High Quality Content by WIKIPEDIA articles! An optical computer mouse or "optic mouse" uses a light-emitting diode and photodiodes to detect movement relative to a surface, unlike a mechanical mouse which has a ball which rotates orthogonal shafts which drive chopper wheels for distance measurement. The earliest optical mice detected movement on pre-printed mousepad surfaces, whereas the modern optical mouse works on most opaque surfaces; it is unable to detect movement on specular surfaces like glass. Laser diodes are also used for better resolution and precision. Battery powered, wireless optical mice flash the LED intermittently to save power, and only glow steadily when movement is detected.