JP2003288059A - Image display device and image display method - Google Patents

Abstract

(57) [Summary] The present invention relates to a PW (Multiple Gray Scale) display method.
Provided are an image display device and an image display method in which a dynamic range does not decrease and a gradation number of an image signal does not decrease even when the M system is used. SOLUTION: A luminance discrimination for discriminating a peak luminance in a field of an input image signal is performed, and a luminance of the image signal is amplified within a range not exceeding a maximum displayable luminance based on a result determined by the luminance determination means. The amplified image signal is encoded, and the gradation is expressed by modulating the pulse width of a drive pulse for driving a pixel in accordance with the encoded image signal. Thereafter, a process of reducing the luminance of the image signal by the amount amplified is performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image display device, and more particularly to an image display device and an image display method for displaying a gradation image by a pulse width modulation (PWM) method.

[0002]

2. Description of the Related Art FIG. 10 is a schematic diagram showing the structure of a pixel modulating means in a conventional image display device. here,
101 is a comparator, 102 is a pixel for displaying an image,
Reference numeral 103 is a counter, 104 is a memory for storing the image data A, and 105 is a driver. First, the input image signal is encoded into image data A, and the image data A is held in the memory 104. On the other hand, the counter 103
Generates output data B as shown in FIG. 11 according to a clock from the outside, and the output data B is sequentially updated by the clock and makes one cycle in one field cycle. Here, MSB in FIGS. 10 and 11 represents the most significant bit, and LSB represents the least significant bit. Then, the comparator 101 compares the image data A held in the memory 104 and the output data B of the counter 103 with each other. According to this comparison, when the image data A is larger than the output data B,
The comparator 101 outputs the pixel 102 to the driver 105
When the image data A is smaller than the output data B, the comparator 101 controls the driver 105 to output a signal for turning off the pixel 102.

Next, FIG. 12 shows drive pulses output from the comparator 101 to the pixel 102 via the driver 105. Here, t0 represents one field time. When the image data A is 6 bits, the comparator 10
In 1, the image data A is compared with the output data B 2 ⁶ times to determine ON / OFF of the pixel. As a result, the driver 105 outputs the drive pulse as shown in FIG. 8 to the pixel 102. That is, the ON / OFF judgment of the pixel once in the comparator 101 is 1 field time t0.
The drive pulse having a pulse width of 1/64 among the drive pulses having the pulse width of is controlled. Image data A with ε gradation
Considering the case where is input, the comparator 101 determines the pixels to be turned ON up to the εth pixel and sets the pixels to O after the ε + 1th pixel.
Judge as FF. As a result, the driver 105 turns on
It is modulated into a drive pulse having a pulse width of γ times which is ε judgments and is output to the pixel 102. That is, the pixel 102
Lights for γ hours within one field time and expresses image data A of ε gradation. Such a multi-gradation display method is generally applied to PWM (Pulse Wide Modulation).
n) method (pulse width modulation driving method).

Next, FIG. 13 is a schematic diagram showing a structure of a modulation means of an image display device in which pixels are arranged in a matrix. Here, 106 is a row and column address counter, the row address counter outputs a row address to the memory 104 and the scanning circuit, and the column address counter outputs a column address to the memory 104 and a clock signal counter. It outputs to 103 and updates the counter 103. Reference numeral 107 denotes a scanning circuit for selecting one of the row electrodes based on the row address, and 108 denotes a shift register for arranging drive pulses (ON / OFF data) resulting from the comparator 101 in a column order by inputting a shift clock. , 109 are latches for holding the drive pulses (ON / OFF data) arranged by the shift register corresponding to each row electrode of one row.

An operation in which the input image data is modulated and output to the pixel will be described with reference to FIG. Here, the comparator 101, the counter 103, and the memory 104 constitute a modulation means, and the address counter 106 and the driver 10 are provided.
5, scanning circuit 107, shift register 108, latch 1
09 constitutes a drive circuit. First, the encoded image data A is input / held in the memory 104. Next, the image data A held in the memory 104 is output from the comparator 101 based on the row and column addresses from the address counter 106. After that, the comparator 101
Then, the input image data A and the output data B read from the counter 103 are compared to make an ON / OFF determination. By this ON / OFF judgment, the gradation of the image data A is modulated into the drive pulse (ON / OFF data). At that time, the output data B shown in FIG. 11 is generated in the counter 103, and the output data B is the address counter 1
It is updated by the clock from 06 and makes one cycle in one field cycle. The drive pulse (ON / OFF data) obtained as a result of the comparator 101 is arranged in the shift register 108 and held in the latch 109 for each row corresponding to the row electrode. Then, the scanning circuit 107 selects a row electrode based on the row address from the address counter 106,
The driver 10 outputs the drive pulse (ON / OFF data) held in the latch 109 corresponding to the selected row.
5 to the pixel 102.

