Patent ID: 8630037
Filing Date: 2014-01-14
Classification: G02B,G02F

Abstract:
1. A near-infrared optical shutter for use with an optical instrument that in operation receives light in visible and near-infrared wavelength regions of an electromagnetic radiation spectrum of frequencies characterizing light and that includes a light detection sensor characterized by spectral light sensitivity in which a near-infrared light sensor band region has a shorter wavelength boundary and a longer wavelength boundary, the shorter wavelength boundary being located adjacent the visible light region of the electromagnetic radiation spectrum, the optical shutter comprising: a multiple-bandpass filter characterized by a bandstop filter region located between a first bandpass filter region and a second bandpass filter region, the first bandpass filter region passing visible light wavelengths, the bandstop filter region blocking near-infrared light of wavelengths within the near-infrared light sensor band region, and the second bandpass filter region passing near-infrared light of longer wavelengths than the wavelength of the longer wavelength boundary of the near-infrared light sensor band region; first and second near-infrared polarizing filters that are tuned to pass visible light wavelengths in the first bandpass filter region and near-infrared light wavelengths in the second bandpass filter region; and a polarization state changer positioned between the first and second near-infrared polarizing filters and optically associated with the multiple-bandpass filter, the polarization state changer responsive to a control signal to provide selectively one of a first light state and a second light state, the polarization state changer in the first light state causing transmission of visible light wavelengths in the first bandpass filter region and substantially reducing transmission of near-infrared light wavelengths in the second bandpass filter region from the optical shutter, and in the second light state causing transmission of visible light wavelengths in the first bandpass filter region and substantially increasing transmission of near-infrared light wavelengths in the second bandpass filter region from the optical shutter.