JPH02266773A - Video signal processor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a video signal processing device in a display device using a display device such as a liquid crystal television in which it is difficult to ensure sufficient contrast.

[Conventional technology]

An example of a display device that cannot ensure sufficient contrast is TPT (Thin Film Transist).
or) Taking up an active matrix liquid crystal television, the conventional configuration will be explained.

FIG. 5 is a block diagram of a TPT active matrix liquid crystal television. In FIG. 5, 1 is a video signal input terminal to which a video signal is input.

The video signal input to this video signal input terminal 1 is transmitted to the clamp circuit 51, the gradation correction circuit 6. The signal is supplied to the TPT active matrix liquid crystal panel module 4 through the alternating current/drive circuit 7 in sequence.

Here, the clamp circuit 51 gradation correction circuit 6. The alternating current/drive circuit 7 serves as a video signal processing section for a display using a TPT active matrix liquid crystal panel module 4.

It should be noted that, among the components of the liquid crystal television, the chino-subsection, demodulation section, etc. are omitted because they are not directly related to this invention, which will be described later.

Also, in order to avoid the complexity of the explanation, here we will use black and white 1/1
After explaining the process, the operation will be explained next. The analog video signal supplied to the video signal input terminal 1 is clamped by the clamp circuit 5 so that the black level becomes a predetermined potential.

Next, this analog video signal is input to a gradation correction circuit 6 having characteristics as shown in FIG. 6, for example, where the black level is So and the white level is S. The gradation is corrected to a signal within the range of .

Second, the correction characteristics shown in FIG. 6 take into consideration the drive voltage/transmittance (brightness) characteristics of the TPT active matrix liquid crystal panel module 4, which will be described later. Since it is assumed that the characteristics are highly saturated, in order to correct this, the characteristics of the gradation correction circuit 6 are such that the black side is compressed and the white side is expanded.

Next, the output after this gradation correction is as shown in Figure 7, for example.
It is input to the alternating current drive circuit 7 which has such characteristics, and during positive polarity drive, the black level is C+Ve and the own level is C+.
V1. j, when driving with negative polarity, black hell is C-11,,
White 1/Hel is converted into a signal C-v□.

Here, in order to extend the life of the liquid crystal, the positive polarity drive and the nine polarity drive are switched, for example, at one frame cycle, and the video signal is converted to AC.

The output signal of this alternating current/drive circuit 7 is applied to the TPT active matrix liquid crystal panel module 4 having characteristics as shown in FIG.

As shown in FIG. 8, the transmittance of the pixel at 1/s to be displayed on the liquid crystal panel changes from black when the drive voltage is Ci:Vl to C±v1. When it is 1, it indicates white, so the input image No. 18 is displayed on the TPT active matrix liquid crystal panel module 40.

Note that, as shown in FIG. 8, the transmittance has a characteristic that is symmetrical with respect to the drive voltage C, so that the above-mentioned inconvenience caused by alternating current does not occur.

[Problem to be solved by the invention]

Since the conventional TPT active matrix liquid crystal TV I/V is configured as described above, the characteristics of the liquid crystal panel (display device) directly affect the image quality.

That is, the narrow optical dynamic range of the liquid crystal panel directly affects image quality, resulting in problems such as lack of contrast and last.

This invention was made to solve the above-mentioned problems, and its purpose is to provide a video signal processing device that can improve the apparent contrast even in display devices that cannot widen the optical dynamic range. do.

[Failure to solve the problem]

The video signal processing device according to the present invention has an adaptive brightness gradation correction function that converts a signal to be brighter or darker than the brightness of an image with medium brightness, depending on the brightness of the image. It is equipped with an adaptive brightness gradation correction circuit and an AC overdrive circuit that inputs the output of the adaptive brightness gradation correction circuit and drives the display means with an overdrive voltage slightly higher than a predetermined level. [Function] The adaptive brightness gradation correction circuit of the present invention converts the input video signal into a signal that becomes brighter as the image becomes darker than when the image is of medium brightness, and As the image becomes brighter, the signal is converted to become darker compared to the brightness of the medium brightness, and the alternating overdrive circuit adjusts the brightness of the raw image according to the output of this adaptive brightness gradation correction circuit. For a signal that ranges from the black peak to the self-peak, the gain of the entire f3 processing system is slightly increased so that it is slightly larger than the dynamic range on the signal for displaying the optical black peak to the self-peak. , overdrive the display means.

