Overview
Eric R. Fossum (born 1957) invented the CMOS active-pixel sensor with intra-pixel charge transfer at NASA's Jet Propulsion Laboratory in the early 1990s, seeking to miniaturise cameras for spacecraft. It can be manufactured in standard CMOS processes alongside its own processing circuitry, and it is the sensor in essentially every smartphone.
What You Need
- Born 1957, United States
- Anchor year: 1993 — the CMOS active-pixel sensor
- Strand: overlooked — billions of units, no public profile
Steps
The problem as it stood
CCDs produce excellent images and need specialised fabrication, multiple supply voltages, substantial power, and separate chips for processing. For a spacecraft — or later a phone — that is size, weight, power and cost in all the wrong places.
What he actually did
Fossum's team put an amplifier in every pixel and used intra-pixel charge transfer to a sense node, giving each pixel its own active readout while retaining the low noise that earlier passive CMOS sensors lacked. The result is manufacturable in a standard CMOS process.
How it worked
A CCD marches charge across the whole array to one amplifier. An active-pixel sensor amplifies at each pixel and reads them by address, like memory. That means no transfer losses, low power, random access, very fast readout, and — decisively — the ability to put the sensor and its processing on the same die in an ordinary fab.
What it made possible
Cameras cheap and small enough to put in everything. Smartphones, webcams, cars, doorbells, endoscopes. Almost all video now produced in the world — including most of what is watched through the delivery chain in the previous wave — originates on one of these.
What happened to him
He commercialised the technology through Photobit, later acquired by Micron, and became a professor at Dartmouth. He received the Queen Elizabeth Prize for Engineering in 2017 with Boyle, Smith and Tompsett — an award that credited all four.
Where the credit landed
Fossum is well credited within the field and unknown outside it, despite his invention shipping in billions of units annually. The Queen Elizabeth Prize is notable for doing what the Nobel did not: crediting the imaging lineage collectively, across Boyle, Smith, Tompsett and Fossum, rather than selecting two names from it.
Pro Tips
- An amplifier in every pixel means no transfer losses and random access.
- Standard CMOS fabrication means sensor and processing share a die.
- The Queen Elizabeth Prize credited all four CCD/CMOS figures — the Nobel credited two.
Knowledge Base
What You'll Learn
The last link in capture: a camera cheap enough to put in everything.
Rolling shutter, and where it comes from
Because a CMOS sensor is read out row by row rather than all at once, different rows are exposed at slightly different times. Fast horizontal motion therefore appears skewed, and a propeller can look bent — the rolling shutter effect. Global shutter designs avoid it at the cost of complexity and pixel area. It is a direct visible consequence of the readout architecture that made these sensors cheap.
Where This Fits
This guide covers one specific part of the history of media technology. The wider picture — how each link in the chain from capture through transmission to display was actually built, who built it, and why the credit so often landed somewhere else — is in A History of Broadcast Technology: The Chain From Capture to Screen, which frames the discipline as a whole and links out to the detailed guides underneath it, including this one. If you are starting from scratch rather than solving a specific problem, read that first and come back here.
FAQ
Q: What is a CMOS active-pixel sensor?
A: An image sensor with an amplifier in each pixel, read by address rather than by shifting charge across the array. It can be made in standard CMOS processes alongside its own processing circuitry, making it small, cheap and low-power.
Q: Why do phone videos sometimes look skewed?
A: Rolling shutter. CMOS sensors are read row by row, so rows are exposed at slightly different times and fast motion appears distorted.