Lee S. Girson does it with mirrors.

He has used his technical background in television and long experience in sales to form a Rockville-based company that makes and sells projection TVs and has licensed its patented design to three large Japanese producers of consumer electronics.

Girson is president of TheaterVision Inc., whose products can be found in homes, military installations, hospitals, schools, restaurants and lounges.

The mirrors are not mentioned as a figure of speech. They are a key to understanding the differences between standard and projection television sets.

* The first difference is that, when you watch a standard television, you are looking at the picture tube, a flat glass surface on which an electronic gun is "painting" a continually changing picture. When you watch a projection TV, however, you are looking at a separate screen on which the TV picture is projected from the surface of the picture tube by a system of lenses and mirrors.

* The second difference is the size of the picture you are watching. The rectangular viewing area generally is between 13 and 19 inches diagonal on a standard television set, while projection TV screens run between 50 and 92 inches diagonal.

TheaterVision has a design patent on the arrangement of TV chassis, lenses and mirrors for one of the five models it produces, according to Girson. He said that Matsushita (producer of Panasonic and Quasar projection TVs), Sony, and Hitachi (producer of RCA and Pioneer projection TVs) are licensed to use the design in TheaterVision's patent, and the company is negotiating with some 20 other manufacturers of projection TVs who may have infringed on its patent rights.

Girson believes that TheaterVision sets and those of the three other manufacturers licensed to use his company's patented design accounted for between 10 and 15 percent of last year's sales of projection TVs. He estimated total sales for the industry at $120 million. He added that, had the 20 other companies with which TheaterVision also is negotiating been licensed last year, the TheaterVision patent would have covered 70 percent of 1981 sales.

Girson has been connected with television in one way or another for most of his adult life. He was born in Homestead, Pa., a steelmaking town across the river from Pittsburgh, but grew up in Detroit and has lived in the Washington area since 1955.

He came out of the Navy after World War II and went to Michigan State Teachers College, where he received a bachelor of arts degree in public speaking because he was planning to get into radio. But along came television, so Girson went to the Detroit Electronics Institute to learn television technology because "I wanted to understand what produced a picture. I used to listen to radio and wonder what they looked like--the Lone Ranger, the Green Hornet."

After becoming conversant with wiring diagrams, the inner mysteries of cathode ray tubes and other technological marvels, Girson went to work for the House of Television, a big Detroit TV dealer. Next it was on to Chicago and Muntz TV--an early independent manufacturer remembered for its Madman Muntz advertising. There he was national sales manager and assistant vice president at age 23.

Girson followed this up with two more jobs that also helped to pave the way for TheaterVision. He moved here to work for a company called Technicolor of California that was marketing a system using mirrors to project technicolor movies. Then he went to work here for another California-based company--National Music Co.--marketing blank and prerecorded audio cassettes.

But he long had wanted to marry videotape and large-screen projection into some kind of entertainment system and, after National Music was involved in a merger, he left the company in 1972.

Girson soon teamed up with Benjamin H. Butler, a cabinet designer, and Gilbert Elliott, a former Air Force general who had specialized in electronic engineering.

After an unsuccessful venture with rear-screen TV--the picture was projected on the back of the screen and the viewer watched from the other side--the trio developed TheaterVision.

Although they started by producing most of the components of a set themselves, they now subcontract much of the work. They test available television sets and each year choose the chassis based on performance and reliability. Five have been used in the company's nine years of existence. Girson says that fewer than a quarter of one percent of TheaterVision's projection TVs have broken.

Fiber glass screens and cabinets are made to TheaterVision's specifications. The company adds a printed circuit board that it developed to eliminate distortion.

Work is performed at eight assembly sites east of the Mississippi and one in California. TheaterVision has four showrooms besides the Rockville headquarters and six main distributors who sell to dealers in 56 locations worldwide. The company employes 20.

Theatervision offers one-piece models with 50-inch and 60-inch diagonal screens, a two-piece model that can be ceiling-mounted or rested on the floor with five diagonal screen sizes ranging from 50 to 90 inches, an "economy" two-piece model with a plastic projection lens instead of a glass lens that also can be used with screens of various sizes, and a deluxe two-piece model with a screen housed in what looks like a bookcase and the projection TV in a coffee-table cabinet. Prices range from $895 to $2,495.