集成双光栅干涉微梁位移测量方法

Interferometric displacement measurement of microcantilevers based on integrated dual gratings

介绍了一种基于集成双光栅干涉和CCD图像测量的微梁位移测量方法,并利用相位差约为π/2的一组光栅实现了扩量程位移检测。利用表面牺牲层工艺制作敏感芯片,在玻璃基底上刻蚀深度约为入射激光波长1/8的凹槽,凹槽上下的两组光栅与正上方对应的梁分别构成两组相位敏感集成光栅单元。利用1级衍射光将集成光栅单元成像在CCD靶面上,梁的位移变化通过CCD图像上对应光斑的灰度值变化来反映。实验结果表明,虽然玻璃凹槽腐蚀深度的误差导致光栅之间的相位差偏离π/2,但所制作的集成双光栅结构实现了多周期的扩量程位移检测,通过接近π/2相位差的两个光栅得到的光强信号的错峰使用,避免了干涉法正弦位移检测信号的峰谷不灵敏位置,实验测得微梁的位移变化为650nm。

A displacement measurement method for microcantilevers based on integrated dual gratings and a CCD image measurement system were presented.The displacement detection range was extended by using two gratings with a phase shift about π/2.The sensor chips were fabricated by surface sacrificial process.Grooves with the depth about 1/8 of the incident laser wavelength were etched on the glass substrate and two adjacent gratings patterned inside and outside of the groove and the reflective undersurface of a cantilever formed two phase sensitive integrated gratings,respectively.The integrated grating units formed an image on the CCD sensing surface through the 1st order diffraction light,and the gray value change of the light spot was related to the displacement change of the corresponding cantilever.Experimental results show that although the phase difference between the gratings deviates from π/2 caused by the depth errors of the etched grooves,the integrated dual gratings extend the range of displacement detection to multi periods.The insensitive areas at peaks and valleys for sinusoidal variation signal of interferometric displacement detection method are avoided by using alternately intensity signals from the two gratings.In the experiment,the measured displacement change of the cantilever is 650 nm.