A Novel Dual-Differential Edge Sensor Based on the Eddy Current Effect

Abstract

In this article, a kind of edge sensor based on the eddy current effect is proposed to realize accurate detection of the nano-level resolution in a large temperature span. Compared with edge sensors with different principles used in optical telescope projects, eddy current edge sensor has the advantages of being insensitive to nontarget direction and immune to nonferromagnetic medium. The proposed dual-differential edge sensor (DDES) greatly simplifies its installation and reduces the number of support components for sensors to half by replacing the complementary symmetrical installation method. By analyzing the detection principle, a kind of precise demodulation circuit and real-time temperature compensation method is also designed to guarantee the sensor’s ultrahigh stability. The prototype of the sensor is manufactured and verified that the resolution can reach within 2 nm in the range of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$300 ~\mu \text{m}$ </tex-math></inline-formula> , and the temperature drift (TD) performance is less than 6 nm/°C under the large temperature span from −25 °C to +25 °C. The installation error measurement convinced that the current structure has an excellent installation error tolerance, which has the potential to apply in the engineering application of astronomical telescope mirror splicing.