KR100273476B1 - Reverse gamma circuit - Google Patents

Abstract

PURPOSE: A reverse gamma characteristic circuit is provided to be capable of performing a compensating function so that the light emission characteristic has a linearity when broadcasting signals or video signals are implemented through a panel type display device. CONSTITUTION: A decimal number converting circuit(11) converts binary number carry color signals into decimal number. An operating circuit(12) operates gamma characteristic data from the decimal number data. An integerizing circuit(13) integerizes the gamma characteristic data. A binary number converting circuit(14) converts the integerized decimal data into binary data. In addition, the operating circuit(12) must satisfy a following equation: Y=isqr(P)/K, wherein Y is output of the operating circuit, P is a variable determining a gradient of the gamma characteristic, and K is a coefficient.

Description

Inverse gamma characteristic circuit

The present invention relates to an inverse gamma (γ) characteristic circuit applied to a plasma display (PDP) or liquid crystal display (LCD) of a TV. In particular, the input and output characteristics of a PDP or LCD screen can be implemented to show linearity. It relates to an inverse gamma (γ) characteristic circuit.

Current TV products are mainly made of CRT (cathode ray tube), but before and after 2000, thin-walled TVs are expected to enter the growth phase.

TV (television) image display by CRT is an excellent display device for TV image display, in the case of color CRT, brightness of more than 100ft-L (white display) on average, contrast ratio of 30: 1 or more and lifetime of 10,000 hours or more are guaranteed. to be.

However, since the CRT is a vacuum tube, its weight and volume are large and its mechanical strength is maintained, it is difficult to make the screen completely flat and there is a problem of distorting the periphery. In addition, there is a problem that a high voltage is required to excite the phosphor with an electron beam and emit light to make an image, and thus it is difficult to be suitable for the IC of recent electronic circuits.

BACKGROUND ART Panel-type display devices such as electronic luminescence, gas discharge (plasma display), liquid crystal, and the like have a possibility of fundamentally solving such problems of CRT, and have been studied and developed from an early age.

The plasma display (PDP) displays a letter or a figure by using a glow discharge to arrange the light emitting points in a matrix form by the electrode lines arranged in the X and Y directions and to control the digital signal for the presence or absence of voltage applied to each light emitting point. As it is a device to make a light source, it usually uses neon gas, so the light emission is red. The electrode can be wrapped with an insulating film to have a memory function, which is used for a terminal device of a computer. It is called PDP because it is made flat.

In addition, the liquid crystal display (LCD) has various methods depending on the type of liquid crystal and the optical effect, but the twisted nematic method is widely used at present. The principle of operation is that when no voltage is applied between the transparent electrodes, the molecular orientation is twisted by 90 °, and the incident light entering the liquid crystal rotates by 90 ° according to the twist, passes through the liquid crystal and passes through the polarizing plate passing only through the horizontal plane. When a voltage is applied to this, 90 ° of distortion is eliminated and the deflection surface of the incident light does not rotate, so that the deflection plate cannot pass. The liquid crystal display device uses the principle of making the contrast according to the voltage applied to the liquid crystal. A color liquid crystal display device is constructed by attaching red, blue, and green filters to each pixel to form three primary colors, and forming transistors for controlling the contrast of each pixel on a transparent substrate.

The panel display device (PDP, LCD) and the CRT have different light emission characteristics. As shown in FIG. 1A, the CRT itself has a non-linear characteristic in which the Vo (output voltage) characteristic of Vi (input voltage) is not linear. Has adult characteristics. Therefore, the current broadcast signal outputs the characteristics opposite to the CRT from the camera. This is illustrated well in Figure 2b.

Therefore, when the broadcast signal is viewed through the CRT, the linear characteristic as shown in Fig. 1C is obtained. The signal having the characteristics as shown in FIG. 1B includes not only the current broadcast signal but also a general video signal.

On the other hand, since the light emitting characteristics of the panel display device (representative example, plasma display) have a linearity as shown in FIG. 2A, the screen is displayed through the panel display device without supplementing the current broadcast signal or video signal. In this case, since a non-linear screen is output (see FIG. 2B), an inverse gamma characteristic circuit is required to compensate for this.

Accordingly, the present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to compensate for the light emission characteristic of the broadcast signal or the video signal through the panel display device. To provide an inverse gamma characteristic circuit.

In order to achieve the above object, the present invention includes a decimal conversion circuit 11 for converting a binary carrier color signal into a decimal number; An arithmetic circuit (12) for calculating gamma characteristic data from the decimal data; A water purifying circuit (13) for purifying the gamma characteristic data; And a binary conversion circuit 14 for converting the integerized decimal data into binary data.

