Eric Fossum, the inventor of the CMOS image sensor, the sensor in almost every modern digital camera, has teamed up with Jiaju Ma in developing the Quanta Image Sensor (QIS). The QIS represents a significant leap forward in low-light sensitivity that has major implications for both scientific imaging and consumer electronics. Fossum and Thayer note that the Quanta Image Sensor is fundamentally different from complementary metal oxide semiconductor (CMOS) and charge coupled device (CCD) sensors, the sensors that have dominated the image industry for years (with CMOS having largely replaced CCD). Whereas traditional sensors have tens of millions of photosites, the QIS aims to have a billion pixels on a sensor of the same size. What makes the pixels special, however, is their extreme sensitivity:
Light consists of photons, little bullets of light that activate our neurons and make us see light. The photons go into the semiconductor and break the chemical bonds between the silicon atoms and when they break a bond, an electron is released. Almost every photon that comes in makes one electron free inside the silicon crystal... We were able to build a new kind of pixel with a sensitivity so high we could see one electron above all the background noise. These new pixels are able to sense and count a single electron for the first time without resorting to extreme measures.
That's right: Fossum and Thayer have developed an image sensor that can work with single photons. The best part? They developed it with industry application in mind:
We deliberately wanted to invent it in a way that is almost completely compatible with today's CMOS image sensor technology so it's easy for industry to adopt it.
To put this into perspective, consider this: in typical low-light conditions, your camera is working with thousands of photons per pixel. This new sensor is working with single photons. This is literally the smallest amount of light possible. Fossum and Thayer note that in its current stage, it's a proof of concept and there are other issues to contend with, such as reading data from a billion pixels, but even so, this represents a promising step toward future advances.