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简体中文Can cleaning lasers be used through glass?
The short answer is: It depends entirely on the type of cleaning laser and the type of glass, but it is generally ineffective and often dangerous.
For true industrial laser cleaning, the answer is almost always no, you cannot effectively use them through glass. Here’s a detailed breakdown of why.
1. The Primary Problem: Absorption of Laser Energy
Industrial cleaning lasers (typically pulsed fiber lasers) work by delivering intense, short bursts of energy to a surface. This energy is absorbed by the contaminant (rust, paint, oxide layer) but (ideally) reflected by the underlying substrate. The rapid absorption causes the contaminant to vibrate, ablate, or vaporize off the surface.
Glass is transparent to visible light, but it is a strong absorber of specific infrared wavelengths.
Common Cleaning Lasers: Most industrial laser cleaners operate in the 1 micron wavelength range (e.g., 1064 nm). Standard soda-lime glass (window glass, picture frame glass) absorbs a significant amount of energy at this wavelength.
What Happens: When you fire a powerful cleaning laser through the glass, the energy doesn't pass through efficiently. Instead, it gets absorbed by the glass itself.
2. The Consequences of Trying
If you attempt to use a standard industrial cleaning laser through a pane of glass, several bad things will happen:
Damage to the Glass: The absorbed laser energy will heat the glass extremely rapidly at the point of impact. This creates intense thermal stress, almost certainly causing the glass to crack, shatter, or melt.
Safety Hazard: Shattering glass is an immediate projectile hazard. The laser beam could also reflect unpredictably off the broken surfaces.
Ineffective Cleaning: The little energy that might make it through the glass would be scattered and weakened, making it completely useless for cleaning the target surface on the other side.
Damage to the Laser System: Back-reflections from the glass surface can be directed back into the laser's delivery system, potentially damaging the sensitive optics.
Are There Any Exceptions?
Yes, but they are very specific and not what you'd typically have on hand.
Specialized Infrared Glass: There are types of glass, like Fused Silica or Calcium Fluoride (CaF2), that have high transmission rates at common laser wavelengths. These are expensive, specialty materials used for laser system optics themselves, not as a protective window for cleaning.
Different Laser Wavelengths: If you had a laser that operated at a wavelength where standard glass is perfectly transparent (e.g., in the visible spectrum), and the contaminant you're trying to remove absorbed that wavelength, it could work in theory. However, this is not the standard use case for laser cleaning. The laser would still need to be powerful enough to ablate the material, which introduces other risks.
What About "Laser" Glass Cleaners?
This is where confusion often arises. You can buy devices called "laser glass cleaners" for cleaning the glass itself on buildings or in solar farms.
How They Work: These systems use a lower-power, continuous-wave laser (often CO2 lasers at 10.6 µm) or other wavelengths. The laser is scanned across the glass surface. The beam is not passing through the glass to clean something else. It is directly interacting with the contaminants (dust, soot) on the glass surface, causing them to be blown away by thermal or photo-acoustic effects.
The Glass as a Substrate: In this case, the glass is the substrate being cleaned, not a window the laser is fired through. The laser parameters are carefully chosen so as not to damage the glass substrate while effectively removing the surface dirt.
The Practical Workaround
If you need to protect a laser cleaning head or contain a process, the standard solution is not to shoot through a window, but to integrate the laser into the sealed environment. The laser head itself is placed inside the chamber, and the process is observed through a viewport made of a material that is safe for the specific laser wavelength being used.
