  The Dark Energy Spectroscopic Instrument (DESI) is under construction to
measure the expansion history of the Universe using the Baryon Acoustic
Oscillation technique. The spectra of 35 million galaxies and quasars over
14000 square degrees will be measured during the life of the experiment. A new
prime focus corrector for the KPNO Mayall telescope will deliver light to 5000
fiber optic positioners. The fibers in turn feed ten broad-band spectrographs.
We describe the DESI corrector optics, a series of six fused silica and
borosilicate lenses. The lens diameters range from 0.8 to 1.1 meters, and their
weights 84 to 237 kg. Most lens surfaces are spherical, and two are challenging
10th-order polynomial aspheres. The lenses have been successfully polished and
treated with an antireflection coating at multiple subcontractors, and are now
being integrated into the DESI corrector barrel assembly at University College
London. We describe the final performance of the lenses in terms of their
various parameters, including surface figure, homogeneity, and others, and
compare their final performance against the demanding DESI corrector
requirements. Also we describe the reoptimization of the lens spacing in their
corrector barrel after their final measurements are known. Finally we assess
the performance of the corrector as a whole, compared to early budgeted
estimates.
