JPH1011025A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform optimum luminance corrections on respective pictures when a computer picture and a natural picture are composed to be displayed on the same screen. SOLUTION: Analog picture data are inputted to an input terminal In and a control signal is inputted from the external to a control signal input terminal Cont. The picture signal is inputted to a luminance correction circuit 102 or a luminance correction circuit 103 according to the kind of the signal and a γ1 correction or a γ2 correction is applied to the signal in respective circuits. Next, signals in the correction circuits are converted into parallel signals suited for displays in a serial-parallel converting part 104 and, succeedingly, an inversion signal is formed in a data transforming part 105 to be supplied to an LCD panel 106 together with a non-inversion signal. Composed pictures are displayed on the panel like the figure (b).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly to a display device which receives a composite signal of a computer image signal such as a character or a figure and a natural image signal such as a television or a video and displays the composite image. Liquid crystal display device configured as described above.

[0002]

2. Description of the Related Art A liquid crystal display device has a luminance characteristic different from that of a CRT.
In order to match the brightness characteristics with the brightness, it is necessary to perform the brightness correction in the liquid crystal display device. Conventional brightness correction will be described with reference to FIGS. 8 and 9, the horizontal axis indicates the input signal voltage, and the vertical axis indicates the relative luminance. When an input signal having a characteristic D having a γ value of 1 is input as a relative luminance characteristic to the input signal, the CRT displays a characteristic F having a γ value of about 2.2.
Is displayed in accordance with. As described above, since the luminance characteristic of the liquid crystal display device is different from the above, by correcting the input signal of the characteristic D for the characteristic E inside the liquid crystal display device, the γ value almost equivalent to that of the CRT is obtained. 2.2
The luminance characteristics of F are obtained.

However, when such a correction is made, C
In a liquid crystal display device having an inferior contrast ratio to RT, an image in which it is difficult to determine a halftone gradation is more difficult than a CRT. Therefore, in a natural image such as a television or a video in which the halftone is regarded as important, as shown in FIG. 9, the contrast ratio of the halftone is larger than the characteristic F of which the relative luminance characteristic with respect to the input signal is about 2.2. The characteristic G is corrected in the liquid crystal display device so that the characteristic H is displayed. However, computer images such as characters and figures have a large amount of binary data in black and white and a small number of halftones. It becomes an image.
Therefore, conventionally, the characteristic E is corrected for a computer image, and the characteristic G is corrected for a natural image, so that good display can be performed on each image. Thus, on a monitor of a personal computer or the like, a natural image may be superimposed on a computer image such as a character or a diagram to display a plurality of images on the same screen, or these images may be switched and displayed. , In such cases,
Either E or G has been corrected. For this reason, the display quality of either image is degraded.

FIG. 10 is a schematic block diagram of a conventional liquid crystal display device for analog signal processing. As shown in FIG. 10, a horizontal driver (H driver) is provided around the LCD panel 9 in order to drive the LCD panel 9.
7, 7 and a vertical driver (V driver) 8 on the side.
Is arranged. Signals for driving these drivers are formed in the control unit 6 and an analog interface (hereinafter, AIF) processing unit 12. The control unit 6 receives a horizontal synchronization signal Hsync, a vertical synchronization signal Vsync, and a clock CLK, and inputs a start signal VSP and a clock VCK to the V driver 8.
Start signal HSP and clock HCK are supplied to drivers 7 and 7.
Has been supplied. The control section 6 supplies a control signal to the AIF processing section 12 to control the operation. The AIF processing section 12 performs a luminance / correction section 11 for performing a luminance correction on the input image signals (R, G, B) for the liquid crystal display device, and performs a serial / parallel conversion on the input image signals by a sample hold circuit. It comprises a serial / parallel converter 4 and a data inverter 5 for inverting and non-inverting an analog RGB signal with respect to a reference voltage.

