Patent ID: 6900945

Claim:
A lenticular lens sheet for use in a rear projection screen that allows imaging light emitted from an image source, the imaging light being incident on a rear of the screen, to emerge toward a viewer's side, comprising: a plurality of lens elements of incidence arranged on an incidence side; and a plurality of lens elements of emergence arranged on an emergence side, wherein a light that has passed through each of the lens elements of incidence converges via a protruding apex of a corresponding lens element of emergence; a lens plane of a center portion of each of the lens elements of emergence, a width of the center portion being a half of a total lens width, is in a shape defined by a curved line fulfilling the conditions expressed by the following numerical formulae (1) to (4): y=a×b −x −e (− L /4 ≦x≦ 0) (1), y=a×b x −e (0 ≦x≦L /4) (2), 3.0×10 −4 <a <3.8×10 −4 (3), and 1.0×10 24 <b <1.0×10 25 (4); a lens plane of each side portion of each of the lens elements of emergence, a width of the each side portion being a quarter of the total lens width, is in a shape defined by a curved line fulfilling the conditions expressed by the following numerical formulae (5) to (8): y=c×d −x −e (− L /2 ≦x≦−L /4) (5), y=c×d x −e ( L /4 ≦x≦L /2) (6), 3.0×10 −3 <c <3.1×10 −3 (7), and 2.7×10 9 <d <4.0×10 9 (8); and the curved lines defining the shape of the lens plane of each of the lens elements of emergence, given by the above numerical formulae (1) to (8), are on the x-y coordinates, and in these numerical formulae, x denotes the coordinate axis passing through both ends of the lens element of emergence, extending in a direction of the width of this lens element, y denotes the coordinate axis crossing the protruding apex of the lens element of emergence, the positive direction of the y-coordinate axis being from the viewer's side toward the image source side, L is a distance between the two ends of the lens element of emergence, a , b , c and d are coefficients, and e is an intercept between the curved line and the y-coordinate axis and is a coefficient relating to a height of the lens element of emergence.