f theta lens
lens package
f theta lens 110
f theta lens 175mm

ZALS series

F – Theta Lens For Fiber Laser Marking Machine

  • High light transmittance, high output laser energy
  • Marking area is optional from 100mm to 300mm
  • High-quality coating, good protection, uniform laser light
  • Suitable for a variety of fiber laser marking machines with a laser wavelength of 1064nm
  • High quality, not easy to damage
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What can F theta lens do for you?

In recent years, laser marking technology has become one of the largest application areas of laser processing, and its features such as fast marking speed, clear writing, strong anti-counterfeiting function, and low pollution have attracted wide attention from the industry. Working near the focal plane of the objective lens. The lens is called an F-theta lens.


f theta lens applications


In the marking system, the laser beam passes through the F theta lens system and will produce off-axis deflection. Relative to an ideal plane, abnormal images or distortion will appear on the marking surface. Simply put, the laser is scattered by the F theta lens to form a relatively fixed focal length and marking range. For example, our usual marking range for lasers is 100mm x 100mm. If you want to mark a larger range of content, you need to replace the F-theta lens with a large marking range.

What are the different effects of using different f-theta lenses for the same laser machine?

Here is the video we test the lens (marking area 100mm x 100mm)and the lens (marking area 200mm x 200mm)

Because the laser output energy is constant, so when you replace a larger range lens, the output laser energy will be reduced, because the laser energy is scattered, so we usually recommend that customers choose high output power laser marking machines, such as 30W, 50W, 60W, so that it can adapt to a larger marking area F theta lens

How to Replace the F- theta Lens and What Settings to Do after Replacement?


As you can see from the above video, it is very easy to replace the field lens, but we still have a lot of work to do after replacing it, you need to adjust the focal height of the laser head and adjust the accuracy of the marking area of the laser head, then adjust the position of the red light positioning offset, etc.

What are the Details of Our F Theta Lenses?

Type F160-W1064 F160-W1064 F254-W1064 F254-W1064 F435-W1064
Focal length 162mm 210mm 254mm 300mm 435mm
Back focal length 194.62mm 256.3mm 298.75mm 364.64mm 486.66mm
Work wavelength 1064nm 1064nm 1064nm 1064nm 1064nm
Scan angle +/-27 degree +/-28 degree +/-28 degree +/-28 degree +/-28 degree
Squire field size 110mm*110mm 150mm*150mm 175mm*175mm 207mm*207mm 300mm*300mm
Incident beam diam.(Max.) 12mm 16mm 16mm 16mm 18mm
Recommended mirror separation 16mm 16mm 16mm 16mm 16mm
Y mirror distance 16mm 18mm 18mm 18mm 18mm
X mirror distance 32mm 34mm 34mm 34mm 34mm
Encircled Energy(80% energy) 12.5um 18um 20um 21um 22um
Max Diameter of lenses 76mm 91mm 91mm 96mm 115mm
Mounting thread M85*1 M85*1 M85*1 M85*1 M85*1

How to Choose the Right F- theta Lens for Your Needs?

To select an F theta lens, the main technical parameters to consider are the laser working wavelength, incident pupil, scanning range, and focused spot diameter.
Working wavelength: mainly depends on the wavelength of the laser, the lens is coated in the given laser wavelength. If the lens is not used in the given wavelength range, then it will be burned by the laser. Normally Fiber laser working wavelength is 1064nm.

Incident light pupil: If a single lens is used, the reflector is placed at the entrance pupil, and the diameter of the maximum usable beam is equal to the diameter of the entrance pupil.

Scanning range (marking range): The larger the range that the field lens can scan, the more popular it is by users. However, if the scanning range is increased, the focus spot becomes larger, and the distortion degree also increases. In addition, to increase the scanning range, the F theta lens focal length and working distance should also be increased. The working distance is longer, which inevitably leads to the loss of laser energy.

There is also a focus spot diameter that is proportional to the focal length, which means that increasing the scanning range, focus spot diameter followed by increasing the spot is not fine enough, the laser power density decreases very quickly, which is not conducive to processing. Therefore, it is not that the larger the marking range, the better the F theta lens, you need to choose the appropriate one according to your needs.

Focused spot diameter: For a scanning system with incident laser beam diameter D, field lens focal length F and beam quality factor Q, the focused spot diameter d = 13.5QF/D (mm). Therefore, a beam expander can be used to obtain a smaller focused spot.