In the liquid crystal display device for analog signal processing configured as described above, the luminance correction is performed by the luminance correction unit 11 of the AIF processing unit 12, and the image displayed on the liquid crystal display device is composed of characters, figures, and the like. Computer images and television,
Depending on whether the image is a natural image such as a video or the like, a correction suitable for the image has been fixedly given to the luminance correction unit to perform the correction. That is, in the conventional liquid crystal display device, even when different types of images are switched and displayed,
Alternatively, even when different types of images are combined and displayed on the same screen, only the same luminance correction can be performed. However, when a computer image or a natural image is switched and displayed, it has been proposed to switch the luminance adjustment and perform the display after performing the luminance correction suitable for each image (for example, Japanese Patent Application Laid-Open No. Hei 5-18835).
2).

[0006]

In the conventional liquid crystal display device, since the relative luminance characteristics are fixed, a composite screen of a computer image such as a character or a figure and a natural image such as a television or a video is displayed on the same screen. When displaying, the display quality of one of the images is degraded. In other words, if the brightness characteristics are such that the contrast ratio of the halftone is large so that the halftone of the natural image can be easily distinguished, the computer image has a relative brightness characteristic different from that of the CRT. If the image is uncomfortable on display and color display, and if luminance correction suitable for a computer image is performed, the contrast of a halftone image of a natural image is lower than that of a CRT and the display quality is deteriorated. Would. Therefore, an object of the present invention is to provide a liquid crystal display device capable of displaying computer images and natural images on the same screen.
Both images are to be able to display high-quality display images.

[0007]

A liquid crystal display device according to the present invention receives a composite signal of image information from different sources and displays the composite image on the same screen.
It is characterized in that luminance correction suitable for each of image information of different sources is performed. Then, it is preferable that the brightness correction for each source can be adjusted independently.

[Operation] In the liquid crystal display device having the above-described structure, a selection is made such that, for example, a computer image has a luminance characteristic of about 2.2 with a γ value by a switching signal from the outside. , A luminance conversion characteristic that increases the contrast ratio of the halftone is selected. As a result, it is easy to determine the halftone gradation of the natural image, the screen quality can be improved, and the display can be performed without any discomfort on the gradation display and color display when displaying the computer image. In addition, by making it possible to make independent adjustments to different luminance correction characteristics for computer images and natural images, fine adjustments can be made for different image tones without correcting the input screen signal itself. Brightness correction can be performed.

[0009]

FIG. 1A is a block diagram for explaining an embodiment of the present invention. Analog image data compatible with the CRT is input to the input terminal In, and a control signal is input from the outside to the control signal input terminal Cont. The image signal is input to the luminance correction circuit 102 or the luminance correction circuit 103 in the switch 101 according to the type of the signal, and γ ₁ or γ ₂ is corrected in each circuit. Next, the signal is converted into a parallel signal suitable for display by the serial / parallel converter 104, and then an inverted signal is formed by the data converter 105.
06. FIG. 1B shows a display screen on an LCD panel based on image data to which such conversion has been added. In this case, a composite signal of two different types of image signals is input, and the respective signals are displayed on the LCD panel after being subjected to optimal luminance correction.

[0010]

Next, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 2 is a block diagram showing a first embodiment of the present invention. As shown in FIG. 2, the input analog image signals (R, G, B) are supplied to H drivers 7 after being processed in an AIF processing unit 10 controlled by a control unit 6. . The AIF processing unit 10 includes a luminance correction unit 11, a serial / parallel conversion unit 4 that performs serial / parallel conversion on an input image signal by a sample / hold circuit, and inversion / non-inversion of an analog RGB signal with respect to a reference voltage. And a data inverting section 5 for performing the following. The brightness correction unit 11 includes a changeover switch 1 that is switched by an external control signal.
And a first luminance correction unit 2 and a second luminance correction unit 3 having different correction characteristics, and the first and second luminance correction units 2 and 3 are respectively provided with first and second adjustment units 2a and 3a. Have been. The start signals HSP, VSP, clocks HCK, VCK generated in the control section 6 are supplied to H drivers 7, 7 and a V driver 8.