Next, FIG. 14 is a schematic diagram of a large-sized display constituted by arranging the image display devices shown in FIG. 13 in a matrix. Here, 110 is a display controller, 111 is a first data bus, 112 is a buffer memory, 113 is a second data bus, 114 is a display unit,
Reference numeral 115 is a drive circuit, and 116 is a screen.

Next, the operation will be described. The image signal from the video system is encoded by A / D conversion in the display controller 110 and converted into image data. The image data is transmitted to each buffer memory 112 via the first data bus 111 with the information indicating which unit to display in the pixel conversion process. Here, for information other than the image signal (for example, character information), necessary data is transmitted from the computer system to the communication control in the display controller by communication, is superimposed on the image data through graphic processing or character information processing, and is buffered. It is transmitted to the memory 112. In the buffer memory 112, the transmission speed of the image data transmitted from the first data bus 111 is converted into a low speed, and then the image data is transmitted to each display unit 114 via the second data bus 113. In each display unit 114, image data is accumulated in the memory 104 in each display unit, and the comparator 101 and the counter 103
The PWM method processing described above is performed by the modulation means configured by. After that, a driving pulse is output to the pixel 102 through the driving circuit 116 including an address counter, a driver, a scanning circuit, a shift register, a latch, and the like. As a result, the image data can be displayed on the screen 117 by being configured by the plurality of display units 114.

[0008]

According to the PWM method, which is one of the multi-gradation display methods as shown in the prior art, the input image signal is represented by a predetermined number of bits with reference to the peak brightness of the image display device. It is generally converted into a digitized pulse width. Therefore, even when an image signal of 2 ⁿ gradation is input, the maximum luminance of the image signal is 50% of the peak luminance.
In such a case, when the multi-gradation display is performed by the PWM method, the dynamic range is halved, and the number of gradations displayed on the image display device is substantially halved to 2 ^(n-1) gradation. Since the dynamic range according to this method depends on the maximum luminance of the image signal, it decreases when the maximum luminance is lower than the peak luminance of the image display device, and the number of gradations of the original image signal also decreases. In particular, there is a problem in that the ability to express delicate light and dark in an image in which the entire screen is dark deteriorates, and the image quality deteriorates. Therefore, it is an object of the present invention to provide an image display device and an image display method in which the dynamic range does not decrease and the number of gradations of an image signal does not decrease even if a PWM method, which is one of multi-gradation display methods, is used. And

[0009]

The solution means according to claim 1 of the present invention is based on a brightness determination means for determining the in-screen peak brightness of an input image signal, and a result determined by the brightness determination means. An amplifying unit that amplifies the brightness of the image signal within the screen within a range that does not exceed the maximum displayable brightness, an encoding unit that encodes the image signal amplified by the amplifying unit, and the encoding unit. Modulation means for modulating the pulse width of the drive pulse for driving each pixel of the display screen in accordance with the image signal encoded by the above-mentioned image signal, and the brightness expressed by the drive pulse modulated by the modulating means by the amplifying means. And a brightness reducing unit that reduces the amount of the amplified signal by a factor of 1 on the screen.

According to a second aspect of the present invention, there is provided a brightness determining means for determining an in-screen peak brightness of an input image signal, an encoding means for encoding the input image signal, and the brightness. Amplifying means for amplifying the brightness of the image signal coded by the coding means at a rate within the screen within a range that does not exceed the maximum displayable brightness based on the result judged by the judging means, and amplified by the amplifying means. Modulating means for modulating the pulse width of the drive pulse for driving each pixel of the display screen according to the image signal generated, and the brightness expressed by the drive pulse modulated by the modulating means is amplified by the amplifying means. And a brightness reducing unit that reduces the brightness of the image on the screen.

According to a third aspect of the present invention, there is provided the image display device according to the first or second aspect, wherein the brightness reducing means has a pulse width corresponding to the amount amplified by the amplifying means. Is reduced from the pulse width of the drive pulse.

According to a fourth aspect of the present invention, there is provided the image display device according to the first or second aspect, wherein the luminance reducing means amplifies a ratio to a constant time width by the amplifying means. It is characterized in that a cutting pulse having a pulse width corresponding to the above ratio is inserted at every constant time width of the driving pulse to reduce the luminance.

According to a fifth aspect of the present invention, there is provided the image display device according to the first or second aspect, wherein the brightness reducing means corresponds to the amount amplified by the amplifying means. It is characterized in that the amplitude of the drive pulse is changed to reduce the brightness.

According to a sixth aspect of the present invention, there is provided the image display device according to any one of the first to fourth aspects, wherein the brightness reducing means further includes brightness outside the image display device. The pulse width of the drive pulse is reduced according to the above.

