JPH05281926A - Liquid crystal video display device - Google Patents

Abstract

PURPOSE:To reproduce even the details of the bright part of an image and the details of the dark part by controlling an input video signal with a video control signal calculated by an arithmetic means. CONSTITUTION:A brightness signal Y separated by a Y/C separating circuit 2 is passed through a screen area division part 4 and supplied to a peak detecting circuit 5 which detects the white peak value of the brightness signal, a mean value detecting circuit 6 which detects the mean level of the brightness signal, a black level detecting circuit 7 which detects the black level of the brightness signal, and a pedestal detecting circuit 8 which detects the pedestal level of the brightness signal. An arithmetic circuit 23 performs weighted mean arithmetic by using control signals for degrees mu1, mu2, and mu3, and E1, E2, and E3 outputted by comparing circuits 18 and 19 and look-up tables 17, 20, 21, and 22 as input signals and outputs a brightness control signal EBR. The brightness control signal EBR is supplied from the arithmetic circuit 23 to an R, G, B control circuit 24 to control the brightness of an R, a G, and a B signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal image display device for displaying an image using a liquid crystal panel.

[0002]

2. Description of the Related Art Conventionally, since a liquid crystal image display device using a transmissive or projection type liquid crystal panel can obtain a bright display, a direct view type liquid crystal television receiver or a projection type liquid crystal projector is used as a display device instead of a cathode ray tube. It has come to be used for etc. However, since the liquid crystal panel has a narrower range of input voltage that can express gradation compared to a cathode ray tube, it tends to cause blackout and whiteout.

FIG. 4 is a graph of the electro-optical characteristics showing the relative transmittance with respect to the applied voltage of the liquid crystal panel, and the range of the input voltage capable of gradation control is the portion indicated by ΔV in the figure, and the range is narrow.

[0004]

In the conventional liquid crystal image display device, when an image signal having a white saturation point or higher of the liquid crystal panel is input, all the peak portions of the luminance signal are cut off. There is a problem that details are not reproduced at all, and there is a problem that details of dark parts are not reproduced on an entirely dark screen composed of a part close to a black saturation point.

[0005]

In order to solve the above problems, the present invention provides a liquid crystal image display device in which a video signal is displayed using a liquid crystal panel, and a digitized luminance derived from an input video signal. A white peak value detecting means for detecting a white peak value of the input video signal from the signal, an average value detecting means for detecting an average video level of the input video signal, and a black level detection for detecting a black level of the input video signal. Means, a pedestal level detecting means for detecting the pedestal level of the input video signal, and an appropriate video level based on the white peak value, the average video level, the black level and the pedestal level detected by the respective detecting means. And a video control signal calculated by the computing means for controlling the input video signal. A configuration in which a control unit.

Further, the above-mentioned calculating means performs the first control according to the white peak value, the average video level and the black level of the input video signal detected by each detecting means, based on the regular video signal of the pedestal level or higher. A first look-up table for calculating a signal, and a second look-up table for deriving a second control signal according to the optimization condition for driving the liquid crystal image display device based on the first control signal. An arithmetic circuit for calculating a single video control signal based on the second control signal.

[0007]

According to the above construction, the white peak value, the average video level and the black level of the input video signal are detected, and the degree of each is calculated by the calculating means based on the level of the regular video signal above the pedestal level. Since the input video signal is controlled by this video control signal, the driving of the liquid crystal video display device can be optimized so that the details of the bright part and the details of the dark part of the image can be reproduced.

According to the above construction, the white peak value, the average video level and the black level of the input video signal are detected, and based on the level of the regular video signal equal to or higher than the pedestal level, the first level corresponding to each level is detected. 1 control signal is derived from the first look-up table, and from the second look-up table, a second control table is generated in accordance with the driving optimization condition of the liquid crystal image display device set in advance according to the first control signal. The control signal is derived, and based on this second control signal, an arithmetic circuit performs arithmetic processing based on a predetermined algorithm for each function, and a single video control signal is derived for each function. The control means controls the input video signal by the control means to perform optimum control of driving of the liquid crystal video display device.

[0009]

FIG. 1 is a block diagram of an embodiment of the present invention. In FIG. 1, an input video signal from a television signal demodulation circuit or the like supplied from a video input terminal T is quantized by sampling in an analog / digital (hereinafter referred to as A / D) conversion circuit 1 to obtain an 8-bit signal. It becomes a digital signal and is supplied to the Y / C separation circuit 2.

