Protection lenses sit between the cutting head’s optics and the workpiece, shielding the expensive focus lens from spatter, dust, and condensation. They’re consumables \u2014 they need regular replacement. But not all protection lenses are equal, and the specifications matter.<\/p>\n
Transmittance is the percentage of incident light that passes through the lens. At 1064nm (the wavelength of fiber lasers), you want 99%+ transmittance per surface. Lower transmittance means heat absorption inside the glass \u2014 which degrades the lens faster and can cause catastrophic thermal fracture at high power.<\/p>\n
Our AR-coated protection lenses achieve <0.2% reflectance per surface<\/strong>, meaning 99.8% transmittance. Uncoated fused silica sits around 96% \u2014 acceptable for low-power (\u22643kW) applications but not recommended for 6kW+.<\/p>\n Damage threshold is measured at a specific pulse width (typically 10 nanoseconds). Our Series A protection lenses are rated at >15 J\/cm\u00b2 at 10ns<\/strong>. For CW (continuous wave) fiber lasers, the relevant parameter is power density in W\/cm\u00b2.<\/p>\n As a rule of thumb: if your cutting head uses a 30mm-diameter nozzle at 6kW, the optical intensity at the protection window is well within the rated threshold. At 12kW+, specify our dual-AR Series C lenses which are rated to 24 J\/cm\u00b2.<\/p>\n Surface quality in the MIL-PRF-13830B specification (scratch\/dig notation) describes allowable surface defects. 20\/10 is tighter than 40\/20 \u2014 fewer and smaller scratches. For protection lenses in high-power laser heads, specify 20\/10 or better. Our standard range uses 20\/10 for all AR-coated lenses.<\/p>\n Protection lens diameter must match your cutting head’s lens seat. Common diameters and their typical head fitments:<\/p>\nDamage Threshold: What “15 J\/cm\u00b2” Means in Practice<\/h2>\n
Surface Quality: 20\/10 vs 40\/20<\/h2>\n
Size Selection<\/h2>\n