| 摘要 |
A collimating lens (10) is constructed of a lens assembly having a first lens set (12, 14) at a first end of the assembly and a second lens set (20) at a second end of the assembly with a doublet (16, 18) disposed between the first lens set and the second lens set. The first lens set includes a plurality of lens elements (12, 14) each of which has positive optical power. The second lens set has a single lens element (26) of positive optical power and a concave surface (40) facing subject matter to be viewed by the collimating lens. The doublet lens element includes a lens element (16) constructed of flint glass and having a negative optical power plus a lens element (18) constructed of crown glass and having a positive optical power. In the doublet lens element, the negative power lens element has two concave surfaces, the positive-power lens element has two convex surfaces, and the two lens elements are cemented together to provide for a broad-band chromatic correction. The second end of the optical assembly of the lens is characterized by a telecentric entrance pupil for the viewing of a radiant subject. An external aperture stop (50) is provided in front of the first end of the optical assembly at a distance of at least one focal length from the first lens element of the collimating lens. This provides for more efficient collection of light and a wider field of view.
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