A new headset from Nikon, released in Japan, is a completely self-contained entertainment center. Media-playback software and up to eight gigabytes of memory are built in, and with two AA batteries installed, the headset weighs less than a pound. According to Nikon, the adjustable eyepiece simulates a 50-inch TV screen viewed from about 10 feet away. The key to the picture quality is a light-diffraction grating that emerged from the company's research on camera lens design. Data can be loaded onto the headset through either a USB cable or a Wi-Fi connection.

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