Todayâ€™s optical lenses are manufactured by a process called precision molding, whereby the glass is heated together with the forming die and then pressed into shape.
Researchers at the Fraunhofer Institute for Mechanics of Materials IWM in Freiburg, Germany have developed and refined another process, called hot embossing, whereby the glass is heated to a higher temperatures than for precision molding. The dies are heated too, but to a temperature some ten degrees lower than the glass â€“ enabling controlled heat exchange during the embossing process.
The new manufacturing technique of hot embossing is up to 10 times faster, a good 70 percent cheaper, yet still makes lenses of comparable quality.
â€œThe speed at which the lenses cool is crucial for their quality. If the glass is cooled too quickly, thermal stresses occur and the quality is diminished. If the glass cools too slowly â€“ because the die is too hotâ€“ the molding process takes too long, which pushes up the costs,â€ says Dr. Peter Manns, who leads the IWM research group.