Spectrographic apparatus with chopper means located in the sample cell

Claim 1

An optical system for a single cell, single beam spectroscopic analyzer comprising a single light source, a single detector positioned to receive light from the light source and a single sample cell connected between the light source and the detector for containing a material to be spectroscopically analyzed and for passing light from the light source therethrough to said detector, said light source, detector and sample cell lying along an axis and having radial dimensions which are substantially the same, said system having no air gap between the light source and the detector, and a chopper means having at least one chopper element in said sample cell, a shaft in said cell on which said chopper element is mounted and extending perpendicularly to the path of light between the light source and the detector, said chopper element having a dimension perpendicular to said axis which is no greater than that of said light source, detector and sample cell, said shaft extending out of said cell, and motor means operatively connected to said shaft for rotating said chopper element around the axis of said shaft, only said motor means being outside the outer periphery of said light source, said detector and said sample cell, said chopper element being in the path of the light between the light source and the detector and having a structure for passing substantially all of the light of at least one frequency from said light source to said detector when it is in one rotational position, and for passing substantially no such light when it is in a second rotational position about 90° from said first rotational position.