Patent ID: 7538871

Claim:
Measurement head for a colour measurement device with an illumination arrangement including at least one light source for illumination of a measurement object located in a measurement plane (M) under an angle of incidence of essentially 45°, with a pick-up arrangement for capturing of measurement light remitted from the measurement object under an angle of reflection of essentially 0° relative to the perpendicular to the measurement plane, with a photoelectric receiver arrangement for conversion of the measurement light captured by the pick-up arrangement into corresponding electrical signals and with a brightness reference arrangement, the measurement head comprising a redirecting arrangement in association with the brightness reference arrangement positionable into and removable from a beam path between the illumination arrangement and the pick-up arrangement and located at a relatively large distance relative to the measurement plane, which redirecting arrangement, when in the beam path redirects at least some of the light originating from the illumination arrangement, into the pick-up arrangement, and the redirecting arrangement constructed as a prism shaped, frusto-pyramidal or frusto-conical, essentially transparent body with a mirrored flat base surface, a scattering layer parallel thereto and at least one lateral light entry surface inclined at 45° relative to the base surface, whereby the base surface is positioned perpendicular to an optical axis of the pick-up arrangement and the scattering layer is directed towards the pick-up arrangement, and whereby the body is dimensioned in such a way that when inserted in the beam path, the light originating from the illumination arrangement enters into the body essentially perpendicular through the at least one light entry surface and is reflected on the base surface into the scattering layer; wherein the brightness reference arrangement includes a sled that is movable in a direction transverse to the optical axis between a measurement position and a reference position; and wherein the redirecting arrangement is mounted on the movable sled.