length of bore meaning in Chinese

炮膛长度

Therefore , the three fundamentals required to obtain high precise measurements are : 1 ) frequency stability and frequency difference stability of the double - frequency laser source as well as the stable equivalent length of bore ; 2 ) the measuring beam and the reference beam are placed very co - axially ; 3 ) capability of recording the sub - division of the period of phase change and a reversible counter system
因而干涉仪系统达到高精度的基础是：频率及频差稳定的双频激光源、稳定的等效腔长；测量光与参考光合光后有很高同轴度的光路结构；能可靠记录相位差变化周期数的细分及可逆计数系统三部分。