Joan L. Mitchell

Joan L. Mitchell
Joan L. Mitchell
Leading developer of image compression methods; coinventor of jpeg.

Joan L. Mitchell began her career in 1974, as a research staff member of the Exploratory Printing Technologies Group at the IBM T.J. Watson Research Center in Yorktown Heights, New York. Her first assignment was to "invent new ways to leave marks on paper." Her first patentable invention was a method of ultrasonic printing.

In spring 1975, she collaborated on invention of the resistive ribbon thermal transfer printing technology, which led to IBM's Selectric Quietwriter typewriter a decade later. The following summer, she switched fields to focus on data compression, which led her to invent novel binary facsimile compression techniques. She wrote IBM's proposal for an international, two-dimensional facsimile data compression standard. By 1980, she was manager of one of several teams that created the IBM Series/1 Internal teleconferencing system, eventually installed in more than 100 locations worldwide. Her fast decompression code migrated into many IBM products on multiple processors.

Mitchell's team also created fast grayscale compression and decompression. The team gradually migrated into fast rotation scaling up and scaling down of the binary images, sometimes combined with binary compression or decompression. In March 1987, she attended her first JPEG meeting in Darmstadt, Germany, and eventually transferred into ImagePlus marketing to focus on image education and JPEG. She returned to the research center in the fall of 1991 to coauthor the book on JPEG. Coeditor of the first JPEG standard, she pressured the committee to have it "good in both software and hardware."

In the mid-1990s, Mitchell took a leave of absence to work with IBM's Joint Bi-level Image experst Group in Burlington, Vermont. She helped verify a JBIG chip and coauthored a MPEG book. She also spent a semester at the University of Illinois, teaching in the Computer Science Department and conducting research in the Beckman Institute.

She returned to the IBM Research Center in fall 1996, and later transferred to the IBM printing systems division in Boulder, Colorado. Her skill with fast facsimile and JPEG decompression, rotation, and scaling proved crucial in eliminating bottlenecks in the high-end printers.

Over the course of her career, Mitchell was an IBM Fellow and a Fellow of IEEE as well as a member of the American Physical Society, Phi Beta Kappa, Phi Kappa Phi, Sigma Xi, and Society for Imaging Science and Technology. She was elected to the IBM Academy of Engineering and later to the National Academy of Engineering. She holds more than 110 patents and has more than 100 publications to her credit. She received many honors, including the Leadership Award from the Internationl Multimedia Telecoms Consortium and the Engineering at Illinois Alumni Award for Distinguished Service.


  • MS, Physics, 1971
  • PHD, Physics, 1974