G09F—DISPLAYING; ADVERTISING; SIGNS; LABELS OR NAME-PLATES; SEALS
G09F19/00—Advertising or display means not otherwise provided for
G09F19/12—Advertising or display means not otherwise provided for using special optical effects
G09F19/18—Advertising or display means not otherwise provided for using special optical effects involving the use of optical projection means, e.g. projection of images on clouds