Measurement instruments

V

UV

V ITO PI Monomer

Polymer layer

Fig. 4-3 Fabrication process of polymer layer^[22].

4.2 Measurement instruments

Conoscope was used to measure the luminance of LCDs. The Conoscope (Fig.

4-4) can be used for evaluation of the characteristics of LCDs, including luminance vs.

viewing direction, chromaticity vs. viewing direction, response time, electro-optical characterization, etc. The basic principle of Conoscope is depicted in Fig. 4-5. A transparent sample that is illuminated from the back side via a cone of light beams C is located in the front of focal plane of the lens L1. The light through the sample is collected simultaneously over a large solid angle by the lens L1 and generate a pattern IF1 in the rear focal plane F’1 of the lens L1. In the pattern IF1, the intensity of each area element corresponds to the intensity of one elementary parallel beam with a specific direction of light propagation. The directional intensity distribution of the cone of elementary parallel light beams C is transformed into a two-dimensional distribution

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of light intensity and color with each location in the pattern IF1 corresponding to exactly one direction of light propagation (θ, φ).

A second optical system L2 optionally projects the figure IF1 on a two dimensional detector array such as a Charge-coupled Device (CCD) for evaluation of the spatial intensity distribution, which corresponds to the directional intensity distribution of the light emerging from the measuring spot on the sample.

Fig. 4-4 Conoscope.

Fig. 4-5 The principle diagram of Conoscope.

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Chapter 5

Measurement Results and Discussion

5.1 Introduction

The objective of the measurement is to investigate the brightness of the 3D displays with different pixel layouts. We demonstrated the 2.83” 6-view parallax barrier 3D display. According to the simulated results presented in Chapter 3, Table 5-1 shows the specifications of the parallax barrier and 2.83” LCDs with conventional and proposed pixel layouts. The proposed pixel layout is multi-domain vertically alignment mode with slanted storage capacitor. The measurement results will be shown in this chapter.

5.2 Measurement results and discussion

The measurement results can be categorized into two parts: brightness and crosstalk. The conventional and proposed pixel images were observed by optical microscope, as shown in Fig. 5-1.

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Table 5-1 Specifications of the parallax barrier and 2.83” LCDs.

Conventional 3D Display Proposed 3D Display Parallax Barrier Slit (μm)

(by NTHU)

Spatial Freq.=180μm/cycle

26 19

Pixel Layout (30μm X 90μm)

Resolution 640 X 480 640 X 480

Thickness of Glass Substrate

(μm) 300 500

Thickness of Polarizer (μm) 180 180

Conventional MVA-b Proposed Pixel with Slanted Cst

Pixel Images (Multi-domain VA)

Fig. 5-1 The fabricated pixel images were observed by an optical microscope.

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5.2.1 Brightness

The brightness increase ratio of the 3D display with pixel which has slanted storage capacitor is shown in Table 5-2. The brightness of 2.83” 3D display with the slanted storage capacitor improves by 63% compared to that of the conventional 3D display. For the aperture ratio of the parallax barrier, the increase ratio by measurement is higher than that of the design due to fabrication variation. The parallax barrier was fabricated by printing process with 20000dpi. The brightness of the proposed LCD is increased due to increasing the aperture ratio. These measurement results imply that the brightness of 3D display with proposed pixel design is increased compared to conventional 3D display.

Table 5-2 Brightness increase ratio of the proposed pixel layout compared to 3D display with conventional MVA-b pixel layout.

Simulation Measurement

A.R. of Barrier (%) 136 152

Brightness of LCD (%) 113 107

Combined Brightness (%) 160 163

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5.2.2 Crosstalk

The crosstalk of each view was measured by inputting the patterns (Fig. 5-2). For instance, Fig. 5-3 shows how to measure the crosstalk of viewing zone 5 and 3 resulted from the light leakage from pixel 4. The input pattern, BBWBBB, represents that white image can be observed within viewing zone 4 and the rest of viewing zones show black image in the ideal case (0 % crosstalk). After inputting these six patterns (Fig. 5-2) respectively, the crosstalk of 3D displays based on conventional and proposed pixel layouts can be measured by Conoscope, as shown in Table 5-3. The results demonstrate that 3D display with proposed pixel layout has lower crosstalk even if parallax barrier slit size is wider (26μm). Therefore, the image quality of each viewing zone can be improved due to lower crosstalk.

