Optimum viewing results require precision metal pinholes made in an ultra thin black substrate. Viewing instructions are printed on the rear of the device.
H is the distance from the variable aperture pinhole to the illocal frame.
Frames must be optically matched. The optical axes must be constrained to move in a horizontal plane while providing independent movement of d and the distance between the illocal frames, d i . This represents three degrees of freedom. There are many ways to achieve this mechanical requirement. All that one sees are the frames.