臺灣博碩士論文加值系統

我們提出了一種用於雷射微型投影機的光斑減少系統。採用全像擴散器和液態可調透鏡（FET透鏡）來減少光斑對比度。本研究首先關注通過考慮具有不同發散角的全像擴散器來減少光斑。通過結合FET透鏡可以進一步減小光斑對比度值。我們比較了使用不同發散角的全像擴散器其光斑減少能力，以提供不同的角度多樣性。進行了三個實驗以探索光斑減少。在實驗1中，我們使用全像擴散器和FET透鏡。光斑對比度值可以降低到0.08353。在實驗2中，當達到功耗和光斑減少之間的平衡時，光斑對比度值可以減小到0.06403。在實驗3中，我們調整不同的波形以獲得較低的光斑對比度值。最終光斑對比度值在400Hz時為0.048，低於0.05，因此足夠低以使人眼無法檢測到光斑現象。

We propose a speckle reduction system for use in a laser pico-projector. Holographic diffusers and fast electrically tunable lens (FET lens) are adopted for speckle contrast reduction. This research first focuses on speckle reduction by consideration of holographic diffusers with different divergence angles. The speckle contrast value can be further reduced by the incorporation of an FET lens. We compare the speckle reduction ability obtained using different divergence angles for the holographic diffuser to provide different angular diversities. Three experiments are carried out to explore speckle reduction. In experiment 1, we use a holographic diffuser and the FET lens. The speckle contrast value can be reduced to 0.08353. In experiment 2, the speckle contrast value can be reduced to 0.06403 when the balance between the power consumption and speckle reduction are reached. In experiment 3, we adjust different waveforms to get a lower speckle contrast value. The finale speckle contrast value is 0.048 at 400Hz which is lower than 0.05 and hence low enough to render the speckle phenomenon undetectable to the human eye.

Chapter 1 Introduction 1

1-1 Preface 1

1-2 Motivation 2

1-3 Architecture of this paper 4

Chapter 2 Basic theory of optics 6

2-1 Speckle phenomenon 6

2-1.1 Discovery of speckle 6

2-1.2 Interpretation of speckle 7

2-2 Parameters of speckle measurement 8

2-3 Speckle measurement method 9

2-4 Relay Lens System 11

Chapter 3 Introduction of experimental instrument 13

3-1 Holographic diffusers 13

3-2 Fast electrically tunable lens 14

3-3 Light pipe 16

Chapter 4 Bidirectional Scattering Distribution Function (BSDF) 18

Chapter 5 Speckle reduction for the laser pico-projector
20

5-1 Layout of laser pico-projector 20

5-2 Experiment setup 22

Chapter 6 Speckle reduction by using different holographic diffusers and driving mode of FET lens 24

6-1 Experiment 1: Speckle reduction by adjusting current frequency of FET lens and using different holographic diffusers of divergence angle. 24

6-2 Experiment 2: The effect between the optical power range of FET lens and the speckle contrast. 28

6-3 Experiment 3: Driving the FET lens with different input waveforms. 32

Chapter 7 Conclusion 35

Chapter 8 Future work 37

Reference 38

Publication list 41

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