期刊
IEEE JOURNAL OF SOLID-STATE CIRCUITS
卷 44, 期 10, 页码 2834-2843出版社
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
DOI: 10.1109/JSSC.2009.2027929
关键词
Activity-triggered detection; CMOS imaging sensor; difference image; digital calibration; high linearity; wide dynamic range
资金
- Research Grant Council of the Hong Kong Special Administrative Region Government [RGC DAG06/07.EG04]
Imaging sensors are being used as data acquisition systems in new biomedical applications. These applications require wide dynamic range (WDR), high linearity and high signal-to-noise ratio (SNR), which cannot be met simultaneously by existing CMOS imaging sensors. This paper introduces a new activity-triggered WDR CMOS imaging sensor with very low distortion. The new WDR pixel includes self-resetting circuits to partially quantize the photocurrent in the pixel. The pixel residual analog voltage is further quantized by a low-resolution column-wise ADC. The ADC code and the partially quantized pixel codes are processed by column-wise digital circuits to form WDR images. Calibration circuits are included in the pixel to improve the pixel linearity by a digital calibration method, which requires low calibration overhead. Current-mode difference circuits are included in the pixel to detect activities within the scene so that the imaging sensor captures high quality images only for scenes with intense activity. A proof-of-concept 32 x 32 imaging sensor is fabricated in a 0.35 mu m CMOS process. The fill factor of the new pixel is 27%. Silicon measurements show that the new imaging sensor can achieve 95.3 dB dynamic range with low distortion of -75.6 after calibration. The maximum SNR of the sensor is 74.5 dB. The imaging sensor runs at frame rate up to 15 Hz.
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