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 Edge Filters (Long Wave/Short Wave)
Visible Long Wave Pass NIR Long Wave Pass
Visible Short Wave Pass NIR Short Wave Pass


Photo of Edge Filters (14650 bytes) Often referred to as long wave pass (LWP) and short wave pass (SWP) filters, these sharp-cut edge filters are distinguished by their high rate of transition between their region of reflection and transmission. This high rate of transition makes them an excellent choice as emission filters in fluorescence applications, and as order sorting filters in photometry. They are also very useful as stray light or trim filters, to eliminate any unwanted near band radiation. All Andover LWP/SWP filters are constructed of hard, durable first-surface dielectric coatings, and will withstand the normal cleaning and handling associated with any high-quality optical component. Their film construction is essentially a modified quarter-wave stack, using interference effects rather than absorption to isolate their spectral bands. Unlike filter glass, which is not sensitive to wavelength shift with angle, these filters will shift shorter in wavelength with an increase in their angle of incidence. This feature can be useful in applications where it may be desirable to fine tune the 50% cut-on, or cut-off wavelength. All standard edge filters are available in 50nm increments from 400nm to 1000nm. Custom edge filters are available and will be quoted upon request. Please contact one of our technical sales representatives for more specific information.



General Specifications
Size Tolerance: +0.0mm/-0.5mm
Thickness: 4.0mm max.
Minimum Clear Aperture: 95% of O.D.
Substrate Material: Glass
Flatness: 3 to 5 wave per 25mm
Parallelism: 3 Arc minutes or better
Surface Quality: 80/50 Per MIL-O-13830B
Coating Quality: 40/20 Per MIL-O-13830B
Humidity and Abrasion: Per MIL-C-675A
Operating Temperature: -50°C to +100°C
Cut-on and cut-off slopes: 6% Maximum
Cut-on and cut-off tolerance: ±10nm
Mechanical: Not mounted in metal holders
Transmission:
Long Wave Pass: 85% average from the 50% cut-on point to 2000nm
Short Wave Pass: 85% average from the 50% cut-off point to 0.6 x the 5% cut-off-point *With the exception of the 400nm filter, all others will drop off in transmission at wavelengths less than 425nm.
Rejection:
Long Wave Pass: 99% or greater from 0.9 x the 50% point to the ultraviolet
Short Wave Pass: 99% or greater from 1.07 x the 50% point to 1.25 x the 50% point
Effective Index of Refraction (n*) 1.7 (approximately)

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