Aspherical lenses provide clear images both in the central and peripheral visual fields, enhancing overall visual quality and reducing eye fatigue.

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Aspherical lenses are flatter in appearance and do not protrude as much as traditional spherical lenses, making the wearer’s eyes look more natural and aesthetically pleasing.

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Aspherical lenses are suitable for most eyeglass frames, allowing you to wear almost any style, including rimless or plastic frames. They also prevent eye deformation, boosting your confidence when wearing glasses.

In regular lenses, light rays hitting the edges of the lens focus differently than those hitting the center. This results in blurry peripheral vision. If you have a high prescription, you need thicker lenses to properly bend the light. For hyperopia (farsightedness), the center of the lens needs to be thicker, making your eyes look magnified, sometimes referred to as “bug-eye” or “soda-bottle” appearance. You might feel self-conscious about your glasses and the way they make you look, but aspherical lenses can help.

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The working principle of aspherical lenses lies in their precisely calculated and designed curvature. Traditional spherical lenses, especially in high prescriptions, can cause the “magnification effect” and “distortion effect,” where the edges of the visual field appear larger or smaller than the center, leading to visual distortion and discomfort.

Some wearers may need time to adjust when using aspherical lenses for the first time. This is because the visual system requires time to adapt to the new optical design.

If you want to learn the story of scratch and dig in all its glory, take my OEOSC accredited course“Understanding Scratch and Dig.” I teach it periodically at conferences, as well as offering on-sitetraining. 1 Annual Optics Review, Laser Focus/Electro-Optics Magazine, November issue, pp 138-140 (1985).2 See for example G. White and J. Marchiando, “Scattering from a V-shaped groove in the resonance domain”, Appl. Oppt. Vol 22, No 15, pp 2308-2312 (1983).

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By David Aikens | Jan 8, 2020 10:00:00 AM | optical design, quality management, optical metrology

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Aspherical lenses have a flatter curvature and thinner center, reducing the magnification effect on your eyes. They also correct distortions, creating higher-quality images. Additionally, they improve peripheral vision. The lenses are thinner and lighter, making them more suitable for various eyeglass frames.

For more than fifty years, the de facto standard method of describing surface quality in optics has been with a pair of numbers referred to as the scratch and dig specification. And for almost as long, people have been trying to use this cosmetic standard to control surface imperfections on precision optics, where scratches and digs affect the performance of the system. The result has been disastrous, as you would predict. The truth is that the scratch and dig specification of MIL-PRF-13830B is a highly subjective, visibility standard, which is excellent for cosmetics, but insufficiently quantitative for performance-based specifications.

The manufacturing process of aspherical lenses is more complex, requiring higher precision equipment and craftsmanship, resulting in higher costs and prices.

In the eyewear industry, aspherical lenses have gradually gained favor due to their unique design and superior performance. They are especially suitable for those with high prescriptions. This article will delve into the fascinating aspects of this modern optical technology by discussing the definition of aspherical lenses, their working principles, advantages and disadvantages, and the people who can benefit from them.

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The scratch standard is only a cosmetic standard.The scratch standard is only a cosmetic standard.The scratch standard is only a cosmetic standard…

Aspherical lenses effectively reduce edge distortion, providing a wider and clearer field of vision. This advantage is particularly significant in high prescription lenses.

This is not a secret. Matt Young made this blazingly clear in his 1985 article “The scratch standard is only a cosmetic standard1. But in 1985, there wasn’t much we could do about it. There was no way to specify scratches and digs that was quantitative, objective, and did not require extensive capitalization. But in 1996, with the publication of ISO 10110 Part 7, there was an alternative. But ISO 10110-7 was cryptic and arcane, and aside from a few stalwarts, it never really became common practice. But in 2009, the new version of OP1.002 offered an alternative that is familiar, easy to use, and effectivefor people who really require a functional specification. By offering both visibility and dimensional methods, OP1.002-2009 is the only standard I recommend these days.

The aspherical design reduces the center thickness of the lens, making the overall lens thinner and lighter, more comfortable to wear, and less burdensome on the nose bridge.

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In the eyewear industry, aspheric lenses have gradually gained favor due to their unique design and superior performance. They are especially suitable for those with high prescriptions. This article will delve into the fascinating aspects of this modern optical technology by discussing the definition of aspherical lenses, their working principles, advantages and disadvantages, and the people who can benefit from them.

Because of an unfortunate revision to C7641866 in 1974, which was used by the Army to purchase some experimental scratch artifacts, there is a significant number of people who refer to the scratch number as “the width in microns.” This is simply not true, and never has been. But because such an “interpretation”is easier to meet, many optics shops will claim this in their specification documentation, on the assumption that their customer doesn’t understand the requirement. Shame on them. This is just  plain wrong. Scratch visibility and scratch width are not well correlated2. Not only is it a mis-interpretation ofthe MIL standard, it is the source of much of the confusion and conflict over the scratch and dig standard.

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Perhaps because of this confusion, the commercially available comparison standards have diverged. While the Army has maintained its own calibrated supply for military purchases, the commercially available standards cannot be certified against the masters. As a result, the comparison standards made by one supplier don’t necessarily have the same apparent brightness as a set made by another supplier. Each is different, and the customer should indicate which he intends to use to interpret his specification. Such a clarification is reasonable for the manufacturer to make; claiming to interpret the scratch number as awidth specification is not.

Aspherical lenses eliminate these negative effects by gradually changing the curvature of the lens surface. Specifically, the central part of an aspherical lens maintains a certain curvature, but as it transitions towards the edges, the curvature flattens. This design provides a larger usable area compared to regular lenses, meaning aspherical lenses can bend light more effectively. This reduces edge distortion, creating a more natural and smooth visual experience.

Aspherical lenses, as a product of modern optical technology, significantly improve the visual quality and comfort for wearers with their unique curvature design. Despite their higher manufacturing costs, their advantages in reducing visual distortion, decreasing lens weight, and improving aesthetics make them a preferred choice for many eyeglass wearers. By understanding the working principles, advantages and disadvantages, and suitable groups for aspherical lenses, we can make more informed decisions in selecting the right lenses for ourselves, enjoying clearer and more comfortable vision.

This is a call to action, to all you optics manufacturers, and to all you informed users of the scratch and dig standard. Stop this madness, and start telling the truth about scratch and dig. You know the real meaning of the scratch number; it is arbitrary, and corresponds to the visibility of the scratch, referenced to a pair of limit standards retained by the US Army ARDEC at Picatinny Arsenal. Take those Take those  disclaimers and incorrect scratch width documents off your website. Start taking exception honorably by saying “we will interpret your scratch and dig s pec per ANSI/OEOSC OP1.002-2009, using the xx calibration standard.” And the next time you get a call from a customer’s QA department, start the discussion by telling him the truth about scratch and dig.

Due to their complex design and manufacturing, repairing and replacing aspherical lenses can be more challenging and require professional technical support.