(a)WBBBBB (b)BWBBBB (c)BBWBBB (d)BBBWBB (e)BBBBWB (f)BBBBBW Fig. 5-2 Test patterns used to measure the crosstalk of each viewing zone.

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Light leakage from pixel 4

Fig. 5-3 The illustration of measurement of inputting the test pattern (BBWBBB).

Table 5-3 Crosstalk was measured by Conoscope.

Conventional Slanted Cst

Barrier Slit Size (μm) 19 26

Crosstalk (%) ~51 ~37

5.3 Summary

For the brightness and crosstalk, the comparisons of conventional MVA-b and proposed pixel with slanted storage capacitor are summarized in Table 5-4. The brightness of 2.83” 3D display with the slanted storage capacitor improves by 63%

compared to that of the conventional 3D display. In addition, 3D display with proposed pixel layout has lower crosstalk even if parallax barrier slit size is wider (26μm). The results indicate that the 3D display with proposed pixel yields not only higher brightness, but lower crosstalk.

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Table 5-4 Comparisons of 3D displays with conventional and proposed pixel layouts.

Conventional MVA-b Proposed Pixel with Slanted Cst Brightness Increase

Ratio (%) 100 ~ 163

Crosstalk (%) ~37 ~19

Images of Viewing Zone 3

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Chapter 6

Conclusions and Future Work

6.1 Conclusions

The pixel layout for multi-view 3D display has been presented and demonstrated in this thesis. There are three parameters: transmittance of LC cells, the aperture ratio of pixels, and the aperture ratio of the parallax barrier, affecting brightness of 3D displays. We proposed Normally White Single Domain VA with slanted storage capacitor to increase the brightness and suppress the crosstalk. The simulated results indicate that the brightness is increased by a factor of 2 compared to that of a conventional 3D display with parallax barrier. The unbalanced brightness issue can be minimized by utilizing Normally White Single Domain VA mode LC cell.

The pixel layout we fabricated is multi-domain vertically alignment mode with slanted storage capacitor. The simulated results show the brightness of the parallax barrier 3D display with slanted storage capacitor pixel layout is increased by a factor of 1.6. The measurement results (brightness increase ratio~1.6) are close to simulation result. In addition, the 3D display with proposed pixel layout has lower crosstalk even if parallax barrier slit size is wider (26μm). In conclusion, the 3D display with proposed pixel yields not only higher brightness but lower crosstalk.

The proposed pixel layout can also be applied for large size of 3D display to enhance the brightness due to the fact that the position and shape of the storage capacitor were optimized for the shape of barrier, as shown in Fig. 3-20. The capacitor was hided behind the barrier to increase the aperture ratio within the barrier slit.

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6.2 Future work

Nowadays, the major issues of mutli-view 3D displays are lower brightness and lower resolution of each view. In this thesis, we proposed a pixel layout which is applied for 3D displays to obtain higher brightness with lower crosstalk. However, the aperture ratio of the pixel will decrease as increasing the resolution. After combining with parallax barrier, the brightness is degraded significantly.

In this thesis, although the brightness of a 3D display with the proposed pixel layout is increased, much light is still blocked by opaque components, such as data lines. The pixels consist of straight data lines, while the parallax barrier is slanted.

Fig. 6-1 shows the concept of the slanted pixel which has higher aperture ratio of effective area due to slanted data lines. Slanted data lines have the same angle as slanted parallax barrier, therefore the light from the pixels become more. Moreover, the crosstalk issue can be degraded effectively due to the light form neighboring pixel become less. As increasing the resolution of each view, slanted pixel has higher brightness than conventional pixel due to the fact that shape of pixel is optimized for slant parallax barrier.

Fig. 6-1 Slanted pixel layout.

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