Efficient characterization of assembled IR lenses for all opto-mechanical parameters
Increasing demands in imaging quality of all assembled optical systems require the optimization of lateral and axial alignment of individual lenses. An economic possibility to improve mechanical alignment is the step-by-step centration testing of the topmost lens surface during the assembly process. Regardless of the material properties of the lens, measurement equipment that operates in the visible spectral range is suitable for this application. When the assembled lens does not meet the expected imaging performance, an in-depth analysis is needed. Focusing electronic autocollimators in combination with high-precision air bearing spindles are commonly used to analyze the centration of each optical surface and lens element. The well-established TRIOPTICS OptiCentric family allows to determine the centration of inner surfaces using their powerful MultiLens technique. The obtained measurement data are processed to provide the shift and tilt of individual lenses or groups of lenses with respect to each other or a freely selectable datum. For IR lenses a wavelength that can penetrate the lens material is required. Autocollimators for MWIR or LWIR are to be combined with a VIS measurement head for all measurements on lens surfaces that are directly accessible from the outside. A measurement accuracy of 0.1μm is reached. The development of the new OptiCentric® IR autocollimation head, was mainly driven by optimizing the spot size and hence its accuracy. A centration measurement precision of below 0.25 micrometer for MWIR and LWIR wavelengths was obtained. For measurement of air spacings and center thicknesses through all IR lens materials the instrument incorporates a low coherence interferometer with an accuracy down to 0.15µm. The contribution describes how an IR lens assembly consisting of several lenses can be fully opto-mechanically characterized in a non-contact and non-destructive fashion. Optimized processes to effectively streamline processes are taken into consideration same as prerequisites like operator skills.
TRIOPTICS GmbH (Germany)
Patrik Langehanenberg has obtained a doctorate degree for his work in the field of low coherence digital holographic microscopy from the University of Muenster, Germany in the year 2009. Since then, he is with TRIOPTICS GmbH where he leads the division for metrology and process technology for the optics manufacturing, in particularly focusing on activities in the field of centration testing and optomechanical characterization of optical systems.
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