Patent ID: 7221814

Claim:
A surface profiling apparatus ( 10 , 60 , 80 , 102 , 120 ) comprising: an optical waveguide including a plurality of sensor sections, each sensor section comprising a respective optical waveguide grating curvature sensing device, each optical waveguide grating curvature sensing device comprising at least one long period grating ( 12 , 14 , 16 ); and optical interrogation means operable to interrogate the optical waveguide grating curvature sensing devices to determine the curvature experienced by each device, the optical interrogation means comprising: an optical source optically coupled to one, input, end ( 18 a ) of the respective optical waveguide and being operable to generate a narrow spectral bandwidth optical signal at a wavelength within the spectral range of an optical waveguide grating curvature sensing device to be interrogated, the optical signal being wavelength-modulated at a modulation frequency; and optical detection means optically coupled to the other, output, end ( 18 b ) of the optical waveguide and being operable to measure the amplitude of a detected optical signal at least one harmonic of the modulation frequency in order to detect changes in the spectral transmission profile of the optical waveguide grating curvature sensing device being interrogated and to thereby determine the curvature experienced by the optical waveguide grating curvature sensing device; whereby the sensor sections are couplable to a surface to be profiled, and a profile of said surface is constructed from the curvatures sensed by the optical waveguide grating curvature sensing devices.