Zoom lens design for a novel imaging spectrometer that controls spatial and spectral resolution individually

Abstract

A novel imaging spectrometer can individually control spatial and spectral resolution by using zoom lenses as the foreoptics of the system and a focusing lens. By varying the focal length we can use the focusing lens to change the spatial and spectral dimensions; with the foreoptics, however, we can change only the spatial dimension. Therefore the spectral resolution and the spectral range are affected by the zoom ratio of the focusing lens, whereas the spatial resolution and the field of view are affected by the multiplication of the zoom ratios of the foreoptics and the focusing lens. By properly combining two zoom ratios, we can control the spectral resolution with a fixed spatial resolution or the spatial resolution with a fixed spectral resolution. For an imaging spectrometer with this novel zooming function, we used the lens module method and third-order aberration theory to design an initial four-group zoom system with an external entrance pupil for the focusing lens. Furthermore, using the optical design software CODE V, we obtained an optimized zoom lens with a focal-length range of 50 to 150 mm. Finally, the zoom system with its transmission grating in the Littrow configuration performs satisfactorily as the focusing lens of an imaging spectrometer in the wavelength range 450-900 nm.

Optical schemes of spectrographs with a diffractive optical element in a converging beam

“…There are a few examples of such spectral instruments, but they use complicated zoom optical systems to change the dispersion [16].…”

Initial design method based on an iterative calculation of aberration and its application to an objective lens for imaging spectrometer

“…The Image Information Research Center of the Korea Advanced Institute of Science and Technology in South Korea has been developing dispersive push broom imaging spectrometers that can operate in the visible range. This imaging spectrometer is designed for military purposes and other applications [20].…”

Design and fabrication of a 900–1700nm hyper-spectral imaging spectrometer

“…It can be improved by using the high precision alignment techniques and the narrower slit. These data do not represent the ideal capabilities of the fabricated system, but these data represent the hyper-spectral capabilities of our system, and can be used for the calibration of pixel versus wavelength [11]. In this case, nine spectral peaks (974.75, 1181.75, 1363.25, 1442.25, 1473.25, 1520.25, 1533.25, 1622.25, 1637.75 nm) are used for the wavelength calibration.For the demonstration of the fabricated hyper-spectral imaging spectrometer system, the spectral and spatial data of three plastic bottles were measured by it.…”