JPH05188352A - Luminance correcting device in liquid crystal image display device - Google Patents

Abstract

PURPOSE:To constitute the device so that not only a video signal but also a soft-ware of a computer are visible in a natural state by controlling a reference voltage generating part, and applying a correction to an input signal of a linear luminance characteristic so that the luminance characteristic becomes linear. CONSTITUTION:Based on an instruction of a luminance correcting changeover switch, a control circuit 13 of an LCD(liquid crystal image display device) driver IC 11 controls a reference voltage generating part 14, applies a correction by which a luminance characteristic becomes a gamma value in consideration of a transmission factor characteristic of an LCD 12 to an input image signal of a luminance characteristic to which a reverse gammacorrection is applied, and applies a correction by which the luminance characteristic becomes linear in consideration of the transmission factor characteristic of the LCD 12 to an input image signal of a linear luminance characteristic. Accordingly, in the case a linear input image signal which is not subjected to a reverse gamma correction such as a software of a computer is displayed on an LCD monitor, the luminance characteristic is corrected linearly, and an image being free from a sense of incompatibility in a gradation display and a color display is obtained.

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 (L
The brightness correction device for CD), in particular, the correction is performed so that the brightness characteristic has a γ value according to the input image signal,
Alternatively, the present invention relates to a brightness correction device in a liquid crystal image display device that performs correction so as to be linear.

[0002]

2. Description of the Related Art A conventional LCD brightness (equivalent to transmittance) correction will be described. FIG. 2 and FIG. 3 are diagrams showing respective examples of the brightness (which is equivalent to the transmittance) correction of the LCD. In these figures, the horizontal axis represents the input signal voltage (Vsig) and the vertical axis represents the brightness. A is L
CD original signal (transmittance) characteristic, B indicates a signal correction characteristic necessary for the luminance characteristic for the input signal (input image signal) (Vsig) to become a straight line C, and D indicates the input signal (input image signal) ( The luminance characteristic with respect to Vsig) has a γ value of about 2.
2 shows the signal correction characteristic required to obtain the characteristic E of 2.

Conventionally, when an input signal is displayed on an LCD monitor, an input signal that has undergone inverse γ correction on the sending side, such as a video signal, is input in consideration of the transmittance characteristic A peculiar to the LCD. By correcting the brightness of the input signal in the internal circuit of the LCD monitor so that the LCD brightness characteristic for the signal becomes D in FIG. 3, the brightness characteristic of the LCD monitor itself becomes
As shown by E in FIG. 3, the characteristic has a γ value of about 2.2, that is, the characteristic is almost equal to that of the CRT. Therefore, in the LCD monitor, the input video signal has a linear and accurate display characteristic.

However, with respect to an input signal having a linear luminance characteristic which is not subjected to the inverse γ correction, the display characteristic on the LCD monitor becomes E itself in FIG. 3 due to the influence of the transmittance characteristic A inherent to the LCD. This is a serious problem in gradation display and color display. Therefore, for an input signal having a linear luminance characteristic, the transmittance characteristic of the LCD is taken into consideration, and correction is performed so that the LCD luminance characteristic becomes B in FIG. 2C
The linear characteristics as shown in (3) are used to obtain a natural image display.

By the way, in the conventional LCD monitor, it is the current situation that the above-mentioned input signal is set in advance so that either the brightness correction B or D can be performed.

Next, an example of a conventional LCD monitor is shown in FIG. FIG. 4 is a schematic view of a main part showing an example of a brightness correction device in a conventional LCD monitor. In the figure, 1 is L
This is a CD driver IC, and this LCD driver IC1
Are digital signals R, G, as input signals from the outside.
B (in the case of an analog signal, it is converted into a digital signal by an A / D converter in advance) is supplied. LCD
The driver IC 1 latches the input digital signals R, G, B, decodes the input signal by a built-in D / A converter, and supplies the signal to the signal electrodes X _{1 to} X ₁₉₂₀ of the LCD 2. The reference voltage generating unit 3 D / A converter in the LCD driver IC1 is composed of a resistor R ₂₁ to R _2n, by setting the resistance ratio of the resistors R ₂₁ to R _2n, brightness correction characteristic B or Only one side of D is uniquely set. Reference numeral 4 denotes a scan driver IC, which supplies the output (scan signal) of the scan driver IC 4 to the signal electrodes Y _{1 to} Y ₄₈₀ of the LCD 2.

