Academic career

During the later years of his doctoral studies, Fossum served as an acting instructor at Yale University.^[2] After graduating Yale, Fossum became a member of the Electrical Engineering faculty at Columbia University from 1984 to 1990. At Columbia University, Fossum performed research on CCD focal-plane image processing and high speed III-V CCDs. In 1990, Fossum joined the NASA Jet Propulsion Laboratory, California Institute of Technology to manage JPL's image sensor and focal-plane technology research and advanced development.^[3]

He joined the Thayer School of Engineering at Dartmouth as a professor in 2010 to perform research on Quanta Image Sensors (QIS).^[4]

Professional career

In 1995 Fossum and Sabrina Kemeny co-founded Photobit Corporation with 3 other co-founders to commercialize the technology.^[5] Fossum left JPL to join Photobit full-time in 1996. In late 2001, Micron Technology Inc. acquired Photobit Corp. and Fossum was named a Senior Micron Fellow; he remained with Micron and was let go after about a year.^[6] In 2005, he joined SiWave Inc., a developer of MEMS technology for mobile phone handsets, as CEO. SiWave was renamed Siimpel and grew substantially before his departure in 2007. During his tenure, the company raised multiple rounds of venture financing prior to his departure. Severely damaged Siimpel was acquired for an asset only acquisition for $15M.^[7] In 1986, he co-founded the IEEE Workshop on CCDs, now known as the International Image Sensor Workshop (IISW). In 2007, with Nobukazu Teranishi and Albert Theuwissen, he co-founded and was the first President of the International Image Sensor Society (IISS)^[8] which operates the IISW.

Invention

During the early 1990s, a JPL research team that included Fossum, Sunetra Mendis, and Sabrina E. Kemeny developed modifications to existing CMOS active-pixel sensor (APS) designs. The team integrated Nobukazu Teranishi’s pinned photodiode concept into on-chip camera system designs. They also included other already invented technologies by other people, such as a sample and hold in the sensor chip. ^[9][10]Based on these changes and additions, the JPL team made their first image sensor.^[11][12] The JPL-developed sensor incorporated intra-pixel charge transfer within a CMOS architecture, building on prior APS and pinned photodiode work developed elsewhere.^[13] In 1994, the JPL image sensor team proposed an improvement to the CMOS sensor: the integration of the pinned photodiode (PPD). A CMOS sensor with PPD technology was first fabricated in 1995 by a joint JPL and Kodak team that included Fossum along with P.P.K. Lee, R.C. Gee, R.M. Guidash and T.H. Lee. Further refinements to the CMOS sensor with PPD technology between 1997 and 2003 led to CMOS sensors achieve imaging performance on par with CCD sensors, and later exceeding CCD sensors.^[13][14]