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22 REIMAGINING WHAT'S NEXT Alternatively, 360-degree image acquisition enables machine vision systems to capture more information about a given subject using a single camera in a fixed position. This can save the cost and complexity of a multi-camera inspection system and associated image processing and storage subsystems, which can also cause system performance limitations. Otherwise, a mechanism may be needed to reposition or rotate the camera or the object to be inspected, in applications such as food packaging inspection or aerial surveying, which similarly adds to the overall expense and complexity of the system. In a system requiring all-round inspection of objects, such as labels applied to bottles in a packaging plant, 360-degree vision can be achieved using a hyper- centric or peri-centric lens, positioned directly above the object itself. A hyper-centric lens captures rays of light as if they have originated from a single point located a certain distance in front of the lens. This convergence point and the perimeter of the lens define a viewing cone. Positioning the object within this viewing cone, directly beneath the downward-facing lens, allows light from the top surface and vertical sides of the object to enter the lens simultaneously. Focusing the light on the sensor allows the entire image to be captured in a single frame. Similar principles mean that cameras can capture a 360-degree view inside a hole or cavity, thereby eliminating any need to insert an optical probe. Other techniques to capture multiple images of an object in a single frame combine the hyper-centric lens with an array of mirrors that effectively see each side of the object simultaneously. Sensors – Physics and Fabrication Increasing the resolution of CMOS image sensors is key to capturing more finely detailed images, although simply reducing the pixel size can result in poorer image quality due to a lower signal-to-noise ratio (SNR). Achieving superior resolution calls for technical advancements to reduce pixel size without detracting from sensor performance. These can be achieved in a number of areas, such as optimizing the pixel pitch and the ratio of light-sensitive area to total area (also called the pixel fill factor). More fundamental changes to pixel physics can improve parameters such as the gain, efficiency and dynamic range. Sensor manufacturers have also improved the technologies for reading data from pixels, achieving enhancements like greater SNR, frame rate and linearity. Among the most important trends driving sensor performance over the last decade or so is use of back-side illuminated (BSI) sensors. These absorb light through upper and lower surfaces, enabling pixel miniaturization without degrading key performance parameters (like well capacity, quantum efficiency, dark current, etc.). This has been followed in more recent times by three-dimensional (3D) stacking of sensor and image processing dies to achieve smaller form factors. Subsequently, 3D hybrid stacking, which involves bonding of both silicon-oxide and metal pads, eliminates through-silicon vias (TSVs) in favor of more efficient direct connections between the two chips. Most recently, sequential integration has been developed, which enables fabrication of monolithic image sensors that each combine a phototransistor array with 3D stackable pixel-readout logic and memory, connected using integrated high-density I/Os. Global Shutter Enhances Imaging on the Move In high-speed industrial automation, as well as automotive and drone applications, there is a need to capture clear and sharp images of fast-moving objects. This challenges the performance of traditional rolling- shutter image sensors, which read image data from the sensor pixels into the frame buffer one line at a time. If the object is moving, the change in position during the time between reading the image from one line and reading the next can cause distortion such as blurring or bending of the image. "In high-speed industrial automation, as well as automotive and drone applications, there is a need to capture clear and sharp images of fast-moving objects."