Device for producing variable moire patterns

A device comprising, in combination:

• a plurality of substantially planar sheets, each said sheet being of a predetermined size and carrying a pattern of lines, at least one of said sheets being transparent whereby the other of said sheets may be observed therethrough;
• and
• a housing defining an interior and maintaining said sheets in continuous contact and in face-to-face relationship within said interior and permitting relative planar movement between said sheets whereby variable moire patterns are produced by the patterns of lines on said sheets, said housing including a pair of side walls disposed in spaced planes generally parllel to the planes of movement of said sheets and permitting observation of the variable moire patterns, said side walls restricting relative movement of said sheets to said planar movement, and auxiliary walls interconnecting said side walls and confining said sheets to said interior.