λ/4-λ N-BK7 Plano-convex Lenses
Plano-convex (PCX) lens is an optical lens with one plane face and one convex face, and a positive focal length, utilized for collecting, focusing collimated lights, collimating lights from a point source, or reducing the focal length of a lens group. Compared to Biconvex lenses, Plano-convex lenses have two unidentical sides and therefore work best for an infinite absolute conjugate ratio (objective distance: image distance). However, plano-convex lenses still reduce spherical aberrations to a quite low extent when the absolute conjugate ratio is greater than 5:1. For conjugate ratio below 5:1, consider using plano-convex lenses in pairs or a biconvex lens.
N-BK7 glass is a RoHS-compliant borosilicate material prevalent for uses in the visible and NIR spectrum (in particular when it comes to manufacturing precision visible components). N-BK7 features high optical homogeneities, great resistance to scratches and abrasions, low cost, and low inclusion content, it is an ideal substitute for UV Fused Silica when high UV transmission is not required, and a preferred alternative for CaF2 at the 1.65-2.3 micro-operating wavelength region with the concern of lower manufacturing costs.
Hangzhou Shalom EO offers Stocked and Custom N-BK7 Plano-convex Lenses with a diameter range of 0.5-300mm, that allows for flexible incorporation into various optical systems like emitters, detectors, imaging instruments, lasers, fiber optics, etc. Our N-BK7 plano-convex lenses have a wide optional diameter range of 6-75mm, and a focal length range of 10-1000mm, while other dimensions and focal lengths could be customized. These lenses feature λ/4-λ irregularities and 40/20 scratch/dig. Each piece of the lens will undergo strict inspection in Shalom EO’s in-house labs before dispatch to secure your interest. Our inspection procedure includes an in-process checking stage of the optical properties of lenses and a final test of coatings, dimension precisions, and the visual observation of scratch/dig, apertures, inclusions, etc.
Note that the transmission range of NBK7 is 350-2200mm, with an absorption dip positioned at around 2.8 microns. To further enhance the transmission of the NBK7 plano-convex lens and elevate the efficiencies of complex optical instruments. , Shalom EO offers two types of anti-reflection coatings. The standard N-BK7 plano-convex lens could be uncoated or coated with our Broadband AR coatings (typical wavebands 350-650nm, 400-700nm, 650-1050nm, 700-1100nm, 1050-1580nm, 1100-1650nm) to accommodate multi-spectrum and tunable laser applications. Besides the BBAR coatings, V coatings, which are a special form of AR coatings that deliver an ultra-low reflection at a narrow band of designed wavelengths are available upon custom request, too.
Application Notes:
1. Because the refraction angles of the incident lights have a slight difference, the focal length of the two sides is also different. To minimize spherical aberration, engineers from Shalom EO suggest that when using the lens to focus collimated lights, the collimated lights should be projected to the curved surface of the lens; conversely, when using the lens to collimate a point light source, the light source should be incident on the flat surface.
2. Simplified Calculation of Focal Length of a Plano Convex Lens: focal length = R/(n-1), where R is the radius of curvature and n is the refractive index.