〔Example〕

Embodiments of the video signal processing device of the present invention will be described below. Here, as an example of a display device that cannot ensure sufficient contrast, a TPT active matrix liquid crystal television will be taken up as in the conventional example, and a case where the present invention is applied. An example of this will be described with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of a TPT active matrix liquid crystal television to which the present invention is applied. This first
In the figure, the same parts as in FIG. 5 are given the same reference numerals and explained.

1 in the figure is a video signal input terminal to which a video signal is input. The video signal input to this video signal input terminal 1 is
Adaptive brightness/gradation correction circuit 2. The signal passes sequentially through an AC/overdrive circuit 3 and is supplied to a TPT active matrix liquid crystal panel module 4 as a display means.

Here, the video signal input terminal 1 and the TPT active matrix liquid crystal panel module 4 are the same as those in the conventional example.

It should be noted that among the constituent parts of the liquid crystal television, the chainer part, demodulation part, etc. are not directly related to this invention, so they are omitted as in the conventional example.

Further, here, in order to avoid complication of explanation, the explanation will be given as a black and white television.

Next, the operation will be explained. The analog video signal supplied to the video signal input terminal l is first supplied to the adaptive brightness/gradation correction circuit 2. This adaptive brightness/gradation correction circuit 2 has characteristics as shown in FIG.

That is, when the average brightness of the image is medium (medium APL), the correction characteristics are the voltage/transmittance characteristics of the TPT active matrix liquid crystal panel module 4 (assuming the same characteristics as the conventional example in FIG. 8), as in the conventional example. ), black side compression and white side expansion are performed so that the black peak has a signal level of Sl and the white peak has a signal level of S-.

Also, if the average brightness of the image is low level (low APL),
In other words, in the case of a black-side concentrated signal, the black peak is at the signal level of Sl, which is slightly higher than the level of S, as shown in the figure.
Depending on the degree to which the signal is concentrated toward the black side, the characteristics change as indicated by the arrows in the figure.

Conversely, when the average brightness of the image is at a high level (high APL),
That is, in the case of a signal concentrated on the white side, as shown in the figure, the white peak becomes the signal level of S-, which is slightly lower than the level of S, 1, and depending on the degree of concentration of the signal on the white side, the white peak becomes the signal level of the arrow A! The characteristics change as follows.

In this way, the adaptive brightness/gradation correction circuit 2 is configured to adaptively change its conversion characteristics depending on the image content.

Next, the output signal of this adaptive brightness/gradation correction circuit 2 is
It is supplied to the alternating current/overdrive circuit 3. This alternating current/overdrive circuit 3 has characteristics as shown in FIG.

Regarding the characteristics shown in FIG. 3, the alternating current function of switching between positive polarity drive and negative polarity drive at one frame cycle is the same as in the conventional example.

The difference from the conventional example is that the S□ level of the output signal of the adaptive brightness/gradation correction circuit 2 is the same as the drive voltage C±V that displays the optical black peak in the TPT active matrix liquid crystal panel module 4. The S level of the output signal is amplified to the drive voltage C±Vw representing the optical white peak in the same module 4, respectively.

As a result, at the output signal level of the adaptive brightness/gradation correction circuit 2, the signal between 51 and S0 is further black than the voltage that optically displays the black peak (the black peak on the drive voltage is C:! = v, .), the signal between 5lll"5ll111 is converted to a drive voltage that is further white than the voltage that optically displays the white peak (the white peak on the drive voltage is C±v8°), and is overdriven. will be done.

Therefore, compared to the conventional signal, a wider range is allocated to the signal between S1 and S by the amount of overdrive on the optical dynamic range, and the average contrast for a wide variety of images is increased.

Also, the blackout and S between S and S11 due to this overdrive. -5W white collapse is reduced by the adaptive brightness/gradation correction circuit 2 and the probabilistic characteristics and visibility characteristics regarding the brightness distribution of the image.

