JPH11311971A - Monochromatic image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the number of steps of display gradation in a monochromatic image display device. SOLUTION: This device uses a display device which can express one pixel 4 of a monochromatic image with two pieces of cells 4a, 4b and in which the maximum output level of the cell 4a is 1 and the maximum output level of the cell 4b is 64. An intensity modulation means 2 controls impressed voltages to the respective cells 4a, 4b with 6-bits (64 steps) and also an area modulation means 3 controls inputs to the respective cells 4a, 4b by respectively turning on and off independently by the instruction from a controller 5 based on a monochromatic image signal SO. Since the maximum output level of the cell 4b is 64 times of that of the cell 4a and the gradation of the cell 4b is controlled in 64 steps by the intensity modulation means 2, the output level per one step of the cell 4b becomes to be one 64 th of the maximum output level of the cell 4b and it becomes to be the same as the maximum output level of the cell 4a. Thus, the final number of the steps of the display gradation of the display device can be made to be 64×64, that is, 4096 steps.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a monochrome image display device, and more particularly to an image display device in which the number of displayable gradations is increased by a simple method.

[0002]

2. Description of the Related Art As an image display device for displaying a monochrome image, an image display device using a cathode ray tube (CRT) is conventionally known. In addition, flat panel displays (FPDs) using liquid crystal panels, organic EL panels, and the like have been widely used today.
It is considered that it will spread more and more in the future because of its advantages such as space saving, light weight and low power consumption.

As a method of expressing the gradation of a monochrome image in this FPD, a method of inputting a luminance signal and expressing the gradation (so-called intensity modulation) is known. For example, in the case of using a liquid crystal panel as a display device, the on / off time of a switch per unit time such as pulse width modulation, frame thinning control or frame rate control (FRC) is controlled to control the unit. A method of performing gradation expression by changing a display period per time (so-called time-division driving) is known (for example, “Electronic Technology May Extra Issue (Vol. 32, No. 7); P110 to 121). , Flat panel display '91; P178 "), and a method of further increasing the number of display gradations of a monochrome image by combining this time-division driving and the above-described intensity modulation has been considered. For example, in the case of using the FRC method, the F
There has been proposed a method in which the number of stages is increased by 2 bits by the RC method, and an 8-bit gray scale (256 stages) can be displayed from a 6-bit gray scale signal.

[0004] Further, the applicant assigns one pixel of a monochrome image to a plurality of cells, and distributes a gradation corresponding to a monochrome image signal to each cell (referred to as "area modulation").
By time-modulating and / or intensity-modulating each cell so as to have the allocated gradation, the number of display gradations by the time modulation and / or intensity modulation is multiplied by the number of cells by the number of cells. (See Japanese Patent Application No. 10-98991). According to this area modulation, for example, if one pixel is represented by three cells,
8-bit gray scale (256
768 steps can be displayed.

[0005]

By the way, in displaying a medical image, in order to perform a highly accurate diagnosis, it is desired that the number of display gradations be 10 bits or more (1024 steps) or more. It is desired to obtain a large number of display gradations.

However, in the method of increasing the number of display gradations of a monochrome image by combining the above-described time-division driving and intensity modulation, the number of divisions per unit time is increased without limit due to the limit of the response speed of the liquid crystal. Can not
There is a certain limit to the method of increasing the number of gray scales in combination with time division driving, and it is difficult to further increase the number of display gray levels by combining time division driving and intensity modulation. Further, if the time-division driving is performed excessively, a flicker phenomenon occurs, and there is a problem that a practical display is not obtained.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a monochrome image display device capable of increasing the number of display gradation levels compared to the conventional one without causing a flicker phenomenon. It is assumed that.

[0008]

According to the monochrome image display device of the present invention, one pixel of a monochrome image can be represented by a combination of a plurality of cells having a plurality of display gradation levels, and the plurality of cells can be displayed. A display device in which at least two cells have different maximum output levels from each other;
And a driving means for driving the two cells so that the output levels per display gradation of the two cells are different from each other.

