JP3829479B2 - Display device and driving method thereof - Google Patents

Description

【００３４】
更に、液晶スピードには、駆動電圧に対する依存性が有り、特に、中間調の領域で大きく応答速度が遅くなる。例えば、白黒の変化が１０〜２０ｍｓ程度であるのに対し、白から中間調の灰色に対する速度は２０〜５０ｍｓ程度と大幅に遅くなる。
【００３５】
そこで、図１に示す液晶プロジェクタ装置では、動作回路系１の映像信号生成回路１１とＬＣＤドライバ１３との間に信号処理回路１００を設けて、液晶スピードの改善、特に、中間領域でのスピードの改善を達成する。
【００３６】
図２に、信号処理回路１００の構成例を示すが、映像信号生成回路１１から入力される映像信号は、フィールド遅延回路１０１を通過する経路と直接の経路で夫々演算器１０２に入力され、この演算器１０２で両者の差が演算される。演算器１０２での演算結果は、アンプ１０３でゲインコントロールされた後、加算器１０４で元の信号に加えられ、ＬＣＤドライバ１３に送られる。この処理をディジタル信号処理で行う場合、フィールド遅延回路１０１は、フィールドメモリにより構成することができる。
【００３７】
図３に、この信号処理回路１００での信号変化の例を示す。この図３は、解像度が高く、同一画素でフィールド毎に信号が変化する場合の波形動作を示している。
【００３８】
フィールド毎に信号レベルが変わる入力信号ａ、ｅに対し、１フィールド前の入力信号ｂ、ｆとの差ｃ、ｇを求め、その結果を元の信号ａ、ｅに加えて、出力信号ｄ、ｈを得る。
【００３９】
このように、信号処理回路１００において、入力信号変化ａ、ｅに対し出力信号ｄ、ｈにおけるフィールド毎の信号レベル差を増大させ、液晶の応答スピードの遅い中間輝度領域での輝度変化に相当する小さな電圧変化の信号の場合、より大きな電圧変化に変換し、これによって、応答スピードの速い白黒変化（輝度変化の大きな変化）の領域へ近づけ、液晶の応答スピードを大幅に改善することができ、ウォブリングの効果を高めることができる。
【００４０】
【発明の効果】
本発明においては、離散的な固定画素配列を有する表示素子から出射した光ビームにフィールド周期でウォブリングを生ぜしめて表示する表示装置において、表示素子に印加すべき映像信号のフィールド間の差を強調して表示素子に印加するようにしているので、例えば、液晶等の表示素子の応答速度を高めることができ、ウォブリング時にフィールド毎に信号レベルが変化する画柄のコントラスト比を改善することができる。この結果、解像度の高い信号表示の視覚的分離感を高めることができ、解像度が向上する。
【図面の簡単な説明】
【図１】本発明の一実施形態による液晶プロジェクタ装置の構成を示すブロック図である。
【図２】本発明による信号処理回路の一例を示すブロック回路図である。
【図３】図２の信号処理回路における信号変化を示す波形図である。
【図４】フィールド間での輝度変化を示すグラフである。
【図５】ウォブリングの原理を示す模式図である。
【符号の説明】
１…動作回路系、２…光源系、３…投影系、１１…映像信号生成回路、１２…同期信号生成回路、１３…ＬＣＤドライバ、１４…タイミング生成回路、１５…ＦＬＣドライバ、２１ａ、２１ｂ…ダイクロイックミラー、２２ａ〜２２ｃ…ミラー、２３Ｒ、２３Ｇ、２３Ｂ…液晶パネル、２４…クロスプリズム、３０…ウォブリング素子、３１…ＦＬＣ（強誘電性液晶）、３２…水晶板、３３…１／４波長板、３４…投影レンズ、３５…スクリーン、１００…信号処理回路、１０１…フィールド遅延回路、１０２…演算器、１０３…アンプ、１０４…加算器[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a display device including a display element having a discrete fixed pixel arrangement such as liquid crystal, plasma, EL (electroluminescence), and the like, and a driving method thereof.
[0002]
[Prior art]
The electronic display device can be said to be an electronic device that transmits various information from various electronic devices to a human through vision, or an electronic tool for humans to exchange information through the electronic device and visual. This electronic display device is widely used in various application fields regardless of industrial fields and consumer fields, and its role is extremely important.
[0003]
In recent years, liquid crystal displays, plasma displays, EL displays, and the like have been actively researched and developed as electronic display devices that replace CRTs. In addition, for example, attempts have been made to realize a 40 to 60 inch flat plate type large display such as a liquid crystal projector or a plasma display by an HD (High Definition) system.
[0004]
In particular, an interlace (interlaced scanning) method is adopted as a standard for transmitting the HD method as a digital signal in order to cope with a conventional high-vision device.
