On the Application of Integral Field Unit Design Theory for Imaging Spectroscopy

Abstract

Integral field spectroscopy is a powerful tool for astronomical observation, of particular importance to large telescopes. In this paper, different techniques for the design and construction of integral field units (IFUs) are described, concentrating on the use of lenslet arrays coupled to fibers. The theory of the design of the foreoptics, lenslets, and fibers is presented. The effects of the fiber oversizing and focal ratio degradation on IFU performance are described. A mathematical model is developed that can be used to calculate the optimized fiber core size according to the required coupling efficiency. A figure of merit for the IFU system is also derived, which can be used to estimate and compare the performance of different IFU systems. Finally, a design example is given to demonstrate the applications of this theory.

Snapshot advantage: a review of the light collection improvement for parallel high-dimensional measurement systems

“…There is a remarkable variety of architectures available for full-throughput imaging spectrometers, among which are (in order of provenance) computed tomographic imaging spectrometry 20 (CTIS), fiber-reformatting imaging spectrometry (FRIS), 21,22 integral field spectroscopy with lenslet arrays 23 (IFS-L), integral field spectroscopy with image slicing mirrors 24 (IFS-S), image-replicating imaging spectrometry 11 (IRIS), filter stack spectral decomposition 25 (FSSD), coded aperture snapshot spectral imaging 26 (CASSI), image mapping spectrometry 27 (IMS), and multi-spectral Sagnac interferometry 28 (MSI). See Fig.…”

Physico-chemical spectroscopic mapping of the planetary nebula NGC 40 and the 2d_neb, a new 2D algorithm to study ionized nebulae

“…In recent years a new tool for obtaining spectroscopic data has been developed. The Integral Field Unit (IFU) is a tool that utilizes a square array of lenses remapped to a slit and then imaged through a spectroscope to obtain spatially resolved data (Ren & Allington‐Smith 2002). Tsamis et al (2008) were the first to use this tool to investigate the spatial variations of PN parameters.…”

ULTIMATE: a deployable multiple integral field unit for Subaru

“…Most fundamentally, a large lenslet size compared to the fibre core diameter minimises shifts in the pupil image and geometric focal ratio degradation. 28 Secondly, arrays of 72 µm lenslets are not readily available from manufacturers and are likely to be expensive and to pose a significant risk in meeting the required specifications. In particular the fill factor for microlens arrays with a pitch < 100 µm will be < 80%.…”