Patent ID: 8178826

Claim:
A light source device comprising: a semiconductor light emitting element for emitting light; and a control section for controlling the semiconductor light emitting element in accordance with an input value received by the control section, the control section comprising: a supply section for supplying the semiconductor light emitting element with a drive current, the drive current being based on the input value and an estimated threshold current of the semiconductor light emitting element, and an estimation section for generating the estimated threshold current used by the supply section using the value of the drive current and a detected value related to the amount of light emitted from the semiconductor light emitting element, wherein the estimation section obtains an estimation of the amount of light emitted from the semiconductor light emitting element using the amount of the drive current and the estimated threshold current, and feeds back an estimated threshold current to the estimation section comprising the difference between a detected emission amount and the estimated emission amount, wherein the control section further comprises an inhibit section for inhibiting the feed-back of the difference between the detected emission amount and estimated emission amount when the semiconductor light emitting element stops emitting light.