[0005]
However, a display element having a discrete fixed pixel arrangement such as liquid crystal, plasma, EL, or the like cannot simply support interlaced scanning even when performing interlaced display such as NTSC system or HD (particularly, high-definition) system. Has the problem. For this reason, although a sequential circuit corresponding to interlace is newly provided in the display element itself, or means such as converting and displaying a video signal into a non-interlaced form using a memory is taken, it is expensive. There is a problem that a complicated system must be constructed.
[0006]
In this case, the number of pixels of the display element, in particular, the number of vertical pixels is required by the number of effective scanning lines of the signal. If the number of pixels of the display element does not reach the number of effective scanning lines, the odd field and the even number The field is written in the same pixel or the video signal is thinned out appropriately. That is, the vertical resolution is lowered and the image quality is inferior to that of the original signal.
[0007]
On the other hand, a display pixel shifting technique (wobbling technique) is known as means for improving the vertical resolution using the same pixel in a display device having a display element composed of discrete fixed pixels. (For example, see JP-A-7-64046, JP-A-7-104278, etc.).
[0008]
In this wobbling technique, the optical axis by the first field scanning and the optical axis by the second field scanning of the video signal are switched by the phase modulation optical element and the birefringent medium, and one field image is switched to the other field image. Is a method of displaying at a different position.
[0009]
By using such a wobbling technique, even in a display device having a display element composed of discrete fixed pixels, interlaced display can be performed with a relatively simple configuration, and vertical resolution is not reduced.
[0010]
[Problems to be solved by the invention]
For example, in a liquid crystal projection apparatus to which such a wobbling technique is applied, when attention is paid to individual pixels of the liquid crystal panel, it is necessary for the same pixel to display the first field image light and the second field image light at different positions. Therefore, in the case of a high-resolution signal having a large change in the vertical direction, the luminance level of the signal of the same pixel greatly changes for each field.
[0011]
However, in an actual liquid crystal panel, the response speed is limited. For example, the response speed of a normal TN (twisted nematic) liquid crystal is about 10 to 30 ms. For this reason, the speed of the liquid crystal may not be able to follow the change of the signal, and the image quality is deteriorated as the contrast is lowered. In particular, the reproducibility of a high-resolution signal component that should be increased by the wobbling means is deteriorated, and the wobbling performance is reduced.
[0012]
Accordingly, an object of the present invention is to provide a display device and a driving method thereof capable of effectively applying a wobbling technique to a display device including a display element having a discrete fixed pixel arrangement without causing a decrease in contrast. Is to provide.
[0013]
[Means for Solving the Problems]
The display device of the present invention that solves the above-described problems includes a display element having a discrete fixed pixel arrangement, a wobbling element that causes a light beam emitted from the display element to wobble in a field period, and an application to the display element. Video signal generating means for generating a video signal to be performed, and provided between the video signal generating means and the display element, emphasizing a difference between fields of the video signal supplied from the video signal generating means, and Signal processing means for applying to the display element.
[0014]
In the present invention, it is preferable that the signal processing means includes field delay means for delaying the video signal by one field, and a signal delayed by one field through the field delay means does not pass through the field delay means. After subtracting from the signal and amplifying the result as necessary, the result is added to the signal not passing through the field delay means and output to the display element.
[0015]
The field delay means can be constituted by a field memory, for example.
[0016]
The display device of the present invention may further include a screen for projecting the light beam generated by the wobbling element in the field period.
[0017]
The display device driving method of the present invention is a display device driving method in which a light beam emitted from a display element having a discrete fixed pixel array is displayed by generating wobbling in a field period in a field period. The difference between the fields of the power video signal is emphasized and applied to the display element.
[0018]
At this time, it is preferable that a signal obtained by delaying the video signal by one field is subtracted from the video signal that is not delayed, and the result is amplified as necessary and added to the video signal that is not delayed to display the display. Applied to the element.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described according to preferred embodiments.
[0020]
FIG. 1 shows a configuration example of a liquid crystal projector device to which the present invention is applied.
[0021]
This example is a three-plate liquid crystal projector apparatus, which mainly comprises an operating circuit system 1, a light source system 2, and a projection system 3.
[0022]
In the light source system 2, the light emitted from the lamp 20 as a light source is sequentially separated into three colors of R (red), G (green), and B (blue) by two dichroic mirrors (DM) 21a and 21b. The respective lights are guided by the mirrors 22a, 22b and 22c, and enter the liquid crystal panels 23R, 23G and 23B corresponding to the respective colors. Each of the liquid crystal panels 23R, 23G, and 23B is composed of, for example, a polysilicon TFT (Thin Film Transistor) liquid crystal panel (hereinafter sometimes referred to as “p-Si TFT liquid crystal panel”). The polarizing plates are arranged in crossed Nicols. Each of the liquid crystal panels 23R, 23G, and 23B performs gradation display according to the video signal transmitted from the operation circuit system 1. Light emitted from the liquid crystal panels 23R, 23G, and 23B is linearly polarized by the polarizing plate described above. At this time, the liquid crystal panels 23R, 23G, and 23B and the above-described polarizing plates are arranged so that the directions of the linearly polarized light of the three color rays are aligned. The lights emitted from the respective liquid crystal panels 23R, 23G, and 23B are combined by the cross prism 24 and sent to the projection system 3.
