During laser operation with several kilowatts, the focusing lens absorbs a small portion of the laser power and gets heated. The absorption takes place mainly in the AR coatings and at dirt on the lens.
Absorption is typically 0.2% of the incoming laser power on a new clean lens with standard AR coating as against 0.15% on a lens with Ophir’s Black Magic coating. During use in a laser cutting machine, absorption increases gradually due to increasing amounts of dirt on the lower surface. At the time of replacing the lens, absorption usually is in the range of 0.3 to 0.4%.
Heating of the lens causes additional surface curvature due to thermal expansion, also increasing the refractive index of the lens material. Consequently, the lens’ focal length becomes shorter, and the focus position cannot be predicted exactly because it depends on many parameters such as laser power, intervals, laser on/off and cleanliness of lens.
Lenses with reduced absorption can therefore, make the focal length more stable and improve reliability of the laser cutting process.
Key features of Ophir Black Magic laser lenses:
- Guaranteed absorption <0.15% constant throughout the lens’ lifetime
- Maximum focus stability
- Industry-leading tough coating with remarkable durability
- Ability to withstand back spatter
- Easier to clean and maintain
- Resistant to humidity
- Radioactive-free coating
- Recommended and approved by leading OEMs
- Used for all high powered CO2 lasers including those over 5KW
- Excels in cutting aluminium and stainless steel
- Superior price-benefit ratio