Sorry, this product is no longer offered for sale. It was discontinued on Jun 11, 2025The recommended replacement product is FSR-U340-C.

Optical Filter, Visible Absorbing, 25.4 mm Diameter, Hoya U-340 Glass

visible absorbing bandpass filter model fsr-u340

The FSR-U340 Visible Absorbing Filter is a 25.4 mm diameter dark glass optical filter that passes UV and absorbs visible wavelengths made of Hoya U-340 filter glass. These filters are precision polished for demanding research or OEM applications and are ideal for extraction of UV wavelengths.

Warning - this filter is extremely susceptible to high humidity. The filter will absorb moisture, and discoloration may happen. Please store this in a low humidity environment. We offer the , a coated version of this filter for humid environments. It prevents moisture from contaminating filter material, preventing stains, discoloration, and contamination. It also has 3% increase of transmission compared to uncoated version.

Specifications

Technical Specs

Type
Visible Absorbing Filter
Material
Hoya U340 or equivalent
Center Wavelength
340 nm
Angle of Incidence
0°
Size
Ø25.4 mm
Size Tolerance
±0.3 mm
Thickness
2.0 to 3.0 mm, typical
Surface Flatness
≤1λ at 632.8 nm over the clear aperture
Surface Quality
60-40 scratch-dig

Damage Threshold
30 W/cm² CW, Typical
Wedge
≤3 arc min
Clear Aperture
central ≥ 80% of diameter
Chamfers
Up to 1 mm face width
Chamfers Angle Tolerance
45° ±15°
Cleaning
See How to Clean Optics

Type
Visible Absorbing Filter
Material
Hoya U340 or equivalent
Center Wavelength
340 nm
Angle of Incidence
0°
Size
Ø25.4 mm
Size Tolerance
±0.3 mm
Thickness
2.0 to 3.0 mm, typical
Surface Flatness
≤1λ at 632.8 nm over the clear aperture
Surface Quality
60-40 scratch-dig

Damage Threshold
30 W/cm² CW, Typical
Wedge
≤3 arc min
Clear Aperture
central ≥ 80% of diameter
Chamfers
Up to 1 mm face width
Chamfers Angle Tolerance
45° ±15°
Cleaning
See How to Clean Optics

Resources & Downloads

2D Product Drawings

FBR-NDXX-S(62 kB, PDF)

Other

FSR-U340 RoHS Certificate(704.6 kB, PDF)

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