Published July 15, 2026 at 17:58
Microscope illumination is fundamentally divided into two categories: REFLECTED LIGHT (episcopic — light shines DOWN onto the sample from above, reflecting back to the sensor) and TRANSMITTED LIGHT (light shines UP through the sample from below). The choice between the two determines whether a given sample can actually be visualized correctly.
Reflected light (standard microscope illumination)
Standard microscopes use ring LEDs around the objective. Light shines on the top of the sample and reflects back to the camera sensor.
Works excellently for:
- Metal surfaces (aluminum, steel, copper).
- Ceramics and glass in thick formats.
- Skin cultures and biological tissue blocks.
- Plastic parts with opaque color.
- PCB top surface with solder joints and components.
Works poorly or not at all for TRANSPARENT samples:
- Light is reflected ONLY from the surface — no internal structures are visible.
- Reflections from the upper glass surface can blind the sensor.
- Internal structural differences (cells, fibers, defects) become invisible.
Transmitted illumination
The LED-U is an LED-driven light panel placed UNDER the sample. Light shines UP through the sample, is absorbed or scattered by internal structures, and what passes through reaches the camera sensor from above.
Works excellently for:
Biological sections: Histology preparations on slides (typically 5-10 μm thick), oil microscopy of yeast and bacteria cell colonies, blood smears.
Thin plastic film: Packaging materials, thin electronic substrates, foil capacitor layers. Internal defects (bubbles, flaws, inclusions) are clearly visible.
Glass fibers and textile fibers: Individual fibers illuminated from below reveal cross-sectional shape and outer structure.
Etched glass or PCB pads: Metal patterns on a transparent substrate appear as sharp silhouettes against the illuminated background.
Microfluidic channels: Liquid flows through PDMS channels are visualized with contrast against the bright background.
Three-dimensional transparent samples: Insect wings, transparent larvae, plankton — internal structures are visible throughout the depth.
Diffuse vs. collimated light
Two fundamental variants of transmitted illumination:
Collimated (parallel) light: All light rays travel parallel to each other. Provides MAXIMUM CONTRAST for silhouette measurements (e.g., outer diameter of a transparent object). Covered in a previous article about the KITOZOOM PPL-B.
Diffuse light (LED-U): Light comes from all directions simultaneously. Provides MORE EVEN ILLUMINATION but less edge sharpness. Better for internal structure viewing where contrast is not critical.
The LED-U is the DIFFUSE variant — perfect for applications where internal structure visualization takes priority over precise silhouette measurements.
70 mm illumination area
The LED-U has a round illumination area with a diameter of 70 mm and an outer diameter of 95 mm. This size format is:
- Large enough for most microscope slides (standard 76 × 26 mm).
- Fits under 100 mm-format petri dishes.
- Compatible with most stereo microscope stands.
- Standard size for interchangeability with other Kitozoom accessories.
For larger samples (up to 200 mm diameter), larger variants are available, but with lower lumens per cm² due to greater diffusion.
Integration into Kitozoom systems
The LED-U is included as standard in the KITO 20, KITO 30, and KITO 40 video measuring microscope systems. When purchasing one of these systems, the bottom light panel does NOT need to be ordered separately.
The LED-U can also be ordered separately for:
- Replacement part if the original panel is damaged.
- Addition to older-generation Kitozoom systems without bottom lighting.
- Universal adaptation to other microscope stands (requires the stand to have room for a 70-95 mm diameter panel).
Applications
Cell biology and histology labs: Standard tool for visualizing cellular structures in thin sections.
Insect research and entomology: Insect wings, legs, and mouthparts visualized with diffuse transmitted light.
Textile QC: Individual fibers, weave structures, wear correlation.
Plastics industry: Quality control of thin films and foil structures.
Electronics QC: Transparent PCB substrates with metal patterns.
Fiber optics: Fiber cross-section inspection.
Pharmaceuticals: Tablet illumination to confirm internal density, tablet crack detection.
Forensics: Hair analysis, fiber transfer, glass fragment inspection.
Museum and art restoration: Manuscript paper transilluminated to reveal earlier writing or secondary layers.
Mineralogy: Thin rock sections for crystal structure analysis.
Specifications
- Model: KITOZOOM LED-U bottom light panel.
- Illumination area: round, Ø 70 mm.
- Outer diameter: Ø 95 mm.
- Light type: diffuse white LED.
- Power: 12V DC via included adapter.
- Integration: standard in KITO 20/30/40, accessory for other systems.
- Light control: on/off (some variants have a dimmer).
What you get for your money
KITOZOOM LED-U bottom light panel, round 70 mm illumination area with 95 mm outer diameter, diffuse white LED light for transmitted illumination, 12V DC adapter included, standard accessory for KITO 20/30/40 video measuring microscope systems but also works as a universal transmitted-light panel for other microscope stands. 1,755 SEK.
Standard accessory for cell biology, histology, entomology, textile QC, plastics industry, fiber optics, pharmaceuticals, and other applications where transparent or semi-transparent samples must be illuminated FROM BELOW. The extra cost over ”no transmitted light” is minimal, and for microscopy work with transparent samples, transmitted light is often ABSOLUTELY necessary — reflected light simply doesn’t provide information about internal structures.
