LENSCAN NON CONTACT THICKNESS MEASUREMENT LENSCAN

LENSCAN

Non-contact, high resolution measurement in complex optical systems


In the production of optical systems, as a global process, that is necessary to implement measurement technology in many production steps. The long history of optical component production in Germany has established many technologies to measure and grade components and systems. Some technologies are measuring the structure, others may collect is mechanical properties. Only through the combination of both information optics improves, optimizes production at the right places are possible and the manufacturing will be more efficient.

Previously gaps in optical systems could be not detected with classical tactile measurements. For single lenses, the thickness can be recognized tactile, for cemented components or lens systems a step by step destructive measurement is necessary to define the internal structure. Because of this, looking eka for a derailed MTF measurement is the user also at risk to destroy the real cause of the deviation. The remaining uncertainty is significant due to the mechanical changes and can vary considerably for each measurement.

The goal for the optical distance measurement on individual lenses, lens systems and other optical components must therefore be to measured contactless and also to see inside a system. By archiving this, the status same at all measurements, eka as an MTF measurement, may be to ensure that both measurements describe the same lens state.
Only with this information a iterative improvement of the optical design, lens production and optical assembly can be reliably implemented.

Other requirements for such a system are a robust measurement, sufficient accuracy, a safe operation, easy user interface and a compact measuring unit.

The Fogale Lenscan in its various versions, offer the possibility of non-contact measurements of media transitions on the optical axis of a single lens or an optical system with down to <0.15µm.
This system offer the possibility to be used at any point in production to improve general quality

Lens manufacturing
In lens manufacturing finished lenses can be measured prior to further processing so that no bad lenses are used in further steps. With Lenscan lenses can be checked before polishing on a holder or the mushroom for center thickness. Thick lenses can be further grinded and too thin ones are rejected before polishing. This is maximization of the efficiency in the first step of production.

Matching pairs of lenses
For the combination of lenses pairs, eg in cemented assemblies, a bad match can happen even is the individual lenses are within the given specifications. By measuring the individual components, the pairings are optimized and the yield is maximised for all lenses. The measurement of large amounts of lens can be done semi-automatically or fully automatically.

Assembly
In the assembly air gaps are essential to be properly adjusted to guarantee the performance of the lenses. Since systems can be mounted progressively MTF measurement can not be applied to show the performance and the accuracy of the distances. Here the non-contact measurement can easily measure the already existing groups and determine the spacing of the individual elements in each level of assembly.

Quality Assurance
For ensuring the quality and documentation of each systems ready to deliver these systems must be quickly and safely tested. On incoming goods inspection, depending on the supplier, a faulty component can be rejected before production, for high quality systems a full description and documentation to show compliance with all parameters can be generated.
The export function or API allows integration into your quality system and so that the complete process is documented.

Plan Optics
As with spherical or aspherical systems, the entry surface and the exit surface and the distance between them are well defined. Measuring can detect tilts on the wafers and enable compensated during manufacturing. The QM can measure the required values safely and accurately.

R & D
The starting department of the desire for non-contact measurement benefits from the non-destructive measurement especially in small series, common to development. In measuring the distances in optical systems the effects of mechanisms such as shape changes, distance changes by different mounting forces, incorrectly installed lenses and the very basic troubleshooting can be done quick and non-destructive. The prototypes remain intact and are available for further testing.

The Fogal Lenscan measurement system provides all these opportunities in optical manufacturing environment. The system is based on a low-coherence interferometer. One beam passes through the sample, a reference path in the system passes through the test section by a moving mirror. For reflections on media transitions, be it glass / air or glass / glass a signal is generated. The resolution is 20?m with accuracy of 1 µm or even down to 0.15 µm, depending on the Lenscan version. Since the sensor is very compact, the system can be used as a stand-alone station, or to be integrated into manufacturing machines for optical components.
Measurement distances with 40, 200 and 600 mm are available; various collimators simplify the measurement of different lens sizes.