The imaging magnetograph eXperiment for the SUNRISE balloon Antarctica project

13 pages, 8 figures.-- Published in: "Optical, Infrared, and Millimeter Space Telescopes" [Section: Solar], edited by John C. Mather.-- Contributed to the conference with same title, Glasgow, Jun 21, 2004.Final full-text version available Open Access at: http://www.iaa.es/~jti/publications/SPIE2Valentin.pdfThe SUNRISE balloon project is a high-resolution mission to study solar magnetic fields able to resolve the critical scale of 100 km in the solar photosphere, or about one photon mean free path. The Imaging Magnetograph eXperiment (IMaX) is one of the three instruments that will fly in the balloon and will receive light from the 1m aperture telescope of the mission. IMaX should take advantage of the 15 days of uninterrupted solar observations and the exceptional resolution to help clarifying our understanding of thesmall-scale magnetic concentrations that pervade the solar surface. For this, IMaX should act as a diffraction limited imager able to carry out spectroscopic analysis with resolutions in the 50.000-100.000 range and capable to perform polarization measurements. The solutions adopted by the project to achieve all these three demanding goals are explained in this article. They include the use of Liquid Crystal Variable Retarders for the polarization modulation, oneLiNbO3 etalon in double pass and two modern CCD detectors that allow for the application of phase diversity techniques by slightly changing the focus of one of the CCDs.This project is funded by the Spanish Programa Nacional del Espacio under project ESP2003-07735.Peer reviewe