| 摘要 |
PROBLEM TO BE SOLVED: To provide a railway vehicle measurement method capable of measuring the running speed of a railway vehicle with high accuracy even when a laser beam is emitted to any object present on the rail laying side such as a rail, a sleeper, gravel, auxiliary rail and ATS.SOLUTION: A ground speed is measured through the steps of: mounting a differential LDV on a railway vehicle; emitting a laser beam from a laser source to an object on a track laying side such as a rail, a sleeper, gravels, an auxiliary rail and an ATS; receiving scattered light from the object at light receiving elements of the differential LDV and extracting a Doppler signal; and measuring the ground speed from the Doppler signal. The laser Doppler signal is obtained through the steps of: collimating the laser beam to be emitted to the track laying side from the laser source; branching the beam into two directions; emitting one of the collimated branched beams to an object on the track laying side at an intersection angle &phgr;; branching the other collimated branched beam into two or more directions; emitting the two or more branched laser beams to the object on the track laying side from a direction different from the direction of the one collimated branched beam; making the one collimated branched laser beam and the two or more branched laser beams cross at two or more points on an irradiation axis of the laser beam; and obtaining the laser Doppler signal with the inside of two or more crossing regions as a focal point. |
