NEW YORK: Tired of hearing other people’s cellphone conversations? It may get worse. Soon you may have to watch their favorite television shows and YouTube videos, too, as they project them onto nearby walls or the seat-backs of commuter trains.

Small digital projectors are in the works. These devices, when plugged into cellphones and portable media players, will let consumers beam video content from their hand-held devices to the closest smooth surface – entertaining themselves, annoying their neighbors and possibly contributing to a new warning sign: “No Projectors in This Area.”

The microprojectors, still in prototype stages, use light-emitting diodes, lasers or a combination of the two to cast a display in darkened spaces of up to 50 or 60 inches wide, or 130 to 150 centimeters, and perhaps even wider, and of 7 to 20 inches wide when there is ambient light.

Digital projectors were once bulky. These new models are small enough to fit into the pocket of consumers who want a big-screen experience from a small-screen device. Some of the models are expected to be on the market by the end of this year, if not sooner.

Prices have yet to be announced. But Matthew Brennesholtz, an analyst at Insight Media, a marketing research firm in Norwalk, Connecticut, said he thought that the projectors would initially cost about $350, then drop quickly to less than $300.

The projectors may be particularly useful for business presentations: showing a product video to small groups, for example.

No pre-meeting coordination would be needed to arrange for a screen. Instead, a patch of wall in a cubicle or at a restaurant could serve for an impromptu presentation. In a pinch, a manila folder or even a napkin would work.

Carolina Milanesi, a research director in London for Gartner, the research firm, said she thought that the microprojectors were most likely to appeal to business travelers who, for example, could use them to beam PowerPoint shows from their smartphones.

But Milanesi is dubious about the likelihood of consumers’ using them in public, because they could so easily be read by others. “I hate it even when I am on the subway and the guy next to me is reading my paper,” she said.

The projectors will first appear as free-standing companion units to cellphones and other devices, Brennesholtz said, connected to them by standard cables. Later, the projector modules will be directly embedded in phones, (Images) as cameras are today. About 16 manufacturers are working on miniprojectors, he said.

Insight Media forecasts a substantial and fast-growing market for the technology. “We anticipate total sales of more than $2.5 billion by 2012 for the companion models,” Brennesholtz said, and $1 billion in revenue for projector modules that are integrated into cellphones and other devices.

Cellphone service providers have been a driving force behind miniprojector development, said Jinwoo Bae, business team leader for Iljin DSP, a South Korean company that is working on a prototype.

“Revenue growth from voice service is becoming saturated,” Bae said, “so telecom service providers are looking for new revenue from video content.”

Iljin DSP’s microprojector, which will be marketed and distributed by SK Telecom, a large wireless operator in South Korea, projects images that are 7 to 60 inches wide, depending on a room’s lighting; the device’s light source is a combination of lasers and LEDs. The lithium-ion battery lasts about two hours, Bae said.

The company is also building a projector engine to be incorporated in cellphones. “We need to reduce the power consumption” of the module, Bae said. “A stand-alone projector can have its own battery, but modules integrated into a mobile phone use the phone’s battery,” limiting the amount of power than can be drawn, he said.

A miniprojector engine is now being manufactured by 3M, the U.S. technology company. It will be sold within a stand-alone projector offered by Samsung this year, said Mike O’Keefe, marketing manager for 3M’s mobile projection technology. The projector, called the Samsung MBP-100, connects to devices like MP3 players that have video output capacity.

Brennesholtz, of Insight Media, was shown a model of the Iljin DSP projector at a restaurant in New York when he met with executives from the company. “I’m not sure what the other diners thought about seeing a Korean sitcom projected on the ceiling of the restaurant,” he said.

As it turned out, there was too much ambient light for the image to look good on the ceiling. “But on a napkin, or on the cover of a box,” Brennesholtz said, “it looked fine.”