Aspheric Lenses

Posted by Ron Schulmerich on

Esco Optics is a world-class manufacturer of apheric lenses. Esco Optics fabricates OEM and custom aspheric lenses to satisfy any requirement or specification. Examples of applications of aspheres include cell phones, small digital cameras, and progressive eyeglass lenses. Small, molded aspheres are often used for collimating diode lasers.The term aspheric simply means not spherical. Aspheric lenses differ from spherical lenses in several ways.

The inherent shape of a spherical lens creates a problem called spherical aberration.Spherical aberration is created when parallel light rays that pass through the central region of the spherical lens focus farther away than light rays that pass through the edges of the lens. This results in many focal points, which in turn produce a blurry image. To get a clear image, all rays need to focus on the same point.

Most aspheric elements are rotationally symmetric, and the radius of the surface changes with the distance from the optical axis. Aspherical lenses eliminate spherical aberrations in addition to other system aberrations. This is perhaps the greatest advantage of considering an asphere in an optical system. Elimination of spherical aberration also reduces the number of optical elements required in an optical system. This added benefit lowers the weight and the cost of manufacturing the system. Aspheres also reduce some distortions.

A spherical surface is defined by the radius of curvature alone. An aspheric surface can be defined by up to 12 or more aspheric terms. The general form of an asphere is defined by the conic constant (k). This is very important when evaluating the manufacturability of aspheres.

Manufacturing aspheres presents a challenge regarding traditional fabrication and metrology methods. At Esco Optics, our aspheres are manufactured with the aid of computer-controlled polishing. (CCP). CCP incorporates CNC machine tools and utilizes an aspheric contouring tool path. Variable pressure and a flexible tool surface are also integral parts of CCP-type processing. CCP is very efficient at manufacturing rotationally symmetric aspheres.

Esco Optics aspheric manufacturing capabilities incorporate grinding and polishing on our CNC Optotech machine tools. At Esco Optics, our Optotech manufacturing cell is capable of manufacturing aspheres from prototypes to high production. Coupled with the CNC technology at Esco Optics is the tenured expertise of our master opticians.

Esco Optics has invested heavily in the metrology aspect of our asphere manufacturing cell as well. Our recently purchased Mahr Marsurf LD120 3D asphere profilometer assures our customers of accurate and repeatable measurements of our aspheres. Esco also utilizes zygo interferometry. Esco Optics has also recently established relationships with partners utilizing MRF polishing techniques and SSI interferometry to allow us to offer high-precision aspheres.

The manufacture of aspheres is not a new technology, but it does demand a top-down organizational commitment to invest in the proper equipment, methodology, and trained personnel. Esco Optics has satisfied this criteria and is excited to offer a range of services to our customers.

If you are interested in discussing our capabilities in depth or have a specific requirement, we will be happy to talk with you at

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