A telecentric lens is the best solution to achieve high measurement accuracy and it is even more effective when matched with a collimated backlight. Collimated illumination offers many advantages, including a very high contrast image, and it is much more accurate than a standard backlight, because it drastically reduces the issues caused by «border effects».
Moreover, a telecentric lens and collimated light setup is highly efficient from an optical point of view: it allows the imaging system to operate at extremely short exposure times, which are essential for high speed measurement applications.
The machine features two identical optical systems:
each system comprises a TCCR2M048-C (Telecentric CORE lens for 1” detectors, magnification 0.268 x, C-mount), an LTCLCR048-G (Telecentric CORE illuminator, beam dimensions Ø = 56 mm; x = 50, green) and an area scan camera and is capable to perform very accurate measurements on a 47,4 mm x 37,9 mm Field of View with a resolution up to 18,522 microns per pixel. The Opto Engineering collimated solution allowed to achieve a uniform background, a nearly zero distortion image and an edge transition of 1 pixel.
Since the machine must measure bottles up to 200 mm, the aforementioned two identical optical systems are mounted on two motorized slides, so that by adjusting the positions it is possible to measure all types of bottle diameters: a similar setup allows to achieve both high accuracy, wide Field of View and very high flexibility.
A similar design is only possible thanks to the CORE lens’ compactness which allows the system to easily move on motorized slides. Using a traditional telecentric lens’ the size of the lens/light would create a large and very expensive system, while this innovative compact telecentric lens keeps the footprint small and the cost lower: This is only made possible by using the CORE lenses & lights.
During the build of the system, Torus measures the parallelism and squareness of the lights and lenses to each other and to the part holding, aiming for less than 50 micron geometric error. Even the very low residual distortion is then corrected by Torus software, to achieve a nearly zero distortion measurement system.