LIQUID-FILLED LENSES In the world of orthodox optics, these lenses would be considered an oddity, not so much because they are liquid-lled (there have been liquid-lled camera lenses and enlarger condenser lenses) or rectangular (you can nd these, too, in many enlargers and slide projectors), but because they are basically 1D. ey are fabricated from acrylic sheet (“Perspex” in the United Kingdom, “Plexiglas” in the U.S. and European countries). is material is dicult to mold into spherical curves without a special oven and a good deal of skill, but it readily bends into perfect cylindrical surfaces. ere are many uses in holography for cylindrical lenses.