KR100560883B1 - Apparatus and method of flicker reduction in projection tv set - Google Patents

Abstract

The present invention relates to an apparatus for removing flicker and an afterimage generated when the power is turned on / off in a projection type TV using a liquid crystal display (LCD), and the flicker; It relates to an afterimage removal method.

According to the present invention, in the projection type image display apparatus using the LCD, the liquid crystal array is stabilized by applying a charge and discharge signal before inputting an image signal to the LCD module in the initial stage of turning on the power, and then shifts to the lamp power on and TV power on states. Controlling to suppress flicker phenomenon, and after the lamp power is turned off in the initial stage of turning off the TV, suppressing the afterimage generation by controlling the liquid crystal to be rearranged and then transitioned to the power-off state by applying a charge and discharge signal to the LCD module. It is characterized by.

LCD, Projection TV, Flicker, Afterimage

Description

Flicker and afterimage removal device and method of projection image display device {APPARATUS AND METHOD OF FLICKER REDUCTION IN PROJECTION TV SET}

1 illustrates a general structure of a thin film transistor liquid crystal display (TFT-LCD).

2 is a block diagram showing the configuration of a conventional liquid crystal display driving circuit.

Fig. 3 is a block diagram showing a driving circuit configuration of the projection image display device of the present invention.

4 is a flowchart showing a driving control method for flicker and image retention in a projection image display device of the present invention;

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

30: LCD driver 31: signal input unit

32: charge, discharge control signal generator 33: control unit

34: timing generator 35: video processor

36: level converter 37: sample & holder

38: LCD module

The present invention relates to an apparatus for removing flicker and an afterimage generated when the power is turned on / off in a projection type TV using a liquid crystal display (LCD), and the flicker; It relates to an afterimage removal method.

As a projection image display device, for example, a projection TV receiver may provide a large screen (screen) that cannot be realized by a general CRT. The projection color image display apparatus performs an electrical / optical signal processing on an image signal to optically output R, G, and B image signals through an image display element (PRT, LCD, etc.) at the end, and outputs the output image (optical signal). ) Is projected on the front projection screen via an optical system such as a reflector to display a desired color image.

As described above, a thin film transistor liquid crystal display (TFT-LCD) used in a projection image display device is formed by injecting and sealing liquid crystals between upper and lower substrates that maintain a predetermined cell gap therebetween.

1 shows one example of a TFT-LCD structure.

The lower substrate is composed of a polarizing plate 1, a transparent substrate 2, a TFT array 3 and an alignment film 4, and a backlight 12 is provided at the rear. In the TFT array 3, a thin film transistor and a pixel based on pixel electrodes connected to the thin film transistors are vertically and horizontally arranged on a transparent substrate, and a plurality of gate bus lines and data bus lines electrically connected to each thin film transistor are provided. Formed. Here, the gate electrode of the thin film transistor provided near the intersection point of the gate bus line and the data bus line is branched at the gate bus line, and the source electrode is branched at the data bus line.

The upper substrate is composed of a polarizing plate 5, a transparent substrate 6, a color filter 7, a common electrode 8, and an alignment film 9. A color filter is a color filter having one of R, G, and B colors on a transparent substrate, and a plurality of color filters are formed corresponding to each pixel, and a common electrode and an alignment film are sequentially formed thereon.

The liquid crystal 10 is injected between the upper substrate and the lower substrate, and the liquid crystal is sealed, and a spacer 11 is provided between the upper substrate and the lower substrate to maintain a constant cell gap. .

The liquid crystal display device configured as described above generates a voltage difference between a pixel electrode positioned at the pixel and a common electrode of the color filter substrate by rearranging only the liquid crystal corresponding to the portion of the pixel. Will be expressed.

