The components market always seems to be in a state of accommodation, creating products to support every other sector’s designs. Whether it’s a power source that fits an oddly shaped printed-circuit board (PCB) or a motor that can deliver massive torque levels in a space the width of a finger, component makers innovate for innovators.
Over the past year, for example, OmniVision gave digital-camera designers a leg up in their work with its BSI CMOS image sensor, enabling them to create even smaller products while boosting image quality. The LED gurus at Osram Opto Semiconductors claimed a new record for white-LED brightness. And, assembly specialist Spiralock offered large-system developers new hope for ensuring product durability, stability, and reliability while promoting space savings.
CMOS IMAGE SENSOR DOES A BACKFLIP
With the help of chipmaker Taiwan Semiconductor, OmniVision Technologies turned digital imaging upside down in June 2008. Forsaking the usual path that’s taken in CMOS-sensor circles, OmniVision introduced its OmniBSI architecture—a radical sensor design that exploits backside illumination (BSI) to boost image quality while simultaneously shrinking overall pixel sizes down to 0.9 µm. In essence, the new technology addresses the demands for better picture quality in ever smaller and more featurepacked cameras.
Contrary to traditional frontside illumination (FSI) CMOS image sensors, the OmniBSI architecture literally turns the sensor chip upside down. Consequently, it accepts light from what was the backside of the silicon substrate.
With FSI sensors, the metal and dielectric layers necessary for the sensor to convert photons into electrons partially impedes light hitting the photosensitive area. Conventional FSI devices can also block or deflect light from reaching the pixel, which reduces the fill factor and can cause problems such as pixel crosstalk.
OmniBSI reverses the arrangement of layers, situating the metal and dielectric layers under the sensor array so light hits the silicon layer unimpeded (Fig. 1). Thus, the sensor’s fill factor improves and thereby increases low-light sensitivity significantly.
In addition to optimizing light absorption, the BSI arrangement creates a 1.4-µm pixel, a feat OmniVision claims surpasses all performance metrics of most 1.75-µm FSI pixels. At that size, FSI pixels impose requirements upon certain camera components, such as a larger lens.
Other advantages OmniBSI offers include a higher sensitivity per unit area, improved quantum efficiency, lower pixel crosstalk, and photo response nonuniformity. Also, BSI supports a larger aperture size, which allows for lower camera-lens f stops. For more details, visit www.ovt.com.
WHITE LED SCALES THE BRIGHTNESS LADDER
Exactly how much brightness can be squeezed out of one white LED? We may never know because when higher brightness is necessary, Osram Opto Semiconductors designs a new and brighter LED.
Back in July 2008, the company set what it calls a world record for brightness and efficacy with a white-LED prototype using 1-mm² chips. The component is capable of 155-lm peak brightness and 136-lm/W efficacy (Fig. 2).
The prototype delivers this performance under standard operating conditions using a forward current of 350 mA. Furthermore, with color coordinates at 0.349 (CX) and 0.393 (CY), the component produces a color temperature of 5000 K.
Timely advances in materials and LED technologies, Osram claims, are responsible for creating this matched combination of parts consisting of optimized chip technology, an efficient light converter, and a high-performance package. The prototype also supports higher operating currents. At a drive current of 1.4 A, it delivers up to 500 lm of white light (Fig. 2, again).
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