| 摘要 |
An infrared lens assembly (16) having a variable F/Number. The infrared lens assembly (16) includes a focusing component (33), a collecting component (37), an aperture stop (46), and a diffracting component (41). The focusing component (33) may include a first and a second focusing zoom lens (34, 36) movably mounted in the infrared lens assembly (16). The focusing component (33) and the collecting component (37) may be formed from high dispersion, low index material. The aperture stop (46) may be mounted to the second focusing zoom lens (36) to vary the F/Number between a retracted zoom position and an extended zoom position. The diffracting component (41) may include a diffractive surface to correct color aberrations associated with an infrared waveband. The focusing component (33) and the collecting component (37) cooperate with the diffracting component (41) to focus infrared radiation at an image plane (15) of an infrared detector (18).
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