What are cylindrical lenses?

Cylindrical lens, also called a cylinder, is an optical lens which focuses light on to a line instead of on to a point, as a spherical lens would. The curved face or faces of a cylindrical lens are sections of a cylinder, and focus the image passing through it onto a line parallel to the intersection of the surface of the lens and a plane tangent to it. The lens compresses the image in the direction perpendicular to this line, and leaves it unaltered in the direction parallel to it (in the tangent plane).

These lenses are used to correct the output from diode lasers, to produce a round beam from the diode’s elliptical output. They are also applied in optical systems to correct the shape of laser beams, change image aspect ratios, and illuminate in the shape of line source.

Applications for Cylindrical lenses

Cylindrical lenses are designed for applications requiring one-dimensional shaping of a light source, able to focus incoming light to a line, or to change the aspect ratio of an image. They have a single cylindrical surface that causes incoming light to be focused in only a single dimension, stretching the image. They are offered in either plano-concave or plano-convex configurations, which are meant to expand or focus light, respectively. Cylinder lenses are available with positive or negative focal lengths, ideal for laser line generation or anamorphic beam shaping to circularize laser outputs.

Sample of Applications: circularize a laser diode beam profile

In a typical laser diode (a P-i-N diode), electrical current flows vertically between contacts on top of and below the semiconductor material substrate. Charge carrier combination and the resulting light emission occurs in the intrinsic region between the doped electrodes. A horizontal optical cavity is formed by cleaving the substrate and polishing the side faces. Fresnel surface reflections at these faces create optical feedback resulting in a lasing effect. Light emitted from a rectangular aperture typically takes on an elliptical beam profile with angle θ1 and θ2 along the major and minor axes. Two cylindrical lenses with focal lengths f2/f1 = θ1/θ2, each positioned their focal length away from the laser diode, may be used to produce a circular collimated beam output.

Materials available for cylindrical lenses

Choosing from substrates of N-BK7 glass, UV fused silica, or CaF2, all of which are available uncoated or with an anti-reflection coating (AR coating).

Production of cylindrical lenses

Cylindrical lens from Phtonchina is among top-level in terms of surface quality, irregularity and dimension tolerance. It also provides the high precision, special shapes and specifications designed by customers.

Photonchina design and manufacture cylindrical lenses(include round versions), plano-convex, plano-concave, acylindrical lenses and cylindrical achromatic doublets. Achromatic cylinder lenses provide additional color correction by minimizing chromatic aberration. Hydrid acylinder lenses are typically used for color correction, in addition to minimizing spherical aberration.

Our precision cylindrical lenses are produced to meet the demanding requirements of laser electro-optic applications. They are manufactured from fine annealed optical glass or other materials designated by customers and are polished to tight tolerances to ensure minimum wavefront distortion. Tight surface quality tolerances minimize scatter and unwanted diffraction effects.

Optical coating

By virtue of over 20 years of experience in designing and operation of optical coating technique, Photonchina uses its vacuum coating equipment imported from Germany or Japan as well as domestic brand to supply a very wide of coating service for customers worldwide.

1. Broadband visible antireflection coating

Our broadband multilayer antireflection coating markedly improves the transmission efficiency of these lenses by reducing surface reflections over a 430-700nm wavelength range. This AR coating performs effectively for multiple visible wavelengths and tunable lasers eliminating the need for several sets of optics.

2. Laser V-coating from Photonchina offers the lowest reflectance at 1064nm for maximum transmission while maintaining high durability and excellent damage resistance. Valuable laser energy is efficiently transmitted through the plano-convex lens rather than lost to surface reflection and scattering. The trade off to its superior performance is the minimal laser line wavelength range.

Lenses made by Photonchina have especially been suited for sensitive laser applications, including laser scanning, diode laser beam shaping. Additional applications include focusing light into a thin line for optical metrology or collecting light in spectroscopy systems. They can also be used to expand the output of a laser diode into a symmetrical beam.

General comments on manufacturing limits for Photonchina

This represents a general list of soft limits and is intended for reference only.

As requirements move closer to a min or max shown, fabrication becomes more difficult.

Certain combinations are attainable, with extra significant fixturing costs, e.ge. crossed axis cylinders, cylinders/spheres.

Aperture coverage is often limited by the range of diffractive nulls available.

Length is always the dimension along the plano axis and width is the dimension across the power axis.

Capabilities

Attribute          Standard level         Premium        Photonchina’s Ability

Diameter(mm)            +/-0.100          +/-0.025                +/-0.015

Central Thickness(mm)   +/-0.150         +/-0.050                 +/-0.015

Radius (the larger one)   +/-1.0%           +/-0.5%                 +/-0.1%

Surface Quality           60-40                 40-20              10-5

Irregularity               1/4 Lambda        1/8 Lambda         1/15 Lambda

(Plano Surface)          or 0.5fr           or 0.25fr                 or 0.15fr

Irregularity                1/2 Lambda        1/4 Lambda         1/8 Lambda

(Cylindrical Surface)     or 1.0fr              or 0.5fr             or 0.25fr

Centration(arc min)         +/-8                  +/-3                     +/-0.5

Note

The surface quality data above is based on area of 20mm*20mm

The irregularity data shown is based on per inch in dimension L.

The data of centration is based on each 20mm in dimension L.

Photonchina manufactures a complete range of cylindrical lenses as follows,