Real-time radius compensation method and measuring head device based on LED (light-emitting diode) annular light

The invention discloses a real-time radius compensation method and a measuring head device based on LED (light-emitting diode) annular light. A measured free curved surface near measuring balls of a contact type measuring head is approximated as a microplane, the LED annular light is projected onto the microplane to form an elliptic projection line, a CCD (Charge Coupled Device) camera is utilized to capture the elliptic projection line, the unit normal vector of the microplane is worked out according to the included angles between the long axis and the short axis of the ellipse and the X axis and the Y axis of the coordinate system of the measuring head and the length ratio of the long axis to the short axis, the outward normal direction of the unit normal vector is chosen, and finally, the outward normal direction of the unit normal vector is utilized to carry out real-time radius compensation on the contact type measuring head. The measuring head device comprises a contact type measuring probe, a measuring probe holder, an LED emitter, a focusing reflector, the CCD camera, an organic glass ring, an annular bracket and other fittings. The method is simple, and can carry out the real-time radius compensation of contact type measurement data; and the device has a simple structure, and is easy to put into practice. The device can be applied on portable coordinate measuring machines, and has a good reverse measurement effect on slowly changing free curved surfaces.