Long working distance objective lenses for single atom trapping and   imaging
  We present a pair of optimized objective lenses with long working distances of 117~mm and 65~mm respectively that offer diffraction limited performance for both Cs and Rb wavelengths when imaging through standard vacuum windows. The designs utilise standard catalog lens elements to provide a simple and cost-effective solution. Objective 1 provides $\mathrm{NA}=0.175$ offering 3~$\mu$m resolution whilst objective 2 is optimized for high collection efficiency with $\mathrm{NA}=0.29$ and 1.8~$\mu$m resolution. This flexible design can be further extended for use at shorter wavelengths by simply re-optimising the lens separations. 
J. D. Pritchard, J. A. Isaacs and M. Saffman
physics.optics physics.atom-ph