Anti reflection coatings for modern glasses really began to take off in the early 1960’s, although perhaps “take off” is an unfortunate choice of expression when talking about coatings which are supposed to stay on.  The early products were, of course, only available on glass (glasses) lenses, but then nearly all glasses lenses were glass anyway – which seems a little redundant I know. A leading British lens manufacturer was once asked at an optical society meeting if AR coatings for spectacles were available on plastic lenses and he replied  “No it will never be possible to put them on plastic lenses”.  He quickly added that it is perhaps foolish to make negative predictions.  In this case foolish indeed when one considers the excellent quality of the plastic coated lenses readily available for glasses today!  

 

One of the most successful early products was the Zeiss T-coated Punktal lens, which had a deep purplish-blue residual reflection, not much like the present day lenses.  Other coatings on the market did not quite match the good appearance of the Zeiss, presenting a slightly lighter reflection.  The colour of the reflection depended on the thickness  of the coating and it was possible to produce a straw coloured  reflection, which some considered better for high plus prescriptions.

 

When Multi-AR (mult aniti-reflective) coatings became available, the difference was dramatic.  The reflections came off in very dark green colour, quite like the MAR coatings of today.

 

Soon plastic lenses were available, MAR coated and of a quality equal to that of glass lenses, although in some early ones the material of the lens tended to be slightly discoloured by the process.  This problem obviously has been overcome and it is probably true to say that today’s lenses are of a quality impossible to fault. 

 

Nowadays, it is usual to combine the MAR with a hard and also a water repellant coating and we now have the Perfect Lens.  It will not be possible to add any further improvements (another foolish negative prediction).

 

The benefits of MAR coatings to the wearer, particularly the myopic person are immense.  The improvement in appearance can be dramatic.  There is a slight increase in the transmission of light -  but the difference this makes to vision is a little difficult to assess and certainly hardly noticeable. 

 

Regrettably, false  and misleading claims are sometimes made for coated lenses, notably that they are very advantageous for night driving.  This is true in that (as mentioned above) they increase the transmissability of the lenses,  but unfortunately this, almost insignificant, factor is sometimes credited with a greater value than it deserves.   “Anti reflection” is frequently confused with “Anti Glare” and can lead to claims that oncoming headlight glare is reduced by the addition of an AR coating to the lenses.  It is not.

 

However, let us not forget the raison d’etre for AR coatings, viz, to reduce the reflections from one’s lenses, thereby enabling the onlooker to observe, unhindered by nasty reflections, the true beauty of the eyes; the fathomless pools of emotion, the er……………”Excuse me, onlooker, what do you think of…………………………….”    

Tags: Buying Glasses Online, Mar, prescription spectacles

This entry was posted on Sunday, April 5th, 2009 at 7:26 pm and is filed under Lenses. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.