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CMOS sensor-based "camera-on-a-chip" devices are here.(complementary
metal oxide semiconductors)(Cover Story)

From:

Advanced Imaging

Date:

January 1, 1999

Author:

Carlson, Brian

More results for:

"eric fossum"

It's Time for Differentiation.

An overview of the vendors in place worldwide to market "Cameras on a
Chip" - and the emerging differences between them in market targets and
value-added functionality.

Since the resurgence of CMOS sensor development in the early '90s,
Advanced Imaging has covered the development of the technology every step
of the way. Now, heading into 1999, CMOS releases are becoming a fairly
common occurrence, with the low-cost and low-power chips finding their way
into myriad consumer and pro imaging apps. For a few years now. we have
been seeing variants of CMOS devices with hard-wired image processing and
camera control functions appearing, currently being coined as
"camera-on-a-chip" devices, as each company races to differentiate its
product from the flock. The various apps that these chips are being
targeted at are similar for many competitors, but there is some debate as
to which design features are desirable for individually-tailored apps, and
exactly where the trade-offs for quality, cost, size, power requirements
and volume production are made.

Everyone seems to be getting on board, from places traditionally known
for CMOS development like the Jet Propulsion Laboratory (JPL), its
commercialized spin-off Photobit and Vision Ltd., to new start-ups and
established players like Hewlett-Packard which are getting in on the
action. With this kind of activity, the "camera-on-a-chip" revolution is
certainly here, and lines are being drawn in the sand daily.

First out of the gate

With global manufacturers waiting in the wings, it may still be too
soon to tell, but the leaders ont of the gate in terms of history, quality
and quantity of CMOS developments and deliveries are without a doubt
Photobit (Pasadena, CA) and Vision Ltd. (Edinburgh, Scotland). While these
two firms have a lot in common - excellent engineers, high-quality
products and competitive prices - they both have very different
philosophies and market plans for competition in the camera-on-a-chip
market.

In the November '97 issue of Advanced Imaging, Dr. Eric Fossum, chief
scientist and chairman of the board of Photobit Corp., noted that,
depending on the application for the chip, there tends to be two camps
advocating different approaches to camera-on-a-chip design. In the first
camp, which includes Photobit, color interpolation and image compression
takes place off-chip in a host computer or sister chip. This approach
permits adaptive processing to meet a wide variety of apps, but
unfortunately needs a sister chip or computer. This approach can be
important for certain cases; an example would be when interface bandwidth
is limited, since video chips produce a large amount of data and color
interpolation triples that data volume. The second camp, which includes
Vision Ltd., advocates putting as much of the color interpolation and
other digital signal processing on the same chip as the image sensor. This
is important for many stand-alone apps such as consumer digital cameras,
video phones, etc., and has other obvious advantages like a smaller
footprint and lower power requirements.

* Photobit. We recently sat down with Dr. Sabrina Kemeny, CEO of
Photobit, and Dr. Eric Fossum, for a brief discussion about the
plans and direction for their CMOS sensors. Asked to identify what sets
them apart from the other CMOS manufactures and what they felt will give
them a competitive edge in the camera-on-a-chip market, Dr. Kemeny
responded, "I think the number one thing that sets us apart from the other
manufacturers is quality. Our sensors have lower fixed-pattern noise, with
a higher fidelity image and better color fidelity...One of our other
unique advantages is that we are a highly focused company. We only sell
image sensors - we do not sell modules and we do not sell cameras -
therefore, we do not compete with our customers."

Both Dr. Kemeny and Dr. Fossum contend that they plan to be a dominant
force in the CMOS market and the leading global provider of high-quality
and high-performance sensors. This is no surprise if you look at the
history of Photobit, a firm founded by key scientists like Fossum and
Kemeny who, during their time with JPL, invented and developed the CMOS
active pixel sensor (APS) technology. Since the research had been spurred
by NASA's need for highly miniaturized, low-power, instrument imaging
systems for next-generation deep space exploration spacecraft (imaging
systems driven by performance, not cost), it becomes apparent why high
quality is synonymous with Photobit.

