A Lens's Grand Journey: Anti-Glare Coat

Ever wondered how anti glare coatings work? Or how the coating is applied to a lens in the lab?

Greeting dear readers! At TLG we often say that “An anti glare coating is the single best upgrade available for purchase.” We see it as such an essential lens enhancement that we recommend it to almost every customer. An anti-glare coating, also known as an anti-reflective (AR) coating, is a thin layer of material applied to the surface of a lens or other optical element to reduce reflections and glare. The primary purpose of this coating is to improve the clarity, contrast, and overall quality of the optical system, whether it's eyeglasses, camera lenses, computer screens, or other surfaces. Our lab Laramy-K Optical has been manufacturing lenses with high quality Antiglare coatings for 20 years! Here's how an anti-glare coating works:

Interference Principle: The anti-glare coating works based on the principle of interference. When light passes from one medium to another (e.g., air to glass), some of the light reflects off the surface of the material due to the difference in refractive indices. This reflection creates glare and reduces the amount of light that reaches your eyes, resulting in decreased visibility and contrast.
Multiple Thin Layers: An anti-glare coating consists of multiple thin layers of a transparent material with varying refractive indices. These layers are usually made of metal oxides or other compounds. By carefully designing and depositing these layers onto the surface, the coating creates constructive interference for certain wavelengths of light. This means that the reflections from each layer will cancel each other out, leading to a significant reduction in overall reflection.
Reduced Reflection: When light encounters the anti-glare coating, some of it is reflected off the outermost layer of the coating. However, as this reflected light passes through the various layers of the coating, the constructive and destructive interference processes occur, causing the reflected light waves to interfere with each other in a way that reduces their intensity. This results in less light being reflected back to your eyes, which in turn reduces glare and allows more light to pass through the lens or surface.
Improved Clarity and Contrast: By minimizing reflections, the anti-glare coating enhances the clarity of the optical element. This is particularly important for eyeglasses, camera lenses, and screens, where unwanted reflections can reduce visibility and cause visual discomfort. With reduced glare, you can experience better contrast and color accuracy, making it easier to see fine details in your surroundings or on a screen.
Cleaning and Durability: Modern anti-glare coatings are designed to be resistant to scratching and easy to clean. They often include hydrophobic and oleophobic properties, which repel water and oil, preventing smudges and fingerprints. This makes maintenance and cleaning of coated surfaces more convenient.

In short: An anti-glare coating reduces reflections and glare by using the principle of interference to cancel out reflected light waves. This results in improved visibility, contrast, and overall optical performance for various applications, from eyewear to electronic displays. How then is this applied to the lens surface and why does it take days in the lab?

Applying an anti-glare coating to a lens involves a specialized process that typically takes place in a controlled environment, such as a vacuum chamber, to ensure the proper adhesion and quality of the coating. The steps involved in applying an anti-glare coating to a lens are as follows:

Cleaning and Preparation: Before applying the coating, the lens surface needs to be thoroughly cleaned to remove any dust, oils, or contaminants that could interfere with the adhesion of the coating. This is usually done through processes like ultrasonic cleaning and solvent rinsing.
Deposition of Thin Layers: The anti-glare coating is created through a process called physical vapor deposition (PVD) or electron beam evaporation. In this process, the lens is placed inside a vacuum chamber, and a material with the desired refractive index is heated until it evaporates. The evaporated material then condenses onto the lens surface, creating a thin layer.
Multiple Layer Deposition: To achieve the desired interference effect and reduce glare effectively, multiple thin layers of different materials with varying refractive indices are deposited on the lens. Each layer is carefully controlled in terms of thickness and composition to create the desired optical properties.
Monitoring and Control: Throughout the deposition process, the thickness of each layer is monitored using methods like quartz crystal microbalances or optical monitoring. This ensures that the coating adheres to the desired specifications.
Heat Treatment: After the layers are deposited, the lens may undergo a heat treatment process to improve the durability and adhesion of the coating. This step helps to reduce the chances of the coating peeling or delaminating over time.
Quality Control: Once the coating is applied, the lens undergoes quality control checks to ensure that it meets the desired optical and cosmetic standards. These checks may include visual inspection, measuring light transmission and reflection, and verifying the coating's uniformity. Other quality control checks done by our lab Laramy-K optical include razor scoring, salt boiling, tape pull, cold shock, and microscopic inspection.
Additional Coating Layers: Depending on the application, additional coatings may be applied over the anti-glare coating. For example, a lens might have a hydrophobic layer to repel water and oils.
Final Inspection and Packaging: Once the coating and any additional layers are applied and inspected, the lens is cleaned again and carefully packaged to prevent any damage during shipping or handling.

When lenses are ordered with an anti glare coating an extra 48 hour journey is commenced through clean rooms and meticulous inspections. A final inspection checking for cosmetic aberrations is done during lens cutting in house at TLG all to ensure your lenses are perfectly coated and ready to enhance your vision.