The solution means according to claim 7 of the present invention divides the screen of the image display device into a plurality of blocks, and the brightness discrimination according to any one of claims 1 to 6 for each block. Means, the amplifying means, the encoding means, the modulating means, and the brightness reducing means.

According to an eighth aspect of the present invention, the solving means according to the present invention exceeds the maximum displayable luminance based on the luminance discriminating step for discriminating the in-screen peak luminance of the input image signal and the result discriminated by the luminance discriminating step. An amplification step of amplifying the brightness of the image signal in a screen in a non-existent manner, an encoding step of encoding the image signal amplified by the amplification step, and the encoding step performed by the encoding step. A modulation step of modulating the pulse width of a drive pulse that drives each pixel of the display screen according to an image signal, and a screen that corresponds to the brightness represented by the drive pulse modulated by the modulation step, which is amplified by the amplification step. And a brightness reducing step of reducing the brightness at a single rate.

According to a ninth aspect of the present invention, a solving means according to the present invention comprises a luminance determining step of determining a peak luminance within a screen of an input image signal, an encoding step of encoding the input image signal, and the luminance. An amplification step of amplifying the brightness of the image signal coded by the coding step in the screen within a range not exceeding the maximum displayable brightness based on the result of the judgment step, and an amplification step by the amplification step. The modulation step of modulating the pulse width of the drive pulse for driving each pixel of the display screen according to the image signal generated, and the brightness expressed by the drive pulse modulated by the modulation step is amplified by the amplification step. And a brightness reduction step of reducing the brightness of the image on the screen.

According to a tenth aspect of the present invention, there is provided the image display method according to the eighth or ninth aspect, wherein the brightness reducing step has a pulse width corresponding to the amount amplified by the amplifying step. Is reduced from the pulse width of the drive pulse.

A solution according to claim 11 of the present invention is the image display method according to claim 8 or 9, wherein the brightness reducing step is amplified by the amplifying step in a ratio to a constant time width. It is characterized in that a cutting pulse having a pulse width corresponding to the above ratio is inserted at every constant time width of the driving pulse to reduce the luminance.

According to a twelfth aspect of the present invention, there is provided the image display method according to the eighth or ninth aspect, wherein the luminance reduction step corresponds to the amount amplified by the amplification step. It is characterized in that the amplitude of the drive pulse is changed to reduce the brightness.

[0021]

(First Embodiment) FIG. 1 is a schematic diagram showing the configuration of a display control unit used in the first embodiment.
Here, 1 is a display control unit, 2 is a video system, 3 is a brightness determination unit, 4 is an amplification unit, 5 is a delay unit, 6 is an encoding unit, 7 is a modulation unit, and 8 is a brightness reduction unit. .
It should be noted that in FIG. 14 of the conventional technique, a portion for processing information other than an image signal has been described, but similar processing is possible in each embodiment of the present invention. However, since it is not directly related to the content of the present invention, in the following description, illustration and description of the processing of information other than the image signal will be omitted.

First, the image signal from the video system 2 is input to the display controller 1. For the input image signal, the in-screen peak luminance is discriminated by the luminance discriminating means 3 in the display control section 1. In the description below, the unit of the screen is one field, and the in-screen peak brightness is the in-field peak brightness. Next, the amplifying means 4 amplifies the input image signal based on the peak luminance in the field determined by the luminance determining means 3. For example, when the peak luminance in the field of the input image signal is 1 / n times the maximum luminance that can be displayed on the image display device, the maximum luminance of the peak luminance in the field of the image signal is 1 / n in the luminance discrimination unit 3. It is determined to be n times, and based on this determination, the image signal input by the amplification means 4 is amplified at a rate of n times in the field.
The image signal does not necessarily have to be multiplied by n in the field, and may be n times or less as long as it does not exceed the maximum luminance (the same applies to the following).

FIG. 2 shows an input image signal when the vertical axis represents luminance and the horizontal axis represents time. FIG. 2 also shows the maximum luminance and the peak luminance in the field. FIG. 3 shows an image signal after amplification when the vertical axis represents luminance and the horizontal axis represents time. Here, it is shown that the input image signal is amplified at a rate of n times in the field, and the in-field peak luminance is amplified to almost the maximum luminance. Then, the amplified image signal is input to the delay means 5 and processed. Here, the delay unit 5 is provided in order to secure the time required for determining the in-field peak luminance of the input image signal.

