DESIGN AND EVALUATION OF AN ECHELLE GRATING OPTICAL-SYSTEM FOR ICP-OES

An echelle polychromator for inductively coupled Plasma optical emission spectroscopy (ICP-OES) was designed for use with the multichannel solid-state detector described in the companion article. The optical system has separate output sections for the UV and visible wavelength ranges, which permit high spectral resolution and high optical throughput while covering the spectral range from 167 to 782 nm. A novel component in the UV section corrects spherical aberration, cross-disperses the spectrum, and separates the UV and visible beams. A large-area echelle grating has been ruled for this system which has high diffraction efficiency and constant blaze angle across the spectrum and low stray light. Optical ray trace computations of image quality are reported, and geometrical optical throughput is compared to other systems described in the literature. Measured performance results include spectral resolution, grating efficiency, and wavelength calibration stability.