Abstract: There is disclosed a partially transparent, directional viewing sheet formed of plastic material with convex and concave lenses of elliptical cross-section, preferably lenticular lenses, formed respectively on the front and back surfaces of the sheet, there being intervening spaces with convex surfaces between the concave lenses which spaces are not transparent to images and may be imprinted with an image that is viewable through the sheet from some directions. Preferably the concave lens focal length is typically about one-half of the focal length of the convex lens. Elliptical cross-section of the lenses minimizes spherical aberration and sharpens the focus. The thickness of the sheet causes focal points of the lenses to substantially coincide producing the effect of a tiny Galilean telescope.

Abstract: There is disclosed a partially transparent, directional viewing sheet formed of plastic material with convex and concave lenses, preferably lenticular lenses, formed respectively on the front and back surfaces of the sheet, there being intervening spaces with flat or convex arcuate surfaces between the concave lenses which spaces are not transparent to images and may be imprinted with an image that is viewable through the sheet from some directions. Preferably the concave lens focal length is typically about one-half of the focal length of the convex lens. Elliptical cross-section of the lenses may minimize spherical aberration and sharpen the focus. The thickness of the sheet causes focal points of the lenses to substantially coincide.

Abstract: There is disclosed a partially transparent, directional viewing sheet formed of plastic material with convex and concave lenses, preferably lenticular lenses, formed respectively on the front and back surfaces of the sheet, there being intervening spaces with flat or convex arcuate surfaces between the concave lenses which spaces are not transparent to images and may be imprinted with an image that is viewable through the sheet from some directions. Preferably the concave lens focal length is typically about one-half of the focal length of the convex lens. Elliptical cross-section of the lenses may minimize spherical aberration and sharpen the focus. The thickness of the sheet causes focal points of the lenses to substantially coincide.

Abstract: There is disclosed a partially transparent, directional viewing sheet formed of plastic material with convex and concave lenses of elliptical cross-section, preferably lenticular lenses, formed respectively on the front and back surfaces of the sheet, there being intervening spaces with convex surfaces between the concave lenses which spaces are not transparent to images and may be imprinted with an image that is viewable through the sheet from some directions. Preferably the concave lens focal length is typically about one-half of the focal length of the convex lens. Elliptical cross-section of the lenses minimizes spherical aberration and sharpens the focus. The thickness of the sheet causes focal points of the lenses to substantially coincide producing the effect of a tiny Galilean telescope.

Abstract: There is disclosed a partially transparent, directional viewing sheet formed of plastic material with lenses, preferably lenticular lenses, formed on both the front and the back surfaces of the sheet, there being on at least one of the surfaces intervening spaces between the lenses which spaces are not fully transparent and may be imprinted with an image that is viewable through the sheet from some directions. Preferably such lenses separated by non-transparent intervening spaces are concave lenses with a radius of curvature which is less than the radius of curvature of convex lenses, on the other surface, causing the concave lens focal length to be less than, typically about one-half of, the focal length of the convex lenses. The thickness of the sheet and hence the spacing between each concave lens and a corresponding convex lens causes the lenses axial spacing to be about the difference in focal lengths of the lenses producing the effect of a tiny Galilean telescope.