Posted in | Lenses

Advanced F-Theta Lenses for Precision Imaging Systems

Avantier’s F-theta lenses are perfect for high-resolution imaging applications because of their uniform field curvature correction and consistent spot size design.

F-theta lenses are preferred optics for laser scanning, engraving, and cutting systems. For a diverse clientele, Avantier creates high-performing custom F-theta lenses.

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An F-theta lens, sometimes called a plane field objective or scan lens, is an assembly of three or four lenses mounted within a sturdy housing for ease of use and pre-alignment. It enables the user to work with a plane-focusing surface, although a laser beam can be focused on a spherical surface using an ordinary lens. It has a laser spot position proportionate to the scan angle and a spot size nearly constant throughout the scan field. Therefore, it is very helpful when using lasers.

Discover High Precision Optical Assembly: F-Theta Lenses

F-theta lens. Video Credit: Avantier Inc.

Applications of F-Theta Lenses

F-theta lenses are an essential component of many laser scanner systems, particularly those that require a flat imaging field and high resolution. They are frequently used in materials processing operations such as drilling, welding, and laser cutting synthetic materials, as well as image transfer, engraving, and labeling systems.

 These lenses are used in confocal microscopy and ophthalmology in biotechnics.

F-theta lens.

F-theta lens. Image Credit: Avantier Inc.

Why Choose F-Theta Lenses for Scanning Applications

A laser beam is usually moved linearly using scan mirrors or a galvanometer in a scanning system. This makes it possible to guide the laser for engraving, cutting, or drilling. If a regular lens were used to focus the laser, the curved lens surface would cause variations in the beam profile as the distance from the optical axis changed. These modifications to the beam profile may cause variations in optical power and manufacturing flaws.

This issue can be partially resolved using a conventional flat-field scanning lens, which focuses light on a flat surface. However, because the generated image does not change linearly with angle, these lenses introduce additional aberrations and errors. 

F-theta lenses allow for consistent, dependable laser-powered materials processing and eliminate manufacturing errors.

F-theta lens.

F-theta lens. Image Credit: Avantier Inc.

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Key Parameters of F-Theta Lens and Scanning System

The operating wavelength, spot size, and scan field diameter (SFD) are important considerations when designing an F-theta lens for application.

The wavelength of the laser being used is known as the operating wavelength. The term “spot size” describes the laser beam’s width. The diagonal length of the square in which the lens can focus the beam is known as the scan field diameter, or scan length, of an F-theta lens.

Another key characteristic of a scanning system is the output scan angle (OSA). This angle is measured between the perpendicular of the image plane and the output laser beam (the beam after passing through the scan lens). For a telecentric lens, the OSA is consistently zero; for other types, it will vary slightly across the image field.

Factory Standard

Source: Avantier Inc.

. .
Lens Design Compact design with 3 to 4 elements
Transmittance >90%
Distortion (Max.) <0.25%
Focal Length Available from 63 mm to 635 mm
Custom Optical Coating Working wavelength ranges from UV to visible to infrared
Lens Performance Customized to fit specific application needs


Custom F-Theta Lenses at Avantier

Custom F-theta lenses are made to order for customers in the medical, research, and industrial sectors, which is Avantier's area of expertise. With years of experience creating high-performance optical components, optical engineers and designers ensure that each component meets the highest standards through meticulous testing before it leaves the factory.

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