Bresser Science TRM-301 40-1000x Trinocular Microscope

The Science TRM-301 is a trinocular laboratory microscope with plan-achromatic objectives and halogen Köhler illumination, which Bresser lists for medicine, biology, agriculture and industry, and for the serious hobbyist who wants one microscope to keep. It covers 40x to 1000x through a 30-degree inclined binocular head with a photo tube on top.

Plan-achromatic objectives are flat-field lenses: the whole image is in focus at once, where a standard achromat is sharp in the middle and soft at the rim. That matters for counting cells across a field and for photographs. The set is PL 4x, PL 10x, PL 40x and PL 100x oil, the 100x retractable so it gives way if it meets the slide. The eyepieces are a pair of WF10x in 23 mm tubes, with eye relief and dioptre adjustment.

Köhler illumination sets the lamp, a field diaphragm and the condenser so the light across the specimen is even and free of glare, with the filament out of focus. Here it comes from a 12 V, 30 W halogen lamp with a continuous dimmer, a fixed field diaphragm and an adjustable Abbe condenser of numerical aperture 1.25 with an iris diaphragm. Bresser describes the result as bright, cool on the specimen and rich in contrast.

The mechanical stage moves lengthwise and across with a Vernier scale, and the coaxial focus knobs give 200 microns of travel per turn of the fine control, which is fine enough to step through a thick section. Immersion oil, a dust cover and a power cable are in the box; a C-mount camera for the photo tube takes the optional adapter, and our microscope camera guide explains the choice. The Science TFM-301 below it has semi-plan objectives and LED light, the aluminium body weighs 8.8 kg with its accessories, and it sits in our laboratory microscopes collection with the Infinity above it.