Doublet lenses Doublet lenses are used to produce a higher quality image than singlet lenses of which they easily out perform, even in monochromatic light. Doublet lenses are made up of two different types of glass, a flint and crown glass. These doublet lenses are designed to correct spherical aberration and coma as well as for chromatic aberration. Freedom from spherical aberration means that the focal length is independent of aperture. Doublet lenses performance and usages depend on the relative aperture. All but the largest apertures are diffraction-limited on axis and give excellent imaging over a small field (say 5°) as required for microscopes etc. Negative doublets are commonly inserted between an objective and its image to increase the tube length (as in microscopy) or magnification (as in astronomy) they are therefore optimised for these conditions of 2x.
Knight Optical > Lenses > Doublet lenses - Achromatic Quality Grade > Positive doublets > 4 to 5 diameter (mm) Only UK and EU customers are charged VAT at 17.5%, customers outside the EU and EU customers based outside the UK who have a valid EU VAT number will not be charged VAT Bulk Discounts! Where (B) appears next to a price below, bulk prices are available, click the (B) button to view! PDF Part No. Focal length (mm) Diameter (mm) Back focal length (mm) Design aperture (mm) Centre thickness (mm) Edge thickness (mm) Price Qty Buy LDB0504 5 4 3.1 3.3 3.6 2.7 £45.90 LDB0604 6.3 4 4.8 3.15 3.6 2.8 £47.99 LDB2005 20 4.7 18.25 4.2 3.6 3 £21.50 LDB2505 25 4.7 23.45 4.2 3.2 2.73 £21.50 Knight Optical > Lenses > Doublet lenses - Achromatic Quality Grade > Positive doublets > 4 to 5 diameter (mm)
Specification   Material: Flint and crown glass Diameter: +0.0 / -0.10mm Centring Accuracy: < 0.1mm (F.L 40mm) < 2.5mrad (F.L > 40mm) Focal Length: ± 0.1% (10mm) ± 1% (>10mm) Surface Quality: <40-20 scratch/dig
Specific requirements We can manufacture Doublet Lens to any quality or size at short notice, so if your requirements are not listed please contact us by telephone/ fax or email: stockrequirement@knightoptical.co.uk Coating Doublet lenses are coated on both faces with SLAR (see coatings section) Options available   · Mounting (all items)   · Stock lenses can be edged to smaller diameters