Reflectance probe

Claim 1

Apparatus for measuring the value of the directional spectral hemispherical reflectance and spectral radiance of the surface of a target when not engaging but being spaced from the target, said target being heated to emit thermal radiation at wavelengths falling within a specified wavelength band, said apparatus comprising: a hollow elongated member having a longitudinal axis and first and second opposite ends, the area of the first end being relatively large relative to that of the second end, one of said first and second ends being open, the member having an inner chamber extending between the ends and having an inner surface adapted to reflect light falling within said wavelength band, said member when the apparatus is in use being positioned with the open end adjacent but spaced from a selected portion of the surface of the target and the longitudinal axis being oriented essentially normal to a region on the selected surface which would be engaged by a line coincident with the axis and sufficiently extended outwardly from the first end; first means for directing a beam of light falling within said band within at least a portion of the chamber and outward through the open end to impinge upon said selected surface region, a portion of the beam being reflected after said impingement backward through the open end into the chamber, the reflected light which strikes the inner surface of the chamber being directed backwardly within the chamber, from the open end toward the other end, a portion of the emitted radiation being directed into the chamber and guided to the other end; second means responsive to at least a portion of the backwardly directed light to derive therefrom a first electrical signal which is a measurement of said reflectance value; and third means responsive to the directed portion of the thermal radiation to derive therefrom a second electrical signal which is a measurement of the value of said thermal radiation.