JP3608557B2 - Image display device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is a digital display device, particularly a plasma display that performs gradation display based on a subfield driving method, and generates a halftone display disorder that is likely to occur when a moving image is displayed, that is, a so-called moving image pseudo contour. The present invention relates to an image display device that improves the above.
[0002]
[Prior art]
Usually, a plasma display performs halftone display by a driving method called a subfield method. Each subfield is selected according to the input digital value, and the average amount of light emission in one field is controlled to be proportional to the input digital signal value. FIG. 6 is a diagram showing the concept of light emission by driving by this subfield method.
[0003]
As shown in FIG. 6, SF0 to SF4 indicate subfields, and the luminance weight of each subfield is set to match the bit weight of the digital signal. FIG. 6 shows the light emission state of each subfield in each of the luminance levels 14, 15 and 16, and the shaded portion indicates the subfield that emits light.
[0004]
[Problems to be solved by the invention]
As can be seen from the figure, when the luminance level changes from 14 to 15, the light emission pattern changes only in SF0, and the temporal distribution of light emission changes slightly. Not observed.
[0005]
On the other hand, when the luminance level changes from 15 to 16, the light emission / non-light emission of all the subfields are reversed although the luminance level change is only 1. For this reason, the temporal distribution of light emission is also greatly changed, and when a moving image is displayed and the line of sight is tracked, a phenomenon called a moving image pseudo contour occurs, which is a serious factor of image quality degradation.
[0006]
[Means for Solving the Problems]
In order to solve the above problems, an image display apparatus according to the present invention includes a plurality of nonlinear conversion means having an input image signal as a common input and having nonlinear characteristics in a limited range of a signal level of the input image signal, and the input A selection unit that selects an image signal or one of the outputs of the plurality of nonlinear conversion units; a selection signal generation unit that controls the selection unit; and a digital image display unit that receives the digital value of the output of the selection unit. And the selection signal is generated so that a characteristic obtained by averaging the outputs of the selection means temporally or spatially becomes a substantially straight line.
[0007]
The image display apparatus of the present invention is characterized in that the plurality of nonlinear means have nonlinear characteristics in the vicinity of a digital value of the digital display means in the vicinity of a value that is an integral multiple of a power of two.
[0008]
The image display apparatus of the present invention is characterized in that the plurality of nonlinear means have nonlinear characteristics in a range in which a digital value of the digital display means does not exceed an integral multiple of a power of 2.
[0009]
Further, the present invention is characterized in that the selection signal generating means selects and passes the input image signal in a portion where the level of the input image signal is flat in the screen.
[0010]
According to the present invention, the non-linear characteristic is switched and selected in a limited range of the signal level of the input image signal, for use in an image display device such as a plasma display using the subfield method and the like in which a moving image pseudo contour is likely to occur. Therefore, it is possible to suppress the occurrence of side effects and to suppress the generation of moving image pseudo contours.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
An image display device according to the present invention (Aspect 1) includes a plurality of nonlinear conversion means having an input image signal as a common input and having nonlinear characteristics in a limited range of the signal level of the input image signal, and the input image signal or A selection means for selecting one of the outputs of the plurality of nonlinear conversion means; a selection signal generation means for controlling the selection means; and a digital image display means for inputting a digital value of the output of the selection means, The selection signal is generated so that a characteristic obtained by averaging the outputs of the selection means temporally or spatially becomes a substantially straight line.
[0012]
For this reason, only the vicinity of the signal level at which the moving image pseudo contour is likely to occur can be equivalently amplitude-modulated to the input signal to disperse the generation of the moving image pseudo contour and make it inconspicuous. In addition, since nonlinear processing is performed only in a limited range of the signal level of the input image signal, it is possible to reduce the frequency of occurrence of a side effect that a pattern such as a checkered pattern is observed on the screen.
[0013]
In the image display device of the present invention (claim 2), the plurality of non-linear means have non-linear characteristics when the digital value of the digital display means is in the vicinity of an integer multiple of a predetermined power of two. And For this reason, the input image signal is equivalently subjected to amplitude modulation only in the portion where the moving image pseudo contour is likely to occur, that is, in the vicinity of the value where the signal level of the input image signal is an integral multiple of a power of 2. It is possible to suppress the occurrence of pseudo contours and limit a portion to which equivalent amplitude modulation is performed, thereby reducing the frequency of occurrence of a side effect that a pattern such as a checkered pattern is observed on the screen.
[0014]
In the image display device of the present invention (Claim 3), the plurality of nonlinear means have nonlinear characteristics in a range in which a digital value of the digital display means does not exceed an integer multiple of a power of 2. . For this reason, the generation of moving image pseudo contour is suppressed by equivalently performing amplitude modulation on the input image signal at a portion where the moving image pseudo contour is likely to occur, and the portion subjected to equivalent amplitude modulation is further narrowed. The frequency of the side effect that a checkerboard pattern or the like is observed on the screen can be reduced.
[0015]
In the image display device according to the present invention (claim 4), the selection signal generating means selects and passes the input image signal in a portion where the level of the input image signal is flat in the screen. It is characterized by that. For this reason, since there is no change in the image, even if it is a moving image portion, in principle, an equivalent modulation is not applied to a portion where a moving image pseudo contour is hardly generated, and a pattern such as a checkered pattern is observed on the screen. The frequency of occurrence of side effects can be reduced.
[0016]
(Embodiment 1)
Embodiment 1 of the present invention (Claims 1, 2 and 4) will be described below with reference to the drawings. In FIG. 1, 1 is an input image signal, 2 is first nonlinear conversion means, 3 is second nonlinear conversion means, 4 is selection signal generation means, 5 is selection means, and 6 is a plasma display.
[0017]
In the present embodiment configured as described above, the input / output characteristics of the first and second nonlinear means are, for example, the characteristics as shown in (a) or (b) of FIG. 2 or FIG. Become. This is because the input image signal is nonlinear as shown in (a) or (b) of FIG. 2 when the moving image pseudo contour is likely to occur, that is, when the signal level of the input image signal is a power of 2, for example, in the vicinity of 16. It is intended to switch and select and display after conversion. Note that the characteristic obtained by averaging the nonlinear characteristics (a) and (b) is linear and is considered so as not to affect the average level of the image.
[0018]
This switching corresponds to switching between 5a and 5b by a checkered pattern (5f) alternating in a so-called field that is inverted every horizontal pixel position, every vertical pixel position, or every field. The checkered pattern alternating in this field can be obtained by the exclusive OR 44 of the outputs of the dot counter 41, the line counter 42, and the field counter 43 as shown in FIG.
[0019]
The dot counter 41, the line counter 42, and the field counter 43 are synchronously controlled by a horizontal synchronizing signal and a vertical synchronizing signal.
[0020]
Further, a portion where the input image signal is flat is detected by the flat portion detecting means 45, and in the portion where the input image signal is flat, the original input image signal 5c is always selected and displayed regardless of the checkered pattern 5f described above. By doing so, it is possible to reduce the frequency of occurrence of a side effect that a pattern such as a checkered pattern is observed on the screen without reducing the effect of reducing the moving image pseudo contour.
[0021]
(Embodiment 2)
Embodiment 2 of the present invention (Claim 3) will be described below with reference to the drawings. The present embodiment differs from the first embodiment in the characteristics of the nonlinear deformation means 2 and 3, and FIG. 5 shows the characteristics and FIG. 6 shows a graph of the characteristics. Only differences from the first embodiment will be described below.
[0022]
5 is different from the case of FIG. 2 in that the non-linear characteristic does not exceed a predetermined power of 2, that is, a range of 15 or less to 9 (a range of less than 16 of 2 4 and exceeding 8 of 2 3). ). Therefore, the portion affected by the non-linear characteristic is almost halved, and the frequency of occurrence of a side effect that a pattern such as a checkered pattern is observed on the screen can be further reduced.
[0023]
In addition, when the change of the input image signal level (INlev) is from 16 to 17, when it is changed from 17 to 18, etc.,
Weights of subfields to emit when level INlev is 16 Weights of subfields to emit when 16 level INlev is 17, . . , Weights of subfields emitted when 16 level INlev is 18, 2,. . 16, the change in the light emission pattern is small and the occurrence of the moving image pseudo contour is relatively small. Therefore, even if the non-linear characteristic range is limited to the above-described range, the effect of improving the moving image pseudo contour is excellent. Can be maintained.
[0024]
【The invention's effect】
As described above, according to the present invention, non-linear characteristics can be obtained in a limited range of the signal level of an input image signal using an image display device such as a plasma display using a subfield method and the like in which a moving image pseudo contour is likely to occur. Since it is switched and selected for display, it is possible to suppress the occurrence of side effects and to suppress the occurrence of a moving image pseudo contour.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an image display device according to a first embodiment of the present invention. FIG. 2 is a diagram showing an example of characteristics of nonlinear means in the first embodiment of the present invention. FIG. 4 is a graph showing an example of characteristics of nonlinear means in FIG. 4 is a diagram showing examples of characteristics of nonlinear means in Embodiment 2 of the present invention. FIG. 5 is a diagram of characteristics of nonlinear means in Embodiment 2 of the present invention. Fig. 6 is a graph showing an example. Fig. 6 is a diagram showing the concept of subfield driving in a conventional image display device.
DESCRIPTION OF SYMBOLS 1 Input image signal 2, 3 Nonlinear conversion means 4 Selection signal generation means 5 Selection means 6 Plasma display 41 Dot counter 42 Line counter 43 Field counter 44 Exclusive OR 45 Flat part detection means

