DVD探頭自動聚焦位移回饋系統之研製
Optical Displacement Feedback on Auto-Focusing DVD Probe System
Date Issued
2005
Date
2005
Author(s)
Li, Kun-Hsun
DOI
zh-TW
Abstract
In this research, a DVD probe system by means of auto-focusing control principle was developed. In this system, the distance between objective lens and workpiece is not exactly at the focal distance;therefore the focus error signal(FES) from photodiode will actuate the voice coil motor(VCM) to keep the lens to be within the focal distance.
Furthermore, in order to avoid the hysteresis error of VCM in the DVD-pickup head, the second VCM was applied and connected in parallel with the first VCM. The second VCM was regarded as a displacement sensor observed by the Michelson interferometer.
According to Ohm’s law, these two VCMs are driven by the equivalent current which ensures the VCMs to move synchronously. Thus, the displacement of the second VCM can be obtained by counting the fringes of interference. Finally, the displacement or surface profile of the workpiece can be obtained and also achieve a higher resolution of contour measurement.
Subjects
DVD讀取頭
干涉儀
音圈馬達
DVD pickup head
interferometer
voice coil motor
Type
thesis
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