Hundreds of technology firms came together in Japan Tuesday to showcase the latest in high-end gadgetry, including wafer-thin speakers and a ring that can monitor your heart rate.

The five-day Combined Exhibition of Advanced Technologies (Ceatec) technology fair in Chiba near Tokyo features more than 600 companies from 15 countries and regions showing new gadgets.

Musical instrument maker Yamaha had on show its prototype TLF speaker that can be displayed as a thin, light and flexible poster with a cloth cover.

The 1.5-millimetre-thick speaker sends directional "flat-wave" sounds that do not deviate once emitted, meaning that sounds can only be heard when the listener is standing in front of it.

Yamaha aims to sell the technology early next year, company spokesman Yusaku Shibuya said, adding: "This can function as a convenient advertising poster, which can be rolled up and carried around."

He said it would first be aimed at corporate users before being released to ordinary consumers with potential benefits for those living in smaller houses who do not want to disturb roommates with music.

Fujitsu Ltd. offered its "omniview" system for automobiles, which uses small cameras and imaging software to give drivers a 360 degree, 3D view of the car's surroundings. Some Toyota vehicles adopted the system earlier this year.

Electronics parts maker Murata Co. was displaying a ring that measures heart speed and blood-oxygen levels and can transmit data to a cellphone or other device to trigger an alarm if the pulse rate is too high.

NTT DoCoMo's new "augmented reality" applications use virtual images to enhance everyday experiences, Japan's leading mobile phone carrier said.

"Cellphones are a bridge between virtual reality and the world around you," said Manabu Ota, a DoCoMo official for consumer mobile device development.

Among applications the firm is developing is a function giving shoppers an enhanced view of a chosen object to see if it fits in the home before buying.

DoCoMo also showed a prototype "AR Walker" system -- made with optical equipment maker Olympus -- which requires users to wear special glasses that give a view overlaid with information on directions and local recommendations.