P.  Geißler and Jähne, B., ?One-image depth-from-focus for concentration measurements?, in Proc. ISPRS Intercommission Workshop `From Pixels to Sequences', Zurich, March 22 - 24, 1995, In Int'l Arch. of Photog. and Rem. Sens., 1995, vol. XXX-5W1, p. 122--127.