Kern OBN 135 Transmitted Light Microscope, Trinocular, 4x-100x, Köhler

A trinocular transmitted-light microscope with Köhler illumination is the instrument of choice for anything that goes beyond simply viewing a specimen, from blood smears in haematology to sediments in water analysis. The Kern OBN 135 transmitted-light microscope, with five Infinity-Plan objectives, covers a magnification range from 4x to 100x, whilst the Köhler illumination ensures an evenly illuminated image area across the entire field of view. The third eyepiece port makes the microscope ready for a camera, even though none is supplied with the basic model.

Five objectives, ranging from low magnification to oil immersion

The revolver houses five Infinity-Plan objectives: 4x/0.11, 10x/0.25, 20x/0.45, 40x/0.65 and 100x/1.25 in oil immersion. The three higher-magnification objectives are spring-loaded and spring back if accidentally placed on the slide, rather than damaging the lens or specimen. All five feature an anti-fungal coating, which is important in humid laboratory environments. Five objectives in five revolver positions mean there is no wasted space and every magnification level is immediately available.

Trinocular head and ergonomics

The Siedentopf tube is inclined at 30 degrees and can be rotated through 360 degrees. The dioptre adjustment operates on both sides from minus 5 to plus 5, whilst the interpupillary distance can be adjusted between 50 and 75 mm. The HWF-10x eyepieces, with a 20 mm field of view, also feature an anti-fungal coating and are designed as high-eye-point eyepieces. The tube diameter of the eyepieces is 23.2 mm, the standard DIN specification for this component.

Köhler illumination and Abbe condenser

The LED transmitted light illumination operates according to the Köhler principle and is infinitely variable, with a colour temperature of 6,000 Kelvin and a power output of 3 watts. The Abbe condenser is centring and height-adjustable, with an aperture of 1.25. In the manufacturer’s description, Kern refers to this combination as professional-grade equipment for demanding applications. Depending on the objective, the field of view ranges from 0.2 mm to 5 mm.

Cross-table and fine adjustment

The large mechanical cross-table features a coaxial coarse and fine adjustment mechanism that can be operated from either side. The fine adjustment mechanism operates with a minimum step of 0.002 mm; at 100x magnification in oil immersion, this is the difference between a sharp and an out-of-focus image.

Camera retrofit: C-mount required separately

The trinocular tube has a third port for a camera, but no sensor is fitted in the basic model. A C-mount adapter is required for the camera connection; this is not included in the Scope of delivery and must be ordered separately.

Standalone microscope or digital microscope kit: correctly classifying the OBN 135

Kern sells several versions under the model designation OBN 135. This product, listed as lt-22616 at LT Laborhandel, is the standard optical microscope without a camera. In addition, Kern offers digital microscope kits fitted with a camera as standard, such as the model OBN 135T241. At LT Laborhandel, this set is listed as a separate product: the Kern digital microscope set OBN 135T241, with the product number lt-22619. Those who wish to document digitally from the outset, without having to assemble a C-mount adapter and camera themselves, are better served by this set. Those who look exclusively through the eyepiece or wish to choose their own camera at a later date should opt for the OBN 135 described here.

Contrast techniques beyond the basic configuration

By default, the OBN 135 operates in brightfield mode. Darkfield, polarisation, fluorescence and phase contrast are available as additional contrast techniques, each requiring supplementary accessories. This is relevant for laboratories which, in addition to routine stained specimens, occasionally examine unstained or birefringent samples, for example in microbiology or materials science.

Typical applications

Kern cites a wide range of applications for the OBN 13 series, spanning laboratory medicine and industry:

• Haematology
• Urology
• Gynaecology
• Dermatology
• Pathology
• Microbiology and Parasitology
• Immunology
• Sewage treatment works
• Oncology
• Entomology
• Veterinary practices
• Water analysis
• Breweries
• Inpatient facilities
• Clinical laboratories
• Public health authorities
• Training centres
• Universities

At a public health authority, a technician uses it to test drinking water samples for bacteria; at a veterinary practice, a faecal smear is examined for parasite eggs. At universities and training centres, the same instrument serves as an introduction to microscopy, using the same optics that students will later use in their professional careers.

Frequently asked questions about the OBN 135

What is the difference between the OBN 135 and the OBN 135T241 set? The OBN 135 is purely optical, whilst the OBN 135T241 set (LT Laborhandel item no. lt-22619) comes with a factory-fitted camera.

Is a camera included in the Scope of delivery? No, the trinocular tube is prepared for a camera; a C-mount adapter must be ordered separately.

What is the maximum magnification? 100x with the oil immersion objective, numerical aperture 1.25.

Can I use phase contrast or polarisation? Yes, as optional contrast techniques via accessories; the basic model is preset to brightfield.

How finely can the focus be adjusted? The fine-adjustment knob operates with a minimum increment of 0.002 mm.

What is the eyepiece size of the microscope? 23.2 mm tube diameter, which is the standard DIN specification for microscope eyepieces.

How heavy is the instrument? The net weight is 10 kg, and the dimensions are 390 x 200 x 395 mm.

Technical details

Scope of delivery

• OBN 135 transmitted light microscope (trinocular)
• Dust cover
• Eyecups
• User manual (multilingual)
• Mains power supply

The scope of delivery does not include a C-mount adapter for the camera connection, and it must be ordered separately for digitisation.

Individual requirements and procurement service

LT Laborhandel’s procurement service provides support for the C-mount adapter, additional lenses, contrast techniques such as phase contrast or polarisation, and calibration following commissioning. Enquiries should be sent to lt-laborhandel.com/service.