Asymmetrical transmission windows for daily privacy protection using cholesteric liquid crystals

A method for realizing an asymmetrical transmission window (ATW) for daily privacy protection using cholesteric liquid crystals (CLCs) is demonstrated. People outside a private space can see people inside through a common window. To protect the individual privacy of people inside who can still see people outside, windows should be replaced with ATWs, which comprise a quarter-wave plate sandwiched between a linear polarizer and a CLC plate. The linear polarizer is set to face the space that requires privacy protection, whereas the light-source wavelength in the private space should be set within the CLC reflection band. The light source in the private space that passes through the linear polarizer and quarter-wave plate is completely reflected by CLCs, whereas the ambient light outside is partially reflected by CLCs. Therefore, people outside the private space cannot see the people inside, who can still view the scene outside through the ATW. Moreover, this study also elucidates an extended conceptual technique that adopts a white light source in a private space to achieve privacy protection using the proposed ATWs. The proposed ATWs can also be switched to double-sided transparent or scattering windows by applying suitable electric fields.