A Study on the Mechanism of a New High Speed Scanning Miniature Nano-Measurement Probe

The primary purpose of this research is to adopt a commercially available DVD pickup head and modify it to become a high-speed scanning nano-measurement probe. With the principle of astigmatism the probe can execute the autofocusing motion by an imbedded voice coil motor (VCM) following the height change of the tested object in the vertical Z-direction. Given high precision triangular current signal with appropriate frequency to the input ports of tracking, the same VCM can be moved along the lateral X-direction for profile scanning. Firstly this paper presents the structure of DVD pickup head, the theory of autofocusing and auto scanning, and the developed controller. Then experimental setups and accuracy calibration will be introduced. In order to achieve a bi-directional precision measurement in autofocusing and scanning, this study has developed a hysteresis error compensation scheme by a DSP-32 integrated system. In association with a high precision linear stage in Y-direction, this high precision micro/nano optical probe can measure the 3D profile of the miniature object successfully at fast speed.