Measuring optical lenses

Schneider-Kreuznach relies on MATRIX VISION’s USB 2.0 cameras for measuring optical lenses

Due to mechanical manufacturing steps like beveling, polishing, centering and coating, the fabrication of optical lenses is complex and often leads to so-called centering errors. However, a centering error does not mean that the lenses are rejects. A precise knowledge of the deviation is important. For this purpose, Schneider-Kreuznach GmbH offers the centering tester VP 30508, a premium measurement system, which relies on the board-level version of the mvBlueFOX USB 2.0 camera.

To keep the basic design of the device Schneider-Kreuznach needed a small, flexible solution with high image quality and found the board-level model of the mvBlueFOX camera. With a length and width of only 38.8 mm and a maximum height of 34 mm, the module fitted the given profile. Not only does this camera have an additional image memory of 8 Mbyte for buffered image transfer, the quality of its very low-noise images was also impressive.

The instrument and camera form a perfect team which, with a precision of 0.01 angular minutes, meets the highest demands. Centering errors are measured according to ISO 10110 without the need to know any lens data (radius, focal length, etc.) as others methods do. In combination with aperture 3 as an effective spatial filter, the alignment of projector and receiver with an angle of ±20° makes it possible to get a high separation effect during probing of the optical surface. It is also possible to measure lenses with a center thickness of 0.4 mm without any problems. Given that the tester is equipped with two measuring heads, two mvBlueFOX-M modules are used. Therefore, lenses with two lens surfaces can be measured on both sides without the need to turn the lens over.