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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