By analyzing the direct frequency modulation and optical feedback effect of laser diode, a theoretical model for measuring small vibration displacement and velocity is discussed.

分析了在直接频率调制下，激光二极管中的光反馈效应，探讨了振动微小位移和速度的理论模型。

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Direct digital synthesis (DDS) is an all digital frequency synthesis technique. Because of its special theory and construction, it has many kinds of modulation capability.

直接数字式频率合成(DDS)技术是一种全数字频率合成技术，其特殊的原理和结构使它具有多种调制能力。

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The intrinsic frequency of a beaker can be determined by means of direct determination, resonance or water drip modulation, and each of the methods makes use of the Lissajous figure.

烧杯的固有频率可以用直接测量法、共振法或水滴流调制法加以测定，各法中均利用利萨如图形。

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