Phase Shift Calibration Method in Optical Sinusoidal Encoder Signals Applied to Servo Track Writer

In this paper, an ultra high precision calibration method of optical sinusoidal encoder signals in spiral servo track writing is proposed to improve position (velocity) regulation in the constant velocity region. The proposed method has been aimed toward non-ideal signal calibration for the imperfect components existing sinusoidal encoders and it applies a digital encoder calibration using a fictitious cosine function. The fictitious cosine function is used for finding phase shift between sine and cosine signals. The proposed method is validated by the experimental implementation, showing noticeable improvement in the position (velocity) error signal. Tracking performance in position error signals is improved up to 40 [%] with a positioner.