KR20070076892A - A liquid crystal system and a method for controlling it's contrast - Google Patents

Abstract

An LCD(Liquid Crystal Display) system and a contrast control method thereof are provided to increase the contrast of the LCD system and to display the gray scale at a black part by a histogram algorism if the quantity of the light projected to a screen of the LCD system is reduced. An LCD system is composed of a variable condensing lens(150) for regulating the quantity of the projected light according to the brightness of a screen and controlling an area of the light projected on a panel(140), in proportion to the quantity of the light emitted from a light source(120); a driving unit(154) for driving the variable condensing lens; and a servo motor(156) driving the variable condensing lens according to a control signal of the driving unit.

Description

A liquid crystal system and a method for controlling it's contrast

1 is a schematic view of a conventional LCD system.

2 is a schematic view showing gamma characteristics of a conventional LCD system.

3A to 3C are diagrams showing a decrease in visual contrast with increasing screen brightness in a conventional LCD system.

4 shows an LCD system according to the invention.

5 shows contrast characteristics of an LCD system according to the present invention.

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

100: image processing unit 110: LCD driver

120: light source 130: condensing lens

140: LCD panel 150: variable condensing lens

152: APL processing unit 154: variable condensing lens driving unit

156: servo motor

The present invention relates to a liquid crystal display (LCD), and more particularly, to an apparatus and method for improving contrast in an LCD system.

1 is a view schematically showing a conventional LCD system. Referring to FIG. 1, a conventional LCD system is described as follows.

The conventional LCD system includes an image processor 100, an LCD driver 110, a light source 120, a condensing lens 130, and an LCD panel 140. The operation of the LCD system is described as follows. First, a signal is processed by the image processor 100 to match an input signal to a display format and to correct an appropriate image quality, and then processes a signal and a clock to completely match the characteristics of the LCD panel 140. Transmit to LCD driver 110. The LCD driver 110 performs gamma correction, contrast correction, brightness processing, and uniformity correction to match the transmission characteristics of the LCD panel 140. The LCD driver 110 also generates a timing signal to match the driving characteristics of the LCD panel 140 and sends the timing signal to the LCD panel 140. The gamma correction described above refers to converting and outputting a signal input from a video display device in accordance with human visual characteristics.

After the gray characteristics of the image are generated by the above-described process, when light is projected from the light source 120, the light is condensed to the condensing lens 130 to maximize the projected light. Gather as much as possible to match the size and project on the LCD panel 140, the image is output and projected on the screen to distinguish the gray level (grey level).

However, the above-described conventional LCD system has the following problems.

FIG. 2 is a diagram schematically illustrating gamma characteristics of a conventional LCD system, and FIGS. 3A to 3C are diagrams illustrating a decrease in visual contrast according to an increase in screen brightness in a conventional LCD system. Hereinafter, the problems of the conventional LCD system will be described with reference to FIGS. 2 and 3A to 3C.

The gamma characteristic curve of FIG. 2 is a curve showing an output value obtained from a screen by projecting light from a black level (brightness '0') to a white level (brightness '100%') and weighting an appropriate gamma value. The curve shown by the dashed line 200 is a gamma graph that is ideally intended to be obtained in an LCD system. Due to the inherent characteristics of the LCD, light flows to the surroundings in the dark part (black gradation) and thus gamma characteristic as shown by the solid line 250. Is lowered.

The above is the biggest factor of contrast reduction in LCD, and in order to increase the contrast in LCD system, even if a large amount of light is emitted from the light source, only the numerical contrast is slightly improved, and the visual contrast is bad. It is for the reason mentioned above.

In FIG. 3A, a black level (brightness '0') is displayed in the middle of the screen, and a white level (brightness '100%') is displayed in the remaining part. As the brightness of the white level increases, the black level is shown in FIG. 3B. As shown in FIG. 3C, the brightness gradually increases due to the influence of the ambient brightness, and as the brightness increases, the contrast worsens.

Therefore, to maintain excellent contrast, the brightness of the screen should be reduced as much as possible even if the brightness of the screen is slightly damaged.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide an LCD system and a method of driving the same, which greatly improve contrast.

