Method for reducing speckle contrast in electro-holography illuminated by multimode optical fiber

Yasuo Ito; Yuji Sakamoto

doi:10.1117/12.2609112

3 March 2022 Method for reducing speckle contrast in electro-holography illuminated by multimode optical fiber

Yasuo Ito, Yuji Sakamoto

Proceedings Volume 12026, Practical Holography XXXVI: Displays, Materials, and Applications; 120260C (2022) https://doi.org/10.1117/12.2609112
Event: SPIE OPTO, 2022, San Francisco, California, United States

Abstract

Speckle noise is often observed when a rough surface is illuminated with coherent light such as a laser beam. Both laser displays and electro-holography systems often use a laser beam as a light source, so it is difficult to avoid the appearance of speckle noise. Speckle noise severely degrades the quality of the displayed image, so reducing speckle noise is an extremely important challenge. Light sources with lower temporal or spatial coherence include supercontinuum light sources and random laser light sources. Although they effectively reduce speckle noise, they are expensive and impractical. Research on reducing the speckle noise that appears at the output end of multimode optical fiber (MMF) through which a coherent laser beam is guided has shown that the noise can be time-averaged by applying mechanical vibration to the MMF. We have devised a speckle noise reduction method for electro-holography, which is an ideal 3D display technology. Speckle noise is reduced by using a voice coil actuator (speaker) to vibrate the MMF through which coherent light is guided. The driving frequency and amplitude of the actuator are electrically controlled. The light from the laser is carried by the MMF and used as the illumination light for the electro-holography. The MMF is coiled around the actuator. Experimental results showed that the speckle contrast tended to decrease as the vibration amplitude increased. This shows that the speckle contrast can be electrically controlled, which demonstrates the usefulness of this method.

Conference Presentation

Citation Download Citation

Yasuo Ito and Yuji Sakamoto "Method for reducing speckle contrast in electro-holography illuminated by multimode optical fiber", Proc. SPIE 12026, Practical Holography XXXVI: Displays, Materials, and Applications, 120260C (3 March 2022); https://doi.org/10.1117/12.2609112

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