In addition, the calculation circuit 12 must satisfy the following equation, that is, Y = i ^P / K. Here, Y denotes an output of the calculation circuit, i denotes a decimal three-color signal data value, P denotes a variable for determining a slope of a gamma characteristic, and K denotes a coefficient.

Other objects and advantages of the invention will be described below and will be appreciated by the practice of the invention. Furthermore, the objects and advantages of the present invention can be realized by means and combinations indicated in the appended claims.

FIG. 1A shows light emission characteristics of a cathode ray tube (CRT), FIG. 1B shows characteristics of a broadcast imaging tube, and FIG. 1C shows input / output characteristics when a broadcast signal is viewed as a CRT.

FIG. 2A shows light emission characteristics of the panel type display device, and FIG. 2B shows inverse gamma (γ) characteristics.

3 is a block diagram of a TV to which a panel display device is applied.

FIG. 4 shows a block diagram of an inverse gamma (γ) characteristic circuit applied to FIG.

<Explanation of symbols for the main parts of the drawings>

1: Video signal amplification circuit 2: Color reproduction circuit

3: analog-to-digital conversion circuit 4: reverse gamma (γ) characteristic circuit

5 panel display 11 decimal conversion circuit

12: operation circuit 13: integer circuit

14: binary conversion circuit

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3 shows a block diagram of a TV to which a panel display device is applied. As shown in FIG. 3, a TV including a panel display device includes an image signal amplifying circuit 1 and a color reproduction circuit 2. And an analog-to-digital conversion circuit 3, an inverse gamma characteristic circuit 4, and a panel display device 5.

The video signal amplifying circuit 1 is for amplifying the voltage level of the video signal so that the panel type display device can recognize the color signal, and the color reproducing circuit 2 separates the carrier color signal included in the video signal and outputs the three primary colors. This circuit reproduces with (R, G, B) signals.

In addition, the analog-to-digital conversion circuit 3 is for converting an analog signal into a digital signal, and the inverse gamma characteristic circuit 4 is a circuit for compensating for the nonlinearity of light emission characteristics of the panel display device. to be.

4 shows an internal block configuration of the inverse gamma characteristic circuit 4 adapted to FIG. 3, the inverse gamma characteristic circuit 4 of the present invention includes a decimal conversion circuit 11 and an arithmetic circuit. (12), an integerization circuit 13, and a binary conversion circuit 14.

The decimal conversion circuit 11 is for converting binary tricolor signals R, G, and B into a decimal number through an analog-digital conversion circuit.

In addition, the calculation circuit 12 is for calculating the signal data converted into a decimal number by the following equation (1).

Y = i ^P K ㆍ ··················

Here, the coefficient K represents a numerical value obtained by dividing the P power of the three primary color signal data value i, P represents a numerical value associated with the gamma characteristic, and Y represents an arithmetic output value.

The K value is a coefficient that becomes 255 after the maximum data value of 8 bits passes P and passes through the gamma characteristic circuit. (The maximum value of 8 bits is 255.) That is, for example, if P = 2, the K value is 255. Therefore, in the present invention, it has 255≤K≤4072.

The P value is a value for determining the slope of the gamma characteristic, and preferably 2? P? 2.5 in the present invention.

The integerization circuit 13 is intended to take only integers from the output values calculated via the calculation circuit 12. The implementation of such an integerization circuit 13 includes a method of comparing an integer and a data value by a program and a method of removing a fractional part below an integer by a program.

The binary conversion circuit 14 is a circuit for converting and outputting an integer value output by the integer conversion circuit 13 into an 8-bit binary number. The binary data signal output through the binary conversion circuit 14 is in inverse gamma corrected state.

The present invention is not limited to the above-described embodiments, and various modifications and variations are made by those skilled in the art to which the present invention pertains without departing from the spirit and scope of the appended claims. Of course it is possible.

As described above, the present invention improves brightness characteristics by inversely gamma correcting light emission characteristics of a panel type display device having linearity through an inverse gamma characteristic circuit.

Claims (1)

A decimal conversion circuit 11 for converting a binary carrier color signal into a decimal number; An arithmetic circuit (12) for calculating gamma characteristic data from the decimal data; A water purifying circuit (13) for purifying the gamma characteristic data; And a binary conversion circuit 14 for converting the integerized decimal data into binary data; The arithmetic circuit (12) is an inverse gamma (γ) characteristic circuit, characterized in that the following formula (1) is satisfied. Y = i ^P K (however, 2≤P≤2.5 and 255≤K≤4072 are satisfied) (1) Herein, Y represents an output value of the calculation circuit, I represents a decimal three primary color signal data value, P represents a variable for determining a slope of a gamma characteristic, and K represents a coefficient.

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