Optical Lenses
An Achromatic Lens, or called Achromats, is a specially designed optical lens that converges or diverges light while minimizing chromatic aberration and offering attenuated spherical aberration than a singlet lens. The major difference between an achromatic lens and a singlet chromatic lens is that a singlet splits up white light and has variable peripheral focal lengths. In contrast, an achromatic lens, such as an achromatic doublet or achromatic triplet, is optimized for infinite conjugate ratios and compensates for chromatic and spherical aberrations, aligning two or more wavelengths to the same focal point. In general, achromatic lenses correct the following optical aberrations:
1. Chromatic aberration, also known as chromatic distortion/color fringing, is a common issue that naturally occurs in average lenses where different wavelengths of light focus at different points along the horizontal or vertical optical axis, leading to blurring of images and larger focused spot size. Chromatic abberation is intrinsic in conventional lenses when the light source is a white light or contains more than one wavelength (in reality, no light source is genuinely single-wavelength) and due to the dispersive nature of optical lens materials. Typical achromatic lenses for visible light correct for red and blue color lights.
2. Spherical aberrations occur when light rays passing through different zones of a lens (central vs. peripheral) focus at different points, causing blurring. An achromatic lens is usually a doublet made from a positive lens and a negative lens. By carefully choosing the curvatures and materials, the designer can also balance out some of the spherical aberration introduced by one element with the other. In addition, chromatic aberrations, which are an off-axis aberration where point sources appear comet-shaped instead of round, are particularly noticeable at large apertures. Achromatic lenses, due to their better aberration correction, maintain small spot sizes (high resolution) without needing to reduce the clear aperture.
Freedom from chromatic, spherical, and coma means that achromatic lenses can provide constant focal lengths regardless of aperture size change and operating wavelength. Achromatic lenses are the cost-effective option for polychromatic illumination, visual imaging systems like microscopes, telescopes, and precision laser applications to where image clarity and color accuracy are required. The most common type of achromatic lenses is achromatic doublet lenses, consisting of two lens elements made of materials with different dispersion properties. An achromatic doublet lens consists of a convex lens of low refractive index and low-dispersion crown glass with a concave lens of high refractive index and high-dispersion flint glass. With such a combination in an achromatic doublet lens, the dispersion of the positive lens element will be cancelled by the second negative lens element.
Hangzhou Shalom EO supplies Off-the-shelf and Custom Achromatic Lenses. The achromatic lenses ensure small focused spots and stable focal length at different wavelengths.
Shalom EO’s Standard Achromatic Lenses:
Shalom EO’s standard achromatic lenses are cemented, unmounted, AR-coated achromatic doublet lenses, featuring a wide selection of positive and negative focal lengths and standardized diameters. The lenses are constructed by one lens made of high refractive index and one lens made of low refractive index.
Our stock achromatic lenses are coated achromatic lenses that come in three coating options: 350-650nm, as in the visible spectrum; 650-1050nm, as for the visible to NIR wavelength range; 1050-1580nm, as for the near-infrared wavelength range. The stock positive achromatic doublets have focal lengths ranging from 7.5mm to 1000mm, and the stock negative achromatic doublets have focal lengths ranging from -100mm to -20mm.
Shalom EO’s Custom Achromatic Lenses:
The custom achromatic lenses have 1.0mm to 300mm in diameter for selection. Aspheric achromatic lenses with minimized spherical aberration are also available in Shalom EO.