[0023]
The projection system 3 has a wobbling element 30. In the wobbling element 30, for example, an FLC (ferroelectric liquid crystal) 31 is used as a phase modulation optical element, and a quartz plate 32 is used as a birefringent medium. The light from the light source system 2 described above first enters the FLC 31 of the wobbling element 30 in the projection system 3. The FLC 31 functions to switch the polarization plane of the incident light between parallel and vertical in synchronization with the interlace signal in the video signal. Since the next crystal plate 32 has the abnormal optical axis direction parallel to the polarization plane of the outgoing light emitted from the FLC 31, the pixel shift is performed vertically according to the switch state of the FLC 31. Is called. At this time, the outgoing light from the wobbling element 30 remains as vertical polarization and horizontal polarization switched for each field by the FLC 31 which is a phase modulation optical element. The image shifted in pixels for each field passes through the projection lens 34 and is projected on the screen 35. In general, since the screen 35 has a luminance gain difference due to polarization, a luminance difference is generated for each field, and this is detected as flicker. For this reason, the linearly polarized light is eliminated by placing the quarter wavelength plate 33 after the wobbling element 30, and the gain difference due to the polarization in the screen 35 or the like is eliminated, thereby preventing flicker.
[0024]
Next, in the operation circuit system 1, the video signal output from the video signal generation circuit 11 is sent to the LCD driver 13 after passing through the signal processing circuit 100 according to the present invention. The LCD driver 13 drives the liquid crystal panels 23R, 23G, and 23B of the light source system 2 based on the sampling timing generated by the timing generation circuit 14 according to the synchronization signal generated by the synchronization signal generation circuit 12. The FLC driver 15 drives the FLC 31 of the wobbling element 30 in the projection system 3 based on the field information sent from the timing generation circuit 14. The operation of the signal processing circuit 100 according to the present invention will be described later.
[0025]
With the above configuration, an interlace structure is faithfully projected on the screen 35 by applying a video signal including an interlace signal to each of the liquid crystal panels 23R, 23G, and 23B as it is.
[0026]
Next, the principle of wobbling will be briefly described with reference to FIG.
[0027]
The light from the light source 20 is displayed in gradation by the liquid crystal panel 23, and the light emitted from the liquid crystal panel 23 is linearly polarized light. The direction of this linearly polarized light is determined by the crossed Nicol direction of a polarizing plate (not shown) that is pasted or placed on the front and back of the liquid crystal panel 23. In the figure, an example is shown in which light is polarized in the vertical direction (Y direction).
[0028]
As shown in FIG. 5A, in the odd field, the light emitted from the liquid crystal panel 23 enters the quartz plate 32 as it is without being switched by the FLC 31 of the wobbling element 30. At this time, the polarization plane of the incident light includes the extraordinary optical axis of the crystal, and therefore, the light is refracted in the direction in which the extraordinary optical axis of the quartz plate 32 is tilted and the image is shifted.
[0029]
On the other hand, as shown in FIG. 5B, in the even field, the light emitted from the liquid crystal panel 23 has its plane of polarization rotated by 90 ° by the switching of the FLC 31 of the wobbling element 30, and the direction of linearly polarized light is The horizontal direction (X direction). The plane of polarization of this light does not include the anomalous optical axis of the crystal of the crystal plate 32, and is thus emitted as it is without being refracted by the crystal plate 32. Thus, the image is not shifted in the even field.
[0030]
Next, problems in the case where the signal processing circuit 100 according to the present invention is not provided in the liquid crystal projector apparatus shown in FIG. 1 will be described.
[0031]
FIG. 4 schematically shows how the luminance changes depending on the liquid crystal speed when a signal applied to a certain pixel of the liquid crystal panel repeats black and white for each field.
[0032]
As can be seen from this figure, since it takes time to follow the luminance of the liquid crystal, the substantial luminance decreases even during the white period, and conversely increases during the black period. This influence is a reduction in contrast ratio, and the reduction is inevitable even if the switching timing of the FLC 31 of the wobbling element 30 is selected so that the contrast becomes maximum. This phenomenon depends on the response speed of the liquid crystal, and the contrast ratio is expressed by the following equation.
