1. What Is Focal Length?
In a laser cleaning machine, focal length determines how concentrated the laser energy is on the target surface.
A shorter focal length produces a smaller, more intense laser spot, while a longer focal length creates a larger, softer beam with lower energy density.
2. How Focal Length Influences Cleaning Performance
| Parameter | Short Focal Length (160–210mm) | Long Focal Length (254–420mm) |
| Energy Density | High | Low |
| Cleaning Strength | Powerful | Gentle |
| Spot Size | Small, precise | Large, wide coverage |
| Depth of Focus | Short, sensitive to distance | Long, more tolerant |
| Surface Safety | Higher risk of burn | Safe, low damage |
| Efficiency | Precise but slowerPrecise but slower | Fast and efficient |
In summary:
Short focal lengths are ideal for heavy rust, paint, and weld cleaning.
Long focal lengths are better for large surfaces, mold maintenance, and precision parts.
3. Application Recommendations by Focal Length
| Focal Length | Spot Size (Approx.) | Feature | Typical Application | Recommendation |
| 160mm | 0.1–0.2mm | Very concentrated | Heavy rust, welds, oxides | For precise, strong cleaning |
| 210mm | 0.2–0.3mm | Strong and versatile | Paint, oxides, molds | Standard for most handheld units |
| 254mm | 0.3–0.4mm | Balanced performance | Machinery, light rust, grease | Ideal for general maintenance |
| 330mm | 0.5–0.6mm | Wide and gentle | Large-area paint removal, aluminum | Best for large surfaces |
| 420mm | 0.7–0.8mm | Even energy, high tolerance | Curved or composite surfaces | Perfect for irregular surfaces |
4. How to Choose the Right Focal Length
1.High-power cleaning → Short focal length (160/210mm) Ideal for removing thick rust, welds, or old coatings.
2.Large-area cleaning → Long focal length (330/420mm) Suited for aluminum, composites, or aircraft structures.
3.Balanced cleaning → Medium focal length (254mm) Offers the best balance between power and safety.
5. Professional Recommendation
When configuring equipment for customers:
“We recommend a 210mm lens as the standard configuration.
For stronger cleaning, choose 160mm; for higher efficiency, 330mm or above.”
✅ Conclusion
Though often overlooked, focal length plays a decisive role in laser cleaning performance.
Choosing the right focal length ensures optimal efficiency, precision, and surface protection for every cleaning task.
