Out of the environmental lab and into the world
Photographers around the world love the reliability and high quality of the workmanship of ZEISS lenses. To guarantee this quality for all time, newly developed products are thoroughly examined in the laboratory. Andreas Pfeiffer, engineer and team leader in the environmental laboratory of Airbus DS Optronics GmbH in Oberkochen, talks about his work and explains in detail how ZEISS lenses are tested.
“We simulate different environmental influences on the products,” explains Andreas Pfeiffer. “Here in Oberkochen we mainly examine the consequences of the impact of temperature, humidity, bumps or vibrations. These so-called environmental simulations always happen under precisely defined laboratory conditions while maintaining certain testing norms. That makes the results reproducible and comparable.”
The foundation is the DIN EN ISO 17025 norm, which defines the general requirements the lab must fulfill. It defines the management system, the calibration of the devices and machines, as well as the qualifications of the specially trained personnel. Laboratories that work according to this norm receive an accreditation. In Germany the accreditation is granted by the DAkkS (the German Accreditation Authority), ensuring that the same standards are followed worldwide by all recognized testing centers of the same level.
“ZEISS’s requirements are clearly defined,” says Pfeiffer. “The lenses have to be durable and work in the most extreme conditions – regardless of whether it’s a rain forest, the desert or the Antarctic. And at the same time, the functions and imaging performance should be ensured over a long period of time.” In addition to functionality, purely optical aspects, such as discolorations or the rubbing off of labels, are also tested. And if a lens has different bayonet mounts, every single mount goes through the entire simulation procedure.
The DIN standard also stipulates exactly which test scenarios must be applied. “For optical devices there’s a range of norms in DIN that are used for the testing,” explains Pfeiffer. “The values that model different climate zones or certain mechanical stresses are all defined.”’ Using this information, one can simulate very closely the ‘real-life’ use of the lenses.
In conducting their simulation tests, the engineers in the environmental lab in Oberkochen have a large selection of devices and machines at their disposal. Vibrations are simulated using electro-dynamic ‘shakers’, different climate zones with temperature cabinets and humidity chambers. When asked whether the machines are custom-made, Pfeiffer answers, “There’s a lot that you can simply buy. Due to the norms for the testing procedure, manufacturers know exactly what to expect. So we just have to produce the matching adapters or holding fixtures for the test objects.”
For the vibration tests on the “shaker”, the lenses are exposed to broadband noises – a stochastically distributed signal with frequencies of 20 to 500 hertz – whereby effective stresses of up to 1.55G are produced. The lenses have to endure the procedure for 30 minutes along the three axes in space. For the shock tests, the lenses are tested for shock resistance with stresses of up to effectively 30 G, and in the vertical direction as much as 100G. “That’s more or less the stress of setting a lens down really hard on a table,” says Pfeiffer.
Photographers use ZEISS lenses around the globe, so the lenses also have to be able to deliver optimal performance in all kinds of climate conditions. “Humidity can cause the labels to rub off, or paint coatings to peel off or dissolve,” says Andreas Pfeiffer in describing possible types of damage. “So the test lens is exposed to a relative humidity of 82-93 percent for five consecutive days in a special humidity chamber.” For the temperature test, there are two scenarios: storage/transportation and operation. For the storage/transportation scenario, the lenses have to survive temperatures of -40°C to +70°C without any damage. While in operation the lenses have to withstand temperatures of -20°C to +55°C. For the operative tests, the testers take pictures of test charts. But the pictures are not analyzed by the testers – unlike with all the other parameters – but rather by the development laboratory at ZEISS Camera Lenses.
Of course, such comprehensive environmental simulations need time. Normally, it takes 10 to14 days, from receiving the test object to getting the final test report. “Only when there is nothing unusual and all tests have been passed is our job over and a pre-production batch of the lens can be manufactured,” says Pfeiffer. “If anything is wrong with the lens, ZEISS will create a new prototype and we test it all over again.” Thanks to this multi-step testing process, ZEISS ensures that its customers always receive lenses of the same high quality, guaranteeing them many years of enjoyment. Customers can always rely on ZEISS lenses to perform under the roughest conditions, even in the most remote corners of the globe.
Series: Around the World 3/3
About Andreas Pfeiffer
Andreas Pfeiffer studied optoelectronics in Aalen, Germany. He began his career at ZEISS in the semiconductor technology division, where he was responsible, among other things, for conducting radiation tests on optical components. In 2007 he joined the environmental lab of Carl Zeiss Optronics GmbH. After an acquisition in 2012, this division was renamed Cassidian Optronics GmbH, and then into Airbus DS Optronics GmbH in 2014.