CMOS active image sensors with on-chip analog-to-digital conversion

The integration of on-chip circuitry with a visible image sensor to simplify system interfaces and reduce system mass is investigated. The primary research interest is the development of a fully CMOS-compatible active pixel image sensor technology that allows a high level of electronics integration on the focal-plane for both driving the image sensor and performing on-chip signal processing operations. The second effort is a demonstration of these features through the integration of an analog-to-digital converter (ADC) with a CMOS active pixel image sensor and the development of ADCs for focal-plane applications. All the designs are fabricated using commercial CMOS processes.; The CMOS active pixel image sensors use intra-pixel charge transfer and readout transistors within each pixel to allow random access and fast readout rates. Both floating diffusion sensing for improved output sensitivity and floating gate sensing for non-destructive readout are presented. Correlated-double-sampling is incorporated into the readout structure to eliminate kTC noise and fixed pattern noise from the pixel. Image sensor arrays as large as 128 x 128 pixels operating at a frame rate of 70 Hz are demonstrated. Both off-chip and on-chip methods to reduce fixed pattern noise to below 0.1% of saturation are presented. The design and testing of 28 x 28 pixel test circuits optimized for reduced crosstalk between pixels, integration with microlenses, improved blue response and single-poly implementation as well as a photodiode pixel are reported.; Integration of on-chip circuitry with a CMOS active pixel image sensor is demonstrated through focal-plane analog-to-digital conversion. An array of single-slope analog-to-digital converters is integrated with a CMOS APS array to provide 8-bit digital output at video rate. Two methods of analog-to-digital conversion based on oversampled sigma-delta modulation are also investigated. The first method uses analog-to-digital conversion based on first-order sigma-delta modulation. Resolution of 10-bits is achieved although the conversion rate is limited to 270 conversions/s per converter. The second method of analog-to-digital conversion uses incremental second-order sigma-delta modulation. Based on simulations and experimental results of the first-order design, the projected performance of this design is 10-bit resolution at a conversion rate of almost 3000 conversions/s per converter.; An inherently CMOS-compatible active pixel image sensor and on-chip analog-to-digital conversion is successfully demonstrated in this dissertation. This work paves the way for the development of larger format arrays, smaller pixel designs and the integration of more sophisticated signal processing operations on the focal-plane.