Meiji MT6800 PLM–PCM Combination Asbestos Microscopes

The Meiji MT6800 Series combines polarising light microscopy (PLM) and phase contrast microscopy (PCM) in a single instrument. These combination microscopes are configured for asbestos fibre identification and fibre counting applications.

Two configurations are available: the binocular MT6820 and the camera-ready trinocular MT6830.

MT6820 Binocular PLM–PCM Microscope

• Binocular polarising and phase contrast microscope
• MA936 Strain-Free Plan 10× objective
• MA936D Dispersion Staining 10× objective
• U Plan MA841 40× phase objective
• Phase and brightfield condenser
• HWF 12.5× focusing eyepiece with Walton-Beckett graticule
• HWF 12.5× eyepiece with cross-line graticule
• HWF 12.5× plain eyepiece
• 6 V, 30 W halogen illuminator

MT6830 Trinocular PLM–PCM Microscope

• Trinocular polarising and phase contrast microscope
• Phototube with 1× C-mount for camera attachment
• MA936 Strain-Free Plan 10× objective
• MA936D Dispersion Staining 10× objective
• U Plan MA841 40× phase objective
• Phase and brightfield condenser
• HWF 12.5× focusing eyepiece with Walton-Beckett graticule
• HWF 12.5× eyepiece with cross-line graticule
• HWF 12.5× plain eyepiece
• 6 V, 30 W halogen illuminator

Phase Contrast Dispersion Staining

The MT Series uses the phase contrast method for dispersion staining. The microscope includes a condenser with a centreable phase slider for use with annulus dispersion staining objectives.

For this technique, the analyser and compensator are withdrawn, the illumination intensity is increased, and the dispersion staining objective—with its phase ring positioned in the back focal plane—is used with the corresponding phase annulus in the condenser.

Different colours can be observed when a fibre is orientated parallel or perpendicular to the polariser’s vibration direction. The presence of two complementary colours within the same image can help the analyst determine the wavelength at which the fibre’s refractive index matches the mounting liquid.

Compared with the objective-stop method used by the older ML Series, the phase contrast method is designed to make the observed results easier to interpret.

Applications

The MT6800 Series supports:

• Asbestos fibre identification using polarised light microscopy
• Phase contrast dispersion staining
• Asbestos fibre counting using phase contrast microscopy
• Digital imaging with the trinocular MT6830 when fitted with a compatible camera

For further information on asbestos sampling and analysis procedures, refer to the Health and Safety Executive publication Asbestos: The Analysts’ Guide for Sampling, Analysis and Clearance Procedures.

MT Series PLM asbestos microscopes use the phase contrast method for dispersion staining and include a condenser with centerable phase slider for its annulus dispersion staining objectives. This technique requires that the analyser and compensator be withdrawn, the illumination increased, and the dispersion objective with phase ring in the back focal plane be inserted together with the corresponding phase annulus in the condenser. 
Different colours will be observed when the fibre is oriented parallel or perpendicular to the vibration / polarizer direction. This method is easier to interpret than the objective stop method used by the older ML Series due to the presence of two complementary colours in the same image, so that the wavelength of the refractive index match can be more closely determined.