F-Theta lenses for large scanner apertures

09. June 2017

With ongoing improvements in the development of laser systems, laser intensities are still increasing with the goal of enabling faster processing speed. This progress does result in ever increasing requirements for lenses. 

In order to minimize the chance of damage and reducing thermal effects, increasing the initial beam size is a solid option. Thus scanner systems with large mirrors experience a rising 


Another side effect of large scanner apertures is their influence on the focus spot diameter. The larger the incident beam, the smaller the final spot diameter at the focus point can be.

Meeting these requirements Sill Optics is presenting 

a new f-theta lens made fully of fused silica. It is dimensioned for large scanner apertures up to Ø30 mm with an effective focal length of 420mm at 1064 nm. Along the design guideline of Sill this lens has no internal ghosts and is diffraction limited. On a scan area of 180 mm x 180 mm spot sizes of about 15.5µm are possible (simulation with Ø30 mm scanner aperture, Ø20 mm input beam diameter, and 1064 nm with M²=1).

This new release is the start of a new f-theta lens 

series specially designed for Ø30 mm-scanners.

Furthermore, the slightly smaller scanners with Ø20 mm are not left out in the cold. With the new S4LFT2340/328, we present a 340mm 

focal length F-Theta lens, which is able to achieve spot sizes down to 16µm on a 61 mm x 61 mm field at 442 mm working distance.