Camera-phones take hold as digital imaging platform

By Junko Yoshida

EE Times
February 10, 2003 (3:34 p.m. EST)

PARIS "Smile, and look at the telephone!" This, in the hopeful outlook of U.S. and European makers of camera modules, will be 2003's trendiest new line, repeated at least 40 million times in a dozen languages.

The companies are counting on explosive growth for imaging-enabled mobile phones. But for that to happen this year, nagging issues of interoperability and roaming in wireless infrastructures must be overcome, and fundamental technology challenges must be met to enable a low-cost, low-power, high-resolution camera module small enough to fit in a flip phone.

Conexant Systems Inc. spin-off Pictos today will unveil what it calls the industry's smallest complete-CMOS VGA camera module, at 10 x 10 x 6.4 mm. Later this month, Agilent Technologies will roll out a line of complete-CMOS camera modules in VGA and CIF resolutions.

"Three years ago, it was a gamble [to get into the camera phone market]," said Philippe Quinio, who directs marketing and product strategy for STMicroelectronics' imaging division. "But today, it's a big-volume business with a huge reward."

Observers estimate the industry will ship twice as many camera phones worldwide this year as in 2002, with volume hitting 40 million units. Some vendors even put total shipments as high as 80 million units.

"When only 17 million to 20 million units of digital still cameras ship yearly," the latest camera phone phenomenon indicates that "the industry is at an inflection point," said Mike Walters, the mobile imaging program manager at Agilent. He predicted that in 2003, for the first time, "the most dominant and prevalent digital imaging platform will no longer be a still camera but a mobile phone."

If that's true, the implications are profound, because consumers will certainly want to "take bigger and better pictures on their camera phones," said Tony Henning, senior analyst at Future Image Wire, a Web-based information service focused on wireless imaging. Users want pictures to be printable, he said, and they look for more in-phone space to store more and bigger pictures.

That would pressure mobile-camera-phone design engineers to consider more suitable "lens, zoom and flash capabilities" for their handsets, said Neil Strother, senior analyst at In-Stat/MDR.

Strother said other design issues must consider the best way to store images, including whether to add memory to the phone, use some type of storage card, download to a PC or send to a Web site. Connectivity issues wireless via Bluetooth, USB On-The-Go, 802.11 or a wired solution such as USB 2.0 or both a wired and wireless option must also be resolved.

Resolution vs. size

To some degree, leading CMOS image-sensor companies, most of which also design a companion signal processor for image processing, have been trying to solve the conundrum of resolution vs. module size. "Higher resolution requires bigger pixel arrays, and yet the smaller pixel size is absolutely necessary to reduce the size of an [imaging] module," said Pictos CEO Kevin Strong.

Karl McGoldrick, general manager of Philips Semiconductors' imaging division, agreed. "Shrinking the imaging module is the most critical [challenge] of all for camera phone designs . . . and this needs a breakthrough."

Or perhaps several breakthroughs: "This requires a very much system-level solution," Agilent's Walters said.

Many in the industry agree improvements are required in three areas: proprietary process technologies, the circuitry around the imaging sensor, and lens design.

"More intelligence needs to be built into the image coprocessor to improve visible defects," ST's Quinio said. Those defects include dark-rimmed images, often the result of using a smaller lens, which may lose optical quality around the edges.

Curt Waters, worldwide business manager for cellular media in Texas Instruments' imaging and audio division, predicted that "as higher-resolution camera phones including a megapixel range emerge this year, more-sophisticated pre- and post-image processing will become necessary to solve the fundamental problems" of CMOS image sensors, which are prone to difficulties with pictures taken under low-light conditions. Though TI does not supply CMOS imaging sensors to mobile phones, the company's new business group is angling to provide "robust, application-specific image processors" for camera phones that may not be based on TI's Omap platform.

What's most important in resolving imaging module size vs. resolution is "a proprietary process technology that would allow a CMOS image sensor company to fabricate sensors with specific pixel designs and doping layers," said Pictos' Strong.

Pictos has made additional modifications to a semiconductor process owned by Jazz Semiconductor, Conexant's foundry spin-off, in terms of "positioning of micro lenses and metal layers," said Diwaker Sambyal, product manager at Pictos. The company's latest imaging sensor is fabricated by Jazz with 0.18-micron process metal layers on wafers using a 0.25-micron process geometry.

ST's Quinio noted that there "are a lot of Taiwanese companies who built their business by supplying CMOS image sensors for PC cameras but none of them has entered the camera phone market because most of them do not have their own process technology."

Integrated solution sought

To reduce the size of the imaging module, the industry also badly needs an integrated solution: a CMOS imaging sensor integrated with an image preprocessor. Philips Semiconductors is the first to succeed here, having integrated "at least the first stage of imaging signal processing" RGB to YUV conversion onto the sensor chip. While its competitors have tried to integrate a similar image processor onto an imaging sensor die, "they have often found it impossible to do so without degrading pictures, because the power dissipation of the image processor gets too high and affects the noise level of the whole sensor," said Philips' McGoldrick.

Pictos' Sambyal said that because side-by-side analog and digital designs may cause more noise, the company will keep a CMOS imaging sensor and an image processor separate for now, though encased in a single module. Pictos' imaging processor handles color-space conversion, brightness control, white-balance control and gamma correction; it can also perform 2-D bad-pixel correction and JPEG compression on the fly, without an external memory or DSP.

Agilent is working on a prototype product, scheduled to be ready by midyear, that integrates an image sensor and image processor on the same chip, said Agilent's Walters. In contrast, ST's current solution puts an imaging sensor on one chip and solders its coprocessor onto a main phone pc board with a low-electromagnetic-interference link, Quinio said.

Today, ST ships in volume both VGA and CIF modules, along with coprocessors. Its VGA module measures 11.76 x 9.56 x 8.4 mm, excluding the socket, the company said.

Both ST and Philips, early leaders in camera modules for mobile phones, claim a number of big design wins from top-tier mobile-phone companies. ST started shipping 100,000 modules per month as of December and is ramping up further, said Quinio. Reportedly, ST's camera modules are designed into Nokia's current camera phone model. Philips, meanwhile, said the top five global mobile handset manufacturers are using Philips' imaging solutions.

Pictos has one large design win for its new module, ready for announcement during the 3GSM Congress, and said half a dozen handset vendors will design it into their camera phones this year. Similarly, Agilent said that several design wins will be ready around this summer.

Traditionally, Japan defies the norm when it comes to the popularity of camera phones. Eighty to 85 percent of the mobile phones shipped in Japan last year already had a camera. While Japan snaps up each new model, In-Stat/MDR's Strother wrote in his report late last year, "high-end handsets are all dressed up with nowhere to go" in the United States and Europe.

But Strother today is changing his tune. "I don't think camera phones are just a Japanese fad," he now concedes. "I think Europeans, Americans and others [in Asia] will start to adopt these devices this year and in coming years." Although he saw relatively few pictures two a month being sent over the networks by Japan's 15 million-plus subscribers, Strother predicted, "Camera phones will also catch on outside Japan for the simple reason that just about everyone likes taking pictures.

"When a digital camera comes built into a mobile phone, and snapping a photo is easy and sending it to someone is easy (and affordable), then people will do it."

Philips' McGoldrick said that even with the interoperability and compatibility issues for the Multimedia Messaging Service in Europe today and the technology challenges of designing a high-resolution CMOS imaging sensor at low cost, "we are still convinced that [the camera phone] market will take off because network guys really need this.

"There is nothing more important than imaging in next-generation mobile phones," McGoldrick said.

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