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Updated: July 8th, 2008 05:26 PM CDT

Automated Calibration Method Developed for Optical Microscopes

Health & Medicine Week
via NewsEdge Corporation

2005 DEC 26 - ( -- An automated calibration method may facilitate the use of optical see-through head-mounted operating microscopes.

"Ever since the development of the first applications in image-guided therapy (IGT), the use of head-mounted displays (HMDs) was considered an important extension of existing IGT technologies," scientists in Austria explained. "Several approaches to utilizing HMDs and modified medical devices for augmented reality (AR) visualization were implemented," including "video-see through systems, semitransparent mirrors, modified endoscopes, and modified operating microscopes."

"Common to all these devices is the fact that a precise calibration between the display and 3-dimensional coordinates in the patient's frame of reference is compulsory," noted M. Figl and colleagues at the Medical University of Vienna. "In optical see-through devices based on complex optical systems such as operating microscopes or operating binoculars," this procedure "can become increasingly difficult since precise camera calibration for every focus and zoom position is required."

In a paper published in the journal IEEE Transactions on Medical Imaging, Figl and collaborators presented a "method for fully automatic calibration of the operating binocular VariosCope M5 AR [Life Optics, Vienna] for the full range of zoom and focus settings available."

This method "uses a special calibration pattern, a linear guide driven by a stepping motor, and special calibration software," according to the report. "The overlay error in the calibration plane was found to be 0.14-0.91 mm, which is less than 1% of the field of view."

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