Using pseudo-random speckle patterns to image targets is efficient (high-resolution imaging), but most approaches require bulky, expensive, complex, and slow machinery. A smaller device capable of generating random speckles is required to apply this technique to biomedical imaging, such as ultra-thin endoscopy or in vivo neural imaging.
A group of scientists demonstrated using a multimode fiber (MMF) with an integrated optical phased array (OPA) chip for single-pixel imaging in potential biomedical applications.
Previous research has shown that illuminating a target with random speckles rather than a focused spot improves an imaging process’s spatial resolution. This is because, unlike a focused spot, random speckle illumination comprises interference patterns with higher spatial frequency elements.
The group generated different random speckle patterns to illuminate the target by integrating an MMF output with an OPA chip, which splits the input light into several independent phase shifters.
Although they had previously demonstrated random-speckle imaging using only an OPA without MMF, they could not resolve many points due to the OPA’s limited number of phase shifters. Surprisingly, they discovered in this work that transmitting through an MMF can greatly increase the number of resolvable points (high-resolution imaging).
The image of the target can be quickly reconstructed using a simple matrix multiplication operation of the illumination pattern matrix and the transmitted optical power matrix.
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