KR900001586B1 - Drive circuit of lcd shutter with driving method of two frequency - Google Patents

Abstract

The driver utilizing synchronized high and low frequencies includes a discriminating circuit (4) for transmitting a field discriminating signal by checking the vertical synchronous signal, a first multiplexer (7) for selecting low or high frequency generated by a frequency generator according to the field discriminating signal, a second multiplexer (8) for doing the same function as the first multiplexer (7), buffers (10,11) for buffering the output signals of multiplexers, a first liquid cell (12) drived by the effective voltage which is a difference between the signals from a frequency inverter (9) and the first buffer which are received as input voltages of a common electrode and a signal electrode, and a second liquid cell (13).

Description

Liquid crystal shutter driving circuit by 2 frequency driving method

1a and b are frequency characteristics of the liquid crystal dielectric constant and electro-optical characteristics by driving frequency.

2 is a waveform diagram of a television composite video signal.

3 is a circuit diagram according to the present invention.

4 is an operating waveform diagram of FIG.

5 is another embodiment according to the present invention.

6 is an operating waveform diagram of FIG.

* Explanation of symbols for main parts of the drawings

1: Synthetic video signal output circuit 2: Synchronous separation circuit

3: vertical synchronization signal detection circuit 4: left and right image signal discrimination circuit

5: low frequency inversion circuit 6: high frequency oscillation circuit

7, 8: 1st, 2 multiplexer 10, 11: 1st, 2 buffer

9: frequency inversion circuit 12, 13: liquid crystal cell

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal shutter driving circuit of a liquid crystal display for sensing a stereoscopic image, and more particularly to a circuit capable of driving a liquid crystal shutter as a synthesized frequency of high frequency and low frequency.

In general, the three-dimensional stereoscopic image is a trend that is getting a good response to the general viewer by taking a picture of any subject at a different angle at the same time to give a feeling as if seeing the object of the body when viewing with the naked eye.

The 3D video signal can be viewed through a 3D video recording device or recorded on a video recording player using a conversion device for converting 3D video film into a television signal. It is a developing trend.

In addition, the signal converted into the television image signal as described above is a composite image signal obtained by combining a left eye image in one field and a right eye image in two fields from a video signal having a period of one frame. Fid injection is done.

As described above, a conventional liquid crystal display device (a device for driving glasses for viewing a stereoscopic image) for viewing a stereoscopic image when a video signal obtained by synthesizing a video signal synthesized on one frame is scanned into a television is described in FIGS. The left and right liquid crystal shutters, which allow viewing of left and right eye video signals by the detection of the feedback, have been driven with a constant voltage. Therefore, in the conventional liquid crystal display device, when the 1-frame left eye image and the 2-eye right eye image signal are detected as a stereoscopic image by the liquid crystal shutter, the on-off response speed of the liquid crystal shutter is slow. It could not be viewed in 3D image and driving voltage was a problem.

Accordingly, an object of the present invention is to provide a liquid crystal shutter driving circuit by a two-frequency driving method in which a three-dimensional effect is improved by increasing the response speed of a liquid crystal shutter by driving the liquid crystal shutter at a synthesized frequency of high and low frequencies using dielectric anisotropy of the liquid crystal. have.

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

1a and b are frequency characteristic diagrams for the liquid crystal dielectric constant and electro-optic characteristic diagrams according to the driving frequency. In the drawing, reference numeral ε ₀ is the permittivity of the liquid crystal molecules, and ε ₁₁ is a component perpendicular to the long axis direction of the liquid crystal molecules. It is a component parallel to the long axis of a liquid crystal molecule, and Vth is a threshold voltage.

First of all, the dielectric properties of nematic liquid crystals are widely used. If the permittivity ε balanced in the long axis of the molecule is ε, the Np-type nematic is a liquid crystal with a dielectric anisotropy of prus ＂+＂, and the maximum direction of the dipole moment is parallel to the molecular axis. Contrary to the above, the type nematic material has a negative dielectric constant anisotropy and has a structure in which the dipole moment is perpendicular to the molecular axis.

In the liquid crystal having the structure as described above, ε _{11, which} is a component whose horizontal axis is horizontal with respect to the dielectric constant ε ₀ of the liquid crystal molecules (the dielectric constant in the major axis of the molecule), changes as shown in FIG. 1a as the driving frequency f ₀ is higher. The vertical permittivity (vertical permittivity) ε perpendicular to the dielectric constant ε ₀ of the molecule is constant regardless of the driving frequency f ₀ as shown in FIG. 1A.

