Norman Lear, who revolutionized TV comedy with such caustic and topical series as "All in the Family," "Maude" and "Mary Hartman, Mary Hartman," is quitting television.

Lear, 56, said yesterday from his Hollywood office that he is relinquishing his active producer's role for an "extended leave" after eight turbulent years because "I want to take a deep breath" and return to writing and directing theatrical motion pictures.

Lear now wants to spend a year working on a film project and avoid the "weekly crunch" of series productions. His previous films include "The Night They Raided Minsky's," which he produced; "Divorce, American Style," which he wrote and produced; and "Cold Turkey" which he wrote, produced and directed.

"I've done 1,400 series episodes - about 700 hours - in eight years," Lear said. "That's a lot of television, a lot of flexing the same muscles. I have an enormous desire to flex other muscles now."

Lear said the decision was not related to such factors as the current state of TV programming, the increased feverishness of network competition, or the fact that not all his recent projects have been successes; there were also such failures as "All That Glitters" and "A Year at the Top." Currently, even the once-mighty "Maude" is languishing in the polar regions of the weekly Nielson ratings.

"Our two companies, Tandem Productions and T.A.T. Communications, have a full, full plate of shows for next season," Lear said, "I think it's going to be every bit as exciting as it ever was." Lear's only relationship to the excitement, however, will be on a consultant basis.

Two of the new programs sound distinctly Learian in concept - "our kind of thing," Lear says. One is a weekly comedy about "a young couple who are not married but are living together" and the other concerns "a street nun who has to fight the establishment - in this case, the established church."

Lear's programs were often provocative in their treatment of such subjects as rape, homosexuality and abortion, but Lear's more substantial contribution to American television was in liberating comedy from the strictures of innocuous domestic farce and in revealing darker, more abrasive and more relevant aspects of American life.

Now some feel the pendulum has swung back the other way, to the escapist "Happy Days" kind of comedy, making Lear's style obsolete. It's also being said, and not only by TV critics, that there is less room for thoughtful programming in prime time than ever because the networks have become so aggressive in their drives to lure the largest possible audiences.

"To say I'm being driven out, of television is hardly the case," Lear said, however. His production company is "not going to compete in any way, shape or form" with "less thoughtful" kinds of programming, he said.

At the same time, Lear declined to make any judgements about the current quality of television. "I'm not a regular viewer," he said. "At night, I'm usually going over scripts. I have never seen a single episode of 'Welcome Back, Kotter,' 'Barney Miller' or 'Happy Days.'"

The life of an independent producer like Lear has been made more difficult, he said, by increased network competition. "The plight of the independent producer is getting worse," said Lear. "The networks make their own deals with actors, writers and producers and that makes it much more difficult for independent companise like ours.

"On the other hand, that has its own excitement. We can't afford to compete with the networks for the established names, even if we're the ones who established them, so that makes you look for new people. Jean Stapleton was an unknown entity when we found her eight years ago."

The Lear shows "All in the Family" and "One Day at a Time" remain well within the hit range in weekly ratings, but "All in the Family" is about to undergo extensive alterations because two of its stars, Rob Reiner and Sally Struthers, are leaving the show at the end of the season.

It had been thought that the characters of Archie and Edith Bunker would return next year in a revamped series called "Archie and Edith." Now it appears that the original title "All in the Family" will be used, although Lear says agreement between his company and CBS is still not final.

Lear said that in addition to movies he wants to explore "new forms" like cable television programming and "innovative public affairs" projects. A new head of production at Tandem will be announced soon.

The walls of Lear's Sunset Bouleyard office are crowded with mementoes of his years as TV's most controversial producer. These include citations from public interest groups, letters from government officials, and a "Shield of Shame" given Lear by a group called "Stop Immorality on TV." Lear tended not to duck the slings and arrows of those outraged by his programs so much as frame them and hang them on his walls.

There is also amid the clutter a framed quotation from Oliver Wendell Holmes that probably sums up Lear's show-biz philosophy: "I believe that a man must be involved in the action and passion of his time at peril of being judged not to have lived," it says. Surely it's hardly in the realm of stretching points to say that with Norman Lear's announcement yesterday, an era in television has ended.