359 / | HD | OPTICS: SYSTEMS (INCLUDING COMMUNICATION) AND ELEMENTS |
642 | DF | LENS {32} |
726 | DF | .~ With reflecting element {3} |
727 | DF | .~.~ Including concave or convex reflecting surface {2} |
730 | .~.~.~ Reflectors in series {1} | |
731 | DF | .~.~.~.~> With concave and convex reflectors in series |