In this monochrome image display device, 2
If the maximum output level of one of the cells is made substantially the same as the output level per stage of the other cell, the number of display gradation levels can be greatly increased.

It is desirable that the driving means of the monochrome image display device drives the two cells so that each of them has substantially the same number of display gradations.

As a display device of the monochrome image display device according to the present invention, a liquid crystal panel having different maximum output levels of two cells by forming monochromatic filters having different transmittances on two cells, It is preferable that the cells are organic EL panels that emit light of the same color at different light emission luminances.

[0012]

According to the monochrome image display device of the present invention, one pixel of a monochrome image can be represented by a combination of a plurality of cells, and at least two of the plurality of cells have different maximum output powers. In addition to using a display device having levels, the two cells are driven such that the output levels per stage of the display gradation of the two cells are different from each other, so that the output level per stage is large. The gradation level between each stage of the other cell can be displayed in the other cell having the lower output level, and the number of display gradations should be increased by the amount capable of displaying the gradation level between each stage. Can be. Further, since the number of stages of display gradation is not increased by the time division driving, the problem of the flicker phenomenon does not occur.

Here, the fact that the present invention can increase the number of display gradation steps will be described in detail with reference to the conceptual diagram shown in FIG. FIG. 1A shows one pixel of a display device used in an image display device according to the present invention, and one pixel of a monochrome image is represented by a combination of two cells a and b. . FIGS. 1B and 1C show the maximum output levels of the two cells and the display gradations of each cell, and the total display gradations of both cells when viewed as one pixel. Is schematically shown. It should be noted that the display gradation steps for one pixel having a level a4 or more obtained by adding each level of the cell b to the level a4 of the cell a are omitted (the same applies to FIGS. 2 and 3 described later). Is.).

In FIG. 1B, the gradation level of the cell a is four steps of a1 to a4 except for the 0 level, and the gradation level of the cell b is two steps of b1 and b2 except for the 0 level. In each stage, the respective maximum output levels a4 and b2 are equally distributed. The highest output level of cell b, ie, level b2, is smaller than the highest output level of cell a, ie, level a4, which is the same as level a3. In this way, when viewed as one pixel, a gradation level in which the level b1 of the cell b is filled can be expressed between the stages of the cell a except for 0 to a1. Become like This is because, when viewed as one pixel, the gradation level can be represented by adding the output level of each cell.

Similarly, in FIG. 1C, the gradation level of the cell a is four steps of a1 to a4 except for the 0 level, and the gradation level of the cell b is b1 to b6 except for the 0 level. The maximum output levels a4 and b6 are equally distributed between the respective stages. The highest output level of cell b, that is, level b6, is smaller than the highest output level of cell a, that is, level a4, and this level b6 is the same as level a3. By doing so, when viewed as one pixel, it is possible to express a gradation level in which the level b1 of the cell b is buried between the stages of the cell a.

In the present invention, "the output levels per stage of the display gradation of the two cells are different from each other."
The reason for this is that if the output level per stage is the same, as shown in FIG. 1 (D), the cell b with the lower output level fills the space between the cells a with the higher output level. This is because the number of display gradation steps cannot be increased.

Also, in the monochrome image display device according to the present invention, if the maximum output level of one of the two cells is made equal to the output level per stage of the other cell, each of the other cells can be obtained. Since the steps can be completely filled with the gradation display by one cell, the gradations can be finely displayed between the steps, and the number of display gradation steps can be dramatically increased. Furthermore, if two cells are driven so as to have substantially the same number of display gray levels, each cell can be driven by a signal having the same number of bits. A readily available drive circuit can be used as it is.

