Industrial Automation Magazine India

Diffraction-Limited, High-Precision Aspheres: MRF Polished

Published on : Tuesday 30-11--0001

Features

• High Strehl Ratio: >0.80
• Three Diameters: 12.5 mm, 25.0 mm, and 50.0 mm
• Three Focal Lengths: 25.0 mm, 50.0 mm, and 100.0 mm
• Ideal for Diffraction-Limited Collimation and Coupling

Thorlabs offers aspheric lenses that provide true, diffraction-limited performance for on-axis beam focusing and collimation. This is achieved by a combination of Computer Numerical Controlled (CNC) machine polishing and high-precision Magnetorheological Finishing (MRF). For monochromatic sources, spherical aberration is often what prevents a single spherical lens from achieving diffraction-limited performance when focusing or collimating light. The lenses found on this page are free of such aberrations, and offer the best single-element solution for many on-axis applications including collimating the output of a fiber, coupling light into a fiber, spatial filtering, or imaging light onto a detector. Our high-precision aspheric lenses achieve Strehl ratios of >0.80, the highest of any Thorlabs lens.

Our N-BK7 high-precision aspheric lenses are available in three sizes: Ø12.5 mm, Ø25.0 mm, and Ø50.0 mm. They are offered uncoated or AR-coated for 650 nm - 1050 nm.

If an unmounted aspheric lens is being used to collimate the light from a point source or laser diode, the side with the greater radius of curvature (i.e., the flatter surface) should face the point source or laser diode. To collimate light using one of our mounted aspheric lenses, orient the housing so that the externally threaded end of the mount faces the source. Note that the numerical aperture of your lens should be greater than or equal to the numerical aperture of the light source.

Superior Optical Performance

In order to reach diffraction-limited performance, a lens must meet two criteria: it must be designed to eliminate aberrations and the design must be executed without any manufacturing errors distorting the wavefront. To the upper right are two contour plots which compare one of our High-Precision, CNC-Polished Aspheric Lenses (Right) to a Diffraction-Limited, MRF-Polished Aspheric Lens (Left). Our Diffraction-Limited, MRF-Polished line of Aspheric Lenses have the lowest wavefront error of any of our other imaging optics. For more information on how these lenses perform compared to our other lines, see the Lens Comparison tab.

Optical Performance Verification

Each lens undergoes in-process verification in order to achieve optimum performance. This is handled primarily by the Zygo Verifire™ Asphere Interferometry Metrology Station. All of our polishing machines have software which communicates with our metrology, allowing fast, accurate, and consistent adjustments to our aspheric lenses. Metrology data can be provided on request; contact Tech Support with inquiries.

Custom Aspheric Lenses

Thorlabs' diffraction limited, high-precision aspheric lenses are manufactured at the production facility housed in our headquarters in Newton, NJ. Our optics business unit has a wide breadth of manufacturing capabilities that allow us to offer a variety of custom optics for both OEM sales and low quantity one-off orders. Custom lens diameters, focal lengths, substrates, coatings, and mounting options are available with prices that are comparable to our stock offerings. For more information, please see the Custom Capabilities tab or contact Tech Support to inquire about a custom order.

Common Specificationsa,b
Outer Diameter Tolerance	+0.00 / -0.05 mm
Numerical Aperture	0.20
Substrate	N-BK7
Surface Quality	40-20 Scratch Dig
Transmitted Wavefront Error	Diffraction Limitedc
Aspheric Surface Accuracy	<55 nm
Slope Error (PV)	<200 µradian
Centration	<1 arcmin

It is used in CNC grinding and polishing Process.

Thorlabs, Inc.(USA)

Tel: 1-973-300-3000

Email: [email protected]