MEASURING DEVICE

To provide a measuring device which is suitable for increasing or decreasing the temperature in an optical resonator to a desired temperature and conducting measurement.SOLUTION: A gas measuring device 100 comprises: an optical resonator 3 for resonating light; a light generator 1 for generating light with which the optical resonator 3 is irradiated; and an optical detector 6 for detecting light taken out of the optical resonator 3. The optical resonator 3 includes a plurality of mirrors 31, 32, holding members 33, 34, a cylindrical member 36, a cylindrical member 37, and a temperature adjuster 38. The coefficient of thermal expansion of the holding members 33, 34 is lower than the cylindrical member 36. The cylindrical member 36 includes a portion whose thermal conductivity is higher than the holding members 33, 34 and bellows 36a, 36b whose flexibility is higher than a first portion. The cylindrical member 37 has equivalent or higher thermal conductivity than the cylindrical member 36, and is disposed through to the positions of the plurality of mirrors 31, 32 including the inside of the bellows 36a, 36b.SELECTED DRAWING: Figure 2 【課題】光共振器内の温度を目標温度まで加熱または冷却して測定を行うことに適した測定装置を提供する。【解決手段】ガス測定装置１００は、光を共振させる光共振器３と、光共振器３に照射するための光を発生させる光発生器１と、光共振器３から取り出された光を検出する光検出器６と、を備える。光共振器３は、複数のミラー３１，３２と、保持部材３３，３４と、円筒部材３６と、円筒部材３７と、温度調節器３８と、を備える。保持部材３３，３４は、円筒部材３６より熱膨張率が低い。円筒部材３６は、保持部材３３，３４より熱伝導率の高い部分と、第１部分に比べて伸縮性の高いベローズ３６ａ，３６ｂと、を有する。円筒部材３７は、円筒部材３６と同等以上の熱伝導率を持ち、ベローズ３６ａ，３６ｂの内側を含む複数のミラー３１，３２の位置まで設けられる。【選択図】図２