We realized an ultimately advanced imaging system that comprises a hemi-spherically curved, back-illuminated CMOS image sensor (BIS) and integrated lens which doubles the sensitivity at the edge of the image circle and increases the sensitivity at the center of the image circle by a factor of 1.4 with one-fifth lower dark current (J_d) than that of a planar BIS. Because the lens field curvature aberration (A_<fc>) was overcome in principle by the curved sensor itself, the curved BIS enables higher system sensitivity through design of a brighter lens with a smaller F number (Fn) than is possible with a planar BIS. At the same time, we controlled the tensile stress of the BIS chip to produce a curved shape that widens the energy band-gap (E_g) to obtain a lower J_d.
For applications of IoT, we are developing pulse-width-modulation pixels based on 4T-APS with a capacitor that controls the FD voltage and a cascoded source-common in-pixel amplifier to achieve high sensitivity and low noise as well as low voltage and low power consumption. Because a change of FD voltage is read out as a pulse width, the power supply voltage of the pixel readout circuit can be reduced to around 1V. Further more, as most of the column circuits are embodied as digital circuits, the power supply voltage can be lowered significantly to achieve low power operation. In this report, a stack structure and a 2-stage ADC are discussed.
A 5.0G-pixel/s readout circuit for 15.3mm×8.6mm optical size, 3.7M-pixel, 1300 fps, and digital output image sensor is presented. To achieve 5.0G-pixel/s readout rate, the high speed column readout circuit is introduced. The novel pixel readout, A/D conversion, and digital data transfer schemes are introduced to realize the readout rate and to reduce the interference noise. The 1 horizontal (1H) readout time is realized to be 1.0μs.
A CMOS image sensor for 3D range map acquisition based on both Time-of-Flight (ToF) and Light-Section method is presented. A pixel of the presented sensor is consisted of two pairs of Lock-In pixel which share one of floating diffusions. In ToF mode, the sensor can obtain range information by single accumulation and readout using three outputs. In Light-Section mode, the sensor offers fast and high accurate detection of the sheet light by a single-slope ADC and a priority encoder. In simulation, the accuracy in ToF mode has been estimated as 3mm-7cm (@50-200cm, 60 fps) and resolution of the sheet light position detection has been estimated as 0.16 of pixel width.
Plane of sharp focus (POF) and borders of depth of focus (DOF) are arranged parallel with an image sensor using a normal optics. This arrangement has large constraints for applications of depth estimation. Therefore, since we adopt tilted optics which can arrange angle of the POF and the borders of the DOF, we have developed a depth estimation method using the POF and the borders of the DOF which are optimized for various application.
Digital ELISA (enzyme linked immunosorbent assay) is a technique to detect fluorescence originated from a single molecule and realize concentration measurement with ultra-high sensitivity. In this study, we developed a lensless CMOS imaging device for a miniaturized digital ELISA system. By using a fabricated device, we demonstrated an enzyme assay based on fluorescence imaging.