Patent ID: 7280575

Claim:
A circuit for automatically detecting an eye safety fault condition in a laser transmitter while accounting for transient conditions, the circuit comprising the following: a laser current detection circuit configured to detect when there is a potential that the laser is emitting light at levels that exceed a predetermined threshold; and a timer circuit configured to cause the laser to cease operation when one or more conditions has been satisfied for a predetermined period of time, wherein the one or more conditions at least includes the condition that the laser current detection circuit has detected that there has been the potential that the laser is emitting light at levels that exceed a first predetermined threshold; wherein the laser current detection circuit comprises the following: a monitor diode configured to measure the light emitted by the laser and provide a voltage that is dependent upon the light measured; a current source or sink configured to provide current through the laser; a voltage source; and a comparator; wherein the voltage source is configured to provide to the comparator a voltage approximating the voltage that the monitor diode should provide if the laser is emitting a normal light emission; and wherein the comparator is configured to detect when the voltage provided by the voltage source and the voltage provided by the monitor diode are such that there is the potential that the laser is emitting light at levels that exceed the first predetermined threshold.