In Conversation with Ernst Rothe

The excellent quality of the versatile, high-precision F-Theta-Ronar lenses from LINOS is a testament to decades of experience at both Rodenstock and LINOS. The 25-year history of these lenses is marked by immense customer satisfaction, and has established LINOS as a leader in laser technology.

Ernst Rothe of LINOS in Munich was instrumental in the success of the F-Theta-Ronar lenses. For 25 years he headed up research and development at Rodenstock and actively accompanied F-Theta-Ronar from the initial product idea to series production. As a pioneer in innovative handling of new products for the optics market, Ernst Rothe played a major role in making Rodenstock, and today LINOS as well, global players in the optics field. LINOS is now a high-end component supplier for the laser industry covering a wide variety of applications. For more details, read the following interview with Ernst Rothe, retired head of research and development, and Christian Schaarschmidt, Market Segment Manager of Laser Material Processing at LINOS.

What makes the F-Theta-Ronar lens from LINOS so special?

Ernst Rothe: The printing industry was the first to exploit the powerful new light source provided by lasers. Together with the ever-increasing processing power of computers, the new technology simplified the printing process considerably. Rodenstock, already an established optics company, was contacted by one of the major printing machine manufacturers seeking an innovative solution for digital imaging of printing plates. We came up with the idea of using polygon mirrors, which deflect the laser beam at high speed, to move the laser point over a planar surface. These were later replaced by galvanometer mirrors. Following a further 2 to 3 years of development, we were one of the first companies to manufacture a high-precision, process-oriented focusing system: the F-Theta-Ronar lens.

What new applications were made possible by this technology?

Christian Schaarschmidt: Laser imaging and laser material processing technology were advanced significantly when LINOS developed their new optics and beam guidance systems. The range of products from Rodenstock traditionally served the high-precision and high-end sector. Today, F-Theta-Ronar lenses from LINOS meet the most stringent demands in the areas of precision laser marking, laser soldering, microscopic welding and drilling of printed circuit boards. In the printing sector, press cylinders are now directly laser-imaged using F-Theta-Ronar systems. We also see great potential for these high-performance optics in virtually all aspects of solar cell production.

What characteristics make F-Theta-Ronar so versatile?

Christian Schaarschmidt: Our F-Theta-Ronar lenses permit extremely small focus diameters, are practically distortion-free, and are ideal for large beam diameters and scanning angles. Thus they are well suited for very small, highly precise structures, right down to the micrometer range.

Mr. Rothe, one example of LINOS's expertise in optics manufacturing is the optical design program developed in your department. What are the distinguishing features of this software?

Ernst Rothe: In the past, a finished lens system was almost sacred because the beam calculations it involved were so arduous. Our primary goal was to reduce the computation time while optimizing quality in production. Next, we worked on refining the program both by extending the software parameters to include more conditions and by exploiting increased computer performance, until analyses and corrective calculations in the micro-range were possible. Furthermore, special algorithms were integrated for the F-Theta condition, to calculate F-Theta-Ronar lenses.

One of the unique features of LINOS software is its integrated tolerance analysis. What advantages does this offer?

Ernst Rothe:

Our in-house simulation programs let us accurately pre-calculate the consequences of various manufacturing tolerances for series production. This considerably reduces the time to production start-up. Rodenstock/LINOS manufacture their own lenses and mechanics, and these LINOS-specific production techniques are thoroughly integrated into the tolerance analysis. I have always advocated the "luxury" of in-house development, as this is the best way to optimize our production capabilities and maintain and develop our level of expertise. It also enables us to react instantly to problems or new orders.

How does LINOS maintain the exceptional high quality of F-Theta-Ronar lenses?

Christian Schaarschmidt: LINOS has developed a number of its own quality-testing procedures, such as the tilting-angle measurement in the mounted lens, which is used, for example, in developing new lenses. Our state-of-the-art production facility in Regen has a specially developed testing station for the F-Theta-Ronar, where we can mark azimuths and create customer-specific protocols. Thanks to the creativity of our engineers, physicists and qualified staff, we know that our processes – coupled with the continual refinement of our design software – guarantee extremely reliable and precise series production.

How have the latest developments in laser technology affected F-Theta-Ronar lenses?

Christian Schaarschmidt: We have a very wide range of products and can meet the ever-growing number of specific customer requirements; for example, with regard to laser parameters, focal lengths and scan fields. These capabilities are enhanced by sophisticated coating designs developed at LINOS, the selection of the right glass materials, and geometric calculations. Our department maintains close customer contact and is very quick to take up new ideas, helping to ensure that we remain the technological leader into the future.

Thank you both very much for your time!

Interview: Christine Costa