A closer look at the DALSA Image Sensors and Business
 It's
a drizzly Tuesday morning when we arrive at the
High Tech Campus,
a hotspot for innovation in Eindhoven - the Netherlands, where we can easily park
our car in one of the natural parking garages. The visit today has been triggered
by the recent announcements of the
PhaseOne P65+ and the
Leaf AFi 10 medium format
digital cameras with their innovative high resolution image sensors; the
DALSA Image
Sensors Business division turned out the place to be.
 We
are welcomed by John Gommans (Director and Product Manager), Jan Bosiers (R&D director)
and Bas van Houtum (Director of Industrial Operations). John kicks-off our session
with a short history and background of the current operation. Back in April 2002,
the former Image Sensors Business of Royal Philips had been acquired by DALSA and
the Image Sensor division now has the overall responsibility for research, development
and manufacturing of the DALSA image sensors. The wafers that are used in the image
sensors are produced at the waferfab in Bromont, Canada, a production facility acquired
by DALSA in 2002 too.
Today, the DALSA Corporation is essentially built on three pillars, Digital Cinema,
Digital Imaging, and Semiconductors; they offer a broad product range including
image sensors and image sensor components, electronic digital cameras, vision processing
hardware components, image processing software algorithms, and semiconductor wafer
foundry services.
Digital
Imaging
The Machine Vision products are used for quality inspections of semiconductors,
printed circuits etc. Another challenging application is for postal & parcel inspection
systems where an image of an entire address (even handwritten) must be lifted
from letters, magazines, and parcels and must be interpreted using sophisticated
algorithms. A new growing market is the inspection of LCD monitors and HDTVs, which
should ensure that each pixel on your screen is working flawlessly.
Life science imaging is another rapidly growing sector with tremendous business
potential as well as unprecedented consumer benefits. For example, digital mammography
can provide better images using less radiation in far less time than traditional
film. DALSA Life Sciences has extensive experience in x-ray imaging in
applications such as: Mammography, Radiography, Bone mineral densitometry, and
other medical x-ray imaging such as micro computed tomography, dosimetry/photometry,
and radiation treatment planning.
 The
Image Sensor Solutions are used in advanced products for Digital Photography, (Aerial) Photogrammetry, Medical (X-Ray, Dental), Broadcast, Machine Vision, and Scientific
application (incl. Space). Some impressive milestones have been the 26 megapixel
CCD which has already been developed in 1993, the
111 million pixels CCD (10,560
pixels x 10,560 pixels) which has been produced for the U.S. Naval Observatory
in 2006.
 A
growing business is geospatial imaging and you will certainly have been looking
at images from DALSA sensors in Google's Maps, Microsoft's Virtual Earth and other global mapping services. You
might even have seen images from a great deal further away as the
Mars Exploration Rovers
are equipped with sophisticated camera systems that have DALSA CCD image sensors
onboard. And most of you will recently have been looking at images created by
DALSA sensors, as most of the host broadcaster's HD cameras at the Beijing Olympics
were equipped with their sensors.
Digital Cinema
The motion picture industry agrees that the future is digital. It also agrees
that HD resolution (or "2K") just doesn't measure up to traditional film, even if
you're only using a television to display it. That’s why film classics such as The
Wizard of Oz and Goldfinger were restored at 4K resolution and an increasing number
of film-originated features (such as The DaVinci Code and Spiderman2) go through
a 4K digital intermediate process. DALSA, as a leader in 4K, provides the most extensive
and complete line of 4K capture gear possible, from its Evolution and Origin 4K
cameras and optimized lenses to 4K data recorders and accessories. These advanced 4K cameras and other sophisticated equipment, ranging from the
latest ENG and EFP cameras to complete screening rooms make up the DALSA professional
rental service.
Digital photography
The recent announcements of the 60.5 megapixel PhaseOne and the 56 megapixel
Leaf medium format cameras have renewed the interest in larger format digital cameras
and at the same time revamped the discussions on the advantages and disadvantages
of the steadily growing number of megapixels in digital photography. Of course,
there’s quite a bit of difference between an 8 megapixel sensor in a camera phone
and a 60 megapixel sensor in a medium format camera, but the same technological problems may affect overall image quality.
Sensor performance
 Image
sensors sense light (photons) and generate a signal (electrons) depending on the
color (frequency) and brightness (luminance) of the light, and you can understand
that a larger pixel means more light and more photons. As the number of
pixels increases and the sensor package size decreases, the pixel dimensions will
get smaller and smaller. However, smaller pixels mean fewer photons, which means
fewer electrons and this will lead to a smaller output signal and with the same
noise levels the signal-to-noise ratio will increase proportionally, and image
qualify will suffer. DALSA has tackled
these problems from two angles:
The signal - A pixel on an image sensor is made up of a microlens, a color
filter, the metal wiring and the silicon substrate that collects the light. In
most sensors the height of the metal wiring is around 6 micron and the effective
fill factor is about half of the total pixel surface. In their latest 6 micron
sensors DALSA has managed to increase the fill-factor to 95% and to reduce the
wiring height to about 3 micron, half the size of the silicon width, thereby
increasing the effective pixel aperture and thus the signal level while
maintaining minimum color cross talk between red, green and blue pixels.
Note that
Sony and
Omnivision have recently announced a different approach to increase the effective
pixel size for image sensors in consumer products whereby the location of the wiring
and the silicon are reversed, and thus effectively increasing the width to 100% and reducing
the height to zero.
The Noise - The complementary method for increasing the signal-to-noise ratio is to decrease
the noise level. Noise is unwanted electrical or electromagnetic energy that degrades
the quality of signals and data. DALSA has achieved this through decreasing the
noise of the amplifier that converts the electrons to an output voltage. By
optimizing the technology and design of this amplifier, the noise level was
decreased by about 30%.
Circle
of Confusion
 "Circle
of confusion" is a term used in relation with camera optics, yet this same term
may be true for the myths about
diffraction. Just Google for terms such as "diffraction limit", "circle
of confusion" or “airy disk" and you'll find numerous articles on the subject,
and sometimes amusing or even heated discussions in the forums.
As Jan Bosiers explains: Diffraction of light is a phenomenon that results
from the obstruction of a wave front of light, and blurs the edges of optical
images. The degraded sharpness is solely determined by the imaging components
themselves and the optical wavelength. Thus, the lens system defines the
diffraction limit and not the pixel size of the digital image sensor. The
optical effect is equal for analogue and digital cameras, but with the
difference that a digital camera pixelizes the image. In order to minimize the
effect of the pixels and enhance the image resolution, small pixels are
preferable. This also accounts near the diffraction limit.
Diffraction of light will be less observable on color image sensors using the
RGB Bayer pattern. The image pixels form a matrix in which the left/right and
above/below neighbor-pixels always have different color filters that filter the
impinging light conform their spectral response. For the final full-color image,
the color interpolation results in a reduced the visual impact of diffraction.
Therefore F-stops up to F/16 and F/22 can still be used without any significant
diffraction problems for sensors with 6x6 micron pixels.
Clean-room visit
 We were very pleased to be invited (allowed) for a visit to the DALSA clean room. We all know the importance of clean room production and we have often enough seen
reports, pictures and videos about clean rooms.
Only by visiting such a clean room one gets a good impression how elaborate and delicate the process is. To manage a contamination level
of only 100 particles per cubic meter
turns out to be a major challenge. It took us quite a long time - a costume change
at the musical Cats would be quicker - to get "dressed" before we could enter the clean
room. Obviously, the people who work here everyday do it much faster.
We were impressed
to see that each step in the production process starts with an extensive quality
check. Bas van Houtum explains that, although the wafers arrive in very high quality from the
foundry, DALSA's
first step in the manufacturing process is a very thorough analysis of the wafer
surface to optimize the end quality and yield within the production flow. Powerful
computers support the process during all phases to ensure optimal quality. Each
sensor carries a unique tag to trace it during production and, if needed, even while
in use in the customer's environment. No sensor leaves the clean room without an
extensive stress test to simulate the extreme conditions in which some of these
sensors will have to operate later on.
The future
As we could have expected, DALSA was not at liberty to reveal any information
on upcoming products, nor camera manufactures planning to implement DALSA's standard
or specialized image sensors. DALSA will be present at the
Photokina
2008, in Cologne at September 23-28. Nevertheless, as the number of players in the
advanced camera market has reduced considerably over the last years, we tried our
luck and tossed the names on the table of the two players that seem to linger behind in the
50+ class, i.e.
Sinar and
Mamiya.
No comments though, just friendly smiles…. | 
