All-optical image denoising using a diffractive visual processor
Cagatay Isıl Tianyi Gan F. Onuralp Ardic Koray Mentesoglu Jagrit Digani Huseyin Karaca Hanlong Chen Jingxi Li Deniz Mengu Mona Jarrahi Kaan Akşit Aydogan Ozcan
Image denoising, one of the essential inverse problems, targets to remove
noise/artifacts from input images. In general, digital image denoising
algorithms, executed on computers, present latency due to several iterations
implemented in, e.g., graphics processing units (GPUs). While deep
learning-enabled methods can operate non-iteratively, they also introduce
latency and impose a significant computational burden, leading to increased
power consumption. Here, we introduce an analog diffractive image denoiser to
all-optically and non-iteratively clean various forms of noise and artifacts
from input images - implemented at the speed of light propagation within a thin
diffractive visual processor. This all-optical image denoiser comprises passive
transmissive layers optimized using deep learning to physically scatter the
optical modes that represent various noise features, causing them to miss the
output image Field-of-View (FoV) while retaining the object features of
interest. Our results show that these diffractive denoisers can efficiently
remove salt and pepper noise and image rendering-related spatial artifacts from
input phase or intensity images while achieving an output power efficiency of
~30-40%. We experimentally demonstrated the effectiveness of this analog
denoiser architecture using a 3D-printed diffractive visual processor operating
at the terahertz spectrum. Owing to their speed, power-efficiency, and minimal
computational overhead, all-optical diffractive denoisers can be transformative
for various image display and projection systems, including, e.g., holographic
displays.