## 2 Switchable Color Filter Barrier for Autostereoscopic Display Design
### Basic Structure of Switchable Wavelength-Selective Barriers for Multiview 3D Display  
Figure 1 illustrates schematically the cross-section of such an autostereoscopic 3D display. The Blue-Green-Red (BGR) color filter barrier _FP_ is positioned at a selected grid distance \(a\) in front of an RGB pixel matrix plane _PMP_. Such multiview displays emit directionally different image information into neighbored viewing zones of width \(P\). For this purpose, the screen was divided into image strips where the individual views are interleaved on the subpixel level. Each image strip _VP_ with a width of \(n\) subpixels, _SP_ contains information of every view in its neighboring pixel columns.  
Switchable color filters can be applied as a shift filter and an on/off filter. In the example shown in Figure 1, the color filter elements are not able to change their passband. In the on-state, their individual barrier elements transmit only one of the red, green or blue wavelength ranges, and in the off-state, they block all visible light. Optimal dimensions and the appropriate arrangement of the barrier cause the emitted light rays to converge at the viewing distance \(D\) on the image projection plane _PP_.  
For this purpose, the individual filter elements of the width \(F\) need a certain period width \(L\). They are arranged in a period that is slightly smaller than the width of the image-strip \(VP\). The views correspond to the \(n\) subpixels, which will be visible in one of the channels \(V1\) to \(VN\). Because of the time-sequential mode, the details of a number of different interlaced images corresponding to the number of switching states will be visible. This increases the resolution of views and is proportional to the number of switching stages of the alternative filter elements.  
Common layouts of autostereoscopic barrier displays use a slanted barrier and a standard 2D matrix display. In contrast, we decided to use a vertical color stripe barrier and a display matrix with vertically-alternating subpixel colors. Figure 2 shows this arrangement. The color stripe pattern of the barrier is exactly rectangular oriented to the colors on the display matrix. Subpixels with the same color are located in a row. Therefore, a local emission in one of the colors does not show any change of brightness at the movement of the observer within a lobe. A time-sequentially switchable, wavelength-selective RGB-color-filter barrier \(FP\) was placed at a defined distance \(a\) in front of the matrix display. In this arrangement, the contents of the left and right views were interleaved line-by-line separated always by one color. Figure 2 shows how the left view, drawn with the brighter colors, and the right view, drawn with the darker colors, were interlaced with always three neighboring subpixels of the same color per line. From line to line, the position in the content changes by two subpixels, because of the same offset of the colors in the barrier. As in Figure 1, on this 3D display design, the same parameter \(V=6\) can be defined as the number of subpixel per group \(VP\), but this separated for every color.  
The emitted light converges at viewing distance \(D\) in adjacently arranged stereo rhombs of uniform color mixing of red, green and blue. Figure 2 demonstrates the time-sequential operating mode, where alternative openings are created and the subpixel allocation is simultaneously shifted by \(V/2\) subpixels. Opposite the arrangement in Figure 1, the color filter stripes are equally distributed anytime. The shift does ensure that the image contents of the adjacent stereo zones converge at the same position [17; 18].  
Figure 1: Principle of time-sequential operation of a wavelength-selective multiview 3D display at the state at \(t_{1}\) and \(t_{2}\) with resolution enhancement in the same positioned viewing zones \(V1\) to \(VN\).