Abstract
Computational imaging with random encoding patterns obtained by scattering of light in complex media has enabled simple imaging systems with compelling performance. Here, we extend this concept to axial reflectivity profiling using spatio-temporal coupling of broadband light in a multimode fiber (MMF) to generate the encoding functions. Interference of light transmitted through the MMF with a sample beam results in path-length-specific patterns that enable computational reconstruction of the axial sample reflectivity profile from a single camera snapshot. Leveraging the versatile nature of MMFs, we demonstrate depth profiling with bandwidth-limited axial resolution of 13.4 µm over a scalable sensing range reaching well beyond one centimeter.
Highlights
Integration of computational reconstruction into the process of image formation can offer increased measurement flexibility compared to conventional imaging systems whose performance generally depends on well-engineered optics [1,2]
To leverage the random encoding functions generated by a multimode fiber (MMF) for imaging axial reflectivity profiles, it is crucial to understand how the spatio-temporal coupling and modal delay in the fiber structure the random encoding matrix (REM)
With the neutral density filter and the gold-coated mirror placed in the sample arm, we examined the energy distribution, the sensitivity matrix, and residual correlation among the encoding functions while varying physical parameters such as coupling regime, mode mixing, and MMF length, before performing proof-of-principle sample imaging of custom-made phantoms
Summary
Integration of computational reconstruction into the process of image formation can offer increased measurement flexibility compared to conventional imaging systems whose performance generally depends on well-engineered optics [1,2]. Complex or disordered media that generate random patterns to serve as encoding functions for computational reconstruction have been shown to enable imaging with improved lateral resolution [4,5,6], extended field of view [4,7], increased depth of focus [8], of 3D objects [9,10], at multiple wavelengths [11], with higher frame-rate [12], or at X-ray wavelength [13], which otherwise cannot be achieved without substantially more sophisticated hardware. The MMF’s spatio-spectral coupling has been employed for high resolution spectrometry with a broad sensing range [22,24], and recently for temporal profiling [25]. Strategies for encoding the axial dimension are missing
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