Camera flashes on OLEDs' promise

As a technology, OLED is an emissive display that proponents offer up as the next viable replacement for LCDs in mobile and other applications. Using a current-mode drive scheme to cause individual pixels to light up, OLED does away with the usual back- or front-lighting of the traditional LCD pixels that serve as light valves for a planar illumination source.

The 2.2-inch-diagonal OLED display used in the LS633 features 512 x 218 pixels and provides a very bright image with a wide viewing angle. System power consumption of 2 watts or more, however, was seen when measured on the bench. While we were unable to isolate the display's power contribution from that of other system electronics, this power figure is on the high side compared with LCD-based DSCs with comparable specs, and it leaves open the question of whether hopes for low-power OLED technology remain unfulfilled.

No stranger to complexity, DSCs routinely have to partition electronics across several assemblies to shoehorn circuitry into space-constrained enclosures. The Kodak camera is no exception: Components are spread across six separate rigid board or flex-circuit elements.

The main board supports the bulk of the ICs in the system. A charge-coupled device signal processor from Analog Devices (the AD9891), a Panasonic CCD vertical driver (MN3114) and an application-specific DSP media processor chip from TI (TMS320DSC25) form the image-processing core of the camera. Memory is provided by three chips: a 2-Mbyte NOR flash from Sharp (LH28F160), a Hynix 16-Mbyte SDRAM (HY57V281620HCT-H) and a 16-Mbyte NAND flash from Toshiba (TC581282AXB), serving code store, working memory and image store, respectively. Images can also be stored on a removable MMC/SD expansion card.

A custom Kodak/Fujitsu Graphics Display Controller (KDP0110) is used to interface with the SK OLED display. Also present on the main board are a stereo audio codec from Wolfson Microelectronics (WM8734) and a National Semiconductor audio amplifier (LM4862). To cope with the high density of fine-pitch peripheral or ball-grid-array packages and other components, Matsushita's co-laminated any-layer-interstitial-via (ALIVH) technology is used in the main board.

Another aspect of DSC complexity revolves around power management. Disparate core and I/O voltages and differing chip supply requirements lead to a variety of supply levels. Additionally, CCD imagers still require a host of bias levels for proper operation. Given the power issues and the need to control precision optics, a dedicated assembly is used in the LS633 to support eight voltage channels, with an 8-bit microcomputer from NEC (the microPD780055A22) and a four-channel motor controller from Rohm (BH6573FV) used for tackling power management and zoom, focus, aperture and shutter drive.

The 3.3-Mpixel CCD image sensor from Panasonic (MN39481) is mounted to a separate two-layer polyimide flex circuit, keeping this sensitive part isolated from the probable cacophony of switching noise elsewhere in the system.

On balance, the LS633 design illustrates that while analog technology remains a piecewise solution, the digital bits of a DSC have collapsed nicely (see www.eetimes.com/sys/uth/showArticle.jhtml?articleId=51202688 for an example of the same engine in a different product).

Despite use of a general-purpose imaging ASIC, programmability still allows Kodak to inject its own flavor of image processing, and a "Kodak Color Science Inside" label touts the software magic that turns raw CCD images into pictures with color fidelity, dynamic range and optical clarity that begin to rival film. Still, integration has its limits; memory devices remain separate items, being both a system variable and a challenge to co-fabricate economically with high-end logic.

The LS633 is not a particularly new camera, having been introduced in mid-2003, when we estimated total cost of goods sold to be less than half of the $400 price. But along with the electronics, the story here revolves around the striking "quiet period" for OLEDs since our analysis.

The LS633 is one of what are still very few examples of full-color active-matrix OLEDs in actual use in end products. Aside from present placements of simpler, passive-matrix displays, OLEDs are not yet taking over the landscape.

Bottom line? Cost and technology hurdles face almost every new technology, and in this case it seems there is tough sledding to displace the incumbent LCD.

David Carey, president of Portelligent (www.teardown.com), a producer of teardown reports and related industry research on wireless, mobile and personal electronics.

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