Patent ID: 7319824

Claim:
A method for controlling an identification point for binarization in an optical signal receiver, the receiver including a photoelectric conversion section which receives an optical signal into which a data signal is modulated with a frame format and converts the optical signal into an electric signal corresponding to the intensity of the optical signal, a binarization processing section which compares the electric signal output from the photoelectric conversion section with a predetermined identification point electric signal, to thus output the electric signal as binarized digital data, and a demodulation processing section for demodulating, from the digital data output from the binarization processing section, frame information into which an optical signal received by the photoelectric conversion section is modulated, by means of performing frame capture operations and error correction operations, the method comprising: an error correction count acquisition step for acquiring the number of error correction operations performed by said demodulation processing section; a capture error determination step for determining whether or not a capture error has arisen during frame capture operation performed by said demodulation processing section; a target value arrival determination step for determining whether or not the number of error correction operations performed by said demodulation processing section has reached a target value when said capture error is determined not to have arisen in said capture error determination step; an identification point electrical signal increment/decrement step for leaving said identification point electrical signal unchanged when said number of error correction operations is determined to have reached a target value but incrementing or decrementing said identification point electrical signal within a predetermined increment/decrement range in such a way that said number of error correction operations approaches said target value when said number of error correction operations is determined not to have reached said target value; and an increment/decrement range reduction step for curtailing an increment/decrement range for incrementing or decrementing said identification point electrical signal in said identification point electrical signal increment/decrement step when said capture error has arisen.