Diffractive diffusers (phase gratings) are routinely used for homogenizing and beam shaping for laser beam applications. Another use for diffractive diffusers is in the reduction of speckle for pico-projection systems...Diffractive diffusers (phase gratings) are routinely used for homogenizing and beam shaping for laser beam applications. Another use for diffractive diffusers is in the reduction of speckle for pico-projection systems. While diffusers are unable to completely eliminate speckle they can be utilized to decrease the resultant contrast to provide a more visually acceptable image. Research has been conducted to quantify and measure the diffusers overall ability in speckle reduction. A theoretical Fourier optics model is used to provide the diffuser’s stationary and in-motion performance in terms of the resultant contrast level. Contrast measurements of two diffractive diffusers are calculated theoretically and compared with experimental results. Having a working theoretical model to accurately predict the performance of the diffractive diffuser allows for the verification of new diffuser designs specifically for pico-projection system applications.展开更多
The self-imaging property of multimode waveguides creates a challenging problem when finding the optimal placement position of an out-of-plane coupler for embedded waveguides. This problem is compounded when the waveg...The self-imaging property of multimode waveguides creates a challenging problem when finding the optimal placement position of an out-of-plane coupler for embedded waveguides. This problem is compounded when the waveguides are coupled using a small input such as a vertical cavity surface emitting laser (VCSEL) or a single mode fiber where only some of the modes are generated. When the waveguide system is under filled, the coupling efficiency for the optical vertical interconnect assembly (VIA) can vary by as much as 6.2 dB depending on the length of the proceeding waveguide due to different output fields from the self-imaging property. This requires sweeping each individual VIA over the entire range of possible coupler positions to find the total maximum coupling efficiency. This process increases in complexity when a VIA supports several parallel channels all having a different optical path length. If a VIA can be placed in a calculated position from the end of a terminated embedded waveguide dependent upon the modal structure then blind pick and place methods may be used. The optimal coupler placement was determined based on smallest average VIA attenuation, smallest attenuation variance, and worse-case alignment scenario.展开更多
文摘Diffractive diffusers (phase gratings) are routinely used for homogenizing and beam shaping for laser beam applications. Another use for diffractive diffusers is in the reduction of speckle for pico-projection systems. While diffusers are unable to completely eliminate speckle they can be utilized to decrease the resultant contrast to provide a more visually acceptable image. Research has been conducted to quantify and measure the diffusers overall ability in speckle reduction. A theoretical Fourier optics model is used to provide the diffuser’s stationary and in-motion performance in terms of the resultant contrast level. Contrast measurements of two diffractive diffusers are calculated theoretically and compared with experimental results. Having a working theoretical model to accurately predict the performance of the diffractive diffuser allows for the verification of new diffuser designs specifically for pico-projection system applications.
文摘The self-imaging property of multimode waveguides creates a challenging problem when finding the optimal placement position of an out-of-plane coupler for embedded waveguides. This problem is compounded when the waveguides are coupled using a small input such as a vertical cavity surface emitting laser (VCSEL) or a single mode fiber where only some of the modes are generated. When the waveguide system is under filled, the coupling efficiency for the optical vertical interconnect assembly (VIA) can vary by as much as 6.2 dB depending on the length of the proceeding waveguide due to different output fields from the self-imaging property. This requires sweeping each individual VIA over the entire range of possible coupler positions to find the total maximum coupling efficiency. This process increases in complexity when a VIA supports several parallel channels all having a different optical path length. If a VIA can be placed in a calculated position from the end of a terminated embedded waveguide dependent upon the modal structure then blind pick and place methods may be used. The optimal coupler placement was determined based on smallest average VIA attenuation, smallest attenuation variance, and worse-case alignment scenario.
