Densitometer

Claim 1

A densitometer which has a double structured lens barrel comprised of an inner cylinder and an outer cylinder extending coaxially therewith in which an annular light passage is formed between the inner and outer cylinders, a flux of light between the cylinders is condensed on the front face of a sample through a condenser optical system provided between said cylinders when reflection optical density of the sample is measured, the back face of the sample is illuminated with a flux of light from a light source located under the sample when transmission optical density of the sample is measured, and the light reflected by or transmitted through the sample is guided to a photodetector through said inner cylinder, the improvement comprising a fixed portion and a movable portion which constitute said double structured lens barrel, said movable portion being slidably engaged with the fixed portion and movable in the direction of the optical axis of lenses installed therein, said movable portion including an inner movable cylinder, an outer movable cylinder coaxially extending therewith and extending downward therebeyond and having an open lower end, said fixed portion including an inner fixed cylinder and an outer fixed cylinder extending coaxially therewith, said inner and outer movable cylinders of said movable portion being slidably engaged with said inner and outer fixed cylinders of the fixed portion, a condenser optical system provided between said inner and outer movable cylinders for normally condensing a flux of parallel light therebetween to a point at the center of said open lower end of the outer movable cylinder regardless of the position of the movable portion, a collimator lens provided in said inner movable cylinder which has a focusing point at said point at the center of the open lower end of the outer movable cylinder, and a light source chamber which includes a light source for reflection density measurement connected with the fixed portion, said light source chamber including a light source and a collimator lens having an optical axis being perpendicular to the optical axis of said collimator lens in said inner movable cylinder and means for moving said open lower end of the outer movable cylinder into contact with the surface of a sample during the measurement of the optical density of the sample.