Definition of <I>f</I>-Theta lens

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Photonics Dictionary

f-Theta lens: An f-theta lens, also known as an f-theta scan lens or simply an f-theta lens system, is a specialized optical component used in laser scanning systems, particularly in laser marking, engraving, and cutting applications.

The "f" in f-theta stands for the focal length, and "theta" (θ) represents the angular scan range. An f-theta lens is designed to maintain a constant focused spot size over a defined linear scanning area, typically at a plane perpendicular to the optical axis. This means that as the laser beam scans across the surface, the spot size remains consistent, resulting in uniform marking or cutting depth.

Key features and characteristics of f-theta lenses include:

Constant focused spot size: Unlike traditional lenses, which produce a varying spot size as the scanning angle changes, f-theta lenses ensure that the focused spot size remains constant throughout the scanning range. This uniformity is crucial for achieving consistent results in laser processing applications.

Telecentricity: F-theta lenses often exhibit telecentricity, meaning that the laser beam remains perpendicular to the scanning plane over the entire field of view. This property helps minimize distortion and aberrations, particularly in laser micromachining and precision manufacturing processes.

Compatibility with galvanometer scanners: F-theta lenses are typically paired with galvanometer-based scanning systems, where one or two mirrors deflect the laser beam to scan across the workpiece. The f-theta lens compensates for the non-linear motion of the mirrors, ensuring precise control of the laser spot position.

Field curvature correction: F-theta lenses may incorporate optical elements to correct for field curvature, ensuring that the laser beam remains focused at different positions across the scanning area.

F-theta lenses are essential components in laser systems used for marking, engraving, cutting, and other precision laser processing applications. They play a crucial role in achieving high-quality results, improved efficiency, and precise control over the laser beam's interaction with the workpiece.

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f-Theta lens