Comparison CO2 Laser vs. Excimer Laser
CO2 laser in Ophthalmics Excimer laser in Ophthalmics
A CO2 laser is a continuous laser that works at An Excimer laser is a puls laser that works at 193nm, 10.600nm wavelength. The engraving is performed which is low UV. The engraving is performed by a by evaporating material from the substrate. The phenomenon called “cold ablation”. The molecular required amount of heat is transmitted to the surface structure is cracked by condensed energy without in milliseconds which brings thermal stress to the applying any thermal effects to the surface. engraving area and its neighboring areas.
Applying heat to organic substances leads to As no heat is transmitted, carbonisation can not carbonisation where the material is not evaporated. occur.
The heat destroys the surface of finished and/or All coated substrates can be engraved with beautiful coated lenses like Transitions or Polarizers. results. The surfaces are not destroyed.
The intense heat can cause microcracks and As no heat is applied during engravings the material cavities. During tinting pigments will accumulate in does not suffer any thermal stress, microcracks can these cavities, leading to unwanted disturbing not occur. The shape of all engravings is smooth and visibility of the engravings. even.
Another problem is the “memory effect” that can be As the material is smoothly removed by cold found in a certain percentage of the lenses. Users ablation, no memory effect can be found. Re-heating experience disappearing engravings when a lens is the lenses has no effect on the engravings. Coating heated while tinting or coating. Reject rates due to layers smoothly cover the surface, pigments cover disappearing engravings can rise up to 4%. the lens evenly.
CO2 lasers require cooling for higher stability. Still The Excimer does not require any cooling. Engraving occuring instabilities can lead to disappearing is performed with absolute stability by controlling the engravings while hardcoating. voltage.
CO2 laser instabilities can also cause too high The absolute stability allows results which are visibilities, which will permanently disturb the wearer reproduceable in the nm range. All engravings will be of the glasses. identical.
CO2 lasers can only work with one dot size. Excimers can work with unlimited numbers of dot Controlling visibilty by choosing a different dot size is sizes. Engraving visibility can be perfectly controlled. not possible. Microengraving for tracing can not be Microengraving is possible down to character heights used. of 40µ.
CO2 lasers have no integrated z-measurement Excimers from OptoTech always have a z- system. Engraving finished or semifinished lenses measurement system that allows the laser to find its for branding is not possible as the laser can not find focus. Excimers are the perfect lasers for branding its focus lenses, even after coating.
CO2 Engraving Excimer Engraving
High Infrared Laser Light Deep Ultraviolet Laser Light
Excimer Lasers remove particles in molecular form CO2 Lasers burn the surface, material evaporates through high energy beam
Engraving effect by extreme heat Engraving effect by Cold Ablation
Engraving area is highly heat affected No Heat Affected Zone
The heat causes micro-cracks and roughness No heat - No cracks - No roughness
The cracks cause problems for tinting and coating No cracks - No problems for tinting and coating
When engraving coated and tinted lenses, the No problem for engraving coated or tinted lenses surface will be destroyed by heat
Engravings can partially or totally disappear when Engraving is permanent heating the lens e.g. while tinting or coating
Engraving Transitions is impossible Engraving Transitions with perfect quality
Engraving mineral lenses is impossible Engraving mineral lenses with perfect quality
CO2 lasers are not very stable in energy, engraving Perfect control of energy and engraving depth, all strength will vary engravings will look absolutely the same
Conclusion:
CO2 Lasers are applicable in very small productions with low budgets and low quality requirements.
Excimer Lasers are recommended for any application with medium to high quality requirements. For a professional lens production Excimer Lasers deliver the best possible engraving result.