Optical Path Switch

Background

This device was created on a short timeline for R&D proof of concept for the optical design. The goal was to create a stable optical path switch without use of mechanical movement.

Optical Design

This device makes use of a λ/2 liquid crystal retarder to achieve non mechanical path switching. Unpolarized light coming into the device is split by a polarizing beam splitter. Each path is passed through a λ/4 retarder, onto a plano mirror, and back through the λ/4 retarder, flipping the path polarization. Passing back through the beam splitter redirects both paths towards the liquid crystal retarder. By mounting the liquid crystal retarder to a single polarizing filter, it could be used to choose which incoming path is allowed to pass through to the image sensor.

Mechanical Design

Mirrors and  λ/4 retarders were mounted into a quasi kinematic window frame using spring retention. These windows were mounted to a monolithic machined block using sandwiched o-rings to proved up to 2 degrees of tip and tilt alignment. A beam splitter was bonded onto a kinematic mount in the center of the monolithic block. The liquid crystal retarder and camera were each then mounted to the monolithic block.