[0033]
[Expression 1]

[0034]
Furthermore, the liquid crystal speed has a dependency on the driving voltage, and the response speed is particularly slow in the halftone region. For example, while the change of black and white is about 10 to 20 ms, the speed from white to halftone gray is about 20 to 50 ms, which is significantly slow.
[0035]
Therefore, in the liquid crystal projector device shown in FIG. 1, the signal processing circuit 100 is provided between the video signal generation circuit 11 of the operation circuit system 1 and the LCD driver 13 to improve the liquid crystal speed, particularly in the middle region. Achieve improvement.
[0036]
FIG. 2 shows a configuration example of the signal processing circuit 100. The video signal input from the video signal generation circuit 11 is input to the computing unit 102 through a path passing through the field delay circuit 101 and a direct path. The difference between the two is calculated by the calculator 102. The calculation result in the calculator 102 is gain-controlled by the amplifier 103, added to the original signal by the adder 104, and sent to the LCD driver 13. When this processing is performed by digital signal processing, the field delay circuit 101 can be configured by a field memory.
[0037]
FIG. 3 shows an example of signal change in the signal processing circuit 100. FIG. 3 shows a waveform operation when the resolution is high and the signal changes for each field at the same pixel.
[0038]
For input signals a and e whose signal levels change for each field, differences c and g from input signals b and f one field before are obtained, and the result is added to the original signals a and e to obtain output signals d, Get h.
[0039]
Thus, in the signal processing circuit 100, the signal level difference for each field in the output signals d and h is increased with respect to the input signal changes a and e, which corresponds to the luminance change in the intermediate luminance region where the response speed of the liquid crystal is slow. In the case of a signal with a small voltage change, it is converted into a larger voltage change, which allows it to approach the region of black-and-white change (a large change in brightness) with a quick response speed, and the response speed of the liquid crystal can be greatly improved. The effect of wobbling can be enhanced.
[0040]
【The invention's effect】
According to the present invention, in a display device that displays a light beam emitted from a display element having a discrete fixed pixel array by wobbling in a field period, the difference between fields of video signals to be applied to the display element is emphasized. Therefore, for example, the response speed of a display element such as a liquid crystal can be increased, and the contrast ratio of a pattern whose signal level changes for each field during wobbling can be improved. As a result, it is possible to enhance the visual separation feeling of the high resolution signal display and improve the resolution.
[Brief description of the drawings]
FIG. 1 is a block diagram showing the configuration of a liquid crystal projector according to an embodiment of the present invention.
FIG. 2 is a block circuit diagram showing an example of a signal processing circuit according to the present invention.
FIG. 3 is a waveform diagram showing signal changes in the signal processing circuit of FIG. 2;
FIG. 4 is a graph showing a luminance change between fields.
FIG. 5 is a schematic diagram showing the principle of wobbling.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Operation circuit system, 2 ... Light source system, 3 ... Projection system, 11 ... Video signal generation circuit, 12 ... Synchronization signal generation circuit, 13 ... LCD driver, 14 ... Timing generation circuit, 15 ... FLC driver, 21a, 21b ... Dichroic mirrors, 22a to 22c ... mirrors, 23R, 23G, 23B ... liquid crystal panels, 24 ... cross prisms, 30 ... wobbling elements, 31 ... FLC (ferroelectric liquid crystal), 32 ... quartz plates, 33 ... 1/4 wavelength plates 34 ... Projection lens, 35 ... Screen, 100 ... Signal processing circuit, 101 ... Field delay circuit, 102 ... Calculator, 103 ... Amplifier, 104 ... Adder

Claims (6)

A display element having a discrete fixed pixel arrangement;
A wobbling element that causes wobbling in the field period to the light beam emitted from the display element;
Video signal generating means for generating a video signal to be applied to the display element;
A signal processing unit that is provided between the video signal generation unit and the display element and emphasizes a difference between fields of the video signal supplied from the video signal generation unit, and is applied to the display element;
A display device comprising: The signal processing means includes field delay means for delaying the video signal by one field, and subtracts a signal delayed by one field through the field delay means from a signal not passing through the field delay means, and the result The display device according to claim 1, wherein after being amplified as necessary, the signal is added to a signal not passing through the field delay means and output to the display element. The display device according to claim 2, wherein the field delay means comprises a field memory. The display device according to claim 1, further comprising a screen that projects the light beam generated by the wobbling element in a field period. In a driving method of a display device for displaying a light beam emitted from a display element having a discrete fixed pixel array by generating wobbling in a field period,
The difference between the fields of the video signal to be applied to the display element is emphasized and applied to the display element,
A driving method of a display device. A signal obtained by delaying the video signal by one field is subtracted from the non-delayed video signal, and the result is amplified as necessary, added to the non-delayed video signal, and applied to the display element. Item 6. A display device driving method according to Item 5.

Images