A prototype of a microlensed hyperspectral imager for solar observations

Abstract

Context. When spectropolarimetric data are recorded at high spatial, spectral, and temporal resolution, the quality of the data is generally limited by the signal-to-noise ratio.Aims. We present a prototype of an integral field spectrograph for solar observations. This prototype overcomes the limitations of traditional solar instrumentation and captures the spectral information for all points in a given field of view without scanning, in order to optimize the efficiency and to minimize spectral and spatial crosstalk.Methods. The prototype was executed as a plug-in for the TRIPPEL spectrograph at the Swedish 1-meter Solar Telescope (SST) and uses an array of microlenses to shrink each image element, so that dark space is created in between. The light is then dispersed in this space, allowing for the independent detection of each spatio-spectral image element on a 2D detector.Results. The prototype was built and installed at the SST, yielding several good-quality data sets. These data sets were used to determine the imaging performance and efficiency of the prototype.Conclusions. Although the instrument required high-accuracy optics, the transparency of the prototype was found to be about 25%, and the straylight properties were found to be typical for spectrographic instruments.