Patent ID: 7483094

Claim:
An optical sheet comprising cylindrical lens elements which have a hyperboloidal face or a paraboloidal face and are provided successively in a row on one of principal faces of said optical sheet, wherein a Z axis is taken in parallel to a normal line direction to said optical sheet and an X axis is taken in a direction of the row of said cylindrical lens elements, and wherein a cross sectional shape of said cylindrical lenses satisfies the following expression: Z=X 2 /( R +√{square root over ( )}( R 2 −(1+ K ) X 2 )) where R is a radius of curvature of a distal end vertex, and K is a conic constant; and convex portions having a height equal to or greater than 0.20 μm from an average central plane are further provided on the other principal face side opposite to the one principal face on which said cylindrical lens elements, wherein a density of said convex portions is equal to or higher than 70/mm 2 but equal to or lower than 500/mm 2 .