Here, the point that the number of display gradation steps can be dramatically increased will be described in detail with reference to the conceptual diagram shown in FIG. In FIG. 2B, the gradation level of the cell a is four steps of a1 to a4 except for the 0 level, and the gradation level of the cell b is two steps of b1 and b2 except for the 0 level. The maximum output levels a4 and b2 are evenly distributed between the stages. The highest output level of cell b, that is, level b2, is smaller than the highest output level of cell a, that is, level a4. This level b2 is the same as the output level per cell a, that is, level a1. In this way, when viewed as one pixel, it is possible to express a gradation level in which the level b1 of the cell b is buried between the stages of the cell a. When the number of display gray levels of the cell b is two as shown in FIG. 2B, the number of steps is increased as in the case shown in FIG. 1C. Therefore, FIGS. 2C and 2D show a case where the number of display gradations of the cell b is further increased in order to dramatically increase the number of display gradations.

FIG. 2C shows that the number of display gradations of cell b is three.
FIG. 2 (D) also shows a four-stage structure. As described above, the maximum output level of the cell b is made the same as the output level per one step of the cell a, and the number of display gradations of the cell b is increased, so that the cell b is more finely divided between the cells a. , And the number of display gradation steps when viewed as one pixel can be dramatically increased.

In the present invention, it is not always necessary to represent one pixel by two cells, but one pixel is represented by, for example, FIG.
It is needless to say that three cells a, b, and c may be used as shown in FIG. In FIG. 3, cell a
Are four levels a1 to a4 except for the 0 level.
The gradation level of the cell b is four stages of b1 to b4 except for the 0 level, and the gradation level of the cell c is two stages of c1 and c2 except for the 0 level. Level a4, b4, c2
Are evenly distributed. The highest output level of cell b, ie, level b4, is smaller than the highest output level of cell a, ie, level a4, and this level b4 is the same as level a1. The highest output level of cell c, ie, level c2, is the highest output level of cell b, ie, level b4.
And the level c2 is the same as the level b1.
By doing so, when viewed as one pixel, a gradation level in which the level c1 of the cell c is buried can be expressed between the stages of the cell b. Between each stage, it is possible to express a gradation level in which the level of the cell b or the combination of the cell b and the cell c is filled.

As the display device of the monochrome image display device according to the present invention, a monochromatic filter having a different transmittance is formed on two cells, so that a liquid crystal panel having different maximum output levels of the cells or two liquid crystal panels. It is preferable that the cells are organic EL panels that emit light of the same color at different light emission luminances.

In the present invention, a liquid crystal panel having the same structure as that of the color liquid crystal panel from which the color filters are removed can be used as a display device. That is, if the color filter forming step is omitted in the manufacturing process of the color display liquid crystal panel, a monochrome liquid crystal panel in which one pixel is composed of three cells can be obtained. Without the cost burden of
It can be manufactured very easily. Also,
The liquid crystal driver (controller) for controlling the gradation of the liquid crystal panel can also control the gradation of the monochrome image using the existing color liquid crystal driver.

Further, by forming monochromatic filters having different transmittances on the two cells as a display device,
If a liquid crystal panel having a different maximum output level of the cell is used, its manufacture becomes easy. That is, in the manufacturing process of the liquid crystal panel for color display,
If a single color filter having a different transmittance is formed on two cells using a current color filter mask, a liquid crystal panel having one pixel formed of two cells can be obtained. The panel can be manufactured very easily without incurring any extra cost such as new development of a mask. Also, a liquid crystal driver (controller) for controlling the gradation of the liquid crystal panel can control the gradation of the monochrome image using the existing color liquid crystal driver.

If the display device is an organic EL panel in which two cells emit light of the same color at different light emission luminances, it is not necessary to form a monochromatic filter on each cell as in a liquid crystal panel, and light emission of the same color is performed. A panel formed by arranging a large number of organic ELs that emit light with different luminances can be obtained.

If a liquid crystal panel having a monochromatic filter exhibiting a bluish color or an organic EL panel emitting a bluish color is used, a blue-based monochrome image display device suitable for a medical site can be obtained. .

