Title :
On-focal-plane signal processing for current-mode active pixel sensors
Author :
Nakamura, Junichi ; Pain, Bedabrata ; Nomoto, Tetsuo ; Nakamura, Tsutomu ; Fossum, Eric R.
Author_Institution :
Olympus Opt. Co. Ltd., Tokyo, Japan
fDate :
10/1/1997 12:00:00 AM
Abstract :
On-focal-plane signal processing for current-mode active pixel sensors (APS), including fixed pattern noise (FPN) suppression and high-resolution analog-to-digital conversion (ADC), is presented. An FPN suppression circuit that removes the offset current variation between pixels by using a combination of an n-type and a p-type current copier cell is described. The FPN suppression circuit exhibits linear transfer characteristics in the input current range from 0 to 30 μA. On-chip ADC is expected to improve imaging system performance and reliability, while reducing system size, weight, and cost. Operation and performance of a current-mode second-order incremental Δ-Σ A/D converter with column parallel architecture and for high-resolution and medium-slow-speed applications is presented. A 12-bit resolution with ±1.5 LSB accuracy at the conversion rate of 5.6 kHz was obtained. The LSB corresponds to less than twelve signal charges of current-mode 10-μm pixel APS´s. Based on the experimental results, a brief description of a possible image sensor with the on-chip signal processing is also described
Keywords :
CMOS integrated circuits; analogue-digital conversion; focal planes; image processing equipment; image sensors; integrated circuit measurement; integrated circuit noise; integrated circuit reliability; interference suppression; optical information processing; 0 to 30 muA; 1000 pixel; 115 mW; 5.6 kHz; CMOS image sensor; charge modulation device; column parallel architecture; current-mode active pixel sensors; current-mode second-order incremental Δ-Σ A/D converter; fixed pattern noise suppression; high-resolution analog-to-digital conversion; image sensor; imaging system performance; input current range; linear transfer characteristics; medium-slow-speed applications; n-type current copier cell; offset current variation; on-focal-plane signal processing; p-type current copier cell; power dissipation; reliability; Active noise reduction; Analog-digital conversion; Circuit noise; Costs; High-resolution imaging; Parallel architectures; Sensor phenomena and characterization; Signal processing; System performance; System-on-a-chip;
Journal_Title :
Electron Devices, IEEE Transactions on
