the reticle 80 and cassette 67 is read by a bar code reader 59 so as to confirm that the proper reticle from the proper cassette is being transported since specific reticles 80 are stored in specific reticle cassettes 67 each particular reticle desirably is returned to its original reticle cassette after use of the reticle to ensure no mixups in this regard the respective bar codes 70 of the reticle 80 and of the reticle cassette 67 are read and confirmed after making such confirmation is the reticle returned to its cassette by thus reading the bar code 70 and confirming the identity of the reticle 80 the reticle is returned to its original reticle cassette without error the bar codes 70 on the reticle 80 and reticle cassette 67 desirably are read in advance of reticle selection wherein the read data are stored in a memory and recalled during the confirmation step in other words reticles desirably remain u201c paired u201d with their respective reticle cassettes wherein after a reticle is used for exposure it desirably is returned to its original cassette 67 i e the cassette in which the reticle was stored prior to use upon reading and confirming the bar codes 70 on reticles 80 and cassettes 67 the reticle is returned reliably to its proper cassette in fig1 a the reticle libraries 64 66 are configured desirably for vertical stacking of reticles 80 on a respective stationary rack alternatively it is possible for the reticle libraries to be configured for use.