EBBA + EBCA mixed liquid crystals that are widely known at present are ε ₁₁ > ε at low frequencies, ε ₁₁ << ε at high frequencies, and when the low frequency voltage and the high frequency voltage are applied, the electric field effect of the liquid crystal molecular direction change becomes 90 °. By using this phenomenon, two frequency driving can be used for driving with high response speed.

Meanwhile, referring to FIG. 1B, the light transmittance characteristic of the applied voltage across the liquid crystal is shown as the light transmittance according to the threshold voltage Vth applied to the both ends of the liquid crystal.

Therefore, as described above with reference to FIGS. 1A and 1B, when the voltage applied to both ends of the liquid crystal is high and the frequency of the voltage is high frequency, the liquid crystal has high light transmittance and is accurately turned on and off at a high speed.

2 is a waveform diagram of a composite (synthesized) video signal of a television, (a) shows a first feed signal which is the first feed signal of one frame signal, and (b) shows a second feed of one frame signal. As the second feed signal waveform diagram, EP1a, EP1b, EP2a and EP2b in the reference numerals are equalization pulses and VS1 and VS2 are vertical synchronization signals.

The vertical synchronous signals VS1 and VS2 shown in (a) and (b) have a width of 3H (H: 63.5 Hz), and six pulses (groove pulses) are inserted in the vertical synchronous signal period. . In addition, before and after this vertical synchronization signal, equalization pulses are provided for perfecting interlaced scanning in the pulse group of the vertical retrace signal.

These equalization pulses are also spaced in half of the horizontal line (horizontal synchronization signal: H), so they act as horizontal synchronization signal pulses every other time. Alternate each other in the field.

That is, it is inserted to equalize the difference in the vertical synchronization signal in the even and the odd numbered feeds. The first feed signal such as (a) has a period of 1 / 2H in front of the vertical synchronization pulse VS1. Six equalizing pulse signals and seven equalizing pulse signals exist in the second feed signal such as (b) in front of the vertical synchronization pulse VS2.

In the present invention described later, the vertical synchronization pulse and the equalization pulse before and after the vertical synchronization pulse are called vertical synchronization signals.

FIG. 3 is a liquid crystal drive circuit diagram driven by a two-frequency voltage according to the present invention. The composite video signal outputs a composite video signal obtained by combining a left eye video signal in one frame and a right eye video signal in two frames. An output circuit 1, a synchronous separation circuit 2 for separating and outputting a composite synchronous signal from the output composite video signal, and a vertical synchronous signal detection for inputting the separated output synchronous signal and detecting a vertical synchronous signal therefrom A circuit (3), a left and right image signal discrimination circuit (4) for inputting the detection output vertical synchronization signal and outputting a shield discrimination signal for distinguishing first and second feeds, and a low frequency generating a low frequency signal of a predetermined period The oscillation circuit 5, the high frequency oscillation circuit 6 for generating and outputting a high frequency signal of a predetermined period, and the low and high frequency signals respectively oscillated and output from the low and high frequency oscillation circuits 5-6 are input and left and right images, respectively. The first and second multiplexers 7-8, which multiplex the low and high frequency oscillation signals, and the high frequency oscillation signals output from the high frequency oscillation circuit 6 are inverted by the shield discrimination signal output from the call discrimination circuit 4; Multiplexing output by the frequency inverting circuit 9 for outputting the common voltage of the liquid crystal, the first buffer 10 for buffering the frequency multiplexed by the first multiplexer 7, and the second multiplexer 8 The second buffer 11 buffering the output frequency and the output of the frequency inverting circuit 9 are inputted as a common voltage, and the signal of the frequency buffered output from the first buffer 10 is inputted as a signal voltage and the phase is changed. A first liquid crystal cell 12 driven by two different frequencies, a first liquid crystal cell 12 driven by two different frequencies by inputting the frequency inversion circuit pressure, and the frequency inversion circuit 9, output A common voltage input and comprises a second buffer 11, the second liquid crystal cell 13 to enter a signal of a frequency into a signal voltage that is in phase with each other are driven by a different second frequency that is output from.

