A novel double display screen was developed by the polarizedlight directivity control method. 一種新的雙顯示屏開發是采用的偏振光的光的指向性控制方法。Because the separation of theimage doesn't depend on pixel pitch, it is possible to adopt it forhigh resolution panel. In addition, the switch to 2D and 3Ddisplay mode is also possible.
In recent years, installing the display in the car such as carnavigations has accelerated because informationization of the caradvanced.
As for the display for the car, the development ofdouble display screen is hoped. Double display screen is a displaywhere different images can be observed in the driver's seat and thepassenger's seat. Under these circumstances, we developed thenew display that could be used by switching as double displayscreen, no-glasses 3D display and normal 2D display bycontrolling the polarized light directivity.2. Problem of parallax barrierIn order to realize the double display screen that is to separatetwo images displayed on one panel at the same time and toobserve them from different positions, the application of the no-glasses 3D display technology such as parallax barrierandlenticular lensis proposed. But in case of double display screen,the area where one separated image can be observed is about tentimes as necessary as a usual no-glasses 3D display. For the car, itis necessary to make those who drive and man in the passenger'sseat can observe a different screen in the large range. But whenLCD is applied as a display element, there is the problem thatoriginates in the structure of LCD (thickness of the glass panel).Figure 1 shows the cross section when the parallax barrier isadopted as a method of double display screen. For example, figure1 indicates the design value of each parameter to adjust the rangeon one screen that can be observed to about 590mm whenobserving it from a position left from the screen by 600mm. TheLCD is high resolution SVGA of 8 inches. The following
To achieve range E in 590mm, D should be assumed to be 0.1mm.以下為了實現E在590毫米的成就范圍，D應被假定為0.1毫米..Concretely, it is possible to achieve it by first thinning the glasssubstrate of the liquid crystal panel up to 0.1mm, arranging thebarrier directly on the glass substrate, and arranging the toppolarizer of the liquid crystal panel in addition outside in thebarrier. Therefore, composing the barrier of the liquid crystalpanel that can be turned on and off becomes impossible anddisplaying the screen of usual 2D without the image deteriorationbecomes impossible. As equation 2 shows, when pixel pitch B ofthe liquid crystal panel becomes smaller, a further making of theglass of LCD to the thin type (Reduce D) is needed to realize awide observational area enough. Therefore, in the high resolutionpanel the limit of the thickness of the liquid crystal panel glassbecomes the limit of the observational area of the image of doubledisplay screen.3. Polarized light directivity controlmethod3.1 StructureFigure 2 shows the construction of our novel double displayscreen using our original polarized light directivity controlmethod. Parts added to a usual liquid crystal panel are thefollowing four.1, Polarizer 1: The polarized light axis of light from the backlightis limited.2, Polarized light control LC cell: The polarized light axis of lightthat passes each area is controlled.從背面的燈光限制的情況來看，偏光控制液晶單元的偏振光軸的光，可以通過控制每個區域的光來進行調節。
3, Lenticular lens: The direction of light that the polarized lightaxis of each area is controlled is limited.4, Patterned retardation film: The polarized light axis of incidencelight into LCD is converted corresponding in each line of LCD.The separation of two images displayed in the LCD is achievedwith the above-mentioned composition material. The principleof the image separation is described as follows.3.2 Principle3.2.1 Double screen modeFigure3 shows the cross section of our new technology that is thepolarized light directivity control method and it shows the doublescreen mode. Figure 4 shows each condition of polarized lightaxis at each state. The light through the polarizer 1 having thetransmittance axis (θ ) is converted into linearly polarized light(Fig4:4-A). Then the polarized light enters the polarized lightcontrol LC cell Homogeneous aligned LC cell withθ +45°rubbing direction can be switching individually bypatterned vertical stripes of ITO electrode perpendicular to thelenticular lens. Two areas of LC panel is design to correspondwith one lens in double screen mode. Also the retardation of theLC cell is designed as λ /2 plate when applied voltage is zero(off state) and zero when applied voltage is 5V (on state). Thelight through off state of LC cell is rotated 90°against incidentlight and the light through on state of LC cell is transmitteddirectly. Therefore direction of linearly polarized light separate2 state θ +90°(Fig4:4-B) and θ (Fig4:4-C). And then Lensrefracts each polarized light to the right or left side toward eachside viewer individually. The light through off state of the LC cellis directed toward right side viewer and the light through on stateof the LC cell is directed toward left side viewer. Each directional light is transmitted through the retardation film. 每個定向光，都可以通過相位差電影來傳輸。The retardationfilm (λ /2 plate) is patterned horizontal stripe that widthcorresponds with pixel pitch. The film direction of odd line is θ -45° and even line is θ +90°(Fig4:4-D). In the directional lighttoward right side viewer, the light through odd line of theretardation film is rotated 90°and the light through even line istransmitted directly. Therefore the directional light through odd /even lines of the retardation film separates 2 state, θ andθ +90°(Fig4:4-F). In the left side viewer, the directional lightthrough the retardation film separates 2 states, i.e. θ +90°andθ (Fig4:4-E). Due to the transmittance axis of bottom polarizer ofmain display is θ +90°, the directional light with direction θ isabsorbed by bottom polarizer. But the directional light withPatternedLeft side viewerEvenOddRight side viewerθθθ +90θθθ +45control LC CellPolarizer 1EvenOddθ +90θ -45BottomPolarizer(4-A)(4-B)(4-D)θ(4-E) (4-F)PolarizedLightλ /2OffOnLinearly(4-C)θ +90θ +90θ +90RetardationFilm (λ /2)Polarized lightFigure 4 Polarized light axisEvenOddθθθ +90θ +90Figure 3 Polarized light directivity control method θ +90 is transmitted. So the directional light is transmitted onlyeven line for right side viewer and only odd line for left sideviewer. The main LC panel displays two different imagescorresponding with odd and even line. So we can display twodifferent images toward right and left viewer individually.3.2.2 3D modeFigure 5 shows the state of the display in the 3D display modein an experimental double display screen. The ITO electrode ofthe polarized light control LC cell corresponding to eachlenticular lens is divided into four stripes. The polarized light axisof each stripe is alternately switched in a 3D mode though thepolarized light axis of each of the continual two stripes isswitched in double screen mode. As a result, the light of eachpolarized light axis reaches the viewer side at a short cycle. Andtwo viewers see different light in the right eye and the left eye. 兩個觀眾使用右眼和左眼，可以看到不同的光。