Patent ID: 8319866

Claim:
An imaging optical system comprising: a light control element formed of a dye pigment-containing dichroic guest-host liquid crystal, and that is disposed on a light path to adjust a quantity of incident light for an image sensing device; and an optical filter disposed on the light path, and that includes an infrared absorbing material, the optical filter having a spectral transmittance that satisfies the following conditions (1), (2), and (3) 0.6 <T IRCF(580) /T IRCF(540) <1.05 (1) 0.1 <T IRCF(640) /T IRCF(540) <0.5 (2) | T IRCF(700) /T IRCF(540) |<0.05 (3) where T IRCF(540) is the spectral transmittance of the optical filter for the light with a wavelength of 540 nm, T IRCF(580) is the spectral transmittance of the optical filter for the light with a wavelength of 580 nm, T IRCF(640) is the spectral transmittance of the optical filter for the light with a wavelength of 640 nm, and T IRCF(700) is the spectral transmittance of the optical filter for the light with a wavelength of 700 nm.