The Y / C separation circuit 2 separates a luminance signal Y and a chrominance signal C, which are supplied to a video signal processing circuit 3 at the next stage and demodulated into R, G, B signals, and R, G, B signals. It is supplied to the control circuit 24. The R, G, B control circuit 24 makes it easier to see an image reproduced on the liquid crystal panel 25 by various control signals such as a contrast control signal, a brightness control signal, and a gamma correction control signal from the arithmetic circuit 23 described later. In addition, the level and bias of the R, G, and B signals supplied from the video signal processing circuit 3 are controlled, and the contrast and brightness are controlled.

In the liquid crystal panel 25, a plurality of pixels arranged in a matrix form horizontal and vertical drive circuits (not shown).
Line-sequentially driven by the R, G, B control circuit 2
A color image is displayed according to the corrected R, G, and B signals from 4.

On the other hand, the luminance signal Y composed of an 8-bit digital signal separated by the Y / C separation circuit 2 is passed through a screen area dividing section 4 to a peak detection circuit 5 for detecting a white peak value of the luminance signal. Are supplied to an average value detection circuit 6 for detecting the average level of the luminance signal Y, a black level detection circuit 7 for detecting the black level of the luminance signal, and a pedestal detection circuit 8 for detecting the pedestal level of the luminance signal. It

The peak value, the average value and the black level of the luminance signal Y detected by the peak detection circuit 5, the average value detection circuit 7 and the black level detection circuit 7 are determined by the pedestal level detected by the pedestal detection circuit 8. The correction calculation circuit 9 corrects and calculates the true video signal level excluding the sync signal level, and stores the true video signal level in the peak data register 10, the average value data register 11, and the black level data register 12, respectively.

In the figure, 13 is the average value data register 11 described above.
2 is a look-up table for outputting a control signal with a degree of μ ₁₀ as shown in FIG. 2A when the average video level APL stored in is a high value, and 14 is stored in the average value data register 11. Average video level A
When PL is a low value, it is a look-up table that outputs a control signal of the degree μ ₂₀ as shown in FIG. 2B, and 17 is the average video level APL stored in the average value data register 11. When the value is neither high nor low, the lookup table outputs a control signal of the degree μ ₃ as shown in FIG. 2C.

Reference numeral 15 in the drawing indicates a control signal of a degree μ ₁₁ as shown in FIG. 2D when the black level of the luminance signal Y stored in the black level data register 12 has a high value. Reference numeral 16 is an output look-up table, and when the black level of the luminance signal Y stored in the black level data register 12 has a low value, a control signal of a degree μ ₂₁ as shown in FIG. It is a lookup table to be output.

Reference numeral 18 in the drawing indicates the lookup table 1 described above.
Reference numeral 20 is a control circuit which compares the control signals μ ₁₀ and μ ₁₁ output from 3 and 15 and outputs the control signal with the lower control level μ _{1 as} a control signal. 3 is a look-up table for deriving a control value output E ₁ as shown in FIG. 3A according to the signal degree μ ₁ .

Reference numeral 19 is a comparison circuit for comparing the degree μ ₂₀ and μ ₂₁ of the control signals output from the look-up tables 14 and 16 and outputting the lower degree as the control signal of the degree μ _2. 3 is a lookup table for deriving a control value output E ₂ as shown in FIG. 3B in accordance with the degree μ _{2 of the} control signal derived from the comparison circuit 19, and 22 is an output from the lookup table 17. ₃ is a lookup table for deriving a control value output E ₃ as shown in FIG. 3C according to the degree μ _{3 of the} control signal to be generated.

Reference numeral 23 is an input signal for the control signals of the degrees μ ₁ , μ ₂ , μ ₃ and E ₁ , E ₂ , E ₃ output from the comparison circuits 18, 19 and the look-up tables 17, 20, 21, 22. And (μ ₁ E ₁ + μ ₂ E ₂ + μ ₃ E ₃ ) / (μ ₁ + μ ₂ + μ
₃ ) is a weighted average calculation and outputs a brightness control signal E _BR.
The brightness control signal E _BR from 3 is R, G,
It is supplied to the B control circuit 24 to control the brightness of the R, G, B signals.

Next, the operation in the case of performing the brightness control of the R, G, B signals with the above configuration will be described. First, the following rules A, B, and C are set as conditions for determining the brightness control output. Rule A: Brightness is lowered when the average video level APL is high and the black level is high. Rule B: Brightness is increased when the average video level APL is low and the black level is low. Rule C: When the average image level is neither high nor low, the brightness is left unchanged (standard value).