Next, the image signal amplified by the amplifying means 4 is quantized by the encoding means 6 and converted into a digital signal. Hereinafter, the encoded image signal is referred to as image data. After that, the image data is modulated by the modulator 7 into a drive pulse of the PWM method in the multi-gradation display method. Here, the PWM method is the same as the conventional technology,
The comparator compares the input image data with the output data of the counter to determine the pulse width of the drive pulse. That is, it is a method of expressing gradation by modulating gradation to a pulse width. When the image data is 6 bits, the comparator compares the image data with the output data 2 ⁶ times to determine the pulse width of the drive pulse. However, the brightness represented by the drive pulse output from the modulator 7 is different from the brightness of the input image signal because it is modulated based on the image data obtained by amplifying the input image signal. Therefore, it is necessary to reduce the brightness of pulse driving in order to obtain the brightness according to the input image signal.

Therefore, the brightness reducing means 8 reduces the brightness represented by the drive pulse based on the information amplified by the amplifying means 4. For example, when the input image signal is amplified by a factor of n in the field, it is necessary to reduce the brightness represented by the drive pulse by a factor of 1 / n in the field. Here, FIG. 4 shows a timing chart of a specific brightness reducing method. The lower part of FIG. 4 shows a drive pulse for one field, and the upper part shows a cutting pulse. The gradation of the drive pulse is determined by multiplying the quantized time width Tq according to the number of gradations to determine the pulse width, and this pulse width is expressed as gradation. When the image data is 6 bits, there are 64 time widths Tq in one field as shown in FIG. 4, and the lower drive pulse represents 63 gray levels.

In order to reduce the brightness independently of the gradation from the drive pulse expressed in this way, the brightness can be reduced by individually shortening the time widths Tq of 64 existing. For that purpose, a cutting pulse as shown in the upper part of FIG. 4 is superimposed on each position of the time width Tq of the drive pulse. This cutting pulse changes the pulse width ΔT according to the amount amplified by the amplifying means 4. Also,
The amplitude of the cut pulse is the same as the absolute value of the amplitude of the drive pulse, but the sign is opposite. By using such a brightness reducing method, it is possible to easily increase the brightness to 1 / n times in the field by controlling only the pulse width ΔT of the cut pulse. In the brightness reducing means 8, the cutting pulse shown in the upper stage of FIG. 4 is superimposed on the driving pulse shown in the lower stage and input to the drive circuit to control the screen display.

By processing the image signal using such means, the dynamic range does not depend on the maximum brightness of the image signal and is not lowered. In particular, when the brightness of the input image signal is low, the brightness is reduced independently of the gradation by the brightness reducing means while the dynamic range of the image signal is secured by amplifying the image signal, Even with an image signal of a dark image as a whole, it is possible to express a high gradation without lowering the dynamic range.

In the present embodiment, the case in which the display is composed of one screen has been described. However, as shown in FIG. 14 of the prior art, the image display devices are arranged in a matrix. The same can be applied to a large-sized display having a plurality of screens to be displayed. In that case, it is necessary to distribute the means in the display control unit 1 to the display controller and each unit shown in FIG.

(Modification 1 of Embodiment 1) FIG. 5 shows a timing chart of the luminance reducing method of Modification 1. The brightness reducing method performed by the brightness reducing means 7 of the first embodiment is performed by superimposing the cutting pulse having the pulse width ΔT as shown in the upper part of FIG. 4 on each position of the time width Tq of the drive pulse. In the brightness reducing means 7 of the modification 1, the cutting pulse is not superimposed on each position of the time width Tq of the driving pulse, but the cutting pulses having the pulse width ΔT are collectively driven as one cutting pulse for the number of gradations. The brightness is reduced by superimposing it on the entire pulse. In this case, it is necessary to calculate and obtain the pulse width (ΔT × number of gradations) of the cutting pulse in the brightness reducing means 7. It is necessary to control the phase of the cutting pulse so that the cutting pulse overlaps with the driving pulse. Figure 5
(A) shows that the drive pulse in the case of maximum brightness (ΔT × number of gradations) is superimposed so as to coincide with the end of the cut pulse. 5 (b) and (c) are 50% each
The case of luminance and 25% luminance is shown. In FIG. 5, the phase of the cutting pulse is controlled so that the ends of the driving pulse and the cutting pulse coincide with each other, but the starting points of the driving pulse and the cutting pulse may coincide with each other. That is, the phase may be controlled so that the cutting pulse is superposed during the period from the rise of the drive pulse to the fall thereof.

The amplitude of the cut pulse is the same as the absolute value of the amplitude of the drive pulse, but the sign is opposite. Even by this method, the dynamic range does not depend on the maximum brightness of the image signal and does not decrease. In particular, when the brightness of the input image signal is low, the brightness is independently reduced from the gradation by the brightness reducing means while the image signal is amplified to secure the dynamic range of the image signal. Even with an image signal of an image in which the entire screen is dark, it is possible to express a high gradation without lowering the dynamic range.

