重构定心法提高微球轴向位移测量信噪比

The Reconstruction Centering Method to Improve the Signal-to-Noise Ratio of the Axial Displacement Measurement of Microspheres

摘要: 微球轴向位移的测量容易受到环境噪声干扰，从机理上提高测量的精准性和信噪比，是解决噪声问题的重要途经。离轴数字全息显微技术能够测量微球轴向位移1，测量分辨力达到纳米级别，而且对微球的位置没有特殊要求。全息定位标志的精准度是测量精准的重要保障。然而，利用传统的图像定心法定位微球中心，为全息定位标志的计算引入误差。本文提出重构定心法，用重构的相位中心定位微球中心，校正全息定位标志，提高测量信噪比。通过对5 m直径微球测量轴向位移，测量信噪比提升20%，验证重构定心法的有效性。

Abstract: The measurement of the axial displacement of microspheres is easily disturbed by environmental noise, and improving the accuracy and signal-to-noise ratio of the measurement mechanism is an important way to solve the noise problem. Off-axis digital holographic microscopy can measure the axial displacement of microspheres, and the measurement resolution can reach the nanometer level, and there are no special requirements for the position of the microspheres. The accuracy of holographic positioning marks is an important guarantee for accurate measurement. However, using the traditional picture centering method to locate the center of the microspheres can introduce errors in the calculation of holographic positioning marks. This article proposes a reconstruction centering method, which uses the reconstructed phase center to locate the center of the microsphere, corrects the holographic positioning mark, and improves the measurement signal-to-noise ratio. By measuring the axial displacement of 5 m diameter microspheres, the signal-to-noise ratio was improved by 20% to verify the effectiveness of the reconstruction centering method.