This dedication to quality and performance is evident with Photobit's
release of the PB720 CMOS chip. The PB720 will be presented at the
upcoming International Solid State Circuits Conference (to be held in
February in San Francisco) by Photobit's Dr. Barmak Mansoorian, and is
available in sample quantities now. Designed for machine vision. portable
devices, automotive, high-end security and broadcast apps, the PB720 has a
1280 x 720 pixel sensor with on-chip 10 bit ADC in a 2/3[inches] optical
format. It dissipates 250 mW while delivering pixel data at 60 fps. The
sensor also conforms to the 720 P60 high-def TV standard and offers 16:9
output. The PB720 is presently monochrome, but color will he added soon,
Dr. Fossum says.

On-chip functions are extensive on Photobit's chips, as in the case of
their present offering the PB159 CMOS APS, a 512 x 384, 1/4[inches],
color-camera-on-a-chip. On-chip functions include an 8-bit,
column-parallel, low-power ADC with TrueBit noise cancellation (TNC)
circuitry, optional frame and line valid sync signals embedded in the
digital output stream, programmable window-of-interest read-out to enable
electronic pan-and-tilt functions, auto gain and auto exposure, and more.

* Vision Ltd. This reporter also had a chance to catch up with Don
Lake, who, besides being a long-time contributing editor of this magazine,
is - in "real life" - North American General Manager for Vision. He gave
us his take on that firm's direction for manufacturing and marketing their
CMOS chips.

When asked what he felt set Vision apart, Don commented, "We do several
things that no one else does yet. The first one is that we make good
pictures...and while it's possible for others to deliver an excellent
image every once in a while, at this point in time. we have managed to
deliver very high image quality repeatedly in very high volume. We're
shipping a couple hundred thousand a month, and the image quality is
consistently high."

Most of the apps that Lake discusses for his firm all tend to be in the
high-volume area.

He comments, "The major market segments we're going after include
personal communications (video conferencing, etc.), toys, security,
automotive, symbology (barcode readers and the like), medical and digital
still photo. And those are all high-volume businesses; we're not doing
high-speed photo, X-ray and a lot of niche stuff. We're out to ship a lot
of parts."

Vision has a multitude of sensors for varying applications, including
the VV6407 CMOS device, a 356 x 292 pixel CIF color sensor targeted at the
video conferencing market. Vision has improved the read-out architecture
and color spectra of the chip, plus added a microlens to give 6dB
improvement over previous performance, all of which results in a
signal-to-noise ratio of 48dB at 200 lux. Also released last year was the
1.3 - million-pixel color digital still camera (DSC) sensor, the VV6801.
This sensor provides a resolution of 1306 x 1028 pixels and was the first
imaging device to offer 12-bit, on-chip A/D conversion. This sensor is
also available in a monochrome option. Also available is the VV6850, a
1016x804 color sensor for machine vision, digital still, medical imaging
and automotive.

When asked about the future of CMOS and some of the emerging trends, he
had this to say: "The integration of image understanding algorithms is a
really important vector for the future. It's not there yet, because nobody
knows which algorithms are going to take off first, so it's winding up as
two- and three-chip solutions where you have a photo plane on one chip and
an algorithm on a another."

CMOS start-up

Another firm dedicated to single-chip solutions is a company founded in
1995 called Omnivision Technologies, Inc. (Sunnyvale, CA). Steph Rutel,
marketing manager for Omnivision, said that his firm is striving to be the
leading innovator in providing CMOS sensors and app-specific products to
the various segments (video conferencing, video e-mail, security,
surveillance, machine vision, collision avoidance, biometrics, etc.) in
the OEM/mass market.

Rutel says, "There are two important implementation philosophies that
really differentiate these products from the competition. 'The first is
the high level of functional integration that we achieve in these imaging
devices. Many of the capabilities that have required multiple chips to
perform are all accomplished in a single device. The benefits for the
designer include, among others, lower power, smaller footprint and higher
reliability. The second (and critical to the technical performance of the
products) is that the majority of the signal processing (gain control,
white balance, etc.) performed by the device is done in the analog domain.
This is our expertise. This retains a maximum of signal information and
quality for intended applications. Since converting signals back and forth
between analog and digital can cause unwanted signal degradation, our
design doesn't perform the conversion until the signal is ready to be sent
over the bus."