(Modification 2 of Embodiment 1) FIG. 6 shows a timing chart of the luminance reducing method of Modification 2. The brightness reduction methods of the first embodiment and the first modification are both methods of superimposing a cutting pulse on a drive pulse. The brightness reducing means 7 of the second modification does not superimpose the cutting pulse on the drive pulse but changes the amplitude Vq of the drive pulse to reduce the brightness. That is, the brightness of the screen display is controlled by the amplitude of the drive pulse. However, in this case, the display element (for example, LED, CRT, etc.) is limited to the one having the characteristic that the brightness changes according to the amplitude of the drive pulse which is the input signal.

Even with this method, the dynamic range does not depend on the maximum luminance of the image signal and does not decrease. In particular, when the brightness of the input image signal is low, the brightness is independently reduced from the gradation by the brightness reducing means while the image signal is amplified to secure the dynamic range of the image signal. Even with an image signal of an image in which the entire screen is dark, it is possible to express a high gradation without lowering the dynamic range.

As the brightness reducing method in the brightness reducing means 7, in addition to the above method, a method of thinning out frames or a method of reducing the display area can be considered.

(Second Embodiment) FIG. 7 is a schematic diagram showing the configuration of a display control unit used in the second embodiment. Here, 9 indicates an external illuminance determining means. Since the image display device affects the perception of the audience and the viewer depending on the illuminance of the environment,
It is necessary to adjust the screen brightness according to changes in the illuminance of the environment. Generally, the brightness of the screen needs to be bright when the illuminance of the environment is bright and dark when the illuminance of the environment is dark. FIG. 7 shows a configuration in which an external illuminance discriminating means 9 is added to the configuration of the display control unit of the first embodiment shown in FIG. First,
The image signal input from the video system 1 is discriminated by the luminance discriminating unit 3 for the peak luminance in the field, is amplified by the amplifying unit 4 at a rate of n times in the field, and is encoded into a driving pulse by the modulating unit 6. Is modulated. Finally, the brightness reducing means 7 superimposes the cut pulse to reduce the brightness represented by the drive pulse to 1 / n times in the field. Separately from this, the external illuminance discriminating means 9 measures the illuminance of the external environment of the image display device, and the coefficient (for example, 1 / m) for adjusting the luminance required for the image display device according to the measured illuminance is used as the luminance. It is transmitted to the reduction means 7. As a result, the brightness reducing means 7 has a pulse width Δ of the cutting pulse according to the coefficient (for example, 1 / m) for adjustment.
It becomes possible to easily control the brightness by changing T and superimposing the cutting pulse on the drive pulse. In other words, the brightness reducing means 7 may superimpose the cutting pulse having the pulse width ΔT necessary for reducing the brightness by (1 / n) × (1 / m) times on the drive pulse.

As described above, when the cut pulse is used also when the brightness of the image display device is adjusted according to the external environment,
In particular, it is not necessary to provide another brightness adjusting mechanism for adjusting the brightness of the image display device according to the external environment, and the cost can be reduced. Further, as in the first embodiment, the dynamic range does not depend on the maximum brightness of the image signal and does not decrease. Especially when the brightness of the input image signal is low,
It is possible to simultaneously realize the function of amplifying the image signal and capable of expressing high gradation without lowering the dynamic range of the image signal. Therefore, a high-quality image can be displayed regardless of the installation location of the image display device.

(Third Embodiment) FIG. 8 is a schematic diagram showing the configurations of a display control unit and an image display portion used in the third embodiment. Here, 10 is an image display portion, 11 is a display block, 12 is a pixel, and 13 is a drive circuit. The display control unit 1 of FIG. 6 is the display control unit 1 of the first embodiment shown in FIG.
It has the same structure as. However, the processing unit of the display control unit 1 of the third embodiment is different from that of the first embodiment, and this point will be described below. The display control unit 1 according to the first embodiment discriminates the peak luminance of a predetermined field, amplifies the entire screen of one frame on the basis of the peak luminance, and thereafter,
Encoding, modulation, and brightness reduction processing are performed in units of the entire frame screen. However, depending on the displayed image, a part of the screen may have a high brightness part and the other part may have a low brightness part. In this case, the display control unit 1 of the first embodiment
If the whole screen of one frame is processed as a unit like the processing of, the processing may be amplified with the high brightness part as a reference.
There is a problem that the dynamic range of most of the low luminance is lowered, the ability of expressing delicate light and shade is lowered, and the image quality is deteriorated.

