Samsung revealed its innovative ISOCELL image sensor technology in September last year, but it has taken until now for the concept to be applied in a device. The Galaxy S5, which was announced at the Mobile World Congress, is the first smartphone from the Korean manufacturer that comes with an ISOCELL camera. Samsung has taken this occasion to publish a video that explains the technology in more detail.
According to Samsung, the ISOCELL sensor design achieves better image quality than is normally possible from the very small CMOS sensors used in smartphones and tablets. ISOCELL uses a backside-illuminated (BSI) photodiode that is unique compared to past designs thanks to its integrated barriers between the individual pixels. Compared to conventional BSI sensors, this reduces electrical crosstalk by about 30 percent. Crosstalk - the bleeding of photons and photoelectrons between neighboring pixels - has been a disadvantage of traditional BSI sensor design, one that can reduce image sharpness and color accuracy because light intended for one particular pixel spreads to its neighbors.
Existing BSI designs, with their photodiodes near the front of the sensor, lack any inherent structures that prevent light bleeding between pixels (a role fortuitously played by the circuitry in front of the photodiodes in older, frontside-illuminated chips). The barriers in the ISOCELL design prevent this bleeding.
An additional advantage of the ISOCELL's barriers is that overall photodiode size can be increased, which can lead to lower levels of noise and better dynamic range due to the increase in full-well capacities of each pixel.
Increasing the size of the photodiodes allows the pixels to receive light from more awkward angles (something described as a 20% wider chief ray angle). This means a lens can be mounted closer to the sensor, potentially reducing the height of the camera module and making it more suitable for the slim bodies of mobile devices.
ISOCELL is trying to address a particular problem for very small pixels. So for now it is most applicable to smartphone camera technology, but as pixel density increases on larger sensors, we might well see it on enthusiast compact cameras at some point in the future. We are looking forward to testing the technology in the Galaxy S5. For now, you can watch the video below for a visual explanation of the concept.