That is, when one gate bus line and one data bus line are selected and voltage is applied, only the thin film transistor to which the gate voltage is applied is turned on, and the pixel electrode connected to the drain electrode of the turned on thin film transistor is charged by the voltage on the data bus line. And the voltage is applied only to the liquid crystal portion between the pixel electrode and the common electrode. Accordingly, the angle of the liquid crystal molecules is changed and light is transmitted or blocked according to the angle of the liquid crystal molecules. By selectively controlling the blocking, a desired image is displayed.

Fig. 2 shows the liquid crystal display device as described above together with the driving circuit. That is, the liquid crystal display device includes a liquid crystal panel 20, a scan line driver circuit 21, and a signal line driver circuit 22 capable of driving the liquid crystal panel. The liquid crystal panel 20 has a structure in which a plurality of scan lines 23 and a plurality of signal lines 24 are intersected in a matrix form on a substrate, and thin film transistors 13 and pixels are provided at the intersections thereof. The scan line driver circuit 21 sequentially applies a scan signal for applying an on signal to the gate of the thin film transistor to the scan line, and the signal line driver circuit 22 is driven by the scan signal. The image signal is applied to the signal line so that the image signal can be transferred to the pixel through the thin film transistor 13.

The liquid crystal display device sequentially applies a scan signal to the scan line 23 of the liquid crystal panel 20 in the scan line driver circuit 21 so that all thin film transistors 13 connected to the scan line to which the scan signal is applied are conductive. When turned on, the signal applied to the signal line 24 of the liquid crystal panel 20 is transmitted to the pixel through the source and the drain of the conductive thin film transistor 13.

According to this operating principle, it is possible to drive all the pixels of the liquid crystal panel by applying pulses sequentially to all the gate electrodes and applying signal voltages to the corresponding source electrodes. In this way, after displaying one frame of image, another frame is displayed continuously, thereby making it possible to display moving images.

In the display of such an image, only a large amount of information such as color display cannot be displayed by white and black driving alone. Therefore, the gradation display is used, in which there are a few more intermediate states between the white and black states. In the case of a black and white liquid crystal display, for example, when an intermediate voltage is applied between white and black, an intermediate state such as gray exists to display information.

In order to obtain the intermediate value of the voltage, there is a method of adjusting the intensity of the voltage applied to the liquid crystal and a method of adjusting the width of the voltage pulse.

In the case of a color liquid crystal display, color display is determined by the degree of gray scale display.

When using a 6-bit drive IC, 64 gradations can be produced, and in a monitor or audio / video (AV) product requiring full color, 256 gradations can be achieved at more than 13 million colors.

As described above, since the LCD displays information on the screen by adjusting the magnitude of the voltage applied to the liquid crystal, the gray scale is adjusted based on characteristics in which light is transmitted according to the voltage.

In the liquid crystal display, color filters corresponding to three primary colors of light of R (Red), G (Green), and B (Blue) are used to realize color. Colors are expressed by arranging RGB color filters adjacently and controlling brightness by applying a signal of a corresponding color to each color filter.

To summarize the process of color expression, the amount of light passing through the color filter is controlled by using a liquid crystal, and the voltage required to operate the liquid crystal is output from a source driver IC so that the pixel TFT Supplied through. In this way, the voltage supplied to the liquid crystal changes the arrangement of the liquid crystal, so that the light transmittance is changed in combination with the combined polarizing plate. In this case, the number of colors that can be expressed is determined by how many stages the liquid crystal can be controlled. For example, in the NW (Normally) ECB mode, when the voltage is not applied, the brightest state is the white state, and when the highest voltage of the driving range is applied, the dark state is the black state. In this case, when the color filter exists for each pixel, applying an intermediate voltage to each color filter pixel may generate an intermediate gray scale according to the combination. Accordingly, brightness and saturation can be adjusted.

The color screen of the TFT-LCD displays the white light of the back light (B / L) 12, the operation of the TFT and the liquid crystal cell that controls the transmittance, and the 3, which passes through the R, G, and B color filters. The addition of primary colors is done through mixed colors.

