January 24, 2017 - Six eyepiece design files posted today.

Just catching up with some files I missed earlier.

April 25, 2015 - 45 eyepiece design files posted today.

These files, up until patent #8,531,774, represent a more-modern sampling of eyepiece designs. The newer designs include a lot of design features, such as aspheres and high-index glasses, that weren't readily available at the time of the designs from Cox. The newer designs also include many applications, such as virtual reality, that weren't anticipated at the time of the older designs.

When compared to new designs that probably have similar design constraints, the old designs hold up surprisingly well. For example, compare US02549158-4, a 1947 design by Ludwig Bertele, to US05877900-1, a 1997 Nikon design. Both designs have efl=25mm and are about f/3 and have an eye relief of about 18mm. The Bertele design places the reticle very close to the last glass element, whereas the Nikon design allows for 8mm separation. The Berele design uses six pieces of glass; the Nikon design, five. The Bertele design is also 23% longer than the Nikon design. I haven't done a tolerance analysis, but the Nikon design looks more stressed to me, with large angles of incidence on the negative surface of the doublet. The Bertele design makes little use of high index glasses; five of the six glasses have n<1.6, and only one has n>1.7. The Nikon design makes heave use of high index glasses; one of five glasses has n<1.6, and all others have n>1.7. Despite this disadvantage in materials, the Bertele design performs relatively well. Comparing RMS spot size vs/ field of view at EDP=8, max field =27deg, shows essentially equivalent axial performance. Full field performance for the Bertele design is meaningfully worse; 129um RMS vs. 107um RMS for the Nikon design.

Another design of note is 4720183, by Don Dilworth. Don has been selling an excellent lens design code, Synopsys, for many years; although I've never met him, he seems like a treasure for our community. He hasn't patented many of his designs, but this eyepiece seems like something special. It has a +-45 deg FOV and is meant to correct the coma from parabaloid mirrors. Looking through a telescope with this eyepiece must be something special.

November 19, 2014 - 67 design examples from Cox posted

67 files, in Oslo and Zemax format are uploaded. The files are based on Cox’s “A system of optical design,” Type 2. The designs are quite dated, from 1957 and older; but they can be quite useful as starting points for new designs or benchmarks for design comparisons. More analysis of the Cox-based design files can be found on the Photographic primes page.

Summary of designs


Design files