Astigmatic detection was originally developed in the optical disk recording technologies to detect the defocused condition of the disk away from the optical pickup head. Our team, comprising a group in the institute of Physics, Academia Sinica and a group in the Department of Mechanical Engineering of National Taiwan University, has discovered that the commercial DVD optical pickup head has a sensitivity to detect linear displacements of sub-angstrom scale and angular changes in nrad. In addition, the detection spot size is smaller than 1 μm and the detection bandwidth is higher than 60 MHz, thus the DVD optical pickup head can detect high-frequency movements of small objects. Furthermore, it can be purchased easily with a low cost. This opens up various applications from low-cost education and framing tools to sophisticated research instruments or equipments. In this article, we will describe the principle of astigmatic detection system (ADS), development and applications of the technology in precision instrumentation, and world-leading ADS technologies developed in our team. We hope to cooperate with other scientists and experts in industry to broaden the application of ADS technologies, and to even bring forth new technologies and industries.
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