Positive pressure maintenance for sample presentation

Abstract

The invention relates to a method of presenting a non-rigid sample to a color measuring instrument, and such an instrument modified in accordance with the invention to provide proper sample presentation. Fluid under pressure is continuously supplied to the head of a conventional colorimeter having an open viewing port, to maintain a positive pressure in the head with respect to its immediate surroundings, fluid being exhausted through the open viewing port in a turbulent flow of about 10-20 cubic feet/minute. Then a solid backing structure is disposed in backing relationship with a non-rigid sample to be examined, and the sample is positioned over the viewing port with sufficient pressure applied to it to prevent the sample from moving away from the viewing port as a result of fluid flow through the viewing port. The fluid providing a positive pressure is exhausted from a location--a secondary opening about 1/10 the effective area of the viewing port--distinct from the viewing port when the viewing port is covered with the sample to be examined. The fluid flow through the instrument head prevents sample lint and dust from entering the head, facilitates removal of heat generated by the instrument, and facilitates maintenance of the sample so that a flat, distortion-free surface can be examined.