Two-piece processor removes 'noise' from images

A Silicon Valley company has developed a two-piece image processor chip set that removes noise from image files in digital cameras. Leading Japanese companies have designed the chips into more than five digital cameras that will start to appear in the 3Q, and one industry watcher said the set could give newcomers a way to make popularly priced models.

NuCore Technology Inc.'s CleanCapture chips are the NDX-1260 analog front-end processor and the SiP-1270 digital back-end processor. The analog chip processes 50Mpixels/s and enables pixel-by-pixel color correction. The digital chip processes 75Mpixels/s, enough to compress 2Mpixel images in JPEG and in Motion JPEG at 30fps. This means the processor can capture images of high-definition quality at a normal video rate without using an external buffer memory.

Six-year-old, privately held NuCore didn't identify the companies that have adopted its 2G chipset, but Matsushita used the company's 1G chips in a digital still camera and JVC used them in a camcorder. Only two or three digital camera makers still develop their image-processing technology in-house, said Seiichiro Watanabe, NuCore's founder and CTO. The others outsource the technology, and are fair game for NuCore.

The company projects a worldwide 2004 market of 37M units for digital still cameras, 12M units for digital movie cameras and 142M units for camera-equipped mobile phones. The cameras in each of those systems are moving toward higher resolution.

"High-megapixel CCDs [charge-coupled devices] without corresponding high-quality image processors will not produce optimum-quality images," said James N. Chapman, president and CEO of NuCore. The CleanCapture chips will satisfy the shift to higher resolutions, he said, including hybrid cameras that capture both still and moving images.

"It's important to get a clean signal without noise from the input stage," said Watanabe. "If the material contains noise, it won't become clean even when making full use of costly image science technology." That's the reason NuCore "dealt with the analog stage. We analyze noise and we remove each factor one by one."

The NDX-1260 processor converts an analog signal from a CCD image sensor into a digital signal. The processor's programmable gain control can adjust gain for each pixel at a 50MHz sampling rate and adjusts white balance for each pixel. It consumes an average of 60mW at 30MHz operation. The device comes in a 52-pad, surface-mount leadless shielded package and is fabricated by Taiwan Semiconductor Manufacturing Co.

Existing analog front-end processors are not able to adjust pixel-by-pixel gain, according to NuCore. "White-balance adjustment in the analog stage eliminates the need to adjust white balance in the digital domain," Watanabe said. "With conventional technology, white balance can be done only in the digital domain. But it results in false color artifacts."

"NuCore's approach removes noise from the root. Conventional efforts compensate for noise in the later digital processing stage, which does not eliminate noise efficiently," said Kumio Yamada, a photographer who runs a specialized digital camera Web site. By lowering the bar for new manufacturers and enabling them to build digital cameras at popular price points, the NuCore image-processing engines could crack the dominance of Japanese manufacturers, said Yamada.

The SiP-1270 digital processor accepts the 12-bit output signal from the NDX-1260. Fabricated on a 0.13?m CMOS process by TSMC, the digital device includes an image processor hardware block with 20 flexible hardwired image-processing pipelines, a motion JPEG engine that can support up to 24Mpixel CCDs, five DAC, interfaces for Compact Flash and Secure Digital cards and I/Os such as USB 1.1, and an embedded ARM9 processor.

All image processing is done at the hardwired block at 75Mpixels/s. When the five D/As are fully in operation, the chip consumes about 400mW; otherwise it takes about 100mW on average, the company said.

Since the CleanCapture chips lower noise at the analog stage, the image files have a smaller data volume. If an image file contains noise, the noise is treated as data and deteriorates compression efficiency. A JPEG file created by NuCore's processor is on average a half or one third the size of conventionally processed JPEG files, said Watanabe.

CleanCapture technology, therefore, lessens image data without introducing a new compression technology, he said. For mobile-phone applications, which the company views as a big opportunity, NuCore intends to develop a smaller chip set with lower power consumption by omitting functions a handset doesn't need.

-Yoshiko Hara

EE Times