RealD Inc. saw its stock tumble last week after a slow summer start.

The Beverly Hills technology licensing company announced that box office sales for its 3-D movie screens were $291 million in June, down from $345 million in May and well below analysts’ expectations. Overall box office for the April-June quarter was down 10 percent from last year.

The disappointing figures sparked analyst downgrades and an investor sell-off. Shares closed down more than 12 percent to $12.04 for the week ending July 17, making it one of the biggest losers on the LABJ Stock Index. (See page 26.)

RealD is the leading licensor of 3-D movie technology in the United States, installing its systems in theaters and then collecting a fee for each 3-D movie ticket sold.

Analysts said that although there are an increasing number of 3-D movies opening, each one is drawing a smaller percentage of audiences than previously.

For example, only 31 percent of the first-weekend box office for “Monsters University,” which opened June 21, came from 3-D sales, the lowest of any animated 3-D film in history. Only 34 percent of the first-weekend sales of “World War Z,” which opened the same weekend, came from 3-D screens, a record low for action films.

“It looks like consumers are getting increasingly choosy about which movies they’re going to pay up for,” said Eric Wold, an analyst in the San Francisco office of Westwood’s B. Riley & Co. “You see a trend of lower and lower numbers.”

Wold lowered his target price to $15 from $16.25 on July 12 after the release of the June numbers, and downgraded the rating to “neutral” from “buy” just a few weeks prior. Analysts at Dougherty & Co. in Minneapolis and Chicago’s Barrington Research also downgraded their ratings.

“With 3-D take rates deteriorating, we have less confidence in the company’s ability to grow license revenue on a year-over-year basis,” Dougherty analyst Steve Frankel wrote in his note downgrading the stock to “neutral.”

But the company still has room for optimism. Wold noted that it’s too early to tell if the sluggish numbers are a one-month blip or a sign of a larger problem.

RealD also has opportunities for growth in overseas markets, where it only controls about 40 percent of the 3-D market. It has additionally branched out into large-format theaters, announcing plans last month to launch an Imax Corp. competitor, Luxe, in Europe.

“They’re still the leader out there in 3-D,” Wold said. “They’re going to continue to take advantage of emerging markets internationally.”