Apparatus with diffusely reflecting hollow housing for measuring absolute reflectivity of a surface and the like

Claim 1

A REFLECTOMETER HAVING, IN COMBINATION, A HOLLOW HOUSING FORMED AS A SURFACE OR REVOLUTION AND PROVIDED WITH DIFFUSELY REFLECTIVE INNER WALL SURFACES AND WITH A PAIR OF ALIGNED APERTURES DISPOSED IN OPPOSITE WALL SURFACES THEREOF, ONE OF THE APERTURES BEING ADAPTED TO BE JUXTAPOSED TO A TEST SURFACE, THE REFLECTIVITY OF WHICH IS TO BE MEASURED, AN OPTICAL SYSTEM EXTERNALLY CONNECTED TO THE OTHER APERTURE FOR RECEIVING AND DIRECTING RADIATION REFLECTED FROM THE TEST SURFACE THROUGH THE OTHER APERTURE ALONG A PREDETERMINED DIRECTION AWAY FROM THE TEST SURFACE, FURTHER APERTURE MEANS IN THE WALL SURFACES AND PROVIDED AT A REGION OF THE HOUSING BETWEEN THE PAIR OF APERTURES, ILLUMINTING MEANS CARRIED BY THE HOUSING AND CONNECTED TO TRANSMIT RADIATION THROUGH THE FURTHER APERTURE MEANS INTO THE HOUSING, LIGHT-OBSTRUCTING MEANS SURROUNDING SAID ONE APERTURE AND IN CONTACT WITH SAID TEST SURFACE FOR PREVENTING EXTERNAL ILLUMINATION OF THE SAID TEST SURFACE BY AMBIENT LIGHT, SAID FURTHER APERTURE MEANS AND SAID ILLUMINATING MEANS BEING ARRANGED TO ENSURE THAT SAID TEST SURFACE IS SYMMETRICALLY ILLUMINATED ONLY BY RADIATION RANDOMLY AND DIFFUSELY REFLECTED FROM THE INNER WALL SURFACES OF THE HOUSING, LIGHT-OBSTRUCTING MEANS DISPOSED BETWEEN SAID ILLUMINATING MEANS AND SAID ONE APERTURE FOR PREVENTING DIRECT ILLUMINATION OF THE TEST SURFACE BY SAID ILLIMINATING MEANS, SAID OPTICAL SYSTEM HAVING TRANSDUCER MEANS DISPOSED AT THE REMOTE END OF SAID OPTICAL SYSTEM AND ALONG THE SAID PREDETERMINED DIRECTION AND MOUNTED AS A UNIT WITH THE SAID PREDETERMINED DIRECTION HOUSING TO CONVERT RADIATION REFLECTED FROM SAID TEST SURFACE TO AN ELECTRICAL SIGNAL, AND LIGHT-OBSTRUCTING MEANS LOCATED BETWEEN SAID OTHER APERTURE AND SAID TRANSDUCER MEANS FOR RESTRICTING THE RADIATION RECEIVED BY SAID TRANSDUCER MEANS ONLY TO RADIATION DIFFUSELY REFLECTED FROM THE SAID TEST SURFACE AND NOT FROM THE ADJACENT WALL SURFACES OF THE HOUSING.