Abstract: An ophthalmic device comprising superposed pairs of light polarizing elements, one pair of such elements being fixed and the other pair being rotatable with respect to the fixed pair to provide a variable light transmission feature. The fixed pair of elements is retained by a frame member having an arcuate peripheral portion which engages a rotatable light polarizing element biasing means which is fixedly attached to each rotatable light polarizing element and prevents substantial axial movement of the rotatable light polarizing element.

Abstract: An interlock mechanism is provided for use as an adjunct with a camera having a shutter and a lanyard operated film advancing and processing system which utilizes a film cassette contaning, in stacked relationship, a dark slide and a plurality of self-processable film units. Each film unit is adapted to be exposed and then processed in a consecutive sequence. The interlock mechanism functions to preserve the proper operating sequence and prevents the camera user from performing anomalous operations which could result in film losses due to the processing of non-exposed film units.