In this case, the first and second liquid crystal cells 12 and 13 are generally manufactured in glasses, and when the first liquid crystal cell 12 is turned on (driven), the image of the feed is corrected to the image to the left eye. When the second liquid crystal cell 13 is turned on, the user may watch a video of 2 days with the right eye. In the third diagram, the low frequency oscillation circuit 5 and the high frequency oscillation circuit 6 correspond to the frequency oscillation means.

4 is an operation waveform diagram of each part of FIG. 3, in which the first and second liquid crystal cells 12 and 13 are operated so that the left eye video signal and the right eye video signal can be viewed by the viewer's naked eye by two-frequency driving. This is a waveform diagram showing.

Embodiments of the present invention will be described with reference to the above-described configuration and drawings. As shown in FIG. 4A, a composite video signal obtained by synthesizing a left eye video signal in a first feed and a right eye video signal in a second feed is synthesized in the composite video signal output circuit 1 as shown in FIG. When outputted to the synchronous separation circuit 2, the synchronous separation circuit 2 separately detects the composite synchronous signal from the input composite video signal and outputs it to the vertical synchronous signal detection circuit 3. At this time, the vertical synchronizing signal detecting circuit 3 detects only the vertical synchronizing signal as shown in FIG.

The left and right image signal discrimination circuit 4, which inputs the vertical synchronizing signal detected and output as shown in FIG. 4 (b) by the vertical synchronizing signal detection circuit 3, has a first feed as described above in FIG. Using the different number of equalization pulses (1 / 2H equalization pulse) of the second feed, the first feed (left eye video signal) and the second feed (right eye video signal) are discriminated, and FIG. A shield discrimination signal such as) is output to the first and second multiplexers 7-8. That is, the left and right video signal discrimination circuit 4 outputs 1 feed when the total number of equalization pulses of the vertical synchronization signal input is 18, and 2 feed signals when 19.

On the other hand, the low frequency oscillation circuit 5 oscillates low frequencies such as FIG. 4 (e) continuously and inputs them to the first and second multiplexers 7 to 8, respectively, and the high frequency oscillation circuit 6 is the fourth degree (f). Oscillations such as high frequency are continuously generated and output to the first and second multiplexers 7-8. In the left and right video signal discrimination circuit 4, a shield discrimination signal such as (1) of FIG. 4C is input as a control signal of the first multiplexer 7, and (1) of FIG. When the same inverted feed discrimination signal is input as a control signal of the second multiplexer 8, the first multiplexer 7 selects a high frequency signal oscillated and outputted from the high frequency oscillator circuit 6 to generate a fourth signal (h). A signal such as the same is output to the first buffer 10.

At this time, the second multiplexer 8 selects the low frequency signal output from the low frequency oscillation circuit 5 based on the inverted feed discrimination signal output from the left and right image signal discrimination circuit 4 and outputs the fourth to the second buffer 11. Output as shown in (i).

The first and second buffers 10 and 11 that input the signals input from the first and second multiplexers 7-8, respectively, as illustrated in FIGS. 4 h and i, respectively, buffer the input signals to buffer the input signals. The first and second liquid crystal cells 12 and 13 output the driving frequencies of the signal electrodes 15, respectively.

Therefore, when the left and right image signal discrimination circuit 4 discriminates and outputs the first feed signal in the waveform of (1) of FIG. 4 (c) and (d) and the period of one frame, the first liquid crystal cell 12 is frequency. The characteristics described above with reference to FIG. 1 are driven by the high frequency signal inverted and output as shown in FIG. 4 (g) in the inverting circuit 9 and the high frequency signal which is selectively output as shown in FIG. 4 (h) in the first buffer 10. The liquid crystal having the liquid crystal is turned on to pass through the liquid crystal shutter (OPEN), so that the left eye image signal loaded on the first feed is viewed on the left eye of the viewer. In this case, an effective value appearing between the common electrode 16 and the signal electrode 15 of the first liquid crystal cell 12 as a waveform is shown in FIG. 4 (J).

On the other hand, the second liquid crystal cell 13 is not driven by inputting the low frequency signal buffered and output from the first buffer 11 and the high frequency output from the frequency inversion circuit 9 as a driving voltage as shown in FIG. 4 (i). That is, when outputting the first feed signal, ie, the feed discrimination signal, output from the left and right image signal discrimination circuit 4 as the 1 feed discrimination signal, the common electrode 16 and the signal electrode ( 15) The voltage appearing between both ends is inputted with the driving voltage as shown in FIG.

