How to Avoid Secondary Contamination of Lens in Scanning Galvo Mirror?

In general power output lasers, all laser galvo mirrors and lenses will absorb specific laser wavelengths due to manufacturing processes or external pollution, etc. Over time, this shortens their lifespan and can cause them to break, resulting in the machine being affected and even shut down.

The increased absorption of laser wavelength by laser lens can cause uneven heating which leads to reflection of the lens

The change in refractive index causes non-uniform power distribution when laser passes through or reflects from a high-absorption lens, resulting in high temperature at the center and low temperature at the edges of the lens. This phenomenon is known as thermal lensing in optics.

Thermal lensing caused by high absorption of laser lens due to contamination can lead to many problems. It can cause irreversible thermal stress in the lens substrate, power loss when the beam passes through the lens, deviation of the focal point position, premature damage to the coating layer, and eventually damage to the lens. When cleaning lenses exposed to air, we often neglect the cleaning requirements and precautions, using improper materials, which can cause new contamination and even scratch the lens, resulting in irreversible damage.

Cleaning of the laser lens is very important

Maintaining the clean optical lens is the most important thing, and good cleaning habits should be used to carefully clean the lenses, reduce or eliminate pollution caused by human factors such as fingerprints or saliva. When operating the optical system with your hands, wearing finger cots or medical gloves during cleaning, disassembly, and installation should be done.

The requirements and precautions for cleaning laser lenses should always be followed, and only designated materials such as optical wiping paper, cotton swab reagent grade ethanol, etc. should be used during the cleaning process. Taking shortcuts when cleaning, disassembling, or installing any lens will shorten its lifespan or even cause permanent damage.

After determining that a lens is contaminated, it is best to use an otoscope to blow the lens until there are no particles on the surface. Do not blow it with your mouth because the exhaled air usually contains oil and water that will further contaminate the lens. If there is still dirt on the surface after using the otoscope, a dedicated cotton swab dipped in a mixture of acetone and ether can be used to gently wipe it away. The contamination of lenses in lasers can seriously affect laser output power and even cause serious errors in data acquisition systems. If we can keep the lenses clean, it will undoubtedly extend the service life of the machine.