| 摘要 |
Provided is a Fresnel lens the manufacture of that is unlikely to be affected by the working errors of the die in the optical axis and its neighborhood . Two lens surfaces (11, 11) that are disposed in the vicinity of the optical axis are disposed in the way they are shifted from each other in a direction along the optical axis, whereby the height Ha in this direction of the optical axis of a non-lens surface (12) located at the boundary between the two lens surfaces (11, 11) is made greater than an original height Ha of the non-lens surface (12) in a case where it is assumed that the lower ends (11a, 11a) of each of these lens surfaces (11, 11) has been placed on the same flat plane intersecting the optical axis OA at a right angle with respect thereto. Also, the lens angle Oa of at least one piece of lens surface (21) that is disposed in the vicinity of the optical axis is set to be greater than the original lens angle that should be given according to the focus calculation with respect to the lens angle (21). |
