KERN OLM 171 Metallurgical Inversion Microscope, Reflected Light, Trinocular

Inverse geometry for solid materials

In industrial fractography, castings inspection and metallurgical quality assurance, conventional upright microscopes immediately reach their mechanical limits when examining solid workpieces. The fundamental technical advantage of the KERN OLM 171 is its inverse (reversed) design. The objectives and the focusing mechanism are physically located beneath the solid cross-table. This design architecture completely eliminates height restrictions for the sample material. Heavy engine components, solid steel slabs or thick semiconductor wafers can be placed directly on the table. Another decisive preparative advantage: with an inverted microscope, the workpiece need only be ground and polished to be absolutely flat on the underside to be examined. The time-consuming process of aligning the entire sample geometry to be plane-parallel – which is absolutely essential with upright systems – is completely eliminated.

Physical superiority of infinity optics

The metrological heart of the OLM 171 is its infinity-corrected optical system (Infinity Optics). The stream of photons reflected from the sample surface emerges from the objective as a parallel beam and is only focused into a real image by a specially calculated tube lens. This parallel beam path (infinity space) is fundamental to high-precision microscopy: it allows the stress- and aberration-free integration of additional optical modules, such as the polarisation and analyser unit included in the system, without shifting the optical focal length or inducing chromatic aberrations.

High-performance incident light and anisotropy analysis

Opaque (light-impermeable) metallic structures require a high coaxial photon density to resolve microscopic grain structures or crack edges (voids). The system is equipped with an extremely powerful 50-watt halogen epi-illumination system. To physically block the glare that inevitably occurs with reflective metal sections, the polariser is swivelled into the beam path, forcing the transverse light waves into a defined plane of vibration. Reflection off the crystal structure of the metal sample alters this state of polarisation. The analyser filters out diffuse specular reflections and makes optical stress-induced birefringence as well as heterogeneous alloy phases visible with maximum phase contrast.

Planachromatic LWD optics and metrological documentation

To image the flat polished surfaces typical of metallurgy without geometric distortion, the microscope is equipped with planachromatic LWD (Long Working Distance) objectives. These highly complex lens systems flatten the field of view, ensuring that both the centre and the peripheral areas of the solid workpiece are simultaneously in absolute focus. In addition to binocular visual inspection, the trinocular tube enables the simultaneous, loss-free coupling of the optical signal to a digital C-mount microscope camera. This is essential for the seamless measurement of grain sizes and software-based documentation in the field of quality management.

Technical details

• Optical system: Infinity-corrected (Infinity Optics)
• Microscope design: Inverted metallurgical microscope
• Illumination type: 50 W halogen epi-illumination, dimmable
• Tubus design: Trinocular, 30° inclination
• Objectives: Planachromatic LWD (Long Working Distance) optics
• Standard magnifications: 5x, 10x, 20x, 50x (plan objectives)
• Eyepieces: HWF 10x / Ø 22 mm (wide-field)
• Optical contrast: Includes polariser and analyser unit
• Mechanical stage: Fixed, with precise xy-travel mechanism for heavy specimens
• Camera output: C-mount adapter for digital image capture (trinocular tube)
• Power supply: Integrated mains power supply (230 V)

Scope of delivery

• 1 x KERN OLM 171 metallurgical inverted microscope
• 4 x Planachromatic LWD objectives (5x, 10x, 20x, 50x)
• 2 x HWF 10x wide-field eyepieces
• 1 x polarisation and analyser unit
• 1 x 50-watt halogen replacement bulb
• 1 x C-mount camera adapter
• 1 x dust cover and mains cable
• 1 x Detailed operating instructions

Individual requirements & accessories

The OLM 171’s trinocular optical path is designed for the direct attachment of a digital measuring camera (e.g. from the KERN ODC series). To carry out precise software-based length, area or angle measurements (metrology) on your metal structures, the camera, in conjunction with an object micrometre for system calibration, is essential. For specialised tribological investigations or analyses requiring extremely high magnification, we would be happy to advise you on additional LWD objectives (e.g. 100x). Please contact our procurement service at any time to configure your digital optoelectronic measuring station.