Optical disc reproduction apparatus

An optical disc reproduction apparatus, comprising:

• a signal reproduction circuit configured to reproduce a wireless frequency signal from an optical disc, and convert the wireless frequency signal to a digital signal including a plurality of digital values in synchronization with a predetermined sampling clock;
• a demodulation circuit configured to perform demodulation to the digital signal;
• and
• a jitter detection circuit configured to detect an absolute jitter value to be an index of signal quality of the digital signal in parallel with the demodulation by the demodulation circuit,
• wherein the jitter detection circuit includes
• an instantaneous jitter information detection section configured to detect, based on first and second digital values of the digital signal which indicate different polarities relative to a predetermined reference value, an instantaneous gradient value corresponding to a difference value between the first and second digital values, and an instantaneous deviation value corresponding to a difference value between an intermediate value between the first and second digital values and the reference value,
• an information conversion section configured to convert, based on an inversely proportional conversion table showing a correspondence relationship between the instantaneous gradient value and an inversely proportional value which is inversely proportional to the instantaneous gradient value, the instantaneous gradient value detected by the instantaneous jitter information detection section to the inversely proportional value,
• an arithmetic section configured to detect an instantaneous variance value by multiplying the instantaneous deviation value detected by the instantaneous jitter information detection section and the inversely proportional value obtained by the information conversion section together, and squaring a value obtained by the multiplication, and detect an integrated value by accumulating the instantaneous variance value, and
• a standard deviation detection section configured to detect a square root of a mean value of the integrated value as the absolute jitter value, and
• the information conversion section limits the inversely proportional value so that the inversely proportional value is smaller than a predetermined value.