A novel mothod of intensity modulated optic displacement measurement is described. A LED is used as source. The ray projects from the first SELFOC lens, then is reflected by the mirror and enters into second SELFOC lens. When the mirror has some little displacement, the ray entering the second SELFOC lens is modulated. The value of displacement is determined according to the change of light intensity with photocell. A resolution of 1×10-9 m is attainable with this metering device. The principle can be also used in the measurement of pressure and vibration.