TRIOPTICS - Flexible and precise aspheric lens measurement

06 Jan 2022

At Photonics West 2022 TRIOPTICS presents its leading centration measurement system OptiCentric^® 101 Dual with a new motorized tool stage equipped with a non-contact distance sensor for asphere testing. The motorized positioning not only guarantees superior accuracy compared to manual processes but leads to faster sample changeover and increased process safety.

Before mounting aspherical lenses to an objective lens, the intrinsic centration error between the asphere axis and the paraxial optical axis or the lens diameter needs to be tested and verified. Only then the mounting and alignment of the assembly based on the paraxial optical axis represents a valid approximation.

The OptiCentric^® AspheroCheck^® measures the asphere decentration by means of combination of an autocollimator with an optical distance sensor pointing to an off-axis zone of the aspherical surface. Under rotation, the beat of the sensor signal gives precise information about the centration. On OptiCentric^® 101, this setup is now available via a motorized positioner in addition to the established manual solution. The motorization allows the sensor head to move to its defined x-z measurement position with high absolute and repeatable accuracy. This increases the measuring precision. In addition, after initial setup the changeover between different lens types is completed much faster – in just a few seconds. Furthermore, the reduction in operator errors ensures an overall increase in process reliability.

The significant improvement in measurement accuracy was also achieved by the new mounting concept. This makes the measurement significantly more robust against external conditions such as vibration.

To further optimize process reliability, a motorized sample alignment table is available for automated alignment of the sample to the optical measuring axis as well as the automation of the theta axis that allows tilting the sensor towards the lens surface. With this, the sensor is brought to the correct incidence angle of the sample’s surface, so that the distance measurement is normal to the surface slope.

Compared to the AspheroCheck^® UP, which is dedicated for fast aspherical measurements, the AspheroCheck^® on OptiCentric^® 101 is the versatile testing tool that can be used for a variety of applications from testing of single elements to alignment and testing of lens systems. The system becomes particularly universal when the distance sensor is combined with OptiCentric^® 101 Dual: the version with two measuring heads, one above and one below the sample.

The highlight of OptiCentric^® 101 Dual is that both measurement heads can be used simultaneously for axial centration measurement. This reduces the measurement time for especially complex lens systems by up to half. Also, it simultaneously monitors the centration of a lens in 4 degrees of freedom – tilt and shift in each of the x and y directions.

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