Spectral reflectance is used on ophthalmic lenses to measure anti-reflection (AR) spectra and residual color, as well as hardcoat and hydrophobic film thickness measurement.
AR coatings are applied to reduce glare and the resulting eye fatigue caused by uncoated lenses. The blue-green hue of AR-coated lenses has also turned out to be an attractive feature for many consumers. Therefore measurement and control of the AR coating and its color has become increasingly important.
The Filmetrics F10-ARc was designed especially for ophthalmic applications and comes standard with a number of proprietary features for characterizing AR coatings.
Hardcoats are applied to impart increased scratch and UV resistance. This protection is supplied to the lens by covering it with the hardcoat and to the AR coating by providing a harder, less flexible foundation.
The Filmetrics F10-ARc is available with a hardcoat measurement upgrade. It is possible to measure both one- and two-layer hardcoats up to 15 microns thick.
Hydrophobic coatings impart water- and oil-repellent properties to AR-coated lenses, making them easier to clean. These layers are extremely thin - on the order of a hundred atoms - and thus require short-wavelength (UV) light to measure most accurately. The preferred instrument for measuring hydrophobic layer thickness is the F10-AR-UV with the UPG-RT-to-Thickness and UPG-Thickness-to-n&k upgrades.
An optional stage (SS-Trans-Curved) for the F10-AR is available for measuring lens transmittance.
For ophthalmic applications, contact our thin-film experts.
Filmetrics offers free trial measurements - results are typically available in 1-2 days.
Reflectance data was collected using our F10-ARc system with optional HC upgrade which allows hardcoat thickness measurement. This instrument uses an optical contact probe which inherently reduces the effect of backside reflections and allows for measurement on concave and convex surfaces.
The contact probe is placed on the surface of the lens. The spectral data is collected and then automatically analyzed by FILMeasure to determine if the lens meets the designated reflectance specifications. It is possible to measure average reflectance, local minima and maxima, and compensate for the presence of a hardcoat. This particular lens conformed to requirements and a clear “Good” indication is displayed to the system operator.