A system and method are presented for measurement on an article. The system comprises an illuminator for producing light of at least one predetermined wavelength range; an optical system; a displacement arrangement; and a control system. The optical system is configured to define at least a measurement channel, and comprises a light directing assembly for directing an input light beam, propagating along an input light path from the illuminator, onto the article and directing a light beam returned from the illuminated region of the article to at least one light detector. The displacement arrangement is associated with at least the light directing assembly of the optical system, and is configured and operable by the control system to rotate said at least light directing assembly of the optical system with respect to a stage supporting the article about a rotational axis substantially normal to the stage.