Patent ID: 6559951
Filing Date: 2003-05-06
Classification: G01N

Abstract:
An air refractometer, comprising:a vacuum container, the length of the vacuum container being variable in longitudinal direction by moving a movable end thereof, one side of the movable end being a vacuum space and other side of the movable end opposing the one side of the movable end being a space of a test gas; a vacuum-side laser beam advancing inside the vacuum container in the longitudinal direction; a vacuum-side laser interferometer using the vacuum-side laser beam; a gas-side laser beam parallel to the vacuum-side laser beam and advancing inside the space of the test gas; a gas-side laser interferometer using the gas-side laser beam; a drive mechanism for driving the movable end of the vacuum container along the longitudinal direction; a vacuum-side reflector provided to a vacuum-side of the movable end of the ) vacuum container for reflecting the vacuum-side laser beam; and a gas-side reflector provided on a test gas side of the movable end for reflecting the gas-side laser beam, a movement of the vacuum-side reflector being measured by the vacuum-side laser interferometer, a movement of the gas-side reflector being measured by the gas-side laser interferometer, the refractive index of the test gas being measured based on the measured values, wherein the vacuum-side laser beam and the gas-side laser beam are split from a single laser beam and are respectively introduced to the vacuum-side laser interferometer and the gas-side laser interferometer through a single-mode light-waveguides, the respective laser beams irradiated from the respective single-mode light-waveguides being optical measuring light paths between the respective laser interferometers and the respective reflectors, and wherein the optical measuring light path formed by the vacuum-side laser beam and the optical measuring light path formed by the gas-side laser beam are coaxially located sandwiching the movable end of the vacuum container.