On the other hand, the left and right image signal discrimination circuit 4 judges that the vertical synchronization signal output from the vertical synchronization signal detection circuit 3 is the synchronization signal of the second feed, and thus (2) and (d) of FIG. As described above, when the feed discrimination signal as shown in (2) is output as the control signals of the first and second multiplexers 7 and 8, respectively, the first multiplexer 7 generates a low frequency oscillation by the input control signal. The signal oscillated and output from the circuit 5 as shown in FIG. 4 (e) is selected as shown in (5) of FIG. 4 (h) and output to the first buffer 10.

At this time, the second multiplexer 11 generates a high frequency oscillation output from the high frequency oscillation circuit 6 by a control signal output from the left and right image signal discrimination circuit 4 as shown in (4) of FIG. It selects as (6) of (i), and outputs it to the 2nd buffer 11.

Accordingly, both ends of the common electrode 16 and the signal electrode 15 are driven to the first liquid crystal cell 12 by the inverted high frequency signal output from the frequency inversion circuit 9 and the low frequency signal selectively output from the first multiplexer 7. The waveform of the driving frequency of the effective value applied to the both ends by inputting the frequency becomes as shown in (7) of FIG. 4 (j), so that the liquid crystal is not driven. At this time, the high frequency of the frequency of the frequency inverting circuit 9 output to the second liquid crystal cell 13 as shown in FIG. 4 (g) and the frequency of the fourth diagram (i) (6) to be selectively output from the second multiplexer 8. The signal is input at both ends.

Therefore, the frequency of the effective voltage applied between the common electrode 16 and the signal electrode 15 of the second liquid crystal cell 12 becomes as shown in (8) of FIG. OPEN and the right eye image signal of the second feed are viewed by the second liquid crystal cell 13.

Accordingly, when the left and right video signal discrimination circuit 4 detects the first feed signal, that is, the feed of the left eye video signal, the second liquid crystal cell 13 is turned off and only the first liquid crystal cell 12 is turned on. When the viewer sees the naked eye and the second feed signal is input, the first liquid crystal cell 12 is turned off, and the second liquid crystal cell 13 is turned on to view the right eye image signal.

Therefore, two-dimensional images can be viewed as three-dimensional images by viewing three-dimensional images of one- and two-feed images taken at different angles at different times as images of left and right eyes. (The time difference between watching the left eye and the right eye is 16.5msec, which is a vertical synchronization frequency period, but it is not recognized by humans.)

5 is another embodiment according to the present invention, the operation of the reference numerals and the respective circuits is the same as the circuit diagram of FIG. 3, except that the frequency inversion circuit 9 inverts the low frequency oscillation output of the low frequency oscillation circuit 5. The first liquid crystal cell 12 and the second liquid crystal cell 13 are input to the common electrode 16 which is a lower transparent electrode.

FIG. 6 is an operation waveform diagram of each part of FIG. 5, which shows that a liquid crystal cell is driven when a low frequency signal is selected.

As described above, when the synthesized video signal, in which the left and right video signals are synthesized in one frame as shown in FIG. 6A, is output from the synthesized video signal output circuit 1, the sync separation circuit 2 is described in FIG. As described above, the synthesized synchronous signal is separated from the synthesized video signal and output to the vertical synchronous signal detection circuit 3.

At this time, the vertical synchronous signal detection circuit 3 detects only the vertical synchronous signal as shown in FIG. 6 (b) from the synthesized synchronous signal and outputs it to the left and right image signal discrimination circuit 4.

In the state of operation as described above, the low frequency oscillation circuit 5 oscillates a low frequency signal as shown in FIG. 6 (e), and the high frequency oscillation circuit 6 oscillates a high frequency signal as shown in FIG. 2 outputs to the input signal of the multiplexer 7-8.

At this time, the left and right image signal discrimination circuit 4 discriminates the first and second feed signals by the vertical synchronous signal input as described above in FIG. 3, and thus the feed discrimination signals as shown in FIGS. 6 (c) and (d). Is output as the selection control signal of the first and second multiplexers 7-8.

Therefore, the first multiplexer 7 multiplexes and outputs a high frequency signal among the two input signals as shown in FIG. 6 (h) when the shield discrimination signal as shown in FIG. 6 (c) is input as a control signal. The second multiplexer 8, which inputs the inverted shield determination signal as shown in FIG. 6 d as a control signal, multiplexes the signal as shown in FIG. 6 f and outputs it as shown in FIG. 6. The outputs of the first and second multiplexers 7 and 8 are buffered in the first and second buffers 9 and 10 to the signal electrodes 15 of the first and second liquid crystal cells 12 and 13. Each is input.

