An Energy/Illumination-Adaptive CMOS Image Sensor With Reconfigurable Modes of Operations

We present an energy/illumination-adaptive CMOS image sensor for distributed wireless sensor applications. The adaptive feature enables always-on imaging operation with extremely low power consumption for extended lifetime of wireless image sensor nodes and provides optimum images in a wide range of illuminations. For adaptive operation, the sensor employs reconfigurable modes of operation. Most of time, the sensor is in a monitoring mode, which keeps imaging at extremely low power consumption. The sensor turns into a high-sensitivity imaging mode or a wide dynamic range imaging mode when illumination varies and sufficient power supply is available from energy harvesting. The sensor changes its operation back to the monitoring mode in order to save energy in the battery. The sensor operates at 1.36 μW/frame in the monitoring mode from harvested energy and provides high-sensitive (24 V/lx·sec) and wide dynamic range images (99.2 dB) at 867 μW in battery operation. The chip achieved power FOM of 15.4 pW/pixel·frame in 0.18 μm technology.