Detecting oscillation amplitude and defects of hard disk rotating in high speed by laser Doppler technique

Laser Doppler technique is widely used in industry for the purpose of detecting vibration and oscillation. Many researchers have found that using non-contact laser vibrometry to measure surface roughness of disk under dynamic status is more difficult than that of the static condition. In this paper, we proposed a laser Doppler technique for the purpose of measuring the oscillation amplitude and defects of hard disk rotating in high speed. Laser light source, optical Doppler system, detector and data process system were integrated in our experimental system. The whole system was calibrated using a sinusoid generator. The method for converting the measured voltage signals into the corresponding size data was described in detail. It was found that the average size of defects of the hard disk in our experiment is from 1 μm to 5 μm. The developed technique may be useful for quality control in real time in mass production processes.