In the conventional LCD monitor having the above-mentioned structure, the main focus is generally on viewing video signals.
The brightness is corrected so that the transmittance characteristic of the LCD is similar to that of the conventional CRT. That is,
In general, since the video signal is subjected to inverse γ correction on the sending side in accordance with the CRT, the resistors R _{21 to} R _2n of the reference voltage generating unit 3 are adjusted so that the γ value of the brightness characteristic on the LCD side becomes about 2.2.
The resistance ratio is set and the brightness correction D is performed.

[0008]

The LCD of FIG. 4 described above.
In the monitor, generally, the reference voltage generator 3 can perform the brightness correction D shown in FIG. 3 in accordance with the video signal. However, unlike the case of computer software, the brightness correction characteristic is not taken into consideration for an input signal to which gradation is digitally applied. Therefore, in this LCD monitor, as in the case of computer software, an input signal that digitally gradations has a disagreement in gradation display and color display. was there.

Further, when the LCD monitor of FIG. 4 is set so as to be able to perform the brightness correction B of FIG. 2 on an input signal having a linear brightness characteristic, the inverse γ-corrected video signal is processed. 3 has the drawback that the brightness correction D of FIG. 3 cannot be performed and a linear display characteristic cannot be obtained.

[0010]

A brightness correction device in a liquid crystal image display device according to the present invention comprises a control circuit 13 as a control means, and a reference voltage generator 14 of a D / A converter as a brightness adjustment means. Is characterized by.

[0011]

In the brightness correction device in the liquid crystal image display device having the above-described structure, the control circuit 13 of the LCD driver IC 11 controls the reference voltage generator 14 to perform the inverse γ correction based on the instruction of the brightness correction changeover switch. The input image signal having the brightness characteristic is corrected so that the brightness characteristic becomes the γ value in consideration of the transmittance characteristic of the LCD 12, and the transmittance of the LCD 12 is applied to the input image signal having the linear brightness characteristic. Considering the characteristics, correction is performed so that the luminance characteristics become linear.

Therefore, a linear input image signal that has not been subjected to the inverse γ correction like the software of a computer is subjected to LC
When displaying on a D monitor, an image having no discomfort in gradation display and color display can be obtained by performing correction so that the luminance characteristic becomes linear. Therefore, on the LCD monitor, both the video signal and the computer software can be viewed in a natural state.

[0013]

Embodiments Next, embodiments of the present invention will be described with reference to FIGS. FIG. 1 is a schematic view of a main part showing an embodiment of a brightness correction device in a liquid crystal image display device according to the present invention. In the figure, an input signal from the outside is L as a digital signal R, G, B (in the case of an analog signal, converted into a digital signal by an A / D converter in advance).
It is supplied to the CD driver IC 11. LCD driver I
The C11 latches the input digital signals R, G, B, decodes the input signal by a built-in D / A converter, and supplies the signal to the signal electrodes X _{1 to} X ₁₉₂₀ of the LCD 12. The basic voltage generator 14 of the D / A converter built in the LCD driver IC 11 includes resistors R _{11 to} R _1n , resistors R _{21 to} R _2n, and switches SW _{1 to} SW _n.
Composed of.

Here, the resistance R₁₁~ R_1nAbout
Curve of the brightness correction characteristic B of FIG. 2 with respect to the force signal (Vsig)
The resistance ratio and resistance values are set as plotted above.
Resistance R_{twenty one}~ R_2nFor input signal (Vsig)
Is plotted on the curve of the luminance correction characteristic D in FIG.
The resistance ratio is set as follows. The resistance R_{twenty one}~ R _2n
Is the resistance R in the case of the brightness correction characteristic D in FIG._{twenty one}~ R_2n
Is the same as.

The control circuit 13 in the LCD driver IC 11 sends out a control output CONT based on an instruction from a brightness correction changeover switch (not shown) connected to the LCD driver IC 11. Switch SW ₁ ~ S
W _n is a resistance R due to this control output CONT.
The fixed contacts a or b on the _{11 to} R _1n side or the resistors R _{21 to} R _2n side can be switched all at once. Further, the scan driver IC 15 supplies a scan signal to the electrodes Y _{1 to} Y ₄₈₀ of the LCD 12.

Next, the operation will be described. The control circuit 13 in the LCD driver IC 11 sends the control output CONT to the reference voltage generator 14 based on an instruction from a brightness correction changeover switch (not shown), and switches the switches SW _{1 to} SW _n of the reference voltage generator 14 all together. Then, control is performed so as to switch to the fixed contact a or b on the side of the resistors R _{11 to} R _1n or the side of the resistors R _{21 to} R _2n .

Here, when the switches SW _{1 to} SW _n are simultaneously switched to the fixed contacts a on the resistors R _{11 to} R _1n side,
The brightness correction of the characteristic B of FIG. 2 is performed. Also, switch S
W _{1 to} SW _n are fixed contacts b on the resistance R _{21 to} R _2n side, for example.
When all are switched to, the luminance correction of the characteristic D of FIG. 3 is performed.

