CMOS image sensor with tunable dynamic range for catheter based endoluminal applications

A custom CMOS image sensor designed for catheter based visible and Near-Infra-Red (NIR) endoluminal applications is proposed. The sensor presents high dynamic range (HDR) capability in a controlled light environment, providing a user-programmable power responsivity curve. The fabricated chip is a monochrome imager including a 256 × 256 pixel array, a complete read-out channel, a series of DACs for internal references and digital blocks for chip control. The complete functionality of the chip is guaranteed through six signal pins, used for the I2C-like input interface and the differential analog output. Prototypes were produced using the AMS 0.35 μm OPTO technology. The imager was electrically and optically characterized. Characterization results show state-of-the-art performance in terms of pixel noise (PN <0.6% of the signal swing, worst case), fixed pattern noise (FPN <1.8% of the signal swing, worst case) and signal to noise ratio (SNR 46 dB, worst case), both in the visible and NIR at 850 nm. HDR was characterized till 83.8 dB, limited only by the characterization setup and the chip specific configuration, capability for higher dynamic range has been demonstrated by image acquisition and processing. The chip dimension, the imager noise, and dynamic performance make it suitable for use in endoluminal applications both in the visible and NIR regions.