The Use of Refractive Optics for High-Fidelity Image Transfer in Spatially Resolved Spectroscopic Measurements

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Abstract
Measurements of emission intensities from spatially inhomogeneous sources often require faithful image reproduction at the entrance slit of a monochromator or spectrograph, or at some intermediate aperture. In fundamental studies, the spatial variations in intensity contain information about the basic nature of the source. For analytical measurements, the spatial resolution is required for the selection of a region in the source which exhibits the optimum analytical characteristics. Refractive optics can be used for this type of image transfer, but only if proper attention is given to the minimization or elimination of lens aberrations. We have developed a simple lens system that allows for the elimination of chromatic aberration and the control of spherical aberration. Two plano-convex fused-silica lenses with nominal focal lengths of 300 mm are mounted on translation stages that are driven in opposite directions by a right-hand/left-hand leadscrew. The performance of this system will be discussed and compared with that predicted by ray-tracing calculations. The magnitudes of various lens aberrations will be compared, and their effect on spatially resolved measurements of emission from an inductively coupled plasma will be examined.