6 February 2012 Collimation of asymmetric laser diode at 450 nm using multimode fiber for speckle reduction through diffractive diffusers
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Proceedings Volume 8280, Advances in Display Technologies II; 82800F (2012) https://doi.org/10.1117/12.906879
Event: SPIE OPTO, 2012, San Francisco, California, United States
Advancements in laser diode technology have lead to the utilization of lasers in pico-projector systems. These proposed devices would need to take full advantage of the coherent source, while still providing full RGB color. Previous work has been completed analyzing 532 nm green diodes in conjunction with hadamard-matrix diffusers for reducing the disruptive speckle noise caused by coherent sources. In addition to the speckle, many small form factor laser diodes have aspheric or nonsymmetric beam shapes upon excitation. Non-circular beam shapes are difficult, if not impossible, to collimate properly. Collimation and beam symmetry is vital in order to keep the bulk of the sources power in the lower order diffractive modes that form from beam shaping optics such as diffusers and micro-lens arrays. Because of these requirements and unique diode structure, generic spherical lenses will not suffice, leading to new techniques for beam collimation. This paper looks at creating the proper beam shape through the use of multimode fiber optics. The output wave from the fiber is then passed through a diffuser. Speckle contrast measurements will be analyzed for both rotating and stationary instances of the diffuser. In addition, other techniques for creating more functional beam shapes will be evaluated in comparison with a fiber optic setup.
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Weston Thomas, Christopher Middlebrook, "Collimation of asymmetric laser diode at 450 nm using multimode fiber for speckle reduction through diffractive diffusers", Proc. SPIE 8280, Advances in Display Technologies II, 82800F (6 February 2012); doi: 10.1117/12.906879; https://doi.org/10.1117/12.906879

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