Electrically Wavelength‐Controllable Color Filters with High Optical Transmittance Using Heterogeneous Chiral Liquid Crystals

Abstract

AbstractOptical signals necessitate using filters that selectively transmit or reflect light with the desired wavelength information. In visual imaging‐related devices, a color filter acts as a wavelength selector to extract certain information from the incident light. To overcome the limitations of commercial pigmented color filters, structural color filters with controllable photonic bandgaps (PBGs) have recently attracted significant interest. Especially, chiral liquid crystal (CLC) has been widely investigated for tunable color filters owing to its selective reflection. However, most of the research has been limited to the control of conventional reflection rather than transmission wavelength. This study proposes an electrically wavelength‐tunable color filter with high optical transmittance using a heterogeneous CLC with extremely small voltages not exceeding 1.4 V. Electrothermal tuning of CLC is approached so that transmission wavelength of the device can be tuned among red, green, and blue. Moreover, analog pixel binning using CLC color filters is explored in a tetra‐layout beyond state‐of‐the‐art pixel binning with post‐capture digital image processing. Dynamic and direct binning can prevent the quality degradation of the images captured under low‐light illumination in image sensors. The wavelength‐tunable transmission color filter proposed in this study is expected to facilitate future electro‐optical dynamic color filter applications.