Abstract: An apparatus and method is provided for use on the pickup head of an optical disc drive for the purpose of adjusting the pickup head to the optimal focus point through a featured tree-structured search algorithm. The apparatus and method can perform the adjustment automatically so as to eliminate the need to use laborious work to make the adjustment in manufacture. The apparatus is activated each time the optical disc drive is started so as to offset the unbalanced condition in the focusing error signal, which allows the optical disc drive to perform the access operation more reliably. Moreover, the apparatus is realized in a digital manner that allows easy implementation and a low manufacturing cost.

Abstract: An auto gain adjustment apparatus and method are provided for the focusing/tracking control of the optical pickup of an optical disc drive. The gain is obtained by utilizing the self-sustained oscillation from a non-linear component in the optical disc drive, such as a relay circuit with hysteresis. This gain adjustment apparatus and method is more advantageous than the prior art in that the gain can be automatically adjusted without involving manual work and the need to apply an externally generated oscillating test signal. The apparatus and method therefore allows the manufacture and utilization of the optical disc drive to be more efficient and cost-effective.

Abstract: A control device to locate the pickup head on the desired position yielded by the operation of seek is taken in two parts. The first part is utilizing the velocity control to prevent the fluctuation problem of the bi-mass system and the second part is switching the operation to the mode of position control gradually, so that the pickup head can reach the destination precisely and minimize the problem of fluctuation and increase the successful rate of the tracking control. Moreover, this invention has utilized a feedforward control to properly compensate the steady state error originated from the characteristics of system or friction, a position feedback control and a switching factor to gradually switch between the modes of velocity and position. Thus, the position and velocity of the sled motor can be controlled at the same time to allow the pickup head to reach the destination smoothly as expected by the designed of the velocity profile. The tracking control therefore is done smoothly.