Thomas I. Harris completed his undergraduate studies at the University of Wisconsin, his home state. For graduate work, he went to the University of Rochester. In his time there, he worked at Bell & Howell Company in the summers. In 1953, Harris began full time at Bell & Howell, where he would stay for ten years. There, he saw the transition into computer programming and was instrumental in this switch.

After his time at Bell & Howell, he moved to Pasadena, California and founded Optical Research Associates in 1963 as an optical engineering services firm. The company’s focus was do develop optical software programs. Later, the company developed CODE V, a computer aided design software used to model, analyze, optimize, and provide fabrication support for the development of optical systems for diverse applications.

He served for 11 years as Treasurer of SPIE and in other capacities for both OSA and SPIE. He holds five patents and has published numerous papers on optical design. He is a Fellow of both societies and has received honors over the years, including the Joseph Fraunhofer Award/Robert M. Burley Prize, SPIE's Presidents Award, and co-recipient of the SPIE Technology Achievement Award for the development of CODE V in 1984. In 1995, he was made a Life Member of SPIE.