Therefore, in the processing of the display control unit 1 of the third embodiment, the screen display portion 10 is divided into a plurality of display blocks 11 as shown in FIG. 6, and the processing of the display control unit 1 is performed in units of the display blocks 11. To do. The display block 11 includes a plurality of pixels 12. That is, the display control unit 1 according to the third embodiment determines the peak luminance of a predetermined field in the display block 11, and based on that, the display block 1 is determined.
The brightness of the screen of 1 frame of 1 is amplified, and thereafter, the processing of coding, modulation, and brightness reduction is performed for each display block 11. As a result, even if there is a high-luminance portion in a part of the entire screen and the rest is low, the high-luminance portion is processed by the display control unit 1 in the screen display portion 10 including it. It does not have any influence on the processing of the display control unit 1 in the screen display portion 10 including other low luminance portions. Therefore, while ensuring the dynamic range of the image signal on the entire screen, it is possible to express a high gradation without lowering the dynamic range even in a low luminance part.

(Embodiment 4) In the processing in the above display control section, the image signal was amplified and then coded to form image data. However, after the image signal is coded into image data, digital arithmetic processing is performed. Then, it may be amplified. Due to the following reasons, it is possible to achieve a high gradation expression while maintaining a sufficient dynamic range even if amplification is performed after encoding, and without lowering the dynamic range even in a low luminance part. In addition, it is advantageous in that the circuit configuration is simple and the cost is reduced when the image signal is encoded to become image data and then digitally processed and amplified.

The television signal, which is an image signal, is adjusted for a CRT in which the relationship between the input signal and the output luminance is nonlinear (γ
Has been corrected). On the other hand, in the PWM method, which is a multi-gradation display method used in the present invention, the input signal and the output luminance are proportional. Therefore, it is necessary to perform inverse γ correction in order to represent the television signal, which is an image signal, by the PWM method. Here, the inverse γ correction is a relation in which the normalized input x and the output f (x) are represented by f (x) = x ^γ , and γ≈2.3. FIG. 9 is a diagram for explaining inverse γ correction in a signal quantized into 6 bits (64 gradations). In order to correspond to the inverse γ correction, the output signal for the input signal x is f (x) = x
^The output needs to follow the curve of ^γ . But PW
With the output gray scale of the M method, gray scales below the level corresponding to the quantized time width Tq cannot be reproduced. Therefore, in the portion expressing the low luminance, even if the gradation of the input signal changes, the output signal, which is the output gradation, can change only in Tq units, so that the gradation expression of the input signal cannot be reproduced at the output. . An enlarged view of the 0 to 20 gradation portion of FIG. 9 is shown in the B portion of FIG. Here, 0 to 7 gradations of the input signal are expressed as 0 gradations of the output signal. Therefore, when a television signal, which is an image signal, is represented by the PWM method, the gradation representation of the television signal, which is the input signal, cannot be represented by the output of the PWM method when the luminance of the image is low and the dynamic range is low. is there. Therefore, the television signal, which is an input signal, is encoded, and then arithmetically processed to be amplified, whereby the dynamic range is apparently expanded, and the display of subtle light and dark in the low luminance region at the time of inverse γ correction is improved.

[0040]

The image display device according to the first aspect of the present invention has a luminance discriminating means for discriminating the in-screen peak luminance, an amplifying means for amplifying the luminance, an encoding means for encoding, and a pulse of a driving pulse. By providing the modulation means for modulating the width and the luminance reduction means for reducing the amplified amount, the dynamic range has an effect of not depending on the maximum luminance of the image signal and not lowering. In particular, when the brightness of the input image signal is low, the brightness is reduced independently of the gradation by the brightness reducing means while the dynamic range of the image signal is secured by amplifying the image signal, Even with an image signal of a dark image as a whole, it is possible to express a high gradation without lowering the dynamic range.

An image display device according to a second aspect of the present invention is a luminance discriminating means for discriminating the peak luminance in the screen, an encoding means for encoding, an amplifying means for amplifying the luminance after encoding, and a drive pulse. By providing a modulation unit that modulates the pulse width of and a brightness reduction unit that reduces the amplified amount, the dynamic range is ensured, and even if the brightness is low, the dynamic range is not lowered and high gradation is obtained. Expression becomes possible. In addition, it is advantageous in that the circuit configuration is simple and the cost is reduced when the image signal is encoded to become image data and then digitally processed and amplified.

In the image display apparatus according to the third aspect of the present invention, the brightness reducing means reduces the pulse width corresponding to the amount amplified by the amplifying means from the pulse width of the driving pulse, so that the dynamic range becomes There is an effect that it does not depend on the maximum brightness of the signal and does not decrease.

In the image display device according to a fourth aspect of the present invention, the brightness reducing means inserts a cutting pulse having a pulse width corresponding to the amount amplified by the amplifying means for each constant time width of the drive pulse to obtain the brightness. By reducing, the dynamic range does not depend on the maximum luminance of the image signal and is not reduced.

