Pulsed Illumination Synchronization for Global Reset Rolling Shutter Imagers
Global Reset rolling shutter imagers eliminate motion blur when pulsed light fires strictly within the dark global integration window under controlled ambient light.
Responsivity
Conversion Efficiency
The ratio of the generated electrical signal to the incident optical power striking a photodetector defines the sensitivity of the sensor at a specific wavelength of light. This parameter, known as responsivity, is typically expressed in amperes per watt for current-output devices or volts per watt for voltage-output devices. It is a fundamental metric used to evaluate and compare the efficiency of light-to-charge conversion in optical systems.
High values of this metric indicate a more efficient detector that can resolve weaker optical signals.
Spectral Variation
Semiconductor physics dictates that this conversion efficiency varies across the light spectrum. The responsivity of silicon detectors peaks in the near-infrared region and drops rapidly in both the ultraviolet and longer infrared bands. This wavelength dependence is governed by the absorption coefficient of the semiconductor material.
Engineers must use spectral response curves to calculate the correct output current for broadband light sources.
Measurement Drift
Thermal stability of the detector affects this conversion ratio during continuous operation. As temperature rises, the bandgap of the semiconductor shifts, which alters the responsivity at longer wavelengths. This thermal drift can lead to measurement errors if the sensor temperature is not stabilized or compensated.
High-precision optical power meters utilize active temperature monitoring to maintain accuracy in varying environments.
Calibration Standard
Metrological verification requires comparing the detector against a certified reference photodiode. This calibration uses a stabilized light source and a monochromator. The resulting certificate lists the responsivity values at specified wavelengths.
These figures are programmed into the instrument to ensure accurate measurements.