Thanks to the modular design of the instrument software, new options and software modules can be easily integrated in order to extend the measurement capabilities of the instrument.
The following extension modules are available:
- MultiLens® – For the alignment and assembly of complete objective lenses and the measurement of completely mounted optical assemblies
- AdvancedAnalyzer – Comprehensive analyzing tool in addition to MultiLens®
- AspheroCheck® – Measurement of centration errors of aspheric lenses
- Cylinder Check® – Measurement of centration errors of cylinder lenses
- Center Thickness – Determines the distance between optical surfaces inside of an optical system
- OptiSpheric® – for the measurement of EFL, BFL, FFL, radius of curvature and MTF on-axis
- OptiAngle® – powerful angle measurement tool
This complex software module is used either for the alignment and assembly of objective lenses or for measuring the centering errors of completely mounted optical assemblies. The inspection of mounted objective lenses provides precise data about the assembly quality. In this way, the MultiLens® software becomes an indispensable tool for optimizing the manufacturing process. The MultiLens® software delivers in a non destructive way the complete information about the individual centering errors of all surfaces in an assembly. The PC controlled OptiCentric® instrument performs stepwise a reflection mode centering measurement starting with the first surface closest to the measuring head and continuing with the following surfaces. The MultiLens® software performs a ray tracing through the optical system based on the lens design parameters and the measured centering values. Finally, the operator obtains a numerical and graphical output of the complete centering status regarding shift and tilt of each measured surface from the CentricAnalyzer submodule. The module can calculate the best-fit optical axis of the objective lens and all surface centering data can be referenced to this axis. Combining these features with adequate assembly techniques, high performance objective lenses with tolerances in the micron range can be easily centered to best performance.
The Advanced Analyser is a software tool in addition to the MultiLens®software with even more analysis features and comprehensive 3D graphical output. It is a self-contained software application. A separate copy can be ordered to per form a detailed centering analysis independently from the instrument’s PC. Of course, if it is run on the same PC, the measurement data is transferred automatically between the applications. The initial measurement data refer to the air bearing’s axis of rotation, which is usually not the desired result. The Advanced Analyser software therefore calculates the following situations:
- Calculate the optical axis passing through two or more centers of curvature. Weighting factors can be applied to calculate the regression line depending on the optical power of the surfaces.
- Calculate angle and distance between two optical axes (e.g. two single lenses)
- Calculate the surface tilt error of any surface relatively to the axis of reference.
- Reference all other surfaces and optical elements relatively to any user defined optical axis
- Reference relative to the mechanical axis
AspheroCheck® (Patent application 10 2006 052 047.5-51) is a hardware and software module designed to measure the tilt and shift of an aspherical axis with respect to a defined reference axis. The module is available as an upgrade for all OptiCentric® Systems equipped with a rotary air bearing sample stage.
The AspheroCheck® module consists of a high-resolution AspheroCheck® distance sensor mounted on a x-z linear stage system. The angle of the sensor can be adjusted square to the sample surface by a rotary stage. Every point along the radius of the sample can thus be reached by the sensor. The standard module is operated manually, a motorized version is available on request.
During the measurement, the AspheroCheck® sensor is moved close to the outer edge of the lens in order to capture the eccentricity of the surface during rotation. At the same time, the autocollimator determines the centering error of the surface in the paraxial area. Both values are then combined to determine the position and the tilt of the aspherical axis.
The following parameters of aspherical lenses can be measured:
- Shift and tilt of the asphere axis in relation to the reference axis of rotation.
- Shift and tilt of the asphere axis in relation to the optical axis of the lens. The “optical axis” is considered to be the line running through the centers of curvatures of the spherical portions.
- When a lens consists of two aspherical surfaces the angle and shift of both aspherical axes are determined.
CylinderCheck® is a software and hardware module for the precise measurement of centering errors of cylindrical surfaces. It requires a specific hardware to align the sample and perform the measurement procedures. Depending on the application, CylinderCheck® can capture various parameters of the cylindrical surface. Typical cylindrical lenses have one cylindrical surface and one plano surface.
For these samples, typically the orientation of the cylindrical axis in relation to the lens edge is measured. Additionally, it is possible to measure the angle between the cylindrical axis and the opposite plano surface. A dedicated sample holder (see picture) is required for both measurement types. CylinderCheck® also gives the azimuth angle of the cylinder axis relatively to a given edge. In addition, anamorphic lenses can be measured with this tool.
Besides measuring centering errors, the OptiCentric® system is able to determine the distance between optical surfaces inside of an optical system. An individual distance (e.g. the center thickness of a lens), but also a complete set of distances, including the center thickness of lenses and air gaps, can be measured non-destructively in an assembled objective lens. Same as in the MultiLens® measurement, this procedure requires the optical design data of the sample.
OptiCentric® offers two methods for this measurement. The first one uses the autocollimator with a lens attachment in order to determine the cat’s eye surface reflection position of the surface under test. The difference between two measured positions is used in conjunction with the design data (radii and refractive index) to calculate the actual distance. This method works extremely well with one or two distances but can be noticeably problematic with three or more.
TRIOPTICS therefore offers an alternative method using an additional distance sensor, specifically developed for measuring distances inside optical systems. It is based on white-light interferometry and is able to measure all center thicknesses in an objective lens with an accuracy of about 1µm.
A selection of different center thickness probes is available for the integration into the instrument. The standard white-light interferometer captures lens distances within a range of 0 to 200mm with an accuracy of 1µm. The high-end instrument measures lens distances with an accuracy of 0.15µm.
With the extension module OptiSpheric®, the measurement functionality of an OptiCentric® instrument can be extended by the following optical parameters:
- EFL – Effective Focal Length
- BFL – Back Focal Length
- FFL – Flange Focal Length
- Radius of Curvature
- MTF on-axis
Besides the software functions, the OptiSpheric® module consists of an additional collimator mounted with a 90° deflection mirror in the base of the instrument. It is equipped with a selection of test targets for the different measurement options.
The software module OptiAngle® and some additional mechanical fixtures convert the OptiCentric® instrument into a powerful tool for angle measurements, including:
- Wedges and filters
- Parallelism of parallel plates
- Deviation angle through wedges and prisms
- Mirror tilt
- Alignment of CD/DVD optical heads
- Wobble of rotating disks
More detailed information on the measurement of plano optics is included in the TRIOPTICS OptiAngle® brochure.