BH-L20 Longpass Filter
Long-pass filter blocking blue (< 525 nm) while passing 92 – 94 % bright yellow-to-red light (560 – 780 nm) for colour-true, glare-free output.
- Passband: 560 – 780 nm, 92 – 94 % T (± 2 % ripple)
- Cut-on (T50): ≈ 545 nm
- Edge steepness: ~20 nm (10 → 90 % transition)
- Blue blocking: < 1 % T below 525 nm
- Construction: Ion-assisted hard-oxide; 5 – 450 mm shapes, 0.21 – 3.8 mm thick
- Custom options: Edge tuning, ripple smoothing, 45° AOI, rapid prototypes
Learn more
BH-L20 keeps transmission below one percent up to ~525 nm, crosses the
50 % mark near 545 nm, and clears 90 % by ~560 nm. It then rides a smooth
92 – 94 % plateau to at least 780 nm with ripple held within ±2 %. The
ion-assisted hard-oxide coating survives heat, humidity, solvents, and
repeated wipe-downs. KUPO can supply Borofloat®, soda-lime, Schott D263 T,
or Corning Eagle XG substrates in any outline—from 5 mm chips to 450 mm
plates, 0.21 – 3.8 mm thick—and ship prototypes in about two weeks.
Typical uses: LED colour tuning, GFP/YFP/RFP fluorescence
collection, blue-glare suppression in machine vision, daylight-to-tungsten
warming for film lighting, and AR/HUD graphics injection without blue
leak.
Description
BH-L20 keeps transmission below 1 % up to roughly 525 nm, rolls past the 50 % mark near 545 nm, and clears 90 % by about 560 nm. From there it holds a smooth 92 – 94 % plateau all the way to 780 nm with ripple held within ±2 %. Use it when you need to strip blue glare and preserve a bright, colour-neutral band from yellow through deep red.
Key advantages
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Steep blue cutoff – 50 % cut-on ≈ 545 nm; < 1 % T maintained to ~525 nm keeps violet/blue out of the signal path.
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High, flat passband – 92 – 94 % T from ~560 nm to 780 nm maintains luminance and accurate colour rendering.
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Hard-oxide durability – Ion-assisted coating survives heat, humidity, solvents, and repeated wipe-downs.
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Custom formats – Round, square, or free-form blanks from 5 mm to 450 mm, thickness 0.21 – 3.8 mm, on Borofloat®, soda-lime, Schott D263 T, or Corning Eagle XG glass.
Typical applications
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LED colour tuning – Remove cool spikes in white or RGB fixtures for warm, amber-rich ambience.
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Fluorescence emission – Collect GFP/YFP/RFP signals while blocking blue excitation lines.
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Machine vision – Suppress blue reflections on metal or glass while keeping red and green channels bright.
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Photography & cinema lighting – Warm daylight LED panels toward a tungsten look without gels.
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AR / HUD optics – Inject yellow-to-red graphics with zero blue leak to the viewer.
Need rapid prototypes or high-volume supply? BH-L20 filters can be coated, diced, and shipped to your exact specifications—fast.