The color filter has a dye method and a pigment method according to the material of the organic filter used in manufacturing, and can be classified into a dyeing method, a dispersion method, an electrodeposition method, and a printing method depending on the manufacturing method. The most common method used in the preparation is the pigment dispersion method. Pigment particles are generally opaque by scattering light, but when the particle size is smaller than the wavelength of light, the pigment particles are transparent by transmitting light, so that the smaller the particle size, the higher the transparency and excellent dispersion characteristics.

As described above, the liquid crystal display is an electro-optical device for driving by applying a voltage to the liquid crystal molecules injected into a constant gap between the lower substrate and the upper substrate.

However, when such a liquid crystal display is applied to a projection TV receiver, flicker and an afterimage occur at the initial stage of power on and off of the TV receiver. This is because the liquid crystal display is a type in which a liquid crystal is injected between two substrates facing each other, as described above. to be. In addition to being functional as a capacitive element, the liquid crystal array after the initial arrangement of the liquid crystal and the driving termination (that is, when the power is turned off) becomes a temporary unstable state (uncontrolled state) Afterimages are displayed on the screen together with the flicker phenomenon.

That is, in the conventional LCD projection TV receiver, since the input signal is passed as it is when passing the signal to the LCD module, the LCD module cannot sufficiently charge and discharge when the LCD module is supplied with power. Flicker and residual images were caused by the voltage difference between the liquid crystal electrode and the liquid crystal electrode.

SUMMARY OF THE INVENTION An object of the present invention is to remove flicker and afterimages occurring at the initial stage of power on and off in a projection type image display using a liquid crystal display.

Another object of the present invention is to control the video signal to be supplied to the TFT LCD to control the charging and discharging in the early stage of turning on and off the power of the TV receiver, so as to suppress the flicker phenomenon and the generation of afterimages. The present invention provides a flicker and afterimage removal device of a projection image display device and a method thereof.

Still another object of the present invention is to arrange the liquid crystal array of the TFT LCD in advance by adjusting the charge and discharge signals before inputting the image signal, thereby preventing flicker and afterimages. The present invention provides a removal apparatus and a method of removing the same.

In order to achieve the above object, the flicker and afterimage removing apparatus of the projection image display apparatus of the present invention is a projection image display apparatus including an LCD module and a lamp, and inputs a signal for receiving data and a clock and a synchronization signal for image projection. Means for driving the LCD module using the image data inputted through the signal input means, a clock and a synchronization signal, and the lamp through the signal input means according to a power on / off initial command input by a user. Control means for controlling the charging and discharging of the LCD module before being turned on or off, charge and discharge control to the signal input means for charging and discharging the LCD module according to the control command of the control means Characterized in that it comprises a charge, discharge control signal generating means for supplying a signal.

In addition, the flicker and afterimage removal method of the projection-type image display device of the present invention for achieving the above object, in the flicker and afterimage removal method of the image display device having an LCD module and a lamp, the power-on command of the image display device is input When the lamp is driven, the flicker removing step of supplying the charge and discharge signals of the LCD module to execute the liquid crystal array in advance, the lamp is turned off when the power-off command of the image display device is input, It is characterized in that it comprises a residual image removal step of removing the afterimage by rearranging the electrodes of the LCD module by supplying a charge, discharge signal for the LCD module before it.

delete

In addition, in the flicker and afterimage removal method of the projection display device of the present invention for achieving the above object, the flicker removal step is performed after the initialization of the circuit at power-on, before the light source (lamp) on, and the afterimage removal step is It is characterized in that it is executed after the light source (lamp) is turned off and before the power is turned off.

EXAMPLE

3 is a block diagram showing the configuration of a device for removing flicker and afterimage in the projection image display apparatus according to the present invention, in which a projection image display apparatus using a liquid crystal display device processes digital image data for driving an LCD module. It is divided into a digital board and a drive board for driving the LCD module by inputting the digital image data, the part for performing the LCD drive by processing a signal from the digital board of the front end not shown here to the drive board, That is, the configuration of the drive board (drive board) is shown.

