Optical measurement apparatus and method of rapid measurement

An optical measurement apparatus combining confocal measurement and low-coherence interferometric measurement, the apparatus comprising:

• a Fourier domain interferometric measurement subsystem comprising a spectrometer operably coupled to a reference arm, a measurement arm and a source of electromagnetic radiation via an optical coupler, the spectrometer comprising a spectral signal generator responsive, when in use, to received reflected electromagnetic radiation;
• a confocal measurement subsystem comprising an optical scanner having a predetermined scan range for longitudinally scanning, when in use, a beam along a region to be measured;
• and
• a processing resource operably coupled to the Fourier domain interferometric measurement subsystem and the confocal measurement subsystem;
• wherein the confocal measurement subsystem shares the measurement arm with the Fourier domain interferometric measurement subsystem, the shared measurement arm comprising the optical scanner of the confocal measurement subsystem;
• the reference arm comprises a reference optical reflector element;
• and an accumulator operably coupled to the spectral signal generator-;
• a plurality of reference optical reflector elements comprising the reference optical reflector element;
• and a reflector element selection unit operably coupled to the plurality of reference optical reflector elements;
• wherein the reflector element selection unit comprises an optical switch, the optical switch being configured to select the reference optical reflector element of the plurality of reference optical reflector elements in response to a control signal.