表面轮廓的测量可以评定零件表面的光滑程度，为了实现高精度测量，提出了应用电子直接调制激光束的频率和外差相干的方法对表面轮廓进行测量。采用差动多普勒的测量原理，实现数字测量及光路补偿；电子直接调制激光束频率的技术减小了系统体积，降低了成本；光纤传输提高了抗干扰的能力；测量信号的跟踪放大，提高了分辨率。通过电路调试并对产生误差的项进行分析补偿。实验表明，该技术的测量不确定度小于0.1%。

Measurement of surface profile can evaluate the smoothness of components. In order to implement measurement with high precision, it comes up with methods for surface-profile measurement, which are the electricdirect modulation for laser-beam frequency and the heterodyne coherence. Through the principle of differential Doppler measurement, we can achieve the digital measurement and optical compensation. Through the technology of electric-direct modulation for laser-beam frequency, we can reduce the size of system and cost. Besides, the transmission by optical fiber has improved the ability of immunity. At the same time, it can improve the resolution by amplifying and tracking the signal measurement. By debugging the circuit, it provides a compensation for the error analysis. The experimental results show that the measurement uncertainty of the technology is less than 0.1%.