The ultrasonic cleaning of zinc selenide lenses is mainly due to the following three reasons:

1. Fragile material: Zinc selenide is soft and brittle, prone to scratches and high temperatures, and cannot be wiped by hand.

2. High cleanliness requirements: Before coating, sub-micron contaminants must be removed, which cannot be cleaned by hand.

3. Suitable for ultrasonic cleaning: It relies on the cavitation effect to non-contactally remove dirt, without touching the lens, and can also clean the edges and crevices.

For the cleaning of zinc selenide lenses, the official ultrasonic cleaning machine model recommended by VGT is VGT-1509FH. This equipment is clearly labeled in VGT's product line as "Ultrasonic Cleaning Machine for Zinc Selenide Window Lenses" and "Ultrasonic Cleaning Machine for Elliptical Zinc Selenide Polished Sheets", indicating that it has been specifically tuned to handle the physical properties of zinc selenide, such as being "soft, brittle, and sensitive to high temperatures".

The core feature of this model lies in its controllable parameters and complete process. The ultrasonic frequency can be adjusted between 40kHz and 120kHz. The low frequency is used to remove stubborn oil stains such as polishing paste and cooling oil, while the high frequency is responsible for removing sub-micron particles. The power can be adjusted within the range of 50W to 300W to prevent excessive energy from damaging the lenses or coatings. The temperature control system limits the cleaning solution temperature to ≤50℃ to avoid damage to zinc selenide due to thermal stress. The equipment integrates 15 functional slots, covering complete processes such as ultrasonic cleaning, multi-stage rinsing, slow drying, and IPA steam drying, reducing the risk of secondary contamination after cleaning.

The VGT-1509FH ultrasonic cleaning machine from WIGUITE is specifically designed for cleaning optical components. It has unique technical advantages in cleaning zinc selenide lenses. Taking all of this into account, it can be broken down as follows:

1. Ultrasonic generator system: Adjustable frequency and controllable power, reducing the risk of ZnSe cavitation damage.

Equipped with the fourth-generation WIGUITE microcontroller to control the ultrasonic generator, with a frequency range of 40 to 120 kHz that can be adjusted: for cleaning ZnSe, the preferred frequency is 80-120 kHz, resulting in smaller cavitation bubbles and softer impact, specifically for removing polishing powder, sub-micron particles, and fingerprint oil stains; at low frequency of 40 kHz, it is only used for stubborn contaminants, which can be switched according to the thickness of the lens and the coating condition, avoiding the problem of ZnSe surface micro-cracking and membrane damage caused by strong cavitation.

The ultrasonic output intensity is visualized, and the cleaning time is independently set. The power can be finely matched, and there will be no problem of energy overload in ordinary single-frequency ultrasonic machines, which can cause the ZnSe anti-reflection film to be broken through. 

The matching workpiece oscillation mechanism (adjustable from 3 to 10 times per minute): the lens basket moves slowly up and down in a reciprocating motion, eliminating the dead zones of ultrasonic standing waves, and at the same time allowing the lens and the cleaning liquid to continuously exchange, avoiding particles getting stuck on the lens surface and causing secondary scratches; it can also prevent lens stacking collisions.

II. Multi-slot complete process chain, suitable for ZnSe chemical sensitivity

The entire machine has 15 functional slots that can be combined: organic solvent pre-washing → neutral water-based cleaning → multi-stage overflow pure water rinsing → slow pulling dehydration → hot air drying. Segmented chemical environment control is adopted to address the pain points of ZnSe's intolerance to strong alkalis and its susceptibility to corrosion by residual chemicals.

1. The entire process can be carried out using neutral optical cleaning agent and high-purity water, avoiding strong acids and alkalis, to prevent corrosion of the ZnSe substrate and erosion of the film layer.

2. Multi-level overflow rinsing tanks, combined with a circulating precision filtration system (adjustable from 1 to 50 μm), continuously filter out the polishing powder and solid particles that are stripped from the cleaning solution, preventing the particles from causing friction and scratching the soft ZnSe surface under ultrasonic action; pressure monitoring and alarm for the filter, automatic prompt for filter blockage, ensuring the cleanliness of the cleaning solution.

3. Slow pulling dehydration + hot air drying: Solves ZnSe water stains and water marks defects (key before coating).

Once water marks remain on the surface of ZnSe, permanent fogging will occur after coating, affecting the infrared transmittance.

Slow pull-up dehydration: The workpiece is slowly pulled out from the high-purity water surface at a low speed, using surface tension to allow the water film to uniformly detach from the lens, minimizing water droplet residues.

Independent hot air drying chamber, clean hot air drying, combined with clean air path, the drying process does not introduce dust.

Compared with ordinary single-chamber ultrasonic cleaning: After single-chamber cleaning and removal, it is very easy to dry and leave water marks, which is a fatal defect for the pre-coating process of infrared ZnSe lenses. The VGT-1509FH ultrasonic cleaning machine of Weiguit designed this continuous process for the cleaning needs of optical components before coating.

III. Non-contact Cleaning, Reducing Scratches Caused by Manual Wiping

ZnSe has low hardness. Traditional cotton swabs and dust-free cloths, even with hard micro-particles, will directly scratch the optical surface during wiping. Ultrasound relies on the cavitation effect of the liquid to non-contactally remove contaminants and does not cause mechanical friction with the lens surface, protecting the substrate and the infrared coating. The lens is only clamped by the edge workpiece, and the optical working surface is completely not in contact with the solid wiping medium.

IV. Automation, Process Consistency, Stable Batch Production Yield

The entire system is fully automated. All parameters such as cleaning time, oscillation speed, temperature, and ultrasonic power are fixed. The cleaning effect is highly consistent across batches.

· It can achieve standardized cleaning of lenses before coating in batches, eliminating differences caused by manual operations;

· The tank body is made of 316 stainless steel, which is resistant to corrosion by optical solvents and does not easily release metal ions to contaminate the optical surface;

· It is equipped with an overflow and oil-water separation system, which prolongs the lifespan of the cleaning solution, continuously maintains the cleanliness of the solution, and reduces the probability of secondary pollution.

V. Adaptation to Infrared Optical Pollutants

Common contaminants on ZnSe lenses: polished residual ZnSe particles, cutting oil, fingerprint grease, environmental dust. High-frequency cavitation can penetrate into the edge, chamfer, clamping step and other blind areas that are difficult to clean manually, achieving full surface cleaning; after cleaning, it meets the cleanliness requirements before infrared coating, reducing coating pinholes, peeling and scattering losses.

Based on the above technical advantages, it can effectively reduce the defect rate of lens cleaning, ensuring the optical performance of the product.