20 Computer P u b l i s h e d b y t h e I E E E C o m p u t e r S o c i e t y

N E W S B R I E F S

R ice University researchershave developed a hard-ware-software approachthat promises smaller, lessexpensive digital cameras

that use batteries more efficiently.This would enable digital cameras towork longer and eliminate the needto change batteries often, long aproblem for users.

Generally, digital cameras collectall the information from a targetscene and compress much of thedata using a compression technol-ogy, typically JPEG, to reduce theamount of processing necessary.

“When it works correctly, com-pression removes redundant info,

and so the images remain more orless the same visually,” explainedRice University researcher and pro-fessor Rich Baraniuk.

However, he added, “Compres-sion consumes quite a bit of batterypower in a digital camera.”

The Rice technique, on the otherhand, would collect just enoughinformation from a target to extrap-olate into a full picture, withoutrequiring compression.

To begin the process, algorithmsin an external computer determinewhether an image can yield a goodpicture via the new technique,Baraniuk explained.

The Rice research used an emerg-ing field of information theory calledcompressive sensing, in which algo-rithms take a few randomized mea-surements of a scene and extractinformation for the whole picture.

The prototype device uses onephoto diode sensor, so in effect, it’sa single-pixel camera, Baraniuknoted. Conventional digital camerascontain millions of sensors, each ofwhich represents a pixel.

In their prototype camera, the Riceresearchers used a one-square-incharray with 786,000 tiny mirrors,based on Texas Instruments’ digitalmicromirror technology, already uti-lized in some digital cameras.

The camera randomly turns halfthe mirrors on and the other half off,about 200,000 times per photo. Themirrors direct the light to a second

lens, which collects it and focuses itonto the sensor.

The data gathered for the photo isbased on the average light intensityof the “on” pixels, as measured bythe sensor. The camera’s algorithmsthen extrapolate the data to buildthe entire photo.

Eliminating compression lessensthe drain on cameras’ batteries, anddecreasing the number of sensorsreduces a camera’s size and cost.Using the Rice technique with con-ventional digital cameras that offerrelatively few megapixels couldboost their image resolution.

This kind of camera could also beused for nonconsumer purposessuch as infrared imaging and tera-hertz imaging, commonly employedin security and spectroscopy appli-cations. Current digital camerascan’t work with the light waves thatthese applications use.

The Rice scientists still must doconsiderable work before their cam-era could be commercialized. Forexample, the prototype device isabout the size of a tabletop and itsimage-extrapolation algorithms areslow.

Baraniuk said his team is also try-ing to make the array’s mirrors flipfaster, to accelerate the image-acqui-sition process.

“It is an interesting, potentially use-ful technology for consumers, al-though it’s too early to say whetherit will ever appear in digital cam-eras,” said Harry Wang, a digital-consumer-imaging analyst with ParksAssociates, a market research firm.And, he added, finding a first adoptermay be a problem because manufac-turers want to recoup their invest-ments in their current technologies.

In response to requests for com-ment on the Rice research, Kodakdeclined and other major cameramanufacturers didn’t respond. ■

News Briefs written by Linda DaileyPaulson, a freelance technology writerbased in Ventura, California. Contacther at ldpaulson@yahoo.com.

Rice University scientists have developed

a new approach that promises less costly,

less bulky, and more energy efficient digi-

tal cameras. Standard cameras use mil-

lions of sensors to gather information

about a scene and then compress the

data to reduce the processing load.The

Rice technique employs one sensor and

uses algorithms to extrapolate the small

amount of data into a full picture.

ResearchersDevelop EfficientDigital-CameraDesign

March 2007 21

Scrabble Program Wins by Inference

A research team has developed a computer program that wins atScrabble not only by maximizing its own score but also by minimizingopponents’ scores via analysis of their moves.

Assistant professor Eyal Amir and doctoral candidate Mark Richards atthe University of Illinois at Urbana-Champaign (UIUC), developedInferencePlayer as an application that works with and plays against theopen source Quackle Scrabble program.

InferencePlayer has not competed against any elite human players intournaments yet but has beaten Quackle, Richards noted.

Basically, InferencePlayer uses information about the tiles its opponentsmost recently played to infer what tiles they might have and what theirnext move will probably be, enabling the program to block their ability toform a high-scoring word.

For example, Amir said, if an opponent plays the word “pigeon,” the tileleft in their rack probably isn’t an “s” because if it was, they likely wouldhave played the word “pigeons” to get the 50-point bonus for playing allseven of their tiles at one time.

InferencePlayer’s algorithms consider all the possible letter combinationsopponents might have held when they last played and determines theirrelative likelihood, he explained. The program then focuses on the mostprobable ones.

Tracking tile plays is what elite and competitive Scrabble players typicallydo, Amir noted.

This ability to precisely infer information from play to minimizeopponents’ scores differentiates this program’s strategy from that of otherScrabble programs—such as Quackle, Maven, and Crosswise. They storeentire dictionaries so that they can pick their own best moves andmaximize their own score. InferencePlayer also uses this approach.

The UIUC researchers say they may try to improve their program’s abilityto create a detailed model of an opponent’s play.

Richards noted, “We’ve been in contact with the authors of Quackle and areplanning to work with them to include our player in their upcoming version.”

Also, he said, “We believe our study of Scrabble can help us improvecomputer play in other games, such as poker and its variants.”

Unlike traditional cookies, thecache cookies are kept in an areaof the browser associated withstoring images. In this area, thecache cookies are harder toremove.

