The night her father came home from the laboratory with a box, Molly Picha remembers, he gathered his children in the living room to make an announcement.

"He said 'This is going to change the course of history of all mankind,' " said Picha, who added she was too young at the time to understand what he meant.

In the darkened living room, her father, Robert J. Collins, flipped a switch on the box and there it was: a red beam of light throwing a signature laser dot on the wall.

The ruby laser he demonstrated that night was the creation of a team at Bell Laboratories that included Collins and colleagues Donald F. Nelson and Wolfgang Kaiser, among others; they were among the very first scientists to build a laser, though credit for its invention went to others.

Collins, a World War II Army veteran who earned his Ph.D. in physics from Purdue University, would go on to become the head of the Department of Electrical and Computer Engineering at the University of Minnesota, where he was known as a tough but helpful professor. He steered the department through the 1960s then, after 15 years of teaching, led the department for a second time in the 1980s as the university built the department a new home, now known as Keller Hall.

After retirement he moved to Bethesda, Md., where he continued to publish research and doted on his grandchildren.

He died July 17. He was 90.

Robert John Collins was born in Philadelphia and raised there and in Miami Beach by his mother after his father died. A high school teacher introduced him to math, and he carried a love for it into college, eventually settling on physics as his field of study.

He was drafted in 1943 and, because of his physics background, sent to Minnesota where the Army was conducting radar training. He met his first wife, Patricia Anne Whitten, in Minneapolis, married in 1944, and after two more years in the Army and graduate school, found himself employed at Bell Labs in Murray Hill, N.J.

In the summer of 1960, as several teams of researchers in the U.S. raced to build the world's first laser, Arthur Schawlow and others at Bell Labs were intrigued by a New York Times account of a successful laser built by Theodore Maiman at Hughes Research Laboratories. Maiman hadn't published an academic article to back his claims, but there was enough information in the newspaper article for the Bell Labs team, which included Collins, to modify their experiments.

The team was the first to obtain a "pencil beam" of light, said Nelson, a professor emeritus of physics at Worcester Polytechnic Institute. Their eureka moment came when the laser threw a red dot on the wall.

Credit for the laser's invention was eventually scattered among several people, including Maiman, Gordon Gould and Schawlow, who in 1981 received the Nobel Prize in physics.

Collins moved to Minneapolis in 1963 to become a professor at the U. He became department head during the tumultuous 1960s, when antiwar demonstrations were rampant.

He was known for being a challenging professor; he once failed a third of his class. Some seniors had to retake the class during summer school to graduate, said his nephew, Dave Ankers.

Said another former colleague, retired U Prof. Pat Kumar: "He was very quick to grasp ideas and to engage you in a very meaningful conversation." Kumar said he never heard Collins complain about who got credit for the laser.

"He was one of the very first to have demonstrated laser communication, and that was good enough for him," Kumar said.

"He told us when we were kids that lasers were going to change the world," said son Bill Collins. His father later gave him one of the ruby rods used in those early lasers, a pencil-like tube he now considers a treasure.

Collins's second wife, Beatrice Agger, died in 2001. He is survived by four children, four stepchildren, grandchildren, and great-grandchildren. Services have been held.