As shown in Fig. 3, the projection image display device according to the present invention includes an LCD driver 30 for driving an LCD module for displaying an image, and data, clock, and synchronization signals for the image display from a digital board in front. A signal input unit 31 for receiving an input to the LCD driver 30, a charge and discharge control signal generator 32 for inputting a control signal for removing flicker and afterimage to the signal input unit 31, and Control unit for controlling the charge and discharge control signal generator 32 to remove flicker and afterimages at the initial stage of TV power on and off, and to control the signal input unit 31 and the LCD driver 30 to display a predetermined image ( 33).

On the other hand, the LCD driver 30 is a timing generator 34 for generating a clock and the synchronization signal for a predetermined image display using the clock and the synchronization signal input from the signal input unit 31, and the signal input unit 31 The video processor 35 processes the image data inputted from the control unit, and performs the uniformity, gamma correction, and the like, and the signal voltage level output from the timing generator 34 to the LCD module. A level shifter 36 suitably changed, a sample & holder 37 for processing a sample & hold for driving an LCD module, and image data output from the video processor 35; And an LCD module 38 driven according to the output of the level converter 36 and the sample & holder 37 to display a predetermined image.

Referring to FIG. 3, the operation of driving the LCD module in the projection image display device according to the present invention will be described.

First, the signal input unit 31 receives digital data, a clock signal, and a synchronization signal input to the drive board from a digital board in the front stage, and inputs the input digital image data, clock, and synchronization signal to the LCD driver 30. Let it be.

The timing generator 34 generates and outputs predetermined clocks, drive signals, synchronization signals, etc., which are necessary for LCD driving using the input clock and synchronization signal. That is, the timing of the synchronization and clock signals is adjusted in order to display an image in accordance with a desired output format on the drive board. For example, in order to display an image in an LCD module in accordance with the format of 480I, a synchronization and Since the clock needs to be generated, this is generated by the timing generator 34.

The level converter 36 converts the level of the signal voltage passed from the timing generator 34 to a level suitable for driving the LCD module 38. For example, the data processed through the general processing process mainly has a signal voltage level of 3V to 5V, whereas the LCD module 38 has a signal voltage level of 15V to 17V, so the signal level of 3V to 5V is 15V. It converts the signal level of ~ 17V.

On the other hand, the video processor 35 performs signal processing suitable for displaying on the LCD module 38 with respect to the image data input from the signal input unit 31, for example, uniformity, gamma correction, etc. for the image data To do. The image data processed by the video processor 35 is converted into an analog signal of a predetermined level for driving the liquid crystal of the LCD module 38 through the sample & holder 37. That is, in order to display the data optimized for the display of the LCD module 38 on the LCD module 38 through video processing in the video processor 35, the digital video data is converted to analog data (Sample & Hold). Supply to the LCD module 38.

The LCD module 38 is driven according to the output of the level converter 36 and the output of the sample & holder 37 so that a predetermined image is displayed, and the displayed image is displayed on the front of the device using the optical system as described above. By projecting onto the screen, an image of a desired large screen is displayed on the screen.

At this time, the control unit 33 (CPU) controls the signal input unit 31, the timing generator 34, the video processor 35, and the like appropriately, so that the image processing by the above-described signal processing and driving of the LCD module is performed. Make it happen.

On the other hand, the control unit 33 controls the charging and discharging signal generation unit 32 in the initial stage of turning on the power of the device, or the power of the device off, the LCD module 38 through the signal input unit 31. By rearranging the liquid crystals, the control to suppress flicker and the afterimage is performed. Here, the charge and discharge signal generation unit 32 is configured separately from the control unit 33, but the control unit 33 receives a predetermined liquid crystal charge and discharge control signal that can replace the generation of the charge and discharge signals or the generation of the signal. It can also be implemented by controlling the signal input unit 31 directly.

