Optical power or energy meters measure the power and/or energy from a light source, such as a laser. A typical optical meter utilizes a light sensor or detector that converts an optical signal into an electrical signal, such as a voltage signal. Typical detectors include pyroelectric detectors, which are based on the pyroelectric effect of ferro-electric crystals to produce a voltage output signal proportional to the optical energy incident on the detector, and thermopile detectors, which employ thermocouples to produce a voltage output signal proportional to the power in an optical signal incident on the detector.
Conventional optical meters measure the optical signal's attributes by directly observing the detector's output signal and extracting information from that output signal alone. For example, a pyroelectric detector's peak output voltage measured from the signal's baseline is proportional to the optical energy in a pulse incident upon the detector, provided the laser pulse width is small enough that it can be assumed to be an impulse. Circuitry can register that peak voltage and thereby provide a measure of the optical pulse energy. However, the dynamic response of the detector limits how quickly such measurements can be taken, especially when the optical signal incident upon the detector comprises a train of periodic pulses, as is typically the case. Present optical meters are thus limited to operate at pulse repetition rates less than about 2 kHz (2000 pulses per second) in most circumstances.
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