ZnSe Telecentric Scan Lenses for CO₂ Lasers

Application Note Serial No.: AN-SGBN-03-03-26

Wavelength Opto-Electronic’s TSL series telecentric scan lenses are built for galvo-based processing with 9.4 µm and 9.6 µm CO₂ lasers. The beam arrives perpendicular to the workpiece across the entire scan field, delivering consistent hole geometry, straight cut walls, and uniform marking from center to corner. Seven models cover fields from 9 × 9 mm to 90 × 90 mm.

1. Why 9.4 / 9.6 µm

Most CO₂ lasers emit at 10.6 µm. Sealed-tube and RF lasers tuned to 9.3 to 9.6 µm are increasingly used because many materials absorb more strongly there:

• PET film and plastics: cleaner cuts with less heat-affected zone
• Glass and ceramics: better absorption and less micro-cracking
• Paper, cardboard and packaging film: sharper edges, less charring
• Thin-film and flexible electronics: more precise material removal

A lens optimized for 10.6 µm has a coating tuned to that wavelength. Wavelength Opto-Electronic’s TSL lenses are designed and AR-coated for 9.4 to 9.6 µm, so transmission stays high where you actually operate.

2. Why Telecentric

A standard f-theta lens delivers the beam at increasing angles toward the edge of the field. A telecentric design keeps the chief ray parallel to the optical axis everywhere. This matters for:

• Via drilling and hole cutting: holes are cylindrical, not tilted or elliptical
• Cutting thick or layered material: no edge taper or side-wall skew at the field edge
• Marking and engraving: uniform depth, contrast and spot shape across the field
• Uneven surfaces: small height variations do not cause position error, because the beam stays perpendicular

Trade-off: a telecentric lens needs elements at least as large as the scan field, so the field is limited relative to a comparable non-telecentric f-theta lens. That is why the field sizes below are moderate.

3. Wavelength Opto-Electronic ZnSe Telecentric Scan Lenses

4. Choosing a ZnSe Telecentric Scan Lens

• Fine detail and micro-processing (9 × 9 mm): TSL-9.4-9-40-D14 gives the smallest spot (~34 µm) for fine marking, thin-film scribing and small-area micro-drilling.
• Compact mid-field work (50 × 50 mm): the 75 mm model gives the tightest spot at this field, while the 100 mm model gives more working distance (118.8 mm), which helps with fume extraction, fixtures and air assist.
• Larger fields, faster throughput (70 to 90 mm): TSL-9.4-70-120 and TSL-9.4-90-170-D20 process larger parts in one scan, at the cost of a larger spot.
• 9.6 µm users: TSL-9.6-70-140ZA is tuned for 9.6 µm sources over a 70 × 70 mm field.
• Mid-to-large field with a small beam: TSL2-9.4-60-100Z-D14 gives a 60 × 60 mm field with a 14 mm entrance beam and the longest working distance in the range (130.9 mm).

5. ZnSe Telecentric Scan Lenses Applications

1. PET and plastic film cutting and perforation: clean edges with minimal melt at 9.3 to 9.6 µm
2. Glass and ceramic marking: high-contrast marks with low cracking risk
3. Paper, label and packaging cutting: consistent edge quality across the field
4. Flexible PCB and thin-film processing: perpendicular drilling and scribing
5. Precision engraving of wood, leather and acrylic: even depth over the whole field

6. Conclusion

Moving to 9.4 µm and 9.6 µm CO₂ lasers can improve cut quality and reduce heat damage on PET, glass, ceramics, paper and thin films. To get the full benefit, match the scan lens to the wavelength. A telecentric design keeps the beam perpendicular across the whole field, so holes, cut walls, and marks stay consistent from center to corner.

Wavelength Opto-Electronic’s TSL series covers fields from 9 × 9 mm to 90 × 90 mm in seven models. These range from the 40 mm focal length lens for fine micro-processing to the 170 mm lens for large-area work. All are ZnSe and AR-coated for 9.4/9.6 µm. Choose the field size for your part, the entrance beam for your beam expander and galvo, and the working distance for your fume extraction and fixtures.