Thermofusion™ Technology outperforms traditional methods of lens curving
Thermofusion™ Technology sets Polaroid polarizing lenses apart from other lenses. Traditional methods of creating polarized lenses are vacuum-forming, injection moulding and casting. Here we compare the results with Polaroid’s lenses. Only Polaroid’s Thermofusion™ Technology offers true polarization and perfect optical performance.
Thermofusion™ Technology: perfect optical and polarization performance
Step 1 The flat PTX4000 material is placed between the highly polished concave and convex moulds.
Step 2 Carefully controlled heat and pressure are applied from above and below, creating a curved lens which is slightly tapered at the edges.
Step 3 The lens curve sets as it is subjected to rapid cooling. Once set it is then unloaded for mounting.
Thermofusion™ Technology allows us to produce lenses which are thicker at the centre and tapered towards the edges thereby optically ‘fine-tuning’ the lens while curving it. Wearers suffer none of the ‘warped vision’ provided by many inferior quality lenses and the subsequent risk of eye-strain is eliminated.
This technique also allows us greater flexibility in creating greater curvature in our lenses, so we can produce lenses for 2, 4, 6 and 8-base frames plus masks.
There are no compromises on production efficiency with Thermofusion™ Technology; we can produce 70 perfect polarized lenses per minute using this innovative method.
Vacuum-forming: reduced optical clarity
Step 1 Flat plastic lens sheet placed in concave base mould and sealed with a cover
Step 2 Heat is applied and air drawn out from below to curve the lens by vacuum
Step 3 The cover is removed and the lens removed for use – lenses cool at ambient temperature
This technique is popular with other manufacturers due to the relatively low costs involved. However unlike Polaroid’s Thermofusion™ Technology process, vacuum-forming allows no optical correction of the lens.Vacuum-formed lenses remain as thick at the edges as they are in the centre which results in optical distortion for the wearer. Though often this distortion is imperceptible, it puts constant strain on the eyes as they struggle to cope with warped shapes, sizes and distances presented to them.
Vacuum-formed lenses also do not retain the desired curve as well as press-polished lenses. The slow cooling off process allows the lens to ‘relax’ into a flatter position than desired
Vacuum forming can produce lenses with a fringe of warped vision.
Polaroid’s Thermofusion™ Technology technique creates optically perfect polarized lenses.
Injection moulding and casting: reduced polarizing efficiency
Step 1 Thin polarized film inserted into concave base mould. Convex lid seals down creating cavity
Step 2 Melted polycarbonate or polyamide (acrylic or polyurethane for casting) is injected, filling the cavity
Step 3 The mould is cooled and the curved lens removed
The inherent weakness with this technique is that when the polarized film lens comes into direct contact with hot plastic, its polarizing efficiency can be seriously depleted. So though the optical clarity of injection moulded lenses is usually good, their polarization quality is often compromised.
With Polaroid’s PTX4000 lenses, the polarizing filter is protected by 6 other layers of lens material and never comes into contact with the heat or pressure applied during the curving process. This preserves 100% of its polarizing capability.
Creating moulds for injection moulding can be expensive and this often inhibits the number and range of lens shapes and design varieties it is possible to produce. The rate of production is also relatively slow with injection moulding. Thermofusion™ Technology offers 70 lenses per minute.