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18Mpixel camera phone, anyone?

Posted: 15 Oct 2009 ?? ?Print Version ?Bookmark and Share

Keywords:image sensor? IP core? baseband? application processor?

Core issue
In reality, the key reason for a camera phone being a crappy camera is its lens. Lack of space in a cell phone makes it difficult to integrate a decent lens with a robust mechanical auto-focus system.

Technology suppliers, while busy feeding the megapixel race, rarely talk about the lens, complained Jim McGregor, chief technology strategist at In-Stat. "On handsets, you are typically limited by the lens. Just because you can produce a 12Mpixel image, it doesn't mean that you can capture enough light and information to do so." He added, "Even on point-and-shoot cameras, this is an issue. And they have better lenses."

"The best solution for handsets is to integrate as much as you can, while matching the capabilities of the image subsystem to the quality of the lens," McGregor said.

Although its solution is not perfect, Silicon Image claims to offer advancements to remedy such a mismatch. The camerIC-18 IP core, for example, now comes with such new features as bad pixel detection/correction and noise reduction techniques.

The dirty little secret nobody wants to point out is that the CMOS image sensors commonly found in mobile phones often come with defects. It's because error-free CMOS image sensors are too costly for budget camera phones.

The camerIC-18 IP core offers the ability to detect and replace defective pixels, said Richter.

As the race for higher resolution CMOS sensors ratchets up, the increase of noise has emerged as another unintended problem. Advances in CMOS process technology enable smaller and smaller transistors and storage cells, thus increasing the pixel density. But the increased pixel density means reduced pixel size, which, in turn, means reducing the number of photons the sensor can detect, thus lowering the signal-to-noise ratio.

The already noticeable noise observed in lower-resolution digital still cameras will become even more visible in higher resolution CMOS sensor cameras. The camerIC-18 promises to eliminate or significantly reduce such noise.

Other features the camerIC-18 IP core supports include wide dynamic range processing and digital image stabilization, along with standard features such as lens shade correction, auto focus measurement, auto-white balance and auto-exposure support by brightness measurement.

Competitive market
The common trend among competing ISP suppliers is to add more features to their ISPs, so they can drive them further into the higher-end mobile handsets.

Samsung Electronics in September announced its newest quarter-inch optical format, 5Mpixel SoC image sensor called the S5K4EA. Samsung's new SoC imager combines a CMOS image sensor with an ISP. The Korea giant is claiming the new solution can bring digital still camera functionality to high-end mobile phones.

Earlier this year, NEC Electronics launched a new SoC product that enables mobile phones to output full-HD (1080-pixel) video streams and up to 12Mpixel still image data retrieved by a CMOS sensor. Other features integrated in the new SoC include: image-stabilizing and optical-compensation technologies, often found in high-end digital still cameras.

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