Page:US patent 1682572.pdf/5



This invention relates: to optical instruments and particularly to spectrophotometers and the component parts thereof, Although there is an extensive field for the application of such instruments in the industries and many different types thereof have been devised, their use has practically been limited to research laboratories because most of the types heretofore produced could be used successfully only by those having an advanced scientific training. While such instruments as were adapted to the skill of men having only average training could be manufactured and sold only at a relatively high price.

In order that spectrophotometer be suitable for industrial purposes and for the average college laboratory it must meet the following requirements: 1st, The instrument must be susceptible of being manufactured and sold at a relatively low price; 2nd, the construction of the instrument must be based not only on correct scientific but also sound mechanical principles and design so that the results of observations will be within the required limits for precision and accuracy; 3rd, it must be sturdy and durable; 4th, the movable parts of the instrument must be so constructed that settings and readings can be made quickly and easily with a minimum of exertion on the part of, and fatigue to, the operator; 5th, the results of observations made with the instrument must be directly obtainable from suitable indicia without necessitating mathematical computations to obtain the required data, so that such data can be obtained and recorded by persons of average skill; and 6th, the construction of the instrument and particularly what may be termed the mechanical parts thereof, as distinguished from the optical elements such as lenses and prisms, must be such that the necessity for mathematical accuracy in the machining of the such parts will be obviated.

It is the principal object of this invention to provide a spectrophotometer which will fully meet the above enumerated requirements.

A further object is to improve upon the construction of the spectrometer and photometer which not only form component parts of a spectrophotometer, but are also separately adapted for extensive use.

These and other objects will appear more fully to one skilled in the art to which the invention relates, from the following more detailed description and by reference to the accompanying drawings forming a part hereof, and wherein is a diagrammatic plan view of a portion of a spectrophotometer embodying my invention showing the arrangement of the members;  is a diagrammatic side elevation of the optical system; Figs. and are diagrams of a portion of the spectrometer showing different positions of the optical wedge;  is a diagrammatic view of the photometric field; Figs. and are a side elevation and a plan respectively of my improved instrument;  are views similar to Figs. and showing a different form of the invention and  is a detail side elevation of an adjusting device for use with the form of construction shown in  inclusive.

The instrument will first be described by reference to the diagrammatic views of inclusive in order that the underlying scientific principles of the construction may be more readily understood.

As shown in the instrument consists of a photometer designated generally by the reference character A, and a spectrometer designated by the reference character B. A portion of the radiant energy or light from any example, the lamp L reflected by the reflecting surfaces R$1$, R$2$, is directed by the prism P$1$, in two substantially parallel juxtaposed beams through the entrance slit S$1$ of  the collimator C and passes through the collimator objective L$1$. The parallel beams as they pass through the dispersion prism P$2$ are dispersed so that, in accordance with the well known properties of such prisms, the rays of different color present in the light beams will be deviated at different angles according to the wave length or frequency of each particular light ray; the resulting dispersed beam being brought to a focus at the ocular slit S$2$ of the telescope T by the telescope lens or objective L$2$.

A bi-prism P$3$ is interposed between the dispersing prism P$2$ and the telescope objective L$2$ to form a divided field of the type shown in ; one half of the field as for