In order to achieve the above object, the present invention comprises a variable condensing lens (condensing lensing) for adjusting the amount of light projected according to the brightness of the screen; And it provides a LCD system comprising a drive unit for driving the variable condensing lens.

The variable condensing lens preferably adjusts the area of light projected on the panel in proportion to the amount of light projected from the light source.

The LCD system may further include a servomotor which drives the variable condensing lens according to a control signal of the driving unit.

The driving unit preferably includes a voltage driving unit for sensing a level requiring brightness adjustment and a timing driving unit for synchronizing sync with the LCD.

The LCD system preferably further includes an average picture level (APL) processing unit that stores and outputs average brightness with respect to an input signal to determine contrast amplification characteristics.

The present invention provides a driving method of an LCD (Liquid Crystal Display) system, characterized in that to improve the contrast (contrast) of the screen by adjusting the amount of light projected on the panel according to the brightness of the screen.

In the method of driving the LCD system, it is preferable to adjust the amount of light projected on the panel by adjusting the position of the variable condensing lens.

The present invention provides a method for processing an input signal processed by an image processor, the method comprising: storing and outputting average brightness in an APL processor to determine contrast amplification characteristics; It provides a contrast adjustment method of the LCD system comprising the step of adjusting the position of the variable condensing lens in the LCD driver in accordance with the contrast amplification characteristics.

In the adjusting of the position of the variable condensing lens, it is preferable to adjust the position of the variable condensing lens by driving a servomotor.

In the variable condensing lens, when the amount of light projected from the light source increases, it is preferable to narrow the distance from the panel.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention that can specifically realize the above object will be described. The same components as in the prior art are given the same names and the same reference numerals for convenience of description, and detailed description thereof will be omitted.

4 is a view showing an LCD system according to the present invention. Referring to Figure 4 describes the LCD system according to the present invention.

The LCD system according to the present invention includes an image processor 100, an average picture level (APL) processor 152, an LCD driver 110, a variable condensing lens driver 154, a servo motor 156, a light source 120, The variable condensing lens 130 and the LCD panel 140 are included.

The image processing unit 100 processes the input image signal in accordance with a display format and corrects it to an appropriate image quality. Subsequently, the APL processing unit 152 processes the input signal to store and output the average brightness information every frame. In detail, the APL processor 152 may classify the received signal into several blocks in one frame, extract average brightness of the actual image, and then determine contrast amplification characteristics in the black and white images. Use a histogram algorithm to ensure In addition, information about the variable condensing lens 150 is extracted to generate and output a DC voltage. In the timing unit of the APL processor 152, the servo motor 156 creates a display clock and horizontal and vertical sinks necessary for precisely matching the synchronization with the LCD panel 140. Transmission to the driver 140 and the condensing lens driver 154.

The image signal processed as described above is transmitted to the LCD driver 110 along with a clock, and is processed to completely match the characteristics of the LCD panel 140. The LCD driver 120 performs gamma correction, contrast and brightness processing, and uniformity correction so as to match the transmission characteristics of the LCD panel 140. In addition, a timing signal is also generated and transmitted to the LCD panel 140.

The variable condensing lens driver 154 includes a voltage driver for detecting a level requiring brightness adjustment and supplying a constant voltage, and a timing driver for synchronizing the sink with the LCD.

Through the above-described process, the DC information and the timing information about the brightness are sent to the variable condensing lens driver 154 to drive the servomotor 156. Accordingly, the servomotor 156 may drive the variable condensing lens 150 by accurate synchronization.

In FIG. 4, the variable condensing lens 150 moves toward the LCD panel 150c according to the screen brightness. Specifically, when the screen brightness is relatively dark, all the light passing through the variable condensing lens 150 is projected onto the LCD panel 140, but as the screen brightness becomes relatively bright, the LCD panel 140 becomes closer to the screen. Move to the position of 150a and 150b. At this time, the light is projected on the 150 'portion of the LCD panel when the variable condensing lens is at the position of 150, but the light is projected on the 150a' portion when the position of the variable condensing lens is 150a, and the 150b 'portion when the variable condensing lens is at the position of 150b. Light is projected on. Therefore, as the amount of light incident on the condensing lens increases, a portion of the incident light is incident on the LCD panel 140 so that a relatively small amount of light is incident, thereby reducing the brightness of the conventional LCD system. Contrast deterioration due to increase can be overcome.

