Technology

Machine vision sensors and high speed imagers require global shutters to capture the data of all pixels at the same moment in time. Consumer CMOS sensors feature rolling shutters, which create motion artefacts when the scene is moving. Cmosis' pipelined global shutter pixel allows to capture the next frame during readout. Each pixel features a storage node, to which the signal is transferred after the image capture. This storage node has an extremely low parasitic light sensitivity, which is essential for most imaging applications. This pixel can be read out with low noise and with a high dynamic range.

Capturing data at high frame rates is one thing, the data has also to be read out and digitized. For that purpose, Cmosis developed fast AD converters which are located in the columns. The circuits can be optimized for high speed or high bit counts.

Large area image sensors, with dimensions up to wafer scale, have been reported for several years in the scientific and commercial literature. Economically, the use of such sensors has been very limited because of low production yields. Every wafer contains defects which result in most cases to a failing sensor. These killer defects are hard to avoid, the sensor has to tolerate them. We patented a new methodology to drastically reduce the sensitivity of CMOS image sensor pixels to defects occurring on a wafer. This allows to make these large devices also on an economic scale. Applications can be found in medical X-ray equipment, large and medium size photography, and scientific instrumentation.

Technologies have been developed in the past to increase fill factor. However, for the large pixels that are often used in professional imaging applications, there was a trade-off with pixel cross-talk. We patented a new technology to keep a high fill factor whilst reducing the cross-talk between pixels. The technology can also be applied in combination with charge transfer pixels. Prototypes are under development. Another advantage that it will also improve the sharpness of back-side illuminated image sensors. Applications can be found in high speed image sensors, backside illuminated image sensors, and sensors for machine vision or security applications.

Charge binning is traditionally a privilege of CCD devices. In CMOS Image sensors, it is usually replaced by sub-sampling which creates severe Moiré patterns, or averaging of the signals of different pixels which requires a lot of data handling. We invented a new method that allows to add charges of pixels from the pixel array. It can be used for a low-resolution preview image, or for high speed light metering purposes.

Time Delayed Integration or TDI imaging is used to image moving objects. By synchronizing the pixels with the motion of the camera or the object, the effective exposure time can be increased. Implementations in CMOS have traditionally been difficult because of the lack of a charge addition circuit. The application requires the combination of a global shutter and a low-noise readout method. We found new ways to solve this problem. This will typically be applied in earth observation instruments, inspection systems and machine vision.