Fringe Disappearance in Self-Mixing Interferometry Laser Sensors: Model and Application to the Absolute Distance Measurement Scheme

The fringes disappearance phenomenon in the self-mixing interferometry occurs whenever the external round-trip phase at free-running state is modulated by either external modulation such as external cavity length changes or internal modulation when the laser injection current is modulated with a high back-scattered light power. This phenomenon has been observed by many authors for harmonic motion or vibration application, and more recently in the case of the absolute distance measurement scheme when the laser injection current is modulated in the triangle waveform. However, there are no clear explanations on the fringes disappearance phenomenon and its dependence on the self-mixing's regimes. In this paper, a novel approach that depicts the mechanism of interferometric fringes disappearance is proposed that highlight with a new perspective the impact of the coupling strength between the laser and the external cavity on the number of missing fringes. The proposed modelling is validated by a set of measurements using the optical feedback interferometry absolute distance measurement scheme.

自混频干涉测量中，边缘消失现象无论在自由运行状态下外循环行程相位受到外部调制（如外部腔长度的变化）或内部调制（当激光注入电流受高背向散射光功率调制时）的影响都会发生。许多作者已经观察到该现象在谐波运动或振动应用中的出现，以及最近在绝对距离测量方案中，当激光注入电流以三角波形调制时的情况。然而，关于边缘消失现象及其对自混频状态依赖性的解释尚不明确。在本文中，提出了一种新颖的方法，描绘了干涉条纹消失的机制，并通过新的视角强调了激光与外部腔之间耦合强度对缺失条纹数的影响。所提出的模型通过使用光学反馈干涉测量绝对距离测量方案的一组测量进行了验证。