With regard to rule A, the output of the look-up table 13, that is, the degree μ ₁₀ where the average video level APL is high, is compared with the output of the look-up table 15, that is, the degree μ ₁₁ where the black level is high, and the degree is determined. The lower one is the degree of rule A μ ₁ . The control values output E ₁ for the degree mu ₁ derived from the look-up table 20 as shown in FIG. 3 (a), supplied to the arithmetic circuit 23 together with the degree mu ₁ of said rules A.

Next, regarding rule B, the output of the look-up table 14, that is, the degree of the average video level APL being low μ _20, and the output of the look-up table 16,
That is, the degree μ ₂₁ of the low black level is compared, and the lower degree is set to the degree μ _{2 of the} rule B. The control values output E ₂ for the degree mu ₂ derived from the look-up table 21 as shown in FIG. 3 (b), supplied to the arithmetic circuit 23 together with the degree mu ₂ above rule B.

Rule C is shown in FIG. 3 (c) in contrast to the degree μ ₃ shown in FIG. 2 (c) in which the output of the look-up table 17, that is, the average video level APL is neither high nor low. A control value output E ₃ having such a constant value is derived from the lookup table 22,
It is supplied to the arithmetic circuit 23 together with the degree μ ₃ derived from the lookup table 17.

In the arithmetic circuit 23, the comparison circuit 1
8, 19 and the degrees μ ₁ , μ ₂ , μ ₃ supplied from the look-up table 17 and the look-up table 20,
Based on the degrees E ₁ , E ₂ and E ₃ supplied from 21, 22,
Performs weighted average calculation (μ ₁ E ₁ + μ ₂ E ₂ + μ ₃ E ₃ ) /
(Μ ₁ + μ ₂ + μ ₃ ) to brightness control output E
_It is derived as _BR and supplied to the R, G, B control circuit 24 to control the brightness of the R, G, B signals.

Therefore, when the degree of the rule A is highest, the brightness is lowered when the average video level APL is high and the black level is high, and the contrast is lowered when the white peak level is high. The liquid crystal panel 25 can reproduce the bright part of the image in detail within the driving range corresponding to ΔV in FIG.

Similarly, when the average image level APL is low and the black level is low, the brightness is increased, and when the average image level is neither high nor low, the brightness is controlled as it is, so that the image is bright. It is possible to reproduce the details of both the dark and dark areas.

Although the brightness control has been described above, the contrast control can be performed by configuring the contrast control unit 26 in the same manner as the brightness control. The rule in this case is, for example, as follows. Good. Rule D: When the white peak brightness level is high, the contrast is lowered. Rule E: Low white peak level and average video level APL
If is low, increase the contrast. Rule F: If the white peak level is neither high nor low, standardize the contrast.

Also, gamma correction of the liquid crystal panel can be realized by configuring the gamma control unit 27 in the same manner as described above, and the optimum display according to the contents of various images can be performed. You can

[0028]

Since the present invention has the above-mentioned structure, even when a video signal having a white saturation point or higher of the liquid crystal panel is input,
It is possible to reproduce the peak part of the luminance signal, and it is possible to reproduce the details of the dark part even on an entirely dark screen composed of the part close to the black saturation point, which significantly improves the display quality of the liquid crystal image display device. be able to.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a characteristic diagram of a first look-up table used in the present invention.

FIG. 3 is a characteristic diagram of a second lookup table used in the present invention.

FIG. 4 is a characteristic diagram of a liquid crystal image display device.

Claims (2)

[Claims] 1. A white peak for detecting a white peak value of an input video signal from a digitized luminance signal derived from the input video signal in a liquid crystal video display device for displaying a video signal using a liquid crystal panel. Value detection means, average value detection means for detecting the average video level of the input video signal, black level detection means for detecting the black level of the input video signal, and pedestal level for detecting the pedestal level of the input video signal A detection means, and a calculation means for calculating a video control signal for obtaining an appropriate video level based on the white peak value, the average video level, the black level and the pedestal level detected by the detection means.
A liquid crystal image display device, comprising: a control unit that controls an input image signal according to the image control signal calculated by the calculation unit. 2. The liquid crystal image display device according to claim 1, wherein the calculating means calculates the white peak value of the input image signal detected by each detecting means, the average image level and the black level on the basis of the normal image signal having a pedestal level or higher. First according to the degree of level
A first look-up table for deriving a control signal of
A second look-up table for deriving a second control signal according to the driving optimization condition of the liquid crystal image display device based on the first control signal, and a single look-up table based on the second control signal. It is composed of an arithmetic circuit for calculating a video control signal.