APPARATUS AND METHOD FOR ADJUSTING FOCUS BIAS AUTOMATICALLY

摘要

PURPOSE: An automatic control system of focus bias is provided to eliminate unstable focus bias factors by receiving data from secondary RF(Radio Frequency) average signals, the average of primary RF average signals. CONSTITUTION: A pickup unit(10) reads data out of an optical disk. An RF signal player(12) is connected with the pickup unit to output RF signals. A focus bias adjusting unit(34) is connected with the RF signal player to generate primary/secondary RF average signals from the RF signals. The focus bias adjusting unit has a primary RF average signal generator(34a) for outputting the primary RF average signal from the RF signal. A secondary RF average signal generator(34b) is connected with the primary one to output the secondary RF average signal by sampling the primary RF average signal. The focus bias adjusting unit obtains the focus bias adjusting degree by analyzing the secondary RF average signal. Therefore, focus bias is adjusted automatically.