In addition, in order to compensate for a dark screen, a sharper amplification characteristic is applied to the black-side video signal and a predetermined white side signal to compensate for the darkened screen, so that light is less transmitted through the LCD panel 140 so that contrast is not felt. Make it one level higher.

5 is a view showing the contrast characteristics of the LCD system according to the present invention. Referring to Figure 5 describes the contrast characteristics of the LCD system according to the present invention.

Contrast does not increase sharply even when the brightness is increased in the contrast characteristic of the LCD system according to the present invention shown by the solid line 500 '. This can solve the problem of contrast sharply decreasing as the brightness increases in the contrast characteristic of the conventional LCD system shown by the dotted line 500.

The driving method of the LCD system according to the present invention is characterized by improving the contrast of the screen by adjusting the amount of light projected on the panel according to the brightness of the screen, and specifically, by adjusting the position of the variable condensing lens. Adjust the amount of light projected on the panel.

In the contrast adjustment method of the LCD system according to the present invention, the APL processing unit stores and outputs an average brightness of an input signal signal-processed by the image processing unit to determine the contrast amplification characteristic and the LCD driving unit according to the contrast amplification characteristic. Adjusting the position of the variable condensing lens. The adjusting of the position of the variable condensing lens may include adjusting the position of the variable condensing lens by driving the servomotor as described above. Specifically, the variable condensing lens may increase the amount of light projected from the light source. Close the gap with the panel.

As described above, the present invention uses a variable condensing lens and an APL processing unit to appropriately block the amount of light projected to the LCD when the brightness of the screen increases, and in the darkened black portion, the gradation representation is represented by the histogram algorithm. Make it possible. Therefore, in the white part where brightness is generally lowered, the amplification characteristic is more sharply applied in the range where the image of the white part is not saturated so as to have the maximum contrast effect. It will have a clear picture quality competitiveness in the market.

The present invention is not limited to the above-described embodiments, and such modifications are included in the scope of the present invention even if modifications are possible by those skilled in the art to which the present invention pertains.

The effects of the LCD system and its contrast adjustment method according to the present invention described above are as follows.

First, the contrast of the LCD system can be greatly improved.

Second, when the amount of light projected on the LCD system is reduced, the darkened black part can be expressed by histogram algorithm.

Claims (10)

A variable condensing lens for adjusting the amount of light projected according to the brightness of the screen; And Liquid Crystal Display (LCD) system comprising a drive unit for driving the variable condensing lens. The method of claim 1, wherein the variable condensing lens, And an area of light projected on the panel in proportion to the amount of light projected from the light source. The method of claim 1, And a servomotor driving the variable condensing lens in response to a control signal of the driving unit. The method of claim 1, wherein the driving unit, And a voltage driver for sensing a level requiring brightness adjustment and a timing driver for synchronizing sync with the LCD. The method of claim 1, And an average picture level (APL) processing unit which stores and outputs average brightness with respect to an input signal to determine contrast amplification characteristics. A method of driving an LCD (Liquid Crystal Display) system, characterized by improving the contrast of the screen by adjusting the amount of light projected on the panel according to the brightness of the screen. The method of claim 6, And controlling the amount of light projected onto the panel by adjusting the position of the variable condensing lens. Determining, by the APL processor, the contrast amplification characteristics by storing and outputting the average brightness of the input signal processed by the image processor; And adjusting the position of the variable condensing lens in the LCD driver in accordance with the contrast amplification characteristic. The method of claim 8, wherein adjusting the position of the variable condensing lens comprises: And adjusting the position of the variable condensing lens by driving a servomotor. The method of claim 9, wherein the variable condensing lens, When the amount of light projected from the light source is increased, the distance from the panel is narrowed, thereby reducing the amount of light projected on the panel.

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