Turning High Index Lenses into Sunglasses
High index lenses have notable advantages over traditional plastic or glass lenses. The 1Z0-301 exams material used in them allows for a higher index of refraction, so light will reach the eye faster than it would with standard plastic or glass lenses. High index lenses are available in plastic or glass form to accommodate a wide range of prescriptions. They are also denser than their standard counterparts, meaning less material can be used to achieve the same degree of visual correction. Less material equals less weight – a very practical benefit indeed when it comes to eye-wear. 1Z0-311 exams Because of these advantages, high index lenses are a popular alternative; not just for regular vision correction eyeglasses, but also for sunglasses.
They can be ordered in a photochromic version to automatically adjust to sunlight, or can be tinted in various popular shades and colors, such as brown, gray, or green. Some prescriptions are also available in a high index polarized format. So how are high index lenses tinted? As with standard plastic or glass lenses, the exact process depends on the type of material used. Plastic lenses – of either the standard or high index variety – are colored in much the same way as you would color an Easter egg. A chemical bath is created in the appropriate color and the lens is suspended in it. This kind of tinting is a retroactive process: first the plastic lens is created to the specification of your prescription, in a clear version, just as you would order for standard prescription glasses. Once crafted the lenses then receive their chemical bath and absorb the tint. Tinting or coloring glass lenses is a completely different matter. Glass cannot be chemically dyed as it will not absorb color after it is formed. Colorization is available for both standard glass lenses and high index glass lenses, but each format requires a different process. For standard glass, the tint is added as the glass is produced. The manufacturer adds minerals that change the color as the glass is being melted and formed. Later the lenses are ground into the appropriate prescriptions.
Because of its unique properties, high index glass cannot be created in various colors and at the time of formation. The only way to color high index glass is to vacuum-coat the color directly onto the surface of the glass. Sometimes that coating can be thick, and cannot be offered in all the color varieties open to plastic or standard glass, but the option is available. In this instance, the prescription is first ground out of previously-made high index glass and later coated with the desired color.