| 摘要 |
<p>An optical filter (11) for use with an imaging lens (29) in an incoherent imaging system operating in broadband illumination increases the depth-of-focus of the lens while maintaining energy thru-put. The optical filter (11) comprises a transparent support (13) having on one surface (17) thereof an array of transparent, discrete steps (15) of substantially equal size, each step having a thickness that differs from all other steps by at least the coherence length of the radiation to be passed and the size of the array being equal to the size of the lens. In use, the optical filter (11) is positioned in front of the imaging lens. When so positioned, the depth of focus of the imaging lens is proportional to the size of the individual steps rather than the size of the lens while the energy thru-put of the imaging remains the same as it would be without the optical filter.</p> |