In the liquid crystal display device configured as described above, the brightness correction section 11 changes the input image signal to be input into the first brightness correction section 2 and the second brightness correction section 2 by the changeover switch 1 based on an external control signal. The luminance signal is input to one of the luminance correction units 3 and luminance correction suitable for each input signal is performed. Here, the first brightness correction unit 2 is selected when a computer image such as a character or a figure is input, and the second brightness correction unit 3 is selected when a natural image such as a television or a video is input. (See FIGS. 8 and 9) to the input signal having the characteristic of E or G. The first brightness correction unit 2 includes a first adjustment unit 2.
a, and the second brightness correction unit 3 is provided with a second adjustment unit 3a, so that each correction characteristic can be adjusted.

FIG. 3 is a circuit diagram of the brightness correction unit 11 used in the first embodiment of the present invention. As shown in FIG. 3, the luminance correction circuit includes a circuit in which a differential amplifier including three blocks having different voltage gains is connected to a resistor R1 serving as a common load. The offset voltages VL, VM, VH corresponding to the level of the input image signal VIN are input to the transistors Q7, Q4 or Q5, Q2 on the reference potential input side of each differential amplifier, and the characteristics near black, halftone, and white are obtained. Producing. The input image signal VIN is input to the input transistors Q1, Q3, and Q6 of each differential amplifier. The output signal obtained from the load resistor R1 is taken out via the emitter of the emitter follower transistor Q12. Transistors Q8 to Q11 serving as current sources are connected to the respective differential amplifiers and the emitter follower transistors. The offset voltage VM is input to either Q4 or Q5 by a switch switched by a control signal. Here, it is assumed that the upper contact of the switch SW is selected when a computer image is input, and the lower contact of the switch SW is selected when a natural image is input.

The input / output voltage characteristics of the luminance correction circuit will be described with reference to FIG. FIG. 4 illustrates the first brightness correction unit 2 of the brightness correction characteristic unit 11 of the liquid crystal display device according to the present embodiment.
5 shows input / output voltage characteristics of the second luminance correction unit 3. Now, when a computer image is input as VIN, the switch SW is synchronized with the computer image by a control signal.
Is selected. At this time, the output voltage of the luminance correction circuit has a slope A at the offset voltage VL, a slope B1 at the offset voltage VM, and an offset voltage VH.
The characteristic obtained by superimposing the slope C at the time of
The correction of the characteristic of E can be added to the input signal of the characteristic of D in FIG. Therefore, it is possible to perform signal correction necessary for obtaining a characteristic F having a γ value of about 2.2 as a relative luminance characteristic with respect to the input signal. Here, the slope B1 is a gain of the differential amplifier at the offset voltage VM: R1 / (R4 + R
5).

On the other hand, when a natural image is input as VIN, the switch SW is switched to the lower contact by a control signal in synchronization with the input. As a result, the output voltage has a characteristic obtained by superimposing the slope A at the offset voltage VL, the slope B2 at the offset voltage VM, and the slope C at the offset voltage VH.
The G characteristic can be corrected for the input signal having the D characteristic. Therefore, it is possible to perform signal correction necessary for obtaining the relative luminance characteristic H for enhancing the contrast in the halftone. Here, the slope B2 is a gain of the differential amplifier at the offset voltage VM: R1 / (R4 + R
6).

Next, the operation of the first and second adjusters 2a and 3a on the first and second luminance correctors 2 and 3 in the present embodiment will be described. In the present embodiment, the adjustment of the brightness correction unit is performed by changing the offset voltage VM.
Now, as shown in FIG. 5, the offset voltage VM is changed to VM '.
, The curve B translates downward as shown in FIG. Thereby, the gradients B1 and B2 in FIG.
Can be changed, and fine adjustment can be made to the correction characteristics of the first luminance correction unit 2 and the second luminance correction unit 3.

