In the eyewear industry, laser marking is an established solution for imprinting logos, traceability codes and technical information on frames, lenses and components. However, the choice between UV lasers and CO₂ is by no means secondary: each technology has well-defined application characteristics related to the nature of the materials being processed and the manufacturer’s quality objectives. Understanding these differences makes it possible to set up an effective marking process, avoiding aesthetic defects, readability problems or substrate damage.
Materials and processes in eyewear: a heterogeneous landscape
Modern eyewear is characterized by a wide variety of materials: cellulose acetate, TR90, nylon, polycarbonate for frames; mineral glass and CR-39 for ophthalmic lenses; and light metals such as titanium and aluminum alloys for structural components. Each material responds differently to laser energy, and this response depends strictly on the wavelength of the source used.
From a manufacturing perspective, marking must meet both functional (traceability for regulatory compliance, inventory management) and aesthetic (brand logo, size and pattern indications) requirements. In many cases, the process takes place on curved surfaces or small components, making the accuracy and repeatability of the laser system crucial.
CO₂ laser: principle of operation and areas of use
The CO₂ laser emits infrared radiation at 10,600 nm, a wavelength that is absorbed very effectively by organic and polymeric materials. In plastic materials, the beam energy causes rapid surface vaporization, creating a sharp and highly visible etching effect. This characteristic makes CO₂ particularly suitable for marking acetate, TR90 and other plastics commonly used in frames.
A major advantage of the CO₂ laser is the speed of marking on thick plastics or extensive graphic layouts. However, the depth of penetration, if not controlled, can generate undesirable thermal deformation or color changes, especially on clear or translucent materials. In addition, CO₂ cannot be used on metals without prior surface treatments, limiting its use in mixed applications.
Another aspect to consider is the size of the laser spot. The CO₂, while effective over large areas, has a relatively large spot compared to the UV laser, which can be a limitation when small two-dimensional codes with high information density, such as the Datamatrix required for traceability according to international standards, need to be marked.
UV laser: principle of operation and application advantages
The UV laser, with a wavelength of 355 nm, acts through a mechanism known as photochemical ablation. The energy of the ultraviolet photon is high enough to break the molecular bonds of the material without generating significant residual heat. This process, termed “cold marking,” results in precise etchings with minimal heat affected zone (HAZ) and no deformation of the substrate.
In the context of eyewear, the UV laser is particularly advantageous in the marking of:
- Heat-sensitive plastics, such as polycarbonate or composite materials, where CO₂ would risk causing yellowing, micro-cracking, or loss of transparency.
- Ophthalmic lenses, where optical quality should not be compromised by thermal stress or microfractures.
- Clear or light-colored frames, on which the contrast obtained with the UV laser is generally superior, with no risk of surface burns.
- High-density two-dimensional codes, due to the very small laser spot (typically less than 20 µm) that allows marking of millimeter-sized Datamatrix with excellent readability according to the ISO/IEC 15415 standard.
An additional advantage of the UV laser concerns material versatility: in addition to plastics, the UV system is effective on glass, ceramics, and some coated metals, allowing a single technological solution for different stages of the production process.
Operational comparison: when to prefer one or the other technology
The choice between UV and CO₂ depends on a number of technical and production factors. If the goal is to quickly mark large logos on opaque acetate frames, the CO₂ laser is a proven and cost-effective solution. The process speed and low source cost make it suitable for high-volume production with simple graphic layouts.
In contrast, when working on delicate materials, transparent surfaces, or components requiring traceability with miniaturized two-dimensional codes, the UV laser becomes the obvious choice. The quality of marking, total absence of thermal stress, and the ability to work on mixed materials (technical plastics, glass, coated metals) more than compensate for the higher initial cost of the source and slightly longer cycle times.
A common mistake is to underestimate the importance of focus and working distance control. On curved frames or on lenses with complex geometries, the use of a three-axis scanning head or autofocus systems becomes essential to ensure repeatability of marking, regardless of the laser technology employed.
Online integration and practical considerations
In modern eyewear, laser marking is rarely a stand-alone process. Integration into automated assembly lines requires compact systems that can be interfaced with production management software (MES/ERP) and equipped with real-time quality control logic.
In this context, UV laser systems lend themselves better to integration with verification cameras for automatic grading of two-dimensional codes, a practice increasingly required by high-end manufacturers to ensure regulatory compliance and reduce waste. In contrast, CO₂ systems, while simpler to integrate mechanically, require more attention in managing the extraction of fumes generated by ablation, which may contain organic particulates and volatile compounds.
One aspect that is often overlooked is maintenance. State-of-the-art UV lasers (DPSS or solid-state) have a very high source lifetime (up to 25,000 operating hours) and require minimal routine maintenance. CO₂ lasers, while mature technologies, require periodic inspection of the condition of the laser tube and cooling system, elements that affect long-term operating costs.
Application examples and process parameters
To make the comparison more concrete, let us consider two real application cases. In marking an 8×3 mm logo on a matte-black TR90 frame, the CO₂ laser (power 30 W, focal length 160 mm) completes the process in about 1.5 seconds with a scanning speed of 800 mm/s, frequency 20 kHz, and power set to 70%. The result is a sharply visible white engraving without deformation.
In the same scenario, using a UV laser (power 5 W, focal length 160 mm), the time increases to about 2.8 seconds with speed 500 mm/s, frequency 25 kHz and power 85%. The contrast is slightly higher and the aesthetic effect “cleaner,” free of heat haloes, but the cycle is slower. The difference becomes even more pronounced when switching to a transparent polycarbonate frame: here the CO₂ tends to generate micro-cracks and opacity, while the UV laser keeps the transparency intact, with perfectly legible white marking.
In the case of marking a 3×3 mm Datamatrix on a CR-39 lens, the UV laser is the only technically feasible option. With optimized parameters (speed 600 mm/s, frequency 30 kHz, power 80%, defocus +2 mm), a grade A marking according to ISO/IEC 15415 is achieved, with high contrast and zero impact on the optical properties of the lens.
Decision criteria for choosing the system
The final decision between UV laser and CO₂ must take into account a few key elements. First, the material portfolio must be evaluated: if 80 percent of production involves opaque acetate and traditional technical plastics, CO₂ is a rational choice. If, on the other hand, you work mainly with polycarbonate, ophthalmic lenses, or transparent frames, UV laser becomes necessary.
Second, regulatory and quality requirements must be considered. If the end customer requires compliance with stringent traceability standards (as in the case of medical devices or products destined for regulated markets), the UV laser’s ability to generate very high resolution codes becomes a decisive competitive advantage.
Finally, it is necessary to think in terms of the complete process: integration with vision systems for quality control, the need to work on complex geometries, and the flexibility required to handle small batches of different products are all factors that can steer the choice toward one technology over the other.
