LENGTH MEASURING METHOD Russian patent published in 2015 - IPC G01J3/14 

FIELD: measurement equipment.

SUBSTANCE: length measurement is based on measurement of intermodal frequency of a Fabry-Perot interferometer built on the basis of the measured length using radiation of a single-frequency retuned laser and stable interference bands of vacuumised Fabry-Perot standard for which intermodal frequency is known. Both interferometers are simultaneously irradiated by the single-frequency retuned laser. Accurate determination of intermodal frequency of the Fabry-Perot interferometer is achieved by subsequent tuning and stabilisation of frequency of the single-frequency retuned laser in the centre of interference bands of two far spaced modes of the Fabry-Perot interferometer between each other with simultaneous recording of the number of its intermodal gaps between those modes. A frequency interval value between these equally spaced modes is determined as per the number of intermodal frequencies of the Fabry-Perot standard, including its possible fractional part of the interference order. As per the measured frequency interval between these equally spaced modes of the Fabry-Perot interferometer and as per the number of its recorded intermodal gaps at this frequency interval there determined is an accurate value of intermodal frequency of the Fabry-Perot interferometer and the measured length.

EFFECT: enlarging a measurement range.

1 dwg