| 摘要 |
The present invention relates to the field of laser machining and provides an optical lens, comprising a lens group and a diaphragm which is located in front of the lens group. The lens group comprises three lenses, respectively the first, the second and the third lens, which are sequentially arranged as a “negative-positive-positive” separated focal power system, wherein the first lens is a negative meniscus lens, the second lens is a positive meniscus lens, the third lens is a plano-convex or positive meniscus lens. All the curved surfaces of the first lens and the second lens are bent in the direction towards the diaphragm, and the focal length of the entire optical system is f, the focal lengths of the first, the second and the third lens are respectively f1, f2, and f3, and the ratio between the focal length of each lens and the focal length f of the entire optical system satisfies the following requirement: −0.6<f1/f<−0.4; 0.5<f2/f<0.8; 0.9<f3/f<1.2. The optical lens provided in the present invention adopts a lens group comprising a negative meniscus lens, a positive meniscus lens, and a double convex or positive meniscus lens arranged in sequence, so as to make the spherical aberration, the image aberration and the curvature of field of the system all achieve a better balance, to make the result of imaging well and to make the imaging uniform all over the image plane. Moreover, the structure upon being applied to the f&thetas; lens with a large aperture incidence achieves a comparatively good result in respect of miniaturization.
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