Combined blazed grating and microlens array for color image sensing

A combination of a blazed grating and a microlens array is discussed for high-efficiency color image sensing. Each image segment includes a microlens with blazed grating and three photodiodes assigned to red, green, and blue colors. Color-splitting performances of design examples were simulated by the two-dimensional finite-difference time-domain method. It was found that the spectral characteristics were similar to the ideal NTSC specifications for a segment size of 10 mu m with a polymer microlens and a TiO2 blazed grating. A prototype consisting of a honeycomb array of microlenses of 15 mu m cell diameter and a TiO2 blaze grating of 1.22 mu m period and 0.35 mu m height was fabricated and-characterized. Power utilization efficiency of about 60% was predicted theoretically and estimated experimentally, which is much higher in comparison to a conventional image sensor utilizing color filters. (C) 2014 The Japan Society of Applied Physics