"; _cf_contextpath=""; _cf_ajaxscriptsrc="/cfthorscripts/ajax"; _cf_jsonprefix='//'; _cf_websocket_port=8578; _cf_flash_policy_port=1244; _cf_clientid='E3D76F85BC153CEC5AA7E5DDCCAE88A1';/* ]]> */
Fresnel Lenses (Right) Consist of Sections with
Click to Enlarge
Excel Spreadsheet with Raw Data
The shaded region in this plot denotes the spectral range over which we recommend using these lenses. All our Fresnel lenses have a nominal thickness of 1.5 mm, and only minor differences are observed for different focal lengths.
Click to Enlarge
Ø2" Fresnel Lens in 60 mm Cage System with LCPA1 Alignment Plate to Check Beam Diameter and Centration
Thorlabs' Fresnel Lenses offer light focusing and collimation without the bulk associated with traditional lenses. Our Fresnel lenses are effectively 1.5 mm thick across their entire diameter, and this uniform thickness, combined with the optical-grade acrylic substrate, reduces their weight by over 90% versus glass lenses of comparable focal length and diameter.a These properties make them ideal for building compact optical systems.
Our lenses are offered in 1/2", 1", and 2" diameters, and they provide high transmission in the 400 - 1100 nm spectral range (see graph at right). As shown in the schematic at the top of the page, they consist of a grooved side and a plano side. In order to minimize the substrate thickness, stepwise discontinuities are introduced at regular radial spacings, creating grooves. Hence, Fresnel lenses can be thought of as a series of concentric rings.
Fresnel lenses are often used to homogenize the output of LEDs, focus light onto a point detector, or concentrate sunlight into solar cells. For the lenses sold on this page, each step has a 10° pitch (illustrated by the diagram in the Specs tab). This pitch angle causes distortions that make the lenses unsuitable for imaging applications.
To mount our Fresnel lenses, we recommend using our LMR05(/M), LMR1(/M), or LMR2(/M) Fixed Lens Mounts, which use a retaining ring to secure the optic. Do not overtighten the retaining ring since this may cause the grooves to wear. Our rubber Stress-Free Retaining Rings can be used in place of the standard aluminum rings to reduce the stress on the optic surface. The grooved side of the lens should be oriented to face the collimated beam, and the plano side should face the divergent source. The JEL10 Eye Loupe can help determine which side of the lens is grooved. Since the lenses are only 1.5 mm thick, they are too thin for mounts that hold optics with setscrews.
a. Weight reduction calculated by comparison to our Aspheric Condensers with Diffusers.
Click to Enlarge
This schematic defines the groove spacing and pitch angle in our Fresnel lenses. Note that the lengths are not to scale.
The linked Zemax files are a theoretical approximation of the performance of each lens. In place of a grooved structure, each file models a sloped surface with infinitesimal thickness at each radial position. This creates limitations, including the inability to view scattering information due to the pitch and groove spacing of the lens. In addition, the optical coefficients in each file are not from the data used at manufacturing; the coefficients are calculated using the necessary optical prescription to focus collimated light at the proper axial distance from the back surface of the lens. These limitations reduce the realistic modeling of the Fresnel lenses sold below.