An event-detection high dynamic range CMOS image sensor

A novel CMOS image sensor is proposed to overcome the analog design limitations in Active Pixel Sensors - APS and large area overcome in Digital Pixel Sensors - DPS for use in bio-medical applications. The design includes a pixel level event generation mechanism by using a binary search technique. A ramp voltage generated by a combined block of 10-bit counter and DAC Digital to Analog Converter is compared with the pixel integrated voltage at each clock cycle at the same time allowing a fixed exposure time interval. The proposed design arrives to a total pixel array area of 1505.62μm × 4566μm for a pixel array size of 160(Zf) × 120(V). The photo-active area in each pixel is considered as the N-well area in a p002B;/n-well/p-sub type photo-transistor corresponding to a size of 11.24μm × 10.76μm. The overall pixel array reaches a fill factor of %34

Empowering Low-Cost CMOS Cameras by Image Processing to Reach Comparable Results with Costly CCDs

Despite the huge research effort to improve the performance of the complementary metal oxide semiconductor (CMOS) image sensors, charge-coupled devices (CCDs) still dominate the cell biology-related conventional fluorescence microscopic imaging market where low or ultra-low noise imaging is required. A detailed comparison of the sensor specifications and performance is usually not provided by the manufacturers which leads the end users not to go out of the habitude and choose a CCD camera instead of a CMOS one. However, depending on the application, CMOS cameras, when empowered by image processing algorithms, can become cost-efficient solutions for conventional fluorescence microscopy. In this paper, we introduce an application-based comparative study between the default CCD camera of an inverted microscope (Nikon Ti-S Eclipse) and a custom-designed CMOS camera and apply efficient image processing algorithms to improve the performance of CMOS cameras. Quantum micro-bead samples (emitting fluorescence light at different intensity levels), breast cancer diagnostic tissue cell samples, and Caco-2 cell samples are imaged by both CMOS and CCD cameras. The results are provided to show the reliability of CMOS camera processed images and finally to be of assistance when scientists select their cameras for desired applications

Design and Implementation of CMOS Image Sensors for Biomedical Applications

Since the first introduction of digital cameras, the camera market has been taking tremendous interest from many fields. This trend has even accelerated when the cost, size, and power consumption of such devices were reduced with the introduction of camera on a chip concept. This concept is achieved by integrating photoactive and electronics parts of digital cameras on a single chip with Complementary Metal Oxide Semiconductor (CMOS) technology but resulted in reduced photon collection efficiency and increased noise. Since then, scientists and researchers have been putting a huge effort to improve the quality of CMOS image sensors with advancements in lithography and fabrication process, by finding alternative ways of increasing the fill factor, designing lower noise circuits, and putting additional on chip features. Despite these efforts and cost, integration, and power consumption advantages of CMOS image sensors, they have still not been preferred in many application fields such as biomedical imaging, where high quality imaging is targeted. Recently, with the process related technological advancements, the cost of CMOS image sensors have increased and this has made the CMOS image sensors loose their cost advantage and attractiveness for low cost applications. In this thesis, I summarize my research effort in integrating the low-cost CMOS image sensors in biomedical applications and improving their performance with novel circuits fabricated with standard CMOS process, while maintaining their cost advantage. Towards this aim, I propose possible ways of implementing pixel array sensors and noise reduction and read-out related circuits with standard CMOS technology in order to make these low-cost sensors applicable for biomedical applications. For this purpose, this research started by fabricating a characterization chip that uses standard CMOS process compatible photodiodes and pixels. Using this chip, I obtained characterization data for an n-well 0.18μm standard CMOS technology and made it available for designers using similar technologies. Later, I developed a small camera prototype by using the characterization data of the first chip. This small camera chip includes efficient pixel circuits with column parallel fully differential noise reduction circuits, and horizontal and vertical access circuits. After obtaining good quality images using this camera prototype, I designed a larger array camera chip, which offers Video Graphics Array (VGA) resolution, using the same technology. This third camera chip uses pixel sharing technique, which results in 1.75 transistors per pixel. Moreover, this design provides the flexibility of changing the pixel array resolution with respect to the pixel size, aiming to optimize the performance according to the application. In order to result in highest possible fill factor, all of these fabricated chips use Active Pixel Sensor (APS) technique. Within the scope of this thesis, I also propose novel Digital Pixel Sensor (DPS) designs, which would bring chip-level additional functions for biomedical imaging applications and hold the potential for future devices

A novel cmos image sensor with event/change detection and reduced data redundancy

A Digital Pixel Sensor (DPS) based CMOS camera configured to record frames and comprising an event detection sensor configured to look for an event happening in a determined frame, comprising an array of event detection pixels, a first reference voltage generator, first row and column arbiters, and first row and column address encoders; the DPS based CMOS camera further comprises a change detection sensor configured to look for a change happening in between frames, comprising an array of change detection pixels, a second binary search value generator, second row and column arbiters, and second row and column address encoders