FIG. 6 is a circuit diagram of a luminance correction unit according to a second embodiment of the present invention. In the figure, the same parts as those in the circuit diagram of FIG. 3 in the previous embodiment are denoted by the same reference symbols, and duplicate description will be omitted. This embodiment is different from the previous embodiments in that the emitter resistors R5 and R6 of the transistor to which the offset voltage VM is input are formed as variable resistors. With this configuration, the inclinations B1 and B2 in FIG. 4 can be adjusted independently, and the first luminance correction unit 2 and the second luminance correction unit 2 can be adjusted independently.
It becomes possible to finely adjust the correction characteristics of the brightness correction unit 3 independently.

FIG. 7 is a circuit diagram of a brightness correction unit according to a third embodiment of the present invention. Also in this figure, the same parts as those in the circuit diagram of FIG. 3 are denoted by the same reference symbols, and duplicate description will be omitted. The difference between the circuit of the first embodiment and the circuit of the first embodiment is that the offset voltages input to the bases of the transistors Q4 and Q5 are VM1 and VM2 and can be changed independently. With this configuration, also in the present embodiment, the correction characteristics of the first luminance correction unit 2 and the second luminance correction unit 3 can be finely adjusted independently. The switches used in the above embodiments may be analog multiplexers that control analog switches with digital signals. Alternatively, a relay may be used if the operation speed is sufficient.

[0018]

As described above, the liquid crystal display device according to the present invention selects a characteristic having a luminance characteristic of about 2.2 for a computer image by a control signal from the outside, For a natural image, luminance correction suitable for each source can be performed on the same screen, such as selecting a luminance correction characteristic that increases the contrast ratio of a halftone. Therefore, according to the present invention, as in the case of correcting the luminance of the composite image with one correction characteristic,
The contrast in the halftone in the natural image is not weakened and the gradation display and the color display in the computer image are not uncomfortable, and the whole screen is maintained in a good display state when displaying the composite screen. Will be able to do it.

[Brief description of the drawings]

FIG. 1 is a block diagram and a display screen diagram for describing an embodiment of the present invention.

FIG. 2 is a block diagram of a first embodiment of the present invention.

FIG. 3 is a circuit diagram of a brightness correction unit according to the first embodiment of the present invention.

FIG. 4 is an explanatory diagram of the operation of the luminance correction unit circuit shown in FIG. 3;

FIG. 5 is an explanatory diagram of the operation of the luminance correction unit circuit shown in FIG. 3;

FIG. 6 is a circuit diagram of a brightness correction unit according to a second embodiment of the present invention.

FIG. 7 is a circuit diagram of a luminance correction unit according to a third embodiment of the present invention.

FIG. 8 is an explanatory diagram of luminance correction of the liquid crystal display device.

FIG. 9 is an explanatory diagram of luminance correction of the liquid crystal display device.

FIG. 10 is a block diagram of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Changeover switch 2 1st brightness correction part 2a 1st adjustment part 3 2nd brightness correction part 3a 2nd adjustment part 4,104 serial / parallel conversion part 5,105 data inversion part 6 control part 7 horizontal driver 8 vertical driver 9, 106 LCD panel 10 Analog interface (AIF) processing unit 11 Brightness correction unit 12 Conventional analog interface processing unit 101 Switch 102, 103 Brightness correction circuit

Claims (4)

[Claims] 1. A liquid crystal display device in which a synthesized signal of image information from different sources is input to the same screen and the synthesized image is displayed on the same screen, a luminance correction suitable for each of the image information of different sources is applied. A liquid crystal display device characterized by being used. 2. A luminance correction unit for applying different luminance corrections to image information from different sources, and a serial / parallel converter for converting a serial signal output from the luminance correction unit into a parallel signal.
2. The device according to claim 1, further comprising: a parallel conversion unit; a data inversion unit configured to receive an output signal of the serial / parallel conversion unit to form an inverted signal; and a control unit configured to control an operation of each of these units. Liquid crystal display. 3. The liquid crystal display device according to claim 2, wherein the brightness correction section includes a switch that is switched by an external control signal, and the switching changes the brightness correction. 4. The apparatus according to claim 1, wherein adjustment of luminance correction for each source can be performed independently.
The liquid crystal display device as described in the above.