Samsung has introduced a new pixel technology for CMOS image sensors called ISOCELL. The company claims this new tech can produce higher color fidelity in poor lighting conditions by increasing light sensitivity and controlling the absorption of electrons. The first image sensor to adopt this tech will be the S5K4H5YB 8MP imager going into mass production by the end of the year.
Naturally, the quality of an image sensor is determined by the amount of light that is accurately captured by the individual pixels within the sensor array. However, smartphones need to stay within a specific form factor size, so they can't have physically large image sensors. Thus in order to increase the resolution and image quality, camera sensor providers have been locked into shrinking pixels instead of making sensors bigger while improving performance at the same time.
"To meet this challenge, previous sensor technology developments focused on improving the light absorption of each pixel, and have progressed pixel technology from FSI (Front Side Illumination) to BSI (Back Side Illumination) which places photodiode at the top to maximize photoelectric efficiency," Samsung explains. "While being very effective at the time, this BSI technology also faced limitations in improving image quality as pixel sizes continued to decrease."
Enter Samsung's next-generation pixel technology, the patent-pending ISOCELL. This tech actually forms a physical barrier around each pixel so that more photons can be collected from the micro-lens and absorbed into the correct pixel's photodiode. This pixel isolation will minimize electrical crosstalk between the pixels and allow expanded full well capacity (FWC), or the amount of charge an individual pixel can hold before saturating.
Samsung claims that when compared to conventional BSI pixels, ISOCELL pixels decrease the crosstalk by around 30 percent for a higher color fidelity, and increases the FWC by 30 percent, leading to a greater dynamic range. Even more, an image sensor using the tech can feature a 20 percent wider chief ray angle, thus reducing the actual camera module's height. This is ideal for form factors with "challenging" low z-height requirements.
"Through advances in pixel and process technology, smartphone and tablet cameras have made it easier than ever for consumers to capture and share beautiful, clear images with the world," said Taehoon Kim, vice president of System LSI marketing, Samsung Electronics. "ISOCELL technology is yet another innovation that significantly raises the bar in image quality, and demonstrates Samsung's technology leadership in image sensors for mobile devices."
Samsung's S5K4H5YB 8MP imager is currently being sampled to customers, and will go into mass production in 4Q 2013. This imager utilizes a 1.12um ISOCELL pixel, and has a 1/4 inch optical format.