These situations are explained in FIG.
This is an explanation of how the optical dynamic range imprinting differs between the conventional example and the one according to the present invention with respect to C1.

The image patterns for each brightness distribution are explained below. In the figure, the shaded area is the area optically modulated by the signal. (1) Image pattern a is an image pattern with high APL concentrated on the white side. In this case, the adaptive brightness/gradation correction function works to make it slightly darker, and the overdrive function slightly increases the gain, so as shown in the figure,
A wider optical dynamic range is allocated which causes whitewashing and increases contrast.

(2) Image pattern b is a low APL image pattern with concentrated quality. In this case, the adaptive brightness/gradation correction function works to make the correction slightly brighter, and the overdrive function slightly increases the gain, so as shown in the figure, the optical dynamic 1/ color is assigned and the contrast is increased.

(3) Image pattern C has an average brightness of medium level (medium A
This is the case of an image pattern in which the luminance distribution is relatively concentrated in this f-averaged level.

In this case, the adaptive brightness and gradation correction section only performs normal gradation correction, and brightness correction etc. do not work, and the over) function increases the gain slightly by 1 to 2. As shown in the figure, a wider optical dynamic range is achieved without white/black blurring, and contrast is increased.

(4) Image pattern d has an average brightness of medium level (medium A,
P L ) and the brightness distribution is distributed from the self peak to the black peak and is an image pattern. in this case,
Adaptive brightness/gradation j [The correction section only performs normal gradation correction; the brightness correction does not work, and the overdrive function slightly increases the gain, so the white/black/white/black color changes slightly as shown in the figure.
Causes swelling.

However, since the image area where black and white collapse occurs is only a small portion of the entire image area, no significant visual quality deterioration occurs.

In addition, compared to the conventional example, the brightness of the black peak and the self-peak itself does not change, but due to the overdrive, the brightness distribution is 111
(bias toward the inside and quality) becomes large, and contrast (5) image pattern C has an average brightness of medium level (medium AP).
This is the case of an image pattern in which the brightness distribution is concentrated toward both the white side and the black side. In this case, the adaptive brightness distribution/tone correction section only performs normal tone correction.
Since brightness correction etc. do not work and the gain is slightly increased by the overdrive function, white/black collapse occurs as shown in the figure.

This pattern is the one that this invention is weakest at, but images that are concentrated on the white side and the quality extremes and have subtle gradations, especially in general TV images, have low probability. Theoretically, the frequency of occurrence is very low, and even if it does occur, the gradation collapse is visible on the manga-like surface, and I don't feel much deterioration.

Note that due to the function of the adaptive brightness/gradation correction function for each image pattern, the optical dynamic range 11 is applied differently in terms of brightness (even if there is a large difference in brightness in the original image, The image viewer is not simply paying attention to the quality of the image, but is failing to recognize the flow of the image content. Even if the brightness difference becomes slightly smaller, this difference can be easily recognized, and this will hardly cause any discomfort.

In the above embodiment, a TPT active matrix (night television) was taken up as an example of a display device using a display device in which it is difficult to ensure sufficient contrast, and an example of its application thereto was explained. This invention can be applied to display devices in general that use display devices that cannot ensure sufficient contrast.

For example, if a simple matrix liquid crystal television or the like is provided with the above-mentioned function in the image processing section (No. 8), the same effect as in the above embodiment can be achieved.

In addition, although the above practical example C was explained for the case of a white/black television (display), in the case of a color television (display), the overdrive function is implemented by each of the R, G, and B video signal processing systems or by the Y (Brightness) By providing the signal processing system with the adaptive brightness/gradation correction function and providing the Y48 processing system with the adaptive brightness/gradation correction function, the same effects as in the above embodiment can be achieved.

Here, if both the overdrive function and the adaptive brightness/gradation correction function are provided in each R, G, and B signal processing system, the adaptive brightness/gradation correction function will work for image patterns close to the primary colors. , Primary colors with high brightness are driven slightly dark<, Primary colors with low brightness are driven slightly brighter, resulting in low coloring (color gain).

However, even with such a configuration, in a display device with an optically narrow dynamic range, the effect of increasing contrast has a greater influence on the overall image quality evaluation than the decrease in color gain, and has a considerable effect.

