Specialist optics manufacturers LBP Optics, alongside sister company ULO Optics, have supplied a set of Zinc Selenide lenses for a cutting-edge new measurement method for 3D shape acquisition. Devised by researchers at the Fraunhofer Institute for Applied Optics and Precision Engineering IOF, the Glass360Dgree sensor can scan objects three-dimensionally, regardless of whether they are made of transparent plastic or glass. This new method is suitable for quality control in production processes or for applications in automation.
At the heart of the system is a high-energy CO2 laser. Using special lenses for high power densities, the laser beam is expanded into a line that vertically illuminates the entire object. For a high-resolution measurement result, this line is moved over the object in a specially coordinated sequence. The energy of the laser light is partially absorbed by the measured object and converted into heat. The measurement object emits the heat distribution which is recorded by two MWIR cameras.
The Fraunhofer Institute development team approached supplier LBP Optics to produce the lenses. Five of the six ZnSe lenses were manufactured conventionally by ULO Optics, using an in-house designed cylindrical polishing machine. One of the lenses had a very steep cylindrical curve and therefore LBP Optics opted to produce it on their newly acquired laser-assisted diamond turning machine – one of only a handful of machines of its type worldwide. This particular lens was a challenging shape and gave LBP Optics a good opportunity to try out the capabilities of the new machine.
The main challenge for the LBP Optics engineers was to extend the machine running time from the pre-set standard of less than 2 hours, to enable one long cut over a period of around 8 hours. This involved some cross-Atlantic discussion and late-night remote programming of the machine’s computer. The size and steepness of the curve on the ZnSe piece was such that it needed to be machined very slowly to maintain the shape. It was finally completed after running continuously for around 8 hours.
The Fraunhofer team has now successfully demonstrated the new measurement system at the international trade fair for quality assurance “Control Virtual”, using the lenses supplied. The researchers are working intensively to make the measurement principle ready for the market. They already have some application areas in mind, explains Martin Landmann, a researcher in the Imaging and Sensing department at Fraunhofer IOF: “The parameters of our system allow us to optimize it for different application scenarios. If we reduce the resolution to below 50 µm, we can record a 3D data set in under a second and are thus fast enough for applications in robotics.”
The purchase of the new machining system significantly increases LBP Optics capacity for manufacturing diamond turned optics. The additional benefit of the laser assisted machining tool is that it allows the machining of a much wider range of materials than previously possible, such as fused silica and other glasses. With the appointment of a highly skilled and experienced diamond machining engineer to run the machine, LBP Optics can offer technical expertise in machining crystals and exotic materials including Stainless Steel, ZnSe, ZnS, Ge, CaF2, BaF2, Si and other glasses.
As LBP’s Paul Maclennan explains, “We’re really excited about this new machining system. At LBP Optics we have a strategy of progressive growth and this can only be fulfilled with the world’s best equipment, diamond turning engineers and technicians. This purchase is already enabling us to respond better to customer requirements, increase our production capacity, improve our technical capabilities and keep us at the forefront of our industry.”
The new laser-assisted technology also gives LBP Optics the ability to cut much larger pieces of Silicon and to manufacture symmetrical aspheres and non-symmetrical optics from glass materials. There are already several projects in production, including ZnSe hybrid lenses for sister company ULO Optics, polishing Silicon and making toric lenses.
