Spherical VS Aspheric Lenses, how do they work in imaging ...

Selecting the right lens for your imaging application is important to achieving optimal performance. Lenses come in various shapes and forms, each with its own unique characteristics and advantages. Understanding the differences between spherical and aspheric lenses can help you make an informed decision that meets your specific needs. In this blog, you will learn more about the intricacies of both lenses, including their design, how they work, their applications, and the main considerations in choosing the right lens for an optical system.

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A sphere-shaped lens features an even curvature across its entire surface and is relatively inexpensive and easy to manufacture, aspherics being more so. However, Spherical lenses may suffer from an effect called Spherical Aberration which causes light rays passing through their edges not focusing correctly in comparison with those passing through its center; images produced can appear blurry due to this phenomenon using wider apertures or high magnification magnification levels.

Refraction occurs when light rays pass through spherical lenses which bend them as they pass. Their basic principle lies within their circular design: light entering such lenses interact with its curvilinear surface, leading them either towards convergence (convex lenses) or divergence (concave lenses).

Here’s a more detailed look at how spherical lenses work, based on their type:

Focusing the light through a spherical lens depends upon its curvature, refractive indices of materials used in its construction and wavelengths of light that pass through it. Spherical lenses suffer from distortion due to their uniform curve; light hitting their edges being refracted more than those striking its center, thus leading to different focus locations along an optical axis.

Aspherical lenses work by controlling the direction that light rays pass through through a process known as refraction, similar to how spherical ones do, yet feature significant variations in surface curvature; their profiles tend to be more complex than spherical ones which typically feature uniform curvatures; as such they’re better at correcting aberrations (especially spherical) more effectively due to non-uniform surface curvatures; as such they focus light more precisely onto one focal point; correct aberrations while correct aberrations more effectively due to non-uniform surface curvatures as opposed to uniform curvatures featured by their counterparts spherical counterparts which feature uniform curvatures; they also focus light more efficiently onto one point when focused onto one point than traditional counterparts would allow.

Take a close look at an aspherical lens to witness its functionality:

Finding an aspherical or spherical lens suitable to your needs requires considering several key aspects, particularly within photonics. Photonics is an expansive field that encompasses everything from telecom systems and laser beam systems through medical photonics as well as sensors requiring lenses – this comprehensive guide can assist in selecting an appropriate type of lens in photonics applications.

In the field of photography, aspheric lenses are prized for their ability to minimize distortion and provide high image clarity, making them essential in professional-grade cameras and high-end smartphones. They help achieve sharp images with accurate focus, important for detailed photography and videography. Spherical lenses, while not as advanced in reducing aberrations, are commonly used in entry-level cameras where cost-efficiency is a priority.

VR and AR systems demand lenses that can deliver a wide field of view with minimal distortion. Aspheric lenses are well-suited for these applications due to their ability to provide clear and immersive visuals, enhancing the user experience. The precision in aspheric lenses ensures that users perceive virtual objects with minimal optical flaws, which is critical for maintaining realism and immersion in VR and AR environments.

In display technologies such as projectors and augmented reality displays, the choice between spherical and aspheric lenses can impact image quality and device compactness. Aspheric lenses help in producing uniform and high-quality images across the entire display surface, while spherical lenses might be used in more cost-effective solutions where high precision is not as important.

Aspheric lenses, due to their complex manufacturing process and materials, can be more delicate and susceptible to damage if not handled properly. They require careful handling and storage to maintain their precision and performance. On the other hand, spherical lenses, being simpler in design and construction, tend to be more robust and less prone to damage, making them a durable option for rugged applications and environments.

The maintenance requirements for aspheric lenses are typically higher due to their complex surface profiles, which can make cleaning and alignment more challenging. Special tools and techniques might be needed to ensure they remain in optimal condition. Spherical lenses, with their simpler curvature, are easier to clean and maintain, reducing the time and cost associated with their upkeep.

Selecting the right lens type for your imaging application involves a thorough understanding of the specific requirements and constraints of your project. Spherical lenses offer simplicity and cost-effectiveness for less demanding applications, while aspheric lenses provide superior optical performance for high-precision tasks. By considering factors such as clarity, field of view, compactness, cost, and supplier capabilities, you can make an informed decision that meets your needs. Innovations in lens technology continue to expand the possibilities, making it an exciting time for developments in optical systems.

An aspherical lens is a lens whose lens surface is not spherical. By using lenses with aspherical surfaces, which offer a high degree of freedom in design, it becomes possible to reduce aberrations that could not be fully corrected with spherical lenses alone.

In this way, aspherical lenses make it possible to reduce the size and weight of products, and even to cut costs. However, the production of aspherical lenses requires a very high level of manufacturing technology.

In this section, we will explain the features, advantages / disadvantages, and manufacturing methods of aspheric lenses.

Principles of Light Collection and Divergence and Classification of Lenses by Surface Type

There are many different types of lenses. They can be broadly classified as the following according to the principle of light focusing and divergence and the type of surface.

Lenses ① to ⑤ are lenses that have a focusing and diverging effect solely due to refraction on the lens surface. Of these, lenses ① to ④ have a continuous smooth surface, while lens ⑤ has a lens surface that is divided into discontinuous zones.

On the other hand, in the case of ⑥, the refractive index inside the lens is not homogeneous but distributed, and in the case of ⑦, light is focused and diverged by using the diffraction effect on the surface instead of refraction.

Lenses ② to ④ are lenses with continuous, smooth, non-spherical lens surfaces and are called aspherical lenses in a broad sense. ② is a lens with an aspheric surface that is axi-symmetric (rotationally symmetric) with respect to the optical axis of the lens, and is often used in imaging optical systems. Lenses ③ to ④ are aspheric lenses that do not have axisymmetry (rotational symmetry) with respect to the optical axis of the lens, and are mainly used in lighting and focusing optical systems.

＞＞What Problems do Spherical Lenses Have?

What is an Aspheric Lens?

An aspheric lens is a lens with a non-spherical lens surface.

Contact us to discuss your requirements of Optical Spherical Lenses For Imaging. Our experienced sales team can help you identify the options that best suit your needs.

Features of Aspheric Lenses

Aspherical surfaces are classified into two categories: axi-symmetric aspherical surfaces, which have axial symmetry (rotational symmetry) with respect to the lens optical axis, and aspherical surfaces, which do not have axial symmetry. Each type of aspheric surface has its own characteristics.

Aberration reduction

Axi-symmetric aspheres include rotational parabolas, rotational hyperbolic surfaces, rotational elliptic surfaces, and rotational quadric surfaces. In imaging optics, the use of such axisymmetric aspheres increases the degree of freedom in shape and makes it possible to suppress aberrations that would be difficult with spherical lenses alone.

In addition, when axi-symmetric aspheres are used in illumination and focusing optics, it is possible to achieve uniform illumination distribution and increase the degree of freedom in ray control.

Addition of new functions

Aspheres that are not axi-symmetrical (rotationally symmetrical) can be used to change the magnification of vertical and horizontal images in imaging optics. Also, in illumination and focusing optics, light emitted from a point light source can be projected in the form of a line. In this way, aspheres that are not axisymmetric (rotationally symmetric) can achieve new functions that cannot be achieved with spherical lenses alone.

Advantages of aspheric lens

In this section, we will introduce the advantages and disadvantages of axi-symmetric (rotationally symmetric) aspheres in imaging optics. There are three major advantages.

Number of lenses can be reduced

In imaging optics, multiple spherical lenses are used in combination to reduce aberrations such as image blur and distortion. By using aspherical lenses, it is possible to reduce the number of lenses while maintaining the same performance. For example, you can achieve the same performance of an 5-spherical-lens optical system with a total of 4 lenses using 2 spherical lenses and 2 aspherical lenses.

Lens units can be made smaller and lighter

The fewer the number of lenses, the more compact and lighter the optical unit can be.

Cost reduction for optical products

With fewer lenses, it is possible to reduce lens materials, processing costs, and assembly man-hours, leading to overall cost reductions.

Disadvantages of aspheric lenses

On the other hand, aspheric lenses have their own disadvantages, too.

Expensive if produced in small quantities

A spherical glass lens is processed by grinding one surface at a time, but grinding and polishing an aspherical lens one surface at a time would be very expensive. For this reason, aspheric shapes are generally processed into molds, which are then transferred and molded onto glass or plastic.

Although the time required for transfer and molding is shorter than for the spherical polishing process, manufacturing of precision aspheric molds (which incurs cost) in advance are necessary. For this reason, consideration of whether or not to use aspheric lens prior to production, based on the estimated total cost of the production volume is necessary.

High processing difficulty

Spherical surfaces are characterized by the fact that the radius of curvature is the same at all positions on the sphere, and this leads to the fact that they are easy to polish and high precision can be obtained. On the other hand, aspheric lenses require the radius of curvature to be made different depending on the position, which requires precision mold processing and technology to precisely transfer and mold the aspheric shape.

Manufacturing of Aspheric Lenses

The method of manufacturing aspherical lenses by transferring and molding the aspherical shape of the mold onto the lens requires three technologies: ultra-precision mold processing technology, ultra-precision transfer and molding technology, and precision measurement and evaluation technology for these surface shapes.

At Optical Design Technology Navigator, we use state-of -the-art ultra-precision processing machines to process aspheric surfaces on a sub-micron order, transfer these aspheric surfaces using molding technology that incorporates a high level of know-how, and then transfer these aspheric surfaces into an ultra-precision 3D mold.

Optical Design Technology Navigator will solve all your needs for aspherical lens manufacture!

TOYOTEC, operator of the Optical Design Technology Navigator, is an all-around optical manufacturer with proficiency in optical, mechanical, and electronical technology. We can design and develop products from scratch based on our customers’ needs, and provides integrated support from design to productization. In addition to manufacturing aspheric lenses, we offer one-stop manufacturing services from ultra-precision machining of lens cores to the design and assembly of lens units, including systems and peripheral components.

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