〔Effect of the invention〕

As described above, according to the present invention, the adaptive gradation correction circuit performs No. 11 conversion on the video signal so that the darker the image becomes, the brighter it becomes compared to the brightness of the medium-brightness image, and the video signal is converted into a brighter image. As the image becomes darker, the signal is converted to become darker compared to the brightness of the medium-brightness image, so for most images, there is no white/black collapse, an effect of increasing contrast is obtained, and only a small amount of brightness is achieved. For some images, some white/black collapse occurs, but there is no significant visual deterioration. Therefore, it is possible to obtain the effect of increasing the average contrast in terms of probabilistic and visual characteristics for a wide variety of images. It has the effect of

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a video signal processing device according to an embodiment of the present invention, FIG. 2 is a characteristic diagram showing the characteristics of the adaptive brightness/gradation correction circuit in FIG. 1, and FIG. 1
Figure 4 is a characteristic diagram showing the characteristics of the AC/overdrive circuit in Figure 4. Figure 4 is an explanatory diagram comparing how various video signal patterns are assigned to the optical dynamic range of a display device with the conventional example and the present invention. , 5th
The figure is a block diagram showing the configuration of the video signal processing section of a conventional active matrix liquid crystal television, FIG. 6 is a characteristic diagram showing the characteristics of the gradation correction circuit in FIG. 5, and FIG. Characteristic diagram showing the characteristics of the drive circuit, No. 8
The figure is a diagram showing voltage/transmittance (brightness) characteristics of the TPT active matrix liquid crystal panel module of FIGS. 1 and 5. l...Video signal input terminal, 2...Adaptive brightness/gradation correction circuit, 3...AC conversion/overdrive circuit, 4...
・・TPT active matrix liquid crystal panel module. In addition, in the figures, the same reference numerals indicate the same or equivalent parts. Agent Masuo Oiwa 2nd figure 3rd figure 6 figure, title of the invention, person making the amendment 7 figure procedure amendment (voluntary) Video signal processing device representative person I ~ Kimoriya 5, of the amendment Each column 6 of the scope of claims and detailed description of the invention in the subject specification, Contents of amendment (1) The scope of claims of the specification is corrected as shown in the attached sheet. (2) On page 6, line 9 of the same page, correct l for image brightness to read ``signal conversion for the image.'' (3) Correct "when brightness" in line 6, true 11, to "signal conversion for images." (4) On page 6, line 13, "according to" is corrected to "in response." (5) Correct "image brightness" in lines 2 and 4 on page 16 to read "signal conversion for images". 7. Amendment of list of attached documents Claims 1 copy 2o Claims According to the input video signal, depending on the brightness of the image, when the brightness of the image is medium brightness, the brightness of the image is changed to low brightness according to the display means. As the brightness of the image increases, the signal is converted to become brighter, and the brightness of the image becomes brighter. Adaptive brightness/gradation correction circuit with an adaptive brightness/gradation correction function that converts the signal to be darker compared to the image with the brightness of the medium brightness of the image - 4] δ-5 Then, with the output of this adaptive brightness/gradation correction circuit, when driving the display means, the optical B, 4 - An image equipped with a patrol circuit that slightly increases the gain of the entire signal processing system and overdrives it so that the dynamic range on the signal is slightly larger than the dynamic range on the signal for displaying the own peak from the black peak. Signal processing device.

Claims (1)

[Claims] Depending on the brightness of the image depending on the input video signal, when the brightness of the image is medium brightness, as the brightness of the image becomes low brightness according to the display means, it is compared with the brightness of the above medium brightness image. Adaptive brightness, which converts the signal to become brighter, and converts the signal to become darker as the brightness of the high-brightness image increases compared to the brightness of the medium-brightness image.
An adaptive luminance/gradation correction circuit having a gradation correction function, and when driving the display means with the output of this adaptive luminance/gradation correction circuit, when the brightness of the above-mentioned medium-luminance image is high, the black peak For signals that have up to a white peak, the AC converter is used to overdrive by slightly increasing the gain of the entire signal processing system so that the dynamic range on the signal is slightly larger than the optical dynamic range for displaying the optical black peak to white peak. A video signal processing device equipped with an overdrive circuit.