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Achromatic Lenses


A prominent issue with single spherical lenses is the introduction of chromatic aberration, where the focal point varies for different wavelengths of light. However, this can be minimised by using an achromatic lens (an achromat) which consists of multiple elements – typically two lenses (a doublet) or three lenses (a triplet) manufactured from different glass types.

Knight Optical can provide custom achromatic lenses, both as doublets and triplets, manufactured to your specific requirements. Our typical manufacturing capabilities can be found below, and a range of glass types are available including Schott (and equivalent) materials.
 

 

Diameter

Centration

Surface Figure

Scratch/dig

Achromatic Lens

3mm to 150mm+

< 3 arc minutes

< 1 fringe

< 60/40

 
We can provide positive and negative focal lengths, and already stock a variety of achromatic doublet lenses ranging from 4mm to 110mm in diameter. Knight Optical can also supply achromatic doublet lenses where infrared materials such as germanium, silicon and zinc selenide are used.

Knight Optical can also provide achromatic aspheric lenses where one of the surfaces is aspheric to further reduce chromatic and spherical aberration. The aspheric element can be polymer-based, making it a cost-effective solution, or using another glass type for more precision imaging.

Contact our technical sales team if you require further information or guidance with your enquiry.

Additional Information

  • Achromatic lenses are excellent for minimising both chromatic and spherical aberrations.
  • They generally correct for blue and red light when used in visible wavelengths, which is achieved by using a concave high-index flint glass and a convex low-index crown glass.
  • There are two main achromatic triplet types, the Hastings triplet and the Steinheil triplet, both of which consist of a low-index element cemented between two high-index components.
  • We can also supply apochromatic triplet lenses which correct for three wavelengths rather than two (red, blue and green). These are widely used in photography where the designation ‘APO’ is used. Often a fluoride element is used, using materials such as calcium fluoride.

Coatings

An optical coating can be applied to your achromatic lens to enhance its performance. Typically an antireflective (AR) coating is applied which is optimised for a broadband wavelength range.

Quality Assurance

Knight Optical can verify your optical components in our metrology laboratory, where our technicians check your achromatic lens against its specification.

  • The radius of curvature and irregularity of spherical surfaces are checked on our Zygo Verifire interferometer, where we can also check the transmitted wavefront error.
  • Our Trioptics OptiSpheric and OptiCentric are used to test the focal length and centering error respectively.
  • Optical coatings are verified on our Agilent Cary 7000 Spectrophotomer which can perform spectral scans at multiple angles of incidence and different polarisations.
  • All optics are 100% visually inspected before packaging, our staff are trained to ISO 10110 and MIL-0-13830A, and can check down to 10/5 scratch/dig which is especially critical for lenses used in laser applications.

Typical Applications

  • Commonly used in imaging applications, including photography, due to its enhanced imaging capabilities.
  • LiDAR and other laser systems to collimate and focus the laser beam.
  • Other applications include objectives lens in telescopes, medical devices, borescopes, image relay, and analytical devices.

Our 2021/2022 Catalogue

Inside Knight Optical’s catalogue you’ll find details of the industries we serve as well as the many other services we can offer. It also showcases hundreds of our most popular products, supported by useful technical information, to help you choose the right part for your application.
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