[0026]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 4 shows a monochrome image 1
1 shows one pixel of the image display device 1 using the display device 4 that can represent a pixel by two cells 4a and 4b. The highest output level of the cell 4a of the display device 4 is 1, and the highest output level of the cell 4b is 65.

This image display device 1 is used to generate a monochrome image signal.
Intensity modulation means 2 for controlling the voltage applied to each cell 4a, 4b by 6 bits, that is, 64 stages (actually 63 stages excluding level 0) based on S0 (one corresponding to each cell 2a, 2b Driving means 6 comprising area modulating means 3 for controlling the input to each cell by turning on and off the output of the intensity modulating means 2 independently (each corresponding to each cell is referred to as 3a, 3b). And a controller 5 for controlling the intensity modulating means 2 and the area modulating means 3 based on the image signal S0 such that the display gradation of one pixel becomes a desired level. It goes without saying that the display gradation level of each cell changes when the intensity modulating means 2 controls the printing voltage to each cell. Since the intensity modulation means 2b controls the gradation of the cell 4b in 63 steps, the output level per cell 4b is 1/63 of the maximum output level of the cell 4b, and the maximum output level of the cell 4a. Is 1/64 of that of the cell 4b, so that the output level per stage of the cell 4b is substantially the same as the maximum output level of the cell 4a. Note that, as is clear from FIG. 5, the maximum output level of the cell 4a is equal to the maximum output level of the cell 4b.
It is smaller than the output level per stage by the output level per stage of the cell 4a.

FIG. 5 is a diagram showing the number of levels of display gradation of the image display device 1. As shown in FIG. As is clear from FIG. 5, the gradation level of one pixel is represented by the gradation level of the cell 4b and the gradation level of the cell 4a which fills the space between the cells 4b. Therefore, in this example, the intensity modulation means 2
Since the cell 4a and the cell 4b are each gradation controlled by 6 bits by a and 2b, the final number of display gradations is 6 bits (64) × 6 bits (64), that is, 4096 steps. it can.

Next, as a display device, a color filter of a color liquid crystal panel capable of representing one pixel of a monochrome image by three cells is used.
An image display device 10 using a liquid crystal panel 40 in which monochromatic filters having different transmittances are formed on one cell will be described. FIG. 6 is a diagram showing an example of a pixel array of the liquid crystal panel 40. As shown in FIG. 6, in the liquid crystal panel 40, each pixel such as pixel numbers 41, 42, 43, and 44 can be represented by a plurality of cells (for example, 41a, 41b, and 41c for the pixel number 41). It is configured to be able to. The maximum output level of each cell a and c of the liquid crystal panel 40 is 1, and the maximum output level of cell b is 64.

The image display device 10 outputs a monochrome image signal.
Based on S0, the voltage applied to each cell 41a, 41b, 41c is increased by 6
The intensity modulating means 20 which can be controlled by 64 bits, that is, controllable by each cell (the one corresponding to each cell is 20a, 20b, 20c) and the output of the intensity modulating means 20 are turned on and off independently to input to each cell. The driving means 60 comprising the area modulation means 30 to be controlled (each corresponding to each cell is referred to as 30a, 30b, 30c), and the display gradation of one pixel becomes a desired level based on the image signal S0. And a controller 50 for controlling the intensity modulating means 20 and the area modulating means 30. Note that the intensity modulation means 20c for the cell 41a operates because only the upper one bit of the six bits gives the level 32,
It is controlled almost by the lower 5 bits. Also, cell 41
The intensity modulation means 20c for c does not use the upper one bit of the six bits, but actually controls the lower five bits. The maximum output level of the cell 41b is 64 times that of the cells 41a and 41c, and the gray level of the cell 41b is controlled in 64 steps by the intensity modulation means 20b. Since the output level is 1/64 of the maximum output level of the cell 41b, if the control is performed in 64 stages by the cells 41a and 41c as described later, the output level per stage of the cell 41b will be the output level of each of the cells 41a and 41c. It will be the same as the composite level.

