What are Cylinder Lenses?

Creating a Laser Line Generator | Creating Circular Beams | Selection Guide

Cylinder lenses are a type of lens that have differing radii in the X and Y axes, causing the lens to have a cylindrical or semi-cylindrical shape, and image magnification in only a single axis. Cylinder lenses are commonly used as laser line generators, or to adjust image height size or correct for astigmatism in imaging systems.

Figure 1: Plano-Convex Circular Cylinder Lens

Figure 2: Plano-Convex Rectangular Cylinder Lens

Figure 3: Plano-Convex Oblong Cylinder Lens

Creating a Laser Line Generator

When using a cylinder lens as a laser line generator, it is important to calculate the required Effective Focal Length $ \small{\left( \text{EFL} \right)} $ for the application. To do so, first calculate the fan angle $ \small{ \left( \theta \right)} $ using the needed line length $ \small{\left( x \right)} $ at the given working distance $ \small{\left( L \right)} $ in centimeters:

(1)$$ \theta = 2 \cdot \tan^{-1}{\left( \frac{x}{2 \, L} \right)} $$

The fan angle can also be used to determine the line length at a given working distance:

(2)$$ x = 2 \cdot L \cdot \tan{\left( \frac{\theta}{2} \right)} $$

Figure 4: Visual Illustration of Equations 1 – 2 for Creating a Laser Line Generator

The $ \small{\left( \text{EFL} \right)} $can then be calculated using the input beam radius $ \small{ \left( \frac{d}{2} \right) } $ and the following equation:

(3)$$ \frac{d}{2} = \text{EFL} \cdot \tan{\left( \frac{\theta}{2} \right)} $$

Figure 5: Visual Illustration of Equation 3 for Calculating Effective Focal Length

Creating Circular Beams

Typically, laser diodes emit elliptical-shaped beams that may be unsuitable for applications that require a collimated, circular laser source. Using two cylinder lenses is a common method to circularize an elliptical beam - the first lens magnifies the minor axis of the laser diode, and the second lens collimates the beam. The curved side of the lenses and the minor axis of the laser diode should be oriented so that the minor axis is magnified.

For example, to modify an elliptical beam with a 4.0mm major axis and a 1.0mm minor axis to a circular beam with a 4.0mm diameter, the minor axis needs to be magnified by 4X. The magnification power (Mag) of a two-lens setup can be calculated by dividing the focal length of the second lens $ \small{\left( f_2 \right)} $ by the focal length of the first $ \small{\left( f_1 \right)} $.

(4)$$ \text{Mag} = \frac{f_2}{f_1} $$

One way to achieve the required magnification is to use a 25mm diameter x -25mm EFL PCV Cylinder Lens (#46-196) with a 25mm diameter x 100mm EFL PCX Cylinder Lens (#46-018). Two PCX cylinder lenses can also be used, but add additional length to the system. The use of cylinder lenses also decreases beam divergence, increasing the beam’s collimation, which is ideal for long-distance projection applications. To help in selecting the right cylinder lens for any application, refer to Table 1.

Cylindrical Lens Selection Guide

Ready to purchase a cylindrical lens? Edmund Optics supplies a wide variety of cylinder lenses to choose from. Use our cylindrical lens selection guide below, or visit our cylindrical lenses page to view our full range of lenses.

Table 1: Cylinder Lens Selection Guide
Type	Wavelength	Ideal Application
Fast Axis Collimators	0.8 – 1.0μm	Collimating high power laser diode bars
Illunimation PCX Cylinder Lenses	0.4 - 1.6μm	Focusing a laser to a line or circularizing a laser beam
UV Fused Silica PCX Cylinder Lenses	0.2 - 2.2μm	Operating in harsh or rugged environments
Achromatic Cylinder Lenses	0.4 - 1.0μm	Creating line profiles of broadband light sources
Plastic Hybrid Acylinder Lenses	0.4 - 1.6μm	Creating line profiles of broadband light sources
Illumination PCV Cylinder Lenses	0.4 - 1.6μm	Beam expansion
Cylindrical Microlens Arrays	0.2 - 2.2μm	Beam homogenization

Still not sure which type of cylindrical lens would be best for your application, and need some more guidance? Contact us and an expert will help you choose the best cylinder lens for your application.