• Steinheil-Mounted-Negative-Achromatic-Lenses-1

Steinheil Cemented
Achromatic Triplets

The focal point where light rays passing through the center of the lens converge differs slightly from the focal point where light rays passing through the edges of the lens converge, this is called spherical aberration; when light rays pass through a convex lens, the focal point for red light which has a long wavelength is farther away than the focal point for blue light which has a short wavelength, as a result colors appear to bleed, this is called chromatic aberration. Since the direction in which spherical aberration occurs in a convex lens is opposite to a concave lens, through a combination of two or more lenses light rays can be made to converge to a single point, this is called aberration correction. Achromatic lenses correct for both chromatic and spherical aberrations. Our standard and custom achromats are designed and manufactured to satisfy the most stringent tolerances required in today’s high-performance laser, electro-optical and imaging systems.

An achromatic triplets consist of a low-index crown center element cemented between two identical high-index flint outer elements. These triplets are capable of correcting both axial and laterial chromatic aberration, and their symmetric design provides enhanced performance relative to cemented doublets. The Steinheil triplets are specially designed for 1:1 conjugation, they perform well for conjugate ratios up to 5. These lenses make good relay optics for both on- and off-axis application and are often used as eyepieces.

Paralight Optics offers Steinheil achromatic triplets with MgF2 single layer anti-reflective coatings for the 400-700 nm wavelength range on both outside surfaces, please check the following graph for your references. Our lens design is computer optimized to insure that chromatic and spherical aberrations are simultaneously minimized. Lenses are suitable for use in most high resolution imaging systems and any application where spherical and chromatic aberrations must be reduced.



AR Coating:

1/4 wave MgF2 @ 550nm


Ideal for Compensation of Lateral and Axial Chromatic Aberrations

Optical Performance:

Good On-Axis and Off-Axis Performance


Optimized for Finite Conjugate Ratio


Common Specifications:


Reference Drawing for

Unmounted Steinheil Triplets Achromatic Lens

f: Focal Length
WD: Working Distance
R: Radius of Curvature
tc: Center Thickness
te: Edge Thickness
H”: Back Principal Plane

Note: The focal length is determined from the back principal plane, which does not correspond with any physical plane inside the lens.



Ranges & Tolerances

  • Substrate Material

    Crown and Flint Glass Types

  • Type

    Steinheil achromatic triplet

  • Lens Diameter

    6 - 25 mm

  • Lens Diameter Tolerance

    +0.00/-0.10 mm

  • Center Thickness Tolerance

    +/- 0.2 mm

  • Focal Length Tolerance

    +/- 2%

  • Surface Quality (scratch-dig)

    60 - 40

  • Surface Irregularity (Peak to Valley)

    λ/2 at 633 nm

  • Centration

    3 - 5 arcmin

  • Clear Aperture

    ≥ 90% of Diameter

  • AR Coating

    1/4 wave MgF2 @ 550nm

  • Design Wavelengths

    587.6 nm



This theoretical graph shows the percent reflectance of the AR coating as a function of wavelength (optimized for 400 - 700 nm) for references.
♦ Reflectance Curve of Achromatic Triplet VIS AR Coating