| 摘要 |
A lens system for an electronic system has two lenses. The first lens (S1/S2) has a negative power and the second lens (S4/S5 or S5/S6) has a positive power and is spaced from the first lens (S1/S2) by a distance of at least a quarter of the focal length of the lens system. In one embodiment (Fig. 3), the second lens (S4/S5) is a refractive-diffractive hybrid lens in which case both the first and the second lenses (S1/S2 and S4/S5) can be composed of acrylic and can have only spherical and conic surfaces. In other embodiments (Figs. 1, 2 and 4), the first lens (S1/S2) has a higher dispersion than the second lens (S4/S5 or S5/S6), e.g., the first lens (S1/S2) is composed of styrene and the second lens (S4/S5 or S5/S6) is composed of acrylic. In this case, the first lens (S1/S2) can have a spherical and a general aspherical surface, and the second lens (S5/S6) can have conic surfaces (Figs. 1 and 2), or both the first and second lenses (S1/S2 and S4/S5) can have a spherical surface and a conic surface (Fig. 4).
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