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Aspherical Lenses and Cylindrical Lenses

Ⅰ. Understand aspheric lens

The aspheric lens has a better radius of curvature and can maintain good aberration correction to obtain the required performance. The application of aspheric lenses brings excellent sharpness and higher resolution, and the miniaturization of the lens design becomes possible. In addition, the radius of curvature of the aspheric lens changes with the central axis to improve optical quality, reduce optical components, and reduce design costs. Aspheric lenses have unique advantages over spherical lenses, so they are widely used in optical instruments, imaging, and optoelectronics industries, such as digital cameras, CD players, and high-end microscopy instruments. Then both aspheric lenses and cylindrical lenses can achieve laser collimation. What are the differences between them?

Ⅱ. The difference between the aspheric lens and cylindrical lens

The aspherical cylindrical lens is composed of a photosensitive polymer and a glass optical lens. The polymer is coated on only one surface of the doublet lens, so it can be manufactured quickly in a short time, providing flexibility similar to a typical multi-element assembly. The aspherical cylindrical lens can effectively reduce spherical aberration and chromatic aberration. There are plano-convex cylindrical lenses, plano-concave cylindrical lenses, double-convex cylindrical lenses and double-concave cylindrical lenses with a one-dimensional zoom function.

The aspheric lens will not introduce spherical aberration compared to the spherical lens due to its aspheric surface design. Still, it can only become an elliptical collimated beam after passing through these two lenses. For an optical system that requires a circular beam, a cylindrical surface is required. The lens pair rounds the spot. A plano-convex cylindrical lens will focus the incident light on the line with a positive focal length. It consists of a flat surface and a convex cylindrical surface. It is often used to gather parallel or divergent light beams onto the line or change the image's aspect ratio.  

Cylindrical lenses are similar to spherical lenses because they all use curved surfaces to focus or diverge light. Still, cylindrical lenses only can converge or split in one direction and will not affect the light in the vertical direction. Suppose a symmetrical output beam is to be produced. In that case, the focal length ratio of the two cylindrical lenses should be the same as the ratio of the central axis to the minor axis of the elliptical beam emitted by the LD. As with standardized collimation, the diode to be measured is placed at the focal point of the two lenses, and the distance between the lenses is equal to their focal length difference. A cylindrical lens is an aspheric lens, which can effectively reduce spherical aberration and chromatic aberration. Divided into the plano-convex cylindrical lens, plano-concave cylindrical lens, double-convex cylindrical lens, double-concave cylindrical lens, cylindrical meniscus lens, cylindrical cross cylindrical lens and special-shaped cylindrical lens, with a one-dimensional zoom function.

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