Frames are used to hold and/or position components in precise positions in a prism assembly. The frames may be constructed using any of side caps, air gaps, recesses, and hold either a single or multiple planar components. The frames are, for example, immersed in liquid filled channels between adjacent faces of beamsplitters in the prism assembly. The planar components themselves may include waveplates, optical flats, spacer glasses, retarders, Color Selects, substrates, or any other components of the optical device. The planar components may themselves include multiple layers (e.g., polarizers, dichroics, etc). In one embodiment, a polarizer and an air gap are provided. The invention increases precision, lowers cost, and improves quality (e.g., contrast ratio) of any number of devices, but is particularly applicable to Liquid Crystal on Silicon (LCOS) and other microdisplay based projection systems such as High Definition (HD) Rear Projection Televisions (RPTVs).