Design and manufacture of compact long-slit spectrometer for hyperspectral remote sensing

In order to increase the swath and reduce the volume of hyperspectral remote sensing instruments, the compact, long-slit Wynne-Offner spectrometer is detailedly investigated. Through tracing the chief ray, expressions of astigmatism are deduced, and the astigmatism of Offner and Wynne-Offner spectrometers are compared. It is pointed that the anastigmatic circle region of Wynne-Offner spectrometer is larger than that of Offner spectrometer, and the former is more suitable for long slit. Design procedure of the Wynne-Offner spectrometer is given, and we then design a compact long-slit VNIR spectrometer. It works in the wavelength range of 0.5-1.0 mu m with a spectral resolution of 5 nm, and its slit length is 61.44 mm. Results show that our design has much more compact structure and higher imaging quality than classic Offner spectrometers. Prototype of this spectrometer is also manufactured. Image quality of the prototype is close to the diffraction limit with low spectral and spatial distortions. Such Wynne-Offner spectrometer has the advantages of long slit, compact structure and high imaging quality, and they are really suitable for remote sensing missions requiring wide swath and small size.