| 摘要 |
There is disclosed an objective or compound lens with high speed and large field angle for applications using infrared radiation. Preferred embodiments of the lens system have a useful spectral bandpass in the 2-2.5 mu m and 1.5-2.5 mu m region. These embodiments are constructed to have low resolution, a speed up to F/0.7 and a total field angle up to 60 degrees. Two embodiments comprise only 4 spherical lenses. By simple calculations the disclosed objectives or compound lenses may be matched to lens materials for use within other ranges of the infrared spectrum as well.
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