| 摘要 |
A projection lens with a short focal length and high initial aperture is proposed. Such projection lenses are used, for example, in cinema projection. The projection lens is configured such that the sum of the overall length and the back focus ( 12 ) is between 2.8 times and 4.5 times the total focal length f'. The entrance pupil is at a distance of between 100 mm and 300 mm from the last lens surface ( 62; 150 ), which faces the illuminating mirror. The minimum stop number k of the projection lens is 1.7, and the projection lens is therefore also suitable for illuminating mirrors with a high aperture angle (of up to 17°).
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