Aspheres

aspheres

An aspheric lens has at least one surface defined by an aspheric equation that has a fluctuating local radius across the diameter of the part. This creates an optical lens with a non-constant radius all of the way around the sphere.

LaCroix Manufacturing Engineers will analyze your print and aspheric lens design. They will match the sag table provided with the print to verify the correct custom aspheric lens is being manufactured. When sending a sag table and aspheric terms do not truncate the vertex radius, conic constant, or any of the aspheric terms as we will not be able to match and verify your aspheric sag table.

spherical v. aspherical
Aspherical v. Spherical

Materials

Optical Glass • Fused Silica • Filter Glass

Sizes

3mm – 200mm

Tolerancing

Aspheric Surface Commercial Precision Max Capability
Form Error (um) 1 0.5 0.1*
Slope Error (um/mm) 0.8 0.5 0.05*
Dimensional Tolerances Commercial Precision Max Capability
Diameter (mm) +/- 0.10 +/- 0.05 +/- 0.01*
Center Thickness (mm) +/- 0.15 to 0.20 +/- 0.10 to 0.05 +/- 0.02
Surface Tolerances Commercial Precision Max Capability
Surface Quality (scratch-dig) 80 – 50 60 – 40 10 – 5
Surface Roughness (ARMS) 10* 5*
Surface Irregularity (Fringes, P-V @ 633nm) 2 to 4 1/2 to 1 1/5
Surface Power (Fringes, P-V @ 633nm) 10 3 to 5 1
Centration (Ray deviation) 5'+ min. 2' – 3' min. 10" sec.
* material and size dependent

The manufacturing process of an aspheric lens begins by designing a near net shape optical glass blank. An initial rough grind using a diamond ring tool is used to generate a best-fit-sphere into the aspheric lens blank. A series of progressively smaller grit diamond tools are then used to sub-aperture grind the aspheric prescription into the part.

LaCroix utilizes highly specialized CNC grinding technology to minimize mid-spatial frequency errors.

Once the optic is sufficiently ground, the aspheric lens is then initially polished to remove all subsurface damage induced in the grinding process. An iterative feedback loop is initialized by taking measurements with either a profilometer or utilizing 3D aspheric metrology on all aspheric lenses. This measurement is fed back to the aspheric polisher for a correction run. This process is repeated until form and slope error specifications are met.

An iterative feedback loop is initialized by taking measurements with either a profilometer or utilizing 3D metrology on all asphere lenses. This measurement is fed back to the aspheric polished for a correction run. This process is repeated until form and slope error specifications are met.

Technology

LaCroix Precision Optics is dedicated to maintaining state-of-the-art machinery and as such, has recently made significant investments in the latest innovative aspheric technology. View our Advanced Processing page to learn more.

Coatings

We have extensive in-house coating capabilities to meet your requirements. See our coating capabilities.

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