Abstract: The invention provides an imager panel subassembly for use in an optical projection system. The subassembly includes a reflective imager panel, such an LCoS microdisplay, for spatially modulating an optical beam incident upon a front surface thereof for producing an image. An optically transparent birefringent trim retarder is disposed in front of the front surface of the imager panel for enhancing the image contrast, and for protecting the imager panel from the outside dust. The subassembly further includes a spacer separating the imager panel and the trim retarder for forming an enclosed airspace therebetween, and adjustable coupling means for securely coupling the trim retarder and the imager panel together in a pre-determined relative position independent of the optical projection system, so that to allow rotation of the trim retarder relative to the imager panel while maintaining dust-tight sealing of the enclosed airspace.