Claims (6)

An image display device that performs halftone display by a subfield method,
A plurality of nonlinear conversion means for converting and outputting the signal level of the input signal; and a selection means for selecting one of the output signals of the plurality of nonlinear conversion means and the input signal;
Each of the plurality of nonlinear conversion means has a nonlinear characteristic, and is configured such that a characteristic obtained by averaging the characteristics of each of the plurality of nonlinear conversion means is substantially linear,
When the signal level has a signal level region where the moving image pseudo contour is likely to occur and a signal level region where the moving image pseudo contour is difficult to occur, and the signal level of the input signal is a signal level region where the moving image pseudo contour is likely to occur, The selection means is configured to select one of output signals of the plurality of nonlinear conversion means ,
When the input signal level is flat in the screen, the input signal conversion processing unit is not processed even if the input signal level is a signal level at which a moving image pseudo contour is likely to be generated. Image display device. 2. The image display device according to claim 1, wherein when the input signal level is a signal level region in which a moving image pseudo contour is not easily generated, the selection unit does not select the plurality of nonlinear conversion units. 3. The image display device according to claim 1, wherein the characteristic obtained by averaging the characteristics of each of the plurality of nonlinear conversion means is a characteristic obtained by averaging the characteristics of each of the plurality of nonlinear conversion means in terms of time or space. . The image display device according to claim 1, wherein the input signal level at which the moving image pseudo contour is likely to occur is a signal level at which light emission / non-light emission of all subfields is reversed. The image display device according to any one of claims 1 to 3, wherein the input signal level at which the moving image pseudo contour is likely to occur is a signal level at which a temporal distribution of light emission changes greatly. The image display device according to any one of claims 1 to 3, wherein the input signal level at which the moving image pseudo contour is likely to occur is a signal level in the vicinity of a power value of the input signal level of 2.

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