Anybody involved in the manufacture or use of high quality optics knows how important cleanliness is throughout the entire process. Even the smallest amount of soil, including water spotting, can cause tiny irregularities on the surface of the lens. These irregularities are more than just unsightly, they can effect how the lens performs and even prevent the proper adhesion of thin film coating, resulting in poor performance of the finished piece.

Common soils such as grinding coolant, lacquers, mounting pitch, stacking wax, cerium oxide residue, and even simple dust and fingerprints can all find their way onto a lens during the manufacturing process. As a result, an extremely thorough method of cleaning must be implemented during the manufacturing process, and periodically with regular use, that removes these types of soils both quickly and completely. Ultrasonic cleaning, when used in conjunction with the proper cleaning concentrate, is an excellent way to achieve this.

Ultrasonic cleaners take advantage of a phenomenon known as cavitation, which creates an extremely strong scrubbing action on all surfaces of an object at a microscopic level. This process coupled with an aqueous cleaning solution, such as Branson Ultrasonic’s OC Optical Cleaner, results in an unparalleled level of precision cleaning.

Cleaning Optics with Ultrasonics: Step by Step

Choose Your Cleaner

-The first step in the process is to choose the correct ultrasonic bath for the job. This can be done  by asking two important questions: “How big are my parts?”, and “How many parts do I want to clean at once?”. The answer to both these questions will determine the size of the ultasonic tank you will need for the job. It is recommended however that you do not over-fill the tank with parts, as they may rub together during the cleaning process. A heated tank is also recommended for removing most soils, set to a temperature around 180 degrees Fahrenheit.

Cleaning Your Optics

Next, fill the tank with a fresh batch of clean water and your chosen cleaning concentrate. After filling, it’s recommended that the tank be run “empty” for a cycle, or the units de-gas function be used before cleaning. This will remove any trapped gas that may be in the solution that will otherwise rob the unit of cleaning power.

Once the tnk is filled an de-gassed, place the parts in a cleaning basket in such a way that they will remain stationary and not rub against other parts in the basket, if any. Run your ultrasonic cleaner for a full cycle, and check to see if the parts meet cleanliness standards. Extremely dirty parts may require more than one cycle to fully clean.

Post Wash Rinsing

After the cleaning cycle is complete, rinse your optics with a hot water spray rinse at about 150 degrees Fahrenheit with de-ionized water. It is also recommended that the rinse water be ran through a micron filter to ensure that there are no contaminants being re-deposited on parts.
Drying Processed Optics

Once cleaned and thoroughly rinsed, a “slow pull” drying method is recommended. Some optics however will require a forced hot air recirculating dryer. If this method is used, a HEPA filter must be installed to prevent new soils from being deposited on parts.

Benefits of Using Ultrasonic Cleaning on Optics

Beyond the obvious benefits of utilizing a cleaning method that cleans at a microscopic level, there are other advantages to consider when contemplating switching to ultrasonics. These benefits include:

• Ultrasonics produce a superior level of clean than using solvent based methods, and are much safer for both workers and the environment
• There’s no need to change laquer, wax, or pitch specifications prior to cleaning.
• Cleaning solutions, when used in conjuction with a filtration system, can be used multiple times before needing to be discarded.

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