This paper starts with a description of the usability and the optical layout of an Abbe or Telescope type surgical microscope for stereo optical and stereo digital imaging. Most important optical characteristics for stereoscopic image aquisition are emphasized. Afocal Galilei-type optical zooms are the heart of all modern stereo microscopes for industrial, bioscience and surgical applications. Two type of such zooms are described:
Type 1: two separate optical channels, one for each stereoscopic view and.
Type 2: one common optical channel for both stereoscopic views each guided off-axis.
Type 1 zooms have the advantage of compact size and high optical quality. Their downside are tight tolerances and adjustment of optical members required for a good binocular performance. Type 2 zooms are always good at binocular even for standard tolerances but suffer from magnification dependency of the stereoscopic perception and from nonsymmetrical vignetting. Design examples are provided and some important aspects of aberration correction are discussed. As a vignetting-free system, one afocal commom optical channel Kepler-type zoom design example is proposed.
Finally, some advanced surgical microscope setups suitable for two stereoscopic observers in one microscope having different stereoscopic perspectives on the magnified object are shown. The Type 2 common optical channel zoom of Galilei or Kepler type is the best choice if a variable rotation position of a stereoscopic co-observer is required.
Afocal zoom lenses are state of the art modules for magnification changing in instrument optics, especially in the field of
scientific and surgical stereo microscopy. Carl Zeiss implemented many types of afocal zoom lenses in the microscopy
instrumentation in more than 30 years. Mechanically compensated zooms with two moving members for magnification
range between 4x and 20x are the most widely used zoom lenses so far.
As the instrumental optics gradually moves towards the digital imaging, some modified schemes have been created in
order to meet new requirements for extended zoom range and for accessibility to the system pupil by an aperture stop or
by a shutter. A structure and particular aberration analysis of a four member afocal 20x zoom lens is discussed.
It is pointed out that a modular approach for instrumental digital imaging systems with afocal interfaces around the zoom
module is one promising application of afocal zooms in the future. This approach contains an afocal zoom with an
accessible central stop surrounded by focusing lens groups placed on the object and / or at the image side of the zoom.
The advantages of schemes like that are the easy scaling to high magnification range, good balancing of aberrations and
diameters of lens elements and the high flexibility in adaption of video systems to different applications. Two examples
of modular video zoom lenses are given: an object-side telecentric 20x zoom lens with a four member afocal zoom and a
telephoto-type 30x zoom lens with a three member afocal zoom.
In the mid IR region, where water acts as the main chromophore in soft tissue, pulsed erbium lasers emit radiation with sufficient energy for photoablative tissue processing. In this study, the ablation characteristics of these lasers were analyzed in order to evaluate their potential for clinical application in corneal and intraocular surgery. Histopathological examination of thermal side-effects was performed on porcine corneas. Ablation rates were investigated by on-line depth profiling in free-running and in q-switched mode. Structure and intensity of laser induced acoustic transients were analyzed by piezo-electric PVDF-films.
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