Using varying length of fiber bundle to reduce the laser speckle of endoscope illumination source
| Autor: | Po-Wei Yi, 易柏維 |
|---|---|
| Rok vydání: | 2019 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 107 In order to not only reduce the section of endoscope but also maintain sufficient brightness. We utilize a high coherent semiconductor laser as the light source. But it also accompanies speckle generation. When the high coherent light source transmitts to the screen or the object, the surface of the object is not smooth, resulting in the scattered light to interfere, which affects the image quality. Therefore, reducing the speckle to enhance image clarity is the goal of the experiment. We use customized fiber, buzzer, and laser speckle reducer to lower speckle contrast. The customized fiber is made by fiber bundle. Each fiber with different lengths. The difference of length is a multiple of the coherence length of the laser light. These three methods the change the mode of the light transmission, thereby reducing the coherent of the laser source. Due to reduce the coherent of the light source, reducing the generation of the speckle. And analysis the image obtained by each method by signal-to-noise ratio and flatness. The result show that the customized fiber obtains the best speckle removal and the most uniform image. Compared to the high speckle contrast image from using single fiber. This method can observe the object clearly. But when we introduce the two fibers into the otoscope, it’s almost without speckle pattern in the image. Base on this reason, we speculate that the special fiber bundle can reduce the spot contrast should be the difference in spatial distribution instead of temporal delay. As the otoscope is the fiber bundle with same length of each fiber. Fibers split one source into multiple light source. Each light source may generate speckle pattern. According to the superposition of all speckle, the spot contrast is lower. Customized fiber, without noise, and more convenient than laser speckle reducer. It can be applied to ultra-slim endoscope developed by us. The application not only provides sufficient brightness but also reduces the problem of speckle. It has the potential to develop into a commodity by improving the stability. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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