Omnivision currently offers about ten different single-chip CMOS
sensors with resolutions from 320 x 240 to 640 x 480, in multiple formats
such as CCIR, 601/656, YUV 4:2:2, and RGB 4:2:2, and in both color and
black-and-white. Their flagship products are the OV7610 Digital (640 x
480) and the OV7510 NTSC/PAL (628 x 582) sensors. They both have a varying
array of automatic controls such as auto gain, auto white balance, auto
contrast, etc.

A recent release from the firm that may help to further solidify
Omnivision's position in the marketplace is the OV511 Advanced
Camera-to-USB Bridge (ACUB). The OV511 is a interface device that provides
a configuration for connecting the OV7610 CMOS sensor to the USB standard.
Mr. Rutel commented that they plan to utilize the OV511 ACUB to broaden
the appeal of their CMOS sensors into the USB market.

Global entry: HP and CMOS

As you may have noted in the Update section of our October '98 issue,
HewlettPackard (Palo Alto, CA) has now moved into the CMOS sensor
business. in October, HP released four new CMOS sensors, numbered
HDCS-1100 to 2000, ranging from CIF resolution of 352 x 288 pixels at 44
fps to VGA res of 640 x 480 at 15 fps, all developed specifically for use
in PC video cameras and low-cost digital still cameras. Bill Sullivan, VP
and general manager of the components group, says that the new sensors
were part of an overall initiative to bring together the components for a
complete electronic imaging solution. HP plans on producing
higher-resolution sensors and a line of image processing ICs that they
hope will ultimately produce a complete digital camera on a chip.

Some of the benefits HP is toting about their new sensors include a low
dark current (at 0.11 nA/[cm.sup.2]) for low noise levels and increased
dynamic range plus HP sensors incorporate and HP-developed color filter
that resists high temperatures, allowing machine soldering during printed
circuit board assembly. Special programmable features on the chips include
random access and windowing capability within the sensor array (for
electronic panning and zooming), separate red, green and blue gain
controls for greater color fidelity, and 4:1 sub-sampling of a viewing
window. permitting up to 58 fps for VGA and 162 fps for CIF. Other
programmable features include window size, interface timing, selection of
8-bit or 10-bit A/D output, etc.

CMOS R&D

The Jet Propulsion Laboratory (Pasedena, CA, one of the original homes
of serious electronic imaging development), has now come up with a
prototype CMOS chip with a 128 x 128 array that has a built-in electronic
shutter. The sensor has been demonstrated to stop high-speed fan blades
rotating at 1,800 rpm without blur. This could further enhance CMOS
ability. to penetrate video apps since the technique could boost video
images by eliminating the blurring caused by either fast-moving objects or
camera panning. This design was implemented by placing additional control
gates on both sides of the photo gate in order to determine the exposure
time for each pixel.

The people at Displaytech (Longmont, CO), best known for their tiny
virtual displays, working with engineers at Black Forest Engineering
(Colorado Springs, CO), have successfully integrated a spatial light
modulator (SLM) and electronic camera onto a single chip. The design was
made possible by using the cover glass that's used to confine the active
liquid crystal layer in the SLM to double as a diffractive lens array,
placing an optical element at each pixel location. With this set-up, the
system only requires the alignment of two mirrors. Displaytech is hoping
that this new design will help turn optical correlators into affordable,
off-the-shelf components.

Conclusion...

While some companies have set their sights on more highly-focused,
demanding and specialized applications, putting the emphasis more on
quality and performance than on high-volume production and sales to the
consumer market, many other industry players are pushing for the mass
market solely with single-chip solutions. Both sides have already produced
chips with acceptable quality that take care of most of the functions
needed for a consumer digital camera, so now the ability to offer some
added functionality, tailored for any assortment of already established
and emerging CMOS applications, becomes the real question for the next few
years. Soon, the "camera-on-a-chip" may be more appropriately called a
"system-on-a-chip," in which not only camera functions, but more dedicated
image-understanding/processing algorithms and an assortment of other
features are also incorporated.

COPYRIGHT 1999 Cygnus Business Media. This material is
published under license from the publisher through the Gale Group,
Farmington Hills, Michigan.  All inquiries regarding rights
should be directed to the Gale Group. For permission to reuse this
article, contact Copyright Clearance Center.

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