Study of Speckle Phenomenon in Laser Projection Systems
Date Issued
2010
Date
2010
Author(s)
Chang, Yan-Shuo
Abstract
In the Master Thesis, we design a laser projection system. There is a serious problem which influence projection image qualities from the illumination source “Laser”, called“Speckle”. Therefore, we study speckle reduction methods and measure it in this thesis.
In introduction, we will introduce the projection displays technology and classify projection systems. After that we describe phenomena and principle of speckle. By utilize the “Speckle Contrast (SC) ”to judge how critical the speckle pattern are. Besides, we introduce the speckle reduction methods that commonly used, that is to place a moving diffuser in the system or by vibrating screen with high frequency (let human eyes cannot felt) to suppress SC by averaging the total intensity.
After that we consider the laser propagation behavior in our system. And then we use reflective spatial light modulator (SLM) to replace the diffuser which is in the general suppressing speckle method. We design the phase diagrams by (Iterative Fourier Transform Algorithm, IFTA), and they can shape laser from a circle to a square for promoting the projection efficiency by complete illumination in the filmstrip. At the same time, we use the phase modulation technology to replace rotating diffuser. Thus we can avoid mechanical rotation and high-frequency vibration, and have faster modulation speed for suppressing speckle as well. For this reason we discuss this speckle reduction method in this.
In future research, we shall optimize these phase diagrams designed for more uniform intensity and more like a square. Besides, we can change filmstrip into display panel to discuss the difference between dynamic and static states, and discuss what difference between three color mixing laser and monochrome laser for making our system closer to the actual projector.
Subjects
Laser Projection Systems
Speckle Reduction
Speckle Phenomenon
Speckle
Type
thesis
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