Concept Study of On-Instrument Wavefront Sensors (OIWFS) for the TMT IRIS Science Instrument D. Loop, M. Fletcher, V. Reshetov, R. Wooff, J. Dunn, G. Herriot, A. Moore, R. Dekany, A. Delacroix, R. Smith et al. (7 more) Published online: 24 February 2010 DOI: 10.1051/ao4elt/201005013