Design method for engineering the initial structure of a spectrometer

Abstract

A well-considered initial structure plays a key role in the design of an exceptional spectrometer. Previously, the design method for the optical initial structure (MOIS) that has only focused on the optical properties based on simple imaging formulas and coma-free conditions has been extensively researched. However, as the shape and size of any optical component are not considered for the MOIS, the optical parameters before and after optimization are very different, which results in a loss of reference value of the initial structure. In order to address the aforementioned issues, a more efficient design method for engineering initial structure (MEIS) of the spectrometer is proposed, where not only the above optical properties are considered but also the relative position and size of any optical component in order to avoid the interference between the optical components. For the MEIS, three important anti-interference conditions between components are deduced through ray tracing, and the relevant imaging formulas are derived by geometric optics, which leads to the rapid calculation of component parameters and the acquisition of an initial structure satisfying the corresponding design requirements by setting reasonable spacing margins. To verify the validity of the MEIS, a wide-band high-resolution spectrometer system with a large CCD Toucan 216 is designed within a wavelength range of 700–1000 nm and a resolution of 0.5 nm. Compared with the MOIS, the positions of each component in the MEIS are more rationalized, which significantly eliminates the complex optimization processes. For the MEIS, changes only in the position of the image plane occur with minimal variations in the axial and vertical wheelbase (less than 0.5 mm) as well as the deflection angle (only 0.5°), with favorable evaluation indices. The MEIS has an important reference value for the rapid and efficient design of excellent spectrometers.