FIG. 8 is a diagram showing the number of levels of display gradation of the image display device 10. As shown in FIG. As is clear from FIG. 8, the gradation level of one pixel is represented by the gradation level of the cell 41b and the gradation level filling each space of the cell 41b by combining the cells 41a and 41b. Therefore, in this example, the gradation between the 64 stages by the cell 41b is controlled by the 32 stages by the cell 41a, the 31 stage by the cell 41c, and the 64 stages by synthesizing the level 0 thereof. The number of key steps is 64 × 64, that is, 4096 steps.

As described above, when one pixel is represented by three cells, at least two cells have different maximum output levels from each other, and the output level per display gradation of the two cells is reduced. If they are different from each other,
The number of display gradation levels of one pixel can be increased. In addition,
So that all three have different maximum output levels,
If the output levels per stage of the display gradation of each of these cells are different from each other, the number of stages of the display gradation can be further increased.

As shown in FIG. 5, 4096 levels of gradation can be expressed by combining two cells having the highest output levels 1 and 64. For example, the pixel of the liquid crystal panel 40 shown in FIG. As shown in FIG. 9, a cell 41a having a maximum output level of 1 and a cell 41b having a maximum output level of 64, a cell 41c having a maximum output level of 1 and a cell 41c having a maximum output level of 1 are used as shown in FIG. If 64 cells 42a, a cell 42b having a maximum output level of 1 and a cell 42c having a maximum output level of 64 are provided, and each of the intensity modulation means is fully controlled by 6 bits,
In color display, what displayed two pixels in six cells can be changed to monochrome display of three pixels, and resolution can be increased.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram illustrating a method of the present invention for increasing the number of display gradation steps.

FIG. 2 is a conceptual diagram illustrating another method of the present invention for increasing the number of display gradation steps.

FIG. 3 is a conceptual diagram illustrating still another method of the present invention for increasing the number of display gradation steps.

FIG. 4 is a block diagram illustrating a configuration of a monochrome image display device according to an embodiment of the present invention for one pixel of a liquid crystal panel.

FIG. 5 is a diagram showing the number of display gradation steps of the image display device.

FIG. 6 is a diagram showing a pixel configuration of a liquid crystal panel used in a monochrome image display device according to another embodiment of the present invention.

FIG. 7 is a block diagram showing the configuration of the monochrome image display device for one pixel of a liquid crystal panel.

FIG. 8 is a diagram showing the number of display gradation levels of the image display device.

FIG. 9 is a block diagram showing a configuration of a monochrome image display device according to another embodiment of the present invention, in which resolution is increased, for two pixels of a color liquid crystal panel.

[Explanation of symbols]

 1,10,12 monochrome image display device 2,20,22 intensity modulation means 3,30,32 area modulation means 4,40 display device (liquid crystal panel) 5,50,52 controller

Claims (5)

[Claims] 1. A pixel of a monochrome image can be represented by a combination of a plurality of cells having a plurality of display gradation levels, and at least two of the plurality of cells have different maximum output levels. A monochromatic image display device comprising: a display device having a plurality of cells; and a driving unit for driving the two cells such that output levels per stage of the display gradation of the two cells are different from each other. 2. The system according to claim 1, wherein the highest output level of one of the two cells is substantially the same as the output level per stage of the other cell.
The monochrome image display device described in the above. 3. The monochrome image display device according to claim 2, wherein said driving means drives said two cells so that each of them has substantially the same number of display gradations. 4. The display device according to claim 1, wherein the display device forms monochromatic filters having different transmittances on the two cells,
4. The monochrome image display device according to claim 1, wherein the liquid crystal panel has a different maximum output level of the cell. 5. The monochrome image display device according to claim 1, wherein the display device is an organic EL panel in which the two cells emit light of the same color at different light emission luminances.