~LSST Accurate Star Simulator Optic (LASSO)~

An f/1.2 lens that emulates the LSST for the case of a single star. The optical design is catadiaptric: A Schwarzschild Objective modified with a meniscus lens at the output, which compensates the spherical aberration introduced by a flat window as on a vacuum chamber. In appears it's similar to a Maksutov Cassegrain but is really quite different (the small mirror silvered onto the meniscus lens is the primary mirror). Optics fabricated at Optimax, mirror coatings done by Spectrum Thin Films, machining done was in-house.


Academic poster


Nice photo of the complete assembly mounted to an XY translation stage. Fiber feed is visible. Note black spot on outer surface of lens which is a ghost suppression feature (silvered surface on inside not viisble).

ray trace
Optical design. Based on a Schwarzschild Objective, the key difference being the addition of L1.

Stray light analysis. Led to addition of "ghost suppression spot" visible here.

Measured performance (right side plots) as compared to an f/1.8 point projector (left side plots). Note diffraction rings from obscuration (bottom right). Images were reimaged and magnified with a microscope objective.

mechanical cross section
The mechanical design. Light enters from the left (nominally a point source).

Aluminum parts before anodizing.

kinematic secondary mirror support
Secondary mirror and kinematic mounting scheme. Unlike a telecope the large mirror is the secondary.

Another view of final assembly.