In the image display device according to a fifth aspect of the present invention, the brightness reducing means changes the amplitude of the drive pulse in accordance with the amount amplified by the amplifying means to reduce the brightness, and thus the dynamic range is There is an effect that it does not depend on the maximum luminance of the image signal and does not decrease.

In the image display device according to claim 6 of the present invention, the brightness reducing means reduces the pulse width of the drive pulse according to the brightness of the outside of the image display device, so that the image can be displayed according to the external environment. When the cut pulse is used also when adjusting the brightness of the display device, it is not necessary to provide a separate brightness adjusting mechanism for adjusting the brightness of the image display device in accordance with the external environment, and the cost can be reduced.

An image display device according to a seventh aspect of the present invention divides a screen display portion of the image display device into a plurality of blocks, and each block is defined by any one of the first to third aspects. By providing the brightness determining means, the amplifying means, the encoding means, the modulating means, and the brightness reducing means, the dynamic range of the image signal is secured for the entire screen, and the dynamic range is not lowered even in the low brightness part. High gradation expression is possible.

In the image display method according to the eighth aspect of the present invention, the peak luminance in the screen is discriminated, the luminance is amplified and coded, the pulse width of the driving pulse is modulated, and only the amount amplified by the luminance amplification is amplified. The reduction has an effect that the dynamic range does not decrease and does not depend on the maximum brightness of the image signal.

In the image display method according to the ninth aspect of the present invention, the peak luminance in the screen is discriminated and encoded, and then the luminance is amplified, the pulse width of the drive pulse is modulated, and the amplified luminance is amplified. By reducing only that, the dynamic range has an effect of not lowering without depending on the maximum luminance of the image signal. In addition, it is advantageous in that the circuit configuration is simple and the cost is reduced when the image signal is encoded to become image data and then digitally processed and amplified.

According to the image display method of the tenth aspect of the present invention, by reducing the pulse width corresponding to the amplified amount of the luminance of the image signal from the pulse width of the driving pulse, the dynamic range is the maximum of the image signal. It has the effect of not lowering the brightness without depending on it.

In the image display method according to the eleventh aspect of the present invention, a cutting pulse having a pulse width corresponding to the amplified amount of the luminance of the image signal is inserted for each gray level to reduce the luminance, thereby reducing the dynamic range. Has the effect of not lowering the maximum brightness of the image signal without depending on it.

In the image display method according to the twelfth aspect of the present invention, in the brightness reducing step, the amplitude is reduced by changing the amplitude of the drive pulse corresponding to the amount amplified by the amplifying step, whereby the dynamic range is There is an effect that it does not depend on the maximum luminance of the image signal and does not decrease.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration of a display control unit of an image display device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing an image signal input to the image display device according to the first embodiment of the present invention.

FIG. 3 is a diagram showing an image signal amplified by an amplification means of the image display device according to the first embodiment of the present invention.

FIG. 4 is a diagram showing a timing chart of a luminance reduction method for the image display device according to the first embodiment of the present invention.

FIG. 5 is a diagram showing a timing chart of a brightness reducing method for the image display device of the first modification of the first embodiment of the present invention.

FIG. 6 is a diagram showing a timing chart of a brightness reducing method for the image display device of the second modification of the first embodiment of the present invention.

FIG. 7 is a schematic diagram showing a configuration of a display control unit of the image display device according to the second embodiment of the present invention.

FIG. 8 is a schematic diagram showing a configuration of a display control unit of an image display device according to a third embodiment of the present invention.

FIG. 9 is an inverse γ of the image display device according to the fourth embodiment of the present invention.
It is a figure explaining amendment.

FIG. 10 is a schematic diagram showing a configuration of a pixel modulating unit of a conventional image display device.

FIG. 11 is a diagram showing output data B of a counter of a conventional image display device.

FIG. 12 is a diagram showing drive pulses of a conventional image display device.

FIG. 13 is a schematic diagram showing a configuration of a modulation unit of an image display device in which conventional pixels are arranged in a matrix.

FIG. 14 is a schematic view of a large-sized display including conventional image display devices arranged in a matrix.

