Patent ID: 7289405

Claim:
An apparatus for detecting a type of an optical disc inserted into an optical disc system, the apparatus comprising: an analog-to-digital converter that converts a focus error signal into an n-bit voltage data; a duty measurer that compares the n-bit voltage data with a positive noise voltage level and a negative noise voltage level, upcounts by a predetermined value if the n-bit voltage data is higher than the positive noise voltage level or lower than the negative voltage level, and outputs the upcounted result as a duty of the focus error signal, the duty measurer comprising: a comparing unit that generates an upcount signal if the n-bit voltage data is higher than the positive noise voltage level or lower than the negative voltage level and generates a hold signal if the n-bit voltage data is lower than the positive noise voltage level or higher than the negative voltage level, wherein the comparing unit comprises: a buffer register that buffers the n-bit voltage data; an absolute calculator that calculates an absolute value of the n-bit voltage data buffered by the buffer register; and a comparator that compares the absolute value output from the absolute value calculator with the positive noise level, generates the upcount signal if the absolute value is greater than the positive noise voltage level, and generates the hold signal if the absolute value is less than the positive noise voltage level.