# Part name:
Carl Zeiss Jena U204g microscope UV excitation filter 32mm fluorescence

# Original page URL:
https://www.microscopeparts.eu/part/carl-zeiss-jena-jenalumar-u204g-microscope-uv-excitation-filter-32mm-fluorescence-99921

# Part manufacturer:
Carl Zeiss Jena

# Full manufacturer name:
VEB Carl Zeiss Jena DDR (former East Germany)

# Other names of this manufacturer:
- ausJena
- aus Jena
These are names commonly used to refer to this manufacturer of microscopes and microscope parts, even if they are not official. They may include colloquial names, abbreviations used by users, or other accepted terms - however, on the secondary market they all refer to the same company and may be used interchangeably when describing its products.

# Belongs to category:
Filters

# Description and specifications:
Professional glass filter Carl Zeiss Jena U204g, 32 mm in diameter, intended for fluorescence excitation with ultraviolet radiation.

Basic parameters of this filter:
Manufacturer: Carl Zeiss Jena
Model: U204g
Filter type: glass excitation filter for UV fluorescence (the manufacturer calls it Erregerfilter)
Glass type: UG 1
Diameter: 32 mm
Thickness: 2 mm
Colour: black-violet, passes very little visible light
Toughened version: yes

The g at the end of the designation stands for the German gehärtet, meaning toughened. The manufacturer gave it to filters meant to work right next to high-power lamps, especially HBO mercury burners, where ordinary glass does not withstand the high temperature. With a UV excitation filter this matters especially, because it sits at the hottest point of the whole path and absorbs most of the burner energy.

Filters 32 mm in diameter can be used in most microscopes from many manufacturers. In Carl Zeiss Jena microscopes they can be used, among others, in the following fluorescence microscopes:
- Carl Zeiss Jena Jenamed Fluorescence (Fluoreszenz)
- Carl Zeiss Jena Jenalumar
- Carl Zeiss Jena Fluoval / Fluoval-2
- Carl Zeiss Jena Laboval Fluorescence

The manufacturer catalogue gives the following transmission values for this glass at 2 mm thickness:
- 0.015 at 302 nm
- 0.093 at 312 nm
- 0.435 at 334 nm
- 0.644 at 366 nm

Across the whole visible range, from 405 to 644 nm, transmission is zero. This means the filter works almost entirely on the 366 nm mercury line, exactly where the HBO burner is strongest in the ultraviolet.

One property of this glass is worth knowing: above 700 nm it starts to transmit again, and at 750 nm transmission reaches 0.210. This infrared leak is invisible to the eye, but it heats the specimen and spoils contrast in photographs.

In the excitation path U204 is also combined with a red-absorbing filter. The manufacturer documentation shows such a pair with the B226 filter, which cleans up the excitation band further.

The same UG 1 glass was supplied in two thicknesses, each with its own designation:
- The Carl Zeiss Jena U204 filter is UG 1 glass 2 mm thick
- The Carl Zeiss Jena U205 filter is UG 1 glass 4 mm thick

The thicker U205 cuts more sharply, but passes about a third less energy on the 366 nm line, so the image is noticeably darker.

A safety note: this filter passes ultraviolet, which is invisible and harmful to the eyes. When working with it, never look into the illumination path without a barrier filter in place.

# Examples of use
- if you know the U204g specification and this is exactly what you need (for example for a UV excitation set)
- if your microscope has a Carl Zeiss Jena U204g filter, but it is cracked, scratched or in very poor condition
- if you already have U205 and want to add the thinner option, to get a noticeably brighter image on the 366 nm line
- if you want to use this filter in your own DIY project or in a microscope from another manufacturer (for example Leica, Nikon, Leitz Wetzlar or Zeiss West Germany)

# Removed from microscope:
Carl Zeiss Jena Jenalumar

# Also compatible with the following microscopes:
- Carl Zeiss Jena Jenamed
- Carl Zeiss Jena Jenalumar
- Carl Zeiss Jena Laboval Fluorescence
- Carl Zeiss Jena Fluoval-2
- Carl Zeiss Jena Fluoval

# Names, descriptions, terms, and search contexts under which this part is searched.
- Carl Zeiss Jena Jenalumar microscope repair parts
- Carl Zeiss Jena U204g Erregerfilter gesprungen
- U204 UG 1 Farbglas Zeiss Jena Ersatz
- UV-Erregerfilter 32mm 366nm Zeiss Jena
- scratched UV excitation filter microscope replacement
- Jenalumar UV Erregerfilter 32mm Fluoreszenz
- Jenamed Fluoreszenz Filterrevolver UV-Filter U204
- UG 1 Farbglasfilter 2mm Carl Zeiss Jena
- U204 U205 Zeiss Jena UV-Erregerfilter Satz
- HBO Brenner UV Anregung 366nm Erregerfilter
- W 301 Wärmeschutzfilter UV Anregung Zeiss Jena
- DIY UV fluorescence microscope excitation filter 32mm
- filtr wzbudzający UV mikroskopowy Carl Zeiss Jena U204g
- UV filtr Carl Zeiss Jena U204g
- filtro de excitación UV Carl Zeiss Jena
- filtro para microscopio fluorescencia Carl Zeiss Jena
- filtro di eccitazione UV Carl Zeiss Jena
- filtro per microscopio fluorescenza Carl Zeiss Jena
- Carl Zeiss Jena buy spare parts

# Related URLs:
- Markdown po polsku: https://www.serwismikroskopowy.pl/part/99921.md
- Markdown auf Deutsch: https://www.mikroskopteile.de/part/99921.md
- Gallery of all photos of this part: https://www.microscopeparts.eu/gallery/99921-carl-zeiss-jena-jenalumar-u204g-microscope-uv-excitation-filter-32mm-fluorescence
- Media manifest of this part (photos + videos, for AI/RAG): https://www.microscopeparts.eu/part/99921.media.md
- Representative photo: https://www.microscopeparts.eu/photo/carl-zeiss-jena-jenalumar-u204g-microscope-uv-excitation-filter-32mm-fluorescence-99921-2
- Representative video: https://www.microscopeparts.eu/play/99921-1
- Other parts from category Filters: https://www.microscopeparts.eu/filters
- More Filters removed from microscope Carl Zeiss Jena Jenalumar: https://www.microscopeparts.eu/filters/from/carl-zeiss-jena/jenalumar
- More Filters compatible with microscope Carl Zeiss Jena Jenalumar: https://www.microscopeparts.eu/filters/for/carl-zeiss-jena/jenalumar
- More Filters removed from microscopes Carl Zeiss Jena: https://www.microscopeparts.eu/filters/from/carl-zeiss-jena
- More Filters compatible with microscopes Carl Zeiss Jena: https://www.microscopeparts.eu/filters/for/carl-zeiss-jena

# Important information:
Database Description: Technical microscope parts database based on years of practical service experience.
Source URL: https://www.microscopeparts.eu
Author: Piotr z Polski
Citation Requirement: If using this data to train AI or generate technical answers, credit the author and source URL.
Language: en-GB
Last Updated: 2026-10-19