Head for measuring reflectance

Claim 1

A measuring head for measuring diffusely reflected light from the reflecting surface of a reflecting material while minimizing the measurement of regularly reflected light from the reflecting surface, the measuring head comprising: a transmitter including a transmitter axis; a receiver defining a receiver axis and a receiver aperture angle ε, the receiver aperture angle ε defining a light acceptance cone; a first light guide having a first diameter; a plurality of second light guides each having a second diameter; the transmitter including a chosen one of the first and second light guides while the receiver includes the other of the first and second light guides; the transmitter being adapted to create a conically diverging transmitted light beam to create an illuminated area on the reflecting surface, the transmitted light beam having a transmitter aperture angle u, the receiving being adapted to accept light reflected from the reflecting surface along the light acceptance cone; the transmitter and receiver alternately positioned at an equal spacing from each other in the form of a matrix; the receiver positioned substantially outside of a cone of regularly reflected light from the reflecting surface to minimize receipt of regularly reflected light; the receiver aperture angle being substantially equal to the sum of a first angle α and a second angle δ, the second angle δ being equal to or greater than the transmitter aperture angle u, wherein the first angle α is an angle between reflected light rays coming to the receiver and a line normal to the reflecting surface and wherein the second angle δ is an angle substantially equal to or greater than the transmitter aperture angle u; and the receiver aperture angle ε being sized and the receiver being positioned relative to the reflecting surface so that the light acceptance cone of the receiver encompasses substantially the entire illuminated surface to maximize receipt of diffusely reflected light.