not less than / 50.