Sign-Coded Exposure Sensing for Noise-Robust High-Speed Imaging
This work addresses noise issues in high-speed imaging for applications requiring very high frame rates, representing an incremental improvement over existing coded exposure systems.
The paper tackled the problem of noise amplification in high-speed imaging by introducing a Fourier camera with pixel-level sign-coded exposure using Walsh functions, resulting in improved noise robustness and reconstruction of 4kHz frames under ambient light.
We present a novel Fourier camera, an in-hardware optical compression of high-speed frames employing pixel-level sign-coded exposure where pixel intensities temporally modulated as positive and negative exposure are combined to yield Hadamard coefficients. The orthogonality of Walsh functions ensures that the noise is not amplified during high-speed frame reconstruction, making it a much more attractive option for coded exposure systems aimed at very high frame rate operation. Frame reconstruction is carried out by a single-pass demosaicking of the spatially multiplexed Walsh functions in a lattice arrangement, significantly reducing the computational complexity. The simulation prototype confirms the improved robustness to noise compared to the binary-coded exposure patterns, such as one-hot encoding and pseudo-random encoding. Our hardware prototype demonstrated the reconstruction of 4kHz frames of a moving scene lit by ambient light only.