Synchronizing signal detector for multi-beam optical disk unit

A synchronizing signal detector comprising n detecting circuits for a multi-beam optical disk unit of n optical beams, using integers n, p, m, c, b, q more than one, each of said n detecting circuits comprising:

• a register for storing a p-bit reference synchronizing pattern;
• p-exclusive-NOR circuits for detecting coincidence between each pulse of p-pulses reproduced from a corresponding one of said n optical beams and each pulse of the p-bit reference synchronizing signal pattern to produce coincident pulses each in response to said coincidence;
• a counter for counting a number of said coincident pulses from said p-exclusive-NOR circuits to generate an all-bit coincident signal when bits of the reproduced p-pulses are all coincident with bits of said reference synchronizing signal pattern and to generate a q or more bit coincident signal when q (where o<q<p) or more bits reproduced from the corresponding one of said n-optical beams are coincident with bits of said reference synchronizing signal pattern;
• pulse means for supplying the all-bit coincident signal to each of other n-1 detecting circuits and for receiving said all-bit coincident signal from said other n-1 detecting circuits;
• window pulse generating means for generating when said all-bit coincident signal is generated by said counter for at least m (where o<m.ltoreq.n) of said n-optical beams, a window pulse having an arbitrary width of b-bits, which starts at said all-bit coincident signal;
• a delay circuit for delaying a c-bit (where c=b/2) period the q or more bit coincident signal to produce an output;
• and
• an AND circuit for ANDing the output of said delay circuit and said window pulse;
• wherein output pulses of said AND circuit are regarded as detected synchronizing signals in the corresponding one of said optical beams.