A lenticular lens sheet 4 comprises a plurality of lens elements of incidence
21 arranged on the incidence side, and a plurality of lens elements of emergence
22 arranged on the emergence side. The light that has passed through each
lens element of incidence 21 converges via the protruding apex of the corresponding
lens element of emergence 22. The lens plane of the center portion C of
each lens element of emergence 22, the width of this portion C being a half
of the total lens width L (i.e., L/2), is in the shape defined by a curved line
fulfilling the conditions expressed by the following numerical formulae (1) to
(4), and the lens plane of each side portion S of each lens element of emergence
22, the width of this portion S being a quarter of the total lens width
L (i.e., L/4), is in the shape defined by a curved line fulfilling the conditions
expressed by the following numerical formulae (5) to (8): y=ab-x-e
(-L/4x0) . . . (1), y=abx-e (0xL/4)
. . . (2), 3.010-4a3.810-4 . . .
(3), 1.01024b1.01025 . . . (4), y=cd-x-e
(-L/2x-L/4) . . . (5), y=cdx-e (L/4xL/2)
. . . (6), 3.010-3c3.110-3 . . .
(7), and 2.7109d4.0109 . . . (8).
