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Acton Optics & Coatings


Optical Filters


Acton optical filters are provided in a variety of VUV/UV filter types including bandpass, neutral density, and reflective designs. These filters are used worldwide for applications such as spectroscopy, elemental analysis, environmental monitoring, biotechnology instrumentation, and space exploration, as well as basic and applied research.

 Optical Filters Types Available:

Bandpass Filters

VUV/UV bandpass filters are available in various bandwidths for a multitude of laser and analytical applications. Our filters cover the wavelengths from 122 to 320 nm with bandwidths ranging from 10 nm to 100 nm. Most filters are available in 0.5, 1, and 2-inch diameters with custom sizes available on request. All filters are visually and optically checked before shipping and include individual transmittance traces to show specific performance characteristics. Detailed light-rejection measurements are available upon request.

Filters can be purchased open-faced, or covered and edge-sealed (for wavelengths above 170 nm) with optional mounting rings. Please note that mounting a filter reduces clear aperture.

Band Rejection Filters

Acton band-rejection filters are available for the bright 393.4 and 396.9-nm wavelengths of calcium. They are manufactured to allow plasma-emission spectroscopy in the 170 to 370-nm region, with reduced calcium spectral interference. Analysis of As 193.7 nm, Zn 213.9 nm, Cd 226.5 nm, etc. in direct-reading emission spectrometers is permitted by average filter transmittance level of 60 to 70% in the 200 to 350-nm region. Transmittance of 80 ±10% is maintained from 450 nm to the NIR. Useful transmittance down to 170 nm is obtained by the use of UV-grade fused silica substrates. Transmittance at 395 nm is 4.0% or less.

Magnesium band-rejection filters are available for the Mg lines at 279.6, 280.3, and 285.2 nm. Filters designed to reject other wavelengths are available upon request.

Long Pass Filters

Acton long-pass filters are designed to block specific short-wavelength ranges by reflection. These "cold mirrors" are ideal for gas detection systems, as well as other environmental or analytical monitoring systems that require differentiation of the shorter UV wavelengths from longer visible to NIR wavelengths. For example, a filter with 200 to 250-nm blocking has transmission of approximately 50% at the cut-on wavelength of 265 nm and 85% average transmission from the longer visible UV to NIR.

We can design long-pass filters for other UV cut-on wavelengths as well.

Neutral Density Filters

Acton neutral density filters are made of metallic films with varying optical densities. Each filter is individually calibrated for transmittance at a series of wavelengths and supplied with a transmittance curve. VUV and UV ND4, ND5 and ND6 filters are supplied in anodized metal rings. Other neutral density filters are provided open-faced, with mounting rings available on request.

Reflective Filters

Acton multi-layer reflective filters are all dielectric, narrow-band reflectors that offer high reflectance at specific VUV through UV wavelengths while transmitting longer wavelength UV to IR light.

Solar Blind Filters

Originally designed for the space program, these unique "very broadband" UV and VUV filters are useful for isolating broad bands of UV or UV-VUV radiation, while rejecting visible light. Acton Research very broadband filters offer broadband transmittance properties, averaging 10-20% over the bands specified. Rejection is approximately 5x10-3 at 500nm.

Model 120-VBB: Care must be taken to avoid contact with the coated surface of this open-faced design, as absorption of the substrate at wavelengths near 120nm typically prohibits covering and edge sealing.

Model 170-VBB: Is manufactured open-faced, however it can be supplied covered and edge sealed to protect the coated surface.

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View the Filter Coating Curves