Visible Wavelength Color Filters using Dielectric Subwavelength Gratings for Backside-illuminated CMOS Image Sensor Technologies

We report transmissive color filters based on subwavelength dielectric gratings that can replace conventional dye-based color filters used in backside-illuminated CMOS image sensor (BSI CIS) technologies. The filters are patterned in an 80-nm-thick poly-silicon film on a 115-nm-thick SiO_2 spacer layer. They are optimized for operating at the primary RGB colors, exhibit peak transmittance of 60-80%, and an almost insensitive response over a ±20° angular range. This technology enables shrinking of the pixel sizes down to near a micrometer

Sparse Diffusion Least Mean-Square Algorithm with Hard Thresholding over Networks

This paper proposes a distributed estimation technique utilizing the diffusion least mean-square (LMS) algorithm, specifically designed for sparse systems in which many coefficients of the system are zeros. To efficiently utilize the sparse representation of the system and achieve a promising performance, we have incorporated L0-norm regularization into the diffusion LMS algorithm. This integration is accomplished by employing hard thresholding through a variable splitting method into the update equation. The efficacy of our approach is validated by comprehensive theoretical analysis, rigorously examining the mean stability as well as the transient and steady-state behaviors of the proposed algorithm. The proposed algorithm preserves the behavior of large coefficients and strongly enforces smaller coefficients toward zero through the relaxation of L0-norm regularization. Experimental results show that the proposed algorithm achieves superior convergence performance compared with conventional sparse algorithms