[Explanation of Codes] 1 Display Control Unit, 2 Video System, 3 Luminance Discriminating Means, 4 Amplifying Means, 5 Encoding Means, 6 Modulating Means, 7
Brightness reduction means, 8 delay means, 9 external illuminance determination means,
10 image display part, 11 display block, 12 pixels, 13 drive circuit, 101 comparator, 102
Pixel, 103 counter, 104 memory, 105 driver, 106 address counter, 107 scanning circuit, 108 shift register, 109 latch, 110
Display controller, 111 first data bus, 112
Buffer memory, 113 second data bus, 114 display unit, 115 drive circuit, 116 screen.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G09G 3/20 642 G09G 3/20 642D 642E 642F H04N 5/66 H04N 5/66 A F term (reference) 5C006 AA15 AA16 AA17 AA22 AF04 AF26 AF51 AF52 AF53 AF54 AF81 BC16 BF07 BF14 BF25 BF39 FA54 FA56 5C058 AA01 AA13 BA01 BA07 BB03 BB25 5C080 CC06 DD04 EE29 FF12 FF13 GG10 GG11 JJ02 JJ05

Claims (12)

[Claims] 1. A brightness discriminating means for discriminating an in-screen peak luminance of an input image signal, and a screen for displaying the luminance of the image signal within a range not exceeding the maximum displayable luminance on the basis of a result discriminated by the luminance discriminating means. An amplifying means for amplifying the image signal amplified by the amplifying means, an encoding means for encoding the image signal amplified by the amplifying means, and each pixel of a display screen according to the image signal encoded by the encoding means Modulating means for modulating the pulse width of the driving pulse for driving the driving pulse, and luminance reducing means for reducing the luminance expressed by the driving pulse modulated by the modulating means by a factor corresponding to that amplified by the amplifying means. An image display device comprising: 2. A luminance discriminating means for discriminating an in-screen peak luminance of an inputted image signal, an encoding means for encoding the inputted image signal, and a display based on a result discriminated by the luminance discriminating means. Amplifying means for amplifying the luminance of the image signal encoded by the encoding means to a ratio within the screen within a range not exceeding the maximum possible luminance, and a display screen according to the image signal amplified by the amplifying means. A modulation means for modulating the pulse width of a drive pulse for driving each pixel, and the brightness expressed by the drive pulse modulated by the modulation means is reduced to a ratio within the screen by the amount amplified by the amplification means. An image display device including a brightness reducing unit. 3. The image display device according to claim 1, wherein the brightness reduction unit reduces the pulse width corresponding to the amount amplified by the amplification unit from the pulse width of the drive pulse. An image display device characterized by: 4. The image display device according to claim 1, wherein the brightness reducing unit has a pulse width having a pulse width corresponding to a ratio of a constant time width amplified by the amplifying unit. An image display device, wherein a pulse is inserted at each of the constant time widths of the drive pulse to reduce brightness. 5. The image display device according to claim 1, wherein the brightness reducing unit changes the amplitude of the drive pulse corresponding to the amount amplified by the amplifying unit to reduce the brightness. An image display device characterized by: 6. The image display device according to claim 1, wherein the brightness reducing unit further sets a pulse width of the drive pulse according to brightness outside the image display device. An image display device characterized by reduction. 7. The screen of the image display device is divided into a plurality of blocks, and each of the blocks is divided into blocks.
The brightness determining means, the amplifying means,
An image display device provided with the encoding means, the modulating means, and the brightness reducing means. 8. A luminance discriminating step of discriminating a peak luminance within a screen of an input image signal, and a luminance of the image signal within a range not exceeding a displayable maximum luminance on the basis of a result discriminated by the luminance discriminating step. An amplifying step for amplifying the image signals amplified by the amplifying step, an encoding step for encoding the image signal amplified by the amplifying step, and each pixel of a display screen according to the image signal encoded by the encoding step A step of modulating a pulse width of a driving pulse for driving the driving pulse, and a luminance reducing step of reducing the luminance represented by the driving pulse modulated by the modulating step by the amount amplified by the amplifying step. An image display method comprising: 9. A luminance discriminating step of discriminating an in-screen peak luminance of an input image signal, an encoding step of encoding the input image signal, and a display based on a result discriminated by the luminance discriminating step. An amplification step of amplifying the luminance of the image signal encoded by the encoding step in the screen within a range not exceeding the maximum possible luminance, and a display screen according to the image signal amplified by the amplification step. A modulation step of modulating the pulse width of a drive pulse for driving each pixel, and the luminance expressed by the drive pulse modulated by the modulation step is reduced to a ratio within the screen by the amount amplified by the amplification step. An image display method including a brightness reduction step. 10. The image display method according to claim 8, wherein the brightness reduction step reduces a pulse width corresponding to the amount amplified by the amplification step from the pulse width of the drive pulse. An image display method characterized by: 11. The image display method according to claim 8 or 9, wherein the luminance reduction step has a pulse width having a pulse width corresponding to a ratio of a constant time width amplified by the amplification step. An image display method characterized in that a pulse is inserted at every constant time width of the drive pulse to reduce the brightness. 12. The image display method according to claim 8 or 9, wherein the brightness reduction step changes the amplitude of the drive pulse in accordance with the amount amplified by the amplification step to reduce the brightness. An image display method characterized by: