Nieradka K, Małozięć G, Kopiec D, Grabiec P, Janus P, Sierakowski A, Gotszalk T
Faculty of Microsystem Electronics and Photonics, Wrocław University of Technology, Wrocław 50-372, Poland.
Rev Sci Instrum. 2011 Oct;82(10):105112. doi: 10.1063/1.3652977.
Here we present an extension of optical beam deflection (OBD) method for measuring displacement and vibrations of an array of microcantilevers. Instead of focusing on the cantilever, the optical beam is either focused above or below the cantilever array, or focused only in the axis parallel to the cantilevers length, allowing a wide optical line to span multiple cantilevers in the array. Each cantilever reflects a part of the incident beam, which is then directed onto a photodiode array detector in a manner allowing distinguishing between individual beams. Each part of reflected beam behaves like a single beam of roughly the same divergence angle in the bending sensing axis as the incident beam. Since sensitivity of the OBD method depends on the divergence angle of deflected beam, high sensitivity is preserved in proposed expanded beam deflection (EBD) method. At the detector, each spot's position is measured at the same time, without time multiplexing of light sources. This provides real simultaneous readout of entire array, unavailable in most of competitive methods, and thus increases time resolution of the measurement. Expanded beam can also span another line of cantilevers allowing monitoring of specially designed two-dimensional arrays. In this paper, we present first results of application of EBD method to cantilever sensors. We show how thermal noise resolution can be easily achieved and combined with thermal noise based resonance frequency measurement.
在此，我们展示了一种用于测量微悬臂梁阵列位移和振动的光束偏转（OBD）方法的扩展。光束不是聚焦在悬臂梁上，而是聚焦在悬臂梁阵列上方或下方，或者仅聚焦在与悬臂梁长度平行的轴上，使得一条宽光束能够跨越阵列中的多个悬臂梁。每个悬臂梁反射一部分入射光束，然后该光束以能够区分各个光束的方式被引导到光电二极管阵列探测器上。反射光束的每一部分在弯曲传感轴上的发散角与入射光束大致相同，就如同单束光一样。由于OBD方法的灵敏度取决于偏转光束的发散角，因此在提出的扩展光束偏转（EBD）方法中仍能保持高灵敏度。在探测器处，同时测量每个光斑的位置，无需对光源进行时间复用。这提供了对整个阵列的实时同步读出，这在大多数竞争方法中是无法实现的，从而提高了测量的时间分辨率。扩展光束还可以跨越另一排悬臂梁，从而允许对专门设计的二维阵列进行监测。在本文中，我们展示了EBD方法应用于悬臂梁传感器的初步结果。我们展示了如何轻松实现热噪声分辨率，并将其与基于热噪声的共振频率测量相结合。
