Sensor

Abstract

Provided is a sensor having a high SN ratio. The sensor includes a light source, a band pass filter; and a light-receiving element, in which the band pass filter includes a cholesteric liquid crystal layer that is a layer obtained by immobilizing a cholesteric liquid crystalline phase, the cholesteric liquid crystal layer has a region where a refractive index nx in an in-plane slow axis direction and a refractive index ny in an in-plane fast axis direction satisfy nx>ny, and in a case where a selective reflection wavelength of the cholesteric liquid crystal layer is represented by λ, the cholesteric liquid crystal layer has a second selective reflection peak at a wavelength λ/2 and a half-width of the second selective reflection peak at λ/2 is 30 nm or less.

Dependencies are inferred from the claim text.