Abstract: A number of luminous sources (4) are arranged in a ring-shaped manner in a plane and individually and successively emit, in a rotating manner on the ring, an incident beam oriented toward the axis (5) of the ring and diagonal to this axis at an angle that is not a right angle. This beam is reflected by the object (2) placed essentially along the axis (5), whereupon it is received by one of the photodetectors (8a, 8b, 8c) situated in a plane parallel to the ring of sources. The presence of a shape defect of a surface irregularity or of a variation in color is determined by modulating the energy received by the photodetectors. This measure provides a very good resolution of the successive lighting of very small areas of the object surface.

Abstract: Disclosed is a device for absolute, high-speed measurement of a diameter of an optical fiber and for detecting defects in the fiber, comprising two complementary signal processing systems including first and second sensors and first and second processing boards wherein angular calibration of the sensors is performed by directly deducing the absolute diameter of the fiber from the equations (4) and (7): f(n,?)=sin(?/2)+[n2+1?2*n*cos(?/2)]1/2 ??(4) M=[A/(B+?)]*[1+Sin2{N(D,?)*?+?}], ??(7) in which n represents N1 index of a substance, ? is a measurement angle, D is outer diameter, A is a signal amplitude in volts, B is a measurement angle, and M is a signal amplitude.