In addition, the frequency inversion circuit 9 inverts the output of the low frequency oscillation circuit 5, which outputs the low frequency oscillation, as shown in FIG. 6 (d) as shown in FIG. To the common electrode 16, which is the lower transparent electrode of. Therefore, the waveforms of the sixth (h) and (g) are input between the signal electrode 15 and the common electrode 16 of the first liquid crystal cell 12, thereby driving the effective value of the first liquid crystal cell 12. As shown in FIG. 6 (J), the first liquid crystal cell 12 is turned on. The signals of FIGS. 6 (i) and (g) are input to the signal electrode 15 and the common electrode 16 of the second liquid crystal cell 13 and are interposed between the signal electrode 15 and the common electrode 16. The effective value is input and turned off as shown in FIG. 6 (k).

Therefore, when the vertical synchronization signal input from the left and right video signal discrimination circuit 4 is discriminated and output as the first feed signal, that is, the left eye video signal, the first liquid crystal cell 12 is turned off by the synthesized frequency of FIG. The left eye video signal cannot be viewed by shielding the light, and the second liquid crystal cell 13 is turned on to transmit the light by the low frequency of FIG. 6 (k) so that the left eye video signal can be viewed by the viewer's naked eye. .

In addition, if the vertical synchronization signal input from the left and right image signal discrimination circuit 4 is determined as the second feed signal, that is, the right eye image signal, the first liquid crystal cell 12 is driven by a low frequency to pass the right eye image and the second The liquid crystal cell 13 is turned off by the driving voltage as shown in FIG.

As described above, the present invention can greatly improve the response speed by driving the liquid crystal shutter by using the high frequency and low frequency synthesized frequency signals using the dielectric anisotropy of the liquid crystal, thereby allowing the user to watch an accurate stereoscopic image.

Claims (2)

A composite video signal output circuit (1) for continuously outputting a composite video signal of one frame in which a left eye video signal of a stereoscopic image is recorded in a first feed and a composite right eye video signal of a stereoscopic image is recorded in a next feed; A vertical synchronization signal by inputting a synchronous separation circuit 2 for separating and outputting a composite synchronous signal from the composite video signal output from the composite video signal output circuit 1, and a composite synchronous signal separated and output from the synchronous separation circuit 2; In the liquid crystal shutter driving circuit according to the two-frequency driving method having the vertical synchronizing signal detecting circuit 3 for detecting and outputting only, the left and right eyes are inputted by inputting the vertical synchronizing signal output from the vertical synchronizing signal detecting circuit 3. Left and right video signal discrimination circuit 4 for discriminating the first and second feed signals, which are video signals, and outputting the shield discrimination signal, and frequency oscillation for oscillating and outputting low frequency and high frequency signals, respectively. Means for inputting a low frequency oscillation signal and a high frequency oscillation signal respectively outputted from the frequency oscillation means, and selecting and outputting a low frequency or high frequency signal by a shield discrimination signal output from the left and right image signal discrimination circuit 4; The low frequency oscillation signal and the high frequency oscillation signal respectively oscillated and output from the multiplexer 7 and the frequency oscillation means are input, and the low frequency or high frequency signal is selected and output by the shield discrimination signal output from the left and right image signal discrimination circuit 4. A second multiplexer 8, a frequency inversion circuit 9 for inverting one of the outputs from the frequency oscillating means, and a first buffer for buffering the output of the first multiplexer 7 10) and the second buffer 11 for buffering the output of the second multiplexer 8, the frequency output from the frequency inversion circuit 9 and the buffer in the first buffer 10 The first liquid crystal cell 12 driven by the effective voltage between the two electrodes by inputting the frequency as the voltage of the common electrode and the signal electrode, the frequency and the second buffer outputted from the frequency inversion circuit 9 And a second liquid crystal cell (13) driven by the effective voltage between the two electrodes by inputting the frequency buffered at 11) as the voltage of the common electrode and the signal electrode. 2. A circuit according to claim 1, characterized in that the frequency inversion circuit (9) inverts the low frequency oscillation frequency output from the frequency oscillation means and simultaneously outputs it to the common electrodes of the first and second liquid crystal cells (12-13).

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