SHORT WAVE PASS EDGE FILTERS
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.
- Useful for redirecting a particular band of light
- Offers coverage over the 300 - 1000nm range
- Provide steeper transition than color glass filters
- Fluorescence
- Photometry
- Color enhancement and combining
For more demanding requirements, please see our steep-edge long pass filters.
| General Specifications | |
| Thickness: | 4.0mm maximum |
| Size Tolerance: | +0.0mm/-0.5mm |
| Min. Clear Aperture: | 95% of outside dimension |
| Substrate Material: | Soda Lime Glass, Fused Silica (Note: BK-7, Borofloat available option for higher Tx.) |
| Flatness: | 3-5 waves per 25 TWF |
| Surface Quality: | 80-50 per MIL-C-48497A |
| Humidity and Abrasion: | Per MIL-C-675A |
| Operating Temperature: | -50°C to +100°C |
| Cut-on Slope: | 6% maximum (11% for 300nm filter) |
| Cut-on Tolerance: | ±10nm from 400nm-1100nm ±5nm from 300nm - 375nm |
| Mechanical: | Unmounted |
| Transmission | |
| Long Wave Pass: | 85% average from the 50% cut-on point to 2000nm |
| Short Wave Pass: |
400-450nm: 85% avererage from the 50% cut-on point to 0.75 x the 50% cut-off point 500-1000nm: 85% avererage from the 50% cut-on point to 0.75 x the 50% cut-off point Note: with the exception of the 400nm filter, all SWP filters will drop off in transmission at wavelengths under 400nm.) |
| Rejection | |
| Long Wave Pass: | 99% or greater from 0.9 x the 50% point to the UV |
| 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) |
