Abstract
We developed a method for calculating the displacement of the beam spot focused on an optical disc by the objective lens for optical pickups. This method is reasonably accurate at predicting the stability in tracking servo control systems. The vibration model of an optical pickup is expressed as the frequency response function of the ratio of the displacement of the beam spot focused on an optical disc by the objective lens to the voltage applied to the tracking coils. The displacement of the beam spot was obtained by adding the product of the focal length of the objective lens and the incident angle of the beam onto the objective lens caused by mirror rotation to the displacement of the objective lens. The calculated values agree well with the measured results. Stiffening the pickup case around the mirror could help to decrease the displacement of the beam spot on an optical disc by 40%.