Therefore, when displaying an input signal that has not been subjected to the inverse γ correction on the LCD monitor as in the software of a computer, the switches SW _{1 to} SW _n are set to the resistance R ₁₁ by a brightness correction changeover switch (not shown). ~ R
LCD driver I so that it switches to fixed contact a on the _1n side.
When C11 is instructed, the control circuit 13 in the LCD driver IC 11 sends out the control output CONT to switch the switches SW ₁ to SW _n to the fixed contacts a on the resistors R _{11 to} R _1n side. As a result, the brightness correction of the characteristic B is performed and L
In addition to the original characteristic A of the CD 12, the luminance characteristic of the LCD monitor becomes a linear characteristic as shown in C of FIG. 2, and a natural image display can be obtained.

Further, when displaying an input signal which has been subjected to inverse γ correction like a video signal on an LCD monitor, a switch SW is switched by a brightness correction changeover switch (not shown).
_When the LCD driver IC 11 is instructed to switch _{1 to} SW _n to the fixed contacts b on the side of the resistors R _{21 to} R _2n , the LCD
The control circuit 13 in the driver IC 11 sends out the control output CONT to switch the switches SW ₁ to SW _n to the resistor R.
Switch to fixed contact b from _{21 to} R _2n side. As a result, the luminance correction of the characteristic D is performed, and together with the original characteristic A of the LCD 12, the luminance characteristic of the LCD monitor becomes as shown in E of FIG. 3 (characteristic of γ value of about 2.2), which is linear. Display characteristics can be obtained.

The brightness correction changeover switch (not shown) may be a cyclic changeover switch such as a tact switch, or a mechanical changeover switch such as a slide switch, a seesaw switch, or a toggle switch. Good.

As can be seen from the above description, when a linear input image signal that has not been inversely γ-corrected is displayed on the LCD monitor as in software of a computer, the brightness is corrected so that the brightness characteristic becomes linear ( By applying B) in FIG. 2, an image having no discomfort in gradation display and color display can be obtained. Therefore, on the LCD monitor, both the video signal and the computer software can be viewed in a natural state.

In this embodiment, the LCD driver IC
A brightness correction changeover switch (not shown) connected to 11 has a brightness characteristic γ value of about 2.2 according to an input image signal.
The control circuit in the LCD driver IC 11 is selected (instructed) whether to perform the brightness correction (D in FIG. 3) so as to be equal to or the brightness correction (B in FIG. 2) to be linear. 13 detects this and switches the switches SW _{1 to} SW _n of the reference voltage generator 14, but the present invention is not limited to this, and the control circuit 13 in the LCD driver IC 11 automatically inputs the input image signal. Brightness correction (γ in FIG. 3) such that the γ value is approximately 2.2, or linear correction (B in FIG. 2).
Switch S of the reference voltage generator 14
W ₁ may be carried out ~SW _n switching control of.

[0023]

As described above, according to the brightness correction device in the liquid crystal image display device of the present invention, the brightness adjustment means is based on the control signal from the control means, and the input image having the brightness characteristics subjected to the inverse γ correction. The signal is corrected so that the luminance characteristic has a γ value, and the input image signal having a linear luminance characteristic is corrected so that the luminance characteristic is linear. When displaying a linear input image signal that has not been subjected to inverse γ correction as in software, the liquid crystal image display device is corrected so that the luminance characteristic becomes linear, and gradation display and color display are performed. It is possible to obtain an image without a feeling of strangeness. Therefore,
On the liquid crystal image display device, both video signals and computer software can be viewed in a natural state.

[Brief description of drawings]

FIG. 1 is a schematic view of a main part showing an embodiment of a brightness correction device in a liquid crystal image display device according to the present invention.

FIG. 2 is a diagram showing an example of LCD brightness correction.

FIG. 3 is a diagram showing another example of LCD brightness correction.

FIG. 4 is a schematic view of a main part showing an example of a brightness correction device in a conventional LCD monitor.

[Explanation of symbols]

 11 LCD driver IC 12 LCD 13 Control circuit 14 Reference voltage generator

Claims (1)

[Claims] 1. A control means for sending a control signal to correct a brightness characteristic according to an input image signal, and an input image having a brightness characteristic subjected to inverse γ correction based on the control signal from the control means. And a brightness adjusting means for correcting the signal such that the brightness characteristic has a γ value and correcting the input image signal having the linear brightness characteristic so that the brightness characteristic becomes linear. And a brightness correction device in a liquid crystal image display device.