CMOS takes off

Technology Advances

From digital cameras to new SUVs, imaging sensors are everywhere.

Complementary metal oxide semiconductor (CMOS), the seeing eye dog of the digital age, may be set to revolutionize automobile safety. That's the view of Nicole Wagner, a research analyst with marting consultant Frost & Sullivan.

"The overall development of CMOS image sensors in the automotive industry," she wrote in a study, "can increase the safety of all motor vehides and especially the sport utility vehicle."

CMOS sensors are arrays of pixels that detect light and convert it to electrical voltages that vary according to the intensity of the light. The pixels have x, y addresses, and images of what the sensor "sees" are prepared by polling the pixels and measuring the voltage at each location. The sensor then compares the image with reference images and sends the result of the comparison to a logic circuit. The technology had been under development for several decades, then took a giant leap forward in the mid-'90s, when a group of engineers at NASA's Jet Propulsion Laboratory developed methods for using CMOS to garner near-scientific-quality images. Because CMOS sensors are less expensive and easier to produce than their predecessors, charge-coupled device (CCD) sensors, they're suddenly showing up everywhere: from consumer electronics such as the growing market for digital cameras to bigticket items such as automobiles to production lines.

The digital cameras of five years ago, for instance, relied on CCD technology and typically cost $1,000 or more. Those cameras have great resolution, terrific sensitivity, and short battery life. With the introduction of inexpensive CMOS sensors, digital cameras are accessible to the masses. They aren't as sensitive as the first generation of digital cameras and don't have the same resolution, but they can be purchased for $50, the batteries are long lived, and they're fine for shooting baby pictures that are going to be posted on the family Web page.

CMOS is good for more than building really cool toys, though. Used in automobiles, it might solve a lot of nagging safety problems. Already, automobile companies are using it to design smart airbags that do the following:

Recognize the difference between an event that truly requires deployment (e.g., a head-on collision) and a minor one (going over a curb)

Assess the size of the opposing passenger and deploy accordingly

Minimize early and late deployments

Auto companies are also experimenting with CMOS-enhanced mirrors, hoping to eliminate blind spots. Similarly, they are researching development of collision avoidance systems. If a driver tailgates, for instance, failing to observe the old "one car length per 10 miles per hour" separation rule, Mr. Zippy might find his car automatically slowing down. He might find his headlights subtly adjusting, too, to avoid shining in the rearview mirror of the driver in front of him or directly into the eyes of an oncoming driver.

CMOS is entering medicine and industry, too. The sensor has uses in endoscopy, dental cameras, veterinary endoscopes, industrial cameras, wireless videophones, and telemedicine.

Copyright Instrument Society of America Mar 2001