Mirror Coatings for Lenses

Mirror coatings were derived as a functional reflective coating to help redirect sunlight from the surface of lenses. Since its introduction many derivations of mirror coatings have been produced creating a wide range of colored mirror coatings and functional purpose. Different applications have also been introduced creating a multifunctional purpose and a cosmetic market for mirror coatings with flash mirror coatings. Below you will find descriptions of the composition, maintenance, types, and correlation of mirror coatings with tins and polarized lenses.

COMPOSITION OF MIRROR COATINGS

  • Mirror coatings can be applied to almost any lens materials surface, and are most commonly applied to the outer surface of the lens.
  • Mirror coatings are applied to lenses by a vacuum application of interference layers made of powdered oxides, metals, lacquered plastics or other available compounds.
  • Mirror coatings are composed of constructive interference layers that interfere with light passing through the lens by reflecting light. The denser the interference layers the more reflection is induced, creating a mirror effect.

MAINTAINING MIRROR COATINGS

  • Most Anti-Reflective coatings consist of at least one if not a combination of the following: Magnesium Fluoride (MgF2) (Mainly used on glass), Silicone Oxide (SiO2), Titanium Oxide, Zirconium Oxides, and with technological advances other oxides and chemical that are not listed may be used
  • A/R is a microscopic thin but extremely hard layer applied to the surface of the lens through a vacuum coating technology.

Cause of reflections

  • Mirror coatings should be cleaned with specially formulated lens cleaners. Other commonly used home made solution include:
    • A mild soap (no higher than PH 7.5) diluted in water.
    • 70% isopropyl alcohol diluted in water (no more than 50/50 mix if used on a regular basis)
  • Stay away from strong detergent soaps and strong acidic or base solutions (PH's ranging around 10) including any ammonia based solutions like Windex or other industrial cleaners.

TYPES OF LENS COATINGS AND PURPOSE:

  • Mirror coatings can be applied as a solid, gradient and double gradient coating. Some common mirror coatings include the 'Half Mirror' and 'Flash mirror'. The half Mirror Coating is a dense mirror coating that gives a full mirror reflection on the outer surface of the lens. This coating completely shields the appearance of the eye. The flash mirror coating is a less dense coating that offers a transparent mirror effect.
  • Mirror coatings are used for functional and aesthetic reasons. Functionally the double gradient mirror coating is used to reflect light from above and light reflected from the ground while allowing more light to pass through the center. The combination of a double gradient mirror coating and moderately dark solid tint and/or polarized lens delivers optimal direct visual acuity on sunny days with snow or other glare enhancing matter on the ground.

LENS TINTS & POLARIZATION WITH COATINGS:

  • Underlying tints are usually applied prior to applying mirror coatings. These underlying tints serve as a background enhancing the mirror effect and also visual acuity if well proportioned. However, because some coatings like the 'half-silver' mirror coatings reflect a good portion of light away, the darker the tint on the lens the less light is reaching the eye. Considering that light is one of the main ingredients to vision, a darker tint may result in too much loss of light, which can affect visual acuity.
  • For the most reduction of glare a polarized lens with a mirror coating is recommended.