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

摘要

Optical signals necessitate using filters that selectively transmit or reflect lightwith the desired wavelength information. In visual imaging-related devices, acolor filter acts as a wavelength selector to extract certain information fromthe incident light. To overcome the limitations of commercial pigmented colorfilters, 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 itsselective reflection. However, most of the research has been limited to thecontrol of conventional reflection rather than transmission wavelength. Thisstudy proposes an electrically wavelength-tunable color filter with high opticaltransmittance using a heterogeneous CLC with extremely small voltages notexceeding 1.4 V. Electrothermal tuning of CLC is approached so thattransmission wavelength of the device can be tuned among red, green, andblue. Moreover, analog pixel binning using CLC color filters is explored in atetra-layout beyond state-of-the-art pixel binning with post-capture digitalimage processing. Dynamic and direct binning can prevent the qualitydegradation of the images captured under low-light illumination in imagesensors. The wavelength-tunable transmission color filter proposed in thisstudy is expected to facilitate future electro-optical dynamic color filterapplications.