Brief Introduction about Optical Aspherical lens

Spherical Lens and Aspherical Lens

A Sphere optical lens has a constant curvature from the center of the element to the edge, and the surface is spherical;In contrast, an Asphere optical lens has a continuous change in curvature from the center to the edge. Aspherical optical lenses are widely used in aviation airborne equipment, satellite, laser guidance, infrared detection and other fields, and are also increasingly popular in civil optoelectronic products.

Classification of aspheric lens

() Dimensions

●Large Optical Aspheric Lens: Above 500mm Diameter big outer size Aspheric Lens

●Medium aspheric lens: Aspheric lens in general optical instruments

●Micro aspheric lens: Diameter 2-9mm, even 0.1-0.8mm diameter aspheric lens

()manufacturing precision

●High precision aspheric lens: Used for astronomical instrument, and Objective lens in a spectrograph.

●Medium precision aspheric lens: Aspheric lens used in general optical instruments

●Low precision aspheric lens.

Advantages of aspheric lens

The following figure compares the focusing points produced by parallel monochromatic light passing through a spherical lens and an aspherical lens. The spherical lens has blurred imaging points due to spherical aberration, while the aspherical lens has very clear imaging points.Therefore, aspherical lens can be used to replace the spherical lens group to calibrate the positive difference. For example, one or two aspherical lenses can be used to replace five or six spherical lenses in the general use of a zoom lens with ten lenses, which can achieve the same or higher optical effect, reduce the production cost, and realize the lightweight and miniaturization of the system.Moreover, the reduction of the number of lenses in the optical system also reduces the mechanical tolerances, additional calibration steps, and anti-reflection coating film requirements, improving the overall practicality of the system and reducing the overall system design cost.

The use of aspherical elements in the optical system can improve the performance of the system, reduce the number of optical elements, so as to reduce the mass of the instrument, reduce the volume and compact structure.Therefore, aspherical optical elements are often used in optical systems with large field of view, large aperture, high aberration requirements, small structure requirements, or special requirements. Aspherical optical elements are increasingly becoming a very important optical elements due to their excellent optical properties.

Manufacturing process

At present, the processing methods used for aspheric optical elements mainly include:

1) Surface material removal method: CNC milling polishing molding method, ion beam polishing method, Magnetorheological (MR) Polishing method, liquid jet polishing method, etc.

2) Change material shape method: glass hot pressing molding method, injection molding method, heat deposition and curing molding method;

3) Additional material method: vacuum coating copy molding method, mixed molding method, etc.

Ultra-precision CNC milling and polishing are suitable for the one-time production of single aspherical lens. With the improvement of manufacturing technology, its machining accuracy is getting higher and higher. Computerized precision polishing technology can automatically adjust the tool residence parameters for accurate polishing.While other manufacturing techniques typically require a special die, each lens has its own unique die, CNC milling and polishing uses standard tools, making it a prime choice for prototyping and low-volume production applications.