Development of vacuum compatible, multi-mode operation light source
Light sources are used extensively at various stages of development and characterization of an electro-optical (EO) payload like Cartosat, HySIS, Microsat etc. These sources are required to characterize many critical parameters of EO payload like photo response non uniformity (PRNU), noise performance, saturation radiance etc. Currently integrating sphere with quartz tungsten halogen (QTH) lamp is widely used for payload characterization. These lamp sources generally operate in continuous mode in clean room environment and thermo-vacuum. In case of high resolution payloads, time-delay and integration (TDI) detectors are used to improve signal collection. For characterization and testing of such payloads multi-mode (pulsed and continuous) light source (switching at kHz rate in synchronization with payload electronics) with specific spectral range is required. Pulse mode operation requirement cannot be met using QTH lamps. To cater to such need a LED based indigenous source has been developed. This paper delineates circuit design and implementation of driver and characteristics of the source is also discussed. Proposed source is capable to synchronize and operate in multi-mode with external clock pulse with high achieved linearity (>99%) and high stability (>99%) in vacuum condition.
Light source; LED; Constant current mode; Pulse mode; Continuous mode; Vacuum compatibility
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