Smart Mini-Cameras

332 Pages·2013·38.913 MB·English

by  Tigran V. Galstian

Optics / camera technOlOgy
Smart
Smart
Mini-Cameras
Mini-Cameras
“… a pragmatic, useful primer to those wishing to know more about
this amazing technology, the camera phone.”

—From the Foreword by Tom Killick, LensVector Inc.
Miniature camera modules (MCMs), such as webcams, have rapidly become
ubiquitous in our day-to-day devices, from mobile phones to interactive
TV systems. MCMs—or “smart” cameras—can zoom, adjust their frame
rate automatically with illumination change, focus at different distances,
compensate for hand shake, and transform captured images.
With contributions from academics and field engineers, Smart Mini-Cameras
discusses the structure, operation principles, applications, and future trends
of miniature mobile cameras. It compares this technology with traditional
digital still cameras and explains the specific requirements of MCM
components (imposed by the size or type of application) in terms of
optical design, image sensor, and functionalities. The book describes the
implementation of several active functionalities, including liquid crystal
auto focus (AF) and optical image stabilization (OIS). It also explores how
new technologies, such as the curved detector and transforming optics,
are stimulating novel trends, including a miniature panoramic lens on
mobile phones.
By providing you with an understanding of the components and performance
tradeoffs of MCMs, this book will help you achieve the best camera design.
Edited by
It also answers frequently asked questions, such as the importance of
the number of megapixels in a mobile phone camera and the value of AF
Tigran V. Galstian
and OIS features.
K14933
ISBN-13: 978-1-4665-1292-4
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9 781466 512924
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Smart
Mini-Cameras

Smart
Mini-Cameras
Edited by
Tigran V. Galstian
Boca Raton London New York
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Contents
Foreword vii
Preface xi
Editor xiii
Contributors xv
Chapter 1 Lens Design and Advanced Function for Mobile Cameras 1
Peter P. Clark
Chapter 2 Modern Image Sensors 49
Junichi Nakamura
Chapter 3 Voice Coil Motors for Mobile Applications 83
Luke Lu
Chapter 4 Extended Depth of Field Technology in Camera Systems 99
Dmitry Bakin
Chapter 5 Liquid Lens: A Key Adaptive Component for Cameras 149
Bruno Berge
Chapter 6 Electrically Variable Liquid Crystal Lenses 181
Tigran V. Galstian
Chapter 7 Optical Image Stabilization for Miniature Cameras 215
Eric Simon
Chapter 8 Multiaperture Cameras 239
Andreas Brückner
Chapter 9 Future Trends: Panoramic Mini-Cameras 299
Simon Thibault
© 2010 Taylor & Francis Group, LLC v

Foreword
Evolution of Miniature Cameras
In 2013, it is possible to buy a decent camera* for less than what
a roll of film cost a generation ago. Mobile-phone cameras with
5 megapixels and autofocus are available for less than $5. Not only
are these cameras very inexpensive, they are also very capable.
Digital still cameras (DSC) were built to meet the demand for
instant photography following up on an idea originally developed
by Polaroid. Mobile-phone cameras took this a stage further, with
images that can be “instantly everywhere.”
How did this happen? Basic high-volume lens technology was
developed through Kodak’s Brownie in the 1930s to the Instamatic
in the 1960s. The development of molded plastic lenses, again pio-
neered by Polaroid, made mass-produced optics cheaper and eas-
ier to make. Charge-coupled device (CCD) sensors, which could
convert light into a matrix of electronic signals, began to replace
film and its associated transport mechanisms. These were shortly
followed by the more cost-effective complementary metal-oxide-
semiconductor (CMOS) sensors.
In the early part of this century, the idea of putting a camera
in a phone emerged. While this was made possible by the new,
cheaper, CMOS image sensor and molded plastic lens technol-
ogy, there was no certainty that this was something that people
wanted. The initial idea seemed to be that people would take pho-
tographs and send them to each other via a multimedia messaging
service (MMS). This was quite attractive to the carriers as, at the
time, they charged for data by the bit or byte and the idea was
seen as a revenue enhancer. The low quality of the images and
the clunky interface required to send images limited the initial
success of camera phones. However, the idea of always having a
camera with you was attractive and began to take hold.
The advances in both the CMOS image sensor technology
and the quality of the plastic lenses started to radically improve
camera-phone image quality. This led to a virtuous cycle where, as
the image quality improved, the cameras were used more, and as
they were used more, the motivation to improve the image quality
increased.
* Albeit a miniature camera module (MCM).
© 2010 Taylor & Francis Group, LLC vii
viii   ■   Foreword
In tandem with this improved image quality and increased use,
the means to share images became more compelling. Rather than
send images by MMS, the mobile internet allowed people to post
pictures on internet sites and social media. Sites such as YouTube
gave a home on the internet for video which has now become central
to the mobile imaging experience. This has had social consequences
that would have been difficult for anyone to predict early on in the
development of digital cameras. As cameras become increasingly
capable and less expensive through the use of solid-state technolo-
gies, not just in the image sensor, but also in lensing and light cap-
ture, we can reasonably expect a trajectory similar to that seen in
microprocessors and the emergence of an equivalent to Moore’s law.
While it is difficult to predict the implications of this, it is
always interesting to speculate. The written word became a unify-
ing and important cultural phenomenon when books became eas-
ily reproducible. When the method of creating books also became
reproducible with the advent of the typewriter and the word pro-
cessor, the written word became an even stronger cultural and
commercial factor. Some might say that this led directly to the
internet as a vehicle to distribute the newfound plethora of writ-
ten information. If we accept that man is primarily a visual crea-
ture, his very consciousness developing from the visual cortex, it
is hardly surprising that a method highly convenient for making
still and video images should be very successful. Once the internet
was born, it was almost inevitable that we should want to popu-
late it with images and video. The mobile-phone camera is a very
appropriate tool for this.
Perhaps it is not too much of a stretch to speculate further.
Could this cause as fundamental a change in the way we commu-
nicate and interact as was caused by the proliferation of writing?
Images, especially video images, are more visceral than writing
and as such may lead to more efficient communication. The use
of video images in the “Arab Spring” certainly gave most of us a
much more immediate and varied experience than we had been
used to in the past. It was not just the medium, after all there had
been plenty of video news reports in the past, but the fact that
nearly every aspect of the situation could be shown because the
mobile phone is almost undetectable and pretty much ubiquitous.
Hopefully, this new, more immediate experience will allow all
of us a greater degree of empathy and knowledge outside of our
own personal experience. On the flipside, this is not to say that
© 2010 Taylor & Francis Group, LLC
Foreword   ■   ix
the puerile and the trivial will not make up the vast majority of
material, as has been true of every medium in the past. It is also
true that it will almost certainly lead to a greater loss of privacy.
Technologically speaking, predicting the future may be easier,
less controversial, and more empirically based. As camera phones
become increasingly capable, they are replacing and enhancing
more and more devices and bring new utility. Already, there are
“apps” that can scan and collate documents. These range from
apps that are designed to keep track of business expenses to read-
ing tax documents and all manner of archiving. Note-taking apps
include facilities to photograph objects and documents, and to
embed videos. Bar-code reading and object recognition are used
to implement comparison shopping and are driving mobile com-
merce. Many of these uses of the camera phone were unimagined
a few years ago. In the future, cameras may be used to track eye
movements in order to control cursors, as range finders for auto-
motive and aerospace applications, and as an integral part of arti-
ficial intelligence systems.
A particularly interesting emerging photographic aspect of
mobile imaging, which may well be a harbinger of the future, is the
invention of the array camera. While we can confidently expect
known features such as zoom and optical image stabilization to
be quickly incorporated into mobile cameras, array cameras may
take photography to a different level. An interesting initial appli-
cation of this is the ARGUS-IS drone camera (the military always
get to develop the best toys!), which is an array of 368 standard
mobile-phone cameras, reportedly. These generate a 1.8-gigapixel
image, allowing an incredible amount of detail across a very large
horizon to be collected. It is not difficult to imagine that in the
future the very high-end cameras, the equivalent of digital single-
lens reflex (SLR) cameras and even larger format cameras used
for making movies, will be large arrays of cameras, using the
miniature camera as a building block. In the mobile phone, one
can envision a low-end phone having a “unicamera,” made of one
building block and a higher-end phone using a “multicamera,” a
small array of the same cameras. It is almost certain that the very
fact that it is easy to record videos and images and to know the
position and vantage points of such images will lead to ever more
accurate models of reality.
However, the reader’s speculation on these matters is as valid as
the author’s, and he or she will be happy to know that the rest of
© 2010 Taylor & Francis Group, LLC