Aimed at high-precision measurement for large plane

a laser measurement system for plane based on sine modulation is presented.In this system

LD is used as the light source and projected onto a piece of cylindrical lens.With direct beam expanding

the cylindrical lens transmits a kind of sectorial laser plane

that is

the reference plane for the measurement system.The position of laser plane is then detected by PSD.Some factors influencing the system accuracy are analyzed.To reduce the error caused by those factors

the method of LD sine modulation is proposed.Calibration and stability test are carried out.The experimental results show that the measurement system is of high precision and high stability.