| 摘要 |
<p>A fixed-focus lens (200) for projecting an image from a light valve (60) onto a screen comprises a first lens group (210), a second lens group (220), and a third lens group (230) arranged in this sequence from the screen to the light valve. The first lens group has negative refractive power, the second lens group has positive refractive power and the third lens group has positive refractive power and comprises four lenses. The on-axis distance between the first and second lens groups is S 1-2 , the effective focal length of the third lens group is F 3 , and S 1-2 /F 3 > 1.51. The effective focal length of the lens closest to the screen in the first lens group is F 11 . The effective focal length of the fixed-focus lens is F, and F 11 /F<-18.5.</p> |
