Samsung Tech Blog about ISOCELL Color, HDR and ToF Imaging
The science of creating pixels has made substantial progress in recent years. As a rule, high resolution image sensors need small, light-sensitive pixels. To capture as much light as possible, the pixel structure has evolved from front-side illumination (FSI) to a back-side illumination (BSI). This places the photodiode layer on top of the metal line, rather than below it. By locating the photodiode closer to the light source, each pixel is able to capture more light. The downside of this structure is that it creates higher crosstalk between the pixels, leading to color contamination.
“To remedy such a drawback, Samsung introduced ISOCELL, its first technology that isolates pixels from each other by adding barriers. The name ISOCELL is a compound word from the words “isolate’ and ‘cell,’” Kim explained. “By isolating each pixel, ISOCELL can increase a pixel’s full well capacity to hold more light and reduce crosstalk from one pixel to another.”
With ISOCELL technology, ISOCELL image sensors have very high full well capacity. Pixels in the newest ISOCELL image sensor have up to 70,000 electrons, allowing the sensor to reach huge signal range. … “To reduce noise, we perform two readouts: One with high gain to show the dark details and another with low gain to show the bright details. The two readouts are then merged in the sensor. Each read out has 10-bits. With the high conversion gain readout at 4x, it adds an additional 2-bits, producing 12-bit HDR image output. This technology is called Smart-ISO Pro also known as iDCG (intra-scene Dual Conversion Gain).”
Samsung has a plan to release a new generation of iToF sensor that has an image signal processor (ISP) integrated. The whole processing of depth information is done on the ISP within the sensor, rather than delegating to the SoC, so that the overall operation uses lower power consumption. In addition, the new solution offers improved depth quality even in scenarios such as low light environment, narrow objects or repetitive patterns. For future applications, Samsung’s ISP integrated ToF will help provide high quality depth image with little to no motion blur or lagging, at a high frame rate.