Color Corrected Aspheric Lenses Reduce both Spherical and Chromatic Aberration

Posted by Bill Hill on

When precision and image quality are critical to the performance of an optical assembly, minimizing the number of lenses can become a critical design consideration. Selecting single optical lenses that can simultaneously reduce multiple aberrations is an ideal way to achieve this goal. Color-corrected aspheric lenses, for instance, reduce both spherical and chromatic aberration, making them ideal for a wide range of applications.

Chromatic, or color, aberration occurs in conventional optical lenses when different wavelengths of light focus at different points along the optical axis, and is typically eliminated by introducing multiple lenses, fabricated from glasses with different indices of refraction, into an optical assembly. Chromatic aberration can also be eliminated, however, by using fewer color-corrected aspheric lenses instead of a greater number of conventional spherical lenses. Reducing the element count not only minimizes the size and weight of the assembly, but also simplifies the assembly process, yielding imaging lenses that ultimately cost less and outperform assemblies made of traditional spherical optical components.


What are chromatic aberrations?

An optical aberration is a departure of the performance of an optical system from that predicted by the laws of conventional optics.  In an imaging system, for example, chromatic aberrations can occur when light from one point of an object does not converge into, or does not diverge from, a single point after transmission through the system. Aberrations occur, not so much because of flaws in the optical elements as because the simple laws of conventional optics are not a completely accurate model of the effect of an optical system on light.

Aberrations lead to blurring of the image produced by an image-forming optical system.  As noted above, they can be corrected by the use of properly designed aspheric lenses.

What are aspheric lenses?

Unlike conventional lenses with a spherical surface, aspheric lenses have a more complex surface that gradually changes in curvature from the center of the lens out to the edge of the lens.  This more complex surface profile can reduce or eliminate spherical aberration and also reduce other optical aberrations compared to a simple lens.  A single aspheric lens, for example, can often replace a much more complex multi-lens system with the resulting device being smaller and lighter, and sometimes cheaper than the multi-lens design.

Aspheric lenses are also available with a wide variety of coatings that enable them to perform in the Ultraviolet (UV), visible light, or Infrared (IR) spectrum.  They also can be fabricated from a variety of materials from standard optical glasses such as BK-7 and industrial, UV and IR-grade fused silica to exotic materials like Germanium (Ge), Zinc Selenide (ZnSe), Silicon (Si) and Zerodur® among others.  Esco Optics works with glasses from all major glass suppliers and manufacturers like CorningSchottOharaTosohHoya, and others.

Whether you are developing an entirely new application or improving an existing one, the experts at Esco Optics will be happy to work with you to custom design aspheric lenses that precisely meet your needs and stay within your budget.

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