Patent ID: 7652971

Claim:
A threshold current modifying device, comprising: an optical device including: an optical pickup head configured to generate an output power when an operating current larger than a threshold current of the optical pickup head is provided to the optical pickup head, wherein the threshold current is related to a temperature of the optical pickup head by a functional relationship; a threshold current calculating module configured to receive a temperature signal from the optical pickup head at first and second temperatures of the optical pickup head, to output a threshold current signal according to the first temperature, the second temperature and the functional relationship, wherein the threshold current calculating module comprises: a temperature-to-threshold current table configured to respectively associate a first threshold current value and a second threshold current value to the first temperature and the second temperature; and a threshold current looking-up unit configured to receive the temperature signal, to respectively look up the first and the second threshold current values in the temperature-to-threshold current table according to the first temperature and the second temperature, to compute a difference between the first threshold current value and the second threshold current value, and to output the threshold current signal according to the difference; and a power control module configured to receive the threshold current signal and to adjust the operating current according to the threshold current signal.