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The Future of Microscope Objectives

Aspheric Lens
Takeover

October 2018 | See all Trending in Optics Topics

Time to Replace Spherical Elements with Aspheric Lenses

 

Spherical lenses being swapped out for aspheric lenses to reduce system size and weight

 

A single aspheric lens can replace a complex system of multiple spherical lenses

 

Advances in aspheric manufacturing have made aspheres produced by grinding and polishing more cost effective

 

System cost and weight reduced while maintaining or improving performance

Aspheric lenses have been used for decades to reduce spherical aberration and improve the performance of optical systems, but their high cost made them cost prohibitive in many applications. Recent advances in aspheric grinding and polishing have allowed subaperture polishing to produce high quality aspheres without requiring magneto-rheological finishing (MRF), greatly reducing cost. A single one of these more affordable, high-performance aspheric lenses can replace multiple spherical lenses with either the same or better performance, leading to lighter, smaller, and less complex systems at a lower cost than previously possible.

Using Fewer Elements: Keep it Simple

One of the main benefits of aspheric lenses is their improved aberration control which allows optical designers to use fewer elements than a design using conventional spherical optics. For example, several aspheres can be substituted for a handful of spherical lenses in a complex lens assembly where ten or more lens elements are typically used while achieving similar or better performance (Figure 1). This simplifies the assembly process and also reduces system size and weight. Reducing the number of elements also reduces the number of surfaces where reflections can occur inside the optical assembly, increasing light throughput.

While aspheres may seem more complicated than spherical lenses, a single asphere can replace multiple spherical lenses in an optical assembly, leading to a simpler, more compact, and more lightweight final system
Figure 1: While aspheres may seem more complicated than spherical lenses, a single asphere can replace multiple spherical lenses in an optical assembly, leading to a simpler, more compact, and more lightweight final system.

Reducing Cost: Show me the Money

There is no denying that a single aspheric lens is typically more expensive than a single spherical lens, but recent advances in asphere manufacturing technology have allowed high-performing aspheres to be produced at a significantly reduced cost. Previously, spherical full-aperture grinding and polishing could achieve irregularities of λ/4, while aspheric grinding and polishing could only achieve irregularities of 1λ. Magnetorheological finishing (MRF), a deterministic fine finishing process that selectively removes material with high precision and control, was required to produce higher quality aspheres and could achieve irregularities down to λ/20. However, MRF adds a significant amount of cost. Advanced subaperture aspheric grinding and polishing is now approaching the same irregularity capabilities as spherical full-aperture grinding and polishing, producing high quality aspheres at a reduced cost. This drop in asphere cost makes replacing multiple spherical lens elements with fewer aspheric lenses an even more economical solution, leading to an increase in optical designers incorporating aspheres into their designs. While MRF is not required for all asphere manufacturing, MRF is still required for extremely high quality aspheres with irregularities typically only limited by the sensitivity of available metrology.

Improvements in aspheric grinding and polishing are driving the increase in optical designers swapping out multiple spherical components for a smaller amount
Figure 2: Improvements in aspheric grinding and polishing are driving the increase in optical designers swapping out multiple spherical components for a smaller number of aspheres.

High-End Asphere Design for Manufacturability Webinar

Learn about the benefits of using aspheres in optical system design and what factors are taken into account during the design process in our webinar presented by Oleg Leonov, Asphere Business Development Manager, and Amy Frantz, Optical Engineer.

Aspheric Lens Takeover at Edmund Optics®

Aspheric Manufacturing Capabilities

Aspheric Manufacturing Capabilities

Edmund Optics’ aspheric lens production cell operates 24 hours a day to manufacture thousands of aspheric lenses every month. Whether you require a stock component from our vast inventory of over 600 aspheric lens designs, a build-to-print lens, or a fully custom asphere design, Edmund Optics has a solution to meet your needs manufactured through either molding, diamond turning, or subaperture grinding and polishing.

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MRF Technology

MRF Technology

Even with the advances in aspheric subaperture grinding and polishing, magnetorheological finishing (MRF) is still needed to manufacture the highest quality of aspheres. MRF is a deterministic and computer controlled process that removes many of the manual steps and guesswork necessary typically involved in finishing a fine optical surface.

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Metrology

Metrology

Edmund Optics utilizes a wide variety of metrology equipment to ensure the quality of aspheres and other optical components manufactured in our global manufacturing facilities including interferometry, profilometry, coordinate measuring machines, and computer generated holography.

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FAQ's

FAQ  Haven’t aspheres been around for decades? Why is this a current trend?
While aspheric lenses have been around for decades, recent advances in aspheric subaperture grinding and polishing have made them more affordable than ever before. Because of this, aspheric solutions that were previously cost prohibitive are now more accessible and replacing multiple spherical components with a smaller amount of aspheres reduces size and weight while maintaining or improving performance.
FAQ  What exact kind of metrology does Edmund Optics use to support its asphere manufacturing?

Edmund Optics utilizes a wide range of metrology to support our asphere manufacturing including Talysurf PGI 1240 profilometers, QED ASI aspheric stitching interferometers, Zygo® NewView white light interferometers, OptiPro UltraSurf 4X 100 non-contact profilometers, TRIOPTICS Opticentric® centering machines, Zeiss Contura G2 coordinate measuring machines (CMMs), Olympus MX51 microscopes, design-specific computer generated holograms (CGHs), and null lenses.

FAQ  What are Edmund Optics’ typical manufacturing tolerances?

A full list of Edmund Optics’ manufacturing tolerances can be found on our Aspheric Manufacturing Capabilities page.

FAQ   Does Edmund Optics still use magnetorheological finishing for high quality aspheres?

Yes, magnetorheological finishing (MRF) is still required for the highest quality aspheres and can achieve accuracies exceeding λ/20.

FAQ  What are the different types of aspheric lenses?

There are many different types of aspheric lenses with their own advantages and disadvantages, as shown in the table below:

Asphere Type Description Relative Price
Precision Aspherized Achromatic Lenses Diffraction-limited and color-corrected doublet with aspheric surface for broadband applications $$$$
“Laser-Grade” Aspheres <λ/10 transmitted wavefront $$$
Precision Polished Aspheres Most common asphere type, offering a balance between cost and performance $$
Best Form Aspheres Modified PCX or PCV lenses with one aspheric surface $$
Diamond Turned Aspheres Made out of high end plastics and crystalline materials $$
Hybrid Aspherized Achromatic Lenses Low cost doublet with molded polymer diffractive surface to minimize chromatic aberration $
Molded Aspheres Low cost plastic or glass lenses suited for high volume production $

Resources

Application Notes

Technical information and application examples including theoretical explanations, equations, graphical illustrations, and much more.

All About Aspheric Lenses
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Edmund Optics Preferred Glass Types
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Need an Asphere Fast?
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Aspherized Achromatic Lenses
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Videos

Informative corporate or instructional videos ranging from simple tips to application-based demonstrations of product advantages.

The Making Of An Aspheric Lens
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Aspheric Lenses Review
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Meet Jeremy Govier: Asphere Guru
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Technical Articles

Links to technical articles appearing in industry publications authored by Edmund Optics or featuring contributions from Edmund Optics' engineering team and key management

"The Long and the Short of It: Techniques for Measuring Aspheres" by Amy Frantz - Photonics Spectra
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"Optimizing the Design of Aspheric Lenses" by Jeremy Govier - Photonics Spectra
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"Design Considerations for Aspheric Lenses" by Jeremy Govier - Photonics Spectra
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