Any machine vision lens (either telecentric or not) shows some amount of distortion. In addition to barrel or pincushion distortion, changes in the angle of view or misaligned components will affect the image symmetry and generate the so-called thin prism or keystone effect.
Imaging and metrology applications often require to minimize distortion. This correction can be done by software by analyzing the image of a precision pattern whose geometrical features are precisely known.
For this reason, Opto Engineering® offers a full range of patterns optimized for software calibration compatible with most Opto Engineering® telecentric lenses.
The checkerboards are realized with two different processes in order to provide the best solution depending on the requirements:
- Chrome on glass, for leading edge applications;
- Emulsion on glass, for a perfect synthesis of performance and cost effectiveness.
Moreover, a certified version is available: standards and equipment used for calibration have been calibrated traceable to the National Institute of Standards and Technology (N.I.S.T.), in accordance with procedures set forth in ISO/IEC 17025-2005 and ANSI/NCSL Z540-1-1994.
- Class number (2*) for Emulsion-on-glass photomasks differs from usual Chrome-on-glass. Specifications are in the tech info section.
- Download CoC Format Pattern facsimile
It’s possible to calculate dimensional tolerance of pattern’s features is calculated as follows:
Example of dimensional tolerance for grade 2 pattern over 10mm length:
Dimensional Tolerance = ± 0.0016mm + (±0.000008mm x 10 mm) = ± 0.00168 mm
|For Chrome-on-glass Photomask|
|Class||Min feature dimensions; Min spacing(µm)||Positioning error (µm)||Speed factor (µm/mm)|
|For Film-on-glass Photomask|
|Grade||Min feature dimensions; Min spacing(µm)||Positioning error (µm)||Speed factor (µm/mm)|