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A Digital Phase-Lock Method for AOD Scanning Measurement System

Feng, Gao, Wang, Xuanze and Jiang, Xiang (2012) A Digital Phase-Lock Method for AOD Scanning Measurement System. International Journal of Mechanic Systems Engineering, 2 (1). pp. 42-47. ISSN 2225-7403

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    Abstract

    An acoustic-optic deflector (AOD) is used as a beam scanning actuator in a heterodyne interferometer for nano-scale surface measurement. In order to obtain the phase difference between the reference signal and measurement signals, a digital phase-locking method is proposed using high speed A/D sampling and digital signal processing. Considering the measured signal frequency incident upon the photo-detector is double that of the reference signal, the latter is first squared in order to match the measured signal frequency. The phase difference can then be obtained by calculating the correlation coefficient between the two signals. Experimental results show this method is flexible and can be used in real time. The measurement results are not affected by the variation of the DC offset and amplitude of the measured signals. Error analysis also demonstrates the proposed digital phase-lock method, which is accurate with resolution of 0.25nm. It can be used to replace the lock-in amplifier which is traditionally used in this kind of application and can therefore greatly reduce the cost of the measurement system.

    Item Type: Article
    Subjects: Q Science > QC Physics
    Schools: School of Computing and Engineering
    Related URLs:
    Depositing User: Feng Gao
    Date Deposited: 11 Oct 2012 13:42
    Last Modified: 11 Oct 2012 13:42
    URI: http://eprints.hud.ac.uk/id/eprint/15352

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