Multi-resolution CMOS image sensor

It is required to capture the image of fast moving objects without distortion in many applications such as surveillance systems, traffic cameras, robotic visions, destruction testing and scientific experiments. One of the problems in the imaging the fast moving objects is motion-blur since the trace of the moving objects is integrated in a frame. To get a sharp image without any motion-blur, the high-speed imaging with a short integration time is indispensable. Consequently, this requires high-speed readout at the cost of high bandwidth. However, high frame-rate images with high spatial resolution entail large bandwidth and also large power consumption.

In order to reduce the bandwidth and power consumption, we proposed a CMOS image sensor which simultaneously generates spatial-temporal multi-resolution images from dual channels: one for normal images (<30 fps) for stationery backgrounds and the other for high frame rate images (adaptable over 960 fps) with a reduced spatial resolution for moving objects in the region-of-interest (ROI) [1,2]. Therefore, the entire image with the details in stationery objects and the suppressed motion-blur in moving objects can be acquired at low power consumption with optimal use of bandwidth. To provide the real-time decision of ROI, this sensor employs on-chip motion detection circuits based on the inter-pixel switch operation by storing the previous frame signal in a floating node. This allows a small pixel implementation without adding any extra in-pixel memory components. A prototype chip has been implemented using a 0.35 ?m 1P4M standard CMOS process and multi-resolution images have been successfully captured without motion blur. The fabricated chip operates at 3.3 V and consumes 75 mW in the multi-resolution readout of a 256 ? 256 normal image at 30 fps and a 64 ? 64 ROI image at 240 fps.

Related Publication
  1. J. Choi, S. -W. Han, S. -J. Kim, S. -I. Chang, and E. Yoon, " A Spatial-temporal Multi-resolution CMOS Image Sensor with Adaptive Frame Rates for Moving Objects in Region-of-Interest," Technical Digest of International Solid-State Circuits Conference, pp.502-503. Feb. 2007.
  2. J. Choi, S. -W. Han, S. -J. Kim, S. -I. Chang, and E. Yoon, "A Spatial-Temporal Multiresolution CMOS Image Sensor With Adaptive Frame Rates for Tracking the Moving Objects in Region-of-Interest and Suppressing Motion Blur," IEEE J. Solid-State Circuits, Vol. 42, No. 12, pp. 2978-2989, Dec. 2007.