According to Jakobsson, the cook-ies maintain user privacy via anony-mous authentication. They log onlygeneral information about a pur-chase, enough for the system toauthenticate the user but leave outspecific data such as the buyer’sname, he explained.

New Technology Prevents Click Fraud

R esearchers have developed anew technique designed to pro-tect online advertisers from

click fraud. Many companies pay Web site

owners who host their advertisementsevery time that someone clicks on oneof their ads. However, there have beencases of fraud in which, for example,Web site owners have hired people orused bots to click repeatedly on an adto drive up their revenue, or otheradvertisers have clicked on ads toexhaust their competitors’ budgets.

Indiana University and RSALaboratories, the research arm ofvendor RSA Security, are developingthe Premium Clicks technique,which works by identifying clickslikely to be from actual shoppers.

This contrasts with standard ap-proaches that try to identify onlyfraudulent clicks, explained IndianaUniversity associate professor MarkusJakobsson. These techniques missmany fraudulent clicks, he noted.

The standard approaches workwith Bayesian heuristic filters that useobservations of previous behaviors todevelop rules for determining theprobability that a click is fraudulent.For example, one rule might state thatif many clicks originate from an iden-tical IP address within a short periodof time, they are probably fraudulent.

However, there are numerousways to commit click fraud, includ-ing many with no telltale signs,which make it difficult to create aneffective automatic-classificationmethod, Jakobsson said.

With Premium Clicks, if users visita trusted Web site and conduct aqualifying transaction such as a pur-chase, the site will cache a crypto-graphic token—called a cachecookie—on their browser. If theusers then click on an advertisementat another site, the system releasesthe token to that second site, therebyidentifying them as a legitimate vis-itor who does business online, notsomeone committing click fraud.

Premium Clicks might not identifyall legitimate activity, he noted, butalmost all of what it identifies islegitimate.

Nonetheless, click fraud will per-sist, so companies must continuemonitoring their online advertise-ments, said Forrester Research senioranalyst Shar Van Boskirk.

RavenWhite has released a Betaversion of the technology to selectedparties and plans to license the tech-nology to vendors for commercialrelease later this year. ■

22 Computer

N E W S B R I E F S

or less expensive to produce, saidJoe Brown, SiTime’s vice presidentfor strategic alliances.

Silicon-based clocks are lessexpensive to make because manu-facturers can use well-established sil-icon mass-fabrication processes,Brown said. “Silicon will yield tensof thousands resonators from onesilicon wafer,” he noted. And, headded, as technology improvementsenable smaller clocks, the yield perwafer will rise and the cost will drop.

Quartz, on the other hand, mustbe carefully polished to specificdimensions to achieve the desiredoscillating frequencies for clocks.

And then, said analyst Carl Howewith market research firm Black-friars Communications, quartzclocks must be placed on a circuitboard, which adds cost. Siliconclocks can be etched right into anintegrated circuit like any otherpiece of a chip, he noted.

Also, the clock mechanism can bebuilt smaller in silicon. SiTime ismaking a silicon clock that is just300 micrometers square, while anequivalent quartz clock is about amillimeter wide.

SiTime’s microelectromechanicalsystem (MEMS) clock uses electro-static forces to make multiple pieces of silicon resonate at a givenfrequency.

Users could feed the given fre-quency of one silicon clock into aphase-lock loop electronic system thatmultiplies or divides the frequency,yielding different levels. A quartzclock produces just one frequency.

Researchers at various universitieshave worked on silicon clocks fordecades, Brown said. However, heexplained, they’ve been unable todevelop clocks as consistently accu-rate as those made of quartz becausethe silicon versions were sensitive totemperature changes that causedunstable performance.

However, improvements inMEMS fabrication—specifically theuse of high manufacturing tempera-tures to remove silicon contaminantsthat cause temperature sensitivity—have made high-quality silicon oscil-lators more practical.

“Silicon clocks traditionally havenot been as accurate as quartz. Thisis one of the problems that silicon-clock companies claim to havesolved,” said Howe.

The first silicon clocks couldreplace quartz clocks in simplerapplications, such as basic micro-processors, but not in complex chipssuch as those used in GPS devices,which require high precision levels,according to Brown.

“The big challenge for silicon-clock adoption,” he said, “is thatquartz has been used successfully forover 40 years.” ■

M any aspects of computertechnology have changedand improved over the years,

but one crucial element has not: thequartz-based clock that paces thework done by traditional synchro-nous processors.

Now, SiTime, an integrated-circuitdesigner and vendor, is about torelease a silicon-based oscillatingclock that would be smaller and lessexpensive than quartz clocks. This,in turn, could enable the productionof smaller and less costly devicessuch as portable media players anddigital cameras.

A traditional chip’s clock is anoscillating quartz crystal that vibratesat a regular frequency, measured ingigahertz or megahertz, upon receiv-ing an electric current. The clock syn-chronizes every action of a chip,controlling the order in which theprocessor performs necessary tasks,including sending signals to circuitsand regulating the data flow.

During the past 40 years, quartztechnology has advanced somewhat,but the fabrication and packaginghas changed very little, so the clockshave not gotten significantly smaller

Silicon Clock Promises ImprovedComputer Technology

Editor: Lee Garber, Computer,l.garber@computer.org

A company has developed a new silicon-based clock to be used as a smaller, less

expensive version of the quartz clocks that pace the work done by traditional

synchronous processors.