4 is a flowchart showing a control procedure of the control unit 33 for removing flicker and afterimages when the power is turned on or off in the projection type image display device according to the present invention. Referring to FIG. 4 and FIG. Looking at the control procedure of the flicker and afterimage removal according to the invention in more detail as follows.
Flicker and afterimage removal method of the image display device according to the present invention is large. It consists of a flicker removal step (step 41-step 44) for removing flicker, and an afterimage removal step (step 45-step 49) for removing an afterimage.

In the flicker removal step, first, the power on step 41 is a step in which a power on key (command) of the device is input. When the power-on key is input, the controller 33 initializes each component IC of the digital board and the drive board (step 42). Then, the control unit 33 inputs the charge and discharge control signals to the signal input unit 31 through the charge and discharge control signal generator 32 (step 43). According to the input of the charge and discharge control signals, the LCD driving unit 30 is configured with the liquid crystal array of the LCD module 38 in advance. In this way, the lamp (light source) is turned on and the TV on state is achieved. Proceed to step 44 and 45.

That is, by controlling the signal input of the LCD module 38 at the moment when the control unit 33 detects the power-on signal, the liquid crystal arrangement of the LCD module 38 is made in advance during the transient period, and then the lamp is turned on. By turning on and providing the LCD drive and the image signal (data), it becomes possible to remove and compensate for the flicker that occurred when the LCD drive and the data signal passed.

In addition, in the afterimage removing step, the controller 33 searches whether the power-off key is input (step 46). Upon detecting the power-off signal of the device, the control unit 33 turns off the lamp (step 47), and then charges and discharges the signal input unit 31 through the charge and discharge control signal generator 32 as described above. Input the signal (step 48). In response to the input of the charge and discharge control signals, the liquid crystal array of the LCD module 38 is made in advance in the LCD driving unit 30, and the state shifts to the TV off state in the state where the liquid crystal arrangement is made in advance (step 49).

That is, the control unit 33 turns off the lamp (light source) at the moment of detecting the power-off signal and then gives a signal to control the signal input of the LCD module 38, so that the liquid crystal arrangement of the LCD module 38 is made in advance during the transient period. When the power is turned off, the afterimage generated when the LCD is driven and the data signal passes can be eliminated and compensated.

According to the present invention, a flicker and an afterimage generated at the time of power ON / OFF are removed in a projection type TV using a liquid crystal display (LCD), thereby turning on the power of the device. It solves the problem that the flicker phenomenon that occurs when the display is unobtrusive, and also improves the display quality of the device by removing the afterimage that occurred when the device is turned off.

Claims (4)

In the projection image display device having an LCD module and a lamp, Signal input means for receiving data and a clock and a synchronization signal for projecting an image; LCD driving means for driving the LCD module by using the image data input through the signal input means, a clock, and a synchronization signal; Control to output a charge and discharge control signal so that the liquid crystal array constituting the LCD module is made before the lamp is turned on or off through the signal input means according to a power on / off initial command input by a user. Way; And, And a charge and discharge control signal generation means for supplying a charge and discharge control signal to the signal input means to charge and discharge the LCD module according to a control command of the control means. Flicker and afterimage removal device. delete A flicker and afterimage removing method of an image display device having an LCD module and a lamp, A flicker removing step of supplying a charge and discharge control signal to the LCD module to execute the liquid crystal array in advance when the power on command of the image display device is input, and then receiving an image signal; And, When the power-off command of the image display device is input, the lamp is turned off, and afterimages are supplied to charge and discharge the LCD module to turn off the image display device after the liquid crystal of the LCD module is supplied before the power is turned off. The flicker and afterimage removal method of the projection image display device characterized in that it comprises a removing step. 4. The method of claim 3, wherein the flicker removing step is performed after circuit initialization at power-on and before light source (lamp) is turned on, and the afterimage removing step is performed after power source is turned off and before power-off. Flicker and afterimage removal method of the projection image display device characterized in that.

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