Super-sensitive switches etched in silicon? This is not your father's solid state.
Sharp, vibrant, incredibly detailed: The pictures produced by Foveon's X3 image sensor chip are seductive evidence that pixels will displace film. The Sigma SD9 - the first commercial camera to use Foveon's technology - captures three times more color per pixel than standard digital shooters. But here's the thing: This isn't digital technology. It's a twist on old-fashioned analog electronics - an array of millions of light filters and detectors etched in silicon.
Weird as it sounds, the road to smaller, cheaper, more energy-efficient consumer electronics may be paved with analog technology. These circuits are built from the same components as their digital counterparts but suck 90 percent less battery power. The difference? In an analog device, each transistor acts like a dial, with a wide range of readings that depend on the sinuous fluctuation of voltage, current, amplitude, and frequency. Digital circuits, on the other hand, use the same transistors as simple on-off toggle switches. Analog transistors capture far more information, so you need fewer of them.
Advances in the digital realm are powering the technology. Tiny analog circuits, sensors, and even radios can be manufactured using the same fabrication techniques - microscopic etching on semiconductor wafers - that have kept Moore's law chugging along. Devices with analog chips in their guts will begin landing in consumers' hands this year in the form of high resolution cameras and mobile phones that can go a week without recharging.
Much of the new analog circuitry creeping into consumer gadgets springs from the research of Carver Mead, Foveon's founder and chair. As a Caltech professor (now emeritus) in the 1970s, Mead sought to imitate the analog elegance of the human brain. In 1986, Mead cofounded a company, Synaptics, to build high-performance analog computers. He understood that solid state circuitry would be ideal for connecting computers to the real world of light, touch, and sound, which are analog by nature. Synaptics eventually focused on the tactile, becoming the leader in laptop touchpads. (It controls about 80 percent of that market.)
Next came Foveon, founded in 1997. Its X3 image sensor chip is perhaps the most impressive analog electronics application so far. Standard digital cameras use filters that permit light sensors to capture only one primary color per pixel. From there, a signal processor runs algorithms that approximate the missing colors by sampling nearby pixels. That guessing game introduces telltale lines and whorls into the final picture. Foveon found a way to use standard silicon as an analog color separator. One of the optical properties of silicon is that different wavelengths of light penetrate it to different depths. This allows Foveon chips to stack red, green, and blue sensors at every pixel.
Impinj, another Mead startup, hopes to conquer sound with a technology that lets digital logic fine-tune a cell phone's analog transmitter midcall, so the overall circuit can be smaller. Impinj claims the design draws one-tenth the power of its two-part predecessors. It also puts out a more efficient signal, allowing phone networks to carry greater call volume. It costs less, too.
For Foveon chief scientist Dick Lyon, who toiled for decades in the shadow of the Digital Revolution, there's a sweet payback to sculpting analog